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Energy/Electricity Storage and Use/Grid Connection => Off-Grid, Batteries & Inverters => Topic started by: knighty on December 15, 2014, 03:57:02 PM



Title: identify battery fault - white scale on top of water ?
Post by: knighty on December 15, 2014, 03:57:02 PM
hi

I've got a battery which came on my camper van, then I used it on my generator... now it's dead

checked it with a battery tester, from fully charged as soon as you pull power from it (100amps for tester) voltages drops to 1 or 2v

I've topped it up, EQ charged it, and left a desulphator and a trickly charger connected to it for about a month....

now the scale from ontop of the water has cleared, but the plates inside that cell are white

all the other cells look good, nice clear water, plates and nice and clear/straight etc. etc.

anyone have any idea what the white stuff is / could be ?

also, that cell hardly bubbles... on charge/desulphator connected if I knock/rock the battery the other cells bubble loads... but there's non (or maybe a little few) from that cell


I'm more interested for interests sake, than trying to rescue it (I'm guessing it's dead now anyway)

photos...
http://imgur.com/a/JoPhn


Title: Re: identify battery fault - white scale on top of water ?
Post by: marcus on December 15, 2014, 04:55:32 PM
white scale on the plates I would take to be heavy sulphation. If it's just one cell I guess it's a shorted cell - have you measured the open circuit voltage? I'm guessing it'll be ~10.something volts.

don't know about floating scale on the top, but would guess if it's heavily sulphated then some sulphate would fall off where the metal rises out of the electrolyte to the cell interconnection bar - although it generally sinks to the bottom of the cell.

And as you suspect, I'd say it's not recoverable.


Title: Re: identify battery fault - white scale on top of water ?
Post by: knighty on December 15, 2014, 06:46:23 PM
that's the puzzling thing... it's sitting there quite happy on 12.5 (ish) volts

put it on a car and it runs everything fine, untill you try to start it, when it dies


the battery tester pulls @100amps, when I test the battery the voltage drops from 12.5v ish to 2v ish



I topped it up and bit, and now the scale floating ontop has gone :-o


Title: Re: identify battery fault - white scale on top of water ?
Post by: marcus on December 15, 2014, 08:34:43 PM
OK, that is a bit weird. Although, is that the voltage after resting for a couple of days or only briefly after charging?

I'd still say that cell is sulphated (the white deposits).

The other thing might be:- if the +ve plates have broken off from the interconnecting bar/terminal of that cell, then the only part of the cell that's still in circuit is a small part of the bar touching top of the electrolyte. That would account for the lack of Amps and 12.5v under light load; and if the actual plates have been out of circuit for a while they may well have sulphated.

I'm only speculating this as I've been looking into the modes of failure for 'cheap car batteries' (not to cast aspersions on your battery) as I've been considering buying some as a buffer battery for my off-grid hydro system, and I've been warned by more than one source that 'cheap' car batteries can fail prematurely where the +ve plates (or grids, as they are in car batteries) attach to the +ve terminal.


Title: Re: identify battery fault - white scale on top of water ?
Post by: Philip R on December 15, 2014, 11:32:51 PM
Knighty,
Marcus is correct, the battery has sulphated up and is kaput.

Some car batteries have the grid made up of a cast lead alloy grid, Some originating from the US have a serated lead alloy sheet, which is stretched out to resemble a chicken wire structure. The active paste pressed into the plate matrix.

The jointing of the pillar to group bar, to plate(s) is important. Failure of any one of these joints will lead to degradation of the cells/battery or complete failure.

Charging the battery with high ripple content DC may well de-sulphate a battery, it also knocks the active material stuffing out of the plates, thus knackering the cells.

Philip R


Title: Re: identify battery fault - white scale on top of water ?
Post by: knighty on December 16, 2014, 12:31:29 AM
I'll add it to the scrap pile then

I seam to have accumulated about half a dozen old batteries, and I'm not sure which ones are any good or not

I'm a strong believer in having a good battery on a car/van... always buy a decent make, and the biggest / highest output one which will fit (sometimes mod the battery tray to fit a bigger battery)


but.... I need a couple of batteries in the back of my camper to re-charge my electric bike from... so figure a few older/weak batteries would be fine as long as they hold charge for a while


Title: Re: identify battery fault - white scale on top of water ?
Post by: biff on December 16, 2014, 10:07:21 AM
Hello Knighty,
              Perhaps you could try a little acid (no8) in each of its 6 cells, say  about 2ms in each .You need to take out the existing fluid down top almost the top of the cells,just leave about 5mm depth above the plates.Move the battery about a bit but keep it level,shake gently for a few minutes . Don,t bother putting the charger or voltmeter on it for about 48 hours because it will be going mad inside,however after 48 hours it will stabilise and settle down. Just make sure to put in the exact amount of acid in each cell.
 An 80 watt solar pv panel (17.5v0) is great for taking them off the bottom up to where the ordinary charger can take over. It will not cost you very much apart from a few pence for the acid and you never know by the time you add a little distl-water It could start behaving properly. It,s worth a try.
                                                                             Biff


