Help! Intermittent fault on battery - causing loss of power

[trevor brooker]

https://www.pedelecs.co.uk/forum/threads/power-cutting-out-on-bbshd.35681/
My previous thread was trying to find the fault - & suggestions lead me to firstly check the battery. As it was an intermittent fault, the only reliable way was with a replacement battery, which I purchased, & has allowed me to become fully mobile again.

I am now left with a faulty battery. On purchase it was described as
52 V 17.5Ah: Panasonic/Sanyo GA cells in 14 series, 5 parallel configuration.
The Panasonic 18650 GA cell is rated at 10A output (max), storage capacity of 3500 mAh (max)
5 parallel x 3.5ah = 17.5Ah 14 series x 4.2v = 58.8v

Suggestions were made to
fix any sense wires that were pinched - done see photos
check that battery cell welds were not loose - done

I'm now at the point of thinking its time to replace the BMS.

the existing one is marked as bmc 14s 30a
the battery case has an on/off switch & usb power take off.



Can anyone provide a link to a BMS I could purchase similar to the existing one.

When I have looked at ebay & AliExpress they do not seem to come with an on/off switch.

The cells are holding power & still balanced. With no draw (minimal for the display) the power remains for hours. When using the PAS or throttle the battery loses power at loads from 150w to 1000w. If it was just at high load it would provide a clue but it also happens at 150w.

Hence my thought about a replacement BMS.

The bike on the new battery is working fine.

 

[KirstinS]

Just to check did you lift all the red card and check the welds like that ?

 

[trevor brooker]

Just to check did you lift all the red card and check the welds like that ?

lifted the red card, used a lolly stick to ping the welds, all felt fine

 

[vfr400]

14S BMS 58.8V Li-ion battery with Charge port protection and Switch function 40A | eBay

Find many great new & used options and get the best deals for 14S BMS 58.8V Li-ion battery with Charge port protection and Switch function 40A at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

 

[trevor brooker]

14S BMS 58.8V Li-ion battery with Charge port protection and Switch function 40A | eBay

Find many great new & used options and get the best deals for 14S BMS 58.8V Li-ion battery with Charge port protection and Switch function 40A at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

many thanks

 

[vfr400]

I was wondering if the 30 amps on your present BMS is a bit marginal for the BBSHD. I'd want more headroom than that. It could be cutting out due to over-current or over-heating.

If you get the new BMS, you have to check your sense wire connector carefully. The Ebay one has pins B1 to B14 (14 pins) marked, but the picture isn't clear where the ground is. There is no standard for the pin arrangement. Some go B1 to B13 and pick up the ground and B14 from the main power wires, then you can have B0 to B14 (15 pins) or B0 to B13 (14 pins) with B14 picked up from the main power wire.

You need to check which sense wire goes to which pin on your present setup, then adjust the new one to suit. It could be that they're identical.

One other important thing: Sometimes, the direction is opposite You might find that you're lucky enough to have the same connector with the same pin arrangement, but you have B14 to B1 instead of B1 to B14, so you have to cut the connector off and rejoin all the wires with it flipped, which is a bit of a pain. I would say that in 70% of cases, I've had to cut the connector off the cell pack and solder the wires from the one that comes with the BMS from first principles because the connector had a different number of pins, was a different type or the direction was reversed.

In summary, you have to check the pin arrangement. Hopefully, they'll be the same.

 

[trevor brooker]

In summary, you have to check the pin arrangement. Hopefully, they'll be the same.

I am finally ready to solder the new BMS.
I'm quite happy about the C P & B wires - straight replacements.
But reading through everything again before I started I was not sure I had understood everything you has said.
My existing balance harness plug goes red to white to black. The cumulative voltages left to right decrease (follow link on 1st post)
The new BMS goes red to white to black & B14 to B1
So I think its the same & as the plugs are interchangeable I will not need to replace the balance harness.

 

[vfr400]

It's dead easy if you go by the measured voltages. You must use the cell-pack ground for your black probe, not the first pin or wire, then put your red probe on each sense wire in turn.

0v goes to B0 if it has one
Approx 4v goes to B1
8v to B2
etc.
and 56v goes to B14 .

 

[trevor brooker]

You must use the cell-pack ground for your black probe,

Can I please clarify is the cell-pack ground is where the B wire connects to the battery?

 

[vfr400]

Can I please clarify is the cell-pack ground is where the B wire connects to the battery?

Yes or where it connects to the BMS.

 

[trevor brooker]

Well I managed to replace the BMS & soldered the XT60s onto the battery frame leads this morning.
Whilst the bike was on the frame checked that it all worked fine.
However as soon as went down the road the fault reappeared.
So its not the on/off switch, pinched wires, BMS so I am left with a poor weld, which would cost too much to either buy a welder or send for professional repair.

