Charging and Load Testing Tesla Model 3, 25S modules

[BrianP]

I have 4 Tesla Model 3 battery modules, 2, 23s and 2, 25s modules, all from the same, low mileage 2018 Model 3.

I am liquidating them as part of the assets of a business which has lost funding.
The static voltages look ballpark good at 88.7V, 87.0V, 82.5V and 91.0V.
I would like to charge and load test each one separately.
I suspect that 1 or 2 of these with the right charger/inverter/bms could be an excellent choice for a coach or for solar in general.

Is there a reputable electronic shop in the Central Texas area that could perform the charge and load tests?
Charger recommendations? Most I have found are for LiFePO4.
YZPOWER 100.8V 8A Li-ion Lipo Chargers Lithium Battery Charger for 24S 87.7V Li-ion Battery

 

[snoobler]

Welcome to the forum.

1S = 3.0-4.2V operating range (probably can go as low as 2.5V, but not worth the bother)

23S = 69 - 96.6V
25S = 75 - 105V

Those voltages are not encouraging. the 2 23S modules should be nearly identical to each other, and the 25S modules should be nearly identical to each other. If you can take cell measurements, hopefully you can confirm that all 23 or 25 cells within a module are essentially identical to each other, then there is hope.

To properly charge and load them you need to monitor all 23-25 cells. If ONE of the cells go too far out of limits, the whole thing is ruined.

Unlikely you're going to find anyone in the U.S., let alone Central Texas that will test them at all. Test at a price that won't make you crap your pants? Probably not.

The charger is correct for 24S; however, you have 23 and 25S. Would put a partial charge on the 25S at least, but it would destroy the 23S if you left it to its own devices.

 

[BrianP]

The modules appear to be not well matched so they would probably not work together well in parallel. But each module has the energy of
~2.5 model S modules so could be used individually.

I am not sure how to measure each 46p bank (Platoon?). I need to figure out what the pinout map is.

And, it is fairly common to have hybrid energy banks with LiPo, LiFePO4, LiTO and even lead acid in different legs.
It should be possible to have mismatched 23S banks and 25S banks managed with the right hybrid BMS (just not in parallel).

I am wondering whether a bit of surgery could be done to lobotomize the 25th 46p Platoon and short around it to convert it to a 24s46p to work on a standard BMS expecting 24 units. The 25th should just discharge harmlessly over time.

Good thing this is a DIY forum so we don't have to do things properly!

I wonder how a BMS-24 would react to finding only 23 units?

I would not want to sell these without knowing their condition. If they test bad, no biggie.

If 1 or 2 survive and test good, I'm in the black! All 4 might be good to excellent. 1 or 2 of these would be perfect in an RV coach!

Some adventurous DIY enthusiast is going to want to see if they can make these things fly. I have sold many model S modules for solar and these are better in every respect. There are going to be a lot more of them hitting the market, every time a Model 3 crashes.

Inventing methods to harness them efficiently will be profitable.

 

[snoobler]

If the cells are paralleled, you only need to measure one.

They are not better in every respect. The individual cells may indeed be very superior, but that is the ONLY way they are better. I would not regard batteries with these nominal voltages to be of any interest to the vast majority of RV owners. I'm a DIY battery freak, who has gobs of capacity of different cell types and testing equipment sitting within 20' of me at the moment, but I would never consider using these unless they were given to me, and I had a fantasy project in the works.

IMHO, your success with 6S Tesla modules is not predictive for these modules. Those modules are massive and even fitting them conveniently in an RV is hard to imagine. I have a Class A motorhome and a 5th wheel, and neither have suitable storage.

Jack was able to establish communication with the CAN bus and get cell voltages reported.

 

[BrianP]

Thanks for that link to the late, great Jack Richard of EVTV. He said that he would have liked the Tesla 3 batteries if only he could find a good inverter for them. The chinese sdex models he had were too heavy, costly, non-repairable and had unknown reliability. The date of the video was Apr 12, 2020.
Enter the Sigineer 96V 15 kW Pure Sine for Tesla Model 3 released in June. The brand is high quality and reliable. There is an option to get a Solar Charger built in. This gets you pretty close to a full system.

Sigineer: "Our inverters don’t interface with the proprietary Tesla battery pack BMS, users have to jailbreak it or use a 3rd party BMS and set the battery voltage range to suit our inverter." Probably beyond the capabilities most shade tree DIY'ers.

While the entire 4-pack might not fit in a Class A coach, at ~6 feet long, 1 or 2 modules should fit in the lower storage compartments.

Since Sigineer is officially supporting the Model 3 Modules (not the full 4-pack), this is definitely a viable, Solar solution.

 

[Csecrist12]

I have 4 packs of the Tesla Model 3 (16 total modules) that I am currently going through as we as using at least 1 whole pack for an HV hybrid setup using either the Megarevo unit or the GoodWe units as both have inputs of 400V from the battery input. I will also be using an Orion BMS to monitor and communicate through CAN directly to the inverter. The batteries will be in it's on the case in a room in a detached shop that will have all fire and electrical safety regulations you can think of.

As far as your batteries go, simply check each voltage on each cell. If any are low, use a Power Supply Unit and charge them per brick to get them to match. You can be your own BMS but have to monitor them regularly. Not as scary as you may think to be honest. Once you get them identical (May take you quite a while depending upon your PSU) but then you can test it with a constant load (IE. space heater with no thermostat) as it would be a constant load. Get them lowered by a certain amount of power then charge them back up and see what happens. It's all about monitoring and this will help your SOH of the batteries.

They're incredible batteries and with a lower pull from being used on a house setup versus what they see in a car are manageable.