Battery Tender question

 
Any disadvantage to putting the battery tender on a timer and running it
only a few hours at night during winter storage (in a semi-heated
garage) instead of running it 24/7?  I'm just trying to cut down on my
electric bill, but don't want to lessen the life of the battery.  How
about 6 hours on, 6 hours off?  Thanks in advance!

--
Kendall F. Stratton III
Fort Fairfield, Maine USA
k3(86_the_Spam)@maine.rr.com
http://www.facebook.com/K3Stratton

 
Probably wouldn't make a whole lot of difference in the
electric bill, but sounds doable. You might run it full time
for a day or so before you put it on a timer.

Charging at full capacity, you're drawing perhaps 15 watts,
(12V x 1.25A). This works out to ~10 KWH/month. a 6/6
schedule might give you a grand savings of $1/month.
Probably less.

Unsure how that compares to the KWH required to run the
timer.

 K3 wrote:

If your bike has an alarm on it, maybe you need to leave it hooked to a
battery tender.  Otherwise, plugging the tender in once every other
week for a couple of hours will be plenty to top up the small amount of
self-discharge.  Or you could just leave it alone and not worry about
it.  If your tender is any good it probably uses less power than a
night-light bulb once the battery is topped up.

If your battery is the sealed type, you could charge it up and store it
in your freezer all winter, and in the spring it would still have more
than 90% of a full charge. Cold is good for *charged* batteries, the
colder it is, the less the battery self-discharges.  Storing batteries
in warm places actually makes the battery self-discharge much quicker.

 wrote:


That's very interesting.

I used to leave my 4 boat batteries in all winter (Northern Ohio) and
never had a lick of trouble.

 

One other poster cited 15W as the likely draw.

Residential electric rates (as of years ago were around 11 cents per
KWH).  Let's adjust for inflation and say 15 cents per KWH.

(0.015 KW)(365 days/year)(24 hours/day) = 131.4 KWH.

At $0.15/KWH, that is $19.71 for the whole year, or maybe $1.60 per
month.

Unless I made a calculation screwup, that isn't a large contributor to
your electric bill.

I don't see a problem with a timer approach.

A simpler approach might just be to get a less powerful battery tender
(essentially a wall wart).

Probably the most power-conserving approach is to get a low-capacity
wall wart above the voltage you're interested in (maybe 15V), then
dope it down using a resistor and several forward-biased diodes.  The
resistor will limit the current, and the diodes would let you get the
Thevenin output voltage down to the battery voltage.

DFC