I didn't have it switched on, but then that wouldn't make any difference would it as I measured it at the battery?

I'm out at the moment, so can't check. But if everything is all OK cells wise, why would it not take a charge and it is still outputting 30 something volts at the battery connection (ie, where you plug it into the motor)

You can measure something like 18v to 30v leakage charge on the output when it's switched off. That's how you know when your BMS is switched off. The only question is why the BMS is switched off. It could be because you didn't switch it on, or it went to sleep.

Just got in from work so not seen the updates until now, as I said earlier and as D8ve has also reiterated the cell pack appears fine. We need to see the actual 14 voltage readings in writing.

56.6v / 14 = 4.04v each which is pretty good, with 56.6v if a cell group was 0 then the others would read 4.35v which is bad. One suspects one didn't probe correctly for a good contact.

If the BMS has gone to sleep remove the thin sense wire multi connector then refit it to see it the BMS wakes up.

 

The pack is to good to bin , it simply may need new BMS if all the cell groups read ok and the BMS cant be woken up.

 

As mentioned the 30v reading is because the BMS has shut down.

Whether a battery can be charged via the discharge wiring depends on the mosfet type used. P types aren't for reverse charging whilst N type are.

One can apply a 10/15 sec reverse charge to try and wake up a BMS or disconnect & re connect the multi wire jst connection .

 

A few reasons not reverse charge as a matter of course if a seperate port BMS is used.

 

• Applying to much current.
  
• Connecting polarity incorrectly.
  
• Damaging a good BMS.
  
• Not knowing mosfet type used.
  

I have never taken much notice of the mosfet designation but should do.

For sure a same port BMS must be a N type and it may be that some separate port BMS may be N type but unless one is sure then mosfet damage may likely occur.

Just got in from work so not seen the updates until now, as I said earlier and as D8ve has also reiterated the cell pack appears fine. We need to see the actual 14 voltage readings in writing.

56.6v / 14 = 4.04v each which is pretty good, with 56.6v if a cell group was 0 then the others would read 4.35v which is bad. One suspects one didn't probe correctly for a good contact.

If the BMS has gone to sleep remove the thin sense wire multi connector then refit it to see it the BMS wakes up.

 

The pack is to good to bin , it simply may need new BMS if all the cell groups read ok and the BMS cant be woken up.

 

As mentioned the 30v reading is because the BMS has shut down.

Thank you for the comprehensive reply, especially straight after work, much appreciated.

I will take a look again today and write down the actual voltages and take it from there. Good to know that all may not be lost.

I did unplug the BMS and plug back in and that has not made any difference though, so doesn't look like that will work to bring the BMS back to life. If the last resort is a reverse charge, how would I do that? A direct connection to the charger with the battery output connections?

Yes direct charging via the discharge connection but only for 10/15 secs to shock the system , of course polarity has to be correct and an adapter from charger to battery made up.

Just got in from work so not seen the updates until now, as I said earlier and as D8ve has also reiterated the cell pack appears fine. We need to see the actual 14 voltage readings in writing.

56.6v / 14 = 4.04v each which is pretty good, with 56.6v if a cell group was 0 then the others would read 4.35v which is bad. One suspects one didn't probe correctly for a good contact.

If the BMS has gone to sleep remove the thin sense wire multi connector then refit it to see it the BMS wakes up.

 

The pack is to good to bin , it simply may need new BMS if all the cell groups read ok and the BMS cant be woken up.

 

As mentioned the 30v reading is because the BMS has shut down.

Off topic, forgive me, but is WheezyRider aka D8ve aka vfr400? If so, glad you have returned with your helpful knowledge and experience. Blame Nealh for blowing your cover lol. Anyway a belated welcome back

Off topic, forgive me, but is WheezyRider aka D8ve aka vfr400? If so, glad you have returned with your helpful knowledge and experience. Blame Nealh for blowing your cover lol. Anyway a belated welcome back

 

 

I don't know, tbh I haven't even thought about WR as being D8veh not that it matters.

Some of us though know another alias being used.

Edited November 21, 20223 yr by Nealh

Off topic, forgive me, but is WheezyRider aka D8ve aka vfr400? If so, glad you have returned with your helpful knowledge and experience. Blame Nealh for blowing your cover lol. Anyway a belated welcome back

 

No, I'm certainly not D8ve or vfr400. If you look back in the history you will see we have had our fair share of - "discussions". Sorry to disappoint

No, I'm certainly not D8ve or vfr400. If you look back in the history you will see we have had our fair share of - "discussions". Sorry to disappoint

Sorry Wheezy, I think I went all Columbo and failed miserably. It was Nealh line earlier in the thread mentioning D8ve that prompted the thought D8ve/VFR400 was back on the forum under a new alias, clearly not the case. As Nealh says, it matters not either way.

I'll get my (Trench) coat

As I metioned d8evh/vfr is on the forum and posts but not as much as previously, the alias used is one that belonged to a late friend of his.

Hi all,

Sorry for the delay, just been out this morning with the multimeter again.

Pack in total (at first and last cell) is showing 56v .

I then measured each point on the plug in point, points 1 to 13 are showing 4.1volts on every point from 1 to 13. Point 14 is still showing 0v.

So 13 x 4.1 = 53.3, so I'm missing some volts somewhere!

I checked all of the wiring from the battery to the plug and all appears good with no obvious breaks or weak spots. However, just putting the meter on just the cells on the last pack also shows zero, although putting it on the last TWO packs then shows 8.3v, so I'm fairly certain that the last pack has power in it but I just cant work out why it is not showing?

I have plugged the BMS sensor plug back in and still no difference, when charger is connected still 'clicking' on and then off constantly.

Is a reverse charge worth a try or does the unplugging/pluging back in of the sensor wires normally wake it?

Thanks again

I'd keep looking for those missing volts first! If you can understand that issue, it may be related.

 

You have 14 cell groups, so 15 places that your meter probes need to go to measure all cell groups. There should be 14 red and one black wires on the balance connector. Those should give access to the points you need to probe.

I'd keep looking for those missing volts first! If you can understand that issue, it may be related.

 

You have 14 cell groups, so 15 places that your meter probes need to go to measure all cell groups. There should be 14 red and one black wires on the balance connector. Those should give access to the points you need to probe.

Yeah, I agreee, it's that B14 point that is the issue, I feel like if I could get a voltage through that point it would solve the issue but I can't work out why the wire/first group of cells isn't showing a charge?

is D8ve aka vfr400?

 

Don't mix up D8ve and D8veh, they are two different people.

 

in This Post D8ve thanks D8veh for his help.

 

Many believe D8veh became vfr400 and then later on, Saneagle.

.

Yeah, I agreee, it's that B14 point that is the issue, I feel like if I could get a voltage through that point it would solve the issue but I can't work out why the wire/first group of cells isn't showing a charge?

My cheap multimeter probes sometimes have to be pushed very firmly to get a good contact.

 

I would start at the cells, and get 14 valid voltages measured directly there, which must be possible because of the overall 56V or so. Then repeat measuring on the balance connector wiring.

 

It should be possible to get the same reading whether you probe directly on the cells or on the wiring. Anywhere it isn't the same, then inspect really closely, or double check meter probe contact quality.

 

I would not do anything else until the voltage measurements at cells and connector are understood and correct. There will be a reason.

I then measured each point on the plug in point, points 1 to 13 are showing 4.1volts on every point from 1 to 13. Point 14 is still showing 0v.

So 13 x 4.1 = 53.3, so I'm missing some volts somewhere!

one possible explanation is the wire from Point14 to the cellpack is broken where it is soldered to the cells.

Yes correct Flecc , I should revert back to saying d8veh instead of plain d8ve.

Likely #14 is low approx. 2.7 - 2.8 volts and the reason why the BMS doesn't switch.

With the other cells at 4.1v it makes sense that #14 is low, one needs to try and get a correct reading for #14.

Can you not probe directly on the cell group ends rather then the wiring ?

 

One can also get a cell reading via the JST connector , place a needle or pin in Red wire #14 position and also one in Red wire #13 position (don't allow pins to touch/short out). Probe both pins with a meter (again don't allow probes to short each other) one should get a correct voltage reading.

 

To get the BMS to work one will have to raise #14 manually to 4.1v or very close , then the BMS will switch on. No use charging to a much lower figure on #14 as the BMS won't balance a huge difference in voltage.

 

The reason the BMS doesn't switch is because it detects a fault , that fault being one cell group is low and below the minimum cell group voltage it expects to see.

Sometimes one can get away with 3v but it is all dependant on how the BMS is programmed.

During the non use period the BMS has bled down #14, most common fault is an open bleed resistor or the battery sw left on .

 

To manually charge one will need an old 5v mobile phone charger, cut the charge connector off and split the two wires. Pair back the wire ends and solder on a arduino board pin to each wire, check polarity and heat shrink a bit of Red and Black to each pin.

Then one can charge the cell group directly or via the JST sensor connector.

If the JST has 14 thin Red wires , simply put the 5v charger Red pin in the very last Red wire position and the 5v charger Black pin in the 13th Red wire position.

Switch the charger on and then carefully monitor that cell group voltage , once the group reads 4.1v or very near try charging as normal.

Edited November 22, 20223 yr by Nealh

Thanks Neal, your explanation certainly makes sense and I will give it a try.

Just need to find an old charger now!

Thanks Neal, your explanation certainly makes sense and I will give it a try.

Just need to find an old charger now!

 

 

I would rather have something specifically for charging single cells. I use the charger module out of Poundland USB packs for reviving cells.

Mocked up a charger and put a charge through the pack, still nothing registering after having the charger on for nearly 2 hours. I would expect to see at least some voltage in the cells after this amount of time surely?

Beginning to think it might be duff cells after all. I charged via the jst pins so my only other option is to put the phone charger directly on the cells to rule out duff connection/wiring but I’m not holding out much hope

Mocked up a charger and put a charge through the pack, still nothing registering after having the charger on for nearly 2 hours. I would expect to see at least some voltage in the cells after this amount of time surely?

Beginning to think it might be duff cells after all. I charged via the jst pins so my only other option is to put the phone charger directly on the cells to rule out duff connection/wiring but I’m not holding out much hope

 

I wouldn't lose heart just yet. Can you show a picture of how you are measuring voltage on the last bank which seems to be showing 0V?

Mocked up a charger and put a charge through the pack

 

Whats a 'Mocked up charger' and how was it connected ?

Whats a 'Mocked up charger' and how was it connected ?

As Neal advised above, 5v phone charger, put through the 14th (positive) and 13th (negative) pins of the jst connector which normally plugs into the BMS

I wouldn't lose heart just yet. Can you show a picture of how you are measuring voltage on the last bank which seems to be showing 0V?

I’ll try and get a pick today of the voltages at the various points