| Author | Message | ||
| Jim Stewart (H3jim)
Rating: |
All the diagrams I have seen that show how a battery equalizer is wired, shows three wires going to it from the batteries. For example, on a 24 volt system, there is a ground, two 12 volt batteries wired in series to make 24 volts and one of these leads goes to the 24 volt terminal on the equalizer, and lastly the center tap of the equalizer goes to the "middle" of the battery set, so it has access to 12 volts. The person I bought my equalizer from, who is an experienced and respected bus nut, says that as long as the ampacity of the equalizer is not exceeded, that the 12 volt tap back to the battery set is not required. It is only needed if the ampacity you require is larger than the capacity of the equalizer. For normal, read smaller current draws, all the equalizer really needs is a 24 volt source and a ground, and all the 12 volt power can just be pulled from the center tap of the equalizer. Sure would make the wiring easier if this is true. I guess the equalizer might help with any battery imbalances, but is not required by the equalizer to power the 12 volts. Can any of you wiring gurus comment on this? | ||
| John that newguy Rating: N/A |
Jim- Get the info from the horse's mouth: http://www.vanner.com/pdf/man-0001.pdf http://www.vanner.com/htm/pro_01.htm?series_sku=3195361503151112&a=a&pt=3 | ||
| Jim Ashworth (Jimnh)
Rating: N/A |
The equalizer balances the draw on each half of the battery bank. Without the 12v center tap, the equalizer won't equalize. Without the equalizer, all 12v will come from the 0 to 12v battery and nothing from the 12 to 24v battery. This will result in an undercharged battery and an overcharged battery while running. Put the 3 wires and if your expected load is the capacity of the equalizer (usually only up to 50A) then a #8 wire is sufficient. Equalizers can be paralled for greater amperage. This is the brief answer. Jim | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
snip "who is an experienced and respected bus nut," I would suggest that you re-evaluate your opinion of this nut. Richard | ||
| Jim Stewart (H3jim)
Rating: N/A |
Interesting. Sacrilegious even. After reading the Vanner site, and looking at their diagrams, it would appear that you can indeed provide the equalizer 24v and ground, and use the 12v for your loads. It will not draw down one or the other 12 volt batteries since the equalizer is only pulling 24 volts, from both batteries, just like all your other 24 volt loads do. Having said that, that wiring scheme does not offer one of the Vanner stated benefits of having an equalizer in the first place, and that is to keep the charges balanced between the batteries, even with no 12 volt loads at all. When connecting batteries in series, there are slight differneces in the batteries, the cabling etc, and this can lead to "normal" minor imbalances that the equalizer corrects. This has nothing to do with pulling 12 volt loads from the battery bank. If you were to center tap the batteries and pull 12 volt loads this way, that does cause large battery imbalances that shortens battery life. On page 8 of the 16 page Vanner installation guide (the first of JTNG's two Vanner links), shows a diagram where the batteries are hooked this way. I just called Wrico again, and they confirmed that from their experience, that this is the way to do it. With no center taps, that they get the best battery life. If the batteries are wired together correctly, that any imbalances are minor, and equalizing is not required. They reiterated that I should wire the Vanner to the 24 volt house bank, and draw all my 12 volt loads (and I don't have very many) from the equalizer. No battery center tap. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
In again reviewing the Vanner diagram, it appears that the omittance of a battery center tap is when there is both a 24 volt starting battery bank and a 12 volt house battery bank. In my opinion the equalizer is not acting like an equalizer in this case. It is only acting as a 12 volt battery charger. The original query was about taking 12 volts from the center tap of two 12 volt batteries connected in series providing 24 volts. In every other diagram in the Vanner document where this is the the situation, the center tap of the Vanner goes to the center tap of the batteries. Have I missed something or just do not understand what Jim was asking? Richard | ||
| Jim Stewart (H3jim)
Rating: N/A |
My original question was to verify what Dick Wright was telling me, as it seemed to be different than anything I had heard or seen before. I am in the process of wiring this and locating the equalizer, so I wanted to make sure that I won't have to redo it all. I seemed to have answered most of my own question, ala the following. Wrico has confirmed their position. I just got off the phone with Technical support at Sure Power Industries, the maker of the actual 80 amp model I bought from Dick. Their take is that it can be used that way, but I am missing the benefits of equalizing the batteries. Also, since the output is an unregulated 12 volts, if the input is more or less than 24 volts, the output will vary proportionately as it is designed to output exactly half of the input voltage. I have very few requirements for 12 volts in my coach - toilet, electric dump valves, control panel for air conditioning (not the compressor, thats 120v) and any spare 12 volt outlets (cigarate lighter type) I may care to add for convenience. All would use power for very brief amounts of time, or use very low amounts of current. And none of it is terribly voltage sensitive. The equalizer in this case would be used soley as a 12 volt power source, and not an equalizer. | ||
