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Old 09-28-2022, 02:13 AM   #1
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Join Date: Feb 2021
Location: Denver
Posts: 7
Year: 2004
Coachwork: Gillig low floor
Engine: 8.3 cummins allison b400r trans
8 volt batteries multiple units

I usually can get By with 12 volt batteries, but I want to purchase someone's 15- 8 volt batteries that were in an electric car. I thought to parallel 5 batteries to a pack of 3 to make up 8volt however many amps and then series to build to 24 volts to an inverter. Big question Is this a way to go or am I nuts? The batteries in question are 15 US Battery 8 volt batteries US8VGCHC.
I am trying to set up 24 volt internal house system in my bus that has a 24 volt system. That I hope to charge the house Battery from the bus charging system. Most stuff will run 12 volts with the inverter running my propane/ electric fridge with 120 volts. So am I going in the right direction or is this too complicated? I am NOT in a rush to create fires so help from someone who has done something similar would definitely be helpful.

Thank you. Marty

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Old 09-28-2022, 07:40 AM   #2
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Hi Marty, that will certainly work and will give you about 10kWh of usable capacity (if I did my pre-coffee math correctly). i also have two buses with native 24V systems and I am a big fan of matching the house and chassis battery voltages, in most systems. Those 8V batteries will work to create a 24V house bank and, if your bus is 24V, it can charge your house bank...and you can also use the house bank to charge up your starter batteries, if you get in a bind.

One consideration, though. In your Gillig, the 12V is provided by pulling it off one of your starter batteries. Your house bank, with 8V batteries, won't give you a direct way to get 12V for your MaxxFan and all the other 12V things...and you won't want to use the starter batteries for those. You'll need to get a 24>12V DC converter to provide 12V from your house bank. That's common and not a big deal...just something to plan into your system.
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Old 09-28-2022, 07:44 AM   #3
Join Date: Mar 2020
Location: Raleigh NC
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Chassis: TS FE 2509
Engine: Cummins 5.9l ISB CM550
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I was told if you want a 24v system use all 24v batteries that way if one battery goes bad your whole system won't go down, just a thought. I also heard the chemistry of e car batteries is much more volatile.
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Old 09-28-2022, 08:46 AM   #4
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Originally Posted by Hutchy View Post
I also heard the chemistry of e car batteries is much more volatile.
These aren't electric car batteries as you'd find in a Tesla or Volt. These are standard lead acid batteries, so not volatile at all...besides the hydrogen gas, of course...but they're not the same chemistry as the production electric vehicle batteries. LiFePO4 batteries are great, but if the OP can get a good deal on lead acid batteries then one nice thing is that they can be charged directly from his bus alternator. Pros and cons to all options...
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Old 09-28-2022, 09:59 AM   #5
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In most 24 volt coaches / busses with a 12 volt sub system they usev2 12 volt batteries and tap the 12 volt. Then there is a battery equalizer that keeps the charge in both batteries the same. If you have that in your bus then you will have to think a bit more when you use the three 8 volt batteries in series.. as Ross said you might need a 24 to 12 v converter because that would draw an equal current from the three batteries, so equal discharge.

Good luck,
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Old 09-29-2022, 02:09 AM   #6
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Coachwork: Gillig low floor
Engine: 8.3 cummins allison b400r trans
8 volt battery

I have decided to not use the 8 volt batteries idea. It is me that I think is the KISS. The stupid part. I keep thinking if out in the outback camping and something should happen to the system, I would be somewhat inconvenienced ( not catastrophic) but my brain hurts when I think about it. So I will stick with 12 volt batteries. Thanks for the info that I had the right start. I was also taken back by making all the cables to hook them up.

Thanks marty
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Old 10-08-2022, 08:18 PM   #7
Join Date: Feb 2016
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24 v batteries

Maybe look at signature solar 24 volt eg4 lipfepo batteries 50 amp I believe stackable, 80% depth of charge great price and no gassing. I'm using the 48 volt 100 amp version. With a nice size Inverter almost everything is 120 volt. Way more cost effective per watt than any lead acid.
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Old 10-09-2022, 06:54 AM   #8
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My bus is native 12 volt and my coach batteries are 24. If you do use one, or more, 24-12v converters...make sure you can turn them off. They like to hum and keep themselves warm...idle current, and it adds up fast.
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Old 10-11-2022, 03:05 AM   #9
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I did the maths on various batteries for our house rack.

With any lead acid battery (flooded whether "sealed" or not, glass mat, or gel) you can only use about 50% of the battery rating before damaging them. Going to 60% will cause damage which accumulates, go too low and you will hurt them immediately. So to get a given amp hour of useful power you need batteries with double the needed capacity.
You will also need to replace them every 3 or 4 years at best and they weigh a LOT when you add up all the batteries, racks, cables, etc. necessary. Plus they take up a lot of space.

With lithium you can pull every watt out of them though 80% will give longer life. This means less capacity needed.
After doing all the maths on weight, cost, space, complexity, etc. we decided to go with the EG4LL 24 volt lithium rack mount units. Just two of these batteries give us 10.24kWh of storage with a battery weight of just 202 pounds. Our initial design is for just TWO batteries in a rack capable of holding FOUR. The two extra spaces will be drawers unless we determine that we need another battery. If we do, we can simply remove a drawer, slide an additional battery in place, and make a couple of simply connection changes.
Each battery is capable of 100amps continuous output with 30 amps recommended. That's 30 ea for 60 amps at 24 volts..... a good amount of juice. They are also guaranteed for 5 or 10 years depending on which of the two models you purchase and rated to have 80% capacity remaining after 7,000 cycles to 80% discharge....that's 19.5 years.
Signature also has a 6,500 watt "all in one" inverter with built in dual charge controllers, battery charger, and a monitor/setup module that can be removed and mounted anywhere in the rig with a simple plug in cable. That inverter is only available in 48 volts so we will configure our 24v batteries in series for 48 volts and if we need to upgrade storage signatures engineers have told me that yes, I can then parallel a 48 volt battery to the two 24's and they'll all play nice as well as with the inverter.
And, with 2900 watts of solar panels on the roof, those lithium batteries will suck it up far faster and more efficiently than any other available battery chemistry.
For us it was a no brainer on the batteries and they are currently powering my HAM shack (4 months pulled them down 30%). The inverter was a change from the planned Victron MultiPlus. The specs on the inverter fit our plan better and at a significant savings over Victron gear which required at least two $300 plus controllers, a separate communication module for the MultiPlus and a separate screen for monitoring. About double what the Signature solar inverter instal will cost and the signature inverter is designed to plug and play with the BMS in the EG4LL batteries.
Another no brainer when that inverter hit the market.
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