question

@JohnC BUMP..

The demo version of Victron Connect seems to be capable of supporting 120mv of temp compensation...

Without an actual temp probe linked between the batt and mppt, that 120mv would be risky.

OP, ur links dont work.

Hi @huramentzefix

That must be an earlier CAN mppt. Indeed the manual lists the max at -3.5mV. There is a 2.05 fw listed in VictronProfessional, but I can't read the accompanying .docx file. Which may have something to say, but possibly not, as it's listed as EOL (end of life). You could try it, also see what Victron Connect does with that setting. It offers up to -120mV on my 150/100, but I use -100mV on my generic 'T105's'. My maker must have said "4mV/cell", but I rounded it to an even 100, as this figure is often used quite coarsely (carelessly?) by makers.

That said, I think 59.28V is too high for Absorb, and you'll find they charge most adequately at 57.6V. Trojan's figure may be for 'performance', but for long life I wouldn't go that high. And then a lesser Temp Comp value won't matter anyway.

As an aside, I replaced mine some 5 years ago, and saved the best 6 rejects for a 12V bank. Lightly loaded, charged at a flat 13.5V for a few hours a day, they're still going strong. Gentle does it..

thank you for your answers and suggestions. my batteries are running a bit "hot" (32°C) but they are being charged at 70A at peak times. a temp probe is installed.

I believe to remember to have had running fw 2.05 on another unit which unfortunately caught on fire the other day.

would you suggest setting my voltage to 58.2V then, which then would be 57.6V at 32°C (compensation 0.0035V x 24cells x 7°C)?
or what temperature are you referring to with your suggestion of 57.6V?

what is your absorption time and float V?
if I remember correctly then I changed my absorption time yesterday from 1h or 2h to 4h.
I will check the current towards the end of those 4h to determine my end of absorption time.
how often and at what V should I equalize? mine haven't been equalized for ages ...
do you auto-equalize?

It's 10:30 in the morning here and I can see the batteries being charged right now at 52A.
battery temperature is 31.3°C at the moment.

just now at 10:45 the charger switched to absorption, is at 50A and at 58.4V (which I will drop to suggested voltage once I hear your comments about my temperature)

update: changed absorption voltage to 58.2V and it is now at 57.6V and 20A absorption.
seems low compared to the 58.4V before?
I should probably extend the absorption time to 6 or 8 hrs?

@huramentzefix

Is that heat caused by the charging? That would worry me, but maybe just their location. Trojan don't seem to mention the max charge rate, but in a solar situation I'd hold that to maybe 0.2C, that's 45A. I never see that much, except on a genset, where I might run up to 50A, but very briefly as I'm usually just topping off then.

57.6V @ 25C is what I meant, that's 2.40V/cell, and very common, even in many of Victron's standard charge selections.

My Abs is usually about an hour or so, but if I were 'rushing up' to it @ 70A then it would take longer. My single string of 8 terminates Abs @ 7A (via a shunt/mppt function). That usually happens at a touch above 99.0% SOC, measured by a Smartshunt. Float I use 54.4V, but I'd be happy at your 54.0.

I've never equalized. But I monitor midpoint deviation with that same shunt, and if it ever moved from 0~0.1% then I'd consider it.

With batt temp like that everything can happen pretty fast. I can reach that too in summer, but you must have a lot more panels, and there's really no need to push hard.

I have a 10kVa inverter and when I am running my washing machine (2.4kW), my dishwasher (1kW), then when the water pump kicks in (1kW), my microwave oven (1.7kW), my toaster (1kW), my coffee machine (1.5kW), my vacuum cleaner (1,5kW), electric lawnmower (1.5kW), airconditioner (1kW) i can have a consumption of 6kVa + at times (130A).
That's why I haven't limited the charge current.

I have 3.8kW of solar installed and run my consumers only when the sun is high and out, and the batteries are charged.

I live in the dominican republic. the temperature here is always 30°C that's why.
But I am aware that you are shortening the lifetime by these temperatures. I think trojan and other manufacturers are saying that the lifetime is 50% at these temperatures.
I thought about chilling them with a window air conditioner but didn't get there yet ...

I just meassured my acid density and they were all in the "red". I am just equalizing them and they are currently at 62V steady and not going any higher at C/10.
Acid density is in the white now so it has been mixed through a bit.
you should to my knowledge equalize till to a not any more rising density, of 1.28 (was that @25°C?)

you still haven't told me your battery temperature that you are referring to.