Electrolite

[duggybuggy]

I don't claim to know much about this stuff, so don't be misled by me if I have it wrong. But it seems to work well for me.

I got a new wet cell battery for the boat because the one I had didn't. seem to be performing too well, which the solar panel winter conditions didn't help, of course, but even so it just seemed to soon drain away, even though the voltage was, say 12.8 or so to start.

The specific gravity of the new battery was right at the top of the green. It's voltage was 12.8.

I took the old battery to my workshop and the specific gravity was low orange, 1.19. So I put it on charge and after about 14 hours it was to the top, and rested it was 12.8v and the specific gravity was still in the orange. Only a tiny movement to 1.21.

So whilst I could charge the battery up to a decent voltage, it's capacity to hold that charge had not been reversed by charging. I had even gone to the trouble of buying a DC power supply unit, so when I'd charged it to the top I hit it with 15.7v 3a for 3 hours to equalise it, but that didn't budge the low specific gravity.

So, the electrolite does permanently deplete gradually with use and time, even with good battery maintenance, and so the capacity becomes reduced. It is not all reversed by charging.

Merry Christmas.

[StuM]

The decreased SG is the result of sulphation. The sulphuric acid has lost its sulphur to crystalline lead sulphate and so the SG of the electrolyte decreases.

Equalisation helps if the main problem is stratification of the electrolyte (i.e. it has more concentrated sulphuric acid at the bottom of the battery than at the top) and can also help to a degree with crystaline lead sulphate coating the plates - but it won't help if the lead sulphate has left the plates and formed "sludge" at the bottom of the battery. Once that happens, the loss is irreversible.

[a64pilot]

While not recommending this, it used to be pretty common to drain a battery, place it upside down and flush out any mud you could with clean water, then refill with electrolyte and the battery would usually last a couple of more years.
However this "mud" is of course largely from the lead plates, so lead has been lost and your not recovering that.
It also almost certainly not an environmentally responsible practice, but I have done it a few times myself.
Also have found out the hard way that electrolyte used in aircraft batteries is a higher concentrate of acid than used in automotive batteries

[duggybuggy]

a64pilot

That is what I did. I wouldn't recommend it, too. I work with sulphuric acid so this made it easier. It may well extend the life, and I have done it just by way of experiment in order to gain a better understanding of battery use and maintenance. The batteries to buy are not too expensive for me to bother, but that said, the one I bought 18 months ago cost me £200 with free delivery; the new identical one from the same supplier has just cost me £255 plus £12.50 delivery. So projecting forwards at that rate, with income rise stagnant, I don't know where it will lead. I suppose this will be the same story for many people in all aspects of their life.

I am going to try and make the saving I need by more economical use of electricity where it is necessary, using more efficient appliances, and using non-electrical means where possible. And so if i have a good knowledge of what is going on with my battery then I will be able to use a smaller/less expensive battery and make the saving there.

I might have a look at wind power which of course would generate power at night which I could pretty much use without much drain on the battery.

I am also going to try and learn about other battery technologies, like lithium-ion and perhaps the newer flow batteries which apparently are going to cause a revolution in even domestic self=generating set ups, making this possible for all.

Its a very enjoyable subject. I like this forum to discuss these matters.

[ErikFinn]

I always thought flushing the bat was just a youtube urban legend.. Has anyone done that to Trojan deep cycle bats, such as the T105? My understanding is the Trojans have much more reserve space under the plates for the sludge to accumulate and thus the shorting would me more rare with Trojans.

[a64pilot]

The flushing was something I did years ago on farm tractor and backhoe, maybe a bulldozer battery, where worst case you just jumped the thing off, likely Interstate batteries which were good batteries.
I doubt it would return a deep cycle to decent service.