66% or better

Solar charging your DS

solar_ds

[dark sponge] decided to make his DS lite, solar powered. Or, at least charged via solar panels.  He was able to find solar cells that were 60×60 mm, which means he could fit 4 of them on the outside of the DS. This gives him a total of 6V at 80 mA output. These panels charge the battery between uses. The DS has to be open and laying on its face for all 4 panels to be exposed, but this way of mounting them didn’t alter the pocket-ability of the unit. He says he’s been using it for a while and hasn’t had to plug it in yet, but we have concerns about wiring the panels directly to the battery. As [cyrozap] points out in the comments on the instructable, this is a Lithium Ion battery, shouldn’t there be some charging circuitry involved?

Comments

  1. Ben S says:

    Should have cannibalized an AC adapter for its connector and used it to make a dongle to plug into the AC port.

  2. Ben S says:

    on second thought, it’s possible that the charging circuitry is in the battery itself.

  3. Anonymous says:

    I’m pretty sure that, like laptop batteries, the protection circuit is in the battery pack itself.

  4. Peter says:

    I’ll third that, I also think the circuitry is within the battery itself.

  5. BartB says:

    It would be strange that the charging circuit would be in the battery. As a designer I would want all space in the battery pack used for the battery. The charging/protection circuit does not need replacement when the battery is past its life.

    This way of charging a Li-ion battery is dangerous. He would be better off in using a step up converter and using a real charge controller. Or much easier, connect directly to charging circuit in the DS where the power connector enters.

  6. eric says:

    I think most (all?) lithium ion batteries have charging and protection circuitry built in for safety reasons.

  7. PlatinumT says:

    They usually have protection circuitry but I’ve never seen charging circuitry built into the battery.

  8. cyrozap says:

    I still don’t understand how this could work without a charging circuit. Li-ion batteries have to be charged a certain way or else they can overcharge and explode. I think the only way this would work was if there was a charging circuit inside the battery. Even if that is true, it is meant to charge from 5V, not the 8.11 volts he showed on the multimeter. And, if you’re wondering, I’m the same Cyrozap as on Instructables.

  9. Eric says:

    At <=80mA I doubt there’s any danger in anything.

  10. hex4def6 says:

    Hmm… if its wired directly to the battery, what happens when the potential across the panels drops due to low light levels? I have a feeling you’ll be pumping power through the cell, and discharging the battery.

  11. _Matt says:

    the protection circuitry will shut the current off to the batteries if there was a problem, so in a sense it is a charging circuit.

    neat hack though.

  12. hex4def6 says:

    Correction; he does have protection diodes.

  13. polymath says:

    well if Nintendo used commercially available batteries instead of developing their own they could have the circuit already built in. I am with _matt on this one. is there really a difference between a charging and protection circuit or is one just a more complex version of the other?

  14. ax0n says:

    I’m also pretty sure a mere 80mA won’t cause permanent harm to fully-charged LiON cells. The danger in charging them comes from the fact that they get hot near the end of their charge cycle, so most charging circuits use thermistors right near the cells to sense the charging is nearly complete. The “circuitry” can be in the pack, but often the thermistor sends a signal back to the laptop or device to let it control the charge.

    Regardless, I don’t think even in full light that you’d see destructive over-heating from this kind of charging scheme. It’s a clever and well-executed hack.

  15. anon says:

    With the DS open, the back is facing down.

    How often have people encountered a situation where the back is getting direct sunlight?

    I guess you could get one of those old-school tanning shades (foil on cardboard)!

  16. firetech says:

    Does anyone have an old dead DS Lite battery to rip apart, and place some pictures up on flickr

    I’d be interested to see if there one.

    According to other ‘replacement’ batteries this model of the battery has a protection / charging circuit in it.

  17. tubes says:

    I have ripped open a battery and the only circuit in it is a wire from the back that connects to a pcb to the front with no other components other then the + – connectors for the DS to get power.

  18. Tony says:

    You guys sure your not thinking of Li-poly batteries? Those definitely have circuits with them for protection, I know I’ve got a couple laying on my bench right now with circuits on them. I am unsure that Li-ion batteries take this precaution though.

  19. toaste says:

    Batteries often contain deep-discharge protection on the unit itself, but DO NOT typically contain overcharge protection.

    Both can destroy the battery, and this probably shouldn’t be allowed to sit in the sun too long.

