Geeks living off the grid are hard on batteries

Many of you will remember [Mikey Sklar] from the multitude of times he’s been on hackaday. What you may not have noticed is that he is an ubergeek, living off the grid.

He has Solar PV battery bank, three electric vehicles, a shipping container loaded with battery powered tools and a small army of iRobot Roomba’s for cleaning. Getting the maximum lifetime out of a battery by removing sulfation is essential to keep expenses down.

Keeping expenses down is nearly a full time job when trying to live the homestead lifestyle. Our current culture makes it extremely difficult to survive completely on self made/grown things and bartering. They seem to be doing pretty well though. One way he can reduce his costs while still getting to enjoy some modern gadgets is to get longer life out of his batteries.  He does this by using a capacitive battery charger and desolfator that he designed and affectionately calls “Da Pimp”. He also brings in a little bit of income by selling kits!

 A capacitive charger behaves like a constant current power supply dynamically adjusting the voltage to get over the batteries internal resistance. Plus there is a pulse from the AC/DC conversion. This allows for old batteries to last longer and for dumpster dived to be used as replacements. Capacitive chargers are small, silent and super efficent (up to 60% more so than cheap transformer based chargers).

Of course, [Mikey] is a supporter of sharing information so you can also go to his site and download the schematics,bill of materials, gerber files, and files for the housing,  to build one yourself.

Comments

  1. limpkin says:

    a cap on aref is missing…

  2. Thopter says:

    If he lives off-grid, where does he get the mains AC to run this charger?

  3. AS says:

    Wow… That is damn scary. I haven’t looked at the microcode, but I wouldn’t hook that up to any lithium chemistry cells. Lead Acid would be fine, and Ni-Cd shouldn’t have much trouble. NiMH and Lithium could very very easily light on fire though.

  4. limpkin says:

    and his R1/R2 divider bridge is only designed to handle not more than 100v!
    no protection diode to vcc… come on man :/

  5. DarkSky says:

    Also no isolation from mains…

  6. Mike says:

    And if he’s using a uC, I would have put in auto shutoff when V > (12,14.4,whatever) that way you don’t have to come back and check on it. I could totally see myself forgetting about it for a few hours.

  7. eldorel says:

    If everyone can see the problems in his design, why don’t we fix it?

    To quote the site:
    “The design is completely open with source code, schematics, circuit layout and bill of materials all made available. ”

    Someone get this up on something like github so we can start making incremental changes until we have an optimal design.

  8. Dax says:

    “Our current culture makes it extremely difficult to survive completely on self made/grown things and bartering.”

    No. The fact that you’re trying to hole yourself up and isolate yourself from the society makes it so. Some things just are difficult and expensive to make at home, and that’s not a matter of culture.

    • n0lkk says:

      I’m certain a Caleb lives in the US, for the US his use of the word culture is correct, save for those few communities that have a local currency. Bartering those items than can be produced at home depends on have resources few have. very few that have rural property with resources use those resources to create valued added produces to sell, selling is bartering. My opinion that is so because of the culture that has been created. An interesting topic, but one better suited at the forums.

  9. Conundrum says:

    This guy would be useful to have around in the event of a 2013 solar storm that wipes out the power grid etc.

    • kresp0 says:

      A solar storm could damage the PV panels too

    • NewCommentor1283 says:

      alas PhotoVoltic(solarpanels), Peltier(candlepower), and any associated uC (inside batpaks) are ALL toast if there is a X-100 solar flare (EMP)

      as for the internal fuses in dumb batpaks, maybe they would be damaged too?

      … 50000v/inch is an emp so with a 3 inch wire dangling off of the end of it… 150000volts!!!

      after a solar storm, all you have if you are lucky (not connected to mains “antenna” and therefore maybe still good) are alternator/dynamo (AC gen/DC gen) and incandesant lightbulbs and batteries such as LA/SLA, NICD/NIMH(bare batteries) but lion are useless without uC

      actually, to think about it, lion packs with the internal uC might spontaneously erupt during a “huge” solar flare/emp

      PS: im not sure but the frame of a car “might” be a faraday-cage enough to protect motors and lightbulbs, ditto for car digital circuits, always enough reflected/RE-induced energy to destroy those delicate things

      • NewCommentor1283 says:

        so when you think solar flare, think half the population being dead from sitting at thier computers ect and a 1 MILLION volt lightning bolt lights up and melts everything thats thin and conductive in the entire building, including the electrical cables inside the wooden walls!

        the fire department cant put out 10 million fires all over a hugh city all at once

        MAYBE? WHY THE US IS BUILDING A HUGE EMPTY “AUTOMATED” “GHOST CITY” (see yahoo news)…
        to see exactly what happens under typical situations???, and im assuming it will have some sort of gigantic faraday cage???

