I THINK I know how to hook up this BMS??!

Batteries, Chargers, and Battery Management Systems.
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David LaFerney   10 mW

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I THINK I know how to hook up this BMS??!

Post by David LaFerney » Aug 29 2016 3:14pm

First time doing this - Building a 13s 48v battery pack out of 52 18650s. Of course the BMS comes with no guidance whatsoever other than that it can be used as either a 14s or 13s manager without adding any components.

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My best guess is that I just connect my cell+s B1+ through B13+ to the first 13 pins in the connector and remove or insulate off the 14th pin - and that is the only difference between 13s and 14s usage? <<<THAT is my question. I just really don't want to mess this up. Unfortunately I haven't been able to get a response from the vendor.

Then for the rest of the connections D- (D for discharge) goes to the controller C- goes to the charge connector B- goes to the Battery negative and then the battery positive goes to both the controller and the charge connector, without connecting to the BMS other than through the balance wires.

Also, what is the name of the type of connector that the balance wires connect through? I would like to order some of them but other than balance connectors that stop at about 8 pins I can't find them. I suspect because I'm not using the right search term for the type of connector.

BTW - My wife and I rode some rental ebikes while on vacation and enjoyed it so much that I just had to build us a pair.

Thanks for any help I can get from someone with enough experience to know what I'm doing.

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Re: I THINK I know how to hook up this BMS??!

Post by dustNbone » Aug 29 2016 6:53pm

I believe the connector is known as a JST-XH, my 16S BMS uses 2 of them, one for each stack of 8 cells. I would imagine your setup would be similar, the connector pictured looks identical to mine, you just leave 2 or 3 wires unused. If you look on the back of the board (opposite side to JST connector) it appears that each pin is numbered. Just make sure you use 1-13, and not 4-16. All your other connections (B-, C- and D-) look right to me.

David LaFerney   10 mW

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Re: I THINK I know how to hook up this BMS??!

Post by David LaFerney » Aug 30 2016 4:11pm

So can you pretty much use any BMS card with fewer than the maximum number of cells just by connecting however many you have starting with B+1?

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flangefrog   1 kW

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Re: I THINK I know how to hook up this BMS??!

Post by flangefrog » Aug 30 2016 4:39pm

dustNbone wrote:I believe the connector is known as a JST-XH, my 16S BMS uses 2 of them, one for each stack of 8 cells. I would imagine your setup would be similar, the connector pictured looks identical to mine, you just leave 2 or 3 wires unused. If you look on the back of the board (opposite side to JST connector) it appears that each pin is numbered. Just make sure you use 1-13, and not 4-16. All your other connections (B-, C- and D-) look right to me.
When searching on eBay or Aliexpress search for XH connectors not JST-XH (try "xh 10s", "xh 11p" and "xh 11 pin" for a 10S battery). They're not made by JST but work fine.

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Re: I THINK I know how to hook up this BMS??!

Post by dustNbone » Aug 30 2016 5:55pm

Ahhh good to know, JST is just a brand name. That's going to save me some money one day :)

As for using a BMS with less than the maximum number of cell group connections, I'm not sure that will work with all BMSs with any number of cell groups. I would check the specifications, some list a specific number, some list a range. You can't always go by what's written on the board itself, the one you show above for instance is a board designed for 16S, but if you look it's only populated with 14 groups of components. The specs list it as 13S or 14S, they probably use the same board for a 15/16S model as well.

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Re: I THINK I know how to hook up this BMS??!

Post by Hwy89 » Aug 30 2016 6:03pm

You need to use all 14 pins for a 13S pack. The most negative terminal will be B1. the negative end of each successive group will be B2, B3, B4 ....up to B13 which is the negative pole of the top group. The positive pole of the 13th group will go to B14.
The rest of your assumptions are correct B+ is battery positive D is discharge through the controller and C is charge from the charger.

David LaFerney   10 mW

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Re: I THINK I know how to hook up this BMS??!

Post by David LaFerney » Aug 30 2016 7:58pm

Hwy89 wrote:You need to use all 14 pins for a 13S pack. The most negative terminal will be B1. the negative end of each successive group will be B2, B3, B4 ....up to B13 which is the negative pole of the top group. The positive pole of the 13th group will go to B14.
Are you sure of that? I'm not arguing, because I have no experience to go by - but if you look at the printed circuit on the back there is a printed connection from the big B- terminal on the front to the lowest position next to the B1+ pin connection.

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Re: I THINK I know how to hook up this BMS??!

Post by flangefrog » Aug 30 2016 9:20pm

Sounds correct to me. When lots of current is flowing through the battery negative cable the resulting voltage drop will affect the reading. Look up Kelvin (4 wire) sensing. Practically all BMSs use cell count + 1 pins.

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Re: I THINK I know how to hook up this BMS??!

