Libre Solar Community Forum

CC for 24v Tesla 2170 powerwall pack

G’Day Guys
Just found this site and I’m blown away. I’m hoping this is exactly what I’m looking for.
I searched here but cannot find the string → Tesla 21700 or Tesla 2170
I have been trying to get a charge controller for Tesla batteries 7 Serial 2 Parallel (7s2p) 24 Volt ( Max. 29 ) - 14 ‘power wall’ - 11Ah 260Wh
So I can charge 14 cells via a solar panel on my 4x4.
I have 40+ years exp. soft. eng. of process control systems so not scared to get my hands dirty, just need someone to point me in right direction :slight_smile:

Hi NG,

Do the Tesla packs with 2170 cells really have 7 cells in series? I only know the Model S battery where each module has 6 cells in series.

In any case, the Libre Solar MPPT firmware can be adjusted to any number of cells in series as long as the maximum voltage of the hardware is not exceeded. For 7s the new MPPT 2420 HC would be ideal. As stated in the issues, the inductor choice needs to be double-checked for 24V systems for max. current. Other than that it’s working fine. Unfortunately, the STM32G431 MCU is not available at the moment, so the further development is a bit stuck.

G’Day MJ

Thanks for the very prompt reply :slight_smile:

Yes 7, see this ebay Ad. to see what I have purchased → 7S 24V 1P 2P Battery Box 20A 40A 60A BMS 21700 Battery Case Protection Board HAU | eBay

I’m such a newbie I don’t even know how do I buy a MPPT 2420 HC ?

BTW - I do no have a BMS version of the powerwall, this is why I need a ‘smart’ charger that is LI aware


At the moment you cannot buy the MPPT 2420 HC anywhere, you have to build it yourself.

And you will definitely need a BMS in addition to the charge controller, otherwise you risk overcharging single cells with potentially catastrophic results.

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G’Day Martin

Thanks 4 your reply :slight_smile:

Do I buy a kit or individual parts or ???

I’m building portable power packs 4 my 4x4 trips, I power fridges, compressor. LED, etc. so I’m using powerwalls and I’ve been charging the cells from the mains as I have many packs.

So I don’t need a BMS, the intelligence is in the appliance eg. fridge

But, I want to charge a 14x21700 24V ( 29.4Max ) powerwall via solar panels and I’m getting so confused no one seems to know any way to do this.

I have tried 4xMPPT solar controllers and they didn’t work even with the Lithium Ion setting !!!

Would really like to find someone that knows how to do this

Yes, you have to buy individual parts and the PCB yourself. There is no kit available at the moment.

Does the charger also balance the cells?

G’Day MJ

For discharge I use the smarts in the appliance like fridge. This works really well, the 2 x fridges I use have always cut off on low volts.

This is very much DIY ATM, I’m not going to sell any of this tech.

Short answer, No

It sometimes takes me weeks to charge up the 100+ 21700 cells via mains before I go on a trip to the ‘outback’ :slight_smile:

Here is a link to the charger

LiitoKala Lii-PD4 26650 21700 4-slot lithium battery LCD charger

I have bought new cells and I remove them from the powerwall and charge them in these chargers like I said above.

Not concerned with balancing as I write down the details of each cell after charging and enter these details into a desktop app I have created to monitor the cells.

I’m hoping that eventually the charger will be monitored via bluetooth or wireless when I get time to buy a ‘communication charger’ - future project.

As the sun is pretty much always shining in Australia I want to be able to charge my powerwall packs by solar when I’m on a trip away.

This is the obvious next step, but I need help finding a solar charge controller that will charge my 24V packs ???