Lead acid... it's dead isn't it?

[Renate]

Decent solar controllers have an Equalise function that you would normally set to automatically run once per month.
RTFM to see if your controller has such a function and engage it.

That what I illustrated above.
Mine does it on the 28th of each month (so that February can get it).

[bdunham7]

It does have an equalising mode and I believe it's set to default.  I have seen it charging the battery to just over 15V but only rarely.
If I try this 16V 10Amp thing on a sealed battery, surely it's just going to force it to vent... assuming it has a suitable vent.

If you actually get it up to 16 volts with 10 amps the battery is probably not in good shape.  10 amps shouldn't make it vent forcefully, it might fume a tiny bit.  If you have an equalizing mode that can supply 10 amps and it has been running even occasionally, then you probably just have the wrong type of battery for this.

[paulca]

It does have an equalising mode and I believe it's set to default.  I have seen it charging the battery to just over 15V but only rarely.
If I try this 16V 10Amp thing on a sealed battery, surely it's just going to force it to vent... assuming it has a suitable vent.

If you actually get it up to 16 volts with 10 amps the battery is probably not in good shape.  10 amps shouldn't make it vent forcefully, it might fume a tiny bit.  If you have an equalizing mode that can supply 10 amps and it has been running even occasionally, then you probably just have the wrong type of battery for this.

The charge controller wont get anywhere near 10Amps, as it's only a 50W panel   I think 3.2Amps is the max at 14.40V

[paulca]

I hooked it up to my beefy PSU and at 16V it only took 4A which started to fall towards 3A immediately.  You think prolonged 16V will start the current rising again?

The battery has a condition sight glass and it's supposed to be green when fully charged and red if it needs replacing (is this a chemical SG measurement or something?), it shows "Black"... Recharge.

[Ian.M]

The indicator 'eye' is a fixed threshold hydrometer containing a colored ball of known density trapped in some sort of cage immersed in the electrolyte of a single cell.  If the S.G. is high enough the ball will float against the window and display its color clearly.  Three color indicators have some arrangement where the background color also changes due to a float moving or by reflection from the electrolyte surface if the electrolyte level is too low.  It only monitors one cell and only gives a crude go/no-go indication of the S.G. so is essentially useless except as an indicator that batteries in store stock need recharging! 

[bdunham7]

I hooked it up to my beefy PSU and at 16V it only took 4A which started to fall towards 3A immediately.  You think prolonged 16V will start the current rising again?

This is a 100AH car-sized battery, right?  Yes, if the battery isn't complete toast, the current will rise to 10 amps and then the voltage should start falling.  If it doesn't do that it's gonski.

Edit:  And do be careful!  If you have one cell venting or one section of the battery getting very hot compared to others, toss recycle it.

[paulca]

I hooked it up to my beefy PSU and at 16V it only took 4A which started to fall towards 3A immediately.  You think prolonged 16V will start the current rising again?

This is a 100AH car-sized battery, right?  Yes, if the battery isn't complete toast, the current will rise to 10 amps and then the voltage should start falling.  If it doesn't do that it's gonski.

Edit:  And do be careful!  If you have one cell venting or one section of the battery getting very hot compared to others, toss recycle it.

Yea 100Ah marine battery.  It's risen now to 4.2A but it's fluctates around 3.5-4.2A.  No heat that I can feel and no hot spots.  I can hear is fizzing gently though.

[tautech]

Sorry, to be clear, I was considering fully charged to be when the charge controller switches from boost, 14.40V to 13.60V float. 

Heres is the chart for 2 days.  The min value 12.11V occured when the 15W load was occuring.  The left side shows what I considered the battery getting somewhere close to fully charged.

Your battery needs a good boil.  It's probably sulfated and has an internal impedance that is now way too high--you're just getting a 'surface charge' on it.  If you have the means, connect it to a charger or power supply that can supply 10 amps and force it to take 10 amps up to a limit of about 16 volts.  If it won't take a full 10 amps, just leave it at 16 volts.  You should see the current ramp up to 10 amps (if it wasn't there already) then you'll see the voltage start to go down.  Or, you'll see just one cell start to boil, in which case you battery is likely done.   If that works, give it 10 amps for 16-20 hours starting from the time that it actually takes the 10 amps.  If this works, you won't be able to raise the battery voltage back up beyond 15 volts with a 10 amp charge.  You probably want to do this outside and not near flammable objects, sources of ignition or things that would be excessively bothered by acid fumes.

