ebike controller with any type of BMS in it?

General Discussion about electric bicycles.
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unclejemima
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ebike controller with any type of BMS in it?

Post by unclejemima » Apr 13, 2018 12:52 pm

I purchased this controller for a 24v power wheels application...

https://www.ebay.ca/itm/48-60V-1000W-Mo ... pq&vxp=mtr

(the listing originally said ok 24-60v, 24V rated to 700w and 48-60v rated to 1000W)

I've always wondered if they have any sort of protection to run a lithium battery without BMS?

I'm thinking power tool batteries.

I still don't get how power tools don't have a BMS in them...so the tool would have the BMS and low voltage shutoff?

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Re: ebike controller with any type of BMS in it?

Post by amberwolf » Apr 14, 2018 2:00 am

Most controllers have an LVC (low voltage cutoff). Some of them are programmable. Some of them you solder jumpers on the board inside. Some of them are automatic, and try to detect what nominal voltage your pack is whenever you connect it (but theyre not all good at it under all conditions). Some of them have no LVC. Youd have to find out how the LVC is implemented in any particular controller, or at least what its actual LVC value is, to know if its suitable for whatever battery you intend to use with it.



Just remember, without an actual cell-level BMS inside the battery (or some other cell-level monitoring), then you cant know if any cell group is going too high or too low during charge or discahrge. That means cells could be severely unbalanced, yet the pack still at the correct total voltage, such that some cells are so undercharged theyre damaged or destroyed by going to zero volts (or worse, negative voltage), and some cells are so overcharged they could catch fire. Its not all taht likely a scenario, but it does happen and it is why BMS are used. If cells always stayed balnced no one would need a BMS and no one would spend the money on making them. ;)

With my EIG NMC cells, I dont use a BMS because they stay balanced. and discahrge and charge equally. under the usage I put them thru. WIth an 18650 pack I have, without the BMS in there it would probably get rapidly unbalanced and have problems, possibly severe ones.

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Re: ebike controller with any type of BMS in it?

Post by unclejemima » Apr 14, 2018 12:52 pm

Interesting.

With what you said in your last post, you'd imagine power tool batteries to have BMS then as well? Or how are they prevented from damage during discharge and cells becoming un-equal?

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Re: ebike controller with any type of BMS in it?

Post by Matador » Apr 14, 2018 12:57 pm

For having opened 29 Makita BL1840 Battrery packs (4Ah 18V 5S2P) I can tell you that they have a circuit board in them for sure.
Of course it has LVC and HVC, and I think the PCB also balances cells, but that I`m not 100% sure.

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Re: ebike controller with any type of BMS in it?

Post by unclejemima » Apr 15, 2018 1:22 am

Yea, you’d think they would have a board and bms cause they almost always have a led meter on them...and I honestly don’t think it would make sense for the tool to have the bms in it...? But I recall hearing back in the day the older models did not.

Can anyone verify or confirm if other brands of power took batteries have bms in them?

They would be a fairly high load rating too you’d think as they draw huge power in tools.

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Re: ebike controller with any type of BMS in it?

Post by amberwolf » Apr 15, 2018 3:10 pm

Most old power tool packswere made of NiMH and NiCd, which were self-balancing when charged the right way (which makes them hot).

Sony made a cell call the Konion which was a Li-Ion cell that apparently did something similar, though Ive never used those so have no direct experience with them, and these were used in some power tool packs (Makita, IIRC, possibly others). They may still have had boards in them to monitor things, but I dont know.

Some other Li-Ion tool packs also dont use internal boards, and dont use selfbalancing cells. So these packs do get out of balance over time, and they also dont have any overdischarge protection. Depending on the tools theyre made to work with, there may be no protection in the tool either, so they depend on the user noticing the tool is performing poorly and putting the pack on the charger then, rather than running the pack further down than is safe and eventually damaging or destroying it (or causing a fire). I suspect their chargers do at least check for a minimum total pack voltage so they wont recharge a pack thats gone too low, but I dont know if thats true or not.


I think that most of the packs (or tools and chargers) do at least have overdischarge / charge protection, even if they dont have balancing circuitry or individual cell HVC/LVC.

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Re: ebike controller with any type of BMS in it?

Post by unclejemima » Apr 16, 2018 9:37 pm

I’m using some rigid 18v packs. According to the review I found of them here...

https://syonyk.blogspot.ca/2017/05/rigi ... y.html?m=1

It sounds like they indeed have a bms...but the last statement has me confused...
But as far as these particular packs go? They're useful for the designed tools, and that's about it. The BMS serves to keep you from doing anything interesting with them unless you learn how to properly tickle it, and I don't know how to do it. So, if you want to power an ebike or a camp stove, stick to the DeWalt packs.
I’m not sure what he’s implying...it has a bms so what’s wrong with using it for an ebike application?

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Re: ebike controller with any type of BMS in it?

Post by amberwolf » Apr 16, 2018 10:52 pm

Seems hes saying theres somethign more than just a connection required to activate the output and/or input to the packs, via the BMS. Probably it requires some form of serial data communication (like some laptop packs), and without knowing what to say and how to say it then whatever you plug it into wouldnt get (or give) any power.

It might also just limit the current they can output, without the right signal.

But I dont know those packs msyelf, so cant say what is actually going on inside.

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Re: ebike controller with any type of BMS in it?

Post by unclejemima » Apr 17, 2018 10:22 am

Seems hes saying theres somethign more than just a connection required to activate the output and/or input to the packs, via the BMS
.

Well it works and I was drawing a good 500W at 18v with no issues by just connecting to the + and - outputs.
It might also just limit the current they can output, without the right signal.
Well it appeared to work just fine the power level I was drawing what is more than enough for me. So I'm gonna assume as long as it works, I'm good to go.

I'm just gonna keep if it will cut power when it gets to low of voltage. The power tool right now (say a power drill) will quit working when the battery level gets to low. At that point I'll hook up the volt meter and see if the BMS actually shut off output of power (what would be good) and or if its the tool that decides it does not want to work at to low voltage...because if that's the case then there is no discharge protection without the tool...and that's what I'm worried about.

Sounds like the Dewalt 20V pack is good to go out of the box. To bad I didn't have a set of dewalt batteries!

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