DIY Battery Repairs for 808 Clone?- Mtbr.com
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  1. #1
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    DIY Battery Repairs for 808 Clone?

    Picked up two of these: http://www.amazon.com/gp/product/B00...ilpage_o07_s00 a little more than two years ago, and while lightly used (maybe 10 rides with 'em?), they've been solid up until now.

    When riding by myself, I'll typically run them on low and have never had an issue running them over an hour. Racing, everybody else has their lights on as bright as they go, so I've run mine on high so they don't get washed out.

    Again, solid, until Friday - night XC race. Right around 1 hour in, my helmet light (battery in jersey pocket) shuts off. Very close to the end, so I just rode it out.

    Once I stopped, I could see that the LED on the back of the light wasn't lighting up at all. swapping batteries made it look like the one battery was dead/bad - both lights would power up just fine with the other battery.

    Tried re-charging it for giggles, and it seems to be working again...

    I'm doing a 50-miler in October that will run into night, as well as racing a 25-hour as part of a team, so I need some solid lights.

    So, where do I go from here?

    I assume step 1 is to check the 'fully charged' voltage, then step 2 is probably to open up the packs to check for any physical evidence?

    From there? Pick up some 18650 cells and build new battery pack(s), reusing the connectors and PCBs?

    (I generally guess right which end of the soldering iron or multimeter to hold, but I'm no expert either... I'm guessing these packs are 2S2P configuration, thinking I *should* be able to go 3 or 4 in parallel to get more runtime, right? I'm assuming the existing PCBs probably wouldn't handle those configurations well though?)

  2. #2
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    Your 2S2P battery pack is probably heavily unbalanced. You should measure the voltage just after full charge. If it doesn't come close to 8.4V then this is the case. Report it back.

    If unbalanced you need to open the pack and see which of two pairs is lower than the other. You need to chage each pair with 4.2V charger or use hobby charger to balance the pack.

    About building new pack you might get some ideas here-> http://forums.mtbr.com/lights-night-...gb-982688.html There is much to read..... but you can ask more afterwards.

    For your lights PCM from your existing pack should be sufficient. Not necessary if you use more powerfull lights.

  3. #3
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    ran both packs full on the chargers last night and then measured them with the DMM - both right around 8.22V - I'm guessing that's close enough to 8.4 to assume they're not super unbalanced?

    Thanks for the link, that give me a bit better understanding.

    Looks like I may need to rig some stuff up and do run-time testing to see if one of the two battery packs really is going dead a lot sooner than expected...

  4. #4
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    No, 8.22V is to low. I was thinking about difference in hundreds (0.01V) for exmple 8.35V or so. I would suggest to open the pack and measure the votage of each pair. You can easily fix it back with duct tape.

  5. #5
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    Ok, I'm most used to field troubleshooting car electrics where +/- .5V is typically "good enough"...

    I've only got the 8.4V charger that was included with the lights - seems like the easy answer for charging the pairs individually is to go ahead and pick up a hobby charger now? I haven't actually looked for a "standalone" 4.2V charger, but I'd assume any of the hobby chargers can be made to do it, and will be all set for me to add a balance plug later on as well. (And, in the grand scheme of things, the hobby chargers aren't terribly expensive either)

  6. #6
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    Hobby charger is good to have and could be used for charging variety of batteries and packs. But it won't solve the problem with bad cells. It would just help you to balance the pack and make it run just little bit longer.

    Measuring the voltage after one day rest would also tell something about cells in the pack. If the voltage drops more than about 0.05V, the cells are very likely bad quality.

    So first to do is identify the cells and then decide it is worth to use them or is it better to get high quality cells. On the long term (5 years) last one is the cheapest way to go.

  7. #7
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    after ~36 hours, the "bad" pack measured at 8.20V, the "good" one at about 8.15V.
    Only difference being that the "bad" one sat at home all day, while the "good" went along in my bag "just in case" - but didn't need to get at 'em.

    Went ahead and opened the 'bad' one up - definitely unbalanced with one pair at 4.05V and the other at 4.18V if I remember right.

    Packs look very similar internally to the gearbest packs from your first link:



    Seems like a good option would be to use the "Xiaomi Pocket 10000mAh Mobile Power Bank" from your link to build 2S3P packs. Obviously I could just pick those up, and yank the protection PCB and cord off these - but, if I'm understanding correctly, it would be best to add the balance charging plug to those as well?

    I'm wondering if it might make more sense to add the balance plug to these packs and keep them around as spares/shorter-lifespan-packs? Then I obviously need to get protection PCBs and cords for the new packs, and 10s of searching makes it look like buying those separately won't be any cheaper than the gearbest packs you tested - which kind of puts me back at square 1, just toss the cells I've got...

  8. #8
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    Lately I'm seeing a lot of those pink/purple/violet cells in a cheapo pack. From the picture I would say yours is more violet than purple/pink. Can you confirm the tint in compare to mine from Gerabest pack?
    Violet ones can have a little bit more capacity than pink ones, but bigger difference in voltage.
    If you want to have peace and working pack for next 5 years (with proper care) then go Xiaomi route. It is cheaper than buying cheapo pack each year. You can take only 4 cells from Xiaomi, make 2S2P and have 2 cells for handheld lights. Or make 2S3P if the weight is not big constrain.

