I have a 2005 Rubicon that has a dead battery. I have tried charging it and it will not hold a charge at all. Since the battery is dead, the starter does not work either. I have just been pull starting it until I get a new battery. Since I am running it with a dead battery, could I cause damage to the alternator, or what ever it is called that keeps the battery charged, and eventually that will have to be replaced? I thought maybe the alternator was constantly running trying to charge the battery and cause it to go out quicker.

I did some pricing for the alternator just out of curiosity and that could get expensive really quick. Three of the pieces were in the hundreds of dollars.

 

I doubt it would damage the charging system, but if the battery has a dead short the alternator will be putting out full power all the time.

If it were mine, I'd just go snag a good AGM type battery. I assume you are planning on replacing it at some point, so I'd say just do it now. It only takes a few minutes.

 

I do plan on replacing the battery pretty soon. What is a AGM type battery and where do you get them? I just figured on buying a Honda battery since I can get a discount on them.

 

AGM is absorbed glass mat, where the electrolyte is absorbed in a matting material.

They generally last twice as long as a traditional lead-acid type battery, can be mounted in any position, resist freezing and vibration better, they don't require service (adding water), and don't spill if tipped over or even broken. They also take the same charging voltage as a lead acid and charge rapidly, where gel cell batteries generally charge at a higher voltage.

The factory Honda battery is an AGM type.

Yuasa also makes high quality (AGM) atv batteries. I believe they are the supplier for several brands.

Mainly by recommending an AGM, I meant don't go out and buy the dirt cheap lead acid battery from a big box discount place. They just don't hold up as well as a sealed AGM.

 

I do plan on buying a Honda battery. I did not realize they were the AGM type. I can't believe the battery lasted this long. We shut it on and off quite a bit. I would imagine if I bought a battery from Walmart, it wouldn't last 2 years.

I'm not sure if the battery is bad. I checked the volts and it showed a consistent 12.4 volts with the atv off. With it running, it showed 14.5 volts. I have not load tested it yet or let it sit over night and then check it. If I do a load test, what should the voltage read? If I pull the rope and hold the starter button at the same time, it will start but it sounds really weak.

Thanks for your help.

 

I would expect 13 to 13.2 at full charge. If you leave it on a battery tender for a day, unhook it and let it sit for an hour, will it get any higher than 12.4?

Two other quick tests I would run: Take a voltage reading from the battery while attempting to crank the ATV. I would expect the voltage to drop quite a bit. If not, I'd be looking for corroded cables, or possibly brushes worn in the starter not making good contact.

Also, pull the negative cable, and with the key off take an amp meter reading between the neg cable and the neg post of the battery. A couple miliamps would be normal. Start with the meter on the 10a range, so you don't mess up the meter if there is really heavy draw. If the reading is more than a few miliamps, something is causing excessive battery draw. If that is the case, I'd first look at any after market accessories, and if that isn't it disconnect the voltage regulator/rectifier and retest.

The factory battery is around 18 amp hours. I'm not sure what kind of amps it should give under load test.

My guess is that it is the battery, however. It is 5 or 6 years old, and they live a hard life on ATV's.