Solar Fueled Emergency Power Pack

Heavy rainfall in Northern Europe last month caused disastrous flooding in several countries. [Daniel Jedecke] was on assignment in the North Rhine-Westphalia region of Germany during the floods and saw the damage firsthand. He was struck by the lack of emergency power, and set about the task of designing a simple, portable power pack.

[Daniel] wanted his system to be as simple and maintenance-free as possible, and well as inexpensive. He passed by the traditional solutions such as gasoline fueled generators or advanced chemistry battery packs. Instead, he settled on the ordinary car battery — they’re easy to obtain in a pinch, and he found a used 45 Ah one sitting in his basement. To keep the system portable, he decided on a single 80 W monocrystalline solar panel which comes with a smart battery charge controller. An inverter provides standard (for Germany) 240 VAC in addition to the +12 VDC output.

The whole thing, except the panel, is installed in an off-the-shelf toolbox with the pieces secured to a custom-made wood frame. We think [Daniel]’s goals were met: made from standard materials, long-lasting without excessive maintenance, portable, and providing both DC and AC outputs for everyday use. Way back in 2015 we wrote about an emergency battery pack using rechargeable drill batteries. Do you keep an emergency power pack handy in case of outages or disasters?

23 thoughts on “Solar Fueled Emergency Power Pack

  1. I got lots of back up power. Will use my drone batteries for powering 5volt USB stuff(charging, fans) using a USB buck converter and I got 5 of 7AH SLA for 12 volt stuff and I got a solar cart like the one he made with 70AH of batteries and 445 watts of panels and inverter. Check out Sunpowercart dot com for the cart they sell plans or ready to go. The big panels fold up flat and the 45 watt is mounted on top of the tool cart for trickle charging the batteries when in standby. Would suck to have flat batteries when you needed it!
    Of course got a generator for the fridge and a window AC unit, after 1 or 2 hurricanes taking power out for days, YOU WILL want that AC unit even if you got to siphon gas out of a car LOL. Cold showers only last so long and it’s alot easier sleeping if the temp isn’t sweating while sitting still hot!

  2. While 12V backup solutions have some merit for really small loads, they don’t have the ability to do much more than to run some lights and charge some phones (which is much better done at 12V than inverting to 120/240V).

    A 45 AH battery (if you could get all of the 45AH hour out of it, which you probably can’t) is 540 WH. A refrigerator is around 120W, which means less than 4 hours of run time.
    A hot water heater, 4,000 watts, or about 6 minutes.

    I hate to blow the wind out of sails. But it’s better to realize what you can do than find out when the lights go out. Honestly, fuel powered generators are about the only way to handle power outages.

    1. I can tell you from personal experience that 450W solar with 220AH marine leisure battery will comfortably run an under counter fridge at the OPs latitude continuously in all but the shoulder months. Only an idiot would try to run a 3kW water heater from such an arrangement – direct heat propane is much better suited to that task, whether in a water heater designed for the job or using a kettle on a camping gas stove. Slightly OT, if you have solar and can divert the surplus to DC immersion, then that’s a good option.

    2. Really depends on your priorities – a small portable pack with some self charging like this is more the camping trip type use case – you are daft if you really expect to power a 21st century life from anything that small, but powering some lights, a music player, radio, even high power computer (for a while) each day is very much possible..

      If you want to power a modern lifestyle just on solar you need a roof full of panels, and massively more battery – just running the fridge over the night is a few KWh… Maybe more – depends on the size of your roof and just how profligate with electric consumption you are…

    3. You’re making a lot of assumptions on what people want to power. If all they want is a light, radio, and charge a couple of cell phones, the author’s set up is adequate.

      I personally have both, lead acid battery for low power items, and a generator for higher draw devices and appliances such as the freezer to keep the food from going bad.

    4. “A refrigerator is around 120W, which means less than 4 hours of run time.”

      I do have a combined fridge/freezer, it uses around 40W/h in average.

      Another thing is, if a lead-acid battery is discharged lower then 50%, the lifetime is rapidly reduced.

  3. I have a few 3KVA APC UPS units each rewired to four external 12V 75Ah gel cells (48V).

    These provide back up power for the sump pump, fridge, freezer, computers, work bench, etc…

    One of these days I want to do a whole house battery back up with used electric vehicle packs.

