Wiring up 4s + boards in series

[johnnyz]

Anyone know if the following diagram on wiring 3 charging boards will work? I want to wire them up in series but dont know if the following will blow something up...lol

If the wiring is correct, will each 4s board work with a 10s battery? or does the series have to be divisible by 4?





Thanks

John

 

[Htfan]

Great question!

Wondering if charging in parallel would work any better? You would probably need a special connector/switch to alternate between running/charging.

 

[johnnyz]

Great question!

Wondering if charging in parallel would work any better? You would probably need a special connector/switch to alternate between running/charging.

I was wondering the same thing...I am only using these little boards for Charging, so that I dont go over voltage. They will stop the charge once at around 4.15 volts which for me is fine..another reader has used these and has success...Ive asked him but still waiting for how he wired them up but in the meantime, if anyone else knows if they can be used either in series or parallel would be helpful!

Thanks

John

 

[Htfan]

Great question!

Wondering if charging in parallel would work any better? You would probably need a special connector/switch to alternate between running/charging.

I was wondering the same thing...I am only using these little boards for Charging, so that I dont go over voltage. They will stop the charge once at around 4.15 volts which for me is fine..another reader has used these and has success...Ive asked him but still waiting for how he wired them up but in the meantime, if anyone else knows if they can be used either in series or parallel would be helpful!

Thanks

John

I'm subscribed. I would like to know also.

 

[johnnyz]

Well....if no one is going to chime in on this post I am going to try paralleling the 3 boards and see what happens...havent got alot of time on this planet!!


John

 

[Ykick]

This is embarrassing to post scribble like this but since I’ve been asked in PM I’ll attempt to better illustrate what I’m doing with these very affordable and seemingly useful BMS boards.

Here’s an 8S connection using 2qty 4S RC Lipo packs. This can readily be scaled up 12S, 16S, 20S, etc.
View attachment 1
For this example the main power leads are series connected to form an 8S battery. Whenever you do this on RC Lipo the JST balance connectors form a redundant connection to the cells which correspond to the connecting point with the main power leads.

What I’ve been doing with these boards is solder some JST male pin connectors onto the BMS pads in the correct order so that when I connect to charge port everything falls into correct order and polarity. I just buy JST extensions and cut off what I need - http://www.buddyrc.com/12-4s-jst-xh-extension-cable.html

Here’s a picture of 4qty boards for my 16S packs to get an idea of my testing setup. One board I attached a female pin JST to look in with my cell log. Doesn’t seem to be that important - if you need to check cells using the JST’s, they can be plugged and unplugged in no particular order.

The charge only port has both red APP housings because I ran out of black housings. So, I stuck on a plug to better avoid confusion - which I’m providing plenty of that….

Good luck, test these buggers out!

FYI - I had one board that seemed to develop a drain or short on a 4S group. I dunno why but whenever I cycled it a couple times, that group would fall behind the other 4S groups.

I’ve swapped that board out and now everything seems to be holding well for the last week or two.

They don’t seem to pass more than 4-5A as rated. My 5A charger simply shuts off but these little 16S eBay chargers are a good bargain and 2A output works nicely with these BMS boards - http://www.ebay.com/itm/Scooter-Charger-For-ONE-Wheel-Electric-Self-Unicycle-Adapter-67-2V-2-0A-Scooter-/331786648148?hash=item4d40067a54:g:fQcAAOSwWTRWzQbL

I wouldn’t do parallel connections with these either? That sounds like a recipe to throw cells out of balance?

Eventually, I plan to add these to my 16S2P RC Lipo pack but I simply parallel the cell groups in the pack and then add whatever BMS I’m using at the moment.

So far, these are my favorite BMS to date. Cheap, simple charge protection.

PS - I dunno about 10S pack? Will these boards work as 2S? I think they might 3S if you jumper the last cell connection? Not sure about 2S though?

Good luck!

 

[johnnyz]

Alright!!!...I am going to follow this and try it tomorrow..will include pics as I go...

Thanks alot!


John

 

[johnnyz]

mmm....Well...hooked these up to a 36 volt 18650 battery pack, as the original BMS failed and I cant get by the little units thats why I thought I would try these...wired it up per the readers instructions, but when I went to attach the Negative pad to the Positive pad, serially it resulted in a bang and the pad was kind of obliterated...each of these parallel series of cells is 15 ah, so maybe that is too much amperage for these things???...not sure what is going on...the order was correct for sure, I double checked with my voltmeter...


You can see in the close up what happened to the pad when I attempted to attach the + pad to the next - pad...



Ideas??????????

 

[parabellum]

I can not judge connection between batteries but, it looks like main V short to me. Considering your batteries are series connected like laid out and according to balance wiring, You should have connected left board Negative to right board Positive to make series connection.

 

[Ykick]

Yeah, obviously a miss-wired connection and I’m reluctant to say anything more which might make it worse?

This situation might be best served using a cheap low power 36V 10S BMS connected for charge only?

I use these for multiples of 4S RC Lipo packs. 10S hardwire is something I can’t wrap my head around without both hands & eyes able to understand the entire circuit you’re attempting to configure?

I’m not even sure these will work 3S let alone 2S which you’re asking of one of ‘em?

But, I don’t think that’s what vaporized the pad. That’s a polarity problem, fairly certain.

They’re cheap enough to blow a couple but be careful you don’t damage one and not know it while relying on it for charge protection.

