Lithium pack with electric parking break

[TheCartBoy]

Oh, that's annoying. You would have to change the nominal voltage to 58v then to get 80% setting to be 46.4v. but what's the limits on the overv setting?

[InVision]

Well ....

Full volts per cell is 3.40 x 16 cells. Empty Volts per cell is 2.50v x 16.

Should those be changed? I will check the range on OVERV tomorrow when I get back.

Thank You

[TheCartBoy]

Naw those are just for the SOC algorithm that's only for lead acid

[InVision]

The setting are:

Overvoltage: 115-200%
Undervoltage: 50-80%

M

PS - Would entering the actual Volts per cell help with the cart's built in meter to approximate the SOC of the Lith Pack?

[TheCartBoy]

That's unfortunate, the parameters limits are too restricted to setup both overv and underv, you will need to pick only one...

The volts per cell won't be the value you think it is, because the controller doesn't let you enter the number of cells directly. It assumes # cells is the nominal voltage ÷ 2. So you might be able to improve the controller SOC, but will need to do some math to figure out the values. Do you have the BMS SOC visible somewhere? I vaguely remember you saying it was under the seat hidden.

[InVision]

Darn...

I think the undervoltage is most important because of the electric brake? If so I should just max out to 80%? I set the over voltage to 122%

I moved the display to the lower dash, but I still have to push button when I want to know info. It does shut off automatically.

The cart has a nice info display on steering wheel with an indicator. *see photo

I have found a meter that works well with lith battery, but I have to find a relay to turn on/off automatically. Working on that.

So I have complicated the issue by putting in a custom programmed controller that gave me good torque and speed years ago. There were no lith batteries back then. Someone else programmed and I can't change some things and others as you noted are limited to low level programming that I cannot access. Also I have a limit of 7000 rpms that I wish I could change to 8000 rpms.

The cart runs great, but the display meter is a hassle and when the electric brake locked up when I was going fast was scary.

So the work arounds are push button when I start to use cart and charge when the battery 40-50-% which is about 40 miles. The display has a trip set that I zero when battery is fully charged.

Thank you. You are very helpful, a big asset to a great forum !!

M

[TheCartBoy]

I agree with you, I think it's better to have the cart slow down/ limp when the battery gets low instead of letting the battery completely die. On a full charge, just be mindful not to regen too much, easy enough when you live in a flat area.

Upload the controller CPF file here, might need to .zip it first. I'm curious why you are 7k limited.

I see it would be ideal to get that original display working. Let me do some math for what SOC tuning values to try.

[TheCartBoy]

The forum is shrinking down the picture, but it seems readable. The screenshots are from the curtis manual, I linked it below - you can see the undervoltage limits are supposed to be more open than yours.

1. Set nominal voltage to 58v and undervoltage to 80% to get 46.4v. You'll need to drive around at very low voltage to confirm this is an effective setting.

2. Assuming we don't have to change the nominal voltage again to make the undervoltage protection work, use these rescaled per cell voltages for the SOC algorithm. The controller doesn't let you enter the number of cells, so that's why we have to rescale the cell voltages, I left my spreadsheet on there you can get an idea. Its (58.4v / 29) for full + reset cell. Its (46.4v / 29) for the empty cell. Set the reset percent to 100% to that feature doesn't interfere, and the default value for discharge time is probably fine, that's a fine tuning element.

https://www.noco-evco.com/product/cu...4E_36E_38E.pdf

[TheCartBoy]

Since we are changing the nominal voltage, we have to change the pull-in and holding % for the main contactor and EM brake. I'll need to know your current settings for those.

[EcoChandler]

@jasonojordan (forgot to quote your thread)

The BMS has a ton to do with it. The BMS is what tells the battery to shut down a lot of the times. That's why buying a quality battery with a quality BMS and cells is even more essential when installing into a cart with an EMB and zero CAN comms between that battery and the controller.