Title: Re: identify battery fault - white scale on top of water ?
Post by: knighty on December 16, 2014, 06:12:32 PM
snapped another photo today now the scum has cleared and you can see the plates

(http://i.imgur.com/elhcMUD.jpg)


I've taken it off the charger / desuplphator and I'll let it sit for a week


I'm more interested in trying to fix it to see if I can than anything else... always reading about desuplphators / other tricks.. and never really trusted them


I'll let it sit for a week, check the voltage... and then I think I've got an SG meter somewhere.... could be time for a bit of acid


Title: Re: identify battery fault - white scale on top of water ?
Post by: Tiff on December 16, 2014, 07:08:11 PM
What voltage did it get up to on the trickle charge? I would try getting it up to around 15v. I use a B6 charger which is useful as you can control amps and voltage over a wide range.


Title: Re: identify battery fault - white scale on top of water ?
Post by: Tiff on December 16, 2014, 07:16:38 PM
Also,  if you have a collection of old batts you can parallel them into a bank (using diodes) that may then have enough capacity to be of some use.


Title: Re: identify battery fault - white scale on top of water ?
Post by: knighty on December 16, 2014, 07:18:38 PM
smart charger took them to 14 and a bit volts

I've got a B6 charger, I'll give it a try
(I think it's a B6, does lipo etc..?)

should have taken a photo of the other cells to show the difference... the rest all look totally different to that one, they're all brown not white


Title: Re: identify battery fault - white scale on top of water ?
Post by: rogeriko on December 16, 2014, 08:00:24 PM
In a healthy battery the plates should be alternating grey and brown. This is a picture of my 18 year old battery that I used to use when I was off grid. It worked just fine.  The brown plate has a cloth wrapping but you can just see the colour of the plates at the top.


Title: Re: identify battery fault - white scale on top of water ?
Post by: Tiff on December 16, 2014, 08:29:08 PM
smart charger took them to 14 and a bit volts

I've got a B6 charger, I'll give it a try
(I think it's a B6, does lipo etc..?)

should have taken a photo of the other cells to show the difference... the rest all look totally different to that one, they're all brown not white

Sounds like you have the same or similiar charger to my one, for a 12v PB batt my one goes up to 14.7v for a full charge IIRC with the amps adjustable from 0.1A up tp 6A. I would definately try to at least  14.8v if you can, but with low amps. The tricky bit is knowing if there is crud in the bottom causing a short in that cell. I've tried flushing a battery out in the past - never again! A whole load of hassle, toxic waste which then has to be disposed of and of all of the risks of pouring and handling acid.

I've got a desulfator as well BTW, although I've not had any success with it - I've tried it on quite a few old car batts but its never made any difference (each time I tested the capacity). Maybe they work better on deep cycle batteries but I've never tried.


Title: Re: identify battery fault - white scale on top of water ?
Post by: rogeriko on December 16, 2014, 09:21:29 PM
I had a whole set of 12 of those large 1000Ah batteries with the clear cases. They were full of crud at the bottom all the way up to the plates, so they were not working very well at all. Because of the value and the fact they were only 5 years old I decided to clean them out. I found an old bathtub and built a platform (pallet) above then I drilled a 1cm hole  in each section at the base.  Below the plates there were 5 plastic sections about 5cm high that I guess helped to support the plates and catch the crud.  When all the acid had come out I poured rainwater in the top and shook the battery (50Kg) until all the crud had come out. Then I filled the hole with 2 part epoxy refilled the battery with distilled water and charged them gently for 1 week. Then I emptied out the water and added concentrated acid until it was the required strength and put it back in the battery. You have to empty the battery and add the acid outside the battery because it gets hot.  The result was batteries almost as good as new, If anyone has newish batteries that have lost a lot of powder and shorted at the bottom, from heavy use I believe, I can give you more info but its definately worth doing. I didn't take any pictures of this operation but I hope it makes sense.


Title: Re: identify battery fault - white scale on top of water ?
Post by: Tiff on December 17, 2014, 08:14:52 AM
Certainly makes sense to flush out expensive and large deep cycle batteries, I did it with an old car battery - chances of sucess were slim but I wanted to give it a go just to find out.

I wonder if a long, thin flexible tube would get to the bottom so that the crud, or at least  some of it could be suctioned out?