Lithium watch dog

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Monitor progress for the lithium battery pack

Using the lithium battery pack means monitoring the cell voltages. My current voltage monitor is 8S. This involves a lot of taking out and putting back and pulling and moving. There’s gotta be another way.

First test of the lithium 12s monitor.
Found one!

Well. As luck would have it. I found a 12S monitor. And after 6 months of searching I found someone who would sell me one. Well, 5, I had to order 5 to get one!

On to the new 12s monitor test

Well. I have to say these things look way better than I had hoped. And how nice is it to be able to measure all 12 cells at once.

After testing I find them very sensitive and accurate. tho, to be fair, the gauges of their accuracy are probably less accurate than this new monitor itself.

So ’nuff talk. On to the test:

Taking a 6s 24v cell I attach the monitor.

I watch for two days to see if its drawing down any one cell more than another. After two days my conclusion is: not that I can see.

I set the monitor to light an led (included) at a cell voltage of 4.00v.

I then attach a 24v battery charger from an electric lawnmower. Hook up and begin charging. As I charge all cells to 4v. I notice that cell 1 is .02 lower than the other cells. Is this an indication that cell 1 is carrying the monitor load?

As the charger brings the cell voltage up (9-10 hour process, this charger isn’t very powerful) I check in from time.

At 9 that night my girlfriend yells up the stairs “your monitor is flashing” I go down, one cell is flickering to 4 down to 3.8 up to 4. Battery voltage is 23.8. I leave the battery on charge for another hr. Most cells are now 3.99 to 4.02. Lot of flickering up and down of the indicated voltages. Battery voltage is 24. I disconnect the charger.

Result

I leave the monitor on for a week watching the cells. Cell one is .02 lower than the others. After a week its .04 lower than the others. Most of the cells are showing some decline (.02) in voltage. Whether that is settling or load sharing I don’t know. Cell 6 is still at 4. And the led is still lit. Indicating that the battery voltage is fully charged.

Discerned:
  • it only takes one cell v to trigger the led
  • the monitor works accurately as a warning device of cell voltage
  • it is suitable for easy battery voltage cell monitoring
To do:

I will look at how the 8M cell monitor users dealt with the monitor drawing all the power from one cell and modify. I would like to be able to leave it on full time. The other option is to continue using the monitor for occasional monitoring and disconnect when not in use.

That’s it. Huzzah. Another step forward in lithium cell tech for off grid use.

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