External battery for heated clothes

 Has anyone tried using an external battery to power heated winter gear?

My bike does not have a very powerful generator/alternator and I am toying with
the idea of using an external battery to power some heated gear
The max amperage of one particular jacket, pants  and gloves combo is
12.6Amp/hrs I am guessing a 2/3 duty cycle on average so that would be 8.4
amp./hrs

One battery  I've looked at (bigger ones start to weigh a lot more)  is a 35 AH,
deep cycle AGM that weighs 26 lbs.
http://www.discountpv.com/batteries/ty-12-35.htm

I interpolate that at this draw rate and 40F temp i have about 21 amps  (looking
at other battery charts)  so that would give me about 2.5 hours..   Using this
size battery as a starting point for the discussion.
Anyone doing something like this?  Feedback?
(A 70amp battery would double this but it is 50lbs and getting a tad heavy. )
Thanks.

Ben

 Ben Kaufman wrote:

AH,

(looking

I think you are way overestimating the duty cycle at 40F.  Also, if you
have a decent windproof insulated suit, a little heat goes a long way.
If you keep your core and your hands warm you probably won't even need
the heated pants.  Adding hand guards to your bars to deflect wind will
reduce the amount of heat loss from your gloves, too.

Are you actually planning on long rides at temps below 40F or are you
going to be commuting?  What bike?

 

with

AH,

(looking

My bike is a ZR-750S (1/4 fairing).  I do a little winter riding on more
temperate days (45F) for fun,  however, as I have gotten older, I seem to  get
the chill a lot easier than I used to. After an hour the cold has begun to
penetrate.    I started putting hand warmers in my gloves a few years ago and
although it does not get amply to the finger tips  (i have to pull over to move
the fingers around to redistribute the heat) , it does feel "delicious."  

At first I was thinking about getting just a vest, which would probably be
within tolerance for my bike's output to warm up the core but  just barely.

I think you are probably correct that I would use a lower duty cycle since I
would continue to wear most of my winter layers.

Ben

 

Ben Kaufman wrote:

AH,

(looking

It might make better sense to look at this in watts.
Figuring 8.4 amps @ 12 volts, about 100 watts draw.
At a guess, a 400 watt alternator could probably drive
this load while a 250 watt alternator would likely let the
battery be slowly discharged.

I run a 30 AH motorcycle battery with a 280 watt alternator
and 35 watt heated grips. This works fine on the highway.
I also run an LED voltage indicator to tell me if I'm badly
discharging the battery while stuck in traffic. A $12
"battery alternator tester" from Kragen will do fine for
this purpose.

The 30AH battery has a footprint that drops into the stock
battery tray. I also discovered by accident that the output
of the alternator was greatly improved by replacement of
the original three wire cable with a new one. Over the
years, a slow corrosion buildup had gradually cut the
charging and a $12 cable made an enormous difference.

I've also seen guys bungee a separate auto battery on
the back of the bike and then recharge it overnight.
I don't think I'd bother with a PV battery unless the
price was competetive.

 On Thu, 13 Nov 2008 10:39:57 -0800 (PST), Rob Kleinschmidt


with

AH,

(looking

The problem with using an auto battery is that they are not designed for deep
discharge and regularly taking them down to say a 50% discharge level will ruin
them in short order.

Ben