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Tesla full charge balancing issue?..


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My tesla sometimes wont charge fully or close to it based on the wheelog and gotway app. The normal full charge rate would get up to 95%~98%(by wheelog) only when I have used the battery lower than 70%(approx). If I have not used the battery below 70%, the charger goes green and stops charging around 88%~90% which is almost 10% loss..

So when I manage to fully charge my wheel and go out for a very short ride in town, using around 5~10% which leaves it 88~90% and then try to charge the battery to keep it full again, charger still shows green light when it should be showing red to compensate the loss to fully charge the battery. This annoys me since none of the battery cells are dead and both the battery and charger showed fine performance on a recent test from a professional. And it does fully charge(95~98%) only when I ride it below 70%.. I only want to keep my battery full even when I have not used the battery below 70%, since that 10% does make a bit of change in range when I have to go out for a long run.. Anyone has similar symptoms? and anyone professional has an advice? If the cells and charger is fine as the mechanic says, I believe the final cell balancing might have a bit of issue or something.. is this something that can be fixed or just gotta use it this way?

Most importantly none of this happened when I first got the Tesla.. it started happening recently and Ive only used this thing for 2month! And there was no issue with the battery and charger after the test..

Edited by DannyK
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4 minutes ago, Chriull said:

@DannyKpresumably your charger got misadjusted. To "proove" this you maybe could measure the charger output voltage or otherwise just get in contact with your reseller.

yep done that.. sent it to the seller who is a repairer as well and ran all the tests and showed me the results.. both the charger and the battery test showed normal. Thats what drive me nuts.. charging only upto 88~90% when not used below 70% just cant be normal..

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1 hour ago, Chriull said:

@DannyKpresumably your charger got misadjusted. To "proove" this you maybe could measure the charger output voltage or otherwise just get in contact with your reseller.

Already sent it to the seller, he ran the tests both on battery and charger, they were good.. he showed me the test results as well.. Unless hes just trying to make it look like its okay(highly unlikely, he is a trusted professional among our EUC community) I dunno what cud be the problem here.. I dont have much knowledge on these areas, but presumably final cell ballancing might have been twisted?.. depending on useage?

Edited by DannyK
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On 7/22/2018 at 3:38 PM, DannyK said:

Already sent it to the seller, he ran the tests both on battery and charger, they were good.. he showed me the test results as well.. Unless hes just trying to make it look like its okay(highly unlikely, he is a trusted professional among our EUC community) I dunno what cud be the problem here.. I dont have much knowledge on these areas, but presumably final cell ballancing might have been twisted?.. depending on useage?

I'm pretty sure that you could remove the control board from the Tesla without having any impacts to charging it. I.e., with Gotway wheels, the control board is not involved in the charging process.

So the problem is either with the charger or battery(s). This is where it's convenient to have multiple chargers available to you. Then you can easily eliminate the charger as the possible failed component.

I would use a process of elimination to narrow the cause. Disconnect one of the batteries and use the wheel and then see if the charging behavior is normal. Repeat with the other battery. I would guess that only one of the batteries will show the problem.

Edited by Marty Backe
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On 7/22/2018 at 8:01 PM, DannyK said:

charge the battery to keep it full again, charger still shows green light when it should be showing red to compensate the loss to fully charge the battery. 

Keeping your battery fully topped up all of the time, especially if it is very hot where you are is not good for the batteries health and some cells may well start to degrade if only by a small amount in just a couple of months of use. Turning the charger off when it goes green will further emphasise any imbalance by not giving the lower cells time to come up to full charge - it ideally needs to be left a couple more hours.

The charger light goes green, not as a statement that the battery is fully charged but as a result of the charge current dropping below some figure, typically around 200mA, if a significant number of cells have reached 4.2 V at that point but some have not then that is when you will see less than 100% charge. If the Tesla has a balancer that functions during charge and not only at 4.2V (I do not know?) then the cells may have more time to balance if discharged further? 

However this still suggests that there is something a bit screwed with the voltage sensing on your wheel fully charged is 4.2V/cell (times the number of cells) but this drops rapidly under use and under load (below shown for  quite low load at different temperatures but the higher load graph will look the same as the lower temperature one.)

image.jpeg.89954797849cfcfee9020f2ef34c2f58.jpeg

i would, therefore expect the wheel to report around 4.0-4.1V as fully charged so that the rest of the discharge reporting is using the more linear part of the curve, otherwise it would worryingly report a sudden drop to around 80% as soon as you started moving.

Really anything is a guess without some actual numbers like the off load voltage of the charger and the immediate end of charge and after sitting for an hour or two voltage of the battery.

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