 

[KirstinS]

Well I managed to replace the BMS & soldered the XT60s onto the battery frame leads this morning.
Whilst the bike was on the frame checked that it all worked fine.
However as soon as went down the road the fault reappeared.
So its not the on/off switch, pinched wires, BMS so I am left with a poor weld, which would cost too much to either but a welder or send for professional repair.

Sorry to hear this but a bad connection whereever it is can be diagnosed and fixed cheaply although can be time consuming

I have repaired many broken welds with soldering iron. Doesn't have to be welded

 

[trevor brooker]

Sorry to hear this but a bad connection whereever it is can be diagnosed and fixed cheaply although can be time consuming
I have repaired many broken welds with soldering iron. Doesn't have to be welded

That's heartening - I have the time, just not the knowledge.
Voltage on the cells has not changed.
Are you able to suggest what to test to find the fault that is causing the BMS to do its job & shut the power off?

 

[vfr400]

General advice: Whatever problem you have on any bike, you test and measure to find out where the problem is. If you just replace random parts, you will never find the problem. Never replace anything unless you know it to be faulty by testing or inspection.

Wire a pair of flying leads to the cell pack so that you can monitor its voltage while you have the problems. If it doesn't show anything, move the monitoring point to the output side of the BMS. If that doesn't show anything, it's not the battery, so move it to the controller supply wires and so on.

 

[trevor brooker]

General advice: Whatever problem you have on any bike, you test and measure to find out where the problem is. If you just replace random parts, you will never find the problem. Never replace anything unless you know it to be faulty by testing or inspection.

Wire a pair of flying leads to the cell pack so that you can monitor its voltage while you have the problems. If it doesn't show anything, move the monitoring point to the output side of the BMS. If that doesn't show anything, it's not the battery, so move it to the controller supply wires and so on.

I'm sure its the 52v battery as for the last two months the 52v battery has been off the bike, pending repair, whilst I have used a replacement 48v battery for a total of 29 journeys covering a total of 383 miles without problems.

Today when I thought I had repaired the 52v battery & fixed it to the bike it suffered the same problems.

I then replaced it with the 48v battery & was able to complete my journey without incident.

So I think I have identified the faulty part as the battery, as with a replacement battery the bike performs normally.

 

[Nealh]

You will need to uncover the battery cell ends completely on both sides and take good pics. It might be a weld so using a pointed wooden kebab or lolly stick, place under each weld and gently see if any lift. If all is ok then a cell or two may have gone bad in a Parallel string, you can measure each cell voltage to see if any are bad.
Check the discharge wire solder joints at the battery to make sure they are good.

 

[vfr400]

You will need to uncover the battery cell ends completely on both sides and take good pics. It might be a weld so using a pointed wooden kebab or lolly stick, place under each weld and gently see if any lift. If all is ok then a cell or two may have gone bad in a Parallel string, you can measure each cell voltage to see if any are bad.
Check the discharge wire solder joints at the battery to make sure they are good.

He shouldn't need to do that. Cell voltage measurement after the battery cuts should indicate any abnormalities, so he would know where to check for the solution.

 

[trevor brooker]

You will need to uncover the battery cell ends completely on both sides and take good pics. It might be a weld so using a pointed wooden kebab or lolly stick, place under each weld and gently see if any lift. If all is ok then a cell or two may have gone bad in a Parallel string, you can measure each cell voltage to see if any are bad.
Check the discharge wire solder joints at the battery to make sure they are good.

Finally got around to measuring the cell voltages, using the balance harness plug
1 -0v
2-3.8v-3.8
3-7.7v-3.9
4=11.5v-3.8
5-15.4v-3.9
6-19.2v-3.8
7-23.1v-3.9
8-27.0v-3.9
9-30.8v-3.8
10-34.6v-3.8
11-38.5v=3.9
12-42.4v-3.9
13-46.2v-3.8
14-50.1v-3.9
15-54.0v-3.9
I never charged up using this BMS but cells still within 0.1v of each other

"discharge wire solder joints at the battery" look fine

"uncover the battery cell ends completely on both sides and take good pics"
next job

 

[Nealh]

The balance voltages with the battery being part discharged isn't too shabby, though doesn't rule out the possibility of a bad cell or two in the P groups.
Not teaching how to suck eggs, I see you using a screw driver to lift the wire. I never use any metallic objects other then necessary and always use plastic levers or wooden lolly/kebab sticks they help to prevent unexpected bangs and shorting of cells.

 

[vfr400]

I'm thinking now that it's probably something outside of the BMS and cell-pack. Check all the solder joints on the main terminals and check the terminals for signs of burning or anything like that.