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Battery Dead?

I have a Sondors Thin that has been working fine since I bought it over a year ago in May.  Today it wouldn't turn on.  I have the Luna LCD and it would flash for a half second then go dead.  The battery test LEDs on the battery itself will not light either.  I tried swapping batteries to my wife's thin (with no LCD) and it does the same on the throttle LEDs (flash for 1/2 sec then nothing).  It's been charging all day.  All connections have been triple checked.  Is it a goner?  And if so, what options might I have to repair or replace... this is my commuter bike! Thanks

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Do you charge the Thin Batteries by first tuning the battery power switch off, then unplugging the 4 pin battery to controller connector, plugging the charger into the battery and lastly plugging the charger power  cord into the outlet? Does the charger lite initially turn red, remain red or immediately turn green? You'll need to check the output of the charger with a multimeter. Is should read about 42v DC. Check the battery voltage. It should read about 41v for a fully charged battery, less than 32 and it won't power the controller. Whichever reads defective with the meter is  what needs to be replaced...

Battery replacements at Sondors.com Parts page or for an upgrade  here. https://electrobikeworld.com/products/lt48-48v-14ah-lithium-ion-battery


Chargers here: https://lunacycle.com/batteries/chargers/ 




Edited by Reddy Kilowatt

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Love the pup & thanks for the help.  

Because I had one dead battery and two Thins, I was able to isolate that it wasn't a controller or charger issue.  The battery showed 0 volts on the multimeter.  

Here's what I think the problem is...  on a whim, I flipped the switch on and off a dozen times (because for a fraction of a sec after I turned it on, I would get my LCD to react).  By doing that, it stayed on, which leads me to believe I have a defective switch on my battery.  Has anyone else experienced this?  

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I've even thought of building a fat tire sidecar for one of my Sondors,  so my Boy (Fly from Canada) and Girl (Gwynn from Wales UK) Border Collies can ride with. 

I have not seen anyone post that problem here but it will now be a trouble shooting item when dealing with these type of issues. Some electrical contact cleaner might eliminate the problem unless you can feel and obvious mechanical difference between the good battery switch and bad, indicating a mechanical , failure/defect. We have found bad solder joints in the battery cradle power leads, even within the motors. 

Good find on getting to the root of the problem and you should contact CS on Sondors.com and even though out of warranty ask for their advise,  about switch, battery replacement or repair, and at the least, they might have a source for a new switch, at best a battery exchange for new. 



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I just bought another sondors original fat today...got it super cheap cause the battery was dead, I mean like 1.4v total at terminals on bottom of battery.  

So I tried this....

1. LED stayed green on the charger...yes it was putting out 41v still nothing at the battery 

2. The BMS won’t let the charger feed the batteries due to low voltage. 

3. This is where the magic happens. Remove the LED status indicator top off the battery, pull up the cap and you’ll see 2 small wires 1 red and 1 black going to the status light, cut and strip wires ( be sure make it clean you’ll be resoldering these) strip each wire back enough to attach alligator clips to each lead. Now hook those wire up to your charger( I used back probe leads and clips, just make sure you no sparky) you’re now bypassing the BMS and can safely feed power to the cells.

set a timer for 1hr, test the terminals for the voltage, with in 1 hour you should see 34-36v. 

Now test the normal charge port on the battery, should now turn red and start a normal charge cycle. 

I see a lot of people having the same issues and thinking they need a new battery..18650 cells are pretty tough and should just go bad sitting around. This particular battery wasn’t used for 10 months and now is back to full power. 

Just thought I’d share my 2 cents! 82FE9D05-D167-48FB-AB25-2F8908E6E43D.thumb.jpeg.e4fa924a66ef68b43ab7fffa38a672b1.jpeg

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Nice work.  The BMS is usually the culprit on these and I have not until now seen instructions on how to get past it and force a charge in.  Similar practice for re-igniting a car battery... today's smart chargers won't do it so you have to have an old-school charger in the garage and hook that up until you force feed juice in the battery to fool the modern smart charger into getting off its butt and doing its job.  At that point the smart part of that charger will take over and it will bring that battery back to life.

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