Adding cells to a pack

costad

10 mW
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Sep 11, 2014
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I have bought a 52V dual motor electric scooter, which has a 21700 24Ah 14s5p pack in it, and I want to upgrade that battery to 60V, a 16s5p, and ofc buy a new BMS to get some extra top speed.
I am just not sure whether or not the controllers or motors can handle it. The controllers are rated 40V and 25A each, and the motors are 1200 watt each.

Can you tell me how many amps my new BMS should be on? I guess it's Watt (2400) / Volt (60), so 40 Amp, but not sure about that though.
 

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A few thoughts:

The BMS should be able to handle more amps then the controller can draw and charger can deliver. How many more is not too important however, 50a BMS aren't super expensive. Regulate the cell discharge and charge with your controller and charger.

The controller can only take what the capacitors and MOSFETs can handle. If you don't have a data sheet or specs on your controller, you will need to open it up and see how many volts the caps are rated for and notate the number on your fets and research how many volts they can handle.

As for mixing new and old battery's it is not recommended. Your old cells have formed some internal resistance depending on age and use. When you mix old and new cells, the new cells get stressed trying to cover for the reduced output of the old cells.

Anyway that's a start.
 
Open up your controller look inside do the Caps say 63 volts. If so the answer is no. You may have 75 v caps or 100 volt if so you can get away with it. by guest if you have 63 volt caps in that controller.
 
Thanks, for the tips.

As for mixing old and new cells, it's brand new. I just fell for their BS of up to 70 km/h commercials, when in reality it's about 45km/h. I am just looking for like 8-10 km/h increase with a bigger battery.

Looks like the capasitors says 80V, and the Mosfets are called IRFB3077, which seems like is 75V, according to this sheet?
https://www.infineon.com/dgdl/irfb3077pbf.pdf?fileId=5546d462533600a4015356153f0d1def
 

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You are thinking of adding a 2s pack of 24ah ? For 16s 68volts fully charged ?Or you might look at putting some solder on the shunts for more amps if your battery and BMS can handle more amps.
 
Yeah, I am looking for top speed, and not so much power. It's already pretty crazy.
As I understand, the shunt mod doesn't add extra top speed, only more torque, right?

So my plan is to buy 10 more 21700 batteries, a new 16s bms, and add those 2s5p to the existing pack for a total of 67.2v when fully charged.

Can it be true my 21700 batteries are like 3428mah each? I guess it take the 24ah and divide it by the number of batteries which is 70. There's only a looong strange number on my batteries, giving no clue about it, and a google search doesn't give any results on that number.
 
999zip999 said:
24ah*5= 4800mah I guess ??? Or so.

Stupid question, but how do you get 4800mah?

Isn't 1000mah the same as 1ah?
So 24ah is 24000mah / number of batteries = mah per cell ?
 
Does the controller have a 3 speed switch? If not you might look for the tabs on the controller and add one. Most controllers that have the tabs for it are set at middle speed, a jumper could give you more speed with less hassle. Not sure where it is. Most cases it is marked X1 X2 X3. I'm sure others will remember what to wire.

dan
 
id check to see if your bike will turn on at 68v, I wouldn't up the amps on your bms, if your running 21700 with 5000 mah, its probably called a 10 amp cell but really you need to find out what 21700 it is, like a Samsung 50e is a 10amp cell at 5p is 50amp bms if you pull more than 50amps from the pack you damage the battery.

theres other things on the bike that might not work over 63v, like the lights, your display, check the dc/dc converter, have a good look at what voltages are being used on the other components and find the dc/dc converter to see what its rated at.
 
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