Hi,
Alternators like to be spun fast. Max rpm 10K but 6Krpm is a good place
to operate. It is easy to damage pb-acid batteries while charging.
See
https://www.solar-electric.com/lib/wind-sun/Iota-charging-deep-cycle-batteries.pdf
There are better guides on the web but this is the first one that came up.
In summary bulk charge to about 25% of total capacity. Absorbtion charge
up to the recommended voltage then float charge.
One can fast charge a battery but the chances of damage increase. I
think the 10 A rate of most 12 chargers is reasonable.
A serious web search should give better figures. To charge at high rates
is going to take a very large battery. ;-)
I suspect that charging batteries in series will help level out the
charge when charging multiple batteries. Of course that takes a different
alternator. ;-( As always YMMV
Good luck.
Dave
On 7/9/21 9:46 AM, fxkl47BF via Emc-users wrote:
On Sunday, June 27th, 2021 at 6:41 AM, fxkl47BF <fxkl4...@protonmail.com> wrote:
i'm gonna explain my screwup here because this group of folks has a very
diverse range of expertise. enough kiss'n up. if you know of a list that would
be more appropriate please let me know.
i've had a desire for some time to build a gasoline powered battery charger.
i've seen it done several times and thought no big deal. my first thought was
to use a 3 hp engine and a 100 amp one wire alternator. but since i already had
a 6.5 hp engine i decided to go with that and an alternator like this
https://www.ebay.com/itm/NEW-CS130-ONE-WIRE-RED-ALTERNATOR-FOR-CHEVROLET-GMC-CHEVY-220-AMP-1-WIRE-1100665-/283190864732?hash=item41ef7dab5c.
i also added an ammeter like this
https://www.ebay.com/itm/301111474999?hash=item461ba47b37:g:hYUAAOxy4fVTEuR6.
i finished it and was ready to test. i pulled a big battery out of my tractor,
connected a 1000 watt inverter, and about an 800 watt load. i cranked the
engine and connected it to the battery. ammeter showed about a 7 amp load. i
switched on the inverter and it went to about 9 amps. i switched on the load
and it went to about 75 amps. the engine was straining. i disconnected the the
alternator from the battery so the load could draw down the battery. after
about one minute i reconnected the alternator. the ammeter jumped to about 110
amps and it promptly stalled the engine. i tried several times with the same
results.
all of my feeble calculations led me to believe that a 6.5 hp gasoline engine
was more than enough to power a 220 amp 12 volt alternator. either my 6.5 hp
engine is more feeble than my brain or my calculations are way off.
thanks for any feedback.
i've been do'n a little piddle'n on this when life didn't get in the way.
i took all of the feedback from y'all and it sounded like less would be better
so where my sheaves were originally a 2:1 increase now i have a 1:1. i tried
slower, .7:1 decrease but it was too slow. the alternator would barely make 13
volts. to get a little more info i bought one of those point and shoot
tachometers. it says this engine runs at 3200 rpm with no load. with a 1:1
ratio i drained down my battery and with a 800 watt load the alternator made
120 amps at 14.3 volts for 20 to 30 seconds before the amps dropped. the tach
showed it turning at 3100 rpm. i think to get 220 amps i would need a 10 or 12
hp engine and turn this thing at 10000 rpm. of course it would melt down after
about 1 minute.
i appreciate all the feedback.
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