"Guv Bob" wrote in message m...
"mike" wrote in message ...
Guv Bob wrote:
Many thanks fellers for the lessons on batteries! I am now 3-5 times smarter than I wuz (about batteries)! Which ain't saying that much according to the lovely wife. LOL!!! Really appreciate pointing me to the less expensive sources and alternatives too.

Bob


"Guv Bob" wrote in message news Got a dumb question.... I have an electric mower that uses two 12V lead acid batteries wired in series to give 24V. The batteries are marked 18Ah. Cost is around $100 for one 12v, or $140 for 2 in series, including shipping.

For the same money or less, I can get two std 12v car batteries and end up with more amp hours to boot, which would be good for a mower. Heavier to push around, but that's not a problem.

I don't know nuthin about how amp-hours work - reckon this would be a good idea? Anyone had experience with this kind of thing before?

Bob

It's more complicated than that.
Let's do some math...
There's lots of marketing hype and specsmanship involved. Let's ignore
all that for now
and just look at round numbers.

If your typical gas lawnmower is 3Horsepower, it takes 2250 watts/24 =
94 AMPS to equal it in an electric mower...again, ignoring possibly
significant
losses that make the numbers much worse.

Mowing short grass probably requires much less than the 3HP number,
so measuring under load would be good.

You can probably buy a cheap 18AH battery that can put out 0.9Amps for
20 hours...for a few cycles anyway.
Even the BEST battery can't put out 18A for an hour. Google will give you
lots of info on that relationship.
The cheap battery really shows its cheapness
at high current loads.

And, as mentioned, don't consider anything BUT a deep discharge design.
It's quite possible to build a proper lead-acid battery charger. But that
doesn't mean that the one that came with the mower is a proper design.
An excellent battery with poor maintenance and poor charge control
won't have a long life.

So, if you have a small yard and you mow short grass and you charge it
after every mow, and before, if it's been a while, and periodically
over the winter and you don't "I hear it slowing down, but I just have
100 more feet to go", run it into deep discharge, it might be worth the
cost of batteries.

And don't forget they're running the crap out of that small motor.
My electric edger gets so hot that it melts the plastic brush holders.
I fixed it three times before it had to be discarded.


For most of us, a used gas mower would be a better use of the funds.
That assertion is supported by the high percentage of electric mowers
found at garage sales.

Thanks for the info. I've got about 3000 sq ft to mow and my electric does it all once and sometimes twice before starting to slow down. And I don't cut it often enough - gets a good 2-3 inches longer than it should sometimes, and plenty of crab grass to cut thru.

I think I found out the real problem in my case. Starting it on days below 70 deg F it runs very slow for the first 10 minutes and then runs fine. On warm days, the motor runs fine right off the bat. Probably because recently I dripped motor oil to run down along motor shaft. Should not have done that.

This mower is from a garage sale bought about 10 years ago. I put a new battery in it then and still seems to be OK on a full charge. No plans to switch back to gasoline for me. No smoke, no gas fumes, no oil, no cleanup spills and no danger of leaking and causing a fire in storage.

I see where they have 36V mowers now that are self-propelled. Fairly expensive, but sometimes the local air pollution district has a 'trade in' program that gives you $100-200 off coupons for trading in a gas mower.



Found the problem... batteries were nearly dead. Replaced the two 12V batteries and it runs better'n new. Nothing wrong with motor, etc. For anyone interested, I got them on ebay. Don't remember the company but they had 100% positive feedback were around $65 total for the two, including shipping.