Just dug an old chair out

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Re: Just dug an old chair out

Postby Burgerman » 22 Jan 2019, 19:06

So chair starts to panic when batteries are about 11.7v

Some 11.5, some 12.
Batt volts though, depends on history before that point. Not state of charge.

But lets say 11.75.
If I just climbed a ramp or short steep hill with a 75 percent full battery that may be 11.75V.
If I drove in straight lines on flat ground,stopped to talk to someone that may be when its done 20 miles and about to stop for good.

So you cant know.
E.G while trying to start your car, when cranking, the battery can be 9V or less. It then is still 99% full. If you wait an hour some of that energy and voltage comes back. If you wait a day almost all of it does.
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Re: Just dug an old chair out

Postby Burgerman » 22 Jan 2019, 20:06

We took out 121Ah. Total discharge 101%.

Charge at 40A and so far we put back 133Ah in 4 hours, and still charging at the same low rate as a mobility charger begins! With an 8A mobility charger that means we would have taken 17 hours to get this far!
Attachments
132.gif
AMPS!
133.gif
VOLTS!
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Re: Just dug an old chair out

Postby Burgerman » 23 Jan 2019, 01:39

DONE.
Took just over 9.5 hours to 1000thC from 100% discharged.

Remember odyssey batteries charge much faster than other batteries due to lower impedance. And these two were charged at 40A thats 5 times the power of a mobility charger, and through heavy cables and Anderson connectors.

Not a lot of chance of charging a gel at 8A with a mobility charger via XLR is there? :clap

FROM 0Ah to 60Ah returned per battery, so x2. So total 120Ah charge returned.
Actual Ah taken to do that is nearly 137. That wasted additional 17 is due to leads inefficiency.

Here we see charger CURRENT at 40A putting the BULK (CC stage) back then gradually falling as the battery gradually sucks up less and less Amps. Eventually it falls to 1000thC or 1000th of the battery capacity. So 130mA.

CC-CHARGE.gif



Here we see the BATTERY VOLTS first the climbing part of the graph, while it is fed 40A (ABOVE!) and the battery volts increase as far as CV stage of 14.7V. And thats exactly where the charger holds the battery until its 100% full... Charge ended when Amps fell to just 130mA.

CV-CHARGE.gif
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Re: Just dug an old chair out

Postby Gnomatic » 22 Feb 2019, 00:02

I have a set of Deka 8G24 gel batteries that I pulled out of an old chair. They are DEAD. Checked with my multimeter they are both measuring 1V or so. I assume these are beyond saving and plan on recycling them.
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Re: Just dug an old chair out

Postby Burgerman » 22 Feb 2019, 00:38

Set your shirley power supply to 17V or higher as needed, even 30V, to try and get a charge rate of around 0.5A - set that as max current and connect. If they eventually start to charge (desulfate) the voltage will fall because resitance will drop. Limited in charge rate by that .5A. If they begin to climb and get above 14.5V then reduce volts to 14.1, and set .3A and give them a few more days. If that current falls to almost nothing then they are as charged as can be.

Then test Ah with the PL8 at the 10 or 20 hour rate. Then charge at 14.1V for about 2 days. And test capacity again. If its not improved, throw them away. If it has, then keep discharging and overcharging for a few cycles.
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Re: Just dug an old chair out

Postby Gnomatic » 22 Feb 2019, 02:26

So, start off with shirley PSU in PSU mode(not three stage), set to 17v, and 0.5A limit. Connected to both batteries in parallel, correct?
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Re: Just dug an old chair out

Postby Burgerman » 22 Feb 2019, 11:33

In parallel then 1A.
Set voltage to whatever it takes to get it to start charging, and the 1A limit will make it safe. As soon as it begins taking a charge (if it does) then the voltage will drop. As the resistance will drop... The problem is that sufates dont conduct. Or conduct badly. So you need to wack up the volts. To get any apreciable current to charge/reverse sulfation. But once it starts to charge properly, and then starts to climb to above 15V then you need to reduce the current. You need the high volts to get a .5A charge... It may need 30 or more volts initially for it to do anything depending on how long they have been dead...

That 15V on charge will not happen for at least 70Ah in. And so the .5A per battery means a long wait. 140 hours or longer.

At that point you can watch until it starts to climb above about 15V.
Then set to 14.1V and turn up amps to max if you want. And wait a long time.
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Re: Just dug an old chair out

Postby Gnomatic » 22 Feb 2019, 20:39

I started with one battery. PSU set to 17v and .5A. After a few minutes, the voltage has fallen to 13.4v, while maintaining .5A current. Is this a good sign?

First time I've tried something like this.
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Re: Just dug an old chair out

Postby Burgerman » 22 Feb 2019, 22:47

Yes keep going... If its any good its volts will drop lower as resistance falls. Once it starts accepting a charge its voltage will begin to rise again. Once above 12V, which may take days, set it to say 20A and 14.1V and just leave it for 2 days, until amps fall to zero or close to it. If amps begin to rise again, while at 14.1V then it is in thermal runaway. So you may need to limit current to .5A again.

Dont get too exitedthough it may be junk...
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Re: Just dug an old chair out

Postby Gnomatic » 22 Feb 2019, 23:32

Nothing to lose. And this process is new to me so its interesting. Plus I now have another use for my shirley PSU.

