I never get below 85%

Coach Dad · September 2012

Hi All,
This is my off grid system:
* 24V 305 AH AGM battery bank.
* 1410 Watts Solar Panels
* 60 A MPPT CC
* 4000 W Inverter

I've been running my off grid system since the beginning of May. The system is only used on weekends and the State of Charge never goes below 85%. (Actually it only went below 90% one time when it hit 85%)

Because I only use 5 to 10% of my battery from the time the sun goes down until it starts charging again,... The maximum power I see in the mornings is only about 700 watts. That tapers down quickly and I'm normally at full charge by 10:30 AM.
This comes out to about a 6% recharge rate 700/((305*28.6)/.77)=6%

My question is... Since I'm only recharging at a rate of about 6% max on a daily basis (Even though I have 13% capibility) should I be doing a EQ every now and then? I know everyone says not to EQ the AGM's so that is why I'm double checking.

westbranch · September 2012

Re: I never get below 85%

CD, what does the batt manufacturer recommend? every brand is different...

inetdog · September 2012

Re: I never get below 85%

westbranch wrote: »

CD, what does the batt manufacturer recommend? every brand is different...

And even more unfortunately, what each manufacturer means by equalization can vary too, as can the interpretation that a charge controller uses for the same term.
When dealing with AGMs, you need to know exactly what the CC is trying to do, rather than just set a voltage and let it run. Keep a close eye on the battery temperatures and voltages.

And for the most part, a CC connected to panels may not deliver for long enough to do the equalization job correctly. Doing it right may require using a line or generator powered charger.

niel · September 2012

Re: I never get below 85%

eqing fla type batteries came about due to imbalances on the different batteries in a battery bank. are you seeing imbalances? in fact have you been tracking each battery's voltage? if you are and see an imbalance then you need to correct the cause of the imbalance. could be a bad wire or high resistance showing up on a connector, fuse, etc. you could try an extended absorb charge and/or switch battery positions. if memory serves you have concordes and the last thing i'd advise would be an eq charge as that's a desperate measure and not a maintenance thing as i've told you before.

they're your batteries though and you can do what you want to them.

silvertop · September 2012

Re: I never get below 85%

niel wrote: »

eqing fla type batteries came about due to imbalances on the different batteries in a battery bank. are you seeing imbalances? in fact have you been tracking each battery's voltage? if you are and see an imbalance then you need to correct the cause of the imbalance. could be a bad wire or high resistance showing up on a connector, fuse, etc. you could try an extended absorb charge and/or switch battery positions. if memory serves you have concordes and the last thing i'd advise would be an eq charge as that's a desperate measure and not a maintenance thing as i've told you before.

they're your batteries though and you can do what you want to them.

I follow what Niel said I only EQ when I have an imbalance between my batteries . I try to watch my chargeing as the seasons change and I try to get a good Absord charge so I can limited my need to EQ...

PNjunction · September 2012

Re: I never get below 85%

What agm's are you using?

If it were me, every once in awhile I'd make those batteries go through a proof of performance test with much larger loads to help expose any weaknesses, and know that I could rely on them if the unforeseen happens. Maybe take them down to 60% DOD twice a year or so.

The other issue is that your batteries might die of old-age faster than your cycle-life. Daily is one thing, but weekly with only 90% drawn - that's almost a float scenario in my book. I think this is a good system if your needs grow, or if the batteries prove to be reliable for much heavier loads as a nice emergency backup if you got stuck up there for a week or two.

In my personal, but limited experience, tickling agm's may not be the best thing for them. I had a badly sulfated agm that never revealed the problem until I put a real load on it. In the meantime, my dinky loads were little more than surface-charge removal, the batteries charged up quickly, (sulfated), but failed with a real load test.

niel · September 2012

Re: I never get below 85%

in reading pnjunction's comment i think it may be a good idea to cycle them down further (no more than 50% of course) just to flex the batteries some. i do this with mine every week or 2, but even monthly would be fine.

Coach Dad · September 2012

Re: I never get below 85%

niel wrote: »

if memory serves you have concordes and the last thing i'd advise would be an eq charge as that's a desperate measure and not a maintenance thing as i've told you before.

Niel- Correct.. they are Concordes.. and I have not done any EQ's based on your recommendatins.

The manufacturer recommended a 1 hr eq every 30 days but I've been following Niel's advice instead..

Nope- They are fine,, there is nothing wrong with them but I want to keep it that way.

So- Are you guys suggesting that I turn off the Charge controller for a Saturday so that it goes down to about 80%? or should I even run some extra loads to get it down to 70%?

waynefromnscanada · September 2012

Re: I never get below 85%

Coach Dad wrote: »

So- Are you guys suggesting that I turn off the Charge controller for a Saturday so that it goes down to about 80%? or should I even run some extra loads to get it down to 70%?

Quite a few people "in the know" do recommend letting deep cycle batteries actually be cycled from time to time. However I'll throw this out there - - my battery pack of six L-16 is now over 10 years old and has only been taken down to perhaps 5% from full charge a few times a year, especially since I got my micro hydro going some years ago. I suspected the batteries would be loosing capacity by now, and they probably are, but not that I can notice. Thought they were failing a while back, but turned out to be a volt meter problem. Normally my hydro handles the two freezers and fridge etc overnight and on overcast days, so the batteries don't really drop at all, but the severe drought we've had this Summer resulted in the hydro being shut down for a month, and I was very surprised to find battery voltages of 12.6/7 in the mornings, and that was without a real rest as the loads were coming and going all night. The drought finally ended last wk, so with the hydro back in the mix, this morning's voltage is a typical 13.6 without any loads. Surge loads do however put sharp but short drains on the batteries. I consider myself EXTREMELY lucky with these "Power-Battery" (I believe made by East Penn) units, they've been awesome batteries, and I fear I'll never see their likes again once they finally do need replacing.

vtmaps · September 2012

Re: I never get below 85%

waynefromnscanada wrote: »

my battery pack of six L-16 is now over 10 years old and has only been taken down to perhaps 5% from full charge a few times a year
<snip>
I consider myself EXTREMELY lucky with these "Power-Battery" (I believe made by East Penn) units, they've been awesome batteries, and I fear I'll never see their likes again once they finally do need replacing.

It seems that you could get by with just two L-16s. Perhaps they wouldn't last as long.... but if you could get 4 years out of a pair, that is the same as getting 12 years out of 3 pairs. Are your peak loads so great as to require 3 pair?

--vtMaps

I never get below 85%

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