Results 1 to 17 of 17
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jun 2008
    Posts
    2,238

    Sudden short run time on two batteries

    I have been running two clones on my night rides. On my two most recent rides, both batteries cut out around 45 minutes or so into the ride. Knowing the kind of quality issues people have had with these batteries, I wouldn't be surprised to have one battery crap out, but to have two batteries have the same issue at the same time is kind of weird to me. One battery is a couple years old and the other is only about a year old. When I charge the batteries, they juice up in about an hour, which is quite a bit shorter than I'd expect on a depleted battery. I only have one charger. Is it possible the charger is cutting out before the batteries are reaching full charge? Any other ideas or things I could try before buying new batteries?

  2. #2
    mtbr member
    Reputation: tigris99's Avatar
    Join Date
    Aug 2012
    Posts
    2,529
    Besides trying a different charge (the cheap chargers can do all kinds of stupid stuff) nothing else you can really do. But if your constantly running them till the protection cuts them off then good chance their bad.
    Trek Marlin 29er

    Like It, Love It, Want Some More Of It!

  3. #3
    mtbr member
    Reputation:
    Join Date
    Jun 2008
    Posts
    2,238
    The batteries have rarely been run to shut-down. Other than the past couple rides, they've only reached that point once when I was testing run time and maybe one other time. My rides are usually only around an hour, so they usually have juice left over.

  4. #4
    mtbr member
    Reputation:
    Join Date
    May 2005
    Posts
    2,506
    Measure the pack voltage when the charge is done. Depending on how you batteries are configured, they should be 4.2V or 8.4V. If they measure like 4V or 8V, then your charger is shutting off too soon.
    GoPro adapters for bike lights http://www.pacifier.com/~kevinb/index.html

  5. #5
    mtbr member
    Reputation: garrybunk's Avatar
    Join Date
    Feb 2014
    Posts
    568
    It's also possible that the cells have come out of balance. Your charger may then reach "full" when the first cell reaches 4.2v leaving the second (or others) cell lower. This was the case with my GearBest 3X light I reviewed. I think I posted pics showing how I individually charged them with a 4.2v charger to rebalance them. Are you willing to carefully tear open the pack (the heatshrink wrap) and measure voltages of individual cells? (I'm assuming you have a standard 2S2P 4 cell pack.

    -Garry

  6. #6
    mtbr member
    Reputation: garrybunk's Avatar
    Join Date
    Feb 2014
    Posts
    568
    Here's the link to the GearBest 3x light. Toward the end of the first post you'll see the pack teardown and my "rig" for charging/testing cells individually:
    Review: GearBest Triple XM-L2 3 Mode Bike Light

    -Garry

  7. #7
    mtbr member
    Reputation:
    Join Date
    Jun 2008
    Posts
    2,238
    Quote Originally Posted by Vancbiker View Post
    Measure the pack voltage when the charge is done. Depending on how you batteries are configured, they should be 4.2V or 8.4V. If they measure like 4V or 8V, then your charger is shutting off too soon.
    The 4-cell pack was reading 7.7V and the 6-cell pack was reading 6.5V, if that provides any clues.

  8. #8
    mtbr member
    Reputation: tigris99's Avatar
    Join Date
    Aug 2012
    Posts
    2,529
    Is that charged or after use?
    Trek Marlin 29er

    Like It, Love It, Want Some More Of It!

  9. #9
    mtbr member
    Reputation:
    Join Date
    Jun 2008
    Posts
    2,238
    Quote Originally Posted by garrybunk View Post
    It's also possible that the cells have come out of balance. Your charger may then reach "full" when the first cell reaches 4.2v leaving the second (or others) cell lower. This was the case with my GearBest 3X light I reviewed. I think I posted pics showing how I individually charged them with a 4.2v charger to rebalance them. Are you willing to carefully tear open the pack (the heatshrink wrap) and measure voltages of individual cells? (I'm assuming you have a standard 2S2P 4 cell pack.

    -Garry
    I read your post a while back. I don't know if I have all the equipment/expertise to perform surgery on the packs (one 4-cell, one 6-cell). I do have a multimeter, so I guess I could open them up and check cell voltage if that's all it takes. Not sure what I would be able to do after that though.

  10. #10
    mtbr member
    Reputation:
    Join Date
    Jun 2008
    Posts
    2,238
    Quote Originally Posted by tigris99 View Post
    Is that charged or after use?
    Fresh off the charger...

  11. #11
    mtbr member
    Reputation: tigris99's Avatar
    Join Date
    Aug 2012
    Posts
    2,529
    Sadly you don't have another charger because before doing that id check them on another charger first. That low of voltage doesn't sound like cells to me, they should be about 8.4 on a dmm fresh off the charge. But dead/unbalanced cells will just loose serious run time on the pack.
    Trek Marlin 29er

    Like It, Love It, Want Some More Of It!

  12. #12
    mtbr member
    Reputation: garrybunk's Avatar
    Join Date
    Feb 2014
    Posts
    568
    What's the voltage you measure coming from charger just plugged into the wall? (Just watch you don't short it out.) Charger should output close to 8.40v.

    If you have a chance to try another charger I would. If you unwrap the packs & check voltages you can just wrap it back up with electrical tape. Not much danger to it so long as your careful with your test leads (it's easier than measuring voltage out of the charger!).

    -Garry

  13. #13
    mtbr member
    Reputation:
    Join Date
    Oct 2009
    Posts
    604
    Odd that there is such a variance between the two packs yet both are lower than usual. Something is definitely off and the charger is at least part of the problem I would think. Im wondering if there is an intermittent short somewhere in the terminal or cable causing it to stop at a random point that's not voltage related

  14. #14
    mtbr member
    Reputation: Cat-man-do's Avatar
    Join Date
    May 2004
    Posts
    4,185
    @ OP,

    Step #1 ) If you have a cheap Chinese charger buy another charger ( or borrow one from a friend ) . My bet is that it is just the charger that is causing the problem. When you get a new one you might want to also buy a surge protector just in case a surge in line voltage took out the first charger.

