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I am really confused about the specific instructions required for charging the thin.

I am very curious about why the charging requirements are so strict and what is at risk for failure if the process is not followed.


First, it is very important to turn off the battery switch before charging. Well I forgot to do just that, my charger is hot and the battery didn't charge. Did I cause damage? What is actually being electronically switched within the battery enclosure?

Second, it is important to plug in the charger to AC only AFTER the bike has it's DC jack plugged in.

I really rarely do this. The charging block is bulky and the plug is hard to move. What damage does this cause? This isn't something I have every heard of with other electronics.


I know a little about lithium batteries and charge controllers, I build my own electronics projects and things. These procedures feel weird to me with my experience in DC electronics and probably put in place to cut costs on proper safe electronics.


My overarching question is what are these weak points that require these additional steps, Is it a cheap charger, or charging component within the battery that add's these steps. 

What damage is caused for having the charger plugged in with the battery turned 'ON"

What damage is potential for having the DC jack plugged in after the AC power was applied?




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The short of it is: These chargers are commonly supplied by a lot of ebike manufacturers with there bikes. 

These chargers and batteries will get quit warm when charging; especially during the last 20% of the charge cycle, this is normal, as it with most chargers and batteries of different types.

Remember: It can take 6 hour or better, to fully charge these fully discharged battery. Also: after long rides, these battery becomes quit warm or hot, and the charger will not charge the battery. So; give time for the battery time to cool before charging. I open the door on the battery box and let things cool a bit before plugging in the charger led. This will help heat escape and allows the battery and controller to cool down faster before charging, and will keep allow heat to escape that is created when charging. Heat is the force that degrades battery cells.

 I hope this much helps for now.  I'll add more later with pictures to help answer those other questions.

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Connecting the charger to your battery, when the charger is plugged into the wall outlet, will cause an excessive arc. It might destroy the BMS inside the battery....very bad. You can further protect your battery and the display, if you are using a Luna Advanced charger, by splicing a XT90 spark resistant connector between the male barrel connector and the charger. The displays on the Luna advanced chargers are know to burn out if not treated correctly. I have them on all my chargers and battery to controller connections. I use two batteries on my original sondors and can switch between them, mid ride, by switching connectors and my 52V 13.5ah rack battery is shared by my mid drive Dolomite. 

It has nothing to do with heat.  


if you really want the complete story on connectors: 


Edited by Tabletteer

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Just got my Thin put together and charging it for the first time.  Battery arrived completely dead.  It's 8:00 PM and I just locked myself out of the garage and my landlady won't be back until the morning.  Which means the battery may be plugged into the charger for 12 hours.  I know it's not supposed to be plugged in more than 8 hours.  IS this going to be a serious issue?  Am I going to have to call a locksmith to get into the garage?  

My Rad Power Rad Rover I can leave plugged in all I want.  Is there a charger option out there I can use that will allow me to do that?

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Your charger is automatic shut off, don't worry, the BMS will stop the charging when the battery reaches capacity, but the "WARNING FROM SONDORS", if the charger is still showing red for more than 8 hrs(the max time it could take to charge the battery), means some component has failed to automatically stop the current flow ..... So unplug the charger. Your new charger and battery will shut off fine. 

There are many advanced chargers out there in the market but your stock charger is fine and automatic. If you wanted to charge at lower amp rates, and to a lower capacities; 80, or 90 or 100% capacity, those chargers are available from LunaCycle.com and their general use is to charge to maximize battery longevity.

See : 





Edited by Reddy Kilowatt

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@Eric Zachary Ryder: here's a way to proof yourself against that problem.


Its a mechanical timer, not an electronic one, so it is unaffected by blips, irregularities and perhaps even failures in the power coming out of the outlet.  So charging a battery with a 'dumb' charger that only knows to stop at 100% (by reaching a common voltage that is known to be 'full' for 18650 batteries) is going to work unless something bad happens to the gear.  If the charger fails to recognize the voltage cutoff, the BMS is the secondary failsafe as it will turn the current away before it starts overcharging and setting up the battery literally for a fire/explosion,.  At that point your house's survival is dependent on that little BMS.  Over time you will learn how long it takes to charge your battery.  Set this timer to cut off at about that time.  Before that time to charge less than 100%.


Next, how about figuring out how much charging you have done and need to do?  I have a couple of these:



Plug them in inline between your charger and your battery.  To do this you are going to need to be able to crimp on some connectors.  This meter comes with what you would need for XT60's, but Forget that and buy/use 'xt60 pigtails' (search Amazon you'll find them).  From there, Luna Cycle sells an XT60-to-bottle battery adapter.

Lastly, you will want to know what the numbers on the watt meter mean.  Click on this (I promise I am not rickrolling you although I am often tempted to do this):


This will tell you what the meter readings mean.  You can figure out how long it takes to charge to X% on the battery via experience, then set your cutoff timer to that time frame and job done.

The easy way is to

a) buy one of the two 80/90/100% Luna chargers.  These are good options.  They do fail on occasion though and need fans to keep running to stay cool.  I have two of these.

b) buy a Cycle Satiator from Grin Technologies.  This is the world's best bike charger and it had better be for $300.  At its core it has a lot in common with an LED power supply with a display and fancy programming memory added.  I have a Satiator that travels with me everywhere in my saddlebags.

c) Make your own charger out of an LED power supply.  This has been done for years by the ebike DIY community.  Its probably time I wrote it up here in a special thread.  I have two of these and they are excellent, but they don't create themselves.  You have to know how to crimp together the right wires and adjust the thing within its - and your - proper limits.

... do the above and then use your cutoff timer as a failsafe behind the above.  So if you charge at a nice friendly 1a, and you need to add 5v to your battery to get it to 55.4v (thats 80% on a 52v battery) then 1a x 5v  = 5 hrs of charge time.  Set the mech timer to 6 hrs because your charger will tail off towards the end of the charge cycle and needs more time to finish.  And if it doesn't (i.e. it fails to stop runaway-train style... which I have had happen on a Luna charger), the mech timer will kill the process after 6 hrs so your battery will be at 56.4v which is still well under its 58.8v 100% max.

Edited by MattRobertson

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