Tesla S batteries... Do you need a BMS?

[BWilliamson]

So, I've got a local guy here in FL selling solar systems/parts...

I'm still fairly new to this, and I wasn't thinking about these Tesla batteries, but considering the price and the kwh you get.. seems like a great deal.

So I've been researching these batteries, and I understand the need to manage the voltage!

That being said, I asked this guy if he has a BMS that's compatible, and he tells me you don't need one... hmmm

I'm hoping to use a hybrid inverter, so curious if anyone else has used a Tesla S battery without a bms, or should I say replacing the bms to work with an off grid system?

Thanks for any input or advice you might have!

 

[upnorthandpersonal]

Don't. Unless they're LFP, stay away from them. Especially if you're not 100% sure of what you're doing.
There are better, safer alternatives - and prices right now are dropping everywhere. You can get prismatic LFP cells to make your own battery packs, and they're not expensive: 280Ah+ 3.2V cells can be had for around $100.

 

[BentleyJ]

It may be educational to watch a few videos of electric cars on fire. The intensity is truly stunning.
A BMS is absolutely necessary especially with Li-NMC chemistry. Those are the cells that operate at 3.7V nominal.

They are not as safe as LiFePO4 which operate at 3.2V nominal.

 

[Hedges]

It has been done before. By people with some experience, and an aftermarket BMS was available.

Solar house generator I started DIY back in 2000 - My path from Trace to Xantrex (on FLA battery) to XW Pro inverters on Tesla Model S batteries

2 100 ft spools from NNC $197 via PayPal shipping $29 2 100 ft spools from Platt $192 via credit card shipping $23 interesting copper will continue to go higher, get your orders in now.....mmmmm sounds like a GOLD advertisement

diysolarforum.com

 

[BWilliamson]

So, I've got a local guy here in FL selling solar systems/parts...

I'm still fairly new to this, and I wasn't thinking about these Tesla batteries, but considering the price and the kwh you get.. seems like a great deal.

So I've been researching these batteries, and I understand the need to manage the voltage!

That being said, I asked this guy if he has a BMS that's compatible, and he tells me you don't need one... hmmm

I'm hoping to use a hybrid inverter, so curious if anyone else has used a Tesla S battery without a bms, or should I say replacing the bms to work with an off grid system?

Thanks for any input or advice you might have!

I assume AliExpress is the place to go?

 

[upnorthandpersonal]

I assume AliExpress is the place to go?

For cells? No way. Try something like the "18650 battery store" since you're in the US.

 

[Ampster]

I am a big Tesla fan and have owned three Teslas. I considered using Model S packs but to get any usable size pack I would need configure several pairs in series and the price then was not competive with a DIY LFP pack using one good BMS and pairing LF280 cells to get any size pack. I know the fire risk but know my Teslas have a great battery management and cooling system so the risk of the cars in my garage or driveways is minimal. Removing the modules from the temperature and battery monitoring and the cooling system was not worth the risk and was not more cost effective than my DIY pack. In addition the voltage of two modules is still on the low side for most 48 volt charge controllers or AIO inverters.

 

[BWilliamson]

For cells? No way. Try something like the "18650 battery store" since you're in the US.

Thank you!!

 

[BWilliamson]

So I'm still wrestling with this one... the local guy has Telsa 2 batteries for $650 a piece... it's tempting for the kwhs
Would you guys still say no? lol

Sorry, just trying to justify it in my head lol

 

[Ampster]

Assuming the module is 5kWh and you do not anticipate needing more capacity, why no give it a shot? That price is $130/kWh which is competitive.

 

[HighTechLab]

BMS or Be A Mess

 

[Skypower]

So I'm still wrestling with this one... the local guy has Telsa 2 batteries for $650 a piece... it's tempting for the kwhs
Would you guys still say no? lol

Sorry, just trying to justify it in my head lol

Sure as long as where you put it is NOT important to you, just in case it goes up in flames that can’t be put out until the it says so.

 

[AntronX]

the local guy has Telsa 2 batteries for $650 a piece

Dont pay more than $200 per module. At $650 each they are priced at $138/kWh assuming 90% capacity remaining from new (these are used batteries). For $120/kWh you can buy new LFP cells from 18650 store. LFP cells are much safer and can be regularly charged to 100% without degradation unlike Tesla's NCA batteries.

 

[Ampster]

BMS or Be A Mess

In addition they were charging it without any upper limit on voltage. Major user error.

 

[Supervstech]

So I'm still wrestling with this one... the local guy has Telsa 2 batteries for $650 a piece... it's tempting for the kwhs
Would you guys still say no? lol

Sorry, just trying to justify it in my head lol

No way i would buy us3d packs from someone saying bms not needed, over 150 a pack...
Sorry.

 

[upnorthandpersonal]

So I'm still wrestling with this one... the local guy has Telsa 2 batteries for $650 a piece... it's tempting for the kwhs
Would you guys still say no? lol

Sorry, just trying to justify it in my head lol

I would still say no. You can buy new cells LFP cells from sources people mention in this thread, and sleep much better at night. Also, LFP has higher cycle life than NCM, so you have to keep than in mind as well.

 

[Skypower]

I would still say no. You can buy new cells LFP cells from sources people mention in this thread, and sleep much better at night. Also, LFP has higher cycle life than NCM, so you have to keep than in mind as well.

A lot of EV owners are realizing that about battery life. Salesman said “Oh that’s just CYA for worse case scenario, you should see better” yeah right. Or just get new batteries LOL……