gcrank1
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# Posted: 6 Mar 2021 05:12pm - Edited by: gcrank1
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In my apparently never ending experiments to see how little I can get away with (without actually forgetting about elec all together....), and to lighten my load for trekking in this winter, I determined to use, and time, my old 17ah auto-jump pack and my re-purposed kid-car 12ah deep cycle battery, both are sealed LA 12v but I suspect the jump pack is not deep cycle (it was intended to jump start a car).
Others have posted up about wanting to only run a couple lights, usb ports, etc; all light duty uses similar to what Ive pared it down to this winter, so I thought some real-time results might be informative.
Here is what I typically have been running, all on a 300w psw inverter to 120vac: (and I have no Kill-a-watt meter) and est amps draw c/w inv factored in:
One 9w led light bulb (1a per) needed of an evening, rarely 2.
The fan to circulate heat out of the peak back into the room (2a on low).
USB port to recharge the phone only sometimes but that is actually easier to just fully charge it in the car on the way to the cabin. Amps? not much.
Sometimes a bit of 1970's vintage portable radio. A?
Usually during the day it has been the fan on low at about 2a so I did the timing yesterday with that.
My 12ah FLA has, of course a net 6ah really useable and I got a little better than 3 hrs out of it before the little inv. started cycling its low voltage shutdown. At that point the battery, with a little rest, read at 11.85v; lower than my typical target low of 12.2 but it proved out the inv. works to shut down under load.
So, the est 6ah net translates into 1a for 6hrs or, as in this test 2a for 3; pretty much right on the calc.
Fwiw, my old, tired jump pack 17ah/8.5 net has done similar for 4hrs + a bit, it too pretty much in the calc, especially since I doubt it is a deep cycle at all.
My old 100ah sealed LA 'marine' battery has really been only about 80ah for a long time now (seems a common complaint on those). At a net 40 And the 2a draw should be about 20hrs, add in a light @ 1a and some radio/usb for 4ish and that is only 10hrs. But no way Im taking that home to charge and bring back unless I can drive in, even then that 65ish# I dislike moving much. It does make for a couple of days light duty use and justifies having some solar to recharge during our absence. I first used 2x100w panels in series and a mppt scc with success for that. From my experience I wouldnt want to use less of an array. If charging of a good solar day while there I want that to recharge by early to mid-aft, not trickle charge over 3 days or so.
If all I ran was one of my 9w (about a 40w equiv lumens) I could double those hours of use. And those bulbs do throw good light (I get a 4 pack for only a few bucks at the local Habitat for Humanity 'Restore' and use em at home too. NO burn outs yet!).
My conclusion: FLA has limitations for packing in. Small ah batteries can provide about enough light for an evening, maybe even run a small fan for a while, if you want both plan on bed early. I think you would still be able to run a bulb in the morning which would be nice.
Better: LFP; even a 20ah one will have likely a 16ah net @ 1a draw, or with my 2a fan an 8hr run. I'd figure that as a solid overnighter, some time at 3a draw, maybe 2 evenings with care. Still, that is at the micro-use end....but surely luggable. They also come in 40 and 50ah versions.
Best: To have multi day/evening use, even some time at 4-5a draw, the 100ah LFP looks to be the bang for the buck if you can trek in another 30#, or drive in to stay a weekend, etc. Use while there and take it home to recharge on the grid for next time. It can grow into generator or solar recharge at the cabin over time if you want.
But, Imo: If you want to start drawing a pretty consistent 5a or more you are going to need to look at 200ah storage from LFP or 400 from FLA; that is gonna cost.
And keep in mind, all the above is NOT 24hr's a day use!
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gcrank1
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# Posted: 8 Mar 2021 07:19pm - Edited by: gcrank1
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Im not 'worried'. I did the tests because I can and its suits my analytical nature. 
This is about battery power, not solar recharging or (over)sizing a system to have 'more than enough'.
On this site, as well as others Im sure we get visitors who do an online query asking for info like this; ie, 'I dont need much so how big a battery/system do I need to do xyz? I dont have/want solar or a gen, figured to just bring a battery for a couple days and take it home to charge.'
Or, 'Ive got this little battery, what can I do with it?'
And,'I ran some stuff and my battery went flat in 1.5 hrs.'
A lot of the replies are way too involved, expensive, complicated or all three.....
Now Ive got all this stuff and I like to know the capabilities of my stuff for future ref. Works for me.
Ymmv
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groingo
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# Posted: 24 Mar 2021 02:42pm - Edited by: groingo
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I used to do that, looking for every way to reduce power use, learned alot too, most important thing, keep it simple, reducing is fine so long as you don't sacrifice quality of life, now with newer improved technology I have exceeded goals from ten years ago, average power use is way down from 1 kwh a day to 350 watts a day thanks to recent upgrades, went from PWM controller to MPPT Epever controller, downsized inverter from 750 watt modified to 650 watt pure sinewave, dumped the 7 year floodeds for 1 100 ah Battleborn Lifepo4 battery and the biggest power saver was dumping my 1.1 compact fridge and getting an Alpicool 21 quart 12 volt / 110 fridge freezer.
Original solar panels still pulling great.
The BB battery because it charges easily 5 times faster than flooded was key, it can grab a lot more energy from sunless days and is programmed never to discharge below 30% to prolong life. . .(which it is has never done).
Heat for past 8 years has been by my own design propane heater that has been verified by Kitsap fire dept and health department to produce no detectable carbon monoxide or Co2 and does not fog interior windows or cause moisture problems while using 5 gallons of propane in dead of winter every 25 days running 16 hrs a day.
The technology today does exist to live frugal yet comfortable, and the tools exist to invent it if they don't make it.
Anyone ever hear from Mountain Don?
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