12v electric blanket?

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

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