Page 1 of 1

which BMS

Posted: Jan 14 2020 7:10am
by markH
All I need to know does it matter if I pick a BMS 30A or 50A with the 60V 20ah lithium battery pack I need to replace the original battery of my 2000W scooter. I'm a noob to electronics and just don't want to damage the controller that is rated DC 60V, Off Voltage
51V, Power 2000W. Thank you.

Re: which BMS

Posted: Jan 14 2020 7:19am
by john61ct

markH wrote:All I need to know does it matter if I pick a BMS 30A or 50A with the 60V 20ah lithium battery pack I need to replace the original battery of my 2000W scooter. I'm a noob to electronics and just don't want to damage the controller that is rated DC 60V, Off Voltage
51V, Power 2000W. Thank you.
You really should actually measure the peak battery amps drawn by the drivetrain and make sure the BMS is rated say 20-30% higher.

In theory 2000W ÷ (lowest voltage 42V?)

I'd go to 70-80A but that's conservative.


Re: which BMS

Posted: Jan 14 2020 12:50pm
by markH
john61ct

I'm not buying the battery separate from the BMS. The batteries I'm interested in offer either 30 A or 50 A BMS' built-in already. I'm concerned whether either will protect my system and if the higher is the better choice.

Re: which BMS

Posted: Jan 14 2020 12:54pm
by john61ct
Then if not possible to actually measure your max amps draw,

I'd buy the bigger one.

And then tune your controller settings (or CAv3 add-on) so your drivetrain **can't** draw over say 43A.

In which case you may not be getting the max possible performance from the drivetrain, the pack being the limiting factor.

Re: which BMS

Posted: Jan 14 2020 1:30pm
by markH
thank you John 61ct :thumb:

Re: which BMS

Posted: Jan 14 2020 8:58pm
by markz
The batteries you are looking at should be from reputable builders/sellers like em3ev and grintech, because the basement dwellers flinging batteries to fleabay/ali's are not worth a second even looking at.

Re: which BMS

Posted: Jan 15 2020 3:22am
by goatman
markH wrote:
Jan 14 2020 7:10am
All I need to know does it matter if I pick a BMS 30A or 50A with the 60V 20ah lithium battery pack I need to replace the original battery of my 2000W scooter. I'm a noob to electronics and just don't want to damage the controller that is rated DC 60V, Off Voltage
51V, Power 2000W. Thank you.
the voltages youre giving makes me think your scooter had SLA batteries, 5 sealed lead acid in series. the lvc of controller is 51v.
is your controller 33amp?

if that's the case and you are upgrading to lithium. is the 60v 20ah battery a 16s/67.2v battery, 15s/63v battery, 14s/58.8v battery

16s could be too much voltage for your controller but lvc of 51v is fine and you have 16 usable volts
15s you get 12 usable volts. 63v with a 51v lvc
14s you get 7.8 usable volts, 58.8v with a 51v lvc. no range 6km?

if your controller was made to be used with sealed lead batteries you may not get the useable 20ah of the new battery.

id go 50 amp bms depending on what 18650 cells are used. the continuous amp rating of the cell multiply by the number of p the pack is. a 5amp cell in a 6p pack. the pack can only put out 30amps, 50 amp bms wont protect your battery pack.

Re: which BMS

Posted: Jan 15 2020 8:40am
by markH
" Goatman wrote

the voltages youre giving makes me think your scooter had SLA batteries, 5 sealed lead acid in series. the lvc of controller is 51v.
is your controller 33amp?

no, the original batteries are 60V lithiums, they originally got 25> miles range and after only 1800 miles of modest speed rides are down to under 7 miles riding on eco mode at very low speeds ... I thought they were 20ah, but may have been 15ah, and the seller doesn't sell them or the scooter after one year, and doesn't respond to emails regarding specs

Re: which BMS

Posted: Jan 15 2020 8:51am
by john61ct

markH wrote: the original batteries are 60V lithiums
Does not mean anything precise.

Best to figure out what chemistry and how many cells in series.

If you charge to 100% Full, then let them sit isolated an hour, what is the pack's exact voltage?

Then remove a tiny bit of "surface charge", say 1Ah and after a few minutes, measure again.




Re: which BMS

Posted: Jan 15 2020 2:34pm
by goatman
the bms is for the battery,not the controller or motor. find out wich 18650 cell is being used and google it to see what its max continuous amp rate is, multiply that by the number of p and that's the maximum amp rating you want for your bms. if that number is 60amps get the 50 amp bms.

find out the amp rating of your controller. you don't want a 30 amp bms protected battery for a 50 amp controller.

you can always look at the fuse that's between the battery and controller to see what kind of amps your bms and battery needs to be

Re: which BMS

Posted: Jan 15 2020 8:46pm
by markH
goatman, it has a 40amp fuse :thumb:

Re: which BMS

Posted: Jan 16 2020 8:11am
by markH
goatman wrote:
Jan 15 2020 2:34pm
the bms is for the battery,not the controller or motor. find out wich 18650 cell is being used and google it to see what its max continuous amp rate is, multiply that by the number of p and that's the maximum amp rating you want for your bms. if that number is 60amps get the 50 amp bms.

find out the amp rating of your controller. you don't want a 30 amp bms protected battery for a 50 amp controller.

you can always look at the fuse that's between the battery and controller to see what kind of amps your bms and battery needs to be
[/quote

with a 40A fuse what does that tell you?

Re: which BMS

Posted: Jan 16 2020 11:25am
by john61ct
The 50A battery will get full power to your drivetrain,

and last a lot longer if you limit the draw to 35A or lower

which is the limit implied by that 40A fuse.

If you get the 30A battery, you will need to limit the draw down to 25-26A, and likely will not get the full power the drivetrain could produce

Re: which BMS

Posted: Jan 16 2020 1:02pm
by goatman
markH wrote:
Jan 16 2020 8:11am
goatman wrote:
Jan 15 2020 2:34pm
the bms is for the battery,not the controller or motor. find out wich 18650 cell is being used and google it to see what its max continuous amp rate is, multiply that by the number of p and that's the maximum amp rating you want for your bms. if that number is 60amps get the 50 amp bms.

find out the amp rating of your controller. you don't want a 30 amp bms protected battery for a 50 amp controller.

you can always look at the fuse that's between the battery and controller to see what kind of amps your bms and battery needs to be
[/quote

with a 40A fuse what does that tell you?
40 amp fuse tells me I want a battery that can deliver atleast 40 amps.

I know, mark hasn't said what his 18650 cells are and we don't know how many p the pack is.we asked, all he wanted to know was whether to get a 30 or 50 amp bms.

40 amp fuse, 50 amp bms.

Re: which BMS

Posted: Jan 17 2020 1:55am
by markH
"with a 40A fuse what does that tell you?
[/quote]

40 amp fuse tells me I want a battery that can deliver atleast 40 amps.

I know, mark hasn't said what his 18650 cells are and we don't know how many p the pack is.we asked, all he wanted to know was whether to get a 30 or 50 amp bms.

40 amp fuse, 50 amp bms. "
[/quote]

That's all I wanted to know and thank you all very much :D

Re: which BMS

Posted: Jan 17 2020 4:19pm
by john61ct
I feel so cheap

8-D