[RE-wrenches] Trojan L-16s

[Larry Crutcher, Starlight Solar Power Systems]

Hi Drake,

It always concerns me when I hear that a battery bank reaches absorb setting very quickly. It typically means one of two things: very few AH were removed from the bank; the battery bank has sulfated cells due to chronic undercharging. Far too often I find the latter to be true.

Healthy batteries will accept current and hold the charge voltage down with a fairly linear, slow climb to absorption voltage. Sulfated batteries do not accept current well which allows voltage to climb rapidly as the battery presents little load on the charging system. I'm not sure how this plays into your original post about a bad cell but it seemed worth mentioning. 

My opinion is to aggressively charge, by using higher voltage, large flooded batteries. This is especially true when the PV system is moderate or undersized. 29.6 volts is what Trojan recommends. You can go as high as 32 volts on the L-16's but make sure the temperature compensation is installed properly and working. You will use more water.

One last comment, I highly recommend that ALL off grid systems have a battery capacity monitor installed. It's kind of like flying an airplane without a fuel gauge…it might not end in disaster.

Larry Crutcher
Starlight Solar Power Systems



On Jul 18, 2013, at 1:11 PM, Drake <drake.chamberlin at redwoodalliance.org> wrote:

Tom,

The batteries usually reach absorb voltage shortly after the sun hits the array. The reason the bank wasn't working correctly is that one cell was dead in one of the batteries. 

I could increase the absorb time to 4.6 hours and the voltage to 29.6, especially since the bank has a new battery. That is longer and higher than I'd previously heard recommended. What would be the effect on water consumption?  How did you calculate the absorb time? 

Thanks,


Drake