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Aircraft battery (Gill versus Concorde)

They can be paralleled though for aviation applications you might want to have them separate for a degree of true redundancy. There are also now larger capacity A123 batteries – 4.4 amp hours. so you would be talking 40 cells to replace your 28v 20Ah battery, not 80. The Cessna 152 battery earlier was only 13.6 aH and looking for a 24v 20aH battery, the weights seem to be around 20kg. You don’t particularly need to have individual taps for A123 batteries (for various reasons, balance charging as used on LiPo batteries tends not to be helpful, and they’re much more robust with respect to slight overcharging or over-discharging) though you might want to monitor them individually to find any bad cells early.

I think the main problem charging them using a commercial charger, is that you would probably want to be drawing current at the same time as charging. By and large commercial chargers judge charge state by monitoring voltage/charge current, gradually reducing the charging current as they approach capacity. If the load were to vary as you approached full charge, commercial chargers would get terribly confused. I can see ways round this – the simplest being just accepting a loss of 10% of capacity. But at the end of the day they’ll never be a straightforward replacement for a lead-acid battery. An electrical system designed from scratch could work nicely with them.

My helicopter batteries have 18 cells (9s2p, in the parlance) and seem to have held up to everything thrown at them apart from one that I dropped down a flight of stairs onto a hard surface. 2 cells got squashed but were so inconvenient to replace I dismantled the rest of the pack. It was indoors so I was very glad it wasn’t a LiPo which almost certainly would have flameballed.

I agree with you that LiPo cells for radio control don’t last, but for A123 cells, despite the troubled history of the company, the hype seems to be true.

Last Edited by kwlf at 24 Jan 14:14

My 24V Gill battery is from 2006. The condition is very good since I take the battery home to a warm place in winter time. Never had any trouble.
The maintenance company wants to perform a test due to next annual inspection. I have never heard about a battery test before. Are there limitations on aircraft batteries ?

Berlin, Germany

Your shop is right, a battery older than 5 years should be capacity tested. A lot of shops tell users they have to replace the battery after 5 (or whatever number of) years but this is wrong.

Check Gills’ maintenance manual for instructions.

7.7.1 To ensure continued airworthiness the battery should be removed and capacity
tested. The recommended service period should initially be at 800 ± 50 hours
or 11 ± 1 calendar month(s) whichever comes first. After the initial service, the
next check should be at 400 ± 25 flight hours or 6 ± 1 calendar month(s),
whichever comes first. The capacity test shall be performed as follows:
e) The battery is considered airworthy if it meets 80% of the one hour
capacity rating (48 minutes to the cut-off voltage).

The airworthiness definition is binding but the fact that you have to perform this capacity test is not. Still, your shop is right. I built my own capacity tester for €8 in parts and do it myself.

I organize my flying so that a dead battery will not ground me, even when I’m on a different continent. If my battery dies, I need two car batteries to start the airplane and have an extra internal battery as a backup for the alternator to keep avionics going. Therefore I keep my battery as long as it works. Others choose to replace it every few years. Usually lead batteries degrade due to sulfation of the electrodes and you can keep it going almost indefinitely with pulse chargers.

Last Edited by achimha at 09 Feb 15:01

I can’t help wondering what the issue really is. Would there really be any legal/official requirement for a battery check under any regime (EASA/FAA/..)? I can see no reason why. A dead battery can never create a hazard, can it? Whether such a check is wise is quite another matter, depending much on one’s overall layout.

Still less to the point seems checking the one-hour capacity – the battery is there to get the engine started, right? One might argue about powering avionics in case of total electrical failure – but if the failure is really total, the battery won’t help either. Plus, today’s glass stuff has its own internal batteries for 30 or 60 minutes autonomy.

EBZH Kiewit, Belgium

The battery needs to be airworthy, otherwise the aircraft is not airworthy because the battery is required equipment (at least for most aircraft). If a mechanic suspects the battery is not airworthy, he needs to employ an accepted method of determining the airworthiness. In case of Gill and Concorde, such methods are spelled out in the maintenance manual.

The mechanic can also say “the battery is probably OK and once it isn’t, the customer will come back”. I think highflyer’s shop is taking a sensible approach.

Last Edited by achimha at 09 Feb 15:30

Still less to the point seems checking the one-hour capacity – the battery is there to get the engine started, right? One might argue about powering avionics in case of total electrical failure – but if the failure is really total, the battery won’t help either.

The electrical failure (failure of alternator) is the reason for this testing. More and more is asked for electrical load analyse with modification of avionics, UK CAA allready had this for years. They require the battery (at 80% capacity) should be suffient for powering electrics in an emergency (alternator failure).

Some modern avionics have internal backup batteries, which also require some sort of testing, as it is part of their certification.

That it will detect a bad battery before you have starting problems is just an extra advantage, but not the reason for capacity testing.

UK CAA seem to have knowledgable people for the electrical regulations, with this battery testing, 2nd avionics master switch and and low voltage warning light which works on bus voltage. All these requirements make sense.


More on battery load testing here

Shoreham EGKA, United Kingdom

Peter, that looks like you are civilly reminding me I am repeating myself after having been corrected… thanks for patience!

EBZH Kiewit, Belgium

A load test is pretty easy to figure out if you have a suspicion of a problem. Since the battery is portable my method is to take it to the auto parts place, where they will check it for free locally.

I maintain 12 vehicle batteries, and the way to stay sane in doing that is to keep them all on battery tenders all the time. Really one of the most attractive things about plane #1 is that has no electrical system (and no hydraulic systems either). Only when you’re searching for AAs to power the radio does it become more of a problem…

Last Edited by Silvaire at 09 Feb 16:04

Not reminding you of anything, Jan

The thread just reminded me of something. There is a lot of disinformation going around about load tests damaging batteries but at anywhere near the correct discharge rate it cannot do any damage.

One could argue that any battery that starts the engine is a good battery, but you can be down to maybe 50% and it will still start, but you get less time in case of an alternator failure.

Last Edited by Peter at 09 Feb 16:22
Shoreham EGKA, United Kingdom
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