Think I've overfilled my VRLAs

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badnewswade
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Think I've overfilled my VRLAs

Postby badnewswade » Tue Mar 08, 2011 11:31 pm

I've finally found the manual for my Noblifts (no cracks please!) and it says that they can indeed be refilled, generally as part of an equalisation charge (which I've sort-of done, didn't overcharge by much though).

However it also mentions an "acid sucker", "pregnant solution state" and "lean liquor state". There's a copy of it online as well which I've found - the English is REALLY bad:

http://store.oohla.com/storefiles/termi ... /es-44.pdf

I think the gist of it is that it's fine to refill it as long as you let the sponge / mat thing soak up the water and don't keep pouring it in until it floats on top. Which is basically what I've done.

Should I just wait a couple of days then draw out the excess water with a pipette?
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Jeremy
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Re: Think I've overfilled my VRLAs

Postby Jeremy » Wed Mar 09, 2011 7:53 am

You're right, that manual is a laugh a minute!

I would leave them as they are and not try to remove any electrolyte. The excess water will gradually vent out as gas and return the electrolyte to the correct strength. If you remove some electrolyte then the battery will always be running with electrolyte of a weaker strength, as you will be removing water and acid, not just water.

I would hazard a guess that the cells will sort themselves out after a while. You may notice poorer performance, particularly in cold weather, until the excess water gasses off, but I'm reasonably sure no long term damage will occur.

You could try doing longer than normal charges, at a low'ish current, to both balance the cells and help get rid the excess water. If you can charge with the covers off the over-filled cells this will probably help.

Keep an eye on the overfilled cells and cover the vents as soon as the level drops to where it should be. I think you'll find they'll gradually recover OK, as the voltage at the moment sounds about right.

Jeremy

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badnewswade
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Re: Think I've overfilled my VRLAs

Postby badnewswade » Wed Mar 09, 2011 4:12 pm

I've got an idea - what if I run them flat with a dummy load then syringe off the excess? It should be depleted of most of the electrolyte when it's flat, right?

http://en.wikipedia.org/wiki/Lead%E2%80 ... ochemistry
In the discharged state both electrodes turn into lead(II) sulfate (PbSO4) and the electrolyte loses its dissolved sulfuric acid and becomes primarily water.


Really don't want to risk excessive gassing as I have at least one incurably dodgy connection in my bike, one spark and *BANG!* I'm deader than Elvis :cry:
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ChrisB
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Re: Think I've overfilled my VRLAs

Postby ChrisB » Wed Mar 09, 2011 5:14 pm

Personally I wouldnt want to run them that flat as your likely to cause more long term damage stressing the cells than just letting gas a bit over a longer period.

My way would be to set them up on the bench, tops off, and just give them a nice long slow charge and keep them gentley gassing until the levels drop.

Its not going to be quick, could be looking at a couple of weeks possibley, depending on the charge current.

Another issue you may have if you flatten them is this will force the electolyte out of the cells and they will over flow, PbSO4 is quite large and will make the plates swell which is why you see battery cases on old batteries bowed out, this also can cause damage to the plates, which is why you dont really want to do this.

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badnewswade
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Re: Think I've overfilled my VRLAs

Postby badnewswade » Wed Mar 09, 2011 5:30 pm

Oh no, not that flat - just down to about 12v or so. Done that before with no problems. Would that be OK? I don't have a sophisticated enough charger to do ultra long charges - just two scooter chargers, one which is less slow than the other. I suppose I could use the slower one and just take some of the stuff out, so that at least it's not so far above the mat. I'm talking a couple of 3 ml pippete fulls from each cell, not loads and loads.


EDIT:
Hang on, I'm confused. Which will create more gassing, the slow charger or the normal one? Want more gassing before I close the batts and less after....
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badnewswade
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Re: Think I've overfilled my VRLAs

Postby badnewswade » Fri Mar 11, 2011 12:52 am

OMG it's getting worse - now they're spontaneously venting!! Batteries are emitting gas even with no load or charger attached! :shock:

Should I be worried, or just leave them to it - maybe this is their way of fixing themselves?
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Re: Think I've overfilled my VRLAs

Postby ChrisB » Mon Mar 21, 2011 10:30 am

They will gas to a degree by themselves, especially if you've over filled them a bit as there is less room for the gassing to go into.

