Which BMS for Tesla Model S Battery

[TennesseeSolar]

This is my first time setting up a solar system and I have run into an issue of trying to pick a BMS for a Tesla model S lithium battery. It’s the battery that at full charge is 25.2 V. From what I can understand online I need a 6S BMS. My other components are four, 345W solar panels that will be in parallel, an MPPT 60 amp controller 24V, and 3000 W inverter for 24v to 120v. I think the problem I am having most though is picking out the BMS and understanding what amperage it should be rated. Also my major reason for having the BMS on the battery is not so much for balancing out the battery but as a prevention method to prevent the battery from catching fire. So I am not looking for something like an $$$ BMS but rather something under $100 that will do the job for this. Below is a BMS I found online that might be for something like this? Can someone who has worked with these batteries and attached a BMS please give me some advice on this.

 

[snoobler]

Welcome to the forum.

I'm so happy to see that you're actually pursuing a BMS. Too few bother.

If you haven't procured the battery, you should probably consider DIY LFP. It's cheaper, it's safer, it has a more favorable voltage profile and a higher cycle life. It's literally better in every way. For less than the price of the Model S module, of which you can only use 60% of the total capacity if you want good life out of it (5.3kWh * 0.6 = 3.18kWh), you could build 7kw of battery with 5.6kWh of it usable.

3000W/24V = 125A

If you insist on Tesla:

Tesla Model S & X Battery Module BMS Cell Tap Board | Stealth EV

Shop the Tesla Model S & X Battery Module BMS Cell Tap Board and other battery management systems by Stealth EV. Click here to shop now or learn more...

stealthev.com

The above will allow you to tap into the sensing leads of the module and add a BMS more easily.

 

[TennesseeSolar]

Thanks snoobler.

I looked at the tap board you recommended, but it just appears to be a wire jumper system from the Tesla plug to this jumper. Its not a stand alone BMS like I think I need. Am I seeing this wrong? So do you know of a BMS for this battery? Maybe its my first bad mistake in solar but I have already purchased this battery and it arrived today. So now I am committed to finding a BMS I can use with it that is not too expensive.

 

[snoobler]

I'm sorry. I thought that was a generic interface, but it's specific to Orion. It won't do you any good even as an adapter.

I have NO experience with this type of BMS, but others on this forum speak favorably of the BRAND.

72.0US $ |6s 7s 8s Bms 300a 350a 3.7v Li-ion Battery Protection Board For 6000w High-power Inverter, Solar Energy Storage, 24v Car Start - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

They have a 6S 3.7V 350A BMS for $69.

350A may seem like overkill, BUT the more safety margin you have, the better.

Sadly, it looks like the delivery isn't until 3/8/21.

If this doesn't work for you, you can use it as a template. You need a 6S BMS for the 3.6/3.7V cell chemistry. Given your peak current, I wouldn't consider anything less than 200A.

 

[TennesseeSolar]

This info was a lot of help to point me in the right direction. I have not bought on Aliexpress before but I can give them a try.

I pulled up the spec sheet on this and found the info below. I am new to building a solar system, so I might not understand this right, but do the charge protection voltage and what they call the charge protection release voltage, and also the balanced voltage, look right to you for this tesla lithium battery?

 

[snoobler]

They are acceptable. 4.28V is high, but not danger zone high. The idea is that you set your hardware to operate within your defined limits and the BMS is just sitting there doing nothing unless something goes wrong.

The balanced voltage means that you'll likely never get balancing when you're restricting it to lower limits... which is fine as they're still in limits.

I don't care for the Tesla modules, but they tend to be of very high quality and tend to have exceptional balance. Many run w/o BMS.

The option isn't ideal, but it will keep the battery from burning or exploding if something goes wrong voltage-wise.

 

[schmism]

The option isn't ideal, but it will keep the battery from burning or exploding if something goes wrong voltage-wise.

The third option is something like an all-in-one inverter which monitors the battery voltage and also performs the same shutdown functions at Vloc and Vhoc for your specified voltages. Allowing you to run odd stuff like Tesla or Leaf battery packs without a traditional BMS because it still features protections on the top/bottom voltages.

