Charging starting batteries

Iceni John · September 2015

I'm temporarily using my old 8D starting batteries as interim house batteries while I'm still working on my bus conversion. I've bought two new Group 31 starting batteries instead, so I've demoted my old 8Ds because they still have some life left in them. Yes, I know that SLI batteries are not deep-cycle, but for the time being they'll be fine as a way of checking that everything works as planned, and I won't be discharging them more than a few percent. When I'm closer to needing real house batteries I'll buy some golfcart batteries, but I'll wait as long as possible before buying them. One of the 8Ds is a DEKA 1400 CCA, the other is some Chinese no-name 1300 CCA, and they're both almost seven years old.

My question is how should these 8Ds be charged from my Morningstar TS-MPPT-60 charge controllers? I set the CCs to 14.7 volts Absorb and 13.5 volts Float (Morningstar's setting 6), but should they have a lower Absorb voltage? They bubble quite a lot during Absorb, more than when I charged them with my Schumacher charger (which I suspect may have been under-charging them?). Needless to say, the East Penn website has no charging info for them, presumably because they think that nobody's fool enough to be charging them this way!

I'm not too worried if these batteries die completely in a year or so, but I just want to squeeze the last possible bit of life out of them for now, and solar seems a good way to do that.

Thanks, John

PNjunction · September 2015

Iceni John wrote: »

My question is how should these 8Ds be charged from my Morningstar TS-MPPT-60 charge controllers? I set the CCs to 14.7 volts Absorb and 13.5 volts Float (Morningstar's setting 6), but should they have a lower Absorb voltage?

Sounds reasonable, but you are in luck. Do a search for "Deka Solar Voltaic Batteries Renewable Energy Charging Parameters". It is the canonical 1913.pdf document. Inside you'll find a great chart for typical 3 stage charging for flooded, agm, or gel.

They bubble quite a lot during Absorb, more than when I charged them with my Schumacher charger (which I suspect may have been under-charging them?).

Oh yeah, mismatched batteries not a good idea. If your Schumacher is a "speed charger", it may have been too aggressive with them if they were healthy from the start. If you place a voltmeter on the battery terminals, and follow the charge cycle with min/max hold on, and perhaps with your own ammeter inline, you may or may not like what you see.

BB. · September 2015

I believe this is the PDF link: [h=3]1913 Renewable Energy Charging Parameters[/h] -Bill

Iceni John · September 2015

Thanks for the DEKA charging info. However, I'm still not clear if those charging parameters are for deep-cycle batteries (as the title's "Renewable Energy" infers). or vehicle SLI batteries such as my two 8Ds. I was told that deep-cycle and SLI batteries have very different charging needs, hence my original question. I know that my 8D batteries aren't much longer for this world, but I just don't want to prematurely hasten their inevitable demise! If I can squeeze another year's life from them as "play" batteries until I get the real house batteries later, I'll be happy. I'll keep a close watch on their electrolyte levels and SG readings anyway - curiously, the DEKA seems to be in worse shape than the Chinese one, as it needs water more often and it doesn't hold its charge so well.

Thanks, John

lkruper · September 2015

PNjunction wrote: »

Sounds reasonable, but you are in luck. Do a search for "Deka Solar Voltaic Batteries Renewable Energy Charging Parameters". It is the canonical 1913.pdf document. Inside you'll find a great chart for typical 3 stage charging for flooded, agm, or gel.

Oh yeah, mismatched batteries not a good idea. If your Schumacher is a "speed charger", it may have been too aggressive with them if they were healthy from the start. If you place a voltmeter on the battery terminals, and follow the charge cycle with min/max hold on, and perhaps with your own ammeter inline, you may or may not like what you see.

I am surprised that the bulk charging for FLA batteries is 30%. Why so much higher than 10% of the C20?

PNjunction · September 2015

lkruper said:

I am surprised that the bulk charging for FLA batteries is 30%. Why so much higher than 10% of the C20?

I think this is significant and should be tested! At least for this brand. I think that is key - follow the manufacturer's specs.

This would be a GREAT advantage for Deka/East Penn, to be able to exceed the more common C/12 to C/8 rule for FLA and provide faster charging, critically important for low solar insolation areas.

That's the thing - much of what we say are generalities that are deemed *safe*, but at the same time, might not actually mean efficient for a particular brand.

Maybe someone out there can verify this by taking a Deka FLA up to 0.3C. Note that they are referring to the 8C11, 9C11, 8L16, GC15, and DC27 models. Not sure about the others.

oil pan 4 · September 2015

Which C rate do you base charging rate from? The 10 hour amp hour rating or 20 hour one?

The 20 hour amp hour number seems to be the standard for most things.

inetdog · September 2015

oil pan 4 said:

Which C rate do you base charging rate from? The 10 hour amp hour rating or 20 hour one?
The 20 hour amp hour number seems to be the standard for most things.

The 20 hour rate is the base used for C/8 type recommendations.

Charging starting batteries

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