+1 on being really hard on the charging system to charge a dead battery , battery tenders wont charge a heavily discharged battery is also corrrect. smaller charger from harbor freight or walmart is always handy to have around anhd a lot less dangerous that jumping a battery ....

 

I've jump or push started many bikes. The fuel injected ones don't push start well because you need a lot of battery to get the ignition and fuel system to fire the bike. When you're stuck miles from home with a dead battery and have a choice of towing it or jumping it, the obvious choice is to jump it. Just remember that you're being really hard on your stator and voltage regulator. When it's sitting in your garage dead, fix the battery and then ride it. Then you aren't screwing up anything else.

 

I wasn't trying to be a d!ck about it. The OP said the ignition was left on and drained a 1 year old battery. If the battery had been around a few years and we didn't know why it was dead, I might be going for the charger. It is a 38 amp charging system on a 19 amp battery protected by a 15 amp fuse. Someone would have to show me how the battery was drawing enough amperage while charging on the bike to damage the system. I have every confidence the system design can handle this scenerio with no damage. Now if he was having to jump his bike everytime he wanted to ride it, yeah that's a bad idea I might buy into the damaging the charging system scenerio. I have jumped late model HDs (not mine) for this exact cause and all was well. My 25 year old, made in the USA battery charger for cars will only put out a max of 10 amps to charge and has been used by everyone in my neighborhood to charge their bike batteries. Again I don't use it as my bike doesn't sit long enough for the battery to drain. I still stand by, jump it and he would be fine in this case.

I am also dead (pun intended) against battery tenders as people tend to get these cheap POSs that just keep charging even when not required, overheating the battery and ruining it as one of the other posters described. I believe if you feel you need a battery tender, just pull the big fuse, let it run its course and charge it properly on a decent battery charger when you are ready to ride.

That's all I got.

 

No harm here. Just a discussion.

Between the voltage regulator and the battery is the 30 amp fuse. The circuit breakers for the ignition, lights and accessories are each 15 amps. The voltage regulator in my bike is rated at 32 amps @ 3600 RPM. I seriously doubt if the charging circuit will throw 32 amps especially with a 30 amp fuse. It's probably nowhere near that since otherwise we'd be in danger of blowing the main fuse all the time.

However, just because the alternator and voltage regulator can put out 30 amps doesn't mean it was designed to have a constant load that high. Kind of like your amplifier or speakers that have a peak load of 1000 watts RMS but a mean of 600. Running the bike with a dead battery puts a whole lot more strain for a longer time than the charging system was designed to do. I've seen quite a few stators that were obviously melted after someone ran around too long with a battery that was at the end of its life.

I just hate to see someone have to buy $150-$200 worth of charging system, plus install, when all they needed to do was charge the battery. Will one time do it? Most definitely not. But each time could be diminishing the overall life of your stator or regulator. So my philosophy is jump it if you have to, charge it when you can.

 

Lot a battery myths here on the forums....I come from the AGM/Gel battery industry and I have posted in numerous threads, just do a search.

You are not going to damage the charging system on the bike by allowing it to recharge a good discharged battery, not sure where that myth came from but it’s certainly not true. Just because the battery may be a 20-30 amp hour reserve capacity does not mean that when it’s discharged that it will use all of the resources available from the charging system. The reason is that the back EMF of the battery will rise as the current goes up, causing the charging system to throttle back on the current that’s being delivered. So in essence, the internal resistance of the battery will dictate the rate of charge.

All that being said, if it were me and the battery were completely discharged, I would attempt to restore it using a good automotive type regulated taper charger. You don’t need some big brute that comes on it’s own cart, but rather something that has say a 4, 6 or 8 amp output. Put it on charge on the bench over night and let it taper down to a trickle.

You can jump start a motorcycle with a car but be sure that the car is NOT running, it does not need to be running and that is how charging systems can be damaged. The greater the battery is discharged, the higher the risk is of damaging the charging system if the car is left running.

As far as the Battery Tender devices, some will charge a completely discharged battery but it depends on the model. If it is a Battery Tender brand or something equivalent, it will do no harm to leave it on the battery when not in use. These were designed for the AGM/Gel technology and they go into float mode when the battery is fully charged, they will NOT over cook the battery. There have been some cheap Chinese versions of these maintenance chargers, I’d be weary, some have been known not to have the necessary circuitry for the different charging algorithms.

You don’t need to keep a maintenance charger on the battery if you ride it frequently enough. But if it’s a late model and sits more than a few weeks then you should definitely use one. The parasitic load on the later bikes will begin to gnaw away at a fully charged battery after a few weeks, once the electrolyte specific gravity starts to drop, then sulfation can start to happen. So if it’s going to sit for any length of time, use a maintenance charger, you will get a lot more life out the battery that way.

Hope this helps….