 

[TennesseeSolar]

Snoobler your advice is very helpful to me on this. Thanks!

Schmism, thanks for the idea on the inverter too. I already ordered this one below and it has over volt shutdown but I am guessing it’s too high, set at 30.5v for my Tesla battery? And again because I am new to solar I might not understand this inverter but I am not even sure how it would shut down my controller charging my battery if it even got up to this high of voltage. I think this would just shut the inverter down.

 

[Jennifer]

Another option is the EVTV BMS system, read Doug's thread at this link, great write up.

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

A little change of plans for me. First I do my taxes and am getting a refund that can help me buy 2 more batteries, and then this happened. My Trace SW4024 inverter has an internal fan and I was startled with a very loud rattle sound coming from the inverter and determined that the FAN was...

diysolarforum.com

Jen

 

[snoobler]

Another option is the EVTV BMS system, read Doug's thread at this link, great write up.

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

A little change of plans for me. First I do my taxes and am getting a refund that can help me buy 2 more batteries, and then this happened. My Trace SW4024 inverter has an internal fan and I was startled with a very loud rattle sound coming from the inverter and determined that the FAN was...

diysolarforum.com

Jen

$2500 BMS for a $1200 battery? Not sure that he wants to spend 2X the price of the battery on a completely over-kill BMS.

 

[TennesseeSolar]

Jen, thanks for the idea on a BMS for my battery. However as snoobler said I don’t think an expensive BMS for my one battery would be a good investment right now. I’m just starting out in solar power and since this is my first adventure in it I am not going overboard at first. At the same time I don’t want to make a mistake in the area that might burn down the battery or my whole system. So that is why I was looking for an inexpensive BMS.

 

[stxShadow]

just have a look for "SimpBMS". It uses the original Tesla electronics on the packs and is able to balance the cells. It is also able to enable / disable different brand of chargers, precharge and shunt trip devices.

Works quite nice for me for some years now.

Jens

 

[Jennifer]

just have a look for "SimpBMS". It uses the original Tesla electronics on the packs and is able to balance the cells. It is also able to enable / disable different brand of chargers, precharge and shunt trip devices.

Works quite nice for me for some years now.

Jens

I thought I had read some where that it has a hard time with parallel strings, being able to plug in additional modules in parallel is part of the EVTV BMS.

Jen

 

[stxShadow]

Works fine for me .... 8 Tesla Model S packs in a 2s4p configuration.
-> you are free with paralleling packs up to 63 packs max.

Jens

 

[bfrank]

Hello Jens,

I am interested in doing something similar but very curious about the other equipment you are using.
Do you use a 48kw inverter? How do you deal with the 1000A?
If I were to get 8 of these modules I figured I'd need to setup 2S in 4 independent circuits from four 12kw inverters.

I'm very new to this and likely just not understanding things correctly.
Struggling to wrap my head around my options at this stage because getting these model S modules at roughly $1k each is very a attractive price point for a 41.6kwh battery.

The model 3 salvage batteries are even moreso but it seems voltage too high to make a reliable inverter practical.

Thanks, Bob

 

[stxShadow]

Hello Jens,

I am interested in doing something similar but very curious about the other equipment you are using.
Do you use a 48kw inverter? How do you deal with the 1000A?
If I were to get 8 of these modules I figured I'd need to setup 2S in 4 independent circuits from four 12kw inverters.

I'm very new to this and likely just not understanding things correctly.
Struggling to wrap my head around my options at this stage because getting these model S modules at roughly $1k each is very a attractive price point for a 41.6kwh battery.

The model 3 salvage batteries are even moreso but it seems voltage too high to make a reliable inverter practical.

Thanks, Bob

Hi Bob,
no ... i am using 48 Volt -> not kW inverters (3xVictron MP2 5000). My consumption is 15kVA max and that is about 300 Amps.
My pack has 2x70qmm for negative and the same for the positive pole. This is quite adequate for the 300 Amps. The pack itself is able to handle 1000 Amps easily .... but you have to rethink about the wire size. Also you will need cooling in that case (if 1000 Amps are drawn for a longer period).

Model 3 packs are not usable be the standard inverters on the market right now (might have changed meanwhile).
Jens