Trojan batteries not charging

[skipmac]

Originally Posted by pietbez

its a 40Amp controller. its been working fine until now, but like i said, we are currently in the middle of a heat wave. the outside temperature today is 42 Celsius.

but with the fan on the controller, the temperature comes right down.

42C??? That is hot. At that temp I would overheat.

[Maine Sail]

Originally Posted by pietbez

thanks everyone for all the help and suggestions.

i think i have found the problem. i decided today to disconnect the load and let the batteries charge at full capacity. I sat next to the bank for a few hours to monitor it manually.

as the morning sun became hotter the charge controller also became hotter, to the point where it would shut down, cool down and reboot. it went into a loop of shutting down, cooling, rebooting.

solution: i mounted a 12v desktop PC fan on the heat sink.

voila! problem solved.

my bank is currently at 14.8v and equalizing.

thanks again for all the replies, what a great forum you guys have here.

PietBez

The fan is NOT a cure to your problem....

Your controller is using a local internal ambient temp compensation feature, which is really a pretty poor design, especially in a controller with poor cooling which results in incorrect voltage adjustments..

I would urge you to look into an external temp sensor that mounts directly to the batteries and a controller that allows you to program the temp compensation gradient. At 42C, 14.8V is far too high a charging voltage. At 42C (measured at the battery case NOT the controller or air temp) the max charge voltage should be 14.3V.

For Trojan batteries the temp compensation is -0.005V per cell or -0.03V per 12V battery for every degree C above 25C.

So for a 12V battery:

42C - 25C = 17
17 X .03 = 0.51V
14.8V - 0.51V = 14.29V

[a64pilot]

Originally Posted by pietbez

my bank is currently at 14.8v and equalizing.


PietBez

I'm not sure he meant it or not, but I took this to mean that he was equalizing the bank, not charging, but if his charger does not measure batt temp and adjust off of that, it is deficient, especially at those temps. I haven't seen temps like that since my trip to South West Asia.
I believe that is 108 F for us Americans?

[pietbez]

yes, after a few days of not taking full charge i wanted to equalize the bank. but also, when i talk about 42c, that was the outside temp today, not the temp at the battery bank. the batteries were not overheating during charge or EQ. it was the charge controller getting hot. so the fan is just a temporary fix to get me through this ridiculous heat wave. under normal weather conditions the whole system works fine.
but yes, i agree, i do need an external temp censor for my bank