Higher Absorption Voltage, Less Top Charging

[BFL13]

Mex has mentioned this a few times. I have some real life experience of that now I have the right equipment to see it. This would relate to the battery blurb advice on doing overcharges every so often above 15v.

First, on solar daily for months, I expected to have to do an equalize every month or so, because the 6v batts only got to 14.8 for a time at the end of the day and did not always get to full. However, when they did get some time in the day at 14.8 and the AH counter said they were full, their SG was up to "baseline SG". This was a big surprise to me. However they also were doing shallow cycles not getting down to 50% each time.

Second, after off- grid no solar doing 50-90s, I would get home with low batteries to do the last recharge from the camping cycles, plug in, and let the 13.8v converter bring them up by next day.

But their SG was still "fair". At that point I put the VEC1093DBD on them which first got them to "full" at 14.8v, but the SG was only "good" but not up to "baseline SG" (my target SG I have seen when they are "truly full" ) So next I ran the Equalize on the VEC which got the SG right up where it belongs. Been doing that for some years now.

OK, so what's new? I recently replaced the old 13.8v converter with an adjustable voltage (PowerMax as it happens, but any charger that can do this would work) and used it for the first time to do the home recharge on return from some 50-90s.

Batts were down 190 AH about 55% SOC. I set the voltage to 14.8 and plugged in. By 10PM (same day not next day as before) was down 6 AH so I lowered the voltage to 13.6 and left it overnight. So this morning it is up 1.7 AH and the SG is back up to "baseline SG"!!! So I don't need to haul out the VEC and do an overcharge. Amazing 🙂

This is not the same as just getting the batts to 14.8 and then dropping to a lower voltage for the Absorption Stage. It means do the entire Absorption Stage at the higher voltage.

I can't say how this compares with the four hour timed 14.4 a PD converter can do, but doing that has to help. Of course, that might just mean the "baseline SG" was established using that 14.4, so the SG is not as high as it could have been, but the owner is happy to see it 🙂

Iota drops to an eight hour 14.2 for the Absorption Stage. I think that voltage would be too low to see the proper baseline SG at the end of it, but I don't have one. Obviously any 13.x voltage is below gassing voltage and could not do the job. That's what happened with my "learner set" of 6s, which never seemed to get in the "good" SG zone using that 13.8v converter, so I got the Vector charger which solved that.

This adjustable voltage converter idea is just great. The Vector charger did the same thing, but it shuts off when the batts are charged, so it can't act as a converter. The adjustable gets you the high voltage Absorption Stage for as long as you want (manual though--no timer) plus it stays on like a converter should at whatever voltage you like.

[pianotuna]

Hi BFL13,

I'm not surprised by the solar results. Shallow cycling is easier on the battery bank.

Thanks for posting your results.

[pianotuna]

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[MEXICOWANDERER]

This is the magic. No IC's or transistors to blow. It's waterproof and rated for 100,000 + cycles and it rated at 15 amperes @ 120vac. I have FORTY YEAR OLD Intermatic timers that work as good as the day they left the factory. They are commercial industrial rated.

[MEXICOWANDERER]

All smiles here BFL. Isn't it fun discovering what free-lance charging control can accomplish? Play conductor and the orchestra responds.

What a lot of people fail to see is 99% of what is discussed here is only necessary one or two times to tweak. Then it becomes automatic. I spend TEN SECONDS A DAY twisting the dial of an Intermatic timer. Times 30 = 300 seconds a month. Times 12. 3,600 seconds. An hour per YEAR. Time to Top Charge? I twist the timer 20 minutes additional time.

On the way back from the gen shed, I pick a cantaloupe, papaya, some mangoes and bananas for a fruit salad breakfast. A hook on my now empty coffee cup allows me to hang it on my belt and use my one hand and a bag.

Then I go inside, swallow salt tablets and shower off all the sweat generated by this rigorous trial-by-fire physical and calculus grade mental overload.

Of course there are battery watering days, and the ubiquitous weak sister cell dipping days. I promise the kids I will return by sunset. They giggle and follow me. But are prohibited from entering the shed.

Doing things the right way makes farce the thought that correct battery management is either complicated or time consuming. It is neither. If I need to recharge, I start the generator and a spare few minutes later voltage is at 29.4

Even the generator is on a timer. I know from negative amp hours how much gen run time returns the batteries to 98-102% CEF or 108-114& actual. Yawn.