Morningstar Sunsaver MPPT controller: AGM vs "sealed"

[kenl]

The controller's program is for a 3h equalise, but in any case  just thought that equalising and sealed didn't go well together...

Rgds

Damon

 If your using your batteries for cyclic use a short eq charge once they are fully charged is OK. BUT not when they are in 32f or below enviroment and only eq them 1-2 times a year if they are starting to read different voltages when compared to each other. It is best to take the voltage readings when they are in a discharged state. Reading them in float will tell you nothing unless one battery has serious issues.  A 0.1v difference is not a good reason to eq the bank. As for the charging profile, your battery is a AGM which also means its a SLA battery. Kinda confusing but set the charge controller to AGM with no eq schedule. These batteries are also not very forgiving if the bulk, absorb, and float voltage settings are not correct so be careful there. Over charging is deadlier to them then under charging at least for my batteries. I have been using AGM's for 5 years now and have had no problems once I bought a GOOD charge controller. Luckily my 1st set only cost $25 and a drive to Chattanooga. But they could of lasted a couple more years had I known then what I do now.

kenny

seemed like a good idea at the time

[DamonHD]

Hey, thanks for that: yes, AGM setting without eq (most of the time) did seem like a good idea.

But the original supplier sent me something completely wrong (flooded VRLA hybrid), so I rejected them and bought some gels which are now in.

Rgds

Damon

[DamonHD]

Some half decent sun today while I was away, SLA up to 12.8V, nothing caught fire.

Took the opportunity this evening to tighten all connections and look/sniff for any signs of overheating.

Rgds

Damon

[DamonHD]

Had an odd glitch on Friday: the off-grid solar controller had been showing green ("full") Thursday night but on Friday morning even though I was seeing 12V and the batteries were charging the LVD cut-out.  Its threshold is set to 11.5V.



I assume that one of the new connections wasn't great so I went and tightened everything again.

As you see the SLA system recovered by itself in a few hours.  I put my server back on grid in the gap.  The LiFePO4 gave me long enough to notice and switch over gracefully.

Anyhow, today was quite a good day for solar so the batteries have had a decent charge and our grid-tie system probably generated more than we consumed today (first time this year).

Rgds

Damon

PS. Thought my controller was cooking my gel batteries trying to float them at about 14.5V instead of 14.0V, but then I realised that temp where they are is just about 0C, so with temp comp that's fine.  Until now my main SLA set has been inside and thus much nearer the nominal 25C of the uncompensated set points.

[BrianSmith]

Damon,

If you put an aerogel wrap on your batteries, it might make sense to try to heat them a bit to keep them from getting real cold where there capacity will suffer.  That is if you can store away more electrons in the extra heated capacity than you burn trying to keep them warm.  How good of an insulator is aerogel in R value?

Just a thought. 

Brian

[DamonHD]

Aerogel is ~0.013W/Km, about 1.5--2x better than the best rigid foams for example.

For the time being I've done a small amount of insulation with some expanded polystyrene packaging (from some solar panels!); about 1cm or so.  I won't do any more until I get a remote temp sensor for the controller, but then I might bundle it up a bit.  Meanwhile I might redirect the aerogel remains to our loft to do tricky bits such as the loft hatch!

Rgds

Damon

[kenl]

I read 12.5V as ~90% SoC...

Rgds

Damon

 Here's a handy chart for SOC of a battery. Keep in mind this is open circuit voltage. It is not of use if you use the Northstar AGM's and the like for they have an equation to give you state of charge. But this is good for deep cycle wet batteries (or so they claim). If you are using Agm batteries your open circuit at rest should be 12.9v to 13.1 for a fully charged battery.

kenny

seemed like a good idea at the time