    1. Hmm, I know the feeling of wanting more battery…

      Though I am seriously more tempted by a modest CAES supplement to the existing small solar filled battery – much more fun to build, efficiency can be better (for longer storage durations), at least equivalent (for modest loads), and potential peak power output to play with is fantastically greater… Can’t have them all at once of course, but the fun of building it and choice in how you drain it gives it more interest to me. Even though it will have to be physically much larger for the same energy store…

  4. After living off the grid for over 10 years, I can say this. There’s no such thing as having lots of backup power because unless you put $5k to10k into a system to get upwards of 1kw of solar and or combined with wind along with 300+ A/H, you aint got squat and that 300A/H is not going to last long, at one time I had over 5k A/H’s with a 2kw inverter, a 1.2kw inverter and a couple of smaller ones to run loads and it still wasn’t enough for some things ! Dividing your loads up on different inverters is actually cheaper and smarter than having 1 big inverter. It’s also a little more efficient, plus as with anything else it can fail. So you won’t loose all of your power in that case. It’s harder to set up though. Sure a portable system is nice if you have to watch a few hours of TV, listen to a radio or use a few LED lights for night time whatever. If the power goes out and you live somewhere with a water well that needs a pump running? Or have a freezer, refrig, or some other essential appliance that cannot be left off for long periods you’re screwed. Sure it’s nice to have an AC but that isn’t an essential appliance. If it’s a warmer climate a ceiling fan or even a floor fan would be nice but not an absolute. All these so called portable power packs are about good for nothing more than tailgate parties, a day at the beach or camping. We are power pigs anymore and it’s going to be a major factor in survival in the future if something isn’t done to stop burning fuels. The pollution from manufacturing all that solar stuff and batteries is going to be another factor along with all of our other hi-tech stuff. I’m not off the grid anymore at least for now and my fore seeable future on account of several things. I am living in a motorhome on a rental lot with shore power but I do have 400 watts of solar on the roof with 330A/H of battery, a 4kw generator, it doesn’t run but I intend to fix it some day. I would like to return off grid but health reasons and age of me and the wife most likely will not make that a for sure thing.

  5. I do agree that LiPo are a higher fire risk which is why I prefer LiFePO4, but the argument that they may be hard to obtain seems suspect. Sure you can pull lead acid batteries out of a car, but this project also depends on acquiring a solar panel and charge controller which I assume were ordered? A modern, higher-performing battery doesn’t seem like too much extra difficulty to acquire.

    With Lead Acid chemistry, you only want to discharge to 50% of the Ah rating to avoid battery damage, so this setup really only supplies 270 Wh nominally whereas with lithium you can pull the full 100% nominal rating. Lead acid also can be damaged by sitting at partial charge and need to be fully charged every 2-4 weeks or kept on a float charger. A LiFePO4 can sit and only loses around 3% per month in self-discharge. A modern LiFePO4 battery with a good controller is a huge performance increase over comparable lead acid:

    For the same 320 euro price, you can get an all in one LiFePO4 “portable power station” that is smaller, lighter, higher capacity, and may include additional outputs like USB-C PD. Granted, it could be hard to obtain during a disaster scenario, but it is inexpensive and useful enough that I think everyone should have one or two around for emergencies.

  6. I have 5KW of solar during daytime ( permanent installation), 10KWh of battery storage and a 5KW inverter. Inow wish I had installed a 10KW inverter instead, any time the load exceeds the inverter capacity, it trips and then takes about 1 minute to auto-reset (a major pita). when the sun sets any less than 10 KWh is a waste of time when when only 2 fridges, the lights and a TV is on.

  7. Yesterday we had our monthly summer street fest. Perfect weather for once. I run sound at one intersection and opposite my area someone fired up a generator with lots of noise. I asked them to move it to the farthest end of their food stand a truck and tent with electric cookers and refrigeration.

    Then I told them that even the Romans had ice and it would work for the short time event. Propane or briquettes could be doing the cooking and the noise would be gone (high 90’s dB).

    5 blocks of free fun with a mix of non electric and generator powered food vendors. There are alternatives. Propane can run a generator as well.

  8. It looks fine and simple, but I’m a bit puzzled by the cable length in the box.
    For larger loads in emergency I was thinking of converting a small generator to accept butane gas, that’ll have a linger shelf life than gasoline, but a UPS combined with solar panels or a kit like this is always handy for tiny loads.

    Recently, I’ve used two USB-C battery banks with a pair of ZY12PDN at 20V in series to power a small PoE switch to power your basic communication needs like a 4G modem and accesspoint, but it comes without charging and therefore no prolonged uptime.

