12v electric blanket?

Submitted: Friday, Jun 02, 2017 at 19:25
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G'day all, I have just purchased a Waeco 12v electric blanket for my partner, what do I need from my solar bank to be able to use it regularly? thanks
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Reply By: Athol W1 - Friday, Jun 02, 2017 at 20:24

Friday, Jun 02, 2017 at 20:24
Ausiedingo

I am not sure what you are asking, as it is highly unlikely that you will be using the blanket whilst the sun is out. But your blanket will use 3.75 amps/hour whilst on high setting (45w divided by 12 volts =3.75a). Multiply the amp/hour use by the number of hours that you intend to use the blanket and this will give you the minimum battery power that you require for the night (remember you should not be using any more than 50% of the available battery power (amp/hours).

As an example if you wish to use it on low setting for 10 hours overnight then your usage would be 1.7 x 10 = 17 a/h plus the warm up period on high setting of say 2 hours would then be 3.75 x 2 = 7.5 a/h + 17 a/h = 24.5 a/h which must be replaced via your solar panels during the day (plus any other loads that you may have, ie lights etc). This would mean that you require a battery of at least 50 a/h just to run the blanket.

AS you can only rely on 8 hours of good sunlight per day, and that is if you are moving the orientation of your panels to make maximum gains, then you would require panels that would deliver minimum of 25a/h during that period, or panels of a minimum output of 37.5 watts plus a safety margin( 25 a/h equates to 300 watts required over 8 hours = 37.5w/h), also remember that few solar panels actually deliver their rated output.

Hope this is of assistance.
Regards
Athol
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Follow Up By: Steve in Kakadu - Friday, Jun 02, 2017 at 22:17

Friday, Jun 02, 2017 at 22:17
What he said.
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Follow Up By: aussiedingo (River Rina) - Saturday, Jun 03, 2017 at 10:19

Saturday, Jun 03, 2017 at 10:19
Thanks Athol, that is exactly what I wanted to know! In my 42 years old van I have 2 new Fullriver 120 a/h batteries with 1 - 110w solar panel mounted on the roof & a portable 250w panel I chase the sun with so it should be able to handle it ok? thanks again, regards, norm
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Follow Up By: nickb - Saturday, Jun 03, 2017 at 20:31

Saturday, Jun 03, 2017 at 20:31
While I agree with the theory above, real world can be very different.
For example, last weekend I spent 2 nights free camping 2 hrs south of Perth. My camper has 2 120w panels mounted flat on the roof feeding a 120a/hr battery. It feeds a 57L compressor fridge, lights, water pump and charges the camera and phone. In this cool weather I use about 10-12A each 24hrs (when solar panels provide no charge).
It was overcast for most of the weekend, maybe 3hrs sun each day before the shade came over. Battery went into float mode around 9:30 first day then around 10:00 the second day.
I would happily run that electric blanket as well as my other stuff and be confident that I would have a fully charged battery each day.
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Follow Up By: Athol W1 - Saturday, Jun 03, 2017 at 21:31

Saturday, Jun 03, 2017 at 21:31
Nick b
I too have solar panels mounted flat on the roof, some 400w on the van and a further 100w on the roof of the ute. I have 420 a/h of battery to charge during the day, with a daily use in the vicinity of 200 a/h. My wife is on home oxygen and that machine alone uses around 8 amps for 16 hours/day or 128a/h.

Whilst I am south of the Tropic of Capricorn then the angle of the solar panels is not conducive to maximum efficiency, and I can still have a requirement run the generator for some hours to replenish the batteries for the night's use. This use can be as much as 6 hours at a charge rate of 35 amps, depending on atmospheric conditions. With the solar panels fitted to the roof then maximum efficiency would only be attained when north of the Tropic of Capricorn during the Summer months, however there was sufficient efficiency once north of Alice Springs last week.

As I mentioned in my original posting was that solar panels MUST be orientated directly towards the sun, and continually changed to follow the sun, for maximum efficiency, and even then they are not all capable of their rated output.

Hope this helps.
Regards
Athol
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Follow Up By: nickb - Sunday, Jun 04, 2017 at 01:38

Sunday, Jun 04, 2017 at 01:38
Agree 100% on solar panel orientation and efficiency.

I'm just giving a real world example where 240W of solar, mounted flat, can replenish 10-12A in around 2-3hrs of morning winter sun. Using your example above where 24.5A/hr needs to be replaced, the conditions and setup I described above would see my battery back on float charge by 11-12:00 at the latest. Just some food for thought for Ausiedingo.

As a side note you have one hell of a solar/battery setup!!
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Follow Up By: Athol W1 - Sunday, Jun 04, 2017 at 10:20

Sunday, Jun 04, 2017 at 10:20
Yes nickb, it is amazing what can be done when the need arises.
It was a matter of sort it out or give up the travelling and free camping, and I decided to come up with a solution that covers all weather conditions.
Regards
Athol
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Follow Up By: terryt - Sunday, Jun 04, 2017 at 12:35

Sunday, Jun 04, 2017 at 12:35
Nickb. 10 to 12 amphours to run a 57 lire compressor fridge, lights, pump and charge camera for 24 hours with NO solar input. If it wasn't a misprint you're dreaming. (unless you have your fridge set to 5 degrees and the ambient temp doesn't get much over that.)
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Follow Up By: nickb - Sunday, Jun 04, 2017 at 12:35

Sunday, Jun 04, 2017 at 12:35
Do you have a write up or blog about your setup and usage? Just interested how others go about tackling their electrical solar needs.
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Follow Up By: nickb - Sunday, Jun 04, 2017 at 23:49

Sunday, Jun 04, 2017 at 23:49
Sorry Terryt, I didn't word it correctly. I used 10-12A whilst there was no solar input ie. from about 530pm to 630am.
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Follow Up By: terryt - Monday, Jun 05, 2017 at 14:53

Monday, Jun 05, 2017 at 14:53
Thanks for clarifying that Nick
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Reply By: Nomadic Navara - Sunday, Jun 04, 2017 at 15:58

Sunday, Jun 04, 2017 at 15:58
This is dependent on the requirement for the blanket. If she only uses it for one hour to preheat the bed then you will only draw 4 Ah from the battery. You can probably spare that capacity without having to add anything to the system. If is going to be used as a heater all night then (including pre-warming) this could mean 8 hours @ 1.7 A or nearly 14 Ah. Depending on how much other power use you have you may have to add some extra capacity to your system
PeterD
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