    On the other hand, the cells don’t generate the current that the normal charging circuit typically demands from the wall charger. It may still work, but that would require a bit more testing

    Probably the best option would be to cannibalize the slow li-ion charger from one of those solar charging widgets that have a battery built in. They’re designed to slowly charge an internal battery and later discharge it through the charging circuit of whatever you want to power up. Wiring the charger output from one of these straight to the DS battery would probably provide a lasting solution.

  20. jz321 says:

    “the protection circuitry will shut the current off to the batteries if there was a problem, so in a sense it is a charging circuit.” -Matt

    Actually,
    a protection circuit protects the battery from over-discharge current, under-voltage, and over-voltage.

    A charge management circuit would charge the lithium battery according to specifications of that type of chemistry. Constant current mode until 4.2v is reached followed by a constant voltage mode until the charging current diminishes.

    Cool hack though…add a MCP73831 lithium battery charge management IC and youd be set without the risk of damaging the battery pack.

  21. Dark Sponge says:

    Hello! I’m the person who made this Instructable, and I have some things to say.

    First of all, thanks to whoever put this on Hack a Day!

    I’m pretty sure the charging circuit is built into the battery. I’ve used it for a while with the backlight fully on and never had to charge it. The battery has not exploded.

    The 8.11 volts you saw on the multimeter was in full sunlight in the middle of the day. It’s never been that bright when I charge the DS.

    I have already considered using a 5v regulator, and to do that I would have to wire all of the cells in series to get a high enough voltage for it. with the panels in series, it only produces a maximum of 30 ma. put that through a 5v regulator, and you end up with even less. I would be left with so little current it could probably barely power the charging led, ending up with next to nothing for the battery.

    When there is no light hitting the panels, the battery will not discharge into them because I used a blocking diode on each panel.

  22. thecauseandeffect says:

    im totally going to do this, but actually integrate the panels into the casing so that it is more seemless.

  23. Red says:

    I’d like to see a hack sort of like this for the EEE pc and/or other netbooks out there (obviously with charge controller, etc)… Given the EEE seems to take 12v input, could be an interesting project… any takers?

  24. Dark Sponge says:

    red’s idea sounds cool

  25. mjn says:

    sooo… lots of questions regarding battery protection. Time to clarify some things… Li-ion batteries need essentially the same protection as li-polys. Most chips that are designed to protect one are also designed to protect the other. Depending on how fancy of a chip you get – they’ll protect against these things (among others): over-voltage, under-voltage, over-current, over-temperature, and cell balancing. Laptop battery protection circuits typically protect against all of those.

    This circuitry is built into some packs, not others. I’ve yet to see a modern laptop battery pack without this circuitry. I’ve never seen a cell phone battery with a built in protection circuit. Typically they have a built in temperature sensor – hence the three terminals that most cell phone batteries have. I’ve never taken apart a DS battery – but I highly doubt they have built in protection circuitry. Not in that form factor. No way.

    OK with that out of the way – how do you typically charge li-ion or li-poly batteries? Well – most circuits give them a constant current with a voltage limit. Most packs can handle 1C or higher. So what this means is that you start out charging at your set current but as the pack gets full its voltage approaches the voltage limit and the charge current slowly tapers off.

    Now – this guy’s circuit just connects a current source to the terminals of the battery pack. It is a weak current source, but it still is a current source. This means that he is in fact overcharging his cells, albeit slowly. Will they explode? I bet if you left it out in the sun on a hot day the pack would puff up. He’s certainly doing damage to the pack – but how much is just too hard to say.

  26. Alpha says:

    I love the DS! It’s a hackers dream come true.

  27. RealVision says:

    @Alpha: No, the Pandora is a hacker’s dream come true.. (albeit an expensive dream – but hey, just look at what you get)

    As for protection, I can only confirm that there are, in fact, batteries with no protection at all.

    80mA won’t make anything explode (those things typically charge at 1,000s of mA), but it will certainly damage the cells (ie. they will have a shorter lifespan)… Basically the same mjn said :-P

    (Disclaimer: I design high-power flashlights, so I know the batteries there, ie. round batteries. I assume square batteries are more of the same.. Would be weird if they weren’t)

    (Also have in mind that open-circuit voltage != actual in-circuit voltage)

  28. phishinphree says:

    Just wire in a max1555 between the battery and the panels and your all set.

    Lipos come in all flavors, raw cells, cells w/ under-/over-voltage protection, some have charging circuits however they also have additional leads. So, if your cell only has 2 pins, there is no built in charging circuit.

  29. dext3r says:

    i think you can just hook up a voltage source to the charging port of the DS just fine. You can get USB charging cables and I’m assuming they just provide 5V to the DS. So whats the difference here?

