Charger help please!


Rashid510

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Yes it will remain at that voltage since the p-group is no longer connected. This is the case with any Code 36/35 packs. Ultimately your pack will hit the minimum based on that cell that goes bad. Its pretty much a pack swap or module swap if you want to get crafty. Repair is possible. @OneLapper is the closest.
 

snydes

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Will that cell remain at that voltage until the others catch up (down)?

What you are seeing is the voltage of the remaining 5 cells in that parallel group, you can not see the voltage of the disconnected cell because... it's disconnected. That is definitely a wicked imbalance. Not really fully understanding why the SOC is displaying what it is displaying, but like Mark911 stated that's the worst imbalance we've seen so it must be doing something wacky we haven't experienced yet. Checking out one of your last ride logs and looking at some of the voltages might shed some light on things.

All these wirebond code 36 packs will look slightly different based on what SOC that wire broke loose at. When the battery is opened up and that P group is inspected, I'd be curious to know what voltage the disconnected cell is at (that would tell you at what voltage the wire broke). Right now I can't imaging the scenario that would cause the imbalance to look like that. I believe this is what can potentially happen when a wirebond failure is left go and is a accumulative affect of lost capacity in that P group.

Manually balancing that group and attempting to reconnect that cell should make the pack usable again, but it's a risky compromise and based on what I have experienced you will not get rid of the code 36. The 5 cells left in that P group are going to have taken a hit in capacity and likely will never stay in balance with the rest. It should charge and operate normally, just have to continue to see that CEL light glaring in your face (or put a piece of electrical tape over it).
 

bluefxstc

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Could the state of charged be based on the voltage of the lowest cell group, vs columb counting, which in this case is pretty low. Looks like the wire broke when the cell was in the discharged state instead of a charged state as most of the graphs we have seen. I wonder how much change there would be in SOC as the bike was ridden. If it was based on the voltage of the lowest cell group it wouldn't change as the bike was ridden.
 

snydes

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If I'm understanding this correctly, it's saying the pack is at 22%, which just doesn't make sense to me no matter how I try and look at it. A healthy pack with a cell voltage of 3.5v should come in at around 45ish percent.

When a wirebond breaks at a lower pack SOC, you will see that P group sticking way up high when the rest of the pack is charged because of that group now takes much less to get back up the the max voltage. From what I've seen the best place (if you can call it that) for one to break is about 3.8v. That seems to give the best compromise on the low and high end of the overall pack SOC.

The pack shown below is an example of a wirebond failure that happened at around 3.5v (cell voltage).

ABAB190B-3416-4782-9C36-639DA8CA646F.jpeg
 

snydes

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This one broke at a slightly higher voltage (mod 3 P1). If memory serves it was roughly 3.65v.

E8E71039-2BA9-4A66-A2D4-F3EA6A15C615.jpeg


This one broke when the pack was fully charged. It looked dead perfect at 100% but as soon as the pack started discharging module 3 P group 9 would drop like a stone.

AC1CD547-FCFB-4D88-853E-F3969975DB03.jpeg
7A9BC176-A231-4584-9CF2-657A8245A62B.jpeg
 

bluefxstc

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I was under the impression, possibly/probably wrong, that battery was made up of series and parallel strings of cells. If a lead in a series string broke that string wouldn't charge leaving it permanently low (see pic in post 12). If the pack used voltage, instead of columb counting, to determine SOC then a permanently low string would leave the SOC low.
 

snydes

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I'm probably not understanding you quite right, I honestly haven't a clue what columb counting is. By design when a fuse wire pops/breaks, it only affects the single cell it was associated with. The BCU can no longer see the voltage of this cell, only the voltage of the remaining cells of that parallel group. You could only loose the entire P group if every fuse on every cell popped in that group. Hopefully that makes better sense.
 

