They would also likely have some of the same safety features i mentioned above for the inverter. The ac battery chargers you would need to have to run off the inverter, also add layers of redundancy because they could be used in the car, in the house, or any AC you have access to, etc.Only the better, more expensive DC-DC converters have any of that, and probably very few have ALL of that. A small 12v ac 'travel inverter' is intended to be used by people who know absolutely nothing about electricity and will basically always have things like reverse polarity protection, fusing, high voltage & low voltage warnings and cutoffs, overheat alarm and then shutdown, overload alarm and then shutdown, etc etc. A step up converter is much more likely to be susceptible to mistakes.The step up converter is a one trick pony in terms of 'preparedness'. An ac inverter can be used for basically anything you own that falls under its watt rating, while the dc dc converter requires you to huck your big batteries over to your car and can't 'directly' power anything else that wouldn't already be able to be powered from the car by just hooking directly to it without the converter! The 12v inverter could also be taken in your house, or really anywhere you can take any 12v batteries (campsite? hideout?). Which is kind of funny considering the AC inverter has to have a fairly large step up converter in it anyway, but i digress. A dc-dc step up converter large enough to accomplish many hundreds of watts of charging is very expensive compared to an equivalently powerful ac inverter.I would use a 12v to 220v AC inverter for several reasons: it's not the method i would choose from an 'emergency preparedness' point of view. A dc-to-dc step-up converter is a valid option, and probably technically the most efficient. To charge '12v' (or higher!) lithium batteries from a car requires stepping up voltage, which has already been talked about. The background assumption is that if grid electricity is down, so is fuel distribution and you would need to make the most of whatever you have. So i am basically against 'bothering' to do 100-something Watts from a running car unless you are also driving it, because the engine takes about a couple thousand watts of power just to idle, and throwing 2000 out the window so you can 'keep' 100-something is extremely wasteful if you are 'rationing' fuel due to power loss. It's not cheap, but I believe it's a "set and forget" product that will make life easier. If I recall correctly, you can also set max charging current. The Orion Tr Smart can be programmed to sense when the alternator is running, so that it doesn't charge your Lifepo4 when engine is off (preventing draining your starter battery). If you don't have common ground, you can get the isolated version, but then you have two separate grounds/negatives. The best solution, with minimal wiring is a Victron Orion Tr Smart Non-isolated: Only 3 connections are needed: Common ground (if you have your Lifepo4 ground connected to AGM/Starter/Alternator ground), Input positive and Output positive. Nothing there to regulate it.Īlso, if you have it plugged in while cigarette lighter socket is powered (some cars have them permanently on) like in accessory mode (engine not running), you will drain down your starter battery. If you just connect it to your battery, you will blow the fuse fairly quickly as Lifepo4 pulls as much amps as it wants. I can confirm that pulling above 5 amps makes the cigarette lighter plug hot.
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