Opinions on my battery charging profile (solar)

[ewarnerusa]

I am curious about what others with battery charging expertise think about what I'm doing to my batteries. Am I damaging them or shortening their lifespan?

Quick background, I installed 280 watts of 12V solar panels with a fully programmable Morningstar Tristar 45 controller on our new TT in 2012. At max sun I can see 15A from the panels. It had OEM 2x12V batteries that I swapped out for 2x6V Costco GC batteries in 2013. I installed an inexpensive ebay 1500 watt PSW inverter in 2013 that does not like to operate at voltages above 14.8-ish volts. So I've utilized the programmable features of my Morningstar to accommodate this, but I'm wondering if my batteries will suffer from not enough 14.8V+ charging.

My normal charging profile has 14.4V for the bulk and absorption setpoint. It will drop from absorption to float when PMW duty cycle drops to <15% for 10 minutes. I have voltage sense wires and temperature compensation, but I have it programmed to not do the temp compensation at lower than 70 degrees F. This is because I don't want the controller charging at higher than 14.4V during normal use so it plays well with the inverter. I have also programmed an "equilization" to occur every third day at 14.9V with the same temperature compensation cutoff. So when the sun is bright I hit the batteries with up to 14.9V for 3 hours every 3rd day. My logic is that this at least gets the batteries some 14.8V+ time while hopefully minimizing the impact on being able to use my inverter. During winter storage, I change the temp compensation cutoff to much colder since the TT/inverter isn't in use. I think it have it adjust down to 32 degrees F.

Do you think my 6V Costco GC batteries are getting enough charging to stay healthy?

Thanks.

[jrnymn7]

sweet! I'm going with 6ga, so you definitely nailed it!

[ewarnerusa]

I've got voltage sense wires and they are getting the full setpoint voltages. I have hooked my laptop up to the Morningstar many times to confirm it. There is about a 0.1V drop that the controller compensates for. I'm using 4 gauge wires.

[jrnymn7]

ewarner,

Have you checked at the batteries to see what they are actually getting, voltage wise? There could be some significant voltage drop if you used standard 10ga wiring.

BFL explains it on pages 4 and 5 in my "pwm controller question" thread.

[ewarnerusa]

pianotuna wrote:
Hi,

You don't mention an equalize "session". I believe Trojan suggests 15.5 volts for that. Perhaps consider doing so once a month?

Nice choice of charge controller. I'm surprized that you only see 15 amps from 280 watts.

The lack of the equalize is what causes me concern. I'm using the auto equalize feature to do my 14.9V every 3 days rather than a 15.5V monthly blast. I have one of those floating bubble specific gravity gauges, but I haven't used it since last summer.

My 12V panels are rated 8A max (2 x 140 watt Cynergy brand), so seeing 15+A seemed right to me? They are flat mounted.
https://www.solarblvd.com/product_info.php?cPath=1_269&products_id=2668

I like the controller. I often contemplate doubling my panel wattage so it is more fully utilized. I built the system with expansion in mind, but so far have not been able to justify buying more based on our usage.

[jrnymn7]

Let the batteries tell you how they are doing... SG readings, tiny bubbles while charging, etc. Some batts need several hours at 15+v while others do well at 14.6v. And pay close attention to battery temperature. You may have to improve battery compartment ventilation for the summer months, even at 14.4v, to avoid excessive gassing.

[pianotuna]

Hi,

You don't mention an equalize "session". I believe Trojan suggests 15.5 volts for that. Perhaps consider doing so once a month?

Nice choice of charge controller. I'm surprized that you only see 15 amps from 280 watts.

[BFL13]

The way to tell is with an hydrometer to see if they are at "baseline" (as new after your initial overcharge) SG when you are at your idea of "full"

On full- time solar in the summer months I have the controller set to 14.8v which the 6v batteries get to after lunch sometime, then it drops to 14.4v the rest of the day.

If that subsequent time at 14.4 is long enough, the Trimetric AH count gets back up to zero and then goes "over" into positive numbers. If the sun is still out that keeps going till it is about 10AH "over" and then the SG is up to baseline. I reset the AH counter to zero after dark.

If the AH count does not go "over" by at least that much, then the SG won't be all the way up that day, and I do not reset the Trimetric. To make up for those days it does not get that high, once in a while I do an equalize to 15+, but that is not often needed.

If I want to use the inverter when the voltage is over 14.9, I just turn off the solar for a minute (switch between panel and controller so you don't have any time with panel on controller with no battery connected), which brings the voltage right back down, start the inverter and then turn the solar back on.