Voltage has now fallen to just below 12V. I take it I should expect the voltage to continue to slowly fall for a good bit.(days?) How low do you think the voltage will fall before it starts to rise?
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Re: Just dug an old chair out

Postby Burgerman » 23 Feb 2019, 00:02

Nobody can know. It all depends on how damaged that battery is.

Heres whats happening. You allowed it to fully discharge. That means all the sulfuric acid in the electrolyte turned to lead sulfate which coated not only the surface of the plates, but deep inside the spongy lead inside the grids. The problem is that this also causes the lead spongy stuff to expand. This pushes it apart, and distorts the plates, and the spongy lead active material is crumbly...

It doesent do this in use as you are not discharging fully most of the time, and you only discharge to about 11V at 100% done. And you dont leave it weeks before charging. But the longer its left, the more of this lead sulfate turns into larger crystals, which dont conduct and which grow in volume. So we dont know how much damage is done. As we start to charge, resistance is super high. No current flows or very little, because the big crystals dont conduct. And because the electrolyte is just about all water (and silica gel crystals in this case) which doesent conduct well. Hence the higher voltage needed to get it to start to charge.

Charge means: convert the lead sulfate back into sulfuric acid. That means that the electrolyte now has some acid back. That means its now lower resistance. That then means it can now have some amps go through it without needing higher voltages. The problem is we dont know how much of the sulfate is ultra fine easily reversed powder, or large permanant non conductive crystals. And we dont know how distorted the plates are. And we dont know how much of the spongy lead active material in the grids has been broken up or expanded so that it doesent conduct...

So now you know whats going on! You are returning the lead sulfate to the acid making the ectrolyte more conductive, and making the plates clean.
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Re: Just dug an old chair out

Postby Gnomatic » 23 Feb 2019, 04:21

That's informative.

I set the voltage at 14.1v for overnight and kept the current limited to 0.5A. Battery continues to hover around 11.95v, drawing its max allowed 0.5A.
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Re: Just dug an old chair out

Postby Gnomatic » 23 Feb 2019, 17:49

This morning the battery had climbed just a little, to 12.05V still drawing 0.5A. So I set the amp limit to 20A just to see what would happen. The volts jumped up to the 14.1V limit, but the amps never go close to 20. Current reached 6A and would climb no further.

I turned the amps back down in the meantime.
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Re: Just dug an old chair out

Postby Burgerman » 23 Feb 2019, 18:17

No leave it. Set amps to max. You only need limit amps if

a) you are leaving it a long while and you are not there.
b) if charge voltage is set to 17 or 70V so that it just feeds a safe .5A indefinitely to sulfate.
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Re: Just dug an old chair out

Postby Gnomatic » 24 Feb 2019, 20:58

The current has fallen to about 1.6A. Should I now cap the current to say 2A in case it stops falling and starts rising again?
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Re: Just dug an old chair out

Postby shirley_hkg » 25 Feb 2019, 00:39

Would it be faster to do it in a 45℃ water trough ?
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Re: Just dug an old chair out

Postby Burgerman » 25 Feb 2019, 01:57

Yes. Cap at 2A and set 14.1V and give it some days until it falls to almost zero.
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Re: Just dug an old chair out

Postby Gnomatic » 26 Feb 2019, 17:23

Current is falling slowly, down to .36A. Keep going?
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Re: Just dug an old chair out

Postby Burgerman » 26 Feb 2019, 18:16

Till its under .1 or less. 1000THC would be 0.01A. Just leave it. As long as current doesent rise again. But it will take forever. So:

If you have the patience, you can set current to .2A and volts to high. And do a controlled overcharge to desulfate further for a day instead. That will force a few Ah extra in but do so slow enough at that low current that the recombination can cope. Ignore volts. The voltage will fall initially when you do that. And eventually slowly climb. If it gets to 15V or a little more stop. Or reduce to .1A. Then test Ah with the PL8. And hopefully it will not be too dissapointing!
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Re: Just dug an old chair out

Postby Gnomatic » 26 Feb 2019, 18:40

I will leave as is. It's going to take quite a while for the current to fall below .1A at this rate
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Re: Just dug an old chair out

Postby Burgerman » 26 Feb 2019, 19:43

Yes thats why you set a fixed Amp rate to keep it charging after it drops below the 200mA.
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Re: Just dug an old chair out

Postby Gnomatic » 28 Feb 2019, 17:54

48hrs later, the current has continued to fall, although only to 250mA last I checked. You weren't kidding about this taking forever .....
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Re: Just dug an old chair out

Postby Burgerman » 28 Feb 2019, 20:54

Thats because the natural result of discharging is sulfation. Its really only reversable fully if its JUST been discharged. As you FULLY recharge. It is reversed and all the sulfates are returned to the electrolyte as sulfuric acid leaving the plates clear of the stuff. This is why a FULL recharge is always essential and why the typical mobility charger that gives a green after 4 hours is a joke.

But if you leave it discharged in any way, for a few hours, some small of it turns into permanant sulfation. Why permanant? It turns with heat, and time into larger crystals. Which doesent conduct electricity. Or conducts it very very badly. So it is for good. 10,000v wont convert it back. What you are doing is a current controlled overcharge, to keep removing every bit of the sulfates that can still be reversed in any way. So yes it will not be fast! You are doing the almost impossible. But if current still falling, its still happening. Wether its going to result in a usable battery is debatable!
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