RPM's needed to charge a battery?

Hello again.

Thanks to everyone for their input on what kind of battery they like. I appreciate it.

My next question is how high an RPM does a machine need to run at and for how long to give the battery a decent charge from the alternator or generator or whatever does that? I do not know the difference between those two so if you can explain it to me I would appreciate that also.

Here is a little background information. I am building a pole barn, and my wheel loader is very handy for installing soffit or whatever. I like having that 7 foot long flat surface to work off vs. a ladder. But I have to constantly move the loader as I move around the building. I had my batteries go dead a couple times, (I also used the loader to get the 30 foot metal pieces up on the roof) so I have left the machine idle lately, but if it just idles I don't know if that is any better as far wearing down the batteries since I don't really work the machine much past idle. I don't start the machine as often so that is obviously a benefit.

Any help on this topic is appreciated.

Thanks.

I had the same problems with a couple tractors not charging and then I figured out that I was not reving the engine high enough to excite the alt on one tractor and the gen on the other now after warming the engines I rev them up high to excite them and both seem to charge but every time I shut them off I have to rev them back up high to get them to start charging again
John

Every situation can be different, you need to install a voltmeter so you can tell what's happening.

Too many variables left unanswered. Engine speed, belting linkage betwren engine and generating apparatus.. Kind of generating apparatus...

Best bet is to get an ammeter between generator and battery to find whether you are getting sufficient current to charge battery.

Your 840 will have an alternator.

An alternator will charge at lower speed than a generator, but still it has it's limits. Also depends on the size of the pulley. Some have a large pulley, they require a little faster engine speed to make full power. They also need to be revved quite high to get the initial charge going, then can be slowed and still charge.

I would recommend watching your gauge/light/voltmeter, whatever it has to indicate charge. You'll learn it's normal operating characteristics, it will become second nature to you to glance at it to see if it's charging. Also try running the engine a little faster. The extra fuel consumption will be minimal. It is also easier on an engine to have the RPM up a little, they oil better, build less carbon deposits.

Finally, avoid stopping and restarting as much. Restarting takes a toll on the starter and flywheel gear. Starters are expensive! Lets not even think of what it involves to change the flywheel gear!!!

No matter how well the charging system works, it's a matter of letting it run long enough between restarts to put more in the battery than the starter just took out. Restarting instantly takes power from the battery. Replacing the power is a gradual process.

Hope this helps!

The least expensive way to charge a battery is with a battery charger. Get an automatic one and put it on at night.

From classes I had years ago on charging systems: After initial starting it take running at normal operating engine RPMs about 15 minutes for the system to make up for the drain from starting each time. I've seen people with new cars that drove them less than a mile each way to work. After a couple of months they started having start problems.

So I would guess your problem is you are not running it long enough between starts unless the system isn't working.

Rick

As others have said watch and see when it charges. We have a forklift we use the same way and it does not charge until you rev it up pretty good to get the alternator working. When you pay attention it stays charged no problem.