Help! bbshd ,battery? issue

[minexplorer]

hi.i have a 15ah 52v samsung 30Q battery on my bbshd. In the programming The low voltage cut out was set to 41v. Electron cycles assured me this still wouldnt harm the battery even tho its lower than a more usual 45v for a 52v batt. Anyway 1500 miles of use so far. When The voltage shows around 41v on the display the bike cuts out.So far so good. Then yesterday 8 miles from home id just got to the top of a steep hill on full power and the bike turned off. Turned back on the display was showing 47.2v !!! I managed to limp another mile or so on lower power 6-8amps it shut off a couple times and thats all. display showing around 45.6v when cuts out and wont go another cpl yards before turning off.

ive checked the display voltage it had changed to 36v ,put it back on UBE but makes no difference. programming is still 41v LBC. ive wiped and re flashed my programming settings.Still wont go 2 yards before shutting off with voltage reading around 45.8v.

Im baffled i consistently get 25-27 miles by the time it gets down to 41v. if im conservative with the power. yesterday only 19 miles. It was a long ,long mostly uphill walk home. These bbsxx are a knee breaking nightmare to pedal without assistance unless absolutely flat.

Could it be the battery BMS faulty or overiding the programming? Much appreciate any advice ,thanks

 

[danielrlee]

Possibly a low cell group causing the BMS to cut power. Have you left the battery on a long charge to balance fully since the cutout started?

 

[minexplorer]

Possibly a low cell group causing the BMS to cut power. Have you left the battery on a long charge to balance fully since the cutout started?

hi danial.it only happened yesterday for the first time.i hadnt used it for cpl weeks.im in the habit of keeping it near fully charged when not in use and when i charge it i often leave it on for hours after full charge is reached to ensure balancing.it always charges to 58.2-58.4v. i know its not ideal but i always go as far as i can. so quite often the battery runs out to the 41v point it cuts out,which is often a mile short of home.

 

[danielrlee]

hi danial.it only happened yesterday for the first time.i hadnt used it for cpl weeks.im in the habit of keeping it near fully charged when not in use and when i charge it i often leave it on for hours after full charge is reached to ensure balancing.it always charges to 58.2-58.4v. i know its not ideal but i always go as far as i can. so quite often the battery runs out to the 41v point it cuts out,which is often a mile short of home.

I'd still start by giving the pack a full charge, allowing for a long balancing period overnight. Also, check the charger to ensure that it's still outputting the expected voltage, somewhere around 58.8V.

 

[vfr400]

It makes absolutely no sense to set your LVC to 41V. That's just asking for problems, and it's completely unnecessary. There's hardly any difference in charge between a more normal 43.4V and 41V. it might get you a couple of hundred metres at most. Even when your battery is at 45.8V, there's not much charge left in it and it'll sag a lot, which is probably why it keeps cutting out.

Balance is easy to check. all you have to do is measure the voltage as soon as you take it off charge. The further the voltage is from 58.8V, the more out of balance it is.

 

[trevor brooker]

QUOTE./ Balance is easy to check. all you have to do is measure the voltage as soon as you take it off charge. The further the voltage is from 58.8V, the more out of balance it is.[/QUOTE]

Ok - I have a similar battery, but it is mainly charging to 57.6v, but charger output is 58.8v. I connect the charger, which then turns itself off at say 57.6v, & does not charge again, even if left for several hours. But once every four months it charges to 58.8v. I alternate between two different chargers, which both do the same.

Is this the BMS playing up?

 

[vfr400]

No. It sounds like the BMS doing its job. It should switch off when the first cell reaches around 4.25V, so you probably have balance issues. The only way to be sure is to open it and check the voltages on the multi-pin connector to the BMS.

The BMS will also switch off when the first cell reaches around 3.0V, which could account for why it switches off at 45.8V.

 

[minexplorer]

It makes absolutely no sense to set your LVC to 41V. That's just asking for problems, and it's completely unnecessary. There's hardly any difference in charge between a more normal 43.4V and 41V. it might get you a couple of hundred metres at most. Even when your battery is at 45.8V, there's not much charge left in it and it'll sag a lot, which is probably why it keeps cutting out.

Balance is easy to check. all you have to do is measure the voltage as soon as you take it off charge. The further the voltage is from 58.8V, the more out of balance it is.

the controller was programmed by electron cycles for the 52v at 41v LVC.when i questioned this low setting they said it would do no harm and it was to allow a little bit more range. yes i did notice it would only make another cpl miles or so between 45v and cutting out at 41v.but as i was always pushing the bike as far as i could it seemed a good idea at the time to leave it that way.

i will change it to say 44v LVC. But i couldnt understand why its suddenly no longer going below 45v even when still set to 41v. thats even when only pulling maybe 5 or 6 amps on pas1. So its out of balance then.

Even if i leave it a on charge several hours after charger has gone green it never shows more than 58.4v . the chargers fan has just stopped and gone green.the battery is reading 57.9v never been that low before.the charger reads 58.5v. it says 58.8v on the back. i will leave it on overnight see what it reads.none of my 36v (lvc 31v)batteries ever charge beyond 41.2-41.5v either. i have just checked their chargers and they read 41.3v and 41.5v and say 42v on the back.

