mckinleytabor
New Member
- Joined
- Jun 15, 2021
- Messages
- 3
Greetings All,
I’m seeking advice on trouble shooting a battery I am building. I know that the Tesla battery modules have fallen out of DYI favor due to the need for caution with the Li-ion chemistry, but these two Tesla Model S battery modules are what I have to work with at the moment.
I’m have a 13s Daly 200A BMS that I’m trying to use to protect and balance these modules. I also have 2 Stealth EV BMS adapter boards on the modules to give me a cleaner pinout to the individual cell strings.
My issue is that on the Daly BMS my cell string voltages are VERY incorrect. My understanding is that the Stealth EV boards (and indeed the Tesla wireless themselves) will not give me individual string voltages, but rather ADD the voltages up as I move down each string. So string 1 gives me 3.8v, string 2 gives me 7.7v, string 3 gives me 11.4v, etc, etc up to string 12 which is 45.6v. I know that my strings are not balanced, so the numbers here are examples.
That having been said, the Daly BMS shows me 12 strings, but with voltages that do not correspond with my manual measurements. Presuming that I can calculate cell string voltages with subtraction working backwards from the last cell string, my voltages are between 4v at the high end and 3.8 on the low end. (Like I said, I know the pack is out of balance). On the Daly BMS, my cell string voltages are 5v at the high end and 1.5v at the low end, and there isn’t even a clear correlation when comparing my manual readings vs the Daly look for which cells are “high” and which cells are “low”.
Oddly the total voltage on the pack from the BMS DOES match my total voltage as measured manually, and the average cell voltage from the BMS pretty much matches a manual average. (Which makes sense given 12 cell strings and the matching total voltage)
I’m taking my manual readings from the balance lead end that plugs into the BMS so as to verify the lead, Stealth EV board, and all the various connections.
The Daly shuts down after a few seconds, which I am presuming is the unit cutting off in accordance with its safety features as 1.5v and 5v are way outsize the protection limits. I have to apply or disconnect a 48v charger in order the get the BMS back up momentary to work with it. I’ve tried setting my cell string voltage high and low limits up and down to see if it is the protection system shutting down the BMS, but the values I input for those fields are not saving. Values for other fields such as total pack amp hours, amp discharge protection, etc, etc are being saved, just not the “high” and “low” cell voltages, which may be because the values I’m entering as so wrong.
Also at no point am I getting more than 21v out of the battery via the BMS, and that value does not change if the BMS is on or off. Again, I’m guessing this is the protection features at work. When I check the voltage at the battery terminal it is correct for the pack based on the series voltage of the cells.
Am I dealing with a bad BMS, or is there some settings that I’m missing? I’ve gone though all the main settings in the IOS Bluetooth Daly app and they all “look” correct. Are there additional settings worth looking at via USB and the Windows application?
Is this Daly BMS unsuitable for Tesla battery modules given the battery’s accumulating cell string voltages?
Thanks
I’m seeking advice on trouble shooting a battery I am building. I know that the Tesla battery modules have fallen out of DYI favor due to the need for caution with the Li-ion chemistry, but these two Tesla Model S battery modules are what I have to work with at the moment.
I’m have a 13s Daly 200A BMS that I’m trying to use to protect and balance these modules. I also have 2 Stealth EV BMS adapter boards on the modules to give me a cleaner pinout to the individual cell strings.
My issue is that on the Daly BMS my cell string voltages are VERY incorrect. My understanding is that the Stealth EV boards (and indeed the Tesla wireless themselves) will not give me individual string voltages, but rather ADD the voltages up as I move down each string. So string 1 gives me 3.8v, string 2 gives me 7.7v, string 3 gives me 11.4v, etc, etc up to string 12 which is 45.6v. I know that my strings are not balanced, so the numbers here are examples.
That having been said, the Daly BMS shows me 12 strings, but with voltages that do not correspond with my manual measurements. Presuming that I can calculate cell string voltages with subtraction working backwards from the last cell string, my voltages are between 4v at the high end and 3.8 on the low end. (Like I said, I know the pack is out of balance). On the Daly BMS, my cell string voltages are 5v at the high end and 1.5v at the low end, and there isn’t even a clear correlation when comparing my manual readings vs the Daly look for which cells are “high” and which cells are “low”.
Oddly the total voltage on the pack from the BMS DOES match my total voltage as measured manually, and the average cell voltage from the BMS pretty much matches a manual average. (Which makes sense given 12 cell strings and the matching total voltage)
I’m taking my manual readings from the balance lead end that plugs into the BMS so as to verify the lead, Stealth EV board, and all the various connections.
The Daly shuts down after a few seconds, which I am presuming is the unit cutting off in accordance with its safety features as 1.5v and 5v are way outsize the protection limits. I have to apply or disconnect a 48v charger in order the get the BMS back up momentary to work with it. I’ve tried setting my cell string voltage high and low limits up and down to see if it is the protection system shutting down the BMS, but the values I input for those fields are not saving. Values for other fields such as total pack amp hours, amp discharge protection, etc, etc are being saved, just not the “high” and “low” cell voltages, which may be because the values I’m entering as so wrong.
Also at no point am I getting more than 21v out of the battery via the BMS, and that value does not change if the BMS is on or off. Again, I’m guessing this is the protection features at work. When I check the voltage at the battery terminal it is correct for the pack based on the series voltage of the cells.
Am I dealing with a bad BMS, or is there some settings that I’m missing? I’ve gone though all the main settings in the IOS Bluetooth Daly app and they all “look” correct. Are there additional settings worth looking at via USB and the Windows application?
Is this Daly BMS unsuitable for Tesla battery modules given the battery’s accumulating cell string voltages?
Thanks
Last edited: