AOVOPRO M365/ES80 charge/run time too short

[IATSE A1]

I have an AOVOPRO M365/ES80 - Ran really strong and long initially (first month) full charge time was 4-5 hr's.
After being ridden to power shutdown as can happen, the charge time shortened to an hour and then even less (charging - red, charged - green) Finding distance also decreasing proportionately.

I've read extensively to develop an understanding of troubleshooting procedures, it's determining and executing the appropriate repair that's got me stumped.

1st. I've fully charged (green) then extracted the pack and noted voltages by metering through the bms connector and they were:
4.01v, 3.97v, 4.02v, 4.07v, 3.69v, 3.44v, 3.67v, 4.07v, 3.39v, 3.81v

2nd. Then reinstalled the pack and rode hard to power shutdown.

3rd. Immediately extracted the pack and again noted voltages by metering through the bms connector and they were:
3.99v, 3.95v, 4.00v, 4.05v, 3.67v, 3.42v, 3.66v, 4.05v, 3.29v, 3.79v

I find no heating of the battery, charger or connections during or directly after charging and/or riding hard to power shutdown.

I've read many posts to arrive at a solution but don't quite get what to do next.

 

[A-DamW]

That pack looks WAY out of balance to me.

Looks like you have done enough homework to arrive at an answer; balance the pack.
How you want to balance the pack is up to you, if you want a list of all the ways I can think of, let me know, or use you search skills.

Next might be determining the root cause for imbalance.

When a pack is balanced, all of the 10 cell groups voltage arrive at the same time when charging to full and discharging to empty.

When a pack is out of balance, the highest voltage cell group will stop charging, the lowest voltage cell group will stop discharging.

As the voltage difference between cell groups gets larger, the usable battery capacity gets smaller.

 

[amberwolf]

Since the cells are that far out of balance with only a month of use, the best way to fix the problem is to replace the battery with one made from quality well-matched cells that are more than capable of the worst-case power usage you'll put the system thru.


Balance problems like this are caused by cells that are not all equally capable, and do not have equal capacity. That cannot be fixed without replacing all the cells with well-matched cells.

If you don't have experience re-celling a pack, the cheapest and simplest method is replace the entire pack.

Re-celling the pack requires the right tools and skills, which in general are the same as required to build a battery pack from scratch; it's probably more expensive than buying a new one (as long as a new one of the right qualities can be found--if the only ones available for it are made by the same company that made the original, it's probably going to have the same results as this one, if the same process and parts are used).


Rebalancing the existing pack will help it some, but the problem will only grow worse with time, especially under hard usage.

If the pack's BMS has a balancing function (some do, some don't), then leaving it on lhe charger will eventually rebalance it (which doesn't fix it, just makes the cells all the same voltage temporarily). Since the imbalance is fairly large, it may take days on the charger as it cycles thru the stages of balancing to do this.

 

[IATSE A1]

Thank you for the replies.

I would like to rebalance this pack I just don't know the best (smartest) method to get it done.

Input would be greatly appreciated, detailed instruction even more so...

 

[IATSE A1]

I have base knowledge and equipment (meters and such, but no spot welder) to get the job done.

I think the OEM charger is junk (dumb, 2 wire) and BMS, not much better.

I ponder this narrow voltage window between each group, each controlling the other within a volt or so and wonder how they could be made to charge and discharge so precisely together.

 

[amberwolf]

I think the OEM charger is junk (dumb, 2 wire) and BMS, not much better.

While it's certainly possible the charger is junk, 2-wire "dumb" chargers are perfectly fine; it's the most common way of charging--communication between charger and BMS is not required if the BMS is designed correctly.

But the BMS design can vary widely between packs and systems; unfortunately cheap ones with poor design and/or manufacture, and even without any balancing function, are common in cheap packs.

I ponder this narrow voltage window between each group, each controlling the other within a volt or so and wonder how they could be made to charge and discharge so precisely together.

I'm not sure what you mean.

If you mean keeping the cells balanced: the cells, if of good quality, and of sufficient capability to handle the loads placed on them, and well-matched in capability and properties to start with (not just voltage), will stay balanced on their own.

If they do not have those properties, they will not stay balanced, drifting farther apart the higher the loads and the farther they are discharged each time.

In that case, the BMS must have a balancing function built in. There are various threads that discuss how these work, if you are curious, but the most basic type has obvious rows of identical parts on them (one set for each group of cells) that do the balancing. You can see one version of them on the right side of the BMS in the randomly found image below:



If your BMS has a balancer, then leaving it on the charger long enough (would guess days for the imbalance your pack has) will eventually rebalance the fully-charged voltage of the cells.

If your BMS does not have a balancer, you can manually do it either by recharging each low cell to match the highest one with a USB charger (while continuously monitoring voltage so it does not exceed the max allowable cell voltage), or draining each high one to match the lowest one with a low-ohms resistor (or automotive light bulb (or several in parallel).

It will still not fix the problem the cells themselves have of not being of equal capacity, and possibly of being insufficiently capable for the load your system sees--replacing the cells (or the whole battery) would be required to do that.

 

[IATSE A1]

So how would I selectively charge or discharge the target group of cells, thru 2 of the 11 leads used to previously check voltages and 1 group at a time?

 

[IATSE A1]

Again, I would like to rebalance this pack I just don't know what method is appropriate.

 

[amberwolf]

Three different ones have been suggested. You may choose whichever you are comfortable with and have the equipment for. Once you choose one and state / show the equipment you have, we can suggest connection methods and sequence of steps and expected results.

 

[j bjork]

So how would I selectively charge or discharge the target group of cells, thru 2 of the 11 leads used to previously check voltages and 1 group at a time?

Yes, that would work. If you dont have a charger you can always discharge the higher groups down to the lowest groups voltage with a light bulb or a resistor. Be sure to monitor the voltage so you dont go too low.. Or you can use a balance charger for rc lipos. Or as Amberwolf suggest, leave it on the charger if the bms balances.

 

[IATSE A1]

Attached are pic's of the battery, BMS and one of my meters.
I'm sure the BMS is not anything as elaborate as what you have shown and likely not balancing the pac.
I don't know what else you want pic's of?
I have a wide array of bench tools and test equipment, weller soldering station and access to whatever hardware, wire and connectors needed to create jigs, pigtails or whatever to spec.
I can read plans, drawings and follow instructions to the letter.
What's next?

 

[IATSE A1]

I have the OEM charger from the scooter.
I have an entire bin of assorted AC&DC chargers and P/S of varying amprages & voltages.
Additionally I have a Viz WP705 (0-50v / 0-2a) variable bench power supply.

 

[IATSE A1]

I have on hand an array of ceramic resistors and out in the shop 12v off road lights if needed