One for the battery experts- new pack - strange problem- Any advice?

[eddymunster]

Decided to order up a new 48v softpack fom a well established supplier via ebay 48v 12ah 30a bms. The good news was it arrived early and is nice and light- 3 kilos.
However when checking the state of charge on arrival nothing doing on the leds, out with the voltmeter 2.4 volts. Bit odd so put it on charge on wednesday and after 6 hrs according to my charger we are good to go with 54.6 volts. email supplier to check shipped voltage and its 30% soc and don't read too much into the intial reading as its a smart bms and would be in sleep mode. Checks this morning prior to going for a wobble and we are on 53.8 so its lost a touch since wednesday.
Off we pop, 4.5 mile in and the display goes off and with it any assistance, very odd never done that before. About half a second prior to this a had a look at the display and had 47.2 volts. At the time I was only pulling 5amps out the pack on the flat in pas 3. For information it's a bbs02b 750w - 20 amp set on the controller with a 42lvc. Walk of shame home- check the led on the pack 50%, check the voltage again 2.4volts.
Anyone have any ideas- I have a gut feeling this is could be BMS related rather than the cell pack itself due to the nature of the fault, cannot see how we lose 40 odd volts so quickly. The pack itself wasn't hot and niether was the motor when i pulled over. Decent cells Samsung 40t 21700.
Awaiting reply from supplier but this is in case I have to sort it myself as I changed the connector to a spark arrestor xtc90 and this causes a warranty issue- they only give a month by the look of things.
So any advice on the fault/ diagnostic checks or recommendations for a good 30amp bms supplier

thanks

eddy

 

[Andy-Mat]

Decided to order up a new 48v softpack fom a well established supplier via ebay 48v 12ah 30a bms. The good news was it arrived early and is nice and light- 3 kilos.
However when checking the state of charge on arrival nothing doing on the leds, out with the voltmeter 2.4 volts. Bit odd so put it on charge on wednesday and after 6 hrs according to my charger we are good to go with 54.6 volts. email supplier to check shipped voltage and its 30% soc and don't read too much into the intial reading as its a smart bms and would be in sleep mode. Checks this morning prior to going for a wobble and we are on 53.8 so its lost a touch since wednesday.
Off we pop, 4.5 mile in and the display goes off and with it any assistance, very odd never done that before. About half a second prior to this a had a look at the display and had 47.2 volts. At the time I was only pulling 5amps out the pack on the flat in pas 3. For information it's a bbs02b 750w - 20 amp set on the controller with a 42lvc. Walk of shame home- check the led on the pack 50%, check the voltage again 2.4volts.
Anyone have any ideas- I have a gut feeling this is could be BMS related rather than the cell pack itself due to the nature of the fault, cannot see how we lose 40 odd volts so quickly. The pack itself wasn't hot and niether was the motor when i pulled over. Decent cells Samsung 40t 21700.
Awaiting reply from supplier but this is in case I have to sort it myself as I changed the connector to a spark arrestor xtc90 and this causes a warranty issue- they only give a month by the look of things.
So any advice on the fault/ diagnostic checks or recommendations for a good 30amp bms supplier

thanks

eddy

I don't know what your problem is, sorry, but I still have a good tip for your comment:-
"Awaiting reply from supplier but this is in case I have to sort it myself as I changed the connector to a spark arrestor xtc90 and this causes a warranty issue- they only give a month by the look of things. "
I make myself a small adapter cable, it costs very little and it means (as in your case too), I keep the full guarantee each time. It just costs one plug or socket more and a short piece of cable....Use quality parts of course!
Regards
Andy
PS. I would (wildly) guess the BMS as well, and they are not expensive, and maybe they will replace it if you send them just that.....Are you electrically "proficient" enough? There are some good videos on the Internet that could help, especially ones where people make their own battery!

 

[eddymunster]

Fitting bms shouldn't be a problem, built ecu's from scratch for motorcycle and car applications, hoping that supplier will send one out rather than ship back as the charges for shipping would be the same as the bms.