    Otherwise about those cheapo pack you can still live with them if you take care and balance them frequently. You can use them for short rides, testing, ..... You can even remove protection if you are going to charge them with balance charger each time.

    PS. in case of Xiaomi set you can use cheaper PCM than I did. I was naively thinking balancing feature would work and wanted to make pack "set and forget". Still think if you are going to use higher powered lights you need more poverfull PCM up to at least 4A. As long are you using 1-3 leds lights about 2A could be sufficient (but no gatrantee).

    About balancing plug and good cells. Not neccesary if you check voltage once or twice a year and balance if neccesary. If you use Gearbest case there is room for balance plug inside so you can add it othewise just improvise with aligator clipps when you need balance them. I'm going to seal those packs only with black duct tape so anytime I can open it and check.

    Now it's up to you to choose.

  9. #9
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    ledo, can you (or anyone else) confirm the wiring order on a 2S JST-XH balance plug?

    It appears I have made the mistake of assuming the ones I ordered had the colors in the right places, and that red was (+). Now that I do some additional searching, I find this:


    Same order for 2S, just w/o the green wire?
    (mine came red/black/yellow from top to bottom, I guessed [correctly?] that the middle wire goes to the middle of the series, just got +/- wrong, whoops... )

  10. #10
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    You should find pictures on the net. Yes there are 3 wires and you got wrong colored wires. Very likely you have those. Please confirm. Correct would be black, yellow, red. Red on yours is very likely at correct position, yellow and black are misplaced.
    It would be better to have those ones which have correct setup.

    Yes of course middle one goes to the middle point in series, black on - and red on + (but not on the output side of the PCM, if you are in doubt). Anyway just take a picture you posted and connect wires by analogy you see on the picture.

    For all, it would be good to read this article: All about lipo balance connectors - TJinTech

  11. #11
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    I ordered these one in particular: http://www.amazon.com/gp/product/B00...ilpage_o00_s00

    And their picture reflects how they were delivered; with the "hook" on top of the connector and the wires to the right, they are red, black, yellow from top to bottom - so none of them are in the right place!

    This also explains the puff of smoke that came out of the traxxas charger when I plugged one in...

  12. #12
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    To bad. I hope the charger is not damaged or it desn't have wrong polarity protection.
    You probably didn't looked my other thread about battery packs. You would see the cketch I've made:
    Name:  1008510d1439575632t-review-4-2s2p-6-cell-2s3p-hardshell-waterproof-bicycle-battery-packs-gb-2s2p.jpg
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    I thought you have the same wiring as the Garry got - see somewhere in the middle of: http://forums.mtbr.com/lights-night-...-982688-2.html
    There were only yellow and black missplaced and the red one was correct. You can realign them to be correct, but you need to bent down small hook in order to be able to get wire out. Then befor realign them you need to put that hook upwards again otherwise wire won't stay in the connector.
    Hope it helps you somewhat.

  13. #13
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    pretty sure the charger is toast at this point, a little disappointing that a $35 charger for my car has "wrong polarity protection" and a $18 RC charger doesn't.

    Oh well, that gave me a chance to upgrade to a real hobby charger instead...

    and looking at Garry's pic:


    Reverse the Red and Yellow, and that's how mine came...

    My bad for not doing my research ahead of time. Connectors look easy enough to re-pin though.

  14. #14
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    When buying hobby charger don't go cheap route. Either it's not accurate or it is bad quality. I have iCharger 106B+. I'm shure you can find cheaper solution, but don't go to low.

  15. #15
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    yeah, there's definitely a wide range out there. first try was a little traxxas unit that just did 2s or 3s via the jstxh plug. I just ordered a Turnigy Accucel 6 (from Hobby King, so hopefully it's not a bad copy), hopefully it does the job.

    not wiring the batteries backwards will probably help too...

  16. #16
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    Yes Accucel 6 is quite good one. Could be better, but will do the job. Not shure if they changed the firmware to be able to calibrate it. It is nice to have PC link so you can monitor charging/discharging process.

  17. #17
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    There's a couple things I need to point out, some chargers/packs the red and black wires are reversed. My estation charger is that way, comes with adapters for packs that are wired normal. But it tells me that its not correct polarity so I can switch it and go back to charging. Except the wall chargers that come with lights as they are simple systems, I dont use cheap chargers for balancing just for that reason. I know nothing will get damaged and things will be balanced properly.

    All that said, I just toss cheap Chinese packs, not worth the hassle imho. Ive already had one that discharged 1 bank down to nothing while other bank was almost full. Protection didn't do crap.

  18. #18
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    Got everything buttoned back up and balance-charged, and the results are pretty disappointing - only one runtime test after balancing so far, but the times (55 minutes for one pack, 1:55 for the other) are right in line with what they were like without the balance charging.

    I did receive my powerbanks yesterday, so there's an upside.

    The PCB's that the original packs have - any idea what they really do? Can I just wire up the new cells without any PCB, as long as I'm only using the hobby charger to charge them? Or is there some additional protection during discharge that the PCB provides?

