BigBattery 24v 100ah Model 3 Li-ion "drop in" replacement info

[Argosy]

Hi guys, thanks in advance for helping me out.
Does anyone use the Model3 cell based battery box from BigBattery in a vehicle?
Im trying to figure out what makes it a drop-in lead acid replacement, and if there is concern with charging from alternator.
Not really getting satisfactory answer from their sales guy -- I need100% clarity I wont be risking a $1500 alternator.
Thank you

 

[John Frum]

link please

 

[Argosy]

24V Li-ion Battery Box (BACKORDER) – BigBattery.com

bigbattery.com

 

[John Frum]

Its not lifepo4 so its not a drop in replacement for a lead acid battery.
Its one of the "explody" flavours of lithium, that is as far as I looked.

 

[Argosy]

Dont think lithium model3 cells are considered explody, esp with thermal cutoff and breaker, but thanks

 

[tictag]

Dont think lithium model3 cells are considered explody,

@smoothJoey is referring to the underlying chemistry i.e. NMC (details here), which is very much an 'explody' type of lithium-ion. Will it explode? Of course, not ... with a properly designed BMS, which I am sure these batteries have.

Would I put NMC batteries in my house, my caravan? Absolutely not. I would genuinely prefer to deal with sulphuric acid and the hydrogen off-gassing that comes with lead-acid!

 

[Argosy]

Understand. Lets not derail the thread/questions above.
does anyone have experience with these systems?

 

[Ampster]

- I need100% clarity I wont be risking a $1500 alternator.
Thank you

Is your alternator 24 volts? Compare its charging specs with this battery. What little I know about alternators is you need some kind of intermediary device to protect the diodes when one of these drop in replacement batteries cuts off charging.

 

[Argosy]

Is your alternator 24 volts? Compare its charging specs with this battery. What little I know about alternators is you need some kind of intermediary device to protect the diodes when one of these drop in replacement batteries cuts off charging.

yes 24V and yes I believe so too. Was probably going to go alternator to lead acid, then an auto charge relay to these.

 

[Ampster]

yes 24V and yes I believe so too. Was probably going to go alternator to lead acid, then an auto charge relay to these.

Then the only question is whether the charging voltage of your alternator 24 volt Pb (Lead Acid) is enough to charge this battery. I recently saw a video on one and will look to see if I can find some specs. What is the charging voltage or resting voltage of your 24v Lead Acid battery?

 

[John Frum]

It's appears to be a 7s pack.
4.2 volts per cell max.

 

[Ampster]

I saw your link and and the subsequent post by @smoothJoey and it is 7S so that means at 4.2 volts per cell this will need constant voltage stage of charging at 29.4 to take them all the way to the top which is higher than I would recommend anyway. If I use some very old Lead Acid numbers of 14.4 that is 28.8 volts which is doable for this because that is 4.11 per cell. If that is consistent with your system it should work fine.

When I had NMC cells (used Nissan Leaf modules) in my garage I only charged them to 4.1 volts so you should be safer. I only had one incident with those NMC cells and they became puffed when I left the switch on my GEM golf cart and they totally discharged. It should be noted I did not have a BMS connected or it would have prevented that.