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Forum Index : Solar : How to Equalize?
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wallablack Senior Member  Joined: 10/08/2011 Location: AustraliaPosts: 164 |
Hi All, I picked up a second hand lead acid battery bank (6 x 2V @ 800ah,25hr rate) not long ago. Although it hold charge "semi-well" I wish to Equalize the battery bank.....but I just can't get her there...gets to 15V MAX. I have given it a good deep charge with a 40A 12V Charger to 14.4V and then let the solar array to try to do the rest as this is where the AC Charger stops...AC Charger & Solar Array still connected. At this stage the array consists of 4 x 120W 12V and 2 x 200W 12V controlled by a PL20. Open Voltage shows 20.6V. Even when I put the PL20 into EQUL (Equalize) mode it has never gone past say 15V. (EQUL setting on the PL20 is set to 16V for 1 hour. In a previous post it was suggested to direct connect the solar array to the batteries and adjust the input by shading the panels with a sheet of cardboard. Even in the peak of day when I do this she won't go past 15V... Any suggestions? Foolproof systems do not take into account the ingenuity of fools. |
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Madness Guru  Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Check the voltages across each cell, also use a hydrometer. Most likely one or more cells is not taking charge. Search around on this site for desulphation which is to get rid of the hard build up of crystals on the plates. Also you should find out the correct equalization setting for your batteries. I am using Trojans and they say 15.5 volts for equalize. If there is a problem with the batteries just trying to hammer them will not do them any good, check if they are getting too warm during charge. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
If they are old with enough defects on the plates you may be gassing the energy off. This is where a clamp meter and a couple of DMM's make all the difference you can see exactly where the energy flow is. I have wasted a lot of time guessing what is going on. I still look after an old bank that has almost had it, its upper limit is about 15.3V. I just charge it with a 15V power supply with the adjustment screw wound up (hooked to a generator) if it needs it in winter other than that I let the monthly EQ @15.2V do it and keep an eye on the water. for the first summer I was involved, we run the generator every second Monday morning and manually trigger the EQ to make sure it completed a cycle but the system was a bit underdone on panels at that stage. Took 18 months for the batteries to settle down properly. PS sometimes the standard charge cycle voltage is a tiny bit low for charging crook batteries should be more like 14.7 V I think. SG readings can be all over the shop with sulphated batteries (they can look charged when they are not) I'm confused, no wait... maybe I'm not... |
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| wallablack Senior Member Joined: 10/08/2011 Location: AustraliaPosts: 164 |
They are typically each reading 2.4V during charge (no load) and after the charger has been disconnected and all of the links disconnected and the batteries let to rest for 2 days they are still showing 2.2V. I have had a desulfator on them for a while now, say 1 week.... I am getting my battery temperature form the centre of the battery bank where the temp. sensor is held against the battery with neoprene, assuming this would be the warmest spot on the battery bank (although the battery recieving the pos solar input seems slightly warmer. The battery temp seems to be not much higher, say 5 degrees, higher than ambient temp but never over that. Foolproof systems do not take into account the ingenuity of fools. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Desulphating takes time, have read checked the SG? If you don't have a hydrometer you can get them for under $20 at auto parts shops. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Sounds to me the batteries are a bit shagged, and you are expecting them to react as new cells would. Like Yahoo said, older cells dont take charge like newer cells, and their max charge voltage will be lower, so you are likely just boiling the water out of the cells once the voltage reaches a max limit for the aged battery. Its not a healthy sign for a good battery bank that you report, and a desulphator can work, but 8 out of 10 times it might not, flogged out batteries are just that........flogged out!!!!, but neglected batteries are often sulphated so there is a chance of rescue to them, but not always. Pete Sometimes it just works |
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| wallablack Senior Member Joined: 10/08/2011 Location: AustraliaPosts: 164 |
Understanding now that they won't charge as high as new batteries, which I never knew, maybe I am expecting a bit much from them. They are reading pretty good SG and I do know their history from a good friend who removed them. They were basically like many battery banks, they were on float for most of their life, but that means little really at the end of the day, still doesn't make them "near new" or anything. With a load of 2 x 100W flood lights and 1 x 250W flood light they seem to drop from 13V to 12.2V and just sit at 12.2V for ages... The only real load testing I have done is our 100W pump and a 36W flouro. Off charge they went from 12.5V to 12.2V in 14 hours with the both running constantly. I think I need to remember, I am just polishing a turd with these... Foolproof systems do not take into account the ingenuity of fools. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
In theory if they are brand new you should be able to get 9.6 KWH. (6 x 2V @ 800ah,25hr rate) Your pump and light test 136 watt X 14 hours = 1.904 KWH which is probably about what you should take out of them in a day. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