 

[johnnyz]

Sorry, unless Im missing something these are wired up correctly via instructions and I simply followed the above diagram with respect to wiring them serially.

In the picture, the 1st negative pad is wired to the last negative in the series, and then the next in sequence is the positive of that cell followed by each series connection, verified by my multimeter (voltage goes up by about 4.1 volts each time)
View attachment 2

The second bms board is also wired up correctly again verified by my multimeter...



What the heck am I missing??

p.s. The reason i didnt use a BMS is because theres very little room in this case as is the case with most of these battery packs, thats why I was interested in the little guys..next Im throwing together a 6 series (6 18650's) and testing another unit ( I bought 20 just in case of this very scenario).

John

 

[johnnyz]

Ok...so here we go..

Slapped together spare 18650's and hooked up the BMS just as I did with the 36 volt battery..also hooked up some voltage checkers to monitor voltage and using my Imax at low .04 amp charge, seems to be working so far...yes I have more cells than the BMS is counted for..lets see if it stops the charge...



John

 

[johnnyz]

It worked..

Got a "Connection break" on the Imax...looks like the cell was at 4.19 volts when it happened (voltmeter not the cell checker which was somewhat off).



Next Ill add more cells and try a serial connection...or maybe a parallel one...


John

 

[johnnyz]

Ok...well reader parabellum got it right...i should have connected the + to the - and now they are working together in series, however because they are working in series, they are getting charged and then the charge gets shut off as the next board charges and then again and so on and so forth


...so its an on/off on/off thing..I know this because I can see it plainly on my Cycle Satiator..so for now I have em charging..(at .07 amps as these cells are only 1800 mah).when I check back I'll see how theyre doing..

The above picture showing the charge voltage in the span of a second...it charges, then when the charge goes to the next bms board the voltage drops, then a second later it charges, then drops etc.

Is there a way to charge parallel?...is it just a matter of putting both + charging leads together and both negative leads??

Still dont know how im going to do a 10s battery yet...

John

 

[johnnyz]

Well...as set up these DID NOT stop the charge on one cell as it went to 4.33 volts before I disconnected the charger....either its not working or they dont work in series...

I suppose it could be the Cycle Satiator??..maybe the up and down of the voltages was the bms shutting of the load but the satiator getting back on it...

I disconnected the series connection and tried each board and viola...they stop the charge when hooked up to the Imax. (I cant charge 8s batteries with the Imax hence the Satiator), so the boards are not faulty. Im stuck...

Any feedback would be appreciated

Adendum:...Just in case it is the Satiator not allowing the bms units to stop the charge, Im going to discharge these cells and do it again this time observing the action of the voltage on the Satiator, see if it rises up and down like before..


John

 

[parabellum]

Any feedback would be appreciated

What I would believe, they do not work in series (as is now). My point is, board only interrupts ether Positive or Negative of the battery, not both. As result, at least one of the boards is bypassed by serial connection of the battery itself and does not make any difference, being ON or OFF. If you interrupt series connection on the battery, between those two 4s groups, you may find them working fine in series.

 

[Ykick]

Be very careful here. I’m discovering a problem where the board on the negative side of the pack goes weird and allows the other series strings to overcharge.

I’m beginning to believe this isn’t gonna work for anything except single 4S BMS applications.

Back to the drawing board. I’m still a believer in charge side only BMS for outdoor devices but I think I’ll stick to small current BMS units wired for charge only.

 

[johnnyz]

Be very careful here. I’m discovering a problem where the board on the negative side of the pack goes weird and allows the other series strings to overcharge.

I’m beginning to believe this isn’t gonna work for anything except single 4S BMS applications.

Back to the drawing board. I’m still a believer in charge side only BMS for outdoor devices but I think I’ll stick to small current BMS units wired for charge only.

I think your right as that is exactly what I have experienced...I dont see how you can parallel charge using these boards either...also, 2 of them simply didnt work...I bought twenty hoping they would work in series and they were cheap enough but dont think its a doable thing, unless someone has an alternate idea?


John

 

[Ykick]

I'm not sure yet what's causing this trouble? Might be controller spark the couple times I powered the controller/CA through the battery charge port?

Or perhaps as parabellum noted, a controller or some other load plugged across the main power port creates a current path effectively bypassing the series connected BMS board?

 

[johnnyz]

Yeah, either way, looks like this isnt doable..good grief..Ok...troubleshoot something else..like how do I reduce slightly the charge out of a charger?...I have run my headway cells for hundreds of cycles using only the battery medics, set to start discharging at 3.5 volts and setting the total charge at 48.8 on the Satiator @ 7 amps and when it gets to 48.8 volts it begins cutting the amps allowing the battery medics discharging at up to 450 ma to slow don the charge rate of these cells at the top...(since the Cycle Satiator at the time could not charge my 92 volt pack, I had to install 2 charge leads splitting this in two and charging twice)..but doing this works like a charm, the cells remain in balance at the top and I stop when I can see on the Cycle Analyst much more sag than usual.Dont need or use a BMS and everything is great. Problem is when your attempting to repair battery packs in which the BMS has failed yet the cells are fine, installing something like my setup wont work if the charger goes until theoretical 3.65 volts per cell.

Maybe Ill initiate another post on how to reduce the chargers voltage. If I can do that then this system will work.

John