KS 14 Battery Configuration

[OliverH]

I think each series pack has one BMS. I need to look on pictures.

[Jason McNeil]

 

3 hours ago, OliverH said:

I think each series pack has one BMS. I need to look on pictures.

Yes, each in the series does have it's own BMS, but as @Keith said, the critical question is whether this is a Y-lead within the protective wrapping so that the load between packs is passed through. I have asked KS for photographic or other supporting evidence of exactly how this is designed. Going back to Zylmex's comment, does anyone have any insights into how the pack BMS/wiring is designed on the GW 680Wh/850Wh?

[OliverH]

59 minutes ago, Jason McNeil said:

 

Yes, each in the series does have it's own BMS, but as @Keith said, the critical question is whether this is a Y-lead within the protective wrapping so that the load between packs is passed through. I have asked KS for photographic or other supporting evidence of exactly how this is designed. Going back to Zylmex's comment, does anyone have any insights into how the pack BMS/wiring is designed on the GW 680Wh/850Wh?

The GW question would be interesting as there were some comments regarding the GW BMS.

[zlymex]

On 2016/1/21 at 10:16 AM, Jason McNeil said:

 

Yes, each in the series does have it's own BMS, but as @Keith said, the critical question is whether this is a Y-lead within the protective wrapping so that the load between packs is passed through. I have asked KS for photographic or other supporting evidence of exactly how this is designed. Going back to Zylmex's comment, does anyone have any insights into how the pack BMS/wiring is designed on the GW 680Wh/850Wh?

This is the photo of my GW MSuper2 680Wh. There are two 340Wh packs and they are parallel connected by two Y-connectors.

Later, I paralleled another 200Wh pack to it making total capacity of 880Wh. Photos below were for two of my friends.

[Jason McNeil]

1 hour ago, zlymex said:

There are two 340Wh packs and they are parallel connected by two Y-connectors.

Thanks Zylmex, but do you know as a certainty that the KS 340Wh packs are not daisy-chained with a Y-connector within the protective wrapping? 

[zlymex]

40 minutes ago, Jason McNeil said:

Thanks Zylmex, but do you know as a certainty that the KS 340Wh packs are not daisy-chained with a Y-connector within the protective wrapping? 

No
Perhaps someone(who uses EagleTree, who opened the 800W motor cover) knows.

[Jason McNeil]

1 hour ago, zlymex said:

Perhaps someone(who uses EagleTree, who opened the 800W motor cover) knows.

Cloud has a spent double pack that no longer charges, he might be willing to donate for dissection in the interests of scientific inquiry  

[dmethvin]

A point @zlymex made in this thread may be important, from a BMS data sheet it says the BMS starts balancing as soon as any cell reaches the target max voltage, for example 4.2v. In previous threads it was implied that balancing didn't begin until charging was almost complete, which is probably true if the cells are all close to each other in voltage. So even if the cells in the pack were way out of balance, maybe that BMS behavior prevents them from continuing to be unbalanced, even if packs with separate BMS are put in parallel?

[Keith]

21 hours ago, dmethvin said:

Maybe I'm understanding it wrong, but if charging a series set of Li-Ions could be done only through the discharge lines we wouldn't need a BMS. Basically I have been learning what I can by watching videos like this one (for an example see the 7 minute mark). Specific cells in a series pack may end up at different voltages. That's why the BMS tries to balance them by selectively charging cells that have lower voltages. Normally the BMS would never overcharge any specific cell to get the entire pack up to voltage. Once you start charging via the output there's no control over that--as you say, the two packs must be at the same potential, even if that ends up overcharging a cell in the process

Dmethvin,

Yes you are understanding wrong (although your post immediately above this one suggests you are understanding now?)

The video you link to is excellent (and recommended viewing for anyone trying to understand why we need a BMS).

As shown in that video. BMS does not charge cells it discharges them ( or more accurately with our BMS prevents them taking any more charge.

