Which freaking battery for 1500w inverter in vehicle...and why?

sometimes I need a few minutes of instant heat in my cold minivan. Warm winter bag is fine for sleeping but I will not start burning fuel in a V6 merely to generate delayed heat. I have a middling 1500w sine wave inverter, a petite space heater, and a 6 amp charger. Planning on topping off battery as needed. The battery will not get charged by alternator. Was figuring a car battery, same as the one under the hood (makes sense to me.) I know lead acid car batteries aren't ideal but I am not as risk averse as most rational people.

Cannot tell you how many people, especially at your fancier resorts, look at me like I’m an alien when they ask about my sleeping accommodations and I tell them: winter sleeping bag rated to minus twenty F. Have done it for many dozens of nights over the past several years. It is time to enhance my modest camper for one.

I know virtually nothing about this subject but I think part of the reason lead acid isn't ideal for this application is the limited discharge capacity compared to other types of batteries that are made to be discharged more completely during use. Back in the day we used to get deep cycle batteries for applications (winching, lotta speakers, exterior lighting, etc) where we regularly needed to discharge them below 50-60% but now you can get a lithium ion battery as a stand alone unit or as part of an integrated power system.

Lithium ion if you want to spend a bunch of money for a nice battery. AGM if you want to spend considerably less for an ok battery. Both can go inside the car without issue. Both are sealed, and therefore can be bought online for considerably less than you will find locally.

AGM's have similar limitations as lead acid and don't want to be discharged past 60% or so, otherwise they'll get damaged. Li ion can be discharged to zero, so you can get away with a smaller battery for similar usable amp hours of use. AGM's do a little better than li ions in the cold, but both will have some reduction in capacity.

I went with 2 of these for my camper last year. So far so good.

https://www.weizeus.com/products/12v...5a747683&_ss=r

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I feel like you’re going to have to spend atleast [emoji639]x the price of a Mr Buddy heater to get a battery system to run that [emoji637][emoji6[emoji640][emoji637]][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji638]]][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji638]]]w heater for any length of time.


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The quick answer is: a 1500W inverter, to run a 1500w space heater draws an enormous amount of power. The math is: 1500/12v=125amps per hour

So your average lead acid battery has something around 100amps reserve capacity (total amps), if you draw a lead acid below 50% charge it is damaged. So essentially you can run your space heater for 20 to 30 minutes before damaging your battery. Reverse the math for charging, you'd have to charge your battery for 9 hours with a 6amp charger to recharge from that 25 minutes of heat.

Enter Lithium Ion, you can use 100% of the reserve capacity without damage, and also charge much faster (except when cold, usually below 32F you cannot charge or discharge). The downside is quality examples of the se batteries are in the $800 range.


I did a lot of rounding here so don't check the math too hard, but its close enough. There are better ways to heat a vehicle. A Chinese diesel heater in a box being one of the best.

Edit: ^^^ beat me to it. I was getting around an hour with a 100ah agm battery and a 500w heater, and factoring in cold and that it's running through an inverter.

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Inverter to run a space heater isn't a good option, no matter how big your battery is.

Any reason not to just go with a Mr Buddy or similar? Cheap to buy, cheap to run.

You can get reasonably good quality 200+ah Lithiums (LiFePO) on ebay and amazon now for like $150-200. Check out Will Prowse YT channel, he tears down batteries and reviews them. This one he was very impressed with as a 100ah for $150. Low temp protection, overcurrent protection, good quality cells, good build quality. https://www.youtube.com/watch?v=9gLIv7wa01Q https://a.co/d/1HCRvEt

Thanks all! I will never be pulling 1500w, half that for short periods of time. Minivan is a small space and I am not looking for warm, just warmer. I know a Mr Buddy would save me a few dollars. I will look into LiFePo and compare charging vs AGM.