Amen to that!
and high voltage cut off too no? that seems the most important for not blowing up.
looking at the details on this 80amp one from battery support Iām going to annotate it and hope someone can add their own or tell me if iām wrong or right.
Technical Parameters: Balanced current: 60mA (VCELL = 3.90V when) starts balancing when a cell over 3.9 with just 60ma Balanced for: 4.20 Ā± 0.05 V Over-charged Protection: 4.2 Ā± 0.05 V will shut the charging off to all cells if one hits 4.2 Over-charged Release: 4.05 Ā± 0.05 V ?waits till the high cell all the way down to 4.05?? Over-discharged Protection: 2.9 Ā± 0.05 V shuts down output of all cells at 2.9 Over-charged delay: 5mS whats this 5secs? till it shuts off? Over-current Protecton: 80 A shuts down power out of battery if over 80 done? Supports Max. Continuing Discharge Current: 80A ?but somehow will do the 80 continuous? Static power consumption: less than 200uA Short-circuit protection function: disconnect the load from the recovery.
Dimension: 200mm * 110mm * 20mm (LWT) - with Radiating Board
The main functions: Over-charged, Over-discharged protection, short circuit protection, over-current protection, with Balancing function.
high voltage cut off is usually taken care of by your supply. in the case of a 12S pack you use a 50.4V supply. 4.2V x 12S = 50.4V therefore your supply will not allow you to charge more than 4.2V per cell because it physically canāt. the āprotectionā will probably shut down if you hook up a supply that too high voltage. if one cell reaches 4.2V before the others while charging, a bleed resistor is switched across that cell (presumably @ 60mA ) this happens apparently within 5 milliseconds.
the 80A current refers only to the switching component and is related to the amount of FETs and what they can handle.
For what its worth the only difference between a 20A BMS and a 100A BMS is the amount of switching FETs and what they can handle.
80A continuous is a bit of a lie if the over current is set at 80A LOL
1 Like
my bulk supply will definitely charge individual unbalanced cells higher than 4.2 with my bulk supply at 50v. I understood that this bms would start balancing at 3.9. Otherwise, which Iāve often see, where the balance function starts at 4.2ā¦ that makes no sense if the pack will have a safety over-voltage per cell at 4.2 as well. no time to balance. but labels seem to say anything.
thatās because you bleed resistor canāt discharge faster that you can charge.
iām saying the supply doesnāt do anything other than feed 50v regardless of what the individual cells at. no safety feature there to protect a cell and thatās what the supposed point of the bms is.
am I right in thinking that the whole pack will stop charging or discharging if any cell hits the low voltage cut off or the high?
how about those many bms that state 4.2 is when it starts to balanceā¦and also when the high voltage cutoff is? or maybe itās just more empty writing.
thatās disgusting
Iāll try to explain it tonight if I have time
1 Like
oo and while youre at it can you tell me if I could modify this
to have greater discharge ability by adding bulbs or different resistors. be cool looking if it had tiny bulbs that I could see through my enclosure. and Iād also like to reduce the voltage it starts to balance.
ive got a couple 13s versions coming in the mail and assume Iāll be about to do 12s