Leaf Amp Hours and total pack voltage questions

[somfas]

Hey all, I finally finished my Nissan Leaf conversion..... thank you to all that helped, all the advice, and to Pingeye for really going overboard trying to help. I had considered writing up my conversion as kind of like one of those "....... for dummies" books. But I really struggled with this one and not sure my confusion would help anyone.

I have 10 modules. I have my BMS set to 82v max charge and alt charge. I have Min set to 3.1 and Maz set to 4.1. I have Balance threshold set to 4.1

I am only getting 80.6v total charge. How can I get that up to 82v?

I have Pack Capacity set to 55ah (as a guess), would that affect it? Should I change that or is there a way to test it?

As an aside, just a basic stupid question, when I am driving it, volts will drop down quite a bit from 80v down to 72v-75v and then quickly go back up when I let up off the pedal. I think if I had the cart loaded, uphill, it would probably drop a lot more if I really hammered it. Thats all normal right? And not bad for the batteries to get below 70v?

Thanks all!

[somfas]

Forgot to mention, ZEVA BMS

[DaveTM]

What charger do you have? (I did not look at your build thread)

Does your charger communicate (CanBus) with the ZEVA?

BTW.....congrats on your build!! You will absolutely love Lithium!!

[somfas]

Thanks! I have the TC Charger that is connected to the Zeva with CanBus. Charges at around 10amps. Seems fine except for stopping at 80.6.

[somfas]

The build took so long, I may have messed up the batteries. They held their charge for a long time. However, once I connected them all to the BMS, they drained down quite a bit. It took me months to finish after hooking up the BMS and it was down to 60v total for 10 modules. Maybe that has something to do with it. Although, I would have thought it would still charge to 82v if thats what it was told to do. But the charger stops at 80.6v.

I'm afraid new modules are in my near future, but I at least want to get some miles out of these before doing so. I've taken a few easy short trips so far and they seem ok.

[Volt_Ampere]

What are your individual cell voltages? You may have an imbalance if the pack sat for a long time with the BMS hooked up. You need to determine why the charge is being terminated early. It will terminate if any cell reached the max voltage you set.
As far as pack sag goes, that is not normal if you are not pulling excessive current from the pack. It sounds like your pack's internal resistance may be on the high side.

[somfas]

I just took the cart for a 3 mile run on paved roads with small hills. Here are some numbers from that trip.

Start - 80.6V. Min cell reported as 4.03v and Max at 4.05, with average of 4.03. Looking at each cell, actual numbers ranged from 4.028 to 4.045 with only 2 cells being over 4.036.

During the ride, just easy cruising at the start, 76.2V 78.8A current 5.7k power
Halfway through, 90% throttle on flat 74.3V 87.7A current 6.5k power
End of ride, WOT up steep hill 71.3V 139A current 9.8k power

Ending total pack voltage was 79.5V after sitting for 20 minutes, Had a drop of 1V for 3 miles of medium to hard cruising.

[DaveTM]

I believe that when my cells get what I consider, to wide of a balance range....I set the ZEVA to do a charge on "Dynamic Balancing". One charge using this setting brought back the cells to what I considered a good balancing.

To me, a "well balanced pack" is .002 volt difference from the lowest pack to the highest pack.

Now, a 1V drop in the packs charge after a "hard" 3 mile ride doesn't appear to be bad. That appears to be normal. I know my pack's voltage "range" is from 57.3 full charge, to 50.0 volts. Once I hit 50.0 pack volts I know I have very little time before the LV relay will kick off.

So...using your example...my voltage "range" is 7.3V. (57.3-50.0) A one volt discharge for 3 miles would give me a 21+ mile ride. Not to shabby if I'm "cowboying" it the entire time.

[somfas]

Thanks for that feedback DaveTM. I will try that. And also good to know about the voltage drop

Also, what is the significance of the Pack Capacity? whether I put in 55ah vs 66ah?

[DaveTM]

Originally Posted by somfas

Thanks for that feedback DaveTM. I will try that. And also good to know about the voltage drop

Also, what is the significance of the Pack Capacity? whether I put in 55ah vs 66ah?

Frankly, I've never understood the AH capacity "thing." I've always looked at my volt meter to determine how much "juice" I have left.

I know that the more batteries, or the more modules the cart has means I've got more runtime. And that bigger packs = more AH.....but I still look at the volt meter to determine where my pack is at during any outing.