battery upgrade Question for double battery build

[Keith]

Hmmm...... OK, if only at 40% charge it would drop quite quickly, but not that quickly I wouldn't have thought. So several things seem to be going wrong at the same time. It's difficult to guess what of several things it could be.

Ringing alarm bells in my head is fake 18650 cells which have a tiny Lithium cell inside them, they would take virtually no current and deliver virtually none as well. A BMS that is both preventing or limiting charge and discharge could also be a problem.

One test comes to mind straight away. If you can get a meter safely ( noting warnings @esaj has given already) onto the two end connections of the 16 cells I.e directly on the cells without the BMS in the way, measure the voltage and then connect the charger through the BMS. The current can only drop once the charger reaches full voltage of 67.2 to 68V. (Depending whether it stops at 4.2 or 4.25V/cell). If the charger goes green but the battery is still at 61V then the BMS charging circuit is faulty. If the voltage at the cells rapidly rises to 67V+ then the cells have a problem. The only simple test of the cells themselves I can think of is to put a controlled load on them, the obvious one being 5 car headlight bulbs in series, 24W bulbs would consume 2A at 60V. (They will get hot enough to burn so be careful) a fully charged battery of 137Wh should last an hour down to 48V and the BMS should have no problem handling 2A if it is OK.

[Jug]

15 minutes ago, Keith said:

I.e directly on the cells without the BMS in the way, measure the voltage and then connect the charger through the BMS. The current can only drop once the charger reaches full voltage of 67.2 to 68V. (Depending whether it stops at 4.2 or 4.25V/cell). If the charger goes green but the battery is still at 61V then the BMS charging circuit is faulty. If the voltage at the cells rapidly rises to 67V+ then the cells have a problem.

Thanks @Keith i will try this measuring method tomorrow because i already assembled my euc, and it is late to do that now. 

I will post result when done! 

[Jug]

@Keith,

Here are result, i attached multimeter on the end of battery bypassing BMS, i had reading of 61V

than i connected charger, charger stay green and the battery was changing from 61.0V to 60.9 every second!

So is that mean the BMS is doomed?

[Jug]

@Keith i measured now cell by cell and all of them are around 3.85V - 3.83V, just one of them are 3.78V!

But i think you already know that they are in pairs in parallel 

[Keith]

@Jug, 

Based on your finding that the charger works fine with another similar pack then yes that would suggest the charge circuit in the BMS is not functioning correctly. It looks like it is preventing the charge voltage reaching the pack.

Silly thought, could this just be a connection issue rather than a fault? I notice that one picture of the BMS shows the position for a Diode which doesn't seem, in your picture, to be populated (?)  is that the BMS you are using? I'm guessing, as I can't see a lot of detail but could this be the position for a charging protection diode ( to prevent discharge if the charge socket gets shorted) if so it would either need a suitable diode or those two terminals may need shorting?

If with the charger connected you can see charger voltage one side of that diode position and battery voltage the other it could be the problem.

Note: A diode will drop 0.6V which the charger would have to allow for, so whether or not you have a diode in the charge circuit could be optional.

[Jug]

8 minutes ago, Keith said:

@Jug, 

Based on your finding that the charger works fine with another similar pack then yes that would suggest the charge circuit in the BMS is not functioning correctly. It looks like it is preventing the charge voltage reaching the pack.

Silly thought, could this just be a connection issue rather than a fault? I notice that one picture of the BMS shows the position for a Diode which doesn't seem, in your picture, to be populated (?) - I've ringed it below - is that the BMS you are using? I'm guessing, as I can't see a lot of detail but could this be the position for a charging protection diode ( to prevent discharge if the charge socket gets shorted) if so it would either need a suitable diode or those two terminals may need shorting?

If with the charger connected you can see charger voltage one side of that diode position and battery voltage the other it could be the problem.

I really don't know anything about that, i have two of them "BMS" and on the second one is the same, no diode or bridge, i think if i short that because that is between discharging cables i will short the batteries?!   

Here is better view! 

[Keith]

@Jug, 

If one BMS, wired the same way works OK, then that would confirm it is a fault, so , yes ignore what I said previously ;-)

[Jug]

Just now, Keith said:

@Jug, 

If one BMS, wired the same way works OK, then that would confirm it is a fault, so , yes ignore what I said previously ;-)

No! Sorry, the other BMS i did not used yet, i just send a photo of another one which is still untouched! 

