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neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210
Posted: 10:42pm 17 Apr 2012
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Not a silly question, I think!
I have a 100Ah deep cycle battery that was fully discharged some 4 years ago and it has been rejuvinated using a C-Teck 5.0 charger on several occasions over the last couple of months because it took days to get through the desulphation part of the program.
Now the charger brings it back from 11.91V to 13.19V in a couple of hours. Last charge was completed at 4:15 p.m. 2 days ago. Immediately after disconnecting the charger, my multi meter showed a drop to 13.10V in about 10 seconds, at the most.
Since then, it dropped to 12.2V at 8:00 a.m. yesterday and 11.91V at 8:00 a.m. today.
These voltages are taken with no load applied over the time span.
Questions.
1. As I simply plan to put the charger on a 24 hour timer (connection time(s) yet to be determined) and attach a 40x PicAxe chip to run a solar tracker controller 24/7, what can I expect from the battery in coming years?
2. I also plan to run an 18V portable drill directly wired to it (as elsewhere described on the Shed forum) for an estimated 30 minutes a day. Am I being too optimistic?
I have picked on this configuration to overcome grid power outages that might occur at inconvenient times.
Comments?Edited by neil0mac 2012-04-19
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 01:10pm 18 Apr 2012
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Have you got something, like a 100W car driving light? You want a load that draws around 10A from your 100Ah battery. Lights are easy for that test as the results are visible. You need to connect an Amp meter with other resistive loads and observe that.
Charge your battery to the 13V you got above.
Disconnect it from the charger and immediately connect your driving light load.
If it stays brightly lit for 10 min or more your battery is reasonably good.
But I suspect the light will be visible dimming in seconds as you watch, indicating the battery truly has had it.
Batteries do not last forever , perhaps time to look for for a better candidate to rescue.Klaus
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 11:42pm 19 Apr 2012
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13.2 volts is nowhere near enough to charge a lead acid battery, it will have very little charge, no matter how long you leave the charger on it.
Something like 13.8 volts would be a practical minimum charging voltage, with closer to 14.2 volts being more realistic for fast charging.Cheers, Tony.
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 02:00am 20 Apr 2012
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Hi NeilOmac,
I believe we have been over this before, probably worth a recap.
The 13.2 V is just residual surface charge on the plates, it means nothing as far as judging battery condition. Most battery manufacturers recommend leaving the battery disconnected for 3 hours before checking the voltage after charging or discharging to get a better accuracy on voltage readings.
Using a charger with a built in desulphator will work on mild sulphation, heavy sulphation requires a different technique due to the very high resistance.
A good battery will sit at 12.5-12.6 volts for more than a month, provided it is clean and properly charged.
11.91 volts is very low, the question is why.
the charging/desulphation process may have loosened a lot of hard stuff up that is continuing the process while the battery is sitting and using the battery's energy while this is happening, you can leave the charger on trickle charge for an extended period, week or more and see if it gets better.
OR there could be faulty cells with damaged plates that are not working and not taking a charge.In which case the battery is toast. Faulty cells are very hard to pick if they are in a bank of paralleled batteries, they will eventually destroy the good batteries.
Longterm? I would say you haven't charged the battery enough yet to rule out heavy sulphate, it needs to charge 24/7 for a minimum 3 weeks preferably with other batteries connected as well.
If you are lucky you will get half its capacity back, that would be 200 - 300 watts to use between charges. It will be harder and slower to charge up than a fresh one, old deep cycle batteries eventually get to the point where its not economic to keep charging them as the power you get back gets less and less, its pretty rare that they die all of a sudden like car batteries do.
yahoo
I'm confused, no wait... maybe I'm not...
neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210
Posted: 03:33am 20 Apr 2012
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We may have briefly discussed it before - but the approach I am using is a bit different.
My primary motivation is to get it to the stage where I can run a microprocessor (40X Picaxe) in day light hours, so a 5W draw for 10 - 14 hours a day 24/7. I don't care if I have to charge it (or leave it on float, even!) during that time of use as what I am getting back is KWHs a day from the solar tracker that it will drive, i.e. COST is NOT an issue.
The reason for this concept is to eliminate the occasional black (or brown) out, or grid failures - like up to 10 days. In that case I am prepared to run my small petrol generator for charging purposes.
Depending on what state it can be restored to, it MAY be called on to run some electronics during storms, or prolonged blackouts.
Question. What is the effect/advantage of having it charging with other batteries? (I do have one which is also of doubtful electrical value. Probably can lay my hands on one that is in somewhat better condition, if absolutely necessary.)
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 01:43pm 20 Apr 2012
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the reason is pretty simple, despite all the hype a modern charger has 2 basic stages
stage 1. voltage restricted to about 14.8 volts (charging)
stage 2. voltage restricted to about 13.8 volts (float)
this can vary a small amount depending how the charger is set, what type of battery it is charging etc.etc.etc.
The point is, that the trigger for the charger to switch from charge to float is the amps going in to the battery. it is generally set between 1 - 2% of the amp rating of the sized battery that it is designed to charge. If the battery and charger are matched in size then as the battery gets past 95% charge, resistance to charging builds up in the battery and progressively less amps are pumped in at 14.8 volts.
Using your charger as an example it will charge at 14.8 volts until the amps that the battery is taking gets to 1.5 amps then it switches to float, it will switch from float back to charge at 1 amp. ( this is just a guess at the numbers but you get the idea). 13.8 volts (float) is designed to maintain a battery, it takes an eternity to charge a battery at this voltage (1000+ hours?)
A 100 amp-hour battery that is heavily sulphated has a lot of resistance to charging due to the plates being gummed up, so when your charger gets to the 1.5 amp cutoff point, it may only be charged to 10% of its capacity, when it switches to float and starts the pulsing desulphation. A normal battery will stay on the desulphate cycle for a bit then accept more amps and switch back to charge and repeat the process.
The best way to get around this is hook a few batteries together, if each battery accepts half an amp and there is three batteries, this will keep the charger in the charge stage for longer, giving the sulphate a better chance to dissolve.
The alternative is to use a very small charger with a lower cutoff amp point on the 100 Ah battery, this does not work as well because a single battery can get stubborn and not take a charge for days at a time then all of a sudden come good, if it is on the float stage it will never get to this point. Having the others hooked up gets around this.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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, perhaps time to look for for a better candidate to rescue.