| Brian (Bigbusguy)
Rating: N/A |
I dont see why 1 extra wire would be so hard to add to have it equalize the batts? I does look like it will power your 12 items hooked up ether way but you will not have a added surge above the rated power of your equalizer if not hooked up the the center tap. Brian 4905 Oregon | ||
| don (Bottomacher)
Rating: N/A |
Jim (H3)- do you have 12 volt headlights? | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
H3Jim, Do you have a 24 volt battery bank and a 12 volt bank? Why I ask is that I do not believe you should hook the raw 12 volts out of the Vanner directly to your 12 volt loads. A battery would act as a filter and also stabilize the 12 volt output. I think you indicated that you had a very small 12 volt load but you have an 80 amp equalizer. Why so big? Just curious. Richard | ||
| Jim Stewart (H3jim)
Rating: N/A |
One wire would not be that difficult to add - its the distance and the size of the wire to support full 80 amp output at 12 volts with minimal voltage drop. The bus does have 12 volt headlights, and it has its own separate equalizer. I'm just setting up the house system. DML - At the time I bought it, I was buying all kinds of other stuff, and had not yet figured out what voltages I was going to use for various applications. For example, the water pump I bought can be used with 24 volts, so thats what I'm using, but initially I though it would be 12 volts. I knew I needed an equalizer, and figured it was better to have it - be easier to plan locations, etc. having something in hand. I just bought what Dick recommended (something about a fool and his $). But in general, I am happy with all I bought from him. As it is I have spent countless hours researching and tracking down things, far more than any time I have actually spent actually working or fabricating. So getting a few things out of the way, even if later as I know more, I would do it a little differently, its probably worth it. Also having a bunch of parts in hand makes the jigsaw puzzle of fitting everything in tight spaces easier in a way. For a newby it helps visulalization. Now halfway through, I would do some things another way, but I bet all of us would - that seems to part of this bus building process. I do not have separate banks, just the standard series parallel 12 volt setup. Not to beat this thing to death, but the current plan was to locate the equalizer inside the bus, next to the the 12 and 24 volt fuses. That way, one #6 wire could handle 50 amps at 24 volts, then after losses, the equalizer could then provide close to its full output at 12 volts if necessary. If I ever want to equalize the batteries, I need to have it physically located closer to the batteries unless I run a mongo wire back to them. The Sure Power tech indiated that its ok to wire it this way, its just that I do not get the benefit of equalized batteries, and the 12 volts is only nominal, it will be 1/2 of the input voltage. And of course if I ever needed more than the 80 amp output, it would overload the equalizer. A battery center tap would allow the batteries to supply the shortfall. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
OK, thanks. I, and everyone else will understand better. The good thing is that all of us learn something about something every time one of these discussions take place. One more question, since you already have an equalizer for the headlights, then I assume that the center tap of the combined coach/house battery is connected to the 12 volt tap of the existing equalizer. Is that correct? Richard | ||
| Jim Stewart (H3jim)
Rating: N/A |
Preovst did wire it that way, yes. as has every other application I have seen, except Wrico's. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
Things are getting clearer. I do not think it would be a good idea to hook two 12 volt equalizer taps to the same battery bank. I am assuming this is why Dick Wright did not recommend it also. Don't know what would happen but it does not seem to be a good idea to me. However, I would consider putting a small 12 battery on the new equalizer 12 volt tap to stabilize the voltage and act as a filter to filter the output of the equalizer and prevent any noise or hash from getting to any critical 12 volt device connected to it. Richard | ||
| Jim Stewart (H3jim)
Rating: N/A |
I will have two completely separate battery banks, one for the bus which is exisiting and has an exisiting equalizer, and a new one I am adding for the house. The only connection (and its not really a connection) between the two will be a battery isolater so the bus alt can charge both banks while I'm driving. The two 24v battery systems are not combined, but totally independant. | ||
| John that newguy Rating: N/A |
Another thought? If you already have a 24v inverter, and 110v is provided through it to all areas of your bus, why not just use a 110v to 12v converter wherever one is needed? You could forget about having any 12v battery bank and all it's associated problems. 110vac to 12vdc converters are available through ham radio supply houses for very reasonable cash. Small, used computer power supplies are a dime a dozen and can sever many needs well. Power pole, genset, alternator, or 24v battery bank, the 12v would always be available. Seems simple to me.. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