    Step #2 ) if the new charger fixes the problem, "Buy another one for back-up". When it comes to inexpensive electronics it always pays to have back-ups.

    It also pays to have a back up plan for any night ride. Personally, I take this idea to another level. Along with my two main lamps ( and batteries ) I always have a small 18650 battery torch on the bars just in case I forget a battery or forget to charge something ( or if the main bar lamp fails ). Along with the 3-mode XM-L torch on the bars I have an extra 18650 cell in my bag. Add to that I always carry a mini EDC AA-torch ( XP-G2) in my pocket for repairs. Lastly, if I'm using a cheaper Chinese lamp on the helmet I'll also carry along another 18650 ( XM-L2 ) torch for the helmet just in case something fluky happens to the helmet lamp and it stops working.

    Sometimes crap happens. Just a couple weeks ago I forgot to bring one of my main batteries. While I could of done the ride with just one lamp it was not necessary. I took the battery for the helmet and used it for the bar lamp. I then took the helmet lamp off and replaced it with my back-up helmet torch....problem solved. Rare that I forget to bring something but it happens and yes it has happened before. No doubt it will happen again.

  15. #15
    mtbr member
    Reputation:
    Join Date
    Jun 2008
    Posts
    2,238
    Quote Originally Posted by garrybunk View Post
    What's the voltage you measure coming from charger just plugged into the wall? (Just watch you don't short it out.) Charger should output close to 8.40v. -Garry
    Charger reads right at 8.40V or maybe 8.41V, I forget. I'll try a different charger. I just don't want to start buying stuff all willy nilly. I have a limited biking budget at the moment.

    Quote Originally Posted by Cat-man-do View Post
    It also pays to have a back up plan for any night ride. Personally, I take this idea to another level. Along with my two main lamps ( and batteries ) I always have a small 18650 battery torch on the bars just in case I forget a battery or forget to charge something ( or if the main bar lamp fails ). Along with the 3-mode XM-L torch on the bars I have an extra 18650 cell in my bag. Add to that I always carry a mini EDC AA-torch ( XP-G2) in my pocket for repairs. Lastly, if I'm using a cheaper Chinese lamp on the helmet I'll also carry along another 18650 ( XM-L2 ) torch for the helmet just in case something fluky happens to the helmet lamp and it stops working.
    Yeah, the first time my lights went out, I forgot a back-up. The bar light went dark, and I was just going to hit a downhill section before doing a short jaunt up to my car. I was less than half-way down the hill when my helmet light went out. Total darkness. I hit the brakes fast. Luckily, I had quick access to the road where my car was parked.

    I thought maybe this was a fluke or that I hadn't charged my lights up before putting them away the time before, but I made sure to carry my Serfas True 250 (my commuting light) just in case. When the other two lights went out, that Serfas was awfully dim, but at least it got me out to the road and back to my car.

  16. #16
    mtbr member
    Reputation: garrybunk's Avatar
    Join Date
    Feb 2014
    Posts
    568
    Hmm . . . would love to hear what individiual cells measure . I'm placing my money on either faulty protection circuit (cutting off early) or more likely cells out of balance (perhaps 1 or 2 with very little capacity while other 1 or 2 still decent). Or perhaps all the cells have had their capacity drop significantly (still doesn't explain the odd voltage off full charge though).

    Here's a link to a decent Chinese 8.4v Li-Ion charger (thanks to ledoman): http://www.ebay.com/itm/141317775310 . Pickup a couple as spares.

    -Garry

  17. #17
    mtbr member
    Reputation: Cat-man-do's Avatar
    Join Date
    May 2004
    Posts
    4,185
    Quote Originally Posted by garrybunk View Post
    Hmm . . . would love to hear what individiual cells measure . I'm placing my money on either faulty protection circuit (cutting off early) or more likely cells out of balance (perhaps 1 or 2 with very little capacity while other 1 or 2 still decent). Or perhaps all the cells have had their capacity drop significantly (still doesn't explain the odd voltage off full charge though).

    Here's a link to a decent Chinese 8.4v Li-Ion charger (thanks to ledoman): http://www.ebay.com/itm/141317775310 . Pickup a couple as spares.

    -Garry
    Garry, I'm sure there could always be other problems with the batteries ( depending on how cheap they are ) but the fact that "both batteries" are doing the same thing at the same time has to be more than coincidence. If both are using the same charger that is the common element. Replace the charger and if that doesn't bring both batteries to at least 8 volts ( and provide at least a couple hours of runtime ) than something else is going on.

Similar Threads

  1. my favorite short clip of all time
    By akiracornell in forum All Mountain
    Replies: 22
    Last Post: 03-18-2015, 06:44 PM
  2. two batteries/one light run time...
    By jvossman in forum Lights DIY - Do It Yourself
    Replies: 5
    Last Post: 03-04-2014, 06:50 AM
  3. Time is getting short.......
    By JeffSkisMontana in forum Pennsylvania
    Replies: 9
    Last Post: 05-23-2013, 07:27 PM
  4. Magicshine Run-time with new GeoMan batteries?
    By FishMan473 in forum Lights and Night Riding
    Replies: 4
    Last Post: 09-26-2011, 08:20 PM
  5. magicshine repaired but short run time???
    By kicky1 in forum Lights DIY - Do It Yourself
    Replies: 18
    Last Post: 06-04-2011, 08:15 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •