How to use a balance charger

[theECB]

I was wondering if anyone has any experience using a 2 cell balance charger? My question is how to wire it up to the batteries properly. I'm considering the following unit from DX.

DealExtreme: $8.46 Mystery Balance Charger for 2/3-Cell Lithium Ion/Polymer Batteries

I see the 2 cell (7.2v) plug has 3 wires coming from the charger. Could this charge two li ion that are stacked? I'm hoping to use this to charge the batteries inside of the mod, no removal required. If so how, if not, how do you properly wire it? Thanks for the help in advance.

~Erik

 

[Huffheinz]

Sorry, man. I don't know the answer, but you could probably find it on a Radio Controlled hobby forum. I'm an RC guy and I have a charger very similar to that. You could probably find a post on RCgroups that would explain.

 

[Rocketman]

A balance charger needs a connection to the negative end of the stack, each intermediate contact (center of two cells) and the positive end of the stack.
If you are going to 'build-in' this capability then a thin contact disk for each point could be wired to each of the 3 leads and run to a mini usb connector.

What kind of mod did you have in mind?
Balanced cell charging is a great idea for stacked battery mods.
To incorporate it into a mod adds additional wiring and a connector for 3 wires.
You must use NON-shorting 3 terminal plugs (don't use stereo phone type plugs).

Rocket

 

[theECB]

After some research, I believe this is how they work. The wire harness has three wires. One red, two black. So, you hook the red (+) wire to a common connection on the positive sides of the batteries. Then you hook the black (-) wire to each battery end.

The balancer must periodically check the voltage of each cell by disconnecting one of the negative terminals. If the charge isn't full, then it reconnects, and continues to charge both. Once a single cell is at full charge, it kicks off that neg lead (breaking the series) and only charges the other cell until both are at a full charge.

Hope this helps. I plan on making a drop in charging unit once the slow boat from China delivers my new toy!!

 

[theECB]

Rocketman! Here to save the day!

Does this look about right?

 

[theECB]

So, what I want to use this balance charger is a 5v Box Mod. The diagram below represents the battery positioning on my box currently. I left out most of the other wiring cause I just want to focus on what the balance charger needs. So, how does it look?

 

[theECB]

Hope you all enjoy my crude drawing skills. I am a picture guy so I hope this helps someone else "visualize" this mod addition.

Rocketman? Any other ideas on a proper 3 terminal plugs?

 

[Rocketman]

My guess is you could use a mini usb plug/jack (ebay???).
Would have to make sure it was labeled so no one could try and hook up usb power.
Two 2 conductor power jacks could be fitted to mod, center pin of jack one to most positive of two battery stack,
center pin of jack 2 to junction of cells, both negative contacts to negative end of cells.
Wire up a pair of power plugs to match.
Deal Extreme does have a nice price on these, about a third of the cost at hobbylobby.com or towerhobbies.com. Go ahead and order one and learn how to wire one up in the next 40 days (before it comes in)

Theybe cheap but they notbe fast.
Rocket

 

[theECB]

I am resurecting an old thread with hopes of new information. Anyone with experience in charging two batteries in place please drop some knowledge!

 

[Java_Az]

I am working on this right now. About to put the finial touches on my circuit so i can etch a board today. Hopefully have it soldered and working tonight. Did you get that balancer charger and try it ? If it didn't work per your diagram i bet i know why.

 

[theECB]

Java_Az, No, I have not bought the charger yet. I was waiting to determine if it would work correctly before shelling out the dough. Could you please expand on what I could do to make it work correctly?

Are you using additional components to make it work?

 

[Java_Az]

Only reason i see why it would not work is in the batteries. If you use Individually protected batteries i believe your going to trip protection trying to charge @ 8.4 volts. So if you use IMR without protection you should be good or making a pack with a 8.4 volt protection circuit and a couple li ion's. You can stack Individually protected batteries and they will discharge fine but going into that batteries to charge them is a different story.

 

[theECB]

Java_Az, thanks for the feedback. This is very helpful and gives my some good ideas about the direction I should be going with this. Please keep me updated on your progress. I assume the board you're designing incorporates unprotected batteries and an 8.4v protection citruit? Would really enjoy seeing some designs.

 

[Java_Az]

Java_Az, thanks for the feedback. This is very helpful and gives my some good ideas about the direction I should be going with this. Please keep me updated on your progress. I assume the board you're designing incorporates unprotected batteries and an 8.4v protection citruit? Would really enjoy seeing some designs.

I might be wrong about that. When i first started researching batteries i read something about not charging singley protected ones on a 8.4 charger. But after pondering it since i made the above post it might not make a difference. I will have to set up a real world test on my charging circuit to see what happens. The old adage " you cant believe everything you read" might just be true in this case.

 

[theECB]

I was doing some research as well, I think the problem occurs when, especially with the high end balance chargers, the protection circuit on the battery may cut off before the main balance charger is complete. This causes the main charger to believe there is a battery disconnect issue. However, it's kinda like an extra layer of protection so I don't forsee any issues with it. Both situations should lead to a fully charged battery. Well, I guess it's time to buy the dang thing and find out myself huh?

Thanks for your help and guidance Java_Az. Best of luck. Would still really like to see any finished product you may have.

 

[Java_Az]

Trying hard to finish my battery powered mod. Getting pretty close to having it done. It is going to have a 8.4 volt charger in it. Not considered a balance charger though but does have some nice safety features. Only thing i really have to show is a passthrough i made thats ego compatible. works with any 510, eGo tanks , carto , mega atomizers and is also cone-able. I will for sure be posting up pics and maybe a video when my current project is done. Here is a pic of my pass-go with a tank0miser on it .

 

[theECB]

Ah yes, I remember that beauty from a different post. You machines the body correct? Well, keep up the great work. I am just finishing up another mod and will also post pics soon. Happy modding Java_Az!

 

[Java_Az]

Yeah i machined it myself, picked me up a mini lathe a few months back. Good luck on your mod i will be looking out for it. Hoping my order of stainless steel gets here this week so i can crank out some parts i need. With my luck it will be here Monday though.