[Jug]

19 minutes ago, Keith said:

@Jug, 

If one BMS, wired the same way works OK, then that would confirm it is a fault, so , yes ignore what I said previously ;-)

Here is the BMS with battery, i made a suggestion on the picture, can that be problem? 

By the way that is the pair of battery which are with less voltage 3.78V

[Jug]

Ok, i just removed batteries from BMS, and tomorrow i will try with other BMS and will see how will that come out!

Thank you @Keith very much for your help, time and suggestions, you helped a lot!   

[zlymex]

1. It's very very difficult to test a BMS alone without batteries installed.

2. Battery voltages should be within 0.05V difference before installed to BMS, better all fully charged. Even the voltages are the same at lower voltages(say 3.70V), serial charge to full may still not all reach to 4.20V at the same time because of capacity difference.

3. Balance circuit functions at a narrow critical region. That is to say, if there are too much difference when cells reach to 4.20V, or there is a moderate output voltage error of the charger other than 67.2V, the balance circuit will not function.

For example, at the connection to BMS, the voltages of the 16 cells are:
4.2V, 4.1V, 4.1V, 4.15V, 4.15V,,,,,,4.15V
After connection to BMS and charging, the voltages of all cells should be rise the same amount because of serial connection and because of the roughly linear capacity-voltage curve. At some point, the voltages become:
4.25V, 4.15V, 4.15V, 4.20V, 4.20V,,,,,,4.20V
They added up to 67.15V so there is still a small charge current from the charger point of view. However, because the first cell has reached to the charge protection point, it will trip the protection mechanism and cut off the charge completely. This will stop the balance function.

Similar analysis will show that of the output voltage(measured by open circuit) of the charger is too high, there is a bigger chance to trip the charge protection before balance circuit function.

Similar analysis will show that of the output voltage(measured by open circuit) of the charger is too low, there is a bigger chance that most of the cell will not reach to 4.20V hence the balance circuit will not function either.

4. How to test that the balance circuit function?
--continue monitor the charge current after the charge light turns to green. It should be dropped gradually and stable to 25mA to 70mA. If the balance circuitry does not function, the current will be dropped to 0 suddenly at some point. When measured by a DC clump meter, the current will never drop to zero.

--continue monitor the charge voltage after the charge light turns to green. It should be raised gradually and stable to 67.1xV. If the balance circuit does not function, the voltage will be rise to 67.2V suddenly at some point. 
--continue charge after the charge light turns to green for more than 3 hours, the battery pack should be warm.
--continue charge after the charge light turns to green for more than 3 hours, disconnect the charger, measure the battery voltage, it should be above 66.9V(that is, within 0.3V difference of the charger output)
--if you have a watt meter, the same thing can be observed: the input power of the charger make difference when plug/unplug the charger at the EUC side(after the charge light turns to green for more than 3 hours)
--charge time become considerably less
--usual riding distance become considerably less(eliminate climate situations)

5. If the balance circuit does not function, there may be four reasons:
---Cell unbalanced. This is the most common situation.
---Bad cell/cells.
---The balance part of the BMS failure.
---Charger failure or output voltage drift.

6. Caution: make sure NOT to short circuit batteries when perform above operations.
 

[dmethvin]

Wow, really good information! Some articles suggest that you do not fully charge to 67.2V in order to extend battery life. If the charger was modified to provide 66V for example, would the BMS still trigger its balancing function when the current went down?

[zlymex]

58 minutes ago, dmethvin said:

Wow, really good information! Some articles suggest that you do not fully charge to 67.2V in order to extend battery life. If the charger was modified to provide 66V for example, would the BMS still trigger its balancing function when the current went down?

Short answer: No.

The balancing function will not be triggered if any of the following is true:
1. batteries already un-balanced to certain degree
2. charger open voltage outside 66.9V to 67.6V
3. stop charge when charger's LED turns green.

[SlowMo]

17 minutes ago, zlymex said:

Short answer: No.

The balancing function will not be triggered if any of the following is true:
1. batteries already un-balanced to certain degree
2. charger open voltage outside 66.9V to 67.6V
3. stop charge when charger's LED turns green.

