[modeleng] Re: Topsy - to charge and how to charge, that is the question!

On Wed, 30 Mar 2005, John Rippengal wrote:

> Peter Sheppard,
> Whoops! I have just re-read your original posts and note that the engine is
> only 3/4 hp. That is only equivalent to about 20 amps from the 24v
> alternator max even ignoring lots of losses. So you will need a more
> sophisticated control system than I have suggested. Basically you will be
> running on the battery.Main charging must be after use because the engine
> can only supply a fraction of the 96amps your motor will take on max power.
> John

Assume batteries are 12v 50amp-hour - joined in parallel to give a 24V
50amp-hour unit.

Assume that average current is actually 50 amps (any higher and the loco
will struggle to get its load moving with a 96amp maximum).

Corresponds to 1 hour continuous running.

Assume that loco runs for 50% of the time and is stationary for 50% of the
time (charging in the station).

Without the charging kit, you could get two hours worth of use from it.

With the charging kit, giving 20amps for 50% of the time, you would get
20amp-hours back during the two hours, which is getting close to halving
the current drain on the batteries.

Result - with the charging kit, the loco should run for nearer four hours
than two and sound more like a real loco!

Sounds workable (although the same running duration could be acheived a
lot more simply with two sets of batteries).

Yours,


Rich.
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