 

[vfr400]

2.4v means that the BMS has shut off. You have to find out why by measuring the voltages on the sense wire connector. Do it when the BMS has shut off, not after charging. When we have the results, we should have a good idea where the problem lies.

The voltage reduction from 54.6v to 53.8v could be normal - probably due to bleed resistors doing their job - though it does look a bit on the low side. I would have expected about 54.2V.

 

[Michael Love]

I would say the parallel sides of the battery pack are not connected. Leaving only one side at 1600maH approx, or whatever each of the cells are rated at, but at the correct voltage when charged ergo, you get to ride it for a bit before it dies

 

[eddymunster]

After a reply from the vendor last night of its probably not the battery I am going to plan b- refit my old battery which is a known good one and see if it all fires up- no issues until yesterday. Thanks for the info on the BMS Andy = I was going to go down the road of charging it up again. But what you said makes more sense- due to work it will be later in the week[/QUOTE]

 

[vfr400]

After a reply from the vendor last night of its probably not the battery I am going to plan b- refit my old battery which is a known good one and see if it all fires up- no issues until yesterday. Thanks for the info on the BMS Andy = I was going to go down the road of charging it up again. But what you said makes more sense- due to work it will be later in the week

Your nuts if you listen to either of those two. Do the tests and you'll know what's wrong.

 

[Andy-Mat]

After a reply from the vendor last night of its probably not the battery I am going to plan b- refit my old battery which is a known good one and see if it all fires up- no issues until yesterday. Thanks for the info on the BMS Andy = I was going to go down the road of charging it up again. But what you said makes more sense- due to work it will be later in the week

[/QUOTE]
On this Forum there are both great many good normal people and a few, "know-all" rude people.
So to be safe, please simply judge for yourself exactly who has a "personality" problem.
Then my recommendation is to simply ignore those who are rude, either to you and/or others here. That will stand you in good stead in the long term......
If I am able to assist you any further, please ask.
regards
Andy

 

[eddymunster]

update- fitted my old shark pack and back in business - went for a 15 mile ride so email fired to vendor to see were we are going to go with this. will name and shame if I don't get a positive outcome. so far the moral of the tale is I should have stuck with Jimmy the old pack gave no trouble whatsoever
if they ok for me to test pack and don't give me the you invalidated w/t -happy days
if not I might end up with a rather expensive paperweight if its the cell pack!!

 

[eddymunster]

Your nuts if you listen to either of those two. Do the tests and you'll know what's wrong.

Just had an email from vendor and wanted me to charge up again and check voltage after 24hrs- seems pointless, so lifted the wrap back, its a softpack, to check sense wires, and its been fitted with a 15s 30amp bms, 17 wires in total,checked voltage at b- to pos=45.9 volts.
so my next question is 1- is this accepted practice.
2-how do I go about check the sense wires.
3- if this is 15s would the lvc point threshold not be higher voltage and this is the reason it shut down or can this be programmed to suit 13s.?
any help appreciated.

 

[vfr400]

Unplug the sense wire multi-pin connector, put your black probe on B-, where the black wire from the cell-pack joins the PCB, then probe each pin in the connector with the red probe. record all the voltages, then you can see/calculate the cell voltages.

 

[eddymunster]

Unplug the sense wire multi-pin connector, put your black probe on B-, where the black wire from the cell-pack joins the PCB, then probe each pin in the connector with the red probe. record all the voltages, then you can see/calculate the cell voltages.

on checking the voltages at the sense wires from BO- B1=3.83,B2=7.64, B3=11.64,B4=15.28, B5=19.10, B6=22.80, B7=26.70,B8=30.50,B9=30.50,B10=34.30, B11=34.30, B12=38.30,B13=42.20,B14=42.20,B15=46.0. So the voltage on the pack looks good, the lowest cell works out at 3.7 and the highest 4.0 the rest are 3.8 or thereabouts. B8/B9, B10/B11 and B13/B14 are wired into one cell group each. Also checking the voltage on B- to the red discharge lead the voltage has gone 0.4 of a volt. I have a feeling this BMS has the LVC for a higher voltage pack maybe 58/63 volts with it being 15s as the pack is a 13s pack. the vendor advertises this as a smart bms so is it programmable and how.
anyones thoughts?

