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Battery load test shortens battery life - really?

I saw some baterries being load tested today. I asked the man doing it about this…

Apparently the current drawn is only 1C i.e. from a 15Ah battery it is 15A. That’s nothing! The starter motor current is 50-300A depending on the starter motor.

There is no way load testing at 1C can possibly affect the battery life.

Last Edited by Peter at 21 Nov 21:16
Administrator
Shoreham EGKA, United Kingdom

What is the best way to test the condition of an airplane battery, Peter? With an all electric airplane like the SR22 it is essential to have good batteries.

With an all electric airplane like the SR22 it is essential to have good batteries.

Really? I should think a backup alternator more relevant. Given the current draw required for IFR flying, no battery will hold out long anyway. Especially when no gyroscopes are vacuum driven. The battery exists to get the engine started, no more, no less.

EBZH Kiewit, Belgium

Not in the SR22, unfortunately. While it does have a second alternator, it is smaller and cannot power the entire electric system, only the very essential stuff. But there are things that, even though not totally essential, are still very nice to have in IMC. For example a working autopilot. And when you lose alternator #1, your AP will only last as long as your battery holds up…(this applies only to R2 DFC90 equipped ones and is currently a very hot topic over at COPA…) Anyway, the AP is just a very particular example, but there is much more other equipment that will stop working when BAT1 has died. It’s really quite complicated and certainly, a fully redundant electrical system as in the C400 would be much better.

BTW, it has often been said that a battery will lose a lot of its power way before it eventually fails to start the engine. Failing to start a cold engine is really one the very last breath of a battery. That’s why battery testing is important and it’s done at each annual. I have forgotten the exact procedure, though. I think there is a “quick ’n dirty” test and a more thorough test, the latter requiring much more time, though.

Actually I am no longer too convinced about these tests either. Let me tell you what happenend last winter: all of a sudden, after six and a half years in service, our BAT1 suddenly stopped working (unable to turn prop). Thing is: only a couple of months before, the battery passed the “test” just fine. According to the above rationale, this shouldn’t have occurred, in other words, the slowly failing battery should have been detected way before it didn’t manage to turn the prop any more.

Last Edited by boscomantico at 22 Nov 14:54
Mainz (EDFZ), Germany

Batteries can lose capacity suddenly.

However IME this happens with the Gill ones. Concorde ones give you loads of warning; mine failed the load test but was still driving the Skytec high speed starter perfectly.

I would not touch Gill again.

There is a lot of disinformation about not being allowed to put a Concorde battery in in place of a Gill one. Many FSDO inspectors now agree that it is a Minor mod, and I think it is the same under EASA, but you can always find somebody else who disagrees. So Concorde has got a lot of STCs – for those A&Ps who don’t want to take chances

Administrator
Shoreham EGKA, United Kingdom

I have a Gill battery and I’m not happy with it. Some Commander owed from Manston told me all problems stopped since he switched to Concord batteries.
Next battery will be a Concord!!

EGBE - Coventry, United Kingdom

In fact Peter, I use Gills. This is what my service outfit recommends. For what reason exactly, I don’t know to be honest.

Anyway, as a matter of fact, I have been very happy with that Gill (243) battery. Never had a single problem before it failed, and when it failed, it was (I just verfied) not only 6.5 but 7.5 years old, which is, I think, darn good for an aircraft which is stored in a non-heated hangar and whose battery was never connected to a “trickle charger” of any sort…

FWIW, the SR22 fleet is pretty mixed between Gill and Cocorde batteries.
Last Edited by boscomantico at 22 Nov 15:23
Mainz (EDFZ), Germany

I would not say Concorde necessarily last longer before they fail the load test (about 5-6 years of 100-150hrs/year flying in my case) but they last probably a couple of years longer before they are evidently shagged i.e. can’t turn the starter.

The other big advantage of Concorde batteries is that they can’t dry out – they are solid electrolyte. No topping up ever, and less risk of acid leakage and getting your battery compartment eaten

For what reason exactly, I don’t know to be honest.

Most likely because the MM/IPC says so. They cannot possibly be saying it on grounds of quality or performance. Gills are significantly cheaper though.

Last Edited by Peter at 22 Nov 16:14
Administrator
Shoreham EGKA, United Kingdom

Most likely because the MM/IPC says so

No. As I said, you can fit both on the SR22.

Gills are significantly cheaper though

Gosh, and I really thought that Gill battery was outrageuosly expensive when I had to buy the new one…
Wonder what the Concorde equivalent would have cost me…

Last Edited by boscomantico at 22 Nov 16:19
Mainz (EDFZ), Germany

PA-46 almost always use Concorde now. That said, I am going to be needing a new one in mine this winter. When you get to see the max temp on starting the engine you get a realtime view of battery performance. I keep it on a maintainer but don’t know how the previous owner looked after it.

EGTK Oxford
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