Problems

[Sailor K]

I built a LIFEPO4 battery. 8 32A cells and a JBD BT BMS. Hooked it up. Got 26V across the battery. Each cell was within .01V+- of 3.24. Charged it up with a LIFEPO4 charger. It appeared to charge correctly--at least the charger did not complain. However, when I put a meter across the positive and C- of the BMS, I get only 3.77V. It won't power a 24V load. JBD blue light was flashing (indicating good BT?) When I tried to connect the BT app, it would not connect to the Blue elephant app (might be user error), did connect to the Overkill Solar and would download and upload parameters to and from the BMS, but would not display voltage on the home page. What is likely problem?
PS: Double checked wiring and it appears correct. All cells are 3.33V right now, measured by meter. Entire battery, measured at the battery terminals is 26.6V

 

[sunshine_eggo]

Stick with the overkill app. The newest version of the elephant app sucks.

What did you do between charge termination and measuring 3.77V?

Did you connect an inverter to the battery? If so, did you use a precharge resistor? If not, you likely triggered short circuit protection when you connected the inverter due to the surge when charging the inverter capacitors.

Have you disconnected everything from the battery and re-checked the voltage?

 

[Sailor K]

I actually didn't do anything between charging and measuring 3.77V from C- to Batt+. Then I tried to put it into the vehicle to see if it would provide power under load, and it did not. Vehicle did not recognize the battery. I just did disconnect everything. Actual battery voltage (batt- to batt+) is 26.7. I have not yet reconnected the bms to verify what it does. Which do I connect first, the B- or the 14pin sense connector?

 

[sunshine_eggo]

I don't think it matters, but I prefer B- first and then sense wires. An 8S BMS typically only has 9 wires. Why 14?

 

[Sailor K]

There are really only 2 connections to the BMS: the B1 and the sense wires. The youtubes I've seen also show the B- first, then the sense wires. Its a BMS that can do from 7 to 13 cells. So, 8 to 13 are combined and tied to the 8th +. I'll tomorrow reconnect and see if it helps. I have a spare BMS if that one somehow got fried.

 

[sunshine_eggo]

There are really only 2 connections to the BMS: the B1 and the sense wires. The youtubes I've seen also show the B- first, then the sense wires. Its a BMS that can do from 7 to 13 cells. So, 8 to 13 are combined and tied to the 8th +. I'll tomorrow reconnect and see if it helps. I have a spare BMS if that one somehow got fried.

Ah. Makes sense.

 

[Sailor K]

So, I disconnected the BMS and reconnected it. Again, Overkill can connect. There is one alert for BMS undervoltage. Again, the battery has 26.8 V, but output of the BMS is 3.77V. Not sure what's happening.

 

[sunshine_eggo]

Check BMS settings for total battery voltage limits. Those are often not consistent with per cell values.

 

[Sailor K]

Check BMS settings for total battery voltage limits. Those are often not consistent with per cell values.

THANKS!!! Dude, you are AWESOME!!! That was exactly the problem. The per-cell voltage protections were correct, but they were times 13. The BMS will control a 7 to 13 cell battery, and it was supposed to "auto-detect" the number of cells. Well, it may auto detect, but it didn't set the protections properly. I had to change the overall battery over and under voltages to 8x the per-cell numbers. Now it works perfectly!!!! Thank you so much for visiting this forum and helping me out. My next step was going to be to use my backup bms, but it would have had the same problem and I would have been stuck again, after doing the swap.

 

[Sailor K]

Well, good news and bad news. Overkill app can connect, I changed the parameters on my battery, but Overkill app will only display some features. NOT the individual cell voltages. NOT the temperatures, NOT the the power or voltage of the pack. It CAN connect and I CAN change the parameters. I CAN turn on and off charging and discharge, but display does NOT show which is on and which is off--the buttons stay gray. Some labels are truncated. Pack voltage was 28V MOL, and output to red and black wires is the same. The blue elephant won't connect at all. Wondering if I should uninstall overkill app and reinstall it?

 

[sunshine_eggo]

Bummer. I have a JBD 4S 100A unit (not overkill), and it works well.

You typically need to kill the app to ensure it's not keeping the BT connection active when switching back and forth.

 

[Sailor K]

Bummer. I have a JBD 4S 100A unit (not overkill), and it works well.

You typically need to kill the app to ensure it's not keeping the BT connection active when switching back and forth.

Again, the help. Thanks. I killed the overkill app, because it was paired with the bms and would not allow another app to pair. Then went back to the newest blue elephant version. Repaired and success!!! It allowed parameter changes and displayed all the information I need. So I am happy. Overkill was partial function only and an email to them they said they support only their own and I am SOL. So I'll continue with blue elephant and its more than sufficient for my needs.