Also, in that video, all charging is done via the discharge lines, there is no seperate charge lines in the LiPo's he discusses it is multi-cell Lithium batteries that require a BMS, where the charge comes from is of no concern.

BMS are installed in each pack, multiple packs with their own BMS do not in any way interact with each other, each BMS looks after nothing but it's own pack.

See my Figure 1 below: to keep it simple I have shown only 4 cells, please note this is just a schematic, I am not inferring that switches and zener diodes are actually used. As the figure shows the only reason we have separate charge and discharge lines is because the BMS has additional charge (which is useful) and discharge (which is damn dangerous) protection. Remove the charge and discharge protection and there is no need for a separate charge connection at all it is just a straight through line. Indeed regenerative braking does charge the pack from the discharge lines and it is absolutely vital that BMS cell balancing still occurs - which, of course, it does!

Figure 2 shows the way I understand most EUC actually balance charge. Across each cell (or set of parallel cells in the same pack) is a shunt circuit that behaves like a zener diode; when any cell is below 4.2V charge current passes through the cell. Once it reaches 4.2V the shunt switches on and shunts the current around that cell holding it at 4.2V. Cells below 4.2V continue to take current, I've shown this with the purple arrows in Figure 2.

[dmethvin]

That makes a lot of sense @Keith, now I can see how the BMS could continue to work even when paralleled. Thanks!

[trya]

@KaleOsaurusRex can you please contribute and tell us the configuration and connection of batteries in your KS16, please?

[KaleOsaurusRex]

@trya

I'm waiting on answers just like you guys are

[Frankman]

 

@Cloud   I cannot understand why these batteries are connected in such a way. I can only suppose that the batt. on the right is made with cheap low discharging rate cells, so it cannot be connected directly with the controller board? Who knows?

 On my EUC I connected 3 battery packs in parallel (all outputs together, 174Wh + 132Wh + 132Wh) and it works fine

[zlymex]

17 hours ago, Frankman said:

I cannot understand why these batteries are connected in such a way.

May be quick and easy this way(parallel connection needs two Y-connectors).  Low discharging rate cells can also be paralleled.

[SirGeraint]

I'm hoping someone with knowledge of the Gotway MSuper2 can answer some questions related to this discussion.  Because so far Gotway hasn't been able to.  I could post pictures if necessary.  It seems that Gotway must have changed the way they connect their battery packs (and have forgot they ever did it that way).  Here's the story.

When I got my MSuper it had 2) 340Wh battery packs.  BOTH of them had a SM-2P connector for charging and an XT-60 to connect to the Controller Board.  There was a daisy chain of SM-2P connectors to connect the charger connector to each battery.  There was a daisy chain of XT-60 connectors that went to the controller board. 

Well, one of my battery packs was bad so Gotway sent me a replacement.  But the replacement battery pack had different connectors.  It had a SM-4P (not a SM-2P) and it didn't seem to charge through it.  It had a male XT-60 and a female XT-60.  So, the only way I could get it to charge was to connect the output of my original good battery pack to this new replacement battery pack (with the XT-60 connectors) and then connect the output of the new replacement battery pack to the Controller board.  What bothers me most about this is that the output to the Controller board is a Single Point of Failure.  Because of this I would like to make a Y-adapter so that the output of the original good battery pack can go both directly to the Controller board as well as to the new replacement battery pack.  Will this be OK?  I don't know what is inside the battery pack. It seems this would effectively be connecting both sides of the new replacement battery to the same wires and I don't know if that would cause a problem.  Does anyone know?

Thanks.

 

[Nevin@Tec-toyz.com]

@SirGeraint, pictures would help. You may have an old version pack which uses a different BMS board. They may have sent you the newer type BMS pack

[SirGeraint]

Here are the pictures.  They are, in order, the Charger Daisy-Chain Adapter, the Connectors that both of my original battery packs had, the Connectors that the new replacement battery pack had, and a hand drawing of how it was originally connected together.  @NevNutz, you are probably right about it being an old style vs. new style.  The strange thing is that my reseller has forwarded them emails where I have explained the situation and they seem to not know what I am talking about.  It like they've forgot they ever made them the way mine is.  But I just need to know if a Y-adapter would be OK or not.   Or if I have to leave it like it is (with a Single Point of Failure) and 'I believe' less instantaneous current.

