Using 20s BMS for 18s battery

gomme600

1 mW
Joined
Feb 6, 2017
Messages
13
Hi there. I have already asked in an old thread but thought that it would be best to start a new one.
I have a homemade ebike with a 18s8p battery. (75.6V, 16AH). At the moment I have to remove all 6 battery packs (It is made up of 6 homemade 18650 packs: 6S4P, 25.2V, 8AH) and charge them using my rather slow accucell 6 charger. I would love to be able to just plug the bike in when I get home and have it charged within a few hours (It takes over ten hours at the moment!).
I am having a hard time finding a 18s BMS, so does anyone know if a 20s one would work?
There seem to be quite a few 20s ones around in my budget (keep in mind that I don't have tons to spend, I just need something to keep the batteries in check), I have a budget of about 30€ to 40€.
Do you think that this one would work? https://m.fr.aliexpress.com/s/item/32238809349.html?trace=wwwdetail2mobilesitedetail&productId=32238809349&productSubject=20S-72V-84V-li-ion-battery-BMS-PCB-72V-lithium-battery-with-25A-constant-discharge-and&scm=1007.13339.33317.0&pvid=66005194-26ce-481b-a756-a6aa3b972c09&tpp=1#autostay

Have any of you used a cheapish bms before with succes? What do you use for large batteries such as 18s ones?

Thanks,
Seb.
 
Henry at best tech does them

http://www.bestechpower.com/666v18spcmbmspcbforli-ionli-polymerbatterypack/
 
Thanks for the suggestion, I can't find any prices there though and I'm not sure that they would be under 40€.
 
The controller can draw a maximum of 45 amps, so 60 amps sounds like a good idea, that way I'm sure not to blow anything up!
The motor is actually a repurposed alternator so it can take something like 70 amps with the right controller.
I am using Samsung ICR18650-22F 2200mAh cells.
24 per pack and six packs to make the ebike battery. (18s8p).
As I am on a budget I was thinking of just using the BMS to charge and connecting directly to the battery for discharging, that way I can use a bms with a lower discharge current.
 
Oops, must have read the data sheet wrong. 45 Amps is peak though so most of the time they are within that 35 amp limit. Looks like I'm shortening their life a peak but the extra current draw shouldn't be dangerous. In this test the guy goes up to a 7 amps discharge: http://lygte-info.dk/review/batteries2012/Samsung%20ICR18650-22F%202200mAh%20(Green)%20UK.html
I am thinking of adding some more packs in the near futur anyway (18s12p) so that will fix the problem.
 
I might have enough batterys to make an 18s2p pack. I addition to my 18s8p pack that would be 44 amps current draw, close enough.
 
Well I have been talking to the seller on aliexpress and he told me to purchase this one: https://m.fr.aliexpress.com/s/item/32311499040.html?trace=wwwdetail2mobilesitedetail&productId=32311499040&productSubject=18S-75-6V-Lithium-ion-battery-lithium-polymer-battery-BMS-with-Max-60A-constant-discharge-current&spm=2114.06010108.3.1.E191Hf&ws_ab_test=searchweb0_0,searchweb201602_5_10065_10068_10000074_10000032_119_10000025_10000029_10000028_10060_10000067_10062_10056_10055_10000062_10054_301_10059_10099_10000022_10000013_10103_10102_10000016_10096_10000019_10000056_10000059_10052_10053_10107_10050_10106_10051_10000053_10000007_10000050_10084_10083_10000047_10080_10082_10081_10110_10111_10112_10113_10114_10115_10000041_10000044_10078_10079_10000038_10073_10000035_10122_10121,searchweb201603_10,afswitch_2,single_sort_2_default&btsid=90573ec9-b224-48c1-bf09-8af1db092392#autostay
And that he would change it so that the max charge current was 60 amps (same charge and discharge port).
I also got a discount, 38 dollars or 36 euros.
 
Received the BMS today, can't test it as I haven't got my step up converter yet though. Here are a couple of photos: https://goo.gl/photos/JPiFBE3DXq3YZ3Jw7
 
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