 

[Nealh]

If B8, B10 & B13 are linked I still only count 12 readings ?

 

[vfr400]

Did you place your black probe on the cell-pack negative wire, like I explained, or on the B0 position?

Don't invent reasons you think that the battery is faulty. Instead, let the results tell you what's wrong.

We should see a list of 13 results, which will enable us to determine the 13 individual cell values. We don't have that at the moment. There are only 12.

Even the values that you have given us show that all is not as good as it should be. 0.3v difference between different cell groups is more than what I'd expect to see, but don't judge anything until we see all 13.

"Also checking the voltage on B- to the red discharge lead the voltage has gone 0.4 of a volt". I can't make any sense out of that. Can you explain what you mean?

 

[eddymunster]

Went from B0 on the sense wire, will recheck again tomorrow night, I take it I should be going from B- on the bms board then. sorry in regard to the other reading of the overall pack voltage, it went up 0.4 volts, b- to red on the discharge lead when the sense wire was unplugged.

 

[Nealh]

Yes, Black probe on BMS B- which is the pack B-.

 

[eddymunster]

Rechecked the pack tonight from B-, the voltages at the sense wires are now B0= 0 BB1=3.81,B2=7.64, B3=11.46,B4=15.28, B5=19.09, B6=22.80, B7=26.70,B8=30.50,B9=30.50,B10=34.30, B11=34.80, B12=38.60,B13=42.40,B14=42.40,B15=46.3. Big fluctuation, B11 stands out at 0.5 volt. Treble checked.

little information regarding yesterdays test- I tested the pack voltage prior to removing the bms plug it was 45.9 volts. I checked my readings twice starting at b15 and working back to b1 then from b1 to b15 and got the yesterdays posted values- I wrote a grid up at the time and used this tonight - same methodology. By the look of things I should have done this yesterday as my final test was to recheck the overall voltage which had crept up 46.3.
So we seem to have 13 readings- one of which is far from right, and that b8/b9 and b13/14 are wired together. So advise on what to do now really?
Vendors advice is to put on a 24hour charge?

 

[Nealh]

B11 parallel group is toast at 0.5v is fit for the tip or recycling, it is not safe to try and recover it and will always be a weak link.
Your battery based on the first cell count of 3.81v should be near 50v if it was good.

Vendors advice is bo**ocks, I doubt they will have clue or even know much about how battery systems work. The BMS simply will not allow charging as B11 is far away below LVC, if the cell group was 2.5v then possibly it may have been recoverable with 500mah 5v old phone charger. Tbh the BMS is likely at fault and should really be a proper 13s model and not a 15s buggered to work and act like a 13s.

 

[vfr400]

Something is wrong with the cell-group attached to B12. As a first step, I'd charge that group up to 3.8v on their own. You can use something like this plugged into the B10 and B11 slots.

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You can use any old USB or phone charger with a voltage from 3.8 to 5v, but if you use one above 3.8v, you need to monitor the cell voltage while it charges and make sure that you switch off at 3.8v.

Try it like that, and if the battery gives further problems, do all these tests again, and if you get the same or similar result, you need to repair that cell-group.

I'm not saying Neal is wrong. It's recommended advice, but if were my battery I'd try and recover it unless the seller is going to refund me. It's not ideal, but I have successfully recovered batteries like that before. If you had 0v on that group, I'd chuck it. Although 0.5v looks very low, it's a microscopic amount of charge below 2.5v because the discharge curve is nearly vertical below 2.5v.

 

[Nealh]

If it was my battery and carried no warranty from the seller, I would try a manual cell group charge to see if the cells would hold a charge.
In this case it sounds like Eddy may have some redress with the vendor first, so I believe he should go down that route first with them first before messing with the battery. The vendor has asked him to put it on charge for 24hrs but as we know the bms won't play ball with a cell group below lvc, I guess he needs to do as the vendor ask's for them then to act to try and rectify/replace the battery.