Jump to content

Recommended Posts

Battery maximum charge voltage may have been the culprit in some of the cases mentioned above. If the "smart" charger is expecting to charge to (say) 14.8 volts, and the battery chemistry won't go above 14.2 volts, then you have a problem. If the aircraft regulator is fairly basic (say something like the zener regulator on an early motorbike) then it won't let the battery charge above its regulating voltage, so will never "fully charge". I don't know what the charge system is like in a Jab, so not sure whether trying to take the voltage above the aircraft's usual max voltage will cause catastrophic failure in the aircraft regulator. I suspect that there is more than one contributing factor here.

 

David

 

 

Link to post
Share on other sites
  • Replies 73
  • Created
  • Last Reply

Top Posters In This Topic

I bought a smart charger 3 years ago from Aldi & it has always worked as specified & only cost $30.00. It recognises the battery type whether it is 6 volt or 12 volt & has several charging modes. I use the motorbike mode on my aircraft battery (Motobatt 21Ah AGM) as it is a gentle charge of 0.8A. Car battery mode charges at 3.8A. There are 3 stages, the last being trickle charge which is 0.07A. The only problem I had was when I left the aircraft master on for a week & there was no charge at all in the battery so the charger was not smart enough to recognise it & decided the battery was stuffed so would not charge it at all. I borrowed a flash Ctek charger from a friend & began charging it in the AGM battery mode as this is my battery type. Within about 30 minutes the battery was almost too hot to handle so I disconnected it & left it for several hours to cool down. Once cool I put my smart charger back on & as it now had some voltage it was recognised and took another 24 hours to fully charge. I reckon I was lucky as the the Ctek was obviously pumping umpteen amps in & the battery could have melted or caught fire.

 

I have a small 20 watt solar panel on the hangar roof which runs through a controller/regulator & keeps the 2 batteries in my hangar trickle charged as well as the aircraft battery. I have the 12volt power outlet wired directly to the battery bypassing all of the aircraft electrics & a cable from the solar panel hangs from the ceiling & I plug it is before leaving the hangar. Sometimes I forget as in when I left the master on.

 

 

Link to post
Share on other sites

My experience with those batteries that once they overheat they are finished. That seems to be a recognised fact. The gel gets holes in it that don't heal. I've only had it with batteries with some time on them.. You need a heat sensor. for protection. Nev

 

 

Link to post
Share on other sites
My experience with those batteries that once they overheat they are finished. That seems to be a recognised fact. The gel gets holes in it that don't heal. I've only had it with batteries with some time on them.. You need a heat sensor. for protection. Nev

The battery has worked perfectly for almost 12 months since it was recharged after the full discharge. It isn't a GEL battery, it is an AGM (Absorbed Glass Mat) battery, capacity 21 A/hr, 310 CCA.

 

 

Link to post
Share on other sites

 I only know what I have been told and have experienced. The batteries I refer to are AGM low maintenance  Use in any position batteries. Plate batteries have plate warpage when overheated. The gases coming off them are also capable of harming humans. I've had a  large   lead acid battery do a meltdown in a tractor also.  A sudden overheat is not normal unless you were charging it at massive rate which is a no no   anyhow. When something happens in the air you can't just pull over and lift the bonnet. Nev

 

 

Link to post
Share on other sites

If the charger was only putting say 100 mA into a new Odyssey battery, by what mechanism could a fire have started? It takes a lot of energy to get the heat up to start a fire. I know that the battery would have this energy, but how would it start? It would take some sort of internal short-circuit I guess, but just how this would happen?

 

 

Link to post
Share on other sites

The charger has been tested as working okay since the fire. We will never really know the cause. By the way, if you look at the wiring diagram for the Jab, JTM001-8, page 268 of 301 you will see an error. A relay is permanently wired across the battery!!! Jabiru have confirmed this is a mistake and the connection should be on the bus side of the switch.

 

image.thumb.png.455870f4d749b8c00f128d2de0bf1937.png

 

 

Link to post
Share on other sites

Maybe it is under reported but it is very rare these days to hear about a car or aircraft bursting into flames when it is “switched off”. Obviously a crash is a very different situation but it is hard to see what could cause a fire in a cold, hangared aircraft that has its battery physically isolated - apart from an intrinsic battery malfunction or the effects of an external charging current. Is there any alternative explanation?

 

 

Link to post
Share on other sites

I had a car battery explode in my face once. My own silly fault: it was fully charged and bubbling, and I disconnected the charger leads without turning it off. I had acid dripping down my face. Luckily I wear glasses so none got in my eyes. I'm more careful now.

