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attackpilot

Active Member
Hello Everyone:

I am hoping that someone can spread some battery knowledge my way.

Yesterday my battery died while I was trying to start my plane. I knew that it was weak, but I tried until it couldn't turn over the engine. So I hooked it up to a charger last night. I tested it with a multimeter before I put it back in the airplane and it read ~13.8 volts. After I stuck back in the plane and did a quick run-up I read it again with the multimeter and it read ~12.4. I know that I need to fly for an hour or so to get a good charge on it, but should it drain that much?

Joe Hutchison
RV-10 Tailkit
Flying Davis DA-2A
 
I would think the charging system should have sustained it. Was the alternator putting out during the runup? If you suspect the battery is weak and the charging system is OK, Get a PC680 Odyssey battery.

Roberta
 
w/o alternator?

After I stuck back in the plane and did a quick run-up I read it again with the multimeter and it read ~12.4.
Click to expand...

was that 12.4 with the engine running, or not?
 
Battery

Joe,

As James queried, was the 12.4V with the engine running ?
If you tested the voltage just after it being charged on the bench, it would most likely show a higher than normal charge, but then settle down to a more normal reading around 12.4 V

How old is the battery ? When was the last time it was charged ?
How cold was the weather at the time ? All these things need to be taken into account before an educated assessment can be made.

Martin in Oz
 
The 12.4 reading was after I did the runup without the engine running. I know that idling and a short runup is not enough to charge the battery properly, but I am just wondering if over a volt drop is normal. The battery is two years old.

Thanks again
 
Yes, that is normal. The starter pulls the battery down considerably. It takes more than a short run to replenish the batter after a start.
I use the Powersonic sealed batteries and they always last at least 4-6 years.
 
If it starts the engine it's great

The start engine requirement is extreme - like pouring water out of the little Amp-hour bucket. As you said, it takes a while to dribble it back full again. If you start a few times and don't have sufficient normal operating time to recharge the battery the charge will be reflected in a Voltage that will be too low to start the engine. Then you will have to get out your battery charger to recharge it, if it is rechargable. The good news is, if you can't recharge it a new battery will make life good again. I think I'm on my 5th Concord battery that has failed (not rechargable) because I left the Master Switch on. I know, I know others may be better, etc. etc. but the Concord battery and my airplane are made for each other - I just have to fix the brain fade.

Bob Axsom
 
I never turn off my strobe lite. You always take one last look at your baby and if that lite is flashing you forgot something.

Ollie
 
Lead Acid battery voltage

A good condx, fully charged, lead acid battery should read 12.6v or 2.1v per cell. Recovery time after high load, start, etc., is dependent on battery condx, assuming charging circuit is functioning properly. I have never seen mine read above 12.6v, with engine not running or when selecting alternator field off, and engine running. Incidentally, my near new battery is near fully charged after 2-3 minutes, per my amp gauge indications. It may take a little longer to get that last few percent of charge, but the recharge process is basically over in short order. It is fair to point out that my engine starts on first turn, so not much battery drain. If I had a hard to start engine, then would draw even a new battery down more, take longer to recharge. If it's taking an hour, you need a new battery, have a charging system or amp gauge problem, or something else is wrong, is not normal.

If you're running some other type of battery perhaps someone else can comment on what's normal, i.e. gel cells.

Link McGarity
RV6/N42GF/flying, for sale
RV10/N41GF rsvd/ tailcone
 
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Lead Acid battery voltage

The other thing that hasn't been mentioned is that a fully charged lead acid battery will read 13.8 volt's or so. I'm not sure of the term but it may be referred to as "surface charge" . Any way there isn't much amperage involved in knocking off this surface charge. So yes a 1 volt drop after starting with a fully charged battery is indeed normal.
 
Powersonic sealed batteries

Mel what model number are you using in your 6 ?
I have waited till the last to order , whats the best ?


Danny..
 
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