OK, one more question for the curious. Why two 24 volt battery systems. Why not the house system only 12 volts. Must be something in the house that needs 24 volts, but I can not figgure out what it would be. Richard | ||
| Jim Stewart (H3jim)
Rating: N/A |
Boy, ask a bus nut a question on his rig and you are liable to get more of an answer than you bargained for. Some reasons for going 24 volt on my house system. The bus system is 24 volts, so I can jump from one to the other. The bus alternator can be used to charge the house system too. The 24 volt inverter is a much more efficient inverter, and I am all electric. Even so I am still using 4-0 cable from the batteries to the inverter. Any accessories I chose, such as the refrigerator, the water pump, any lights are all more efficient than 12 volt, and I can use smaller wire for the same amount of watts / power. So yes, the refrigerator is 24 volt DC. Even the 10 gauge wire would not have been large enough for decent run length for a 12 volt refrigerator - its not the amps, its the voltage drop. The water pump runs on either, so I use it in the 24 voolt mode, I scavenged some of the 24 volt interior bus lights that I will use. My Espar, hydronic heater is 24 volts, and I will switch that from the bus system to run off the house system. The fans for my hydronic heaters are all 24 volt. The existing bay lights are all 24 volt, there are two in each bay, one by each door, that switch on when you open the door, so I will also switch those to the house system. Same for the stairwell lights. I will keep the bus system totally separate, the idea is to make those batteries last as long as I can by not discharging them except to start and run the bus. Because I have a 4000 watt inverter, and do not need it for the refrigerator, I will go with mostly all 110 volt everywhere else. Advantium microwave / convection oven, other lights, tv's, stereo, block heater, stovetop, awning power, alternate power for the hot water heater, outlets, 3 roof air conditioners, and possibly electric heat in the bathroom floor. I also have a totally separate 12v battery for the generator start. Now all I need is some jumper cables for those emergencies. Excessive voltage drop in DC circuits is hard on the appliances, slows DC motors, makes them less efficient and creates heat, sometimes to dangerous levels. You experience excessive voltage drop in a DC circuilt usually long before you reach the rated ampacity of the wire. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
Great information Jim. I am sure it will be a lot of help to others pondering the 12 or 24 volt question. You certainly convinced me that in your cass this is the way to go. Richard BTW, I am still not convinced that Dick Wright is correct in not connecting the equalizer like the manufacturer directs, but that is life. | ||
| Jim Stewart (H3jim)
Rating: N/A |
Richard, I'm still not sure that Dick is right (Wright) either, but after all this discusion, I am going to mount the equalizer closer to the batteries, so if I decide I want to change later, I won't have the wire length /size issue. Any equalizing loads are bound to be far larger than the small amounts of 12v I will use. So its better to put it closer to the larger load. Costs me nothing to do it now. Theoretically, I am sure that connecting the 12 volt center tap makes good sense. However, Dick is making that recommendation based on his experience. As we all know, he has been around for quite a while, and has seen / worked on / trouble shot a large number of coaches. So practically speaking, he may be right. In my case, because of my low amount of 12 v usage, the biggest risk I take is my batteries will not be equalized, which can shorten their life if they get wildly different from each other. Interesting to note is that along with Dick's recommendation was the observation that in systems without the battery center tap, batteries seemed to last longer. That's the crux of the entire argument, and what we are all after - longer life for our batteries. There may have been other factors that came into play in those systems he observed with short battery life. So I will keep flexible and will try to get any other information I can on this subject. I will talk to Dick some more at Bus N USA next month. I note that some of the other regular posters to this board that have extensive electrical experience have been curiously silent on this topic. Perhaps this is new ground for all. | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Jim, From my experience, and I'm sure this matches what most people have seen, a vanner hooked up to an idle bank will always draw power. The vanner is designed to bring the center voltage to 50% of the total pack voltage. This effect is great if you are supllying an alternator feed to the +24 Volt lug of the batteries, but when you stop generating power, the Vanner will "oscillate" charge/discharge from both batteries. I guess the easiest way to picture this is as a teeter-totter. The fulcrum being the center tap, and where the two kids (or the one mean fat kid) sit being the oposing battery poles (GND/+24VDC). Now