Cosmo wrote:
From a numbers perspective a 60 amp hour battery at 12V = 720 watt hours. Ignoring cost
AGM 120 amp hour at 50% useable power = 720 watt hours. Ignoring weight.
You are ignoring some important info. the 60 amp lithium will be 1/2 the size and 1/4 the weight. Cost you could diy a 60 amp lithium for under 200 with out much trouble, but 300 if you buy one. A good name brand agm is close to 200 last time I looked. Sure there are some cheaper.
Cosmo wrote:
12 Watt heating pad will consume 288 watts in 24 hours or 24 amps running continuously ( my edit, unless you total for the day, which I think you do ) . Major assumption here based on nothing - If the heater runs s 50% with a thermostat in 24 hours it would consume 144 watts or 12 amps. leaving 576 watts or 48 amps of power for consumption.
Your math is off, a 12 watt heating pad will consume 1 amp an hour, or 24 ah in a day. if it runs 50 % your down to 12 ah. I think more realistic is the heater running 10 to 25% of the time, as you would not due this with out insulating the battery ( if you where smart ) even just a layer of 1 inch foam tapped on it ( now it is larger )
Cosmo wrote:
For comparison a 120AH AGM would provide 60AH of usable power. Both the AGM and Lithium will loose efficiency in cold weather. I am guessing the AGM will loose 1/3 capacity which brings available power down to 40 amps or 480 watts. Not sure about the Lithium. The difference under these extreme conditions might be 8 amps or 96 watts of extra power from the Lithium. When the cost per watt of the gain is calculated its expensive. Of course the rest of the year in friendly temperatures it’s a different story and lithium wins. There are other factors both pro and con for both batteries.
Lithium looses about 15%, but if your eating it then the loss is even less, but made up for by whats used to heat it. read the article at the end battle born only got 8.1 % out of the lead acid in a high drain test 15 % in a low draw test
Cosmo wrote:
I am sure my calculations are embedded with errors and I am missing a lot of considerations. My intent is to learn more.
Thanks for your help and research
=Cosmo
https://mortonsonthemove.com/lithium-ba ... d-weather/