| Author | Message | ||
| Steve Fessenden (63.27.88.69) Rating: N/A |
Tom: I have dealt with the suggested system of two 12 volt chargers for a 24 volt system. It doesn't work well enough. Neither does having a separate 12 volt alternator charge the lower battery. A vanner equalizer is proven technology and it does work on the bus, not just in theory. I got the answer to my problem from an email from a question on this board last year. Too bad it wasn't posted on the board instead. I checked with Vanner on how it works before I bought. I have a 60 Amp Vanner Equalizer. Cost under $300. Costs less than the batteries it manages and increases their life. It hooks up with three wires: one (fused) to the 24 volt battery terminal, one (fused) to the 12 volt battery terminal and one to the battery ground terminal. Thats it. Unless you get the batteries way out of balance the equalizer will keep them each at the same voltage, +/- .05 volt continuously. It works whether you are charging or not. If you are charging it passes more current to the 12 volt battery until the voltages are equal. If you are discharging the 12 volt battery it passes current from the 24 volt battery to the 12 volt battery to keep the battery voltages the same (equalized). Since I have a 60 Amp equalizer it can pass up to 60 amps to the 12 volt terminal continuously. If you have a higher draw than 60 Amps for a short time the batteries will get a little out of balance but the equalizer will keep putting out at its max after the load drops, catching up and rebalancing the batteries. If you have more than 60 Amp draw for a long time the batteries can get so far out of balance that the equalizer cannot catch up. You don't want to exceed its capacity with CONTINUOUS loads. HEADLIGHTS: If you want to run 12 volt headlights off the center tap only you will probably need a 100 Amp equlalizer at about $850. There are other ways to wire 12 volt headlights. One, like Prevost is to run the Left side using the 12 volts between the 24 volt battery terminal and the 12 volt battery terminal, and the right side between the 12 volt battery terminal and ground. Another is to use headlights that use a 24 volt H4 halogen bulb. Other loads you might be tempted to run that way are usually not that close to balanced. I had six heater blower motors wired half 24 to 12 and half 12 to ground. That is not a balanced load because the motors don't all run at the same time or for the same amount of time. Steve Fessenden | ||
| CoryDane N/E IL (4.17.253.179) Rating: |
It seems to me that if you are looking at putting out $850 dollars for an 85amp equalizer, it would be more to an advantage to get the $450 24v to 12v converter at 80 amp instead. = dollar for dollar the converter is a better deal and wiring is simple to deal with. - Why do you suggest that two 12v chargers will not properly take care of a 24v bank of batteries? I had hooked my bus batteries up to the solar cells to 12v regs to the battery, each to a 12v bank (the battery is connected in series to provide 24v) and it has worked for years now with no problem. - the Equalizer you speak of sounds like it would work but it may have charging discrepancies from what I read of your post. the inverter has an excellant charger @24v and does a fine job.- - Better to save a buck on a proven Converter than to throw more out when you dont need to to do the same thing. The converter does not have any problems with heavy loading as it take power over all the batteries where you mention the equalizer has its limits. Already a bad point even before the message is out. = If anyone is considering these options, take a good close look at them before you spend that kind of money and go for the best, or best price, for your application. They both sound like they will work but one seems to have limitations, however, if younever approach the operating limits, you would justify the extra bucks. Other than load limit (75-80 amps) I cant think of a single bad thing about the 24v to 12v dc converter that you need to be concerned with unless someone else out there knows of some concerns, let us know-cd | ||
| Steve Fessenden (63.25.54.5) Rating: |
A converter doesn't prolong battery life. Even when you are drawing 24 volts only, the two batteries in series can end up with different voltages and charge levels. An equalizer prevents this. They are used in trucks, buses, factory conversions. Some bus companies used to rotate the batteries to prolong battery life before equalizers. Check www.vanner.com When you are ready to buy, call the tech department and ask them to explain it. That is what I did and why I went with an equalizer. They make converters too, so I got an accurate explanation, not a sales pitch. The only time an equalizer doesn't work well is when it is undersized. The worst case senario I mentioned was to warn people not to try to get by on an almost big enough equalizer. I would design for as much as possible to run on 24 volts. Then I would use an equalizer and center tap for most of my 12 volt load. Cost: less than $300. Finally, I would use small converters at the appliance for a few voltage sensitive items. In Good Sams "Highways" magazine one guy said he found a voltage of 11 volts reaching his suburban gas heater. He had multiple circuit board replacements before he found that he had a big voltage drop. The circuit boards could take high voltage but not low. That is a great use of a converter. It will put out the rated voltage, exactly, until the input voltage is too low for it to function. You can accomplish that with a much smaller converter. I was able to get physically small surplus 25 Amp 24 volt to 12 volt DC to DC converters for $20 each. 10 amp for $10. $850 was for the 100 Amp equalizer. I don't think any of us really need that. $280 is the cost of a 60 Amp Vanner Equalizer from a distributor. I got mine from Ohio. A converter can never handle much more than its rated output, even for five minutes. The power to the load goes THROUGH the converter. An Equalizer can handle battery loads of more than its rated output because the power comes directly from the battery. If there is a 12 volt 90 amp draw for five minutes and then the load drops to 30 Amps a 60 Amp equalizer will continue to put out 60 Amps, 30 Amps morre than the present load, until the battery votages are equalized again. Steve Fessenden | ||