      1. Top tip with floods – use your clean water supply and flood our house from the taps inside, at a slightly higher level than the outside.

        Then you won’t get any faeces entering the house and the cleanup will be that much easier.

  9. This is nice and simple. There always seems to be some unnecessary heavy pressure to jack it up enough to power a strip mine shovel or aircraft carrier without looking at needs or goals.

  10. I spoke to Daniel a few days ago.

    A car battery was deliberately chosen as their containers tend to pile up at street corners or in ditches after such a flood, and one can scavenge the battery quite easily – most lead-acid batteries survive a short submersion surprisingly well. A lead-acid battery can only yield ~60% of its nominal capacity – for a small car 54Ah battery that’s ~400Wh.

    The design goals are NOT powering a fully autonomous / island estate, but providing bare necessities when there is no electricity anywhere near – and maybe with a scavenged battery or two. The goals are

    1.) charging phones / pads / laptops of family & neighbours (obviously possible, probably quite overpowered for phones-only)

    2.) powering a light in 1-2 rooms (obviously, easy with standard LED lighting)

    3.) capable enough for warming baby bottles/meals (the heaters usually come around 80-100W – can do that, too)

    4.) barely able to sustain a standard German under-the-counter fridge for a day (i.e. not the US walk-in variant) which run at 250W peak – will last a day as it only runs in intervals (tested)

    5.) able to sustain a sleeping-breather/CPAP (20-150W) – will last a few nights without humidification, or barely one with efficient systems, or just a few hours with older ones (you’d need a bigger battery for those)

    1. A very good reason to pick Pb battery, they are at least for now globally so trivial to find, and pretty much all compatible 12 standard – the days of anything but 12V being common are pretty long gone…

      Seems like with goal 5 inparticular the solar panel needs bumping up in size significantly, or perhaps given simple sun tracking – the oil filled tube shaded by the cell approach perhaps? the 20-150w for a whole night (especially those longer winter ones) of the breather – a very essential device for its human will not be made up reliably in the daylight on such a small solar panel – maybe the 20-50w range with good clear sky and some manual sun tracking will last the night from the days charge. With really great sun tracking and no obstructions to the horizon maybe that upper limit can be pushed some on a good day – but for a crucial lifesaving device you really need to reliably generate enough even on the overcast days, or have enough battery life to keep it running for several more nights and recharge fully in just one or two good days.

      The fridge is probably pushing it a little a too, but the really well insulated models at least when not having to deal with really hot weather I would expect it to be good enough – even if it does run out before sun-up the temperature won’t get that far out of spec before the battery is full enough to reactive the fridge (even with sun tracking a panel that can’t produce the peak the fridge demands is likely better off giving it nothing and building the battery up enough that the fridge can then get into its stride and run at peak power for long enough to get all the way to target temperature).

  11. I live in a building that has a generator on the roof to power the hallway
    lights. If the power goes out, the apartments go out too.
    No place to put a solar panel, but I do have a package with enough AA batteries
    to power my little grundig g3 for a while. Most if not all my foodstuffs are non-perishable. After reading about the tesla battery fire that burned for days and was quite difficult to extinguish, I don’t think I’d want something like that.

  12. I ruined two car batteries by running my inverter on them. I understand that car batteries are only designed to be drained to 90% charge as an engineering trade-off for providing high current for a short time. That makes sense since the engine and alternator will usually start charging it very soon afterwards. Even deep-cycle batteries should not usually be drained below 50% capacity many times, so that has be factored in to any backup time/capacity calculations.

  13. I have a box that has a small .5A 3 stage charger and a 300W inverter in the middle, and 2 12V 24 AH AGM cells. I call it my juice box. It has it’s uses. I can jump a car or a mower with it. I can run a 12V compressor off of it. I can run a small 120V load off of it.

    I also have a much smaller and lighter LIPO jump pack that will start a big farm tractor, a car is easy, and it is a whole lot easier lighter and easier to use.

    I also have a 1.2KW 2 cycle generator that weighs about the same as the juice pack. It has a DC output so it can charge a battery, I have not tried jumping a car off of it. On the plus side it will run for more than a half day on a tank of gas. It is really hard beat gas for power. I have a few solar arrays on outbuildings and they do OK for what they are.

    My greenhouse has water from the pond thanks to solar and my small house has enough solar charged battery to run a notebook overnight, a radio for tunes, and LED lights, and a short wavelength UV lamp cycles on for a while every couple of days to combat mold and mildew.

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