imagine that the Alternator is spinning and creating a Current/Voltage source of ~28 Volts (typical). The center tap will show ~14 Volts, which is the typical charging voltage for a 12 volt battery (please for the sake of simplicity put the different types of batteries/chargers aside...). When the alternator is not generating current/voltage, the vanner's circuitry still draws voltage across the whole pack (24VDC) which will slowly lower the batteries voltages. Keeping in mind that the vanner uses the presumed STATIC +24VDC lug as a REFERENCE (when there is no voltage regulator/alternator, this lug's voltage becomes DYNAMIC). Other factors like temperature, specific gravity, lead length, terminal resistance, phantom loads, etc., can make differences in the voltage of individual batteries display to the vanner. The vanner will then do it's only job and return the voltage of the center tap to the center of the total voltage. Unfortunately, this isn't being offset by a charging source, so it will slowly bleed off one battery until the voltages are equal. This, as stated before, can lead to an oscillation (very slow, about one cycle per hour, again personal experience viewed with a pair of multi-meters, YMMV) This seems to be a problem with the basic concept (implementation?) of a battery equalizer. It was designed to level off a charge given to a pack, and had the added benifit of providing 12 Volts to other accessories by ensuring the lower 12 volt battery wouldn't be under-charged while boiling off the upper battery. Once the charge is removed, the vanner will actually reduce the efficiency of the upper 12 volt battery by draining voltage into the center tap (basically like pouring a glass of water in a dry salt flat to refill the lake). The power from the upper battery will not extend the usefull time the pack can run a load, and >90% of which is dissapated as heat (which explains the enormous heat sinks on vanners). I have posted previously to an "argument" with JTNG over Propane Vs. Batteries, that the best way to prolong your battery life is to unplug your pack when it's not being used, so a vanner can't draw them down to dead. In your case Jim, some sort of disconnect scheme for your vanner would be ideal, but again it won't protect your 12 volt battery from being under charged the next time you use it. Having reviewed the "Vanner" brand diagrams when I purchased my bus, I rewired the pack with a single 12 volt optima deep-cycle on the center tap lug of the vanner for headlight/clearnace-light loads an placed a schotky diode to prevent "back wash" into the vanner. When parked, an Anderson Power Products (not a sponsor, they make the plugs for electric forklifts, some people just don't know it yet... they are Here) plug is removed and the vanner loses its ground (and because of the diode, there is no complete circuit). The 24 volt pack is left alone (series, no center tap to the 24 volt pack). Remember - "A vanner is an over-glorified voltage regulator." Hope this helps! Cheers Tim | ||
| John that newguy Rating: N/A |
Tim... That was the best, and easiest to understand, explanation of how an equalizer works! Most of the dialog presented on these type threads, are filled with engineer's terms, and are geared for the engineer, not the end user. Your comments are well worth printing out for future reference. Let me be the first to thank you! | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
I have an friend who does technical writing on optics (Perkin Elmer, Kodak, etc.), and he was once quoted as saying "If you find yourself saying 'it's complicated', and you just don't know enough about it to explain it to someone without the diagrams/charts/graphs, then you need to sit down and study it again." I see that as a complement JTNG! Thanks! Cheers! Tim P.S. It occurs to me to state the following after mentioning the forklifts: When was the last time you saw a vanner on a forklift? Maybe we should be designing our battery packs for the load as was originally inteded rather than finding a device which will "fix" the problem... Just a thought... -T | ||
| Jtng Rating: N/A |
P.S., p.s.: -I- did. I decided to supplement the need for electric power by using propane appliances. '>) | ||
| Stan Rating: N/A |
Tim: I wasn't aware of this oscillation and consequent battery drain. Vanner's site states that there is no current transfer unless there is a 12 volt load pulling down the 0-12 battery and then there is a transfer from the 12-24 battery to equalize. I never did a test like you did because I never had a problem of the Vanner discharging the batteries. I can't imagine what situation would arise where the 12 volt battery would be higher than the 24 volt battery unless the 24 volt battery was self discharging. | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
