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5 Answers

How to keep battery alive in cold weather

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Aircraft Systems

I have a PA-24 Comanche and I live in Maine. The temps here are often near zero in the winter even if its sunny. I just put a new battery in the plane but the cold weather is too much and I am finding myself hot proping the airplane to start it, which doesn't excite me on an icy ramp. What could I do to keep my battery alive? I have a float charger on it, but it doesn't seem to be cutting it. The battery is in the tail of the plane. 

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5 Answers

  1. Best Answer

    John D. Collins on Jan 03, 2013

    I use a product called Battery Minder. It has a temperature probe and adjusts the voltage for temperature although I don’t see your kind of cold temperatures very often. See http://www.aircraftspruce.com/catalog/elpages/batteryminder11-02006.php

    In addition to the battery, I assume you are using pre-heat or an engine heater. Since your battery is located in the rear of the aircraft, it has a long cable run to the starter solenoid. Any corrosion in the connections or the airframe ground, both at the battery end and the starter end will mean that you don’t deliver full cranking power to the starter. You might talk to your IA and consider if it is feasible to replace the battery cable with a lower gage conductor.

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  2. Bob Watson on Jan 03, 2013

    They make a battery warming wraps for cars that go around the battery. They are basically an electric blanket for the battery. You plug it in and it warms up the battery. I don’t know if something like that could be used or adapted to your plane’s battery, but they seem to exist. However, most of the places that turned up in a Google search of “battery warming blanket” were out of stock, so winter might be a tough time to find one.

    External power is another option I’ve seen used, but your plane would need an external power receptacle (which is probably more expensive to add, if it doesn’t already have one).

    If all else fails (and, again, I don’t know how practical this idea is for your plane), you can take the battery out and keep it at home where it’s warm, then install it when you get to the airport to go flying. That’s a pain, but it works. Of course, working with the battery bolts in sub-zero temperature isn’t going to be fun.

    In addition to keeping the battery warm, how’s the oil? Do you have an engine or oil heater installed? Cold and thick oil will make it hard on the starting system, even with a good battery. Finally, it could be that your starter needs to be looked at.

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  3. Brian on Jan 03, 2013

    I’d have to agree with John. If you just put in a new battery chances are the battery is not an issue. I flew out of New Hampshire for 5 or so years, we had no issue starting and did not use a battery tender, just a tanis heater.

    I think Johns onto something with the cables. Perhaps see if they can do a continuity check of the cables, starter solenoid, and check to make sure the starters good. If you know the battery isn’t keeping charged, then is it filled? Is this a PA-24 180 or PA-24 400 and is the starter sufficient for that size engine. In other words, not to be redundant, but I’d inspect the other elements in the starting process unless you’ve put a meter on your battery and are certain it’s a battery issue (I suspect it isn’t).

    Bob, most airplane batteries, unlike car batteries today, are acid filled and not sealed batteries. If the highly flammable acid gases are not sealed in tight and if that blank shorts…well let’s just say it might be worth doing some investigation before putting one on an unsealed battery.

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  4. Sam Dawson on Jan 04, 2013

    A few things to add to this discussion.
    Most battery manufacturers recommend using the battery for start in cold weather as it helps warm up the battery and have a blurb that states if the battery is not used for start it may not be sufficiently charged for emergency operations.
    A discharged battery that can not start an engine may not be airworthy. For example, from the Gill Dry-Charge Maintenance Manual:
    7.11.1 Teledyne Gill batteries that have been discharged to the point where their cranking power has been diminished must NOT be jumped with another power source.

    The discharged battery may not be airworthy because it does not have the necessary capacity required to operate the aircraft avionics and electrical system in the event of generator failure.”

    In many cases an airplane is not considered airworthy with an inoperative battery. For example, in post 1977 Cessna 172s the battery is listed as a -R item in the equipment list. A -R item is required for the airplane to be airworthy and, IAW 91.213 must be operational. In Bonanzas the battery is listed in the KOL for day VFR- so again, must be installed AND operational. So in these cases it could be argued that if you need a jump start the battery is not operational and you are therefore flying an airplane that is not airworthy.

    More importantly you may be putting yourself at risk in some situations if you fly with a depleted battery. Many aircraft generators/alternators are not self exciting- meaning you need battery power in order for the electrical system to work properly.
    An example of a bad situation. You are flying a retractable gear airplane into IMC. You need a jump start- your battery is depleted. After take off you punch into IMC, then retract the gear. The gear is electrically driven. As you raise the gear this puts a load on the electrical system, your battery is so depleted that your non-self exciting alternator kicks off line and you now have no electrical power at all. No battery, no alternator.
    Something even worse happened to a DA-42 Twin Star in Germany. The Thielert engines (one of the most horrible engines I have ever flown), was certified with a DEC (digital electronic control), but no back up power unit. In other words, no electrical power, no engine power. Diamond had a procedure in their POH that if you did a start on one engine with ground power the other engine had to be started using battery power. The pilots did not follow this procedure. After take off when they raised the gear it put a momentary electrical load on the system that the flat battery could not carry. The alternators kicked off line. The DECs could not handle this and shut down/feathered both engines. Fortunately the pilots were able to dead stick into an open field.

    Finally getting a jump start may hide a more serious problem. I did this once in a 310 thinking I had a battery issue. Instead I had a voltage regulator issue. The voltage regulator melted and I had a total electrical failure.

    I am not suggesting that the OP did anything illegal or unsafe. Just putting some food for thought out there. Read the operator manual for your battery. It probably recommends using a battery minder below a certain temperature.

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  5. Josh on Feb 03, 2013

    So I thought I would give feedback, and I thank all of you for your advice. It turned out, that although the connections on the battery were in good shape, that the connections to the solenoid on the front of the wire wall and the engine grounding wire were both a bit oxidized. I cleaned them up with a wire brush and changed out the old washers with shiny new ones and she started right up (after an engine pre-heat) in 20 below zero temps. The power cables were aluminum, however, they were in good shape and just a few years old.

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