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Topic: Boondocking using HEATING PAD

Posted By: Just Lee on 01/08/14 10:56am

I'm just not good at figuring this stuff out and I am to Old to start now so I am asking you...... LoL

I have 2 12volt Deep Cycle Batteries with the following according to the NAPA Web Site... Batteries are Napa part # 8240

Attributes:
Battery BCI # : 24DCM
Battery Cold Cranking Amps @ 0 Degrees F : 550
Battery Cranking Amps @ 32 Degrees F : 685
Battery Load Test Amps : 275

I have a 1000 watt inverter....

According to the sticker on the HEATING PAD it says;

Rated 70 Watts Max.

My questions is will this setup last me all night?......

Do you need any more information?

Thanks Lee


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Posted By: HappyKayakers on 01/08/14 11:14am

I'm not even going to attempt the math but I would imagine someone will need to know what setting you plan on using on the heating pad. The one I use has 4 different settings.

If you're just trying to stay warm at night (as opposed to treating an injury), invest in a mummy bag and mummy liner.


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Posted By: pdogg on 01/08/14 11:30am

For starters, your batteries are not true deep cycle.. they're hybrid marine cranking batteries..


Posted By: RoyB on 01/08/14 11:41am

Just make sure your INVERTER is the PURE SIGN WAVE type. The MSN INVERTER may cause your heater pad controller go up in BLUE SMOKE...

Your 70WATT Heating pad will draw around 5AMP DC from your two batteries. You need to look up the battery specs and see how long your can safely pull 25AMPS from your two batteries.

A TROJAN 27TMX 85AH 12VDC battery is rated to produce 25AMPS for 175 minutes or 2.9 hours. Two connected in parallel will produce 25AMPS for a good 5.8 hours. Your trailer will also have some parasitic power drains and of course you will be running some 12VDC lights at night. I would be running my HDTV and a few other home entertainment items as well... You really need to find out what is going to be on and add up the power drains.

In addition if you run down your two batteries over night it would be wise to have a way to quickly re-charge them as batteries sitting in a fully discharged state for a long period of time will do internal damage to your batteries requiring replacement.

To be successful you need to do some more planning and possible upgrades to smart mode converter/charger and LED lights etc. You also may need to have a small 2kW Honda type generator to connect your 30AMp SHore Power Cable to and recharge your batteries to their 90% charge state the next morning so you can can use them again the next night etc... If you have smart mode charging technology you can re-charge your two batteries in a short three hour generator run time. I do this at 8AM each morning during breakfast and this is when I make my coffee for the day when the generator is running...

I was never lucky just going to the woods and turn on things without planning and perhaps a couple of trail runs in my back yard. It always got dark on me around 10PM...

Roy Ken


My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
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Posted By: Tiger4x4RV on 01/08/14 12:08pm

You might go the old-fashioned route: hot water bottle. Or maybe those hot-or-cold gel pads you can buy at the drug store. I've used a flexible flask with warm water in it; never had it leak.

You can also get chemical "hand warmers" at sporting goods stores. Put one inside a sock (not while you are wearing the sock) so it cannot come in contact with skin and use it like a hot water bottle.


2006 Tiger CX 4x4, 8.1 L gas V-8, Allison 6-speed



Posted By: MEXICOWANDERER on 01/08/14 12:13pm

X2 Roy Ken. It is VITAL that your inverter be PSW PURE SINE WAVE. A MSW modified sine wave inverter will fail the control module of your heating pad almost instantly.

Your heating pad would (most probably) not stay on 100% of the time. However with losses in the system pretty much count on a 9-10 amp draw. Twelve hours of operation will FULLY DEPLETE (to 50% remaining capacity) a pair of group 24 cyclable batteries if the pad duty cycle is 100% I've never seen an inverter gobble less than 2 amps vigorish.

Sigh. A propane powered heating pad. Sigh.


Posted By: MrWizard on 01/08/14 01:05pm

We use a go power 300w pure sine wave to power a heat pad
IIRC Idle no load power for the GP is 0.600 amps yes 600 milliamps

Any way 25 amps ...has NOTHING to do with it
5~6 amps plus 10% inverter conversion loss, figure 8 amps load at max heat for whatever hours you use it. 6 hours at 8 amps = 48 amp hrs or about 30% of your bank
To stay above 50% discharge, you will need to recharge your batteries everyday

If your heat pad is old and has the manual three position selector resistive style switch, you can use a MSW inverter if it's new with digital control then you need PSW inverter


I can explain it to you.
But I Can Not understand it for you !

