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24v Battery Bank, 12v RV Questions

I have built an 24v 400ah lifepo4 battery bank for my rv. I have 970w of solar connected through a 60a mppt to the battery bank. I am missing a couple pieces to complete my system and I need some direction from someone with more experience than myself.

I understand having a step down converter from 24v to 12v for critical loads from the battery bank, what I am struggling with is twofold:

1) the 12v power from the secondary alternator in my truck that charged my previous battery - how do I go about using it (safely, and without damaging the batteries) to charge the 24v system.

2) My Fifth Wheel is setup with the Progressive Dynamics #PD9260 12v power converter for when I am connected to shore power, which also charged (albeit slowly) the previous battery - how do I safely charge my 24v battery bank without having to gut everything?


What products do you recommend that could help with these situations?

(I.e previous battery was lead acid - new battery bank is lifepo4. AC power runs 15k BTU A/C units and microwave, though only on shore power, only has 1kw inverter currently [it’s on the list])



battery chargingLithium Battery
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kevgermany answered ·

1 use one or more Orion 12/24 chargers in parallel

2 depends. Assuming you're going to put a suitable inverter in in the future, might be worth going to an inverter/charger now - look at the multiplus/quattro ranges.

However I'm not understanding something. What do you mean by 15k AC? 15kW?

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derrick thomas avatar image derrick thomas commented ·
OP means 15k BTU output air conditioner.
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solarnewb avatar image solarnewb derrick thomas commented ·

Precisely. Two 15k BTU A/C units

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solarnewb avatar image solarnewb commented ·
Multiplus seems promising but will it handle both the 12v and 24v? Been looking at the wiring schematics for some of them and I’m still unclear on that. As for the more

Powerful inverter I don’t need anything significantly more powerful as even with 10kwh battery storage it won’t last long with a 1500(1 a/c unit) or 3000(both a/c units) draw - so it seems I will have to rely more heavily on a generator for that.


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kevgermany avatar image kevgermany ♦♦ solarnewb commented ·

Multiplus is single DC voltage.

So you need a 24V unit.

I've got a similar setup.

Orion 12/2-15 from alternator to house batteries. A second is going in.

24V Easysolar (integrated multiplus and MPPT). Charges house bank from grid and sun.

Orion 24/12 converter for the 12V DC loads like LED lights, fans etc.

non-Victron Trickle charger to maintain starter battery from house battery converter 12V when parked up on shore power and winter.


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solarnewb answered ·

Seems like the best route from the alternator is simply going to be an Orion 12v/24v dc dc charger, though I am not finding anything higher than 15a - which is unfortunate. Still on the lookout for the power converter side of things

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kevgermany avatar image kevgermany ♦♦ commented ·
Yes, that's why I said you can use more than one in parallel. Load current on the alternator is twice output. Try and stay below 50% of alternator rated output when you add up Orion(s) and vehicle loads.
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solarnewb answered ·

As for the pd power converter, I already invested in a 12v lithium one before I decided to go the 24v route for the battery bank. A couple questions there…

  1. 3 options: keep the 12v that is currently installed (meant for lead acid), use the 12v that I already have purchased (meant for lithium), return the 12v and get a 24v lithium
  2. (really a sub-question) is it better to run the 12v converter through a 12/24 Orion step up to charge the 24v batteries or run a 24v power converter through a 24/12 Orion step down for running the 12v RV electronics?
  3. (In case of step up 12/24) can you run the 12v from the converter through the same Orion 12/24 as the alternator or should it be separate? Other steps necessary to protect any of the components or the alternator?

I appreciate the insight already and your time. Thank you

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kevgermany avatar image kevgermany ♦♦ commented ·
Simpler the better.

If you go multiplus, you don't need the pd converter as well.

Shore power into multiplus into 24V batteries. Orion(s) 24/12 to feed 12V loads. Orion(s) 12/24 to charge from alternator.

No need to piggyback. Just go straight.


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