 

 

Link to post
Share on other sites

Thanks Jab7252, I read your “light reading” - and will never approach my Savannah again without my acid-resistant protective gloves! But, seriously, there was obviously something wrong for a Jabiru to spontaneously ignite. In this particular situation, even though the Jabs were used fairly frequently for student training, the standard batteries were often unable to start the engine. Hence the need for leaving them on a charger. Maybe there is a need for some guidance on best battery or best way to maintain adequate charge. 

 

 

Link to post
Share on other sites

I suspect that 'unable to start the engine' is more a result of not knowing how to start a Jabiru. Using the choke correctly is most important and perhaps students are not being taught the correct procedure? It's in the manual. Cold mornings are the worst. If the battery cannot crank the engine at 300RPM or better it won't fire. If the battery used by Jab was not up to the task they would have picked up on that long ago.

 

 

Link to post
Share on other sites
I suspect that 'unable to start the engine' is more a result of not knowing how to start a Jabiru. Using the choke correctly is most important and perhaps students are not being taught the correct procedure? It's in the manual. Cold mornings are the worst. If the battery cannot crank the engine at 300RPM or better it won't fire. If the battery used by Jab was not up to the task they would have picked up on that long ago.

We get some pretty seriously cold mornings over winter, and correct technique won't cut it.  A battery booster is pretty important, and keeping batteries on charge overnight helps too.  Sometimes we have to resort to shoving two hair dryers into the cooling vents for 20 minutes to warm up enough to start.

 

Jabs don't like -1 degree starts

 

 

Link to post
Share on other sites

I fly a Drifter - if the ambient temperature is not in the range of 20 to 30 degrees Celsius, I don't take off.....I think I'm the ultimate Fair Weather Pilot - but I'm not young and I do like my comforts.....a Lot....

 

There I was, flying along thinking "gee it's a bit hot today" - then something ahead caught my eye - what the hell is that - oh it's just a leaf - wait, there's another - and another - and then "why am I looking up and seeing the ground?"

 

BP

 

 

Link to post
Share on other sites

 Flywheel attach set up is stressed by having a powerful starter on a jab. Use multi grade oil  in cooler climates. Don't think I would recommend a power pack with a Jab.. If a battery is gassing  in a confined space the gasses are hydrogen and oxygen and the slightest spark will cause an explosion. Vent the area. A fan blowing on it is OK as the gases don't get near the fan. I f you are caught in a real freeze,  IF  you have the time warm the engine with a hair blower or suitable fan type  heater before attempting the start. Don't open the throttle much (if at all). It cranks easier when the cylinders don't fill, and the choke only works with throttle closed with that type of carb. Nev

 

 

Link to post
Share on other sites

just upside down, or so close to it it wasn't funny - reckon I flew the left wingtip into a big strong thermal, it just flicked the Drifter into a roll so quickly I was way over before I knew it - in hindsight I should have clicked as soon as I saw the leaves, but it all happened so quickly I really didn't get a chance - I recovered fairly quickly and didn't lose much altitude, I was at about 2,000 at the time, I would not want that to happen to me on short final...

 

speaking of thermals, did anybody see my latest article in Sport Pilot magazine?  The pictures of a graphical representation of a glider in a thermal is quite interesting....

 

 

Link to post
Share on other sites
We get some pretty seriously cold mornings over winter, and correct technique won't cut it.  A battery booster is pretty important, and keeping batteries on charge overnight helps too.  Sometimes we have to resort to shoving two hair dryers into the cooling vents for 20 minutes to warm up enough to start.

Jabs don't like -1 degree starts

The Jab Cold Start kit sure helps.

 

 

Link to post
Share on other sites
 Flywheel attach set up is stressed by having a powerful starter on a jab...

Nev that is one of my concerns, now that I seem to have solved most starting issues. (After fitting a Cold start kit, powerful LiFePO4 battery and sorted out the idle mixture.) 

On hitting the starter, the engine is now subjected to very violent forces, presumably increasing the chances of shearing off flywheel bolts.

 

Two possible solutions:

 

Perhaps we can introduce some way to "damp" the initial cranking.

 

Perhaps bolts in a warmed engine may be less prone to shearing than cold ones. Preheating with a hair dryer of heat gun is pretty easy.

 

 Your thoughts?

 

 

Link to post
Share on other sites

Old K, I really like the idea of "dampening" the initial cranking force. It should be possible to do this electronically . Maybe stronger bolts would make this unnecessary, but it could well be that a soft start cranking is better.

 

 

Link to post
Share on other sites

Pulling the prop over before each start is, in my opinion essential, to not only check the compressions, but also to introduce some heat into the cylinders . I always pull over at least 10 blades before each start . Have never had any start problems . My first battery lasted 6 years . My second Odessy in now 4 years and neither have required any additional charging. I live in on the Victoria South coast . It gets real cold down here in Winter .... Bob 

 

 

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...