I have a question. My IPS Zero with 340wh Sony batteries only charges upto 65.58v and registers it a 100% charged so I opened my charger and increased the voltage to 67.2v and now it increased the charge to 66v max. Is this an attempt by IPS to prolong the life of the Sony batteries? I read somewhere that IPS has its own battery management built inside the mainboard.

[zlymex]

5 minutes ago, SlowMo said:

I have a question. My IPS Zero with 340wh Sony batteries only charges upto 65.58v and registers it a 100% charged so I opened my charger and increased the voltage to 67.2v and now it increased the charge to 66v max. Is this an attempt by IPS to prolong the life of the Sony batteries? I read somewhere that IPS has its own battery management built inside the mainboard.

Was 65.58V and 66V measure during the charge or when charger disconnected? 
Was 65.58V and 66V  measure by app or by a multimeter?  If later what brand?

Anyhow, reduce from 67.2 to 66V won't extend the batteries life much.
Indeed IPS has its own BMS on the mainboard and it seems to be good design except the balancing current is a bit small.

[SlowMo]

1 minute ago, zlymex said:

Was 65.58V and 66V measure during the charge or when charger disconnected? 
Was 65.58V and 66V  measure by app or by a multimeter?  If later what brand?

Anyhow, reduce from 67.2 to 66V won't extend the batteries life much.
Indeed IPS has its own BMS on the mainboard and it seems to be good design except the balancing current is a bit small.

It's during charge and measured by the Iamips app.

[zlymex]

2 minutes ago, SlowMo said:

It's during charge and measured by the Iamips app.

In that case, don't believe them.

[SlowMo]

Just now, zlymex said:

In that case, don't believe them.

I just wonder why the open voltage of the IPS charger measured less than 67 volts using the multimeter.

[zlymex]

2 minutes ago, SlowMo said:

I just wonder why the open voltage of the IPS charger measured less than 67 volts using the multimeter.

Might be the error from the  multimeter. I use Fluke 289 and Metra Hit 30M

[SlowMo]

6 minutes ago, zlymex said:

Might be the error from the  multimeter. I use Fluke 289 and Metra Hit 30M

Thanks. I guess I need to invest on a quality multimeter to get proper measurements.  But now I am a bit worried that I might have over adjusted the open charge voltage. 

[Jug]

13 hours ago, zlymex said:

--continue monitor the charge voltage after the charge light turns to green. It should be raised gradually and stable to 67.1xV. If the balance circuit does not function, the voltage will be rise to 67.2V suddenly at some point. 

@zlymex, Thank you very much for explanation! 

I changed yesterday the BMS, the batteries was in range 3.83V to 3.85V after all putting together i charged that pack until charger turned green, i had 67.2V on voltmeter.

Today when i checked it after my job the voltage was 66.6V, i readed your post here and i connected charger, the charger turned green after few minutes, on the discharging cable i have readings of 67.6V from the begin of charging (when it was red and with green light on charger) 

and also i have now 002 to 003 (don't know what exact amperage is this?!) when my multimeter is set on 2000µ 

So i think it still charge and work the balancing thing? 

[EnPagés]

Hello everyone! This is my first comment and I'm not very sure if this is the better place but... here we go:

I'm the proud owner of the new Gotway MCM4 260Wh since two weeks. Everyday I ride up a street (or climb) near 25-30% inclination and 1km long. When the battery it's full there's no problem to drive fast 18-20km/h but if the batteries it's 50% it's impossible to drive more than 8-10km/h.

I imagine this can be solved with an extra (parallel) battery, because my MCM4 has one side empty (I want to instal a little GPS tracker inside but this goes in the MODs). My question is about this second battery:

Option one, buy another (and very expensive) Gotway Battery 260Wh 10Ap 2200Ma, Sony 32p. Following the recomendations of @esaj to get the same kind of batteries.

Option two, I found different Battery Packs and with different prices also... But almost all are Samsung except this It's (hope it's legit one) Sony:

http://www.alibaba.com/product-detail/60V-4-4ah-16S2P-high-rate_1857348742.html

My second question about this battery and the High Rate Discharge: After reading a lot, I thing the Original Battery from Gw it's made with Sony V3, this one according the indications it's VTC3. Can this High Rate damage or descompensate or give me problems with the Original Battery pack?

Can this battery with the double Ma give me a powerfull response when Im climbing? or otherwise I can overheat or shortcut something?

Thank you for your help in advance!

