How to Run a 24V battery bank in an RV?

[Derek884]

So, paralleling batteries is bad. I want to run a 4800 watt power bank. This seems to require a 24V or 48V battery bank. My question is how do you run a 24V or 48V battery bank in an RV when everything is run of 12VDC? I assume you would have to start by replacing the converter. How do you convert it to 12V and does this make sense?

Thanks,

Derek

[Mike90250]

What is a 4800w power bank? Is that a 4800w Inverter to provide 12V ac power ?

[Derek884]

6 volt 200amphr battery x 4 = 4800 watts

[Mike90250]

6 volt 200amphr battery x 4 = 4800 watts

Close, but no cigar. try this out (you left out the hour spec)
6v x 200 ah = 1200wh x 4 = 4800 watt hour battery pack. Erase the words "power bank" - there is no such thing.

If you are in an RV, that is a unique situation, where a lot of gear is pre-installed and wired for 12V. No promises it's been done right, heavy gauge wire is expensive.
Your engine has a nice big alternator that can put more charge into the battery in a half hour, than a whole roof full of PV could do in a day. Remember that when counting panels, mounting holes into the roof, and hoping it's done so it wont blow off in a wind as you hurtle down the road at 65mph


12V @ 400ah can be done with 2 big L16 size 6v batteries, wired in series. fewer caps to check for water, cables to check for coming loose, and less parts to mess with

[Derek884]

Sounds good. Do you have a suggestion on where to buy batteries. Shipping is expensive, so I was hoping to find somewhere local. (Denver, CO)

There is Sams, which has Duracel

https://www.samsclub.com/sams/batteries/3990105.cp?pageView=grid&searchCategoryId=3990105&navAction=pop&rootDimension=automotive_battery_type:Golf%20Cart%20Batteries:Commercial%20Batteries&altQuery=100001_1055_3990105&totalLimit=48&recordType=all

Batteries Plus

https://www.batteriesplus.com/productdetails/sli6v370s

Interstate

https://www.interstatebatteries.com/products/l-16s

[Derek884]

Sounds good. Where do you recommend buying a battery? My local places are interstate, batteries plus, and Sams (Denver, CO)
That gives me Duracel or Interstate batteries.

https://www.interstatebatteries.com/products/l-16s

https://www.batteriesplus.com/search?q=l16

[Derek884]

Sounds good. Where do you suggest buying batteries? I live near Denver, CO. I have Interstate, BatteriesPlus and Sams Local.

[Sunking]

Sounds good. Where do you suggest buying batteries? I live near Denver, CO. I have Interstate, BatteriesPlus and Sams Local.

Not a single one of those companies make batteries. Find a Trojan dealer.

[OldSmokey]

I have done this and my system is 48 Volts.
these are the main components.

1. I have 960 watts of solar feeding a 48 Volt 300Ah battery pack with a Victron 150/35 CC
2. Provide power to the RV with a 48 Volt to 12 Volt buck converter like this one:
https://www.amazon.com/uxcell-Converter-Regulator-Transformer-Waterproof/dp/B01M06Q94K/ref=sr_1_1_sspa?ie=UTF8&qid=1523540004&sr=8-1-spons&keywords=48v+to+12v+converter&psc=1
3. Remove the old WFCO POS 12V converter
4. Provide battery charging and AC inverter functionality with one of these:

https://invertersrus.com/product/sp-ic2248/

not perhaps the best choice, but a good compromise for my requirements.
5. fit a small group 24 size battery on the tongue for the braking system fail and to power the tongue jack.
6. fit a battery isolator to the truck to charge the group 24 battery.

So I get 12V for the RV main systems with the buck converter
The brakes and jack are powered from their own 12V battery
The 12 V is charged from the battery isolator and I get auto change over when I connect to mains power or generator.

you will need to use 24V versions of these in your case.

[OldSmokey]

deleted post, duplicate

[Sunking]

6 volt 200amphr battery x 4 = 4800 watts

You need to get your noodle wrapped around the difference between between Power (watts) and Energy (watt hours) as they are not the same thing. Think of it this way. Your car has a 250 hp engine. How far will it go? You cannot answer because the question is nonsense.

Power = Watts = Voltage x Current
Watt Hours = Watts x Hours = Battery Voltage x Amp Hours
Amp Hours = Amps x Hours

Example a 100 watt light bulb ran for 5 hours uses, 100 watts x 5 hours = 500 watt hours. If that light bulb uses 12 volts would use 500 watt hours / 12 volts = 41.67 Amp Hours. Critical you understand that in detail. Power is a rate at which Energy is being consumed.

So you have a 12 volt 400 AH battery configuration which is perfect for an RV. You would need a panel Wattage of 500 to 700 watts, with a 50 to 60 amp MPPT charge controller to supplement your Electronic Battery Isolator when the engine is not running. Vehicle alternator will do the bulk of power generation. Use 400 AH batteries, not 200 AH batteries as you want to avod parallel configurations.

[mba83]

Would it be OK to hook up the 12V battery to the 24V/48V system through a DC-DC converter? (I'm thinking of using a converter that puts out 13.8V so that it always keeps the battery topped of). Or would there be any issues with this setup? I know it won't be a "true" charger setup, but for lead acid battery I'm thinking this will work just like a car generator typically works.

Thanks!

[Mike90250]

If the DC-DC converter is robust enough to survive, yes, it would work. When batteries are low, they can present a large load for a few minutes, and your DC-DC may not like that. Battery chargers are designed to charge into a low battery and not reset or shut off

[mba83]

This 12V "car" battery would typically be close to fully charged. The idea is to have the 40A DC/DC converter be constantly keeping it topped off (stand by charging / floating at 13.8V).

Thanks

[mba83]

I plan to use this regulator: https://www.amazon.com/dp/B01LY8D7U0...I1RNM3QIKLRZOQ