| Bill K. (209.173.120.92) Rating: N/A |
Here is what I did, I taped into the house batteries for the headlights, I have a 110 alt on the bus eng. Then for a backup Iam running a extra set of running lights 12V and some extra clearance lights using a 24V to 12V convertor, the running lights draw around 4amps each and the clearance draws .3amps. I have a 25 amp convertor continuous duty which I bought from the surplus center cost 200. I have 4 golf cart batteries on the house system. I wanted the 12V off the 24V with the big bus gen. just encase. I would not want to be out on the big highway late at night without lights if the house system failed. | ||
| gary (64.12.106.24)
Rating: N/A |
I am running my head lights off my house batteries . I use a 70amp vannier equalizer to get 12 volts from the 24 volt house batteries.Clarence and tail lights are 24v from starting batteries. So far this system is working perfect. | ||
| Buswarrior (Buswarrior) (152.163.201.206)
Rating: N/A |
Hello everyone. Perhaps you need to know that all the new coach and transit manufacturers have been using Vanner Equalizers to get 12 volts for many years now. All the lighting on the new ones is 12 volt, big alternator still cranking out 24 volt to power the HVAC and keep those big batteries charged. These devices work fine, and do not do anything evil to your batteries. They are easy to install and need no supervision or attention. Provided that the purchaser doesn't try putting one in that is too small, trying to economize....it will never bother you again. Find the folks who buy up your local transit surplus. When an equalizer fails, often these are changed out for a new one, because the mechanic either doesn't know how to fix it, or is told to swap to save time, when all they need is solder. Pick up a reconditioned one and get some of your tax money back! happy coaching! buswarrior | ||
| Frank Wells (161.184.178.35) Rating: N/A |
This is what I did on my 5A. I got 12v off the 12v genset battery added a 12v alternater to the coach engine to maintain charge and a relay at the 24v coach light switch. Bingo 12v headlights. I am probably not the first to do it this way, but it works for me. Unless you have a vanner which I am sure is also a good fix I would not be looking for 12v off one battery in a 24v system. out of balance battery banks equal short battery life | ||
| Jim Ashworth (Jimnh) (172.158.229.193)
Rating: N/A |
For headlights (4 @ 55 watts = 220 watts) use a 20 amp vanner equalizer. These headlights will draw 18 amps. No need for a big equalizer. Install a Grainger cube relay actuated by the existing 24v headlight system to control this 12v to the headlights. Normally closed goes to low beam and normally open goes to high beam. Simple, foolproof and CHEAP ('cept for the equalizer!). Had this on my MC-8 for 9 years-- never a battery or relay problem. Oh yeah, by the way, if you have circuit breakers on the headlight wiring (like the MC-8 had), you will have to replace them with double the rating (12v draws 2x the amps) and consider changing the size of the wire also if it is a long run. Jim NH | ||
| Steve Fessenden (63.25.54.93) Rating: N/A |
Fusing an equalizer. When you go to install an equallizer, an unexpected cost can be fuses. A 60 amp equalizer requires a 40 amp fuse on the 24 volt connection and an 80 amp fuse on the 12 volt connection. You can use two fuses in parallel, safely and by the code, to get the required size. I used two 40 amp fuses on the 12 volt connection. Giant (Maxi) auto fuses, which are on the rack in Autozone and other stores next to the standard ATO plug in fuses. I got the in line holders for these at Skycraft surplus in Orlando, if you can't find them elsewhere. Should be able to order them from an auto parts store. The inline holders for giant plug in auto fuses have 8 ga wires. Steve Fessenden | ||
| FAST FRED (63.215.231.232) Rating: N/A |
The West Matine Catalog has a large number of large fuses and holders, that would work for a converter. To DC fuse an inverter is a much bigger job, requiring classT fuse holder and fuses. A small #6 wire cant carry much juice if the fuse fails , before it becomes a fuse,and burns out someplace. But that great 4/0 can carry soo much juice that a lesser A {auto or marine} fuse cant break the current that can be hundreds of times larger than the rated cap of the fuse. Thats why they make class T , it will break thousands of DC amps { as usual they aint cheap}. FAST FRED | ||
| Jim Ashworth (Jimnh) (172.162.75.37)
Rating: N/A |
Correction to earlier post regarding relay control of headlights. My MC-8 has been sold and I went from memory on the earlier post. Wrong thing to do. Two 24v cube relays were used, one for low beam and one for high beam. My apologies. Jim |
