Microlighters

Today I took a little 2 hour flip and on returning noticed a feint sulphur smell in the cockpit. I looked under the dash and the battery was swollen like a soccer ball and very hot. It was one of those sealed units.

Now it is mounted against the firewall, albeit behind the fireproof material so could it be

1. heat?
2. overcharging (my MGL unit shows 14.5V)?
3. a faulty plate shorting out?

Most likely no. 3
Do you want a technical write-up on how a battery works and what causes a plate to "short" out?
Naw...I don't feel like writing :D

BTW, that battery is toast. Throw it away and get another one.

Thanks Duck, I was hoping it was number 3

the other 2 are more complicated/expensive to sort out.

It was a really old battery, about 5 years old, that came out of my old plane. It had stood for 18 months before I recharged it and put it in the BB

Just make sure it is a deep cycle battery you replace it with. The rattex charging system will NOT charge a "cyclic" battery. Learned the hard way..... So you don`t have to........ :D

Then on the other hand, the "sulphur smell".......are you SURE it was coming from the battery??

Yip, the battery was swollen and hissing like a snake on heat

The acid used in batteries is Sulphuric Acid (H2S04) hence the sulphur smell.

Morph, if it's a NORMAL sealed LEAD ACID battery, then 14.5v is right up there on the upper limit. If it's a true Gell type then that voltage is too high. Gells don't want more than 13.9v... tops. They're gonna get cooked above that. Yes, those fractions of voltages ARE critical.

The Rotax regulator should not be putting out more than 13.9v. (This is MY opinion......others may differ)

The simplest battery to use is the lead acid motorcycle type that can be visually checked, tested with an hydrometer and refilled with electrolyte if necessary.

I'm with Duck on the 14,5V is too much, when you feeding it 14.5V all the time. Although you can go up to 14.4V or even 14.7V (AGM Batteries?) when controlled by a charger, but then the amps are dropped and it is done for a limited time ONLY. Overcharging the battery will cause gassing and will dry it, but you can also undercharge a battery, which will also shorten its life.

In the plane, I would go for 13,8V.

Would also point to no 3 as a possibility.

The sealed batteries will swell when overcharged, shorted internally, heated etc. I do prefer them however, for just about any use (old 7Ah batteries make great doorstops in the workshop ). Biggest advantage: they don't spill

Yes, Duck does have a valid point, you can check lead acid motorcycle type levels and top them up, but I prefer the no spill advantage.

Boet, could you pls elaborate on the "Rattex won't charge a cyclic battery"?

Got myself a CTEK charger and use it to desulphate and maintain my batteries from time to time. Works great in the plane and in my small bakkie which loafs a lot. Used to buy a new battery for the bakkie at least once a year. The charger revived the dead battery, which was a year old at the time, and it's still going. Plane's three (?) year old battery wouldn't turn the 582 the other day after standing for a week, put the charger on for a day... nou het hy nuwe woema!

Best R800 I spent this year. (XS 3600 at Battery Centre. Outdoor Warehouse, LA Sport?, www.bushpower.co.za and some other places also have them)

Check out www.ctek.com for interesting info.

Morph wrote:The acid used in batteries is Sulphuric Acid (H2S04) hence the sulphur smell.

The only time that I witnessed this awful smell was on my Opel Corsa a few years back. Smelled worse than a rat cooking on the exhaust manifold.

Diagnosis – overcharging.

Regards
John ZU-CIB

PS: Edited to fix typo

I'll measure the charging voltages today with a Fluke meter and let you know.

According to the 912 installation manual the rectifier/regulator supplies 14V +/- 0.3 volts.

Morph, Im sure you are overcharging. Duckie is right and to be safe Ill limit the continious charging to as low as possible, say 13.5 or so. In normal operation the battery acts more like a buffer than a battery as you only draw current when you start her etc. (this is an illustrtive statement for those boffens (Rubber Duck)who is now going uhm....) therefore charging that slow shouldnt make a difference.

San

Well after some closer examination and monitoring the voltages at flying revs as opposed to 14.5V at idle I noticed the voltages hitting 19.1V

So, definately overcharging and now I am in the market for a voltage regulator/rectifier for the 912. Any ideas of price? Maybe a second hand one somewhere?

Eeeee, Mr Morph, thet is a verryverry ekspensif iatem. Maak jou reg vir ten minste 10 buffels.
Die verskil tussen n "Deep cycle" en n "cyclic" battery:
The cyclic batt is used in electric wheelchairs, shopriders etc. You need a special charger to charge them. IE Cyclic 500. It will take 500 charge/discarge cycles before going down. Thru ignorance fitted one to an aerie. Had endless shit untill an expert relieved me of my ignorance induced misery. The poor 912`s charging system would NOT charge it.
No problemos with an ordinary deep-cucle battery.
The leas acid batteries leaves you with an acid spill risk. Not good in ANY airoplane. I have been using these "gell cell" batteries now for many years, and never had any problems. The first one in my Turbi lasted 11 years, was worth every cent of the 1984 R750 that I paid for it. :D
Note, if thes gell cell batteries goes completely flat, throw it away. It will be troublesome. My experience. :D