| Author | Message | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 451 Registered: 8-2004 Posted From: 70.60.107.113  Rating: N/A |
I'd like to ask advice and info on real-world experiend. My bus is 24V starting but I have an additional alternator to provide 12V for house batteries. Here are some issues: 1) It may be possible to swap that 12V alternator for an additional 24V; that will mean a significant 24-12V converter for powering 12V items. So, do I stay with 12V for the "house" side; running straight from the 12V system for 12V items, or switch to 24V. Of course, whichever I go with, the inverter will have to match it. 2) I don't have any idea of how much house battery power I'll need. I don't have "bays" but I'm in the middle of redoing my floors and I've found an open floor area that will allow me to build in a sunken area (vented) that will give me room for 2 Type 31 start batteries (in series for 24V) and 6 T-145 6V "Deep Cycle" batteries for the house. This will give me three 12V pairs. The T145's are rated at 260 A/Hr (20Hr rate) at 6V. Would a pair give me 260 A/Hr at 12V? If so, that would give me ~780 A/Hr total for 6 batteries at 12V. So, those are my parameters. Specific questions: A) I have a perfectly good 24V/Start and 12V/House separate alternator system. Would the advantages of a 24V/24V combo be worthwhile enough to tear what I have out and start over? B) Would 6 T145 Deep Cycle 6V batterie at 260 A/Hr each give me a reasonable amount of battery capacity for "boondocking"? I have propane for the "cooktop" burners and hot water. Thanks for your advice. BH, NC USA | ||
| joe padberg (Joemc7ab)
Registered Member Username: Joemc7ab Post Number: 361 Registered: 6-2004 Posted From: 66.38.159.33 Rating: N/A |
Bruce 12 volt house is the most common, a 780 A/hr bank is larger than what most people have. This is an instance where larger is definitely better, and it should be a reasonable amount if careful while boondocking. The following references have alot of usefull info. Phrannie.org/battery.html The 12 volt side of life www.ccis.com/home/mnemeth www.uuhome.de/william.darden/ | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 968 Registered: 1-2003 Posted From: 67.142.130.13  Rating: N/A |
1) It may be possible to swap that 12V alternator for an additional 24V; that will mean a significant 24-12V converter for powering 12V items. So, do I stay with 12V for the "house" side; running straight from the 12V system for 12V items, or switch to 24V. Of course, whichever I go with, the inverter will have to match it. The inverter will be your largest DC load, and 24v inverters are generally more capable than 12v ones. Also your cables, fuses, lugs, etc. will all be significantly smaller for 24v. Not sure why you say "significant" converter. If you go 24v, you should, instead, use mostly 24v items where DC is called for. Mostly that would be lights, and every 12v lamp has a 24v equivalent. These are usually about twice the price, but in five years we've replaced maybe two bulbs, and that's full time. LED items available only in 12v can be paired in series. That really just leaves small loads like fans, igniters, and alarms, unless you have 12v blowers for, say, a furnace (which can easily be changed to 24v). Water pumps are available in either voltage. You should really be able to get away with a very small equalizer, say 20 amps or so. Remember, with a properly wired equalizer, you can draw much more current from the 12v side when needed, and the equalizer will replace that charge over time. 2) I don't have any idea of how much house battery power I'll need. I don't have "bays" but I'm in the middle of redoing my floors and I've found an open floor area that will allow me to build in a sunken area (vented) that will give me room for 2 Type 31 start batteries (in series for 24V) and 6 T-145 6V "Deep Cycle" batteries for the house. This will give me three 12V pairs. The only way to know how much you'll need is to calculate it. That takes a lot of work, but there is no way around it. You will need the draw for every item you will run, the length of time you need to run it, and the time between charge that you want to achieve. Don't forget to figure in all the losses, and if you use flooded batteries, figure on only drawing them down to 50%. The T145's are rated at 260 A/Hr (20Hr rate) at 6V. Would a pair give me 260 A/Hr at 12V? If so, that would give me ~780 A/Hr total for 6 batteries at 12V. Yes. A) I have a perfectly good 24V/Start and 12V/House separate alternator system. Would the advantages of a 24V/24V combo be worthwhile enough to tear what I have out and start over? That can easily be calculated. A lot depends on what you've already got, and what you still need to get. Inverter? Fuses? Cables? The usual reason for going with a 24-volt house system on a 24-volt coach is to be able to easily charge the house batteries from the coach alternator. If you need two alternators anyway (because the chassis one is too small), this is less of an issue. The other major benefit, of course, is the ability to tie the two systems together, either to provide additional alternator power to the house side, or to "jump start" the chassis side. B) Would 6 T145 Deep Cycle 6V batterie at 260 A/Hr each give me a reasonable amount of battery capacity for "boondocking"? I have propane for the "cooktop" burners and hot water. Depends on what else you run and how long you intend to boondock. That amount is more than most, but not enough for some of us. You'd have 9,360 usable watt-hours from that arrangement; we have nearly double that at 17,660 and find it barely adequate sometimes. YMMV. HTH, -Sean http://OurOdyssey.BlogSpot.com | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 969 Registered: 1-2003 Posted From: 67.142.130.13 Rating: N/A |
