Space Cell Pro 3 - 10 amp BMS?

I have a space cell pro 3 (10S3P). I opened it up to reorganize the components to maximize my wheelbase for dual vescs and peripherals. Once i opened it up I noticed that the BMS was pretty small. Upon further investigation i noticed that the BMS label says “36V” on one line and “10a” on the next line. There is a bunch of Asian text inbetween and I haven’t had any luck finding this BMS online to see what the details are. Lastly I also noticed that the negative discharge cable from the battery pack is going directly to the power switch (anti spark?) board, which is connected to the bms and out to my xt60 discharge cable which came with a 40amp inline fuse. I’m a little confused as the other teardowns of the Space cell I’ve seen on this forum all have bigger BMS’s, I’m not sure what to make of my findings. Do the pictures indicate that the BMS is being bypassed for discharging ? Did Enertion use a 10amp BMS on my Space Cell strictly for charging and balancing the cells only ? If anyone can share some insight on what is going on here I would appreciate it.


Discharge Cables and Power Switch Board

the BMS has to be bypassed. I cant tell by the pictures provided but that is the only way a 10 amp bms will work. its only used for charging. (brings cost down)

That’s what i was thinking too but have only seen talk about a 30amp and 50amp BMS when it concerns the Space Cell. I also saw the posts where @evoheyax actual bypassed the BMS on discharge on his Space Cell and I think Enertion was not fond of the idea.

interesting. wonder what @onloop has to say on this. I’ll check mine when I get home. Aside from balancing, isn’t the low voltage cutoff another reason we’d want the BMS wired for discharge?

Yes if you want to take advantage of low voltage protection you would need to go thru the BMS.

Hmmm that being said I wonder if this space cell will allow you over discharge and ruin it.

yeah this is definitely a curiousity of mine as well.

Now of course, I’m using a VESC and I have low-voltage protection in there as well but coming from an engineering background it’s hardwired in my brain that more at least 2 fail-safes are a good measure of quality. I’m a little concerned at the prospect of this corner being cut, especially after a much higher AMP BMS was advertised on this forum in batches previous. Not jumping to conclusions yet-- I haven’t looked at mine yet. But mine is from this latest batch. so it would not surprise me if I find the same thing. the BMS was definitely smaller than i anticipated

There is an improvised way to do specific cell low voltage cutoff while bypassing the BMS, you use an arduino to check if the BMS has done cutoff, and use the arduino to do the cutoff, for example you connect the receiver to the VESC thru the arduino, and than the arduino can send 50% PWM when he detecs cutoff from BMS

I’m curious on what you find. If we are bypassing the BMS for discharge then why only a 40 amp fuse ? The pack should be able to do 60 amps and I think we could conservatively discharge 50 amps and get more power to our motors. I would just like some clarity so that i know for sure what is going on and what the intention was/is.

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Semi related

I spoke with enertion support and they said the bms handles up to 80a discharge current, though i suspect that it’s really just bypassing the bms.

yeah I’d say that’s probably marketing speak. If @themegak popped open the case and there’s a BMS with 10a written on it Plus TWO positive leads from the battery then that could be the smoking gun. I’ used google translate to analyze the photo. The 2 characters in front of 10A say “Charge” and the partial unobstructed characters after 36v say “Lithium Ion”

Are you able to physically see what kind of BMS you have in your Space Cell Pro 4

Pretty sure it’s the same as SCP3

I have a Space Cell Pro 3. If your BMS is like mine then you too would have a 10 amp BMS. You may want to take a look. Up to you, but it is always good to know what you are working with.

I took a look and it’s physically the same, but I didn’t read too much into it. I can pretty much guarantee yours and mine are not 10A discharge BMS’s. As @t1m0007 pointed out it’s probably 10A max charge current. Enertion claimed it’s 80A discharge, though I’m a bit skeptical on that.

Looking at the two pictures, I believe the BMS is for charging only. No amp limit on discharge. Correct me if I’m wrong but, the main negative lead should be going into the BMS and going out of the BMS for amp limiting.

It’s just hard to believe a BMS that small can output that many amps. I am skeptical that we are discharging via the BMS. Then again I am no BMS expert.

Sorry but can you take a picture of yours as I want to be sure we have the same BMS so that i can assume i can change my fuse holder and fuse and bump my Batt Max up to 50 amps safely across two vescs (25 amps for each vesc). I would appreciate this greatly.

Yea, I think it’s just bypassing the BMS for discharge and they said 80A to me because thats the output rating of 4 parallel cells. Either way I would replace the fuse holder or remove it altogether as 40A is a bit small for this pack.

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most BMSs interrupt the negative lead. That’s to say all the ones i’ve ever seen or used did. this is interesting. I don’t think i’ve seen any like this yet, they must be lasting longer.

I also noticed that the VESCs you get from Enertion are now coming automatically set to a 42 volt limit and though i didn’t pay enough attention to remember, i’m willing to bet that the cutoff is also 10S friendly. So the VESCs are actually protecting the pack from over discharge now? Seems odd to me.

in a complete this would work fine. I’m not sure how long it would last in a DIY build though. HMMMMMM.

VESCs voltage cut offs tend to be higher than BMS’s anyway. Supower has a 2.9v over discharge cut off by default. I don’t see a problem with using the VESC for that. However, if you mean over current, I think the Space Cell is bypassing BMS discharge and relying on the 40A fuse to not bust your components in case of battery mutiny.