      • BadIntentions says:

        If you wanna start some of that tinfoil hat survivalist crap, get your numbers right. Your numbers are magnitudes off. The absolute peak, in a contained area just south of a NUCLEAR WEAPONS generated EMP burst (in the continental use anyway) would be around 50kv/sqmeter not 50kv/sqinch. The real number is close to 30 v/sqinch. Solar eruptions would not be nearly so powerful.

        This isn’t like lightning, this is radio energy. If you had spares on hand, disconnected from the grid transformers, batteries, solar cells, motors, generators and other electrical devices would handily survive even the most powerful EMP pulse. Unless they have a long antenna, such as a power line or the national powergrid connected.

        In fact, the full metal body around a PC would provide significant protection to it. You need only unplug it from external wires that would pick up this energy.

        Cars are actually fairly well protected by their steel bodies too. Starfish prime (the bad-mofo nuclear test that accidentally knocked down Hawaii) didnt disable any vehicles. Military simulators find that most vehicles tested (including some very modern cars with complex ECUs) survived with only ancillary systems (Aircon, radio) offline.

        Even VERY sensitive electronics (microcontrollers) can be protected by installing them in a full sealed metal box or cylinder, with full metal contact. Think of a fat steel gaspipe with a well welded bottom and threaded cap. No matter how bad-ass the emp, that would provide 100% protection. Even against direct lightning strikes.

        Now, the nuclear fallout from such a device, you are on your own. I suggest a dosimeter.

        • Black Soap says:

          The engines might still work, but how many modern cars would go nuts due to anti-theft electronics, or at least require a dealer reset to convince the car that it hadn’t just been tampered with or stripped in a chop shop?

  10. Mike bradley says:

    The schematic made my eyes hurt

  11. Chris says:

    A “theory of operation” would be nice, to determine what this actually does without reading both schematic and software.

    Best I can tell from looking at the schematic alone:

    Lead-acid: Should charge well. May desulfate to some degree. Non-conductive sulfate deposits on battery plates need higher than normal charging voltage to dissolve. This is achieved since the capacitive coupling allows the voltage to rise to required levels if battery resistance is high. But as small patches become desulfated, resistance quickly drops to the point where it’s not feasible to desulfate the rest of the plate area; so this is only a partial recovery. Better than nothing though!

    NiCad: Possibility of overcharge due to the NiCad’s slight negative dV/dT when fully charged. Bad NiCads are the opposite of lead acid – they’re low-resistance due to shorts caused by the growth of conductive crystals (whiskers). A high current pulse is needed to shatter those whiskers; typically supplied by charging up a large capacitor with rectified AC, then dumping it quickly into the battery. I’m not sure if it attempts to do that, but the capacitors are too small to be effective in my opinion; I’ve had the best luck with a 330uF photoflash capacitor.

    NiMH: Stronger possibility of overcharge due to the larger negative dV/dT when fully charged. NiMH has no repairable failure mechanisms.

    Li-Ion: Mikey gave a safe answer – no. I agree with this. Highly experimental at best.

    Since the idea is to extend battery life, I’d stick to lead acid. Maybe NiCd/NiMH if no better options are available, and the charger is programmed to slightly undercharge.

    I do love the simplicity, efficiency, and economy of capacitive charging. Well worth considering for hobby projects. Just remember that it can produce dangerously high voltages, with no isolation from the AC line. That’s why you don’t see it in many commercial products, especially if they’re not entirely self-contained.

  12. BadIntentions says:

    I too live primarily off grid. Hes really doing it all the hard way. Off grid doesn’t mean isolated. Off grid just means you don’t rely on utilities for anything.

    As for being hard on batteries; sure, if you use crap batteries, the wrong kind of PV panels/wind generator, bad battery maintenance, and are not working on efficiency.