  19. #19
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    Actually that PCB isn't so much for charging protection as discharge protection. If the light itself doesn't have any for of protection built in, id say its extremely dangerous not to have the PCB. If you discharge your pack to far and then try to charge alot of nasty things can happen. From toxic fumes being released to pack exploding.

  20. #20
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    Quote Originally Posted by tigris99 View Post
    Actually that PCB isn't so much for charging protection as discharge protection. If the light itself doesn't have any for of protection built in, id say its extremely dangerous not to have the PCB. If you discharge your pack to far and then try to charge alot of nasty things can happen. From toxic fumes being released to pack exploding.
    That's what I was worried about.

    Assuming I don't just yank the PCBs off the existing packs (very tempting, but at the same time they ARE working, and I do have upcoming night races, so it's very much a "bird in hand vs two in the bush" situation), something like 7 4V 2s LI ION LI PO Battery Protection Balance BMS PCM Current 4A 2S4AW005 | eBay from hunk lee should be sufficient?

  21. #21
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    Tig, you are exagerrating a bit. First he would have one of the best cells on the market. Next, discharging to much affects only to the capacity. It is charging part of cycle when things mostly goes wrong. Charging with high current won't work well anymore. Using hobby charger would probably mitigate most of the threats. Specialy when balancing would be used.

    FYI, I'm happily using few packs without protection. Of course I check the status of the cells very often and "I know what I'm doing" (I think someone said this before )

    Of course it is not bad practice to use PCM and I would suggest to use it for any users. In this case the user should be aware of limitations of existing PCM. Very likely it won't stand higher currents. Good enough for 2-3 led lights, but very likely won't stand more powerfull lights. It is just good to know that and not blaming batteries afterwards. To get over this the Hank Lees PCMs are way to go. If he would use hobby charger from time to time I would suggest to use cheaper PCM like this: 2pcs Protection Circuit Module PCM FOR 2s 4A 7 4V LI ION LI PO Battery 2SW003 | eBay if he would stay in 4A range. To support more powerful lights in the future I would go with 2S2P 18650 7 4V LI ON Battery Protection Circuit Module PCM FOR Bike Light A37 | eBay or 2pcs 7 4V 2s LI ION LI PO Battery Protection Balance BMS PCM Current 7A 2S7AW006 | eBay

  22. #22
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    I share "worst case scenario". Ya its exaggerated for sanyo/panasonic cells BUT you have to think of the tons of people that read this then think its ok to run unprotected regardless of cell brand. Even Panasonics aren't immune to over discharge followed by attempted charge leakage and failure. Been there, done that just to see what would happen. They can and more than likely will start to leak a toxic substance if that occurs. Cheap cells on the other hand (though rare occurrence now after the disasters of the past) can go critical and cause a fire.

    Look at how many people just dont know these things that post in the light forums, imagine the 100s-1000s that read it that we dont see. Best to post worst case scenario so people understand the risks of running unprotected.

    That said, my 3s2p pack I made for my DIY has no protection, but installed balance lead and pre balanced for 24hrs before assembly. But my custom driver has low voltage step down/warning and cut off (button pushes can over ride the cut off in an emergency)

  23. #23
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    pulled pcbs off the existing packs, soldered everything up with the LG cells out of the power packs, got one of them charged and ran a burndown test last night...

    7 hours on high power!

    Pretty surprised, but definitely pleased at the same time.

    Most surprising was the red 'low battery' light though - in my tests with the old packs, it always came on 4-10 minutes before the light shut off completely.

    With the LG cells - 3 hours of red light! Frankly a little less useful to have it come on so close to 50%, but what a difference.

    Looks promising for me to do an evening race this friday, just in the nick of time. More charging and testing tonight...

  24. #24
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    There are at least two explanations for that long lasting red. The light driver is set to some voltage treshold when turns to red.
    This treshold is probably set to work with an old pack. That one had low quality cells and has very steep discharge curve. Not surprising. The voltage is falling down so quickly it turns off very soon after red.
    The second possible thing is voltage drop because of resistance ie. looses in the (probably) to thin wires and the voltage treshold is reached to soon while there is still plenty of juice in the cells.

  25. #25
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    Im with ledoman, im gonna say option 2, the driver is set for poor discharge curve of stock pack. I know mine does the same thing simply based on the quality of cells. I tore down stock pack and charged cells, used in solarstorm case and saw same thing. Stock cells once they went red burned down fast. Panasonics sat in the red forever (I finally gave up waiting). If you can track with dmm, see what voltage it goes red.

  26. #26
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    Let me ilustrate. I've took HKJ komparator as a source. Let say the treshold is set to 3.6V. I've used red line to mark it. I think you would easily understand the graph.
    DIY Battery Repairs for 808 Clone?-cellscomparation.jpg

  27. #27
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    thanks guys - I felt Like I understood pretty well, but the chart definitely seals the deal. I'll definitely be running a few more burn-down tests to get a good idea, but if I know that red light = 2.5 hours left (or whatever), then that is what it is and I can definitely deal with that.

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