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Sanity check - Chevy Bolt 12v to DIY lithium bank

lisalizajohn

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End goal here is to power a (150w-600w) Midea 8k BTU inverter AC, cheap (25-100w) mini fridge, some lights, and some USB charging hubs in a small homebuilt trailer. Trailer will be used exclusively for short getaways - usually in campgrounds with flaky shore power, but occasionally in dry campgrounds or boondocking where the Bolt will be the primary power source. I am not interested in attempting to pull power directly from the big DC battery - that is really intriguing but really scary.

The Bolt has a 130a DC-DC converter to keep its 12v battery charged, owners have established that (using an inverter with questionable efficiency) you can pull ~1000w from it consistently without draining the 12v. I'd like to pull as close to this as I can, since the vehicle must be on to activate the DC-DC converter, and I don't like the idea of sleeping or leaving camp with the vehicle in a drivable state. Refilling the battery in a handful of hours would be ideal.

The battery plan is a DIY setup with 304ah EVE cells and a JK BMS. I would prefer 24v, both for future solar considerations and to limit the distance required for expensive high gauge wiring, but I'm not dead set on it. Either way, I'm planning for ~7kwh of battery storage.

For an inverter, I'm pretty sold on the Samlex EVO line - AC input for shore power, AC input for a (future) generator with auto start, and DC input (up to 50a) for 'alternator' and/or solar. Incredible surge capacity, though the AC doesn't surge and the fridge works on my 1500w inverter without issues. Victron Multiplus (with that attractive Power Assist) is also a possibility, though I really like the being able to add a generator plan C easily, and the Multiplus units are much more expensive than the 1200w Samlex I'll probably go with.

If I were willing to go 12v, there are a number of options - Renogy's 50a DC-DC charger with MPPT is attractive, as is the similar KISAE 1250, or any number of other DC-DC charger options without built-in solar input. For 24v, though, I haven't come up with anything suitable other than the KISAE 2430, which I'd have to pair with a step up converter. Victron would require me to parallel multiple 12v->24v converters, or I could go with something like the DayGreen 12v-28v converter - probably the 40a model to max out what I can feed the KISAE. I have a suspicion I could probably do without the KISAE and just let the Samlex limit the current on the 40a 28v output from the DayGreen from the Bolt, but I'm not totally sure it actually limits the current through the DC input - and regardless, I want to be able to add solar when I replenish my toy fund, and I'd prefer to be nice to my battery.

This seems almost too simple - am I crazy?

TL;DR: Samlex EVO 1200w/2200w 24v model, with shore power into AC1, autostart generator into AC2, and KISAE 2430 into DC input. KISAE 2430 fed by Chevy Bolt 12v (w/ 100a fuse) with DayGreen 40a 12v->28v converter, giving me ~800w from the vehicle now and leaving open the option for 30a of solar down the road. DIY 304ah 24v EVE setup with JK BMS. What am I missing?
 
I can confirm you that we pull 1000w from the Chevy Bolt DC-DC (our Vanabolt) for complet night without problem.
The van was energised over night and we use a 120Vac heater to keep us warm.
The DC-DC is always activate when plug to J1772 gun (charge station), so no need to power the car ON to have the DC-DC power.
Funny fact, I was able to connect the charge station to the Van 12V inverter. That manner, the Van charge itself with his own energy ?

If you look at a device to charge 24V battery from 12V, you should look at the really useful RC charger like ISDT Q8 max or Icharger S6.
Those little chargers are fully adjustable, can balance cells and charge many batteries types.
With a simple power supply you can use them from 120Vac too.
 
Oh, man, I'm going to have to go through your post history! If I can activate the Bolt's DC-DC with a super slow charge (straight out of its output) I'm golden! The losses at each conversion will probably end up kind of ugly, but no higher than the overhead of having the car running, I'm sure! Thank you!!

I'm looking into the RC chargers, too - I had no idea there were cheap RC devices capable of feeding 1000w! You may have completely changed my game plan - I can't thank you enough.
 
If I can activate the Bolt's DC-DC with a super slow charge (straight out of its output) I'm golden!
You can. At first the EVSE will not like to be connect to an inverter and it will refuse to charge our EV.
But when you connect ground to neutral the EVSE will don't see anything strange and will allow the current to flow from inverter (120Vac) to EV charger (360Vdc) to DC-DC (12Vdc) to... the inverter ?
 
The Bolt has a 130a DC-DC converter to keep its 12v battery charged...the vehicle must be on to activate the DC-DC converter.
One would think the DC-DC converter would be on all the time to keep the 12v battery charged, otherwise will lose voltage over time if the Bolt is not driven. Will have to test on my Son's Bolt.
 

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