This ^
Decent solar controllers have an Equalise function that you would normally set to automatically run once per month.
RTFM to see if your controller has such a function and engage it.

It does have an equalising mode and I believe it's set to default.  I have seen it charging the battery to just over 15V but only rarely.

If I try this 16V 10Amp thing on a sealed battery, surely it's just going to force it to vent... assuming it has a suitable vent.

Of course they are vented but depending on the battery technology the vents may retain some small positive pressure in each cell to assist with retaining electrolyte.
An equalising charge is also known as a gassing charge amd when we used dumb LA battery chargers leaving them ON too long led to a gassing charge then we topped up the electrolyte something that's much more difficult with a low maintenance or SLA.

IME in periods of low battery activity keeping them fully charged is very important to maintain an acceptable service life and vehicles we have that might get little use over certain times of the year get a smart charger on them monthly at least overnight or until the Charged light comes on.

[bdunham7]

Yea 100Ah marine battery.  It's risen now to 4.2A but it's fluctates around 3.5-4.2A.  No heat that I can feel and no hot spots.  I can hear is fizzing gently though.

Keep cooking!

[paulca]

Yea 100Ah marine battery.  It's risen now to 4.2A but it's fluctates around 3.5-4.2A.  No heat that I can feel and no hot spots.  I can hear is fizzing gently though.

Keep cooking!

4.3A

I'll let it run a while longer, but I'm not leaving it overnight at 16V, not unattended.  So I'll cut it when I am off to bed.  I might drop it back down to 13.6V and leave it overnight then hook it back up to the panel.  Maybe it helped.

[bdunham7]

4.3A

I'll let it run a while longer, but I'm not leaving it overnight at 16V, not unattended.  So I'll cut it when I am off to bed.  I might drop it back down to 13.6V and leave it overnight then hook it back up to the panel.  Maybe it helped.

Don't reduce it, just stop until you can resume supervised cooking.  Definitely don't leave it unattended!  It doesn't look good, if C/10 or less gives you 16 volts.  But there's no point in not continuing the experiment tommorrow--nothing to lose at this point.

[paulca]

Well, so I turned it back on the next day and it took 6.5A for a few minutes, I left it for a few hours and it dropped to 3.2A.

I gave up and hooked it back up to the panel.

Seems to have had some effect.  It averaged 13.0V the first 24 hours and running the garage lights it only drops to 12.44V now.

[tautech]

Well, so I turned it back on the next day and it took 6.5A for a few minutes, I left it for a few hours and it dropped to 3.2A.

I gave up and hooked it back up to the panel.

Seems to have had some effect.  It averaged 13.0V the first 24 hours and running the garage lights it only drops to 12.44V now.

Good.
What this shows is LA likes some exercise so bump the battery back up to ~14.4V and drag it down a time or two more and you should get some more useful life from it.

[paulca]

Battery is doing ok, but as it's Spring and the panel is generating more than enough power...

Is it wise to bring the battery down low, maybe 10.8V at 1 amp and THEN give it the slap in the face charge at 10amps at 15V?

[tautech]

Cycling LA's is often beneficial like the occasional gassing charge just don't overdo it.

[paulca]

So nearly a year later, battery has been fine, but is showing "surface charge" issues again.

So this time, I drained it safely, first with the 3Amp garage lights, then with then 200mA USB outlet/voltmeter on the caravan electrical panel I use for distribution.  The low voltage cut out each time cutting it out at 11V.  It did not recover during the day, because when it rose above 12V the load got switched back on.

Confirming I had drained it enough, I let it settle for the evening and the voltage read 11.3V, turned the lights on and the low voltage cut in immedaitely.

Then... a "slap in the face" charge.  10 Amps@16V until the CC limiter started dropping voltage down to 15V, when I reset the CV voltage to 15V and left it overnight.

That should fizz it up a bit.

14 hours later it was happily sitting at 14.40V taking about 0.8A, <0.01C.

Put it back into service and we'll see if I can get another year out of it.

[paulca]

Battery torture evidence: