Bms for 20s 35ah molicel 45b pack

[constantly.constance]

Hello im very new at this so please forgive my blatant ignorance on stuff like this i am basically a person that can more so copy what i see someone do so diving into battery building a lil blind i know im playing with fire but am trying to get a understanding of things the best i can and this is a learning experince

No for my question i am about to start building a 72v 20s 8p battery for my electric scooter i will be using molicel p45b cells they are supposed to be some of the best cells i can use for my aplication
They have 4500mah and a maximum discharge raiting of 45amps i will be using the copper nickel sandwich weld option and i will be running 2 spintend single ubox vesc 20s 150a controllers i plan on running them at 50 amps but making a second profile that is closer to 100amps should be possible i see others doing it with lesser batteries and lesser controlers

anyways the point to my question i was looking at the daily bms systems the look good to the untrained eye anyway and they have bluetooth utart and canbus hookups my question is they come with a number of peak amps capability what kinda amps do i need i was thinking its probably like the 200 amp version twice the max of what i would ask from the system but just a guess if anyone has a recomendation please gemi you 2cents even if its a verbal beating lol

And if possible a easy to understand explanation would be great or a simple math equation for this kinda thing or somthing

Thanks
Constance

 

[MorbidlyObeseKoala]

I think you are on the right path. Doubling your max continuous amps might be a little overkill BUT so often these things are advertised with a much higher rating than they can actually handle for realistic riding situations you will definitely want some headroom. Additionally getting something that has bluetooth or programmable limits that you can view and change will help when you have to troubleshoot something. So I think your choice is fine if it fits your budget.

Some other brands other users seem to recommend are ANT and JBT which also have some bluetooth or display screen options. I have seen some battery builds from small companies offering similar batteries to yours with a 300 amp rated ANT bms but for larger builds.

One build suggestion I have is to make a way for you to completely remove/isolate the BMS without having to completely disassemble the entire battery.
A few reasons for this option:
1. if you get a bad BMS, fairly easy to replace it when the replacement arrives
2. you can easily take it out of the troubleshooting phase if you can remove it (as long as you are careful with the limits of your cells and don't do something foolish). It can take a lot of testing and voltage readings to determine the cause of something acting weird so any time you can remove a variable, it helps speed up the process.
3. if you intend to store the battery for an extended time period (a month or 2 without cycling it) you can document your pack and your parallel group voltages and be absolutely certain the BMS isn't causing any drain to the cells. When you come back to it, you can see how much it discharged by itself and determine if that is acceptable or if there are issues at the cell level that need to be dealt with
4. if you use that monster battery for a different build with a higher amp draw, you can put in a beefier BMS to handle it and leave the cell connections in tact (assuming your discharge wires are big enough to handle it)

good luck, have fun, be careful with all that power especially when building the pack. You don't want to start a fire with that amount of energy close to anything living or valuable.

 

[constantly.constance]

Thanks yeah im going with the ant one actually the daily needed a extra component for active balancing and also cause a very reputable company that does batteries for scooters and is well known for high performance parts and stuff thats what they are using and yeah im going with 200 as the max my controller handles is 150amps and the ant one can handle bursts of 300 amps it said so that should give me plenty of head way for any type of surge or any thing like that im figuring im going to check with the company before i purchase im thinking they can offer a little guidance thank you for your imput its much appreciated

 

[ScrapRider]

Look at JK active balance BMS . They have a 200 amp 20s version with 2amps of active balance current. I have tried them all and JK is finally the all in one solution I have been waiting for. Daly totally missed the boat on active balancing and it’s a joke.
JK all the way, only issue is 200 amps is the limit currently. Hopefully they introduce a higher current lineup.