Four years ago I built a EV JR Dragster powered by 12 Milwaukee M28 batteries. I connected 2 six packs batteries in series which gave the controller 56V. The car has run flawless and consistent. I now want to build another dragster for a faster class. My plan is to take 12 Milwaukee M18 9AH batteries. Connect 6 in series for a total of 108V.
Is anyone familiar with the BMS of these batteries that will limit their output when I connect 6 in series?
Before anyone suggest that I build my own battery packs that is not an option. As with the M28 batteries I want to be able to swap the batteries back in forth with power tools. On race day I snap them into connectors on the car and race.
Explain. Limit power or defeat power Limit?
Sorry don’t know what that means. I am just wanting to duplicate the simplicity of the first car. Just connected the battery packs to the controller which powered the motor. Chain drive to the axle and grandson was racing.
The new car is a little more complicated with a Zilla 1k controller and Hairball interface but I just want to know if six batteries in series will deliver 108 Volts or will the BMS in each battery limit the output
Batteries can be connected in series without a theoretical limit.
There should be no problem if they are all the same.
When differences start showing up, voltage will get high or low on a pack and trip bms.
You might have to just try and see how reliable it is.
If it’s more important to win the race than save a battery, find a way to disable bms while racing.
It would have to be done in each pack, and reconnected for charging.
If it worked before it should work with more.
Thank you for your advise. I believe I am going ahead with this project even though I am incapable of disabling the bms.
More worried about parallel branches. Can,t be good if mixed soc. The bms may not be able to save them from high current.
Sorry not familiar what “mixed soc” means. I will try to contact someone at the local university to explain it to me. Thank you for heads up.
Sorry soc = state of charge.
If a low battery is connected to a full battery, current will only be limited by the connecting wires.
I suggest a test to see the affects. Then you won’t be surprised when it happens.