    Ditch inverters. You lose 5-25% of your energy because of them, depending on quality and load. He should be building DC powered chargers, not AC powered chargers. Hes converting DC to AC and back to DC. Just for that hes probably eating a 30% penalty.

    Either way, all decent solar charge controllers (I use 2 Xantrex 80-600s connected to 9.2kw of panels) are capable of ‘equalization charging’ which attempts to desulfate the plates.

    My current bank of batteries, made of 32 Trojan 300ah 6 volt batteries configured into 4 banks of 48 volts each, has been online for 12 years. Careful watering, and maintenance will get you farther than experimenting with your expensive battery banks.

    • BadIntentions says:

      Heh, submitted too early!

      AAANYWAY.

      For portable tools, I just use air tools. I built a 1000 gallon per day biodiesel plant and keep 0-5% in exchange for friends supplying the feedstock (cooking oil) and the chemicals. I have a Yanmar diesel electric start engine with a belt driven 3-stage compressor head connected to an 120 gallon air compressor tank. its palletized, and fits in the back of my diesel converted van. The air tools are much more reliable, if not somewhat less convenient. I just keep a few hundred feet of hose. Nice thing is, i have a lot of tools that you just cant get on battery power (framing hammer, etc).

  13. n0lkk says:

    I have a bit of a headache, perhaps that’s why I’m not seeing, how this is “safer.. for the masses”, than the more common circuit out there. I think this is inviting Murphy to hang around those who he sees build and use this. Even those who understand what they built and try to be cautious when they use it The Gods help those who pick this up to use, not knowing it’s not the typical charger, because Murphy doesn’t give a crap.

  14. Simon says:

    The latching relay (K1) in the circuit diagram and on the gerbers (bottom left of board, next to bridge rectifier) is not installed in the demo videos, nor the build instructions. K1 isn’t in the BOM. The instructions don’t ask for “links” to be installed and links do not seem to be present in the videos.

    This relay is the only thing (!4) that can connect the “A/C” to the battery.

    There are many possibilities,

    1) it is fake

    2) it is unfinished

    3) an elaborate, but late, April 1st joke

    4) a fantastic device where U1, U2, R1 and R2 and the 9v battery are “not what they seem” (aka alien, fusion powered) technology that can charge batteries.

  15. MINE says:

    Re.
    “actually, to think about it, lion packs with the internal uC might spontaneously erupt during a “huge” solar flare/emp”

    Really?! This is more than a little concerning, is this a likely possibility?
    If so then there could be hundreds of serious house and workplace fires per square mile.
    People would be spontaneously emitting flames and smoke like a mass outbreak of SHC.

    Come to think of it, relatively harmless looking items such as electric car battery packs could “go supernova” even if in storage.

  16. Mikey Sklar says:

    @Simon: K1 and the set point buttons were pulled from the final kit. That is why you do not see them in the video, pictures and BOM. The latching relay would eventually fuse from the capacitors acting like a welder causing the relay armature to be locked in place. I have some ideas for how to remedy this on a future release.

    • Simon says:

      Sorry, I should have included at least one :-). My comment was intended for those who want to build their own — you’ll need to understand it to make it work :-). The commented out bits of the source code does give a clue that it was removed.

  17. Mikey Sklar says:

    Simon: good point

  18. DaveX says:

    Essentially the circuit is passing line current through 14.1uF of capacitors (1/(2*pi*60Hz*14.1uF)=188ohms, 120V/188ohm=0.63Amps), then rectifying it to DC, then hooking it directly to the battery. The rest of the circuit is a DMM built out of a atmega48V, with code to control the non-existent relay and translate the voltage to 3 digits on the LEDs.

    For 220/50Hz operation, you could get the same current with 349 ohms, or about 9uF of capacitance.

    If you want to try this at home, hook a 450V, 14uF capacitor in series with a bridge rectifier, put the outputs on your battery and watch it with your voltmeter.

  19. Harvie.CZ says:

    What about using half-bridge rectifier (and possibly double capacitor capacity) instead of full-bridge rectifier? That would make less frequent current peaks (which may be bigger if you alter capacitors). Giving battery some time to take a rest between these pulses… i think it could be better for the battery… Any ideas?

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