....

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Posted By: MEXICOWANDERER on 01/08/14 01:17pm

WAIT! Let me explain my "error"! I forgot! Some inverters have a SEARCH MODE. BUT BUT BUT, load your inverter with a 70 watt load. You are saying your inverter has a greater than 90% efficiency with a 70 watt load?

OK I'll bite...

70 watts at 12.5 volts is 5.6 amperes

The moment your inverter goes off of SEARCH MODE and into power mode, say with a 10 watt load, what is the battery DC burden then?

At 70 watts A.C. load what is the exact D.C. burden on the batteries. As measured with an accurate ammeter?


Posted By: kneal44 on 01/08/14 01:27pm

I have seen advertised in truck stops a dc plug in electric blanket... says good all night with out draining battery. for $40. look on ebay .
sleeping you only need just a little heat to keep warm. you never wanna run your batteries dead.
once i used the propane heat and ran out of power... by morning not enough juice to start generator... had to start main engine and then start genny.
could have been a real problem if dident have separate start batteries.
propane furnact takes lots of power over night...


when u play in the sand .... you can get stuck

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Posted By: RoyB on 01/08/14 01:29pm

Wizard - We are saying the same thing - just your way of saying it makes better sense...

25AMPs x 2.9hours = 72.5AHs Thats pretty close to the 85AHs rating for the battery mentioned... This much current drain however would drop the 85AH battery to 0% state of charge which you don't want to do.. Adding up all the current drains times the hours of use is really a better way to look at it...

If the total amps added up to 25AMPS then it would only be 2.9 hours of use before dropping the battery to 0% state of charge...

since I measure my actual current draw at my Battery Monitor Panel in AMPS all the time its easy for me to see how much current is being drawn...

just saying...
Roy Ken


Posted By: RoyB on 01/08/14 01:39pm

MEX - I was holding the 120VAC Electric Blanket plug in my hand one time and was fix en to plug it into the MSW Inverter I had then. The electric blanket controller died of fright before I plugged it in and started pushing out blue smoke... hehe I guess it knew what was going to happen...

Roy Ken


Posted By: Handbasket on 01/08/14 02:09pm

I've always been of the (fairly strong) opinion that in most cases if I can find something for the RV that runs off of 12V directly instead of going thru an inverter, I'm better off. If the 12V electric blanket will do the job, it's prob'ly your best option. Maybe do a little research on truckers' forums before buying.

Jim, "Democracy: your vote counts. Feudalism: your Count votes."


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Posted By: doughere on 01/08/14 02:11pm

You don't have real deep cycle batteries.

2 charged #24 batteries would be enough to run your blanket through a night: IF you get a small true sine wave inverter in the 150 watt range.

The 70 watt blanket would at most use about 60 AH which your batteries would easily be able to supply.

You need to do a lot more research on what you need. One night's not a problem, its what you plan to do in a longer term. A 1000 watt gen would be enough to recharge daily, but the batteries you have are not correct for this type of service. If you only plan to do this a dozen times a year, you're OK, if you plan to do often, you need to do a full assessment of your power needs.

Regards,
Doug


Posted By: MrWizard on 01/08/14 02:12pm

i never have a 10 watt load
even turning on the kitchen CFL ligts is 18w
the main load for the go power is the laptop with external drives
of course the TV and DVD are on the same power strip and in standby mode, i never have tested it with a 10watt incandescent resistive load

our trip-lite PV1250 has adjustable load sense and only power the fridge and also draws less than 1 amp, on standby, 2 amps no loss idle if I turn off the loss sense , even the fridge light bulb will not turn it on
when we open the door the light blinks on and off unless the fridge compressor is running

I think PT & BFL have done extensive go power load testing

MEXICOWANDERER wrote:

WAIT! Let me explain my "error"! I forgot! Some inverters have a SEARCH MODE. BUT BUT BUT, load your inverter with a 70 watt load. You are saying your inverter has a greater than 90% efficiency with a 70 watt load?

OK I'll bite...

70 watts at 12.5 volts is 5.6 amperes

The moment your inverter goes off of SEARCH MODE and into power mode, say with a 10 watt load, what is the battery DC burden then?

At 70 watts A.C. load what is the exact D.C. burden on the batteries. As measured with an accurate ammeter?