Mark911

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The BMS monitors the voltage of each P-group (21 per module, 84 total). Each P-group has 6 18650 cells. However, the system looks at each p-group as being ONE unique cell, not 6. If during discharge ANY p-group reaches the minimum voltage (the ave voltage of the 6 18650 cells wired in parallel, or the 5 or 4 or . . . depending on wirebond or other issues) as set by the firmware the BMS will shut down the pack (open the contactors) to protect that particular P-group from becoming over discharged. Li-Ion cells can be permanently damaged when over charged or discharged, that's why there's parameters for both.
In this case it looks like the bad P-group simply lost voltage faster and/or charged slower than the others and over successive ride/charge cycles is now at an open voltage much lower than the rest. Since it's an issue that will trigger a low voltage cut-off the effective capacity of the pack will be severely reduced as there's no way the passive balancing system can (or want to) dump that much energy from the good cells. Even with an active system I doubt the system could keep the bad P-group "pumped up" enough to not affect the effective capacity via low voltage cut-off.
The system also keeps track of all the energy going into (charging) and out of (discharging) the system, ie coulomb counting. By using this data and applying various algorithms the BMS can actually predict how much range (effective capacity, not necessary capacity as indicated by each cell) is available at any time. This helps the rider gauge his/her decisions on the trail/track and from a long term standpoint can assess the overall health of the pack. For example, as the pack ages it loses capacity. End of life is typically 80% (20% loss) of capacity. Without long-term re-calibrations you'd be running out of charge and the display would still say you have 20% pack remaining. You wouldn't want that. By the same token if the system senses a low P-group voltage it can use it along with all the other data collected to calculate about how much effective capacity you can expect and it'll report that via the display. That's what you want as it wont leave you stranded out in the middle of nowhere with a dead bike and a display showing 80% pack remaining!
Having said this it would have to have been an issue that's been getting progressively worse over time. It's possible Alta revised some of the algorithms to better indicate effective range via the display and you might see a sudden shift upon the firmware update if your bike had some p-group issues, I'm not that familiar with the software end of things.
 

Edabdo

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The BMS monitors the voltage of each P-group (21 per module, 84 total). Each P-group has 6 18650 cells. However, the system looks at each p-group as being ONE unique cell, not 6. If during discharge ANY p-group reaches the minimum voltage (the ave voltage of the 6 18650 cells wired in parallel, or the 5 or 4 or . . . depending on wirebond or other issues) as set by the firmware the BMS will shut down the pack (open the contactors) to protect that particular P-group from becoming over discharged. Li-Ion cells can be permanently damaged when over charged or discharged, that's why there's parameters for both.
In this case it looks like the bad P-group simply lost voltage faster and/or charged slower than the others and over successive ride/charge cycles is now at an open voltage much lower than the rest. Since it's an issue that will trigger a low voltage cut-off the effective capacity of the pack will be severely reduced as there's no way the passive balancing system can (or want to) dump that much energy from the good cells. Even with an active system I doubt the system could keep the bad P-group "pumped up" enough to not affect the effective capacity via low voltage cut-off.
The system also keeps track of all the energy going into (charging) and out of (discharging) the system, ie coulomb counting. By using this data and applying various algorithms the BMS can actually predict how much range (effective capacity, not necessary capacity as indicated by each cell) is available at any time. This helps the rider gauge his/her decisions on the trail/track and from a long term standpoint can assess the overall health of the pack. For example, as the pack ages it loses capacity. End of life is typically 80% (20% loss) of capacity. Without long-term re-calibrations you'd be running out of charge and the display would still say you have 20% pack remaining. You wouldn't want that. By the same token if the system senses a low P-group voltage it can use it along with all the other data collected to calculate about how much effective capacity you can expect and it'll report that via the display. That's what you want as it wont leave you stranded out in the middle of nowhere with a dead bike and a display showing 80% pack remaining!
Having said this it would have to have been an issue that's been getting progressively worse over time. It's possible Alta revised some of the algorithms to better indicate effective range via the display and you might see a sudden shift upon the firmware update if your bike had some p-group issues, I'm not that familiar with the software end of things.
Well, I wont be riding this until I get it repaired. Time to remove a battery pack!
 

Edabdo

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What you are seeing is the voltage of the remaining 5 cells in that parallel group, you can not see the voltage of the disconnected cell because... it's disconnected. That is definitely a wicked imbalance. Not really fully understanding why the SOC is displaying what it is displaying, but like Mark911 stated that's the worst imbalance we've seen so it must be doing something wacky we haven't experienced yet. Checking out one of your last ride logs and looking at some of the voltages might shed some light on things.

All these wirebond code 36 packs will look slightly different based on what SOC that wire broke loose at. When the battery is opened up and that P group is inspected, I'd be curious to know what voltage the disconnected cell is at (that would tell you at what voltage the wire broke). Right now I can't imaging the scenario that would cause the imbalance to look like that. I believe this is what can potentially happen when a wirebond failure is left go and is a accumulative affect of lost capacity in that P group.

Manually balancing that group and attempting to reconnect that cell should make the pack usable again, but it's a risky compromise and based on what I have experienced you will not get rid of the code 36. The 5 cells left in that P group are going to have taken a hit in capacity and likely will never stay in balance with the rest. It should charge and operate normally, just have to continue to see that CEL light glaring in your face (or put a piece of electrical tape over it).
Yeah... I've done the tape thing already! Lol!
 

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