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Unread 07-05-2019, 04:38 PM   #1
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Default Bms stopped

Twice i noticed that the bms display is showing 58.2 volts at the end of charge cycle. The last time the bms stopped and shut everything off, charge was at 58.3v. Never got that high before, and i have left it plugged in over night and bms (usually stopps at 57.9v 58v) and never stopped before. Max charge is set at 4.17v. Cary never gets below 53v. I use a zeva bms. Is that normal. I have a 7 leaf pack

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Unread 07-05-2019, 10:02 PM   #2
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Default Re: Bms stopped

This is what i get. Usually i can leave cart plugged in all night and no issues, she just balances.

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Unread 07-06-2019, 10:59 AM   #3
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Default Re: Bms stopped

I don't have my Zeva manual with me but I'm pretty sure the Max Charge only comes into play when you're using a CAN Bus controlled charger such as the Elcon TC otherwise it has no impact on voltage.

I have had the same issue a few times on both of my carts and plan to address it when I get back to Florida in October. It looks like we've both got simular setups and chargers.

I'm pretty sure that the issue is that just we're charging too close to our Max V setting. I have watched as one or two cells will be just a hair higher than the rest at the very end of the charge cycle, during balancing, when it triggers the cell over voltage protection.

Your charger is probably actually charging to the high side of 58.4 and one of the cells is getting high enough to trigger an Over-voltage event. Once the BMS has finished balancing it has bleed off enough voltage to read 58.2v...

I was talking with Gary about our chargers a couple of months ago and he was telling me that there's three potentiometers inside and one controls the output voltage. Simply put your multi-meter on the output and tweak ccw on the pot until the desired output voltage is reached. I am planning to adjust my charger down a hair to around 58v / 4.14. If you look at the discharge chart your not loosing any significant capacity at that voltage, your stressing the cells less and significantly reducing the chances of overcharging.

With my charger set for 58/4.14v I'll probably have my Zeva settings around:
Max V: 4.17
Bal V: 4.12
Charge V: not applicable for our chargers.

We'll see what I end up with when I get back. Good luckLEAF DISCHARGE GRAPH.pdf

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Unread 07-06-2019, 11:14 AM   #4
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Default Re: Bms stopped

Quote:
Originally Posted by MCJEFE View Post
I don't have my Zeva manual with me but I'm pretty sure the Max Charge only comes into play when you're using a CAN Bus controlled charger such as the Elcon TC otherwise it has no impact on voltage.

I have had the same issue a few times on both of my carts and plan to address it when I get back to Florida in October. It looks like we've both got simular setups and chargers.

I'm pretty sure that the issue is that just we're charging too close to our Max V setting. I have watched as one or two cells will be just a hair higher than the rest at the very end of the charge cycle, during balancing, when it triggers the cell over voltage protection.

I was talking with Gary about our chargers a couple of months ago and he was telling me that there's three potentiometers inside and one controls the output voltage. Simply put your multi-meter on the output and tweak ccw on the pot until the desired output voltage is reached. I am planning to adjust my charger down a hair to around 58v / 4.14. If you look at the discharge chart your not loosing any significant capacity at that voltage, your stressing the cells less and significantly reducing the chances of overcharging.

With my charger set for 58/4.14v I'll probably have my Zeva settings around:
Max V: 4.17
Bal V: 4.12
Charge V: not applicable for our chargers.

We'll see what I end up with when I get back. Good luckAttachment 189088

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Thats were i am. I dont have a canbus charger. I do notice some cells are a tad higher. I set my pot at 58.3v i believe. I am away at seasonal and it wont be checked till oct as well. Just annoying

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Unread 07-08-2019, 09:58 AM   #5
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Default Re: Bms stopped

Stopped charger shows 58.3 when i reboot charge status shows 57.5. Does the bms balance when not plugged in to charge?

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Unread 07-08-2019, 10:12 AM   #6
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Default Re: Bms stopped

The Zeva has a maximum time the balancing shunt is active once the cell is over the set value.

You should not set the "Balancing Voltage" lower than the "Charge Voltage" as it causes many shunts to be active at the same time, produces heat and has not practical benefit.

Whatever the "Charge Voltage" is, divide it by the number of cells and round it up to come up with the proper 'Balance Voltage".

If Your charger is set for 53.8v, the balance should be 53.8v/14 cells= 4.15v

That is pretty high and it may not allow enough "headroom" between that value and 'Max Cell' voltage for the BMS to properly balance the pack.

If You keep hitting a "High Cell" condition during the charge, the best way to handle it is to lower both the "Charging Voltage" and the "Balancing Voltage" until the cells get balanced.

If You lower the charger voltage to 57v and the "Balancing Voltage" to 4.08v, that will allow more room for highs cell to balance while the lower cells are not up to the "average" charging voltage yet.

That is also the preferred setting if You are using Regen brake as it allows the pack to go above the "Charging Voltage" without triggering a high cell event in case you use the Regen brake on a fully charged pack.
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Unread 07-08-2019, 10:34 AM   #7
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Default Re: Bms stopped

When charging your pack the BMS will begin balancing your cells once the Balance Voltage threshold that you set has been exceeded. Your charger will continue to charge completely independent of the cell balancing until it reaches the full voltage level and then shuts off. The Zeva BMS will also continue to Balance the cells by bleeding off voltage from the highest cells until they are all down to the level of the lowest cell or the Balance Voltage threshold you set which lowers your total pack voltage. If you feel the BMS case while its balancing you will actually feel the heat being generated from the individual cells that are being shunt balanced.

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Unread 07-09-2019, 04:17 PM   #8
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Default Re: Bms stopped

Thank you everyone. I will adjust the pot on the charger to 57v and change the bms accordingly. I dont think my cart regens when breaking. When i go down hill the cart doesnt slow itself down, i have to apply the brake.

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