06-02-2021, 05:49 AM | #1 |
Gone Wild
Join Date: Feb 2015
Location: Myrtle Beach, S.C.
Posts: 226
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Lithium setup discharging
Have a 14 cell nissan leaf setup in my precedent with the Chargery BMS. I have noticed that the cart is losing .3-.4 volts every day. BMS shows storage and no current which means it isnt reading this discharge
any thoughts? My charger LED does stay on all the time but cant imagine that is drawing this much power? even with the cart turned to storage and tow switch on, the pack is still losing voltage. |
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06-02-2021, 06:29 AM | #2 |
Nincompoop village idiot
Join Date: Apr 2018
Location: Michigan
Posts: 9,625
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Re: Lithium setup disharging
I’d start by doing a parasitic draw test and see what kind of idle current you’ve got pulling from the controller, radio, voltage reducer, or any other add ons.
It would also be helpful to know what is installed in your cart. And when this occurs. Off a fresh charge it’s normal for it to drop voltage relatively quickly for a bit until the batteries settle down to their true voltage. |
06-02-2021, 08:29 AM | #3 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,125
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Re: Lithium setup disharging
Something is draining your battery pretty significantly if you are losing that much voltage per day. You need to determine where the load is coming from. I use a clamp on DC ammeter for diagnosing that kind of stuff but you can use a regular DVM in amps mode if you disconnect things and put it in series.
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06-02-2021, 09:15 AM | #4 | |
Gone Wild
Join Date: Feb 2015
Location: Myrtle Beach, S.C.
Posts: 226
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Re: Lithium setup disharging
Quote:
I will look at my wiring again. Its strange thought because with my pack "disconnected" at the HV?LV disconnect the pack will still lose voltage. So at that point i believe the only thing connected to the pack would be the BMS leads and the charger but the pack will continuously keep draining so if i leave it unmonitored for a month i would have a ruined pack I don't think it did this when I first installed the pack. |
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06-02-2021, 09:41 AM | #5 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,125
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Re: Lithium setup disharging
Sounds like either the BMS or charger is pulling some current. Try disconnecting them and leaving it for a day or two and then check the voltage. I left my Leaf pack for 5 months with everything disconnected and it was within 100mV of the same voltage when I returned. I do not have an onboard charger - don't like them. My home designed BMS draws no current when the cart is off - but I disconnected all of the sense leads when I left the pack anyway.
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06-08-2021, 06:46 AM | #6 |
Gone Wild
Join Date: Feb 2015
Location: Myrtle Beach, S.C.
Posts: 226
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Re: Lithium setup disharging
haven't been able to figure it out yet, but it appears to be draining faster with the BMS on.
If I use the sleep mode which activates the disconnect I am only losing .1-.2 V per day. IF i leave BMS on I am closer to .4v I will probably disconnect the bms for a few days and get a few readings and go from there |
06-08-2021, 10:23 AM | #7 |
Gone Wild
Join Date: Oct 2012
Location: Southwestern Pa.
Posts: 6,204
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Re: Lithium setup disharging
Don't know the Chargery BMS but I will say that on my ZEVA, when I put it in sleep mode, the little green light on the BMS still remains lit.
That's draining some power.....if I were to store over a long time period I'd disconnect the pack. FWIW |
06-08-2021, 02:07 PM | #8 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,125
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Re: Lithium setup disharging
When I left my cart for months, I disconnected everything from the battery cells. It was fine and at same SOC 5 months later.
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06-08-2021, 06:33 PM | #9 |
Gone Wild
Join Date: Apr 2017
Location: SE TN
Posts: 2,218
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Re: Lithium setup disharging
One of the things that causes a BMS to run down in standby is the balancing current. Do you balance your batteries in static or charge mode? And are your battery voltages within 30mv? Just a SWAG
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06-08-2021, 06:48 PM | #10 |
Bonafide Nincompoop
Join Date: Dec 2015
Location: Charlottesburg Va
Posts: 8,987
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Re: Lithium setup disharging
I agree you need to disconnect Everything from the pack including the BMS and monitor voltage over a few days.
I would have to think something in the BMS has failed for it to draw that much current. That's probably about equivalent to a 194 incandescent light bulb being powered by the pack. The LEDs used on most electronics these days draw so little current a pack that size could probably run one for a year or more without draining below threshold. |
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