  30. louis ii says:

    Less redundant speculators please.

    People with questions could go to the instruct-able and ask for more details there. That that is where the project and maker/user are active, after all.

    Thank you to the creator of this project for clarifying some of the details on this project by visiting this site.

    Eee PC solar project:
    Yes, there is enough space to put panels on the back side of the display, but it would make the device thicker (bigger) which appears to go against part of the “small ideal” which is one of the Eee’s selling points.

  31. cartufer says:

    i considered doing this myself a few weeks ago and came to the conclusion i could get about 260ma(my genuine charger outputs 320ma) at 5v from solar panels available on dealextreme, the fat ds is good for this as it has significantly more surface, i decided not to solar power my ds because i’m not in the sun enough

    for best results use a usb inline battery backup

  32. Louis II says:

    Potential panels for EEE PC 10″ solar cells:
    http://store.altenergystore.com/Solar-Panels/1-to-50-Watt-Solar-Panels/Kyocera-12W-12V-Mini-Solar-Panel/p718/

    The only real drawback is fairly obvious:
    Extremely low current (amps) will result in very long times to charge.

    Still, if you mounted 2 of these on an EEE PC and wired them in parallel, you could get an effective juice of 12v at around 0.2 Amps… not too snappy for a couple modules, but if the 3 amp output of the DC adapter means anything, that would give an amp hour every 10 hours (less from losses) of direct sunlight.

    I don’t think it’s worth it, really, but it would only cost about $80 to find out, potentially.

    Personally I would look for better modules before settling on those ones. I also might consider a fold-out design of home-made modules (from broken ones, of course) to provide more power than needed, using some charge controlling and blocking diodes to account for other issues that might come up… but that’s not exactly super-portable like the EEE PC intends to be.

  33. Jo says:

    Now it’s a Nintendo DS Light! :3

    But really, I think there’s a greater threat of thermal damage from leaving it in the sun than from overcharging li-ion batteries with 80 ma.

  34. mscir says:

    Sounds like it’s time for … an experiment… ! The same model battery wired with the same solar cells under a spotlight in an attempt to overcharge it would be interesting. A log of the voltage and temperature of the battery vs. time would be even better.

  35. Jude says:

    NOOOO!!!! I’ve been working on this! Ive got it all done, just waiting on the solar panels! but nice to see that someone else was thinking it.

  36. mscir says:

    Hey Jude (hmmm, seems like I’ve heard that before somewhere) funny comment. Yes I love solar powered anything, I’d put solar panels on a hat and run current across my scalp if I thought it would make me smarter! But anyway please let us know how your project goes. It would be good if we could hear some specifics, like a)what % of the charging of your battery was from solar, and how long the battery lasted (vs how long they typically last), and last but not least, if it exploded (heh, just joking). Post a pic of your project if you want, I’d like to see it.

    Best Wishes,
    Mike

  37. AeroMaster says:

    Well I did not think it was possible but the Lithiom Ion Battery isn’t damaged? Also is this safe for an average person to do!? I mean one wrong wire that isn’t connected properly and 1 of 2 things will happen. 130 dollars down the drain (BRICKED DS!!!) or BOOM it shorts out. So my advice even if you have insturctions on how to do it but you don’t know much about these things and how they work. DO NOT ATTEMPT THIS OR THERE MAYBE UNDESIREABLE RESULTS!!!

  38. MCHolden says:

    Guys I just want to throw my experience into the ring regarding the issue of a charging circuit, and just where it is in the system. I have a DS that works fine but will not charge the battery. I have to charge it in another DS when it dies. I opened the faulty DS up last night to see if there was a bad solder joint or other obvious damage. If you look at the mobo where the charging port is, you can see the positive lead of the charging port connects to the F1 (or was it F2? it’s not in front of me now) fuse which in turn connects to an array of resistors, transistors, and diodes, before making it’s way to the positive terminal of the battery compartment. I can only presume this is a charging circuit. So when you plug in your charger, you are not just wiring your 5.3VDC directly to your battery. I agree with the comments above that it probably won’t cause an EXPLOSION at 80ma, but it seems Nintendo has put a charging/protective circuit in there for a reason. I didn’t read the instructable to see where the hacker connected the output voltage of the solar panels. If he connected them directly to the motherboard on the line side of the charging circuit, he should have no troubles. If he wired them directly to the battery terminals then I would say he will slowly but surely overcharge the battery, shortening its useful life. Either way, great hack sir!

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