brain teaser

[wpowokal]

A bit of a brain teaser for those of us who are less informed, so experts please allow time for others to work it out.

Yesterday morning I found my packing shed system shut down, OK not unusual we had strong over night winds probably the volts were too high (no controls on this system), so I changed over inverters as the standby has greater voltage tolerances, all came good, measured the battery voltage and ops its down to 21volts. (24v system)

So I went next door to see the batteries and placed the digital meter across each of the 2V cells in the first of three parallel strings, until I come to one that has a negative 2.1v reading.

Question is how is this so?

Pics to follow tomorrow.

allan

[dnix71]

One cell is shorted out completely and your volt meter is seeing the voltage drop across the shorted cell. Time to buy another cell or two. How much will this cost or do you have spares?

At 21 volts on a 24v setup you probably have one more dead cell. 24v nominal is really 25.2 full charge at rest. 4 volts low is two bad cells. That bites.

[wpowokal]

Spare cells on hand, I started with in excess of 120 of these, I know they need replacing, have allocated $ but maybe they will get through this summer. All other cells in that string had acceptable volts across them for their age.

allan