Saturday, February 27, 2016

BOTTOM BALANCING THE LAST BETTER PLACE MODULE

We have had a few nice weekends in the last half of February, so decided to start bottom balancing the third Better Place battery module. 

The terminals and connectors were  all cleaned with scotch bright and a thin coat of Noalox anti-oxidant compound was applied to the them. The connectors were positioned on the terminals and a small drop of Loctite was applied to each of them before threading them into the terminal. A socket on a Dewalt drill with the torque setting on 3 was used to tighten all of the terminals.  

Then voltages were taken on each half cell and most of them were in the 3.85 volt range but one cell was only 3.65, so the volt meter was hooked on that half cell to monitor the drain down of the module.

Eye terminal connectors had been previously crimped onto the end of an extension cord and two 1000 watt flood lights are used to draw down the module. When the voltage reading on the lowest cell approached 3 volts, the individual half cell readings will be taken again and a different cell will be monitored if necessary. I will drain the module down to 88 volts or 2.75 volts/half cell and let the module set for awhile, as it will drift back up in voltage in a few hours. Then a 100 watt light bulb is hooked up to allow the voltage to be drawn down slowly. Finally a 5 watt night light is hooked up that allows the voltage to be drawn down even more slowly. This is the only way I have found that will cause the voltage to finally stabilize and not keep drifting back up. Even after that, over a couple of weeks, the cells will drift back up to around 3 volts. 

After the initial draw down and couple of weeks sitting, individual half cell balancing is done with a JLD404 and a 4 volt flashlight bulb. The JLD404 is set so it drains the half cell down to 2.75 volts and does not turn back on until the cell drifts back up to 2.95 or so. These are just hooked up and allowed to cycle until the half cell stabilizes under  2.95 volts.


BOTTOM BALANCING MODULE


With spring just around the corner, I want to get a running start to get the Fiero back on the road with all three modules installed.

Thanks for visiting,

Randy
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