Post by Hwy89 » Aug 31 2016 12:53pm

I see the trace you pointed out and I think you are right. I also noticed that all of the connector terminals are marked +B. That would also explain why the board was sold as 13s or 14s
Every other BMS I've seen was wired as I explained but this one seems to be different.
Sorry for the misdirection.

David LaFerney   10 mW

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Re: I THINK I know how to hook up this BMS??!

Post by David LaFerney » Aug 31 2016 3:25pm

No problem - thanks for taking another look though. Another hint is that there are only 14 connections total, so if you used one of them for the B- you wouldn't be able to use the board for an S14 pack - which it is rated for. S14 Or S13.

I have all the spaghetti for the BMS wired up, so I'll know for sure pretty soon now. I think I'll do some testing before I wire up the other one though - just to be sure.

Hard to find time to work on it during the week. Or ever.

David LaFerney   10 mW

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Re: I THINK I know how to hook up this BMS??!

Post by David LaFerney » Aug 31 2016 3:28pm

flangefrog wrote:When searching on eBay or Aliexpress search for XH connectors not JST-XH (try "xh 10s", "xh 11p" and "xh 11 pin" for a 10S battery). They're not made by JST but work fine.
Thanks. That actually does help.

David LaFerney   10 mW

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Re: I THINK I know how to hook up this BMS??!

Post by David LaFerney » Sep 09 2016 8:05am

So, I've hooked this thing up (two of them actually to 2 batteries) and it doesn't work - No charge or discharge current. A couple of volts are detectable from both of those, but that's all.

Why Oh why don't they either post clear instructions online for this kind of thing or include them with it?

I would really appreciate any advice I can get. This is all that is keeping me from finishing 2 bikes.

Just to be clear I did this...

"connect my cell+s B1+ through B13+ to the first 13 pins in the connector and remove or insulate off the 14th pin...
Then for the rest of the connections D- (D for discharge) goes to the controller C- goes to the charge connector B- goes to the Battery negative and then the battery positive goes to both the controller and the charge connector, without connecting to the BMS other than through the balance wires." So, the pin labeled B1+ is connected to the + side of the first cell in the pack. The - end of that same pack is also the main B- for the entire battery.

David LaFerney   10 mW

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Re: I THINK I know how to hook up this BMS??!

Post by David LaFerney » Sep 10 2016 11:54am

That is exactly what I have done, but it doesn't work. In the ebay listing the vendor says "The default is 14 cells. User can modify it to use 13 cells very simply without any additional components." but I can't get a response from them to find out how. I suspect that bit of knowledge would get me going, but I have no idea how to get it other than from the vendor - who won't respond. Also, if you look at the listing and the photo I included above you can see that they sent me a different PCB - which isn't really the issue in this particular case.

I'm going out to the shop right now to electrically separate the pack into 6s modules (and a single) and replace the BMS with balance leads - which I wish I had done to begin with now. Hindsight is 20-20 they say.


Ebay listing - http://www.ebay.com/itm/111091672244?_t ... EBIDX%3AIT

David LaFerney   10 mW

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Re: I THINK I know how to hook up this BMS??!

Post by David LaFerney » Sep 13 2016 7:53am

That is exactly how I had it (them) but it was a brick. I have them going now. It occurs to me that there should be a bms that you can plug in externally to balance / power leads - no doubt there is such a thing, and I just don't know about it. Thanks.

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Re: I THINK I know how to hook up this BMS??!

Post by docw009 » Sep 13 2016 9:20am

This is just of academic interest to me, as I hope never to have to replace a BMS, much less look inside a battery pack. Just want to understand it bit better.

Maybe you should have told the vendor you wanted it set for 13S. Now you have to set it. I dunno, but I would guess each one of those 14 identical legs has a voltage monitor connected to circuitry that turns on the MOSFETs to allow current to flow thru battery if voltage is in spec. They also disconnect the charger ground when the leg gets to 4.2 volts, and maybe start balancing.

That suggest the unused 14th voltage detector is live and running so it won't let the battery run. It's telling the control, "whoa, this cell is dead!" If so, that implies you have to find its output and disconnect it. I think that's what the vendor means by "no additional components needed".

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Re: I THINK I know how to hook up this BMS??!

Post by David LaFerney » Sep 13 2016 12:09pm

"Maybe you should have told the vendor you wanted it set for 13S."

I agree - in retrospect that IS what I should have done. But I'm a do-it-your-selfer and they said that it was a user configurable thing, and I just assumed that they would also tell how to do it.

suggest the unused 14th voltage detector is live and running so it won't let the battery run. It's telling the control, "whoa, this cell is dead!" If so, that implies you have to find its output and disconnect it. I think that's what the vendor means by "no additional components needed".

I have a high degree of confidence that you are correct there too. Most likely cutting a connection with an exacto knife would have got me going with pretty much no drama or delay. If I knew which connection to cut. I was hoping that by posting the pictures someone on here would know based on previous experience since I couldn't get any communication from the vendor.

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