bubbling batteries

[dconn]

Hi All,

Soon I'm planning on living off-grid with my existing PV panels and an almost ready Piggot / Volvo turbine (coils & magnet arrangements are as per Hugh Piggott but with 9 1/2 foot prop and a volvo spindle).

Anyway, and back to the topic, tonight I went out to the batteries to move the inverter from one battery bank to another and I noticed that my 600AH 12V battery bank made from 4 X 6V 300AH lead acid trojan batteries was hissing/bubbling.  At least I think two of the batteries were hissing from putting my ear close to them.  Thats strange because the battery bank was only at around 12V and today was not all that sunny (lots of clouds).  Normally this bank has about 400W of PV connected to it via. a solar charge controller but when I noticed the bubbling it was nighttime (so no sun/charge at all).

So maybe these batteries have gone bad some how?  (although as I'm writing this the batteries are supporting a couple of CFLs, a couple of [notebook] computers, the ISDN telecoms and network stuff so they are still working a bit for sure).

I'm going to invest around 800 euro within a couple of weeks on 12 X 2 volt 800AH forklift cells that bolt together (each cell weights 38 kilos!) and this will be my new house battery bank but I was hoping that my existing 12V 600AH battery bank would survive to allow me to work on my computers (to make some useful money) but I'm not sure now with this bubbling thing.

What do you think?  Do you think my batteries have had it?

Thanks for any information!

Derek

[ghurd]

I read, and have seen, that unusually "bubbling batteries are getting near the end of their usefull life".

If they are cooked, maybe more AH should be used next time. Keeping the state of charge above 70%.

Also. Search here about 'EDTA', sulfation, and de-sulfators.

G-

[crashk6]

Use a hydrometer to check the specific gravity of each cell in the batteries that where "bubbling" you may have some cells out of balance. Which would cause them to boil like that... it could also kill the batteries in question and damage the bank as a whole. The hydrometer will tell you more than a simple voltage reading. If you indeed have out of balance cells... desulfate then run and equalizing charge and check the specific gravity again.

regards,

--

crashK6

[wpowokal]

Derek do you have two seperate banks of 12V or are they in series 24V?

Either way the "idle' bank can discharge into the in service bank, which it seems is what you noticed.

allan down under

[dconn]

Hi Allan,

This bank is four 6V batteries - two sets of two 6V batteries in series and both 12V sets in parallel - so 12V total.

It must be bad cells "sucking" the power from the good batteries all right - I think its time for me to buy myself an SG meter and go look.

I'm about to upgrade the main power to 24V and buy new[ish] batteries anyway but I didn't have any plans to get rid of my 12V system.

Thanks everyone for your help,

Derek

[wpowokal]

Derek, I assume both 12v banks are and remain connected while you are discharging one set.

Think of it this way, you have two tanks of water cross connected, and therefore at the same level.

Now you start drawing water from one tank, so water will flow from the other to try to maintain equal levels.

If I understand you correctly what you are experincing is normal. Have you done a discharge test on your batteries? This will establish the remaining capacity of your batteries.

To test;

Fully charge a bank, including a 3 hour equalising charge (assuming flouded lead acid), isolated that bank and allow to sit for say 12 hours(this lets the surface charge disipate).

Place a load on the batteries equal to 10% of amp hour rating, monitor each cell if possible, and cease the discharge test at 1.85V for any cell, under load.

Multiply the amps x time, the closer this figure is to 20% of your batteries amphour capacity the better your batteries are.

Now don't re-connect both banks until you have charged the test bank to equal volts with the other, or large currents will flow.  

Hope this helps

allan down under

[Ungrounded Lightning Rod]

This bank is four 6V batteries - two sets of two 6V batteries in series and both 12V sets in parallel - so 12V total.

It must be bad cells "sucking" the power from the good batteries all right - I think its time for me to buy myself an SG meter and go look.

The problem might be the batteries that AREN'T bubbling:  If one of your 6-volt batteries is low, or has a bad cell, the other one will be seeing more than 6 volts and take an overcharge - electrolyzing the water into gas that bubbles off - or hisses if there's a LOT of overcharge current.  (If the low battery has one or two dead cells the good cells in it should also be bubbling...)

You might have a dead cell somewhere.  Or you might just need an equalizing charge.

I'd try bringing the electrolyte levels up to balance, applying an equalizing charge, recheck / refill the levels afterward, and see if the issue goes away.  If it doesn't clear up after a couple trys you've probably got some batteries nearing their end-of-life and should start looking for replacements or to do your 24V upgrade (unless you feel like playing with extreme life-support measures for the old ones).

If ALL the cells are bubbling you're probably overcharging your bank.  Check the battery voltage of the whole bank to see.  If it's too high, check your regulator or dump load controller.

Since you've got a wind machine you could easily be feeding your batteries far more power than they can take (especially if you're charging one bank while discharging from the other - a bad way to run - and/or if you have no dump load and controller.)

[dalibor]

because i am working with batteries, i will write few words.

first of all, you should check density in every cell, like others have already said. also check voltage level of every cell, it should be around 2,23 V per cell in "floating".

when cell is bubbling in "floating" conditions, it almost always means it is discharging it self, because there is somewhere small connection between poles. this is caused by making of sulphate (my english isnt so good, forgive) on plates. then this cell is sucking energy from healthy ones and from power supply (solar, wind,etc).

if cell has transparent case, check out if there is some sort of "mud" on its floor, it means your plates are defragmenting and total capacity is becoming lower. it also shortcut between "+" and "-" and discharge cell.