* This post was edited 01/08/14 07:42pm by MrWizard *


Posted By: MEXICOWANDERER on 01/08/14 02:27pm

What I was referring to is "Is's and "Ought To Be's"

When my Trace is on search mode, it takes .045 ampere. The instant it turns "On" that .045 ampere increases to 2 amperes. A 70 watt load doesn't suck 70 watts from the batteries, no, the inverter is not 90% efficient at that load. It is more like 80% efficient. So a true 70 watt load needs 20% added to it 84 watts plus 2 amps (call it 25 watts) to make the inverter more happy. Ah heck, call it 110 watts total. Twelve hours of heating pad at 110 watts is nothing to sneeze at.


Posted By: MrWizard on 01/08/14 04:45pm

Mexi
what you say is true..
notice i said call it 8amps battery load not 5.6
and 6 hrs load/sleep cycle, not 12 hrs

96w per hr, for 6 hrs

* This post was edited 01/08/14 07:46pm by MrWizard *


Posted By: Just Lee on 01/08/14 06:09pm

Oh boy I think..... I am more confused now then I was....

Thanks for trying to explain... All I really wanted was a Yes or No.

But I can see there is much more to it them meets the eye....

So I guess I'll just plug it in and see what happens..


Posted By: mena661 on 01/08/14 06:54pm

Just Lee wrote:


So I guess I'll just plug it in and see what happens..
We nerds get carried away sometimes. [emoticon] Let me simplify it.

1. Is your inverter pure sine wave (PSW) or modified sine wave (MSW)?
2. Does your blanket have digital controls?

We'll move on once those are answered.


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Trojan L16 6V's 740 Amp-hours



Posted By: MrWizard on 01/08/14 07:48pm

Just Lee

Your two batteries should carry thru the first night

But you need to recharge the batteries before doing a second night

Each night you use the heat pad, recharge batteries next day


Posted By: SCVJeff on 01/08/14 09:06pm

I used to have a 3 position heating pad until it got plugged into an MSW inverter and all the smoke leaked out.

I tried to blow smoke up.... Wait, that was something else... [emoticon]
Anyway, I don't think a mechanical switch is a guarantee that its MSW safe, so be careful and pay attention to your nose for the 1st 30 mins just to make sure.


Jeff - WA6EQU
'06 Itasca Meridian 34H, CAT C7/350



Posted By: ICamel on 01/08/14 10:38pm

One other thing that has not been mentioned. I have two pure sine wave inverters. Both have a function that will sound an alarm and then auto shut off when the inverter senses the battery charge to be 50% of maximum.


ICamel

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Posted By: Just Lee on 01/09/14 08:40am

mena661 wrote:

We nerds get carried away sometimes. [emoticon] Let me simplify it.

1. Is your inverter pure sine wave (PSW) or modified sine wave (MSW)?
2. Does your blanket have digital controls?

We'll move on once those are answered.


I have a Xantrex 1000 watt MSW Inverter and
To me YES it looks like my electric PAD is digital by that I mean you push the button to increase the heat (it is NOT a SLIDE dial)I tried to Google the Pad and didn't get anything..

Hope this helps

Yes I know I will have to run the generator EVERY day to re-charge the batteries.....

Thanks for simplifying this......

Lee


Posted By: mena661 on 01/09/14 09:37am

Ok, since you have digital controls and a MSW inverter, it would not be a good idea to run the blanket from your inverter. MSW typically will smoke digital controls. If you really want to do this you can buy a PSW inverter just to run the blanket.

Size of the inverter depends on how much power the blanket draws in watts. You can find that out by getting a Kill A Watt meter and plugging your blanket into that.

Kill A Watt Meter Clicky


Posted By: Just Lee on 01/09/14 09:45am

Ah ok thanks.. I do have a Heating Pad in the house that has dial controls (almost like a dimmer switch) would that one work the MSW inverter?

I also have a inverter that plugs into the cigarette lighter. It is 200watt.... Not sure what it is MSW or the other one....

Gotta leave in a few I'll chaek back later

Thanks


Posted By: dclark1946 on 01/11/14 05:53am

Once you have your inverter/heating pad issue worked out you may want to change your batteries to something with more capacity. If you want to stay 12V you should be able to go with a pair of Gr 27 like a Trojan SCS 200 battery with 115AH per battery. You will still need to run the generator every day but these batteries will provide more reserve capacity.

Dick


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Posted By: mena661 on 01/11/14 12:53pm

If the inverter with the cig plug was really cheap, it most likely is a MSW. Most PSW inverters will say pure sine wave somewhere on the unit. I believe the dimmer switch heating pads are MSW friendly.


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