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Battery Question


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My bike is a '04 RT with original gel battery. When the bike is not in use it is always on the (BMW) charger. The indicator lights show storage, which is a full charge. After returning from a 100+ mile ride I plug it back into the charger and the charger light is flashing which indidcate the charge is above 80% but not a full charge. It charges for a couple hours before reaching the storage level again. Is it normal for a fully charged battery to discharge while riding the bike? It would seem at some point the battery could go dead at this rate. I am just wondering if it is time to replace. Thanks.



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Mine is exactly the same, even after a 500 mile day. It seems that the alternator does not top off that last few percent.

The gel battery charger does. Recently I put a meter to the battery after returning from an all day ride. It measured 13 volts. Your battery is not discharging while you are riding.

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Your battery may well read fully charged as to volts and be basically shot also. I recently was experiencing difficulties again with setting the ABS when I started the bike. I checked voltage 13.something. Put it on the charger overnight anyway and all green lights ready to go according to the charger by the morning. Had same problem when I started with ABS not setting. Got out my voltmeter and hooked to the power take off on the dash and watched while I started the bike. Voltage dropped to 6.2 volts as I started the bike. That is a sign of a battery that can't handle the load. Went to American Battery where I live and had them order a gel cell for me. $50.00 later and I am experiencing 9+ volts when I start the bike and the ABS sets perfectly. Also runs smoother at idle. Seems I was likely getting weak spark at low rpms. By the way the other battery was a year and a half old BMW gell cell. Go figure!


Anyway, the moral is to take a volt meter and check what the voltage reads when you start the bike. It shouldn't go below 8 to 9 volts. You can easily check by using the voltage take off at the dash. thumbsup.gif

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When the bike is not in use it is always on the (BMW) charger.


If it's ever hot in your garage, I wouldn't do this. That's because a battery's lifetime can be cut in half if trickle-charged 24/7 at temperatures well above room temperature. Thought I'd mention this since you're in AZ.

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Even a weak battery will show 12 volts. A better measure of cranking capacity is amps.


If you use a smart charger like a Battery Tender, the ambient temperature in a garage doesn't matter. I've used a Battery Tender in my garage at temps ranging from sub zero to 95 degrees with no problem.

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