P.S., p.s., pee... I recently got my hands on some of those "new-fangled" Opto-Isolated Photovoltaic-MOSFET drivers, and I'm looking at a way to electronically disconnect my pack from its self when the alternator is shut off (concievably I could even parallel the batteries to actually help out with the load, like in several new Class 8 trucks I've seen). -T Again... P.S., p.s., peeeeeee... I should just build a new alternator/voltage-regulator/battery-equalizer/120-VAC-battery-charger/12KW-inverter/gener ator/air-conditioner-compressor/air-tank-maintainer/flat-tire-changer/VCR/blender/toaster/ reclining-chair "all-in-one" and market it as a "BBS post killer"... LOL -T | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Stan, Take a look at a teeter-totter. It just stays there until something moves (the fat kid on one side, or a 12 volt load in this case). The vanner will act like the teeter-totter and ballance this load out (like giving the skinny kid a pile of bricks which is a load-a resistor which generates heat, or an alternator providing a pull to 28 volts-which is the same as the skinny kid getting a WARN winch to the ground). As for the 12-24 volt battery giving its charge to the 0-12 volt battery, you must remember that the two batteries are tied together (+/-) so the only way for the voltage to be affected is for the vanner to see a voltage reference above ground, which is always static. At this point, the 12-24 volt battery is already elevated 12 volts off the ground (punn intended) so the upper battery can never really get to ground. It could be done by shorting the 0-12 volt battery, which would aggrevate the lower battery's dicharge further, or reversing the polarity of the 12-24 battery which would provide a -12 VDC supply (shorting the 12-24 battery out). Either way the upper battery looses it's charge without contributing anything usefull to the 0-12 volt battery or the load. As I stated in the previous post Your Milage May Vary, I was refering to a newly purchased (for me that is), 1984 Gillig Phantom which had protection diodes on just about everything in the rig, several years of un-hampered corosion on battery terminals an battery cables, etc. Outstanding conditions presented a load to the vanner, even though a 12 volt load was not present. The best way I can explaing this is with "Vanner" brand's own Owner's Maunal for their Battery equalizer. I hope this will be as usefull and easy to follow as the first post, and hopefully Vanner won't sue me for expaining the "marketing": Page 2, "General Description" paragraph 2: "A typical system would include a 24VDC power source, such as an alternator or solar array, two 12 volt battery banks in series, and the Volt-Master Battery Equalizer. The Battery Equalizer connects to the 24 volt, 12 volt and ground terminals of the battery system. When the 12 volt loads require power, the Battery Equalizer ensures that the current is taken equally from both batteries, and that the voltages of the two batteries are kept equal. This equalization ensures extended battery life and provides a stable 12 volt supply for operating accessories." The key thing to see here is that they are ASSUMING that a 24 volt power source is present. They are actually mis-stating what this device does. It "sees" a voltage change because the 12 volt load is drawing more current across the 0-12 volt battery (current source) than the 12-24 volt battery (negative out-of-circuit current source). What the vanner does is increase the voltage visible at its center tap to 50% of the total 24VDC-GND alternator Feed (voltage/current source - in other words, it pushed the fat kid to the middle of the teeter-totter). This will cause a current flow from the 24 volt terminal throught the vanner to the center tap at a voltage determinde by the Vanner as the middle of the 24VDC potential. BUT, remember the alternator is actually providing the power while this is happening. Let's move to Page 5, "Typical Aplications": "Scenario #1 - 24 volt load present, no 12 volt load present. The system operates as a system would without the Battery Equalizer whether the alternator is ON or OFF. The Battery Equalizer is in the standby mode except for making small adjustments to keep the batteries in balance. Scenario #2 - Both 24 volt and 12 volt loads present, alternator is OFF. The Battery Equalizer will insure that both batteries will discharge at the same rate even if different loads are present. Scenario # 3 - Both 24 volt and 12 volt loads present, alternator is ON. The alternator provides 24 volt power to the battery system and to the 24 volt loads. The Battery Equalizer transfers power from the 24 volt source to the 12 volt load by converting 24 volt power to 12 volts. It will supply sufficient 12 volt power to satisfy the 12 volt load and to maintain battery voltage balance." Here, there is one important thing to notice, they do not mention a 12 volt load only with the alternator off. A clever bit of marketing omission. In "Scenario #2", they basically say what I just said about the vanner making adjustments to the batteries to ensure that the batteries discharge -AT THE SAME RATE- a key point. The same rate. Which means that it does not replace the charge, or transfer the power from one battery to another, --it simply expends the higher charged battery's power as heat to keep up with the other load--. Now one COULD conceivably transfer carge from one battery to another, but that would require a four-terminal vanner which could (on a whim) put a battery in either the 24 or 12 voly positions. (several H-Bridge MOSFET circuits as I was poking at with JTNG) And as a breif correction, when I used the multi-meters, the effect was more like a falling leaf-- one battery would drop then the vanner would pull down the whole pack to catch up, then the cycle would repeat... This is all due to a small leak on one battery, and no 24-28 volt power source being available to give a high-voltage reference to the vanner. So Stan, I commend you on having an imaculate power installation, where you obviously either use those battery disconnects that the manufacturer of you rig provided (mine were bypassed by the previous owner >>LTD<<) OR, you have a tidy well balanced installation which is conducive to long storage. But, the bottom line here for those who are reading this and have their head's spinning... If you want your batteries to last, take your power from the top and bottom of your series-pack or just unplug them. Cheers! Tim | ||