Note: my electronic knoledge it's elementary and this is my first EUC

[zlymex]

9 hours ago, Jug said:

@zlymex, Thank you very much for explanation! 

I changed yesterday the BMS, the batteries was in range 3.83V to 3.85V after all putting together i charged that pack until charger turned green, i had 67.2V on voltmeter.

Today when i checked it after my job the voltage was 66.6V, i readed your post here and i connected charger, the charger turned green after few minutes, on the discharging cable i have readings of 67.6V from the begin of charging (when it was red and with green light on charger) 

and also i have now 002 to 003 (don't know what exact amperage is this?!) when my multimeter is set on 2000µ 

So i think it still charge and work the balancing thing? 

I think the cells are in good balancing condition and the balancing circuitry works although 66.6V is a bit low and 67.6V is a bit high.

[zlymex]

9 hours ago, EnPagés said:

Hello everyone! This is my first comment and I'm not very sure if this is the better place but... here we go:

I'm the proud owner of the new Gotway MCM4 260Wh since two weeks. Everyday I ride up a street (or climb) near 25-30% inclination and 1km long. When the battery it's full there's no problem to drive fast 18-20km/h but if the batteries it's 50% it's impossible to drive more than 8-10km/h.

I imagine this can be solved with an extra (parallel) battery, because my MCM4 has one side empty (I want to instal a little GPS tracker inside but this goes in the MODs). My question is about this second battery:

Option one, buy another (and very expensive) Gotway Battery 260Wh 10Ap 2200Ma, Sony 32p. Following the recomendations of @esaj to get the same kind of batteries.

Option two, I found different Battery Packs and with different prices also... But almost all are Samsung except this It's (hope it's legit one) Sony:

http://www.alibaba.com/product-detail/60V-4-4ah-16S2P-high-rate_1857348742.html

My second question about this battery and the High Rate Discharge: After reading a lot, I thing the Original Battery from Gw it's made with Sony V3, this one according the indications it's VTC3. Can this High Rate damage or descompensate or give me problems with the Original Battery pack?

Can this battery with the double Ma give me a powerfull response when Im climbing? or otherwise I can overheat or shortcut something?

Thank you for your help in advance!

Note: my electronic knoledge it's elementary and this is my first EUC

Welcome here!

Both battery pack will do but you need to check the thickness of the pack from Alibaba which seem to me that the BMS is thicker than usual being with an aluminium heat-sink.

The high discharge rate pack is good, it will ease the loading of existing pack and make the whole thing more powerful together with the old pack. You may need a Y-connector if adding a second battery pack which can be purchased or DIY.

Parallel battery packs of mixing brand cannot be regarded as bad idea. I had two different types of packs in parallel for my T260(240Wh Chinese brand battery), Sanyo and Panasonic and they live together very well for more than a year.

[Chriull]

On 11.1.2016 at 6:11 PM, Jug said:

Here is the BMS with battery, i made a suggestion on the picture, can that be problem? 

By the way that is the pair of battery which are with less voltage 3.78V

Seems that noone answered to your question till now - or did i miss a posting?

Definitely - if you introduce new connections by your soldering you change the way the BMS can/will work + you could shortcut cells (think you did not by now - you would have noticed immediately). Could be that you had good luck - the green stuff on the traces of the PCB is "solder resist" and isolates the traces (a bit..) However you should in any case repair all such things!

And you want to use less solder ( https://learn.adafruit.com/adafruit-guide-excellent-soldering/common-problems ) - the BMS in combination with the batteries is quite a safety critical part. I would try to build it up carfully and as perfect as possible...

Edit.: The overlap you show on the picture would be a shortcut of the battery cell(s) 16. Since the PCB traces are not molten you have no shortcut by now. But a minor scratch by vibrations etc could lead to one!

Repairing this situation could again lead to a shortcut of this cell. Too much heat or scratching could destroy the "solder resist" (green "layer" on the trace) and it would not isolate anymore. So you should do this very carefully! Maybe you could remove the battery cell 16 before this in some way?

Edit2: You could unsolder the connection at B16+ first and then repair the situation at B16-. Should be imho the safe(r) way to go...

PS.: At "B13+" you have a small ball of solder lying around. This could be held loosely by some soldering flux - you should remove this too, since it will loosen itself over time and then you have a conductive piece moving around your BMS...