Thanks

[Nevin@Tec-toyz.com]

The new battery they sent you with the SM-4P is for the newer version BMS batteries. Are the wires on that SM-4p connector 2 red and 2 black wires? If so, thats for high and low voltage protection. But I don't think those BMS boards are compatible. What was your original issue?

[Cloud]

On 26 января 2016 г. at 3:59 AM, Frankman said:

 

@Cloud   I cannot understand why these batteries are connected in such a way. I can only suppose that the batt. on the right is made with cheap low discharging rate cells, so it cannot be connected directly with the controller board? Who knows?

 On my EUC I connected 3 battery packs in parallel (all outputs together, 174Wh + 132Wh + 132Wh) and it works fine

I believe the quality of the cells is the same in each pack. Each pack can be connected to the control board indepently, without the other pack. But only one of the packs has the connector for the exterior charger. I would lie if i told you i know the reason why it was designed this way or how the wires are commutated ibternally inside the shrink wrap.

[Frankman]

@Cloud    So probably, as the battery packs are made in large series and all have the same couple of connectors, for the manufacturer is much more faster, easy and cheap to connect two batteries in this way. But obviously the best way is to connect the battery outputs together.

Every time I buy a device (especially from Asia) I always try to open it and carefully check inside for all components, cables and connections. Because, due to high rates of production and lack of quality controls, there may be some little imperfection that may compromise the efficiency of the whole device. And, believe me, a lot of times I solved a problem before it happened.

And many times you can also learn and understand how it works.

 

 

[Cloud]

6 hours ago, Frankman said:

@Cloud    So probably, as the battery packs are made in large series and all have the same couple of connectors, for the manufacturer is much more faster, easy and cheap to connect two batteries in this way. But obviously the best way is to connect the battery outputs together.

Its possible but in kingsong 14" the way the wires are routed may be more complicated than a parralel connection would be. Its pretty crowded in there and not much room for wires, The wires from the battery pack on the left side goes thru the center area into the battery compartment on the right, then the wires from the battery on the right goes back through to the compartment on the lef, and there it connects to the board. Wouldnt it be easier to connect in parralel? This way the wires from one of the batteries would have to cross over to the other side. Youd just need either a Y connector or two points on the control board to connect to.

6 hours ago, Frankman said:

Every time I buy a device (especially from Asia) I always try to open it and carefully check inside for all components, cables and connections. Because, due to high rates of production and lack of quality controls, there may be some little imperfection that may compromise the efficiency of the whole device. And, believe me, a lot of times I solved a problem before it happened.

And many times you can also learn and understand how it works.

This is one of the best advice ive seen. I myself fell pray many a time to not checking the connections inside for potential lack of QC

[zlymex]

On 2016/1/28 at 0:06 PM, SirGeraint said:

There was a daisy chain of SM-2P connectors to connect the charger connector to each battery.  There was a daisy chain of XT-60 connectors that went to the controller board. 

These "daisy chain connectors" of Gotway are actually one Y-connector.or two Y-connectors(which equivalent to a cross connector), facilitating the parallel connection of all the packs. If you can juest replace SM-4P of the new pack with SM-2P from the old pack, the new pack will be connected the same way as before.

[SirGeraint]

On 1/28/2016 at 3:33 PM, NevNutz said:

The new battery they sent you with the SM-4P is for the newer version BMS batteries. Are the wires on that SM-4p connector 2 red and 2 black wires? If so, thats for high and low voltage protection. But I don't think those BMS boards are compatible. What was your original issue?