| Jim Stewart (H3jim)
Rating: N/A |
So to distill your posts down to action and wiring, it sounds like you are substantiating Dick Wright's recommendation about not using a center tap for house batteries where they are not under charge for most of the day. If the "equalizer" can supply enough current for the 12 volt loads without the center tap, then no need for the center tap. Also, you seem to be saying that its also a good idea to not leave the equalizer "plugged" in all the time, but rather have it switched on only when you need 12 volts. otherwise it continually drains the batteries, especially when it's hooked to a center battery tap. I just looked at the spec's for the Sure Power 80 amp equalizer I have, and the quiescent power draw is 20 to 25 milliamps. This is when there is no 12 volt load at all. When there is a load, it runs between 84% and 94% efficient, the rest I assume is given off as heat. What you are saying seems to make very good sense, but I'm trying to translate this into what you recommend for my wiring. | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Simply (in order of questions), Mr. Wright is correct, It will supply plenty of current (but it will still see a difference in center tap voltage, and, if not disconnected from the 24 volt batteries, drain down the 24 volt supply) Why not use a 12-volt voltage regulator on specific 12 volt appliances? It's more efficient. Yes, it's a good idea to fully unplug the vanner (or at least its ground, as it will not operate without a ground reference) The vanner will draw down batteries if there is ANY imbalance in the system while it's hooked up. The vanner has a small current overhead (about equivalent to an LED so yes ~15-45mA) even when nothing is being used and there are no imbalances. This number goes out the windows the second the vanner begins to equalize (can go anywhere from 1-to-"rated current") which is why one should pull at least the ground. What it does not pass through as voltage is emitted as heat (standard rule of electronics). And to distill it further (using your term...) what I recommend for you is: " Use smaller task-specific voltage regulators which are of high-efficiency for specific loads. Sevral different types of small regulators LM7812, LM317, etc... are available, and can be tuned for maximum efficiency in each task. desings for this can be found just about anywhere on 'The Web'. " Cheers Tim | ||
| Jim Stewart (H3jim)
Rating: N/A |
Thanks for all your input. One more question if you would. How important is it to equalize the batteries under normal usage, with 24 volt loads only and 0000 cables. 6 12 volt AGM's, series parallel. The sense I get is that its not really that much of an issue if you don't draw 12 volts out of the middle, you have adequate size cables, and start with all new batteries of the same size and capacity. | ||
| T. (Bluegrass)
Rating: N/A |
why not use an Inline Diod the power only runs one way, so It could not drain the battery and the cost Is not that much a couple of dollars and then you dont have to remember to turn It off. Tony | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Jim first: If you're not pulling an imbalanced load (12 volts) you shouldn't need to equalize often. A way to "cheat" this is to rotate your batteries when you check them (only works with the parallel-series pack you've described, but it should help keep your batteries replacement times about the same). Of course one still needs to remember to check the batteries from time to time (with AGM you still need to check individual battery voltages, corrosion, cables, etc.) Tony: First, every diode drops (consumes) voltage. Some are as little as .3 volts, but others (quite a few power diodes, the size the are typically used in high current-low voltage circuits like these) drop up to 2 volts. This means that the $400 multi-stage voltage regulator you have will need to either adjust (some with a "sense" wire at the battery, others with a voltage set-point trimmer) the voltage that the alternator puts out. While this can be overcome by most voltage regulators, it has some not-so-amusing effects on your loads and the vanner. Are you running halogen bulbs off the batteries? They are very sensitive to the voltages they see. This is why better voltage regulator companies will put a "halogen" mode on their regs. A few extra volts will make you replace your bulbs little more often (which could get expensive when you're replacing you bulbs every month). And that voltage has to go somewhere (in electronics, if it ain't doin' nothin' useful, it makes a great heater). The vanner or the diode will have to deal with the higher voltage. Do you want to find another ventilated compartment with at least a foot of free-air clearance around it for another device? Let alone the temperature/power de-rating... for those who are not into electrical stuff as much as others dielectic