Only on 12-volt vehicles or boats. On 24-volt vehicles or boats, 24-volt house systems are more common. -Sean http://OurOdyssey.BlogSpot.com | ||
| Stephen Fessenden (Sffess)
Registered Member Username: Sffess Post Number: 763 Registered: 1-2002 Posted From: 66.38.120.219 Rating: N/A |
I changed to a 24 volt house system when I bought my bus. It has a 60 Amp Equalizer on both bus and house systems, so I can use fairly heavy 12 volt loads. I once travelled over 1000 miles with after an alternator went out, using the solenoid to connect both systems together. If I had had a separate 12 volt system, we would have been in trouble. It is always nice to have rendunant systems and be able to fix things when you get home. | ||
| Stephen Fessenden (Sffess)
Registered Member Username: Sffess Post Number: 764 Registered: 1-2002 Posted From: 66.38.120.219 Rating: N/A |
I have also started the bus with a weak bus battery by flipping the switch to connect house batteries and bus batteries. Redundnacy again. | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 455 Registered: 8-2004 Posted From: 70.60.107.113 Rating: N/A |
Thank you, Stephen. I do think that a double-24V system would be best but my dilemma is whether the benefits would be worth it for go through all the issues to change. On the other hand, I'm guessing that the only real changes would be to replace the 12V alternator with a 24V and wire in an equalizer. I like your theory on redundancy, too; I'm building in redundancy in other things, too. | ||
| Nellie Wilson (Vivianellie)
Registered Member Username: Vivianellie Post Number: 267 Registered: 11-2008 Posted From: 75.178.92.43  Rating: N/A |
Hey Bruce - Curious why you'd need a 2nd alternator. Can't you just charge from your existing coach alt... or is this (the second alt.) another redundancy feature? I'm in the middle of the same process. Started with a 12 V system (barely sufficient to run lights and a radio) but after talking with a lot of cluey people, I've concluded 24V makes much more sense, well worth the change-over (which really isn't a big deal). Besides the benefits Sean mentioned (the most important being backup for starting and ability to charge from the coach alt.) there are more (and better) accessories for 24V (or so I've been told... lacking funds to buy anything anyway, I haven't investigated that claim yet). And you may not need anything fancy to run whatever 12V stuff you've already installed... like radios and such. You can always use the factory installed 12V posts, or run a center post lead (like MCI did). Or use a 'step-down' device (converter, resistor, etc.) for whatever 12V stuff you keep. Understand, this is not first-hand knowledge, just passing on what I've been told... so we'll see. The proof's in the pudding, right? The Best, Nellie Wilson | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 457 Registered: 8-2004 Posted From: 70.60.107.113 Rating: N/A |
Nell, I needed some work done on my transmission and the guy who did that work had a bus with an engine like mine. He had put on a 12V alternator to run big 12V loads on his bus and he suggested that it would be a good idea. I like the redundancy issues, but I'm really coming to think that both should be 24V systems. And there is the issue that a second system will give you the big charging capability for when you need it. I'd hate to have to choose between running air con and charging the start batteries. I think that this is one of the "no perfect answer" areas. A well-designed system with one alternator should do very well; a well-designed one with two should do well, too. The two-alt system will be more expensive but offers redundancy. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 953 Registered: 10-2006 Posted From: 76.202.165.190  Rating: N/A |
Having a really outsized 12V house system is great BUT , it is easy to destroy by discharging and not completely recharging . My suggestion is an E meter , a Trace SOC (state of charge) or a Bogart engineering unit FIRST. This will at a glance tell you exactially where the batts are in terms of being charged. $150 to $200 but the BEST bucks you will ever spend if you want to boondock . Second best bucks is at least 1 - 75W or bigger solar to keep the charge as close to 100% full as you can, silently. FF | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 458 Registered: 8-2004 Posted From: 70.60.107.113 Rating: N/A |
Thank, Fred. I forgot to mention that a good SOC meter will be an important part of my system. How big is a 75W solar panel? My bus is right at 13'6" height so I can't add *any* height; therefore I can't to a permanent mount on the roof. I suppose that I could have it arranged so that it folds out from the side of the bus. It sure sounds like a plus in any system but I'm not sure that it's practical for me. I'm guessing that the systems (i.e. available inverters/ pass through, battery charger, etc.) that most of us are using are already set up for solar input, right? | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1712 Registered: 12-2000 Posted From: 76.68.135.14  Rating: N/A |
One of the greatest advantages to a solar panel is maintaining the coach batteries at all times when it is parked between uses. The solar panel's role is to finish the job, topping them right up, and keeping them there. FWIW, the new coaches have been coming with twin alternators in them for a few years now, Bosch air cooled units being the popular choice. happy coaching! buswarrior |