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

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bdunham7:

--- Quote from: paulca on February 25, 2021, 04:49:02 pm ---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?

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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:

--- Quote from: bdunham7 on February 25, 2021, 05:14:55 pm ---
--- Quote from: paulca on February 25, 2021, 04:49:02 pm ---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?

--- End quote ---

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.

--- End quote ---

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:

--- Quote from: paulca on February 25, 2021, 10:56:26 am ---
--- Quote from: tautech on February 24, 2021, 11:55:11 pm ---
--- Quote from: bdunham7 on February 24, 2021, 11:35:24 pm ---
--- Quote from: paulca on February 24, 2021, 01:13:17 pm ---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.

--- End quote ---

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.

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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.

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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.

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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:

--- Quote from: paulca on February 25, 2021, 05:38:45 pm ---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.

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Keep cooking!

paulca:

--- Quote from: bdunham7 on February 25, 2021, 06:51:12 pm ---
--- Quote from: paulca on February 25, 2021, 05:38:45 pm ---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.

--- End quote ---

Keep cooking!

--- End quote ---

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.

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