Bestech power BMS review

Batteries, Chargers, and Battery Management Systems.
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cwah   10 GW

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Bestech power BMS review

Post by cwah » Sep 05 2013 4:48am

Hello,

I purchased a 20s 35A bms to use with my lipo pack. Here is the BMS:
Image

Image

The data sheet:
Image


But there is a lack of information on the wiring, here is what I have:
Image

A) Any idea what the second hold is used for? (see A in the picture)

B) And why is there positive and negative in this area? Shouldn't it be only positive wiring? (see B in the picture)

Thanks
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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friendly1uk   10 MW

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Re: Bestech power BMS review

Post by friendly1uk » Sep 05 2013 5:19am

Part B is just showing you your load (bike) has a +&- that want connecting to the bms.

They have put the charger straight across the same place. This is how regen would work. It's not how I expect a typical charger to connect though. I have seen it drawn this way when I was looking to buy from them and comparing different suppliers who sell the same thing. They were offering different drawings for the same thing, and I imagine what you have there is not the right drawing.
I can never spell his name, but we have a resident that buys a lot from them. He will know. Dunum/dnmun something like that.

I have not long been up, but I'm sure there is good reason to connect a charger through it's own switching fet.

Is this really a review thread? I have one of their boards here that I'm not sure I want to use. It does have a C- though.
bmsbattery sent me broken and incorrect stuff, and won't even talk to me about it.

cwah   10 GW

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Re: Bestech power BMS review

Post by cwah » Sep 05 2013 5:49am

I think I got it. I'm going to plug it accordingly to the drawing.

I hope the balancing feature is working well.


ps: it's a review because I'll send pictures and everything. And tell if it worth it
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: Bestech power BMS review

Post by dnmun » Sep 05 2013 8:17am

the BMS is in the negative lead of the battery. it has no B+ connection. there are two holes there so you can connect two wires. one goes to the controller and one goes to the charger negative lead.

you don't need to tell us if it is worth buying. most can tell from just looking at it. i just ordered a bunch of those D167 too. for lipo and lifepo4.

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Re: Bestech power BMS review

Post by 999zip999 » Sep 05 2013 10:26am

I'll take a review. Thanks

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pdf   10 kW

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Re: Bestech power BMS review

Post by pdf » Sep 05 2013 12:02pm

What are the two white wires at the top of the first diagram, with adhesive on them? Is this a sensor (temp?) of some sort?
-------------
Jamis Commuter 1.0/Xtracycle Stokemonkey 36V LiFePO4, 15 ahr
Giant Boulder 9C 8x8, 48v, 10 Ahr LiMn from ebikes.ca

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Re: Bestech power BMS review

Post by dnmun » Sep 05 2013 12:06pm

that is a thermal circuit breaker. when the heat sink gets hot enuff to cause the breaker to exceed 80o C then it opens and the circuit current that the BMS uses is interrupted and the BMS turns off.

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friendly1uk   10 MW

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Re: Bestech power BMS review

Post by friendly1uk » Sep 05 2013 12:18pm

I didn't notice before. Point A is connected to the solder pad below to it. You can use both of them for your two wires, Power and Charge.

As you can see from the posted image, overcharge protection may allow the cells past 4.3v which I'm not keen on.

My issue won't show with my fish eyed camera. I have the same heatsink and it does not sit on the body of the fets. You can see daylight. It does sit flat to the mounting tab though, so something is not square. Could be the heatsink or the fets. During the clamping operation the board has become S shaped not flat. My board is a double stacked affair, and you can see the interlinking pins between them are not right because the board is not flat. I need to run an iron over everything to see if I can stress relieve it. I can't put a saftey device in to service looking like the solder is about to let go, or the tracks are going to get lifted. Just a glance and you know it aint right.
bmsbattery sent me broken and incorrect stuff, and won't even talk to me about it.

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Re: Bestech power BMS review

Post by dnmun » Sep 05 2013 12:22pm

i think i will be able to show that they cut out at 4.255V when i get them. with their comparators, i have found the HVC error is always low side so i don't expect any of them to get to 4.3V.

the heat from the mosfet comes out on the tab so that is why the metal to metal contact is on the tab.

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Re: Bestech power BMS review

Post by cwah » Sep 07 2013 6:08pm

Ok, I just finished wiring my 20s lipo:
Image

Added few cell log to it. I've set the final voltage to 84V.

Let see what if HV cut off will stop charge before cell log alarm rings.....
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: Bestech power BMS review

Post by friendly1uk » Sep 07 2013 6:32pm

dnmun wrote:i think i will be able to show that they cut out at 4.255V when i get them. with their comparators, i have found the HVC error is always low side so i don't expect any of them to get to 4.3V.

the heat from the mosfet comes out on the tab so that is why the metal to metal contact is on the tab.
If it's consistently around there then I'm happy. Wiki claims 4.28 is a common figure from the cell manufacturers. That too would have some tolerance I'm sure, but I like a margin I can see.


Sudden craving for spaghetti. Must be something round here I have seen lol
I'm not sure I would do my first charge indoors with that much going on. Pop it on a tray so you can sling it outside
bmsbattery sent me broken and incorrect stuff, and won't even talk to me about it.

cwah   10 GW

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Re: Bestech power BMS review

Post by cwah » Sep 07 2013 10:36pm

Ahah, you are right, I've put my lipo in a metal box in case the bms is not working :lol:
Image

Lipo alarm from celllog is about to start.... or auto-bleeding is also about to start lol. Or fire? :lol:
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: Bestech power BMS review

Post by cwah » Sep 08 2013 4:11am

I left it charge overnight.. it doesn't seem to be bleeding very fast.....
Image
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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friendly1uk   10 MW

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Re: Bestech power BMS review

Post by friendly1uk » Sep 08 2013 4:59am

What are the other 4 cells doing, they seem to be what is holding you up. I can't see where 17.01v has gone, which is 4.2525v each if evenly distributed. Your highest cells are in that set. You could find them and drain them a little till your display says they are around 4.19v like the rest. Then they can all get charging again.

TBH I would just wait. You have a fair number of cells at 4.2 and non below 4.15 so there not miles apart. Just move one of the cellogs to the set of 4 that is most likely to cause any problems.
bmsbattery sent me broken and incorrect stuff, and won't even talk to me about it.

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Re: Bestech power BMS review

Post by dnmun » Sep 08 2013 8:51am

you have 42mA balancing current. the difference between 4.2V and 4.15V is about 4% so 4% of 5Ah is about 200mAh so it should balance in about 5 hours.

if you hit the HVC on these BMSs it has to be discharged back below 4.08V on the high cell to reset. what is the shunt current? if you measure that you will know if it is still charging.

cwah   10 GW

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Re: Bestech power BMS review

Post by cwah » Sep 08 2013 10:40am

I was able to see when it's charging as I connected my amp meter in serie.

But yeah, it takes forever to balance. I decided to give and and have a ride for now. I don't like having my lipo sitting at 4.22V for too long
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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