Ended up with a LawnBoy 8481AE Aluminum Deck, Self Propelled, Electric Start

[FuzzyDriver]

Check "Ah"? Is that a typo?

 

[Joe Kuhn]

Check "Ah"? Is that a typo?

Meant to say Amp hours or Amps, whatever. I'm no expert on electricity. I've decided to assume the output from the mower is correct. I've matched the battery closely except for size so will go with it. Saw documentation somewhere that there is output from mower back to battery which I believe is not the case with the Toro electric start I'm also fixing. This LB is working fine so far. I've mowed once and stored it in my shed and it starts up every time I've tested it.

 

[FuzzyDriver]

OK, thanks. I'll try to help with the terminology.

An amp-hour is, as the name implies, an ampere of current flow for an hour. This is a battery rating, since batteries are storage devices, as opposed to a generator, which produces potential power as long as it's being turned (not a storage device). A battery can have a rating like, for instance, 20 Ah which means it would be dead after the amount of current you draw from it times the hours you draw that current equals 20. 20 Amps for 1 hour, 10 Amps for 2 hours, 4 Amps for 5 hours - any combination that multiplies out to 20. As you can see, Amp-hours for a generator doesn't make sense - it can put out 20 Amps (or 10 Amps or 4 Amps) forever as long as you keep turning it.

If I can help with anything else, electricity-wise, let me know. Have a good day!

 

[Joe Kuhn]

.

OK, thanks. I'll try to help with the terminology.

An amp-hour is, as the name implies, an ampere of current flow for an hour. This is a battery rating, since batteries are storage devices, as opposed to a generator, which produces potential power as long as it's being turned (not a storage device). A battery can have a rating like, for instance, 20 Ah which means it would be dead after the amount of current you draw from it times the hours you draw that current equals 20. 20 Amps for 1 hour, 10 Amps for 2 hours, 4 Amps for 5 hours - any combination that multiplies out to 20. As you can see, Amp-hours for a generator doesn't make sense - it can put out 20 Amps (or 10 Amps or 4 Amps) forever as long as you keep turning it.

If I can help with anything else, electricity-wise, let me know. Have a good day!

The volts coming from the generator in this mower is 45 although the battery is 12. Is that a problem? If so, perhaps I need a new generator and perhaps it toasted the original battery.

How do I check the amps coming from the mower generator that will keep my battery charged up? I looked it up, but don't think my meter has a setting for that, or I don't understand how to set it for Amps. Will post picture of my meter if needed.

Thanks

 

[FuzzyDriver]

The alternator on the Lawn-Boy uses the magnet in the flywheel. This means that it is generating a pulse of voltage as the magnet passes next to the alternator, and generates nothing for the rest of the revolution. Your meter, set for DC volts, is designed and calibrated to measure a continuous, steady voltage. This is why the voltage reading specification varies wildly from alternator part number to alternator part number (some are 18 VDC, some are 160 VDC equipped with the same battery!) and why they want you to use their "Lawn-Boy" meter.. So the DC you see shouldn't worry you - long as you got some you should be good.

I doubt if I'd worry about it, but a more reasonable check would be to check the battery voltage before you start, run the starter to discharge the battery some, and then check it again after you're done mowing. The voltage should be lower after you run the starter and higher after you're done mowing (probably near the pre-start voltage)..

 

[bertsmobile1]

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The volts coming from the generator in this mower is 45 although the battery is 12. Is that a problem? If so, perhaps I need a new generator and perhaps it toasted the original battery.

How do I check the amps coming from the mower generator that will keep my battery charged up? I looked it up, but don't think my meter has a setting for that, or I don't understand how to set it for Amps. Will post picture of my meter if needed.

Thanks

Generally you would use a 1Ω resistor connected to the battery and measure the voltage drop between each end ( called a shunt resistor & available from any electronics store )
Most of the mower engine companies also sell them as a service tool .
You can buy a cheap motorcycle amp meter and hook it up to one side of the battery .

However to do it properly you need some very expensive testing gear because you are trying to read a pulsed output which goes from 0 to a peak voltage then back to 0 then to a negative peak voltage then back to 0 V again

 

[FuzzyDriver]

Bert: The alternator current has to be going through a rectifier (probably full-wave) or it wouldn't charge the battery since the negative pulse would counter the positive one.

John, As Bert said, due to the simplistic design (~3000 Hz pulse) it's not practical at all to measure with equipment you have around. Besides the shunt (the current is so low I'd use a 10 Ohm, BTW), you'd need an oscilloscope and a calculator/differential calculus. It's just not worth messing with at all. If your battery isn't getting kept charged, put it on a cheap 12V trickle charger once in a while. BTW, the early electric start Lawn-Boys didn't have an alternator, they came with a trickle charger for when the battery got too low, heh heh.

 

[bertsmobile1]

Fuzzy,
I know how they work , I was just trying to explain why he was getting silly readings.
Lots of mowers only use a 1/2 wave rectifier with no regulation so you can get really weird readings with cheap meters.
I am always dissapointed with how bad the knowledge of simple electrical principles is throughout the entire population

 

[FuzzyDriver]

"I am always dissapointed with how bad the knowledge of simple electrical principles is throughout the entire population"

Couldn't agree with you more.

 

[Joe Kuhn]

Now I feel bad for asking...