Tesla modules: JK BMS or SIMP BMS
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19-01-2024 9:31pm#1
I'm getting some Tesla Model S / X gen 3 battery modules, 5.3kWh each, 6S74P (444 cells) and thinking of building a powerwall with them. I will use some of them in parallel (depending on how many I can get) and 2 in series, for a 48V setup (fully charged 50V, discharged 40V - this is fine with my Sunsynk hybrid inverter)
I plan to replace my CALB setup with these over time. Initially I will need at least 8 of them. Might start with 10. Could later expand to maybe 12, 14 or even 16 if more of these Tesla modules come my way for reasonable money
These modules come with Tesla proprietary BMS slave boards. You can remove these and these tap boards:
And then you can read out temps and cell voltages and connect to a BMS of your choice. I.e. for 8 Tesla modules you could just buy 2 * JK BMS that can handle 24S, roughly €100 each. Plus 8 of those boards, so about €500 in total, but €700 of 10 modules, etc. Has BT and a very good phone app, and with some extra hardware can connect to Home Assistant and control inverter via CAN. Millions of these sold, it's de-facto the world standard for cheap BMS, I know them well myself, lots of support around from others
OR
You can go for a SIMP BMS. This BMS can talk directly to the native Tesla BMS slave boards and a single BMS can handle up to 96 of these Tesla modules. It's not a simple BMS to setup though and it is not cheap, the BMS is €494 + taxes + shipping and taxes and I think the harnasses connecting to the Tesla modules are extra, so about €1000 in total for 10 modules and only slightly more for more modules. Has BT, but no phone app and not sure about Home Assistant, but it can conrol converter via CAN. This seems on paper like an ideal setup, but I doubt many more than 1000 have sold world wide of these, so community support will be tricky. Also rather technical to get it going, and need to make up quite a number of cables yourself if you can't find someone to make them for you. It also needs a Teensy development board. I have no experience of these. And they seem to be sold out everywhere. The manual for the SIMP BMS is here:
SIMP BMS can also control EV on board charging, so it is very suitable for EV conversions using OEM batteries like Teslas, BMW, VW, etc. I don't plan to use it for that, just for home power wall.
BTW my setup is in my garden room / shed so not anywhere near the house. And I do appreciate that LiFePO4 is inherently safe, no matter what happens and lithium ion is not.
What would the good people of Renewable Energies do?
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Looks like they are standard 7 pin and 5 pin JST connectors coming from the ribbon cables on the Tesla gen 3 slab. That is great news, why on earth would anyone still buy those tap boards? Those JST connectors are dirt cheap. Had some lying around from a previous project where I was salvaging Valence 19V batteries out of the Red Arrow (6S LiFePO4)
Onto my spare JK BMS (4S-8S) and balancing. The minimum voltage delta to start balancing is 3mV. It only just about made that 😁
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And the master pair of batteries connected to my main JK BMS. Got all the connections / wires right first go 😂
Got more packs from that original 2015 Model S 70D this evening, have 12 now. Would love to get the remaining 2 packs from a friend of the guy I got them from. We are working on it.
Will install the lot on a heavy duty trolley in the next few days. Have a load of JK BMS on its way to me. Each pair of modules will have its own JK BMS
Post edited by unkel on0 -
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