substrates (silicon with chemicals added or "doped" so that it makes it act like a semiconductor) have varying characteristics when exposed to heat (or when it generates its own heat), which affects how they behave (conductivity or its inverse - resistance). Most semiconductors suffer from thermal saturation, which means it starts to create too much heat for it to operate effectively, so it creates more resistance, which creates heat - a runaway thermal reaction called (plainly) "thermal runaway". This'll make some think twice about cramming those big power devices in tight places... (disclaimer: Your-Milage-May-Vary, some may have this setup - in a situation that will not lead to thermal runaway. I'm mearly pointing out that there are many more circumastances that must be considered when adding another device... -T) Second, a diode(s) won't really fix your problem either. Remember that a vanner protects the 12-24 volt battery by producing a higher voltage at the center tap (which appears as a load to the battery-causing a discharge the vanner disputes as heat), and protects the 0-12 volt battery by lowering the voltage at the center tap (causing the same load/discharge on this battery which the vanner dissipates as heat). What this means is, the center tap is by its very nature bi-directional, so a diode would prevent protection of one battery. In fact, if the over charged battery is on the wrong side of the diode's current flow, it could destroy the vanner or the unprotected battery or both (some may have seen this effect if they mysteriously see the vanner's circuit breaker "pop"). One could put a diode at the +24 volt terminal, but this would make the vanner think that something is seriously wrong with the load of the 12-24 volt battery (with no more alternator power, the voltage at the 24 volt terminal will drop because of the draw of the vanner's internal circuitry), so the vanner would deeply discharge the 0-12 volt battery to match the discharge rate of the upper terminal. If the diode was placed in the other direction at the +24 Volt terminal, the vanner wouldn't be able to equalize the charge on the 24 volt battery. because it couldn't get to it (it would leave it charged as the 0-12 volt battery dies). This leaves two more places that a diode could go: Vanner to ground (either the vanner will never see a ground so it won't equalize, or the vanner will still get it's ground reference and it will still equalize despite your diode, and it'll have a new .3-2 volt load to compensate for on the 0-12 volt battery - early death to the 12-24 volt battery) OR Battery-ground to chassis (accepted by the industry as the way to protect 12 volt devices and lights from reverse voltage from the 12-24 volt battery, and full 24 volt transients aka. spikes, surges, etc.) If you look at many installations, using my Gillig as a great example, there are two switches for disconnection: 1) Vanner ground. This one only needs to be rated at the total power output of the vanner (+20% for good safety, an engineering "truth") and prevents the vanner from operating, 2) Battery ground. This one needs to be rated for the peak surge ability of the whole pack and is usually physically larger than the vanner cut-off, and prevents the 24-volt pack from having a ground field (like an antenna, good idea to disconnect when stored for long periods of time) Again, this is why I stated that the best way to protect the batteries for the sake of idiot-resisting (nothing's idiot proof, every time that's said about something, someone goes and makes a better idiot...) your battery longevity. Why spend $50 (+/-) on another failure point? That diode will be a 60-400 watt heater on a 200 amp alternator (explain the heatsinks?). Use a real switch on the ground terminal or at the very least un-hook the ground from the vanner. Fast Fred's method of KISS really applies here. Only use a vanner if you're tapping the battery, and only tap the battery if you have an alternator running (why they made them in the first place...) Cheers, Tim | ||
| Brian (Bigbusguy)
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I dont know about the Vanner draw with a Idle battery bank the working light on my Vanner 100 amp is off when there is no load on the batterys. I will let you all know in a few days my bus have been parked for about 30 days plus with the vanner hooked up and no battery charger on. I will check the batt volts before I start it . I think it should have no more drain on the batterys then it would with out a Vanner. Brian 4905 Oregon | ||
| Tim Strommen (Tim_strommen)
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Brian, You're referring to an idle pack (probably well maintained, with good connections and wires). Your experiment will need regular checks to see any effect the vanner will have (about every 5 minutes. Do you have a data-logging multi-meter? That's the best way to watch this...) I'm interested to see how long your pack lasts, probably a month at least (the lower the pack gets though the faster the drop goes.) Cheers! Tim | ||
| Stephen Fessenden (Sffess)
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Good advice on long term parking. I don't believe it would apply to one or two days, howerver. If I need to park for longer periods without 120 volts for the inverter charger, I will just pull my fuses on the 12 volt line on each of my two Vanner Equalizers. That would prevent the battery drain, wouldn't it? | ||
