An electrical question.

[MasterGuns]

How long can I expect to power a pair of heated socks that draw 9 watts each sock from a 10.5 AH rechargeable deep cycle battery? Here is how I figured this out and if I am out in left field please correct me.

 

10.5 Amp hours is 10,500 mah

 

18 watts at 12.8 volts is 230.4 mA

 

The battery can safely discharge 80% of its charge or 8400 mah

 

8400 divided by 230.4 is 36 hours.

 

Am I correct or I am screwed up?

[dingy]

How long can I expect to power a pair of heated socks that draw 9 watts each sock from a 10.5 AH rechargeable deep cycle battery? Here is how I figured this out and if I am out in left field please correct me.

 

10.5 Amp hours is 10,500 mah

 

18 watts at 12.8 volts is 230.4 mA

 

The battery can safely discharge 80% of its charge or 8400 mah

 

8400 divided by 230.4 is 36 hours.

 

Am I correct or I am screwed up?

 

If it is a deep cycle battery, I would think 80% is pretty conservative on draw down.

 

Gary

[MikeWa]

4 to 5 hours.

 

Mike

[dingy]

If it is a deep cycle battery, I would think 80% is pretty conservative on draw down.

 

Gary

 

I was looking at the draw down % backwards. 80% is probably a good number. That would leave 20% remaining in battery.

 

Whoops !!!

 

Gary

[midnightventure]

amps times volts equals watts so watts divided by volts equals amps. That means you will be drawing 1.4 amps.

[Peder_y2k]

Bout 7 hours for a near new battery. Planning to go ice fishing?

You can prolong the energy drawdown by shutting the sox off intermittently, thus letting the battery partially recharge on its own.

-Pete, in Tacoma WA USA

[MikeWa]

Yea my math came out to about 7.5 but things are never ideal. So I would figure about 4.5 to 5 hours if it was mine. Anything beyond that is gravy.

 

Mike

[Guest tx2sturgis]

Your math is off a bit.

 

A lot depends on the battery...amp-hour ratings dont tell the whole story. Is this a Nicad or lead acid type? Or something else?

 

How cold the battery is, will be important also. Colder means less output. Sometimes, MUCH less.

 

It also depends on whether you expect to get much use out of that battery after its been drained a few times.

 

A typical SLA battery in that range, similar to what used to be called 'alarm' batteries, will be lucky to provide a few hours for each full recharge. If there is not a 'watchdog' circuit, and the battery is killed dead even one time...you will probably be tossing it in the garbage. The same can be said for nicad packs. Lithium batteries in that amp range always have some sort of built-in circuit to monitor charge, discharge, and number of cycles.

 

Why not use some of the disposable Hot Hands type heaters? They dont cost much and you can carry a lot of them in the same space, and for the same weight, as a heavy battery.

 

http://stn3.headgap.com/hothands/FMPro?-db=Ordershh.fp3&-format=products.htm&-new

 

Also, scroll to the bottom of this page:

 

http://stn3.headgap.com/hothands/FMPro?-token=12618259&-db=ProductsHH.fp3&-lay=WEB&-format=items.htm&-sortfield=SortID&category=wear&-find

Edited October 24, 2013 by tx2sturgis

[CaptainJoe]

Your math is off a bit.

 

A lot depends on the battery...amp-hour ratings dont tell the whole story. Is this a Nicad or lead acid type? Or something else?

 

How cold the battery is, will be important also. Colder means less output. Sometimes, MUCH less.

 

It also depends on whether you expect to get much use out of that battery after its been drained a few times.

 

A typical SLA battery in that range, similar to what used to be called 'alarm' batteries, will be lucky to provide a few hours for each full recharge. If there is not a 'watchdog' circuit, and the battery is killed dead even one time...you will probably be tossing it in the garbage. The same can be said for nicad packs. Lithium batteries in that amp range always have some sort of built-in circuit to monitor charge, discharge, and number of cycles.

 

Why not use some of the disposable Hot Hands type heaters? They dont cost much and you can carry a lot of them in the same space, and for the same weight, as a heavy battery.

 

http://stn3.headgap.com/hothands/FMPro?-db=Ordershh.fp3&-format=products.htm&-new

 

Also, scroll to the bottom of this page:

 

http://stn3.headgap.com/hothands/FMPro?-token=12618259&-db=ProductsHH.fp3&-lay=WEB&-format=items.htm&-sortfield=SortID&category=wear&-find

 

 

+1

 

They also sell hot hands for your feet that has an adhesive strip that you place on your sock under your toes and ball of foot... Use them all the time...you get about 5-6hr out of a set for about $1

 

I bought a whole box 8yrs ago and only have a couple left. bought it around the beginning of march at wallmart. they were marked down to .25 apiece... and they still work!

Edited October 24, 2013 by CaptainJoe

[MikeWa]

I purchased a pair of battery operated gloves (Gerbings) from Cabelas. They work real well in keeping my hands warm. They claim 2 to 8 hours depending on which of four settings is used. I found they are good for about 4 to 5 hours on the low setting. So a couple of spare lithium ion batteries makes me good for the day.

 

Mike

[djh3]

Looks like one of them math questions from high scool about 2 trais traveling across america at x speed an y z speed who gets where when.

[Huggy]

Looks like one of them math questions from high scool about 2 trais traveling across america at x speed an y z speed who gets where when.

 

Yup. I usually just try it and see how long the battery last!