Trojan batteries not charging

[pietbez]

Hi everybody.
i am new to this forum, and must admit that i don't have a boat and i don't sail. i have come here because whenever i search for a solar related question i end up here. hopefully someone will be kind enough to reply regardless.

my setup:
100% off grid system
4 x 260w panels 8amp 36v open circuit. connected in series.
1 x

Tracer 4215BN MPPT charge controller.
6 x Trojan T105 batteries in parallel/series config to give a 12v system.
1 x 3000w inverter.

my Trojans are 2 months old and the setup has been working very well. usually my bank is fully charged by 10h00 11h00 in the morning and the controller goes in to float charge for the rest of the day. i never drain the bank below 12.2v at night.
the last couple of days the batteries start charging when the sun comes up, but then once it reaches 13.6v it just stays there. it needs to reach 14.7v before it goes into float but it just doesn't get there. the controller is putting about 40amp at 13.6v into the bank but the voltage just doesn't rise.

does anybody know why this might be happening? we are currently in the middle of a heat wave with temperatures in the 40's (Celsius) but i don't think that should have such a big effect???

any ideas or suggestions would be appreciated.

thanks
PietBez

[sailorboy1]

Not that uncommon. Sometimes my system doesn't go into absorption for a few days depending on where they started for state of charge and the sun level.

40 amps at 13.6V is 544W out of your 520W of panels so you are getting full power. How much power are you using at the time and/or how much is actually going into the batteries? It sounds that you just aren't getting up to absorption, maybe because you are taking enough out of the system at the same time to not allow the batteries to charge up more.

Or since you say the batteries don't get "below" 12.2 at night, which is pretty low really for a 600AH plus battery bank , that the batteries are just discharged more that you think and now are taking all the bulk charge you are supplying and not getting back to full charge.

[a64pilot]

You have a generator or other means to get them to full charge, then measure specific gravity of the cells to determine if you need to equalize?

I'd suspect you have a few months of partial SOC cycling and need to equalize, getting to float may not mean your fully charged, you may be well below a full charge.

[pcmm]

Check your panel temperatures. PV panels have a temp at which they start to collapse and produce less voltage than you think. But something else isn't right here. you say you were getting to float voltages by 10 or 11am. but that overnight you are getting down to 12.2v that means you're pulling 300-400Ah out of your battery bank each day? Also means that it should typically takeat least8-10hrs at 40amps bulk stage to get your batteries topped up. but really that last 10% takes a lot longer.

Something has changed. have you added ALOT more load to the system recently?

do you know how much draw is on the system typically?

[skipmac]

Originally Posted by sailorboy1

Or since you say the batteries don't get "below" 12.2 at night, which is pretty low really for a 600AH plus battery bank , that the batteries are just discharged more that you think and now are taking all the bulk charge you are supplying and not getting back to full charge.

Another related issue. Is that 12.2V with any load connected or with all electrical draw switched off? It can make a big difference.

A battery could be fully charged but if a heavy load is connected drawing 20-30 amps or more from the battery, the voltage might measure 12V or even less. Disconnect the load and if you haven't drawn too much out of the battery the voltage will quickly rise to 12.5-12.6V which is fully charged for a lead acid battery.

[pietbez]

thank you all for your valuable input. tomorrow is another sunny day. (i am in south Africa, so its mid summer here)
i am going to disconnect all load to the system tomorrow and just let the batteries charge the whole day long to see if i can get better results.

i will be back here tomorrow night to post my findings. thanks for all your help. i do not want to damage my bank. it cost me an arm and a leg. with the south African currency being so weak, these batteries don't come cheap over here.

[barnakiel]

It sounds as if your batteries are fine but the regulator found a reason to hold the voltage at 13.6.

Dig deep into your regulator specs: e.g. some regularos will charge to the high point (14.8) only if and when a number of conditions are met (over say a 10 day period). Sort of like they have a minimalistic learning (better said: adapting) algorithm.

BTW if the regulator keeps the batts at 13.6, they still get properly charged, even if "100%" charging may last a bit longer this way.

b.

[hellosailor]

You might also want to separate the batteries, try to charge just one or the other. If there is an internal short or similar problem in one battery, separating them will show that up very quickly.

[skipmac]

Originally Posted by barnakiel

It sounds as if your batteries are fine but the regulator found a reason to hold the voltage at 13.6.

This was also my first thought (guess?) based on somewhat limited information from the OP.

Originally Posted by barnakiel

BTW if the regulator keeps the batts at 13.6, they still get properly charged, even if "100%" charging may last a bit longer this way.

b.

Especially since the controller is showing that many amps out, the batteries are still getting charge.

[senormechanico]

I agree with all the above.
And that's not usual for me.

[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

[sailorboy1]

You sure the controller is rated for the panels?

[GordMay]

Greetings and welcome aboard the CF, PietBez.

Glad you solved it!

From the manual:
“Controller Overheating
If the temperature of the controller heat sinks exceeds 85°C, the controller will automatically start the overheating protection and recover below 75°C."
➥ http://www.i4wifi.cz/img.asp/?attid=315022

[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.

[a64pilot]

Good, the simplest cures are always the best