| Tim Strommen (Tim_strommen)
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"Vanner" brand manual states that the ground lug is the first connection broken and the last one made, and if you disconnect the +12 volt or +24 volt line(s) and not the GND, it will damage the equalizer (probably popping the breaker at the same time... but maybe not). It's probably not pleasant, or clean, but disconnecting the ground is simply "the right way to do it" for longest life - both equipment and battery-run-time wise. Cheers! Tim | ||
| WA David (Wacoastmci)
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OK, read quickly through posts (and hate to be at tail end charlie) but here is the situation as I understand it (based on personal experience with this issue and many $$ until facts understood). First, you must understand that Vanner only takes from high side battery and gives to low side to equalize. It does not equalize both sides. It will not take from low side and give to high-it does not work that way. Second, older vanner families (family 1 thru 4) equalizers require a 2 or 3 amp system load to come on at all, so if you have a Family 1 thru 4 and you are parked, low side battery will go down to nothing while high side stays up since Vanner will not come on. Third, Vanner Family 5 & 6 are designed to come on at low voltage system load so will tend to keep the batteries equalized (only by taking from high side and giving to low side) so that both will go down somewhat equally while parked. The solution to how to avoid killing your low side battery when parked is get a Vanner Family 5 or 6 equalizer AND a low voltage 24 v smart charger. | ||
| Buswarrior (Buswarrior)
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Hello. WA David, how does one identify the family of Vanner one has? The one I have, circa 1990, is left permanently connected to the batteries, at times, for months with no interference from me, with no appeciable negative results. Batteries are right up, and Trace only goes to a couple amps when I plug it in after extended battery switch off storage time. happy coaching! buswarrior | ||
| Tom Caffrey (Pvcces)
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I don't believe that it makes any sense for the equalizer to take any power from the 12 volt tap for any purpose other than to measure the voltage. As for the waste heat issue, silicon power diodes only have a .4 or so voltage drop. They would fry if they had a 2 volt drop in high current applications. The Schottky seems to cut that loss to between 1/2 and 1/3 of a silicon diode. Nearer 1/2 when it is cold and closer to 1/3 if it gets nice and warm. This is why they are used in battery isolators. Does anyone here know if the ground lead in an equalizer conducts any amount of current? I was thinking that it might only be used for voltage sensing, but I don't know. Just my two cents. Tom Caffrey PD4106-2576 Suncatcher | ||
| Brian (Bigbusguy)
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Ok checked the volts of my start batts after 6 weeks of no starting and no charging only the Vanner 65/100 on them. With no other volt draw. 74' out side temp. Both batts at 12.3 volts. So I would say it will be fine and will not draw down you batts. The bus started just fine. So there one more myth busted. Brian 4905 Oregon ? | ||
| Stephen Fessenden (Sffess)
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12.3 volts is low. Should be 12.65 volts fully charged. 12.0 is discharged. | ||
| Brian (Bigbusguy)
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I would call that still in the safe zone . I was also running off the inverter for lights when I first parked it so there was a small drain on them I dont know what the volts was when I left. But the equlizer did not run down to nothing or go too low to start it easy . And it was 12.37 so It was fine . The equlizer only uses 17mil amp and will not come on unless there is a .5 volt differance. I dont know what a normal batt will go down to in 6 weeks but I normaly keep a charge on them . So its nothing to worry about the equlizer will not run them down . I found this some place a few years ago: (It is believed that a partial or full discharge applied once every six months or so enhances the performance of lead-acid batteries. Avoid too many full discharges, as this would wear down the battery unnecessarily.) True or not I dont know? Brian 4905 Oregon? | ||
| Craig (Ceieio)
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Hmmm interesting information. based upon Tim's info it might be a good idea to put a high current relay on the Vanner ground leg that is switched by the bus master switch. With my bus I don't have the master on much unless the engine is running. Kill the bus master and it will break the Vanner ground and take the Vanner out of the equation. The bus master could break the Vanner on both a bus bank and a house bank with two seperate relays. Realys are pretty reliable and this way it would all be "automatic" Craig - MC7 | ||
| Stephen Fessenden (Sffess)
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Actually you want the Vanner working. It would not be good to find that the batteries had discharged unequally, like only the lower battery is near dead. Better to charge the batteries occasionally and have them equalized all the time. They will last longer. |
