Battery Questions for Trojan T-105's setup

rogermedia

Battery Usage Question: We have 4 Trojan T-105's. We have a Tri-Metric 2030 Battery Monitor. We are solar powered with 640 Watts going to a 60Amp Morningstar MPPT controller. For the most part the meter never reads under 80% remaining charge. From reading the Trojan manual they say safe usage is all the way down to 50%. Others have told us not to let it go below 70%.

What is a safe operating range? Typically we get back to 100% everyday but sometimes it might be two or three days till a full charge occurs again.

We have been going for 5 months now and only been running off the batteries for the last month or so while boondocking. The water levels have barely dipped below the fill lines and I fill them back up with distilled water. I also check the water every 30 days.

At this point I have not done an Equalizer charge. I am thinking of grabbing a hydrometer to test the specific gravity of each cell.

Any thoughts and recommendations are highly appreciated.

BB.

Re: Battery Questions for Trojan T-105's setup

Welcome to the forum Roger.

Batteries and what to do with them can generate a lot of discussion... As I see it, run your batteries as you need them. Discharging daily to 75% Sate of Charge is fine... Going down towards 50%--Just part of life. Try not to go often below 50% SOC and never below 20% SOC--That can limit their life or even kill them (going below ~20% SOC).

For a Hydrometer--Try this one:

http://www.solar-electric.com/midnite-solar-battery-hydrometer.html
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Just rinse out out with a couple squirts of distilled water after you have completed your measurements for the day.

For good quality flooded cell lead acid batteries--Their cycle life curve is pretty much "flat" from 80% to 20% SOC (one that was posted here a while ago).

So, if you cycle 20% out of the battery or 40% out of the battery (depth of discharge) you will still get a total of ~XYZ AH of cycles... I.e., you will get 2,000 cycles from 100 to 80%, or 1,000 cycles from 100% to 60%.

Some light reading:

http://www.windsun.com/Batteries/Battery_FAQ.htm
http://www.batteryfaq.org/
http://batteryuniversity.com/

In theory, as long as your battery bank does not go below ~50% (or at least very often), and you get back >90% state of charge at least once a week, you are doing OK.

Do not let the battery sit unused below ~75% -- It will start to sulfate (really sulfate "faster"). Keep batteries from getting too hot (cooler batteries last longer). Batteries usually get hot when charging at 90% or higher SoC or during equalization.

Some vendors say to equalize once a month... Others say to equalize when the high to low cell specific gravity spread is more than 0.015 to 0.030 or greater.

For other general Solar RE and project information, there is a lot to read here:

http://forum.solar-electric.com/showthread.php?5556-Working-Thread-for-Solar-Beginner-Post-FAQ

-Bill

rogermedia

Re: Battery Questions for Trojan T-105's setup

Great stuff! Thanks for the response. We figured things we going ok but wanted to make sure with some human interaction. I have bookmarked the links and will be educating myself further.

Thanks again!

Audiomaker

Re: Battery Questions for Trojan T-105's setup

BB. wrote: »

For good quality flooded cell lead acid batteries--Their cycle life curve is pretty much "flat" from 80% to 20% SOC (one that was posted here a while ago).

So, if you cycle 20% out of the battery or 40% out of the battery (depth of discharge) you will still get a total of ~XYZ AH of cycles... I.e., you will get 2,000 cycles from 100 to 80%, or 1,000 cycles from 100% to 60%.

-Bill

I kinda stumbled on this thread, but that confirmation is what I was looking for over in the "Best battery for generator only" thread (in Solar Newbies forum).

That being the case (that you still get xyz AH of cycles) really makes me question if it isn't better to drain to a 65% to 75% depth of discharge when a generator is being used as the charging source.

On grid, or solar (or water or hamster), I am in agreement with the shallow DOD, but with the cost per kwh running a generator, I'm starting to think that a deeper DOD might be betting in the big picture *only* when running on gen power.