Does this mean the chargers are slightly worn? ive tested with 2 different meters .What sort of time does a full balance take,a whole day? thanks

 

[vfr400]

As I said, you have to open the battery and measure the voltages on the multi-pin connector.

 

[minexplorer]

As I said, you have to open the battery and measure the voltages on the multi-pin connector.

will do that tomorrow.ive done it once before on a 36v because it wouldnt charge much beyond 41v. they were all the same. now ive just discovered that batterys charger only goes to 41.5v. thanks

 

[peter.c]

The battery load stress on the cheap laptop style chargers does not help or no glue on the v adjustment pot when it was tweaked

 

[Benjahmin]

If using cheap dvm's then they are uncalibrated, i.e. they haven't been checked against a known source. So the difference between a measured 41.6v and stated 42v is within an error factor. What I would be looking for is for the charger output and final battery charge voltage to be the same with the same meter. For instance, I have a brand new battery which, according to two dvm's I have, charges to either 41.5 or 41.6 - depending which meter I use. However the charger output measures the same. So I have to assume that the battery is charging fully and meter error is an issue.
All that said is does sound like you have sag issues.

 

[Nealh]

Going to 41v is low and just above 2.9v per cell, ideally 3.2v is the min you should try and aim for.

 

[minexplorer]

Going to 41v is low and just above 2.9v per cell, ideally 3.2v is the min you should try and aim for.

yeah im gonna set it to 44v but first to leave it plugged in to balance for 24hrs .so far 10 hrs of balancing hasnt raised the voltage a jot,still 58v.half a volt less than the chargers output.

 

[Nealh]

If one cell string is out of kilter and say 0.4 - 0.6v out of balance then it won't balance straight away and may even remain out of balance after several full charges.
Could also be that you need to check all 14 cell string voltages via the BMS JST connection and if necessary raise any strings that are low. The bms will generally keep cell strings balanced but they will need to be quite close to begin with.

 

[minexplorer]

If one cell string is out of kilter
raise any strings that are low. The bms will generally keep cell strings balanced but they will need to be quite close to begin with.

Thanks neal,how do i raise any that are low .i know how to check the voltage on them but no idea how to manually raise one if a 24hr on charger hasnt managed it.

ive always understood you should have the battery OFF when charging. With the battery off.reads 58.6v at the terminals with the charger attached.Although charger is on it doesnt 'RUN'. As soon as i detatch it and switch the battery on its still only 58v at the terminals,after many many hrs. If i switch the battery on while the charger is attached,then the chargers fan starts and the voltage drops at the terminals a little from the 58.6v. if i then detach it after a few seconds and check battery voltage,it momentarily reads a little over the 58v. its as if the charger will put more in only if the battery is ON. is it safe to try this?

additional.scatch that it only ran for 10mins and batt still 58v.attaching batt to bike.display says 58.4v.which is what its always been. now im confused again, if its not out of balance,why the LVC change. Although my 2 multimeters may be a half volt low inaccurate they still show the charger output .6v higher than the batterys final charge,after hrs an hrs of balance charging.

 

[minexplorer]

If using cheap dvm's then they are uncalibrated, i.e. they haven't been checked against a known source. So the difference between a measured 41.6v and stated 42v is within an error factor. What I would be looking for is for the charger output and final battery charge voltage to be the same with the same meter. For instance, I have a brand new battery which, according to two dvm's I have, charges to either 41.5 or 41.6 - depending which meter I use. However the charger output measures the same. So I have to assume that the battery is charging fully and meter error is an issue.
All that said is does sound like you have sag issues.

yeah looks like my 2 dvm's are reading a .5 volt low. the two 36v batts and chargers match. the 52v batt however is .6v lower than its charger output after long balancing charge. the bike display says half volt higher 58.4v which it pretty much what it showed when battery was new.

 

[Nealh]

All the ones I have with a switch is for a bms switch and are wired so, needs to be on for charging. If the bms isn't on then charging/balancing doesn't occur correctly, it by passes the balancing affect.
Likely battery is well balanced ( individual cell string voltages will tell you that). If they are good, /read well (voltage wise) no reason to suspect otherwise then dvm's must be out.

Somehow you need to calibrate your dvm's against a known correct source, a new battery cell fully charged should show how far they are out or compare to a friends dvm known to be quite accurate.
There should be a voltage pot/adjuster inside so you can trim dvm voltage to be more accurate if it is out.

The bms balances small discrepancies 0.3 > is quite a diiference voltage wise and bms may over time sort the issue out, generally bms balancing takes ages as the balance load is tiny 10 - 100 ma max (typically 30-50 ma).

 

[minexplorer]

All the ones I have with a switch is for a bms switch and are wired so, needs to be on for charging. If the bms isn't on then charging/balancing doesn't occur correctly, it by passes the balancing affect.

The bms balances small discrepancies 0.3 > is quite a diiference voltage wise and bms may over time sort the issue out, generally bms balancing takes ages as the balance load is tiny 10 - 100 ma max (typically 30-50 ma).

So its not a simple battery on off switch then? needs to be on when charging in the future or its not balancing correctly. if the display is the accurate voltage and the dvm is out thats good ,but the dvm at least shows the batts full charge is lower than the charger output by .6v. maybe future long charges with the battery ON will bring it up ? i will have to see. and see if the bike runs til the new lvc of 43v ,rather than cutting out at 45-46v .thanks neal