 

On 1/29/2016 at 9:25 AM, zlymex said:

These "daisy chain connectors" of Gotway are actually one Y-connector.or two Y-connectors(which equivalent to a cross connector), facilitating the parallel connection of all the packs. If you can juest replace SM-4P of the new pack with SM-2P from the old pack, the new pack will be connected the same way as before.

Yes, @zlymex, I prefer the cross connector (parallel connection) way of connecting them.  But I tried connecting a SM-2P connector to the wires from the SM-4P and it didn't charge.  Unless the problem was that I connected the SM-2P to BOTH of the wires and should have only used 1 red and 1 black.  Is that what I should have done?   If so, I will need to buy another SM-2P connector.

@NevNutz, If the solution mentioned above is the correct way to do it then it negates my original questions... Which were,  if the way I am charging it (with the output of one battery charging the new battery via an XT-60) is OK.  And, would it be OK for me to use a Y-Adapter so the output of the first battery could go to both the new battery and directly to the Controller board.

The original way that mine was wired up seemed simple.  I don't understand why they complicated it in their new design.  I used to be in Electronics so I'm sure if someone explained it to me I would understand.

I want to minimize how many times I have to open the case so I am hoping to have my course of action laid out ahead of time and have all the parts I am going to need.

I appreciate the help from both of you.

 

[Jason McNeil]

Had quite forgotten that KS had forwarded to me a comparison of the original & new (Mark III) uprated BMS boards. Can anyone here infer if this schematic provides parallelization of power through the packs?

PCB on the left is the original, while the upgraded one is on the right is the new board.

[Chriull]

On 20.1.2016 at 6:09 AM, zlymex said:

Because I opened the shrink wrap. Charge wires are thin and not connected to the output wires directly.

Edit: 
True there exist packs with only one pair of wires for input and output(what is called? In Chinese it called 同口, direct translate to 'same port'), the BMS are more expensive and difficult to make for large current. Photo below is the BMS of the 64 cell pack of the KS-18A

 

15 minutes ago, Jason McNeil said:

Had quite forgotten that KS had forwarded to me a comparison of the original & new (Mark III) uprated BMS boards. Can anyone here infer if this schematic provides parallelization of power through the packs?

PCB on the left is the original, while the upgraded one is on the right is the new board.

There is not really anything to be seen in detail ;(

If you look at the above BMS from the KS-18A posted by zlymex you can recognize the schematics posted by hobby16 in 

You have the discharge protection mosfet X1 which goes to the voltage inversion diode T1 (in this case the body diode of MOSFET ?Q21?) which leads to C-. C+ should be connected to P+ (cannot really see it on the photo). The overdischarge protection MOSFETS (normaly 3 pieces in parallel in other BMS) got replaced by the fuse.

So if you daisy chain this BMS (discharge output goes to the charge input and so on until the last discharge output goes to the mainboard) you have (almost) the whole discharge current flowing over the overvoltage protection MOSFET (and the voltage inversion diode/Mosfet)- who is sitting there alone and not really designed for that load...

Could be that in the right Mark III BMS the "blobs" near the stripes above the charge/dischare wires are each two MOSFETS in parallel as overdischarge and overvoltage protection?

However - lets assume, that the principle schematics did not really change (or if you do not want to make this assumption, just consider for the following the KS-18 BMS version from zlymex) you definitely have the battery packs in parallel. Just with the overvoltage protection MOSFET and voltage inversion diode inbetween each pack.

This practically does not matter anyhow while charging - just each following pack gets minimal less voltage in because of the (very small) voltage drop about those two mosfets.

The problem as stated above is the (almost) full current flowing through this one MOSFET which could have gotten a second in parallel in the new BMS?

The second problem by this approach is when regenerative breaking occurs: Imho than all voltage generated from the motor only charges the first pack (nearest to the motor) and the voltage inversion diode is blocking off all the other packs. So if you have (almost) full battery packs and lots of power generated by the braking motor you just stress the first pack and the stress is not divided to all battery packs. (I cannot see if this diode ist still existant with the new BMS ...).

Would be interesting if i made any consideration error or this is really true