A few questions about the use of DC-AC inverter in the EV for charging

[Sigunas]

Hi, I would like to extend the range of my Nissan Leaf in the winter. I'm thinking about a 8-12 kWh li-ion battery and an inverter in the trunk to charge 6-8 kWh while the EV is parked for a 3 - 4 hours in the area without a public charger. I can buy locally automotive quality li-ion modules from wrecked EV for a reasonable price. The modules are internally 6s2p. I plan to use them connected 2s2p or 2s3p, so 44V 200Ah or 44V 300Ah. I would like to use Victron Multiplus II 48/3000 as my inverter, because in the warm season, I would like to use the same Multiplus at home as an ESS addition to my solar system for power assist, peak shaving and higher self consumption. But I have a few doubts:
1. Is the Multiplus II rugged enough to be used in a car? I mean road bumps, vibration, temperatures outside between -20C and 20C(between -4F to 68F)? Can Multiplus be used in the trunk of the car, lying on the back? On the side? Or must stand upright only?
2. Will Multiplus II 48/3000 be able to charge my Leaf at 10A@230V? Or am I limited to 8A@230V only? According to the specifications, the Multiplus can deliver 3000VA, but only 2000W. What metric should I use for EV charging?
3. Is Multiplus II GX model preferable for ESS? I see listings, where Multiplus II GX costs only 40 eur($44) more than a standard version. On the other hand, if GX version does not add benefits for ESS, I could go for used one not GX version and save more.

Any sugestions are welcome, but I don't want to modify the high voltage battery/lines or change the car
Inverter does not have to be multiplus, or any of the victrons. But I would prefer EU brand, because far east products, that are not from the very bottom, are not that cheap here anymore and considering, that even more expensive ones come without any support or warranty, I dont' see much value in them generally, except maybe some special cases.

 

[billvon]

1. Is the Multiplus II rugged enough to be used in a car? I mean road bumps, vibration, temperatures outside between -20C and 20C(between -4F to 68F)? Can Multiplus be used in the trunk of the car, lying on the back? On the side? Or must stand upright only?
2. Will Multiplus II 48/3000 be able to charge my Leaf at 10A@230V? Or am I limited to 8A@230V only? According to the specifications, the Multiplus can deliver 3000VA, but only 2000W. What metric should I use for EV charging?
3. Is Multiplus II GX model preferable for ESS? I see listings, where Multiplus II GX costs only 40 eur($44) more than a standard version. On the other hand, if GX version does not add benefits for ESS, I could go for used one not GX version and save more.

1) Yes. They are designed for boats and RVs.
2) I assume you have the 230V version of the Multiplus. It will do 2400 watts at 25C, but 1800-2000 watts is a more realistic long term output if it's in a hot car.
3) No opinion there.

 

[timselectric]

I don't see any issues. As long as the multi plus is ok with a 44v battery. (I don't know)

Edit: I'm assuming that you have already figured out battery BMS's.

 

[Sigunas]

I don't see any issues. As long as the multi plus is ok with a 44v battery. (I don't know)

Edit: I'm assuming that you have already figured out battery BMS's.

I found post in victron forum, where someone complains, that 48V Victron can discharge to 38V only in standalone mode, but only to the 40.6V in ESS mode. But I think, even 40.6V will be good for me and will leave safety margin to not to discharge too much.
I plan to charge to 4V/cell only and to use active balancer for cells. 48V Victron can pump only 35A to the battery. That's less than 0.2C for 200Ah battery, so very very light use for automotive cells. Do I absolutely need additional BMS?

 

[yabert]

I plan to charge to 4V/cell only and to use active balancer for cells. Do I absolutely need additional BMS?

Don't...
Don't add active balancer who, if they fail, can caused serious problem to those good quality used EV cells.
About BMS you have two choice: You are the BMS or you buy a BMS.
After drove thousand miles in my DIY EV without BMS I would say... buy a BMS.
200$ contactor BMS is a safe bet for your Frankenstein range extender.

 

[timselectric]

I found post in victron forum, where someone complains, that 48V Victron can discharge to 38V only in standalone mode, but only to the 40.6V in ESS mode. But I think, even 40.6V will be good for me and will leave safety margin to not to discharge too much.

It will run fine.
I was referring to charging ability. Not sure how low the charging voltage can be set.

I plan to charge to 4V/cell only and to use active balancer for cells. Do I absolutely need additional BMS?

I personally would not run any type of lithium battery without a BMS. (For safety)
But, it's up to you.

 

[Sigunas]

Don't...
Don't add active balancer who, if they fail, can caused serious problem to those good quality used EV cells.
About BMS you have two choice: You are the BMS or you buy a BMS.
After drove thousand miles in my DIY EV without BMS I would say... buy a BMS.
200$ contactor BMS is a safe bet for your Frankenstein range extender.

Scrapyard has a few contactors from EV's to choose from.
What BMS would you use for 12S 200Ah battery? Or do you mean contactors "as the BMS"?

 

[yabert]

What BMS would you use for 12S 200Ah battery?

I use a JBD contactor smart BMS in my house battery.
I prefer contactor over mosfet, but It's a personal choice.

About your project, do you think about rebuilding your Leaf battery? It's was a plan I had few years ago. Take a 24 kWh Leaf and swap battery module to have around 40 kWh.
Example, if you can find 16 battery modules from an Ionic 5 / EV6 (buy a whole pack and sell the other 16 modules) you can rebuild your battery and have 38 kWh.
Not bat for 368 lbs of tiny module.
There is many BMS wires to manage, but when correctly connected at cells level, the Leaf will not see any problem to be power by 38 kWh instead of 24 kWh.
The other choice is to swap the battery by a Leaf 40 or 62 kWh battery. You will find video/info online.

 

[Sigunas]

I use a JBD contactor smart BMS in my house battery.
I prefer contactor over mosfet, but It's a personal choice.

About your project, do you think about rebuilding your Leaf battery? It's was a plan I had few years ago. Take a 24 kWh Leaf and swap battery module to have around 40 kWh.
Example, if you can find 16 battery modules from an Ionic 5 / EV6 (buy a whole pack and sell the other 16 modules) you can rebuild your battery and have 38 kWh.
Not bat for 368 lbs of tiny module.
There is many BMS wires to manage, but when correctly connected at cells level, the Leaf will not see any problem to be power by 38 kWh instead of 24 kWh.
The other choice is to swap the battery by a Leaf 40 or 62 kWh battery. You will find video/info online.

Thanks. I was just planning to buy 4-6 EV6 modules for this project. I had thought about replacing the leaf's batteries completely, but considered that more of a theoretical possibility when the current battery drops to 60% SOH or less. Now I'm still at ~78% SOH (17kWh) and that's enough for 90% of the time, and the rest we can swap and use an ICE car for a longer trip. Therefore, I didn't really want to get inside the HV battery and hoped to extend the distance in a less invasive way. But it is probably worth looking more into how to fit EV6 modules instead of the original ones.

 

[yabert]

But it is probably worth looking more into how to fit EV6 modules instead of the original ones.

If that can inspire you
44 x 35 x only 4.5'' thick.