Parasitic battery drain from ZEVA BMS

Sergio

It depends on the specific application.

A series cart will only go over voltage during charge, but a Sepex can also go during Regen brake.

If using a Sepex cart you need to allow for the Max cell voltage to be higher than the average for Full charge so there is head room if the Regen brake is used hard immediately following a full charge.

The folks that have the Zeva can tell you how long the monitor shows the balancing cycle after the charge, some earlier Zeva datasheets specified up to 1 hour balancing sessions.

The diagram in this post uses 2 additional relays, 1 to detect the charger is plugged to AC and one to place the Zeva in sleep mode.

The LV and HV relays are also wired so either condition can trigger a safety shutdown regardless if it happens during motoring, Regen braking or charging.

Lithium Battery Conversion - LV & HV control relay wiring

BGW

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NCPW

After charging today and giving a 2 hour buffer after the charge, I activated the sleep function. I was at 58.1v, so we'll see where the voltage is in a few days.

DaveTM

I've read...and re-read the documentation.....and I can't see an explanation of how the system "wakes up."

I assume when I turn on the key on?

Sergio

The Zeva remains is sleep mode as long as the "sleep" pin is connected to negative, once you open the switch and remove the negative the system wakes up.

DaveTM

Ahhh.....the reverse of my thinking.

I'm ordering a switch.

DaveTM

I got the "Special 70Old's Racer" switch and installed it this am. You know.......put one wire in the Sleep connector on the ZEVA.....sip some coffee.....connect the other wire to a round bolt connector and crimp it.....that's a two or three coffee sip........Think of where I need to place the switch with it's contact paper back.......another sip........attach the switch.......sip more coffee.....about to connect the negative end........bathroom break from to much coffee.........connect the negative end.

Click the switch and it works like a charm!!!

BTW.....I didn't give this much thought, but with the ZEVA in sleep mode, the cart is still able to drive. Well, I didn't drive it but I turned on the key switch and got a power reading on my separate digital voltmeter. With the F\R contact switch in "N" I hit the go peddle and got the 3 (or maybe 4?) Alltrax controller "good to go" blinks.

After thinking about this, the ZEVA monitors the pack and would shut down the "juice" if a LV was detected......but only if the ZEVA were active. My controller is set (as a backup) for a LV cutoff as well.....but that's just the total pack voltage....not an individual cell voltage.

Anyway.......just thinking out loud.

yurtle

My 11/11/11 (2011) pack still works pretty dammm (ha, enough Ms fools the auto-censor) good, so I'm kinda trying to learn for the day...

Since we have series carts - no regen - seems like a relay or two could automate this. Monitor charger and key switch. I think it may have been posted, but I'm just filing it away for now.

NCPW

So, I'm not too pleased with the sleep function. I still have a good parasitic draw on my pack and the only thing it could be coming from is the BMS or the key switch controlled voltage reducer.

Sunday my pack was 58.1v
Monday it was 57.4v
Tonight it was 56.1v

Sergio

Have You looked for other sources of power drain?

Zeva claims the BMS will draw 8mA while in sleep mode, that is the equivalent of 1Ah after 5 days and it could not possibly have that voltage drop impact.

There is not a standard wiring diagram for these setups so it is hard to troubleshoot unless you have something you can post.

The voltage converter should be suspect as well since it is directly connected to the pack at all times and always drawing some current even if the trigger is OFF.

Is the charger directly wired to the pack or isolated through a relay?

NCPW

Now that I'm thinking about it, I have my charger connected through a HV relay. I disconnect my charger via a Anderson SB50 connector when not in use, but now I'm wondering if the relay along with the reducer is the culprit?