Of course it could be that they are self discharging due to crud build up in the bottom of the cells, in which case its game over really.

You dont really need a posh charger, just a really basic one that will do a trickly charge, you may need to add a current limiting resistor into the circuit to keep the charge current nice an low though, I'd say maybe 250-500ma is what you need to aim for might be even less.

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badnewswade
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Re: Think I've overfilled my VRLAs

Postby badnewswade » Mon Mar 21, 2011 10:50 am

Well, I've equalised them, glued 'em down, done a long float charge of about 36 hours (with the scooter charger) and put them back in the bike. I didn't draw off the excess after all - it either wouldnt' have helped or it would have hurt the batteries.

Good news: They're in GREAT condition. Almost as good as new - I took them to Stanton Drew and they got me there and (just) back (23km), just like when they were new. OK I did drive very slowly when I could and was on sparks by the end, but it never got so low that it started cutting out. The problem of sagging under load is much, much reduced, although not eliminated entirely - I could probably have been more agressive with my equalisation charge. I have isolated the hot wire from the others to as large a degree as I can, used a high temp terminal block and put some heat shrink on it so I'll know if it gets hot. It doesn't, but I haven't put the second string back in yet.

Bad news: It still gasses noticably and stinkily on float charge. I'm giving it a long float charge - over 12 hours - and then think about putting the second string back on. (which I've also equalised, having learned the lessons of the first string)

The second string is the scary bit - the scoot's weedy 800w motor isn't really designed to take the weight and neither is the luggage compartment, so the hot wire probably will heat up if and when I put it back in. So maybe I should try a few more runs and float charges before I do that... also the extra batteries will block some of the ventilation, on the other hand it might not gas so much if its' kept under the gassing voltage by the other batts.

Long term, a Lithium battery - almost certainly another Ping battery - looks like the only way to get proper range on this bike without shortening its' life, not to mention mine. :shock: There's a real risk of accident from having four 20ah batteries in the luggage compartment so I can't reccomend it except as a stopgap. Maybe if I reinforced it... I digress.

Acceleration performance is just fine just as long as it isn't overloaded with extra batteries, but sadly to get any kind of usable range that's exactly what I'm going to have to do - for now. I'm going to go all out to save up and after I MOT it... maybe I'll go for it. I really like this machine despite its faults, and don't want to waste money buying another one when I could be enjoying the benefits of Lithium.

Has anyone else tried putting a big Ping battery on a proper moped? I know someone on the Electric Motoring forum did but he seems to have vanished... hopefully not because it didn't work out! He seemed a little bit down about it, although he didn't say anything to indicate that it was an outright failure.
Last edited by badnewswade on Mon Mar 21, 2011 11:07 am, edited 2 times in total.
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ChrisB
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Re: Think I've overfilled my VRLAs

Postby ChrisB » Mon Mar 21, 2011 11:05 am

Glad its all working out fine now 8)

badnewswade wrote:Has anyone else tried putting a big Ping battery on a proper moped? I know someone on the Electric Motoring forum did but he seems to have vanished... hopefully not because it didn't work out! He seemed a little bit down about it, although he didn't say anything to indicate that it was an outright failure.


I dont think Ping does big enough BMS's for his batteries, and the batteries may not be up to the discharge currents, I wondered about a set for my one, but as it can draw 120ish amps this puts it outside anything Ping currently does so have been "trying" to learn about the other options out there, but I'm not doing very well with it currently :oops:

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badnewswade
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Re: Think I've overfilled my VRLAs

Postby badnewswade » Mon Mar 21, 2011 11:12 am

What's your motor's wattage? I'm thinking that mine is low enough that it won't have that problem - he does a 40ah set now, which if it's double the 20ah supports sustained discharge of 2c (80amp) and max discharge of 120 amp, although the safety cut-out would kick in at 100 amp. Oh, and you can get high rate BMS. Might be worth emailing him to confirm those specs... it doesnt' sound as though yours is that much higher than what the standard BMS gives you to be honest.
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