which BMS

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markH   100 µW

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which BMS

Post by markH » 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.

john61ct   1.21 GW

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Re: which BMS

Post by john61ct » Jan 14 2020 7:19am


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.


markH   100 µW

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Re: which BMS

Post by markH » Jan 14 2020 12:50pm

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.

john61ct   1.21 GW

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Re: which BMS

Post by john61ct » Jan 14 2020 12:54pm

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.

markH   100 µW

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Re: which BMS

Post by markH » Jan 14 2020 1:30pm

thank you John 61ct :thumb:

markz   100 GW

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Re: which BMS

Post by markz » Jan 14 2020 8:58pm

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.

goatman   10 kW

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Re: which BMS

Post by goatman » Jan 15 2020 3:22am

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.

markH   100 µW

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Re: which BMS

Post by markH » Jan 15 2020 8:40am

" 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

john61ct   1.21 GW

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Re: which BMS

Post by john61ct » Jan 15 2020 8:51am


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.




goatman   10 kW

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Re: which BMS

Post by goatman » 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

markH   100 µW

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Re: which BMS

Post by markH » Jan 15 2020 8:46pm

goatman, it has a 40amp fuse :thumb:

markH   100 µW

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Re: which BMS

Post by markH » 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?

john61ct   1.21 GW

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Re: which BMS

Post by john61ct » Jan 16 2020 11:25am

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

goatman   10 kW

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Re: which BMS

Post by goatman » Jan 16 2020 1:02pm

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.

markH   100 µW

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Joined: Jan 14 2020 6:53am

Re: which BMS

Post by markH » Jan 17 2020 1:55am

"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

john61ct   1.21 GW

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Joined: Dec 18 2018 2:06pm

Re: which BMS

Post by john61ct » Jan 17 2020 4:19pm

I feel so cheap

8-D

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