EQ is not charging its deliberately gassing the batteries hard to stop them stagnating or layering acid and a few other things. You are supposed to raise the voltage to push them well past the point of resistance, if they are all bubbling evenly and losing the same amount of water that is as good as you can do. Obviously a bent plate or rubbish between the plates or damaged plate wrap ETC is going to cause a low resistance point where gassing will happen sooner and EQ is not as effective (the heavy layers take some shifting). the point between charging and gassing is not clear nor is it the same all the time. The only true indicator of a battery having accepted all the electricity that it can at that point is the amps have stopped dropping. Example if you were charging to 14.4 and checking every 15 minutes and the amps got to 5.4 amps and no lower then the battery is full or the charging voltage is too low. increase it to 14.8 and the amps sit at 7.8 and don't drop any further then they were full as they were going to get. Sulphated battery might still be dropping a 3 amps or be gassing at 11 amps. Most chargers switch to float on a time base or at a set amps, how that is matching the batteries charge needs at this point I have no idea, not enough info. I'm confused, no wait... maybe I'm not... |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Wallablack The desulphation does take time as I have had some on for over a month to get them going but never expect to make them new again just usable as yours seem to be from your comments. A little trick I learned, is to use a generator to charge as the spikes of mechanical rectification help to desulphate better than the soft DC produced by rectification, I noted that the back up batteries on many units I serviced only lasted half as long with rectified AC chargers compared to the old generator charged batteries. Also remember that while batteries are at so may amp hours it is wise to only discharge to no more than 60% of capacity on deep cycle and less than 50% on automotive and marine batteries and that is over a ten hour time frame. In practical terms I find that a battery bank is only good for 50% of it's so called rated Amp Hours. The exception to this is Lipo and Nife cells which will go over 90% without damage. All the best Bob Foolin Around |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
On the desulphator subject, I chipped in that I was using a little unit (555, mosfet and small inductors). I had a 12v deep cycle battery that was flat for about 3 months. The SG was virtually water and 3 weeks on a normal charger did nothing. I was sceptical about these desulphators but after 3 weeks running the little unit, all the SGs came up to around 1265 and the battery cranks over my old Fiat 615 tractor (hungry on CCA) with no difficulty or sign of losing power. I'm still not convinced but not as sceptical now. Does anyone know the chemistry associated with using short high voltage spikes to reverse the sulphation process? I'm sure it is more than just "chipping" off the crystals. Web search found only opinions. David M. |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Mobi I did look into it a few years ago and the general gist of desulphation was that the sulphate crystals have a resonant frequency as all crystals do and exciting them at that frequency agitates them and causes them to break down, from memory it was around 20K hertz. Some designers put a sweep frequency between 15K and 30K HTZ and that seems to wok The origional one I had was a bit of a heath robinson machine with valves and it worked very well on 32 volt batteries as it was designed to. You could hear a high frequency buzz when it was working around the top end of audibility. I used it to revive many 12 volt batteries as well. All the best Bob Foolin Around |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I have a couple small desulphators and in the process building one of these , also lots of information about the process on the same site. I have had some reasonable results in recovering golf cart batteries with these. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
The trick with a sulphated battery is wire two or more batteries together and use a small charger so it doesn't go straight to float. I find that effective. two N70Z-ed's and a 2 amp charger is OK. A 7 amp charger will not stay on. the chemistry involved in breaking down the solids will depend on what various structures the crystals have grown as, there are a lot of combinations possible and some are not easily reversible. I have found some have a hard skin and it takes a while to eat through that skin to get to the soft stuff underneath 4 or 5 cells will have eaten back patches and have started to dissolve and 1 or 2 will just not budge, and just sit there gassing from the terminal connection bus bars for a month. I'm confused, no wait... maybe I'm not... |
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| wallablack Senior Member Joined: 10/08/2011 Location: AustraliaPosts: 164 |
WOW....thanks for all of the information guys...greatly appreciated. I never expected to turn them into knew batteries but my understanding of equalizing was to get all of the batteries to "act" (probably not the word I'm looking for) the same as one another. When I first put them all together just before the new year I noticed on full charge some seem more active (bubbling) than the rest. I had a good look at them yesterday during peak sun they all seem to be the same. I was also a bit skeptical about desulphators but after breaking down an old forklift battery bank (forum link) I did visually see a change and physically the batteries were better off after it, but with so many variables could have affected that change (different charge controller etc) so I wasn't sure. I have had these ones on the desulphator for a bit now. With these batteries having a clear outer case it makes a nice change to actually see deep inside to see what is happening etc. I understand desulphating acts deeper than I can see. I tested the fridge (300lt...ish) on it yesterday while it was on (solar) charge and I was quite happy. With 4 kids opening and closing the door all day and the fact the fridge is working harder as it is outside I thought it would have chewed the power up pretty quickly. At 9am yesterday with the bank at 12.4V I kicked her in the guts. The fridge drew a big 825 watts for about 30s and then ran it all day and night. At 7am this morning(now) I am still showing 12.3V. Foolproof systems do not take into account the ingenuity of fools. |
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isaiah Guru Joined: 25/12/2009 Location: United StatesPosts: 303 |
Pick up a Variac or variable inductor and you should be able to bring that voltage up over 15v,go slow and careful. What you actually be doing is raising the incoming voltage to the charger. Here in the states we use 125 volt normal and we had the variac up to 137 volts. You'll have to use one of the old dumb chargers to do this. Watch the heat on the charger and battery both. Isaiah URL=http://www.motherearthnews.com/Renewable-Energy/1973-11- 01/The-Plowboy-Interview.aspx>The Plowboy Interview[/URL> |
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