mains electric blanket

Hi all hope someone can sort me out?
I have a mains electric blanket it is only 35 Watt. I have in my van two new 110 amp battries 80 watt solor panel and a 500 watt inverter, My question is can i run the blanket via the inverter whilst of hook up, and how long for roughly, we are doing our first of hook up camp next weekend and would at least like to get in to a warm bed.

Thank you
Graham

graham01 wrote:Hi all hope someone can sort me out?
I have a mains electric blanket it is only 35 Watt. I have in my van two new 110 amp battries 80 watt solor panel and a 500 watt inverter, My question is can i run the blanket via the inverter whilst of hook up, and how long for roughly, we are doing our first of hook up camp next weekend and would at least like to get in to a warm bed.

Thank you
Graham

Graham,

Watts divided by Volts = Amps so in theory 35 watts divided by 240 volts = 0.15Amps load on the 240 volts supply.

However, 35 watts divided by 12 volts = 3Amps.

Assume a 400% inefficiency rate for converting 12 volts to 240 volts (there should be an indication of % efficiency on the Instructions) and you will be pulling 12Amps on the 12 volt system and a 110Amp battery should therefore last 9 hours.

That's "in theory" but:

A) I wouldn't trust these figures for one second.

B) Mojo will put me right on the "theory" so I am probably out by a factor of 10 either way!

Best regards,

Ian

Thanks Ian
if i read your post right i should be able at least to warm the bed say 2 hours before i get in

graham01 wrote:Thanks Ian
if i read your post right i should be able at least to warm the bed say 2 hours before i get in

Graham,

Enjoy; but keep an eye on the voltage and remember that below 10.4 volts for a lead-acid battery you are probably inflicting severe damage!

I remember boasting "I love to get into a cold bed!" and was shot down in flames by someone who said "As you never come to bed until two hours after me how did you work that out?"

Best regards,

Ian

Dutto wrote:
B) Mojo will put me right on the "theory" so I am probably out by a factor of 10 either way!

Theory looks fine to me, though you may be a bit pessimistic about the efficiency of the inverter - last time I looked I think you could expect losses of up to 40%, though that varies according to a lot of factors.

It doesn't look like you should have any problems running for 2 hours each night for several nights in a row, but don't think you could have it on all night every night for several days.

As Ian says, you should not be planning to get anywhere near to flattening the batteries - even if they are leisure batteries - so do listen out for a low battery alarm on your panel and take action as soon as you hear it.

IF it gets too cold whats wrong with 2 hot water bottles and wooly hats ??