MagicShine MJ-828 Battery Pack Mod

[Phireglass]

Well i just picked up a MJ-818 tail light which comes with the MJ-828 battery pack with voltage indicator and overcharge undercharge protection. and im goin to most likely get the MJ-880 and run both off this pack, now i know they use (4) 18650s in there. Can i take it apart and put in some AW 3100mah 18650s in there instead? Will it still charge correctly? Im familiar with all the lights, drivers, etc but i dont usually do any led diy type of stuff but this seems easy enough. What do yo guys think?

[find_bruce]

Easy enough to pull apart & replace the cells see Review & dissection of magicshine battery mj-828.

Not quite sure why you would be wanting to use AW cells - whilst they are an excellent choice for use in a flashlight (IIRC they are panasonic 3100 cells with protection added), in the case of 2s2p better protection comes from the PCB which ensures that the two banks of cells are within tolerance. Plus soldering on the end of the cells, while possible, is less than ideal. If I was in your shoes I would be looking at buying panasonic 3100 cells with solder tabs like this

The combination you are loooking at would draw too much current for the standard battery pack, but from all reports using the panasonic 3100 mah cells should be fine.

I assume you are aware that the MJ-880 comes with a 2s3p (ie 6 cell) battery and uses a connector that is not compatable with the usual magicshine connector ?

The other problem with the magicshine set-up is that the charger is pretty crappy. It would be a shame to spend all that money on panasonic cells only for a faulty charger to damage your batteries. After reading this thread I bought a hobby charger which appears to do the job nicely.

[Phireglass]

Thank god someone replied lol, ok the panasonic cells with the soldering tabs is clutch im def gonna order those instead (i just said AW cause i wanna do it with top notch parts)

but you are right the pcb would take care of any protection issues so the AWs are not really nessecary, as for the connector,

i believe the y cable i would use to power both the headlight and tail light would take care of that, i did notice the 880 pack has more of a square connector rather then just the circular one but i dont think it will be much of an issue i could always cut it ane make it work.

Now i have heard of these hobby chargers and thats my main concern is how to charge this pack once i mod it, but i have no clue how i would charge it, theres the pcb board for one and the 4 cells. Once i solder em in i will have to use the existing cord on the pack, any idea how to go about this?

[find_bruce]

i did notice the 880 pack has more of a square connector rather then just the circular one but i dont think it will be much of an issue i could always cut it ane make it work.

The issue is pretty clear if you look at the connectors



Doesn't seem too bad to modify, but apparently it is possible to modify the standard female connector to fit the mj-880. I won't link to another forum, but I am sure your google skills are sufficient to search for modifying standard connector to fit mj-880.

i believe the y cable i would use to power both the headlight and tail light would take care of that

The only thing to watch out for is that the Y-cable has a reputation for using very thin wires - exactly what you do not want when you are running high current draw with a tail light and a double xm-l light.

Perhaps a better option though is to use a cable designed for the mj-880 which should have slightly thicker wires and comes with
Input: MJ-880 male connector.
Output 1: MJ-880 female connector, to be connected to MJ880 bike light or MJ-880 ext cable.
Output 2: Traditional magicshine female connector, could be connected to a tail light.

All you need then is to modify the female connector on your battery

Again a google search for mj880 y-cable should give you plenty of options

Now i have heard of these hobby chargers and thats my main concern is how to charge this pack once i mod it, but i have no clue how i would charge it, theres the pcb board for one and the 4 cells. Once i solder em in i will have to use the existing cord on the pack, any idea how to go about this?

Yep - that's how they are charged. What I did was cut the cord off the junk charger that came with the battery and put a suitable plug on the leads. I got a Turnigy Accucel 6 & could use either banana plugs or XT-60. I chose XT-60 because they can only go in with the correct polarity.

If you wanted to go fancy you could also wire in a balance lead & plug, but it should not be necessary with good quality cells like the panasonics.

A hobby charger needs a bit more care in use - you need to set both the voltage & the charge current, plus it has two good safety features - a timer and capacity limit which helps to stop overcharging cells in the event of a fault.

[Phireglass]

Oh man, you are my savior lol, ok so what have you done to your battery pack? are you just using the hobby charger and running it stock?

I know exactly what you mean in the y-cable situation i may have to fab something up to cope with the current, now you got me thinking of just modding the 880 pack but thats kinda gnarly and pricey, any idea what i should be running when charging my modded pack? (sorry ive just used the wf-139 charger, set it and forget it)

and to clarify, you pulled the old stock charger cord (male) and hooked it up to your hobby charger then to your pack?, what settings are you using on your particular setup? im just trying to get an idea of how difficult its going to be to charge this beast.

And according to the hobby charger link i should be charging at the battery packs mah-70% correct, so if im goin by that it would be a charge current of about 3720mah?

[find_bruce]

Yep that's how my set-up is. I have the standard batteries, but with the addition of a balance lead - I rarely have to balance the pack but I like to be able to put a voltmeter on it to check that things aren't too out of whack. I always planned to replace the cells with panasonics when they fail, but to be honest they have lasted much longer than I expected.

I know what you mean about the mj880 battery - a 2s3p battery is a chunky beast. I think the path you are looking at will give a neater solution, but at a cost - you will be spending something like $50 + just for the panasonic cells.

The stock battery is nominally 4400 mah & because I didn't really expect the batteries to last, I charge is at about 1/2 c, or 2 A. The voltage is set at 7.4 v but yes it does charge to 8.4 v. The timer is set for 180 minutes and the capacity at 5000 mah (I also use a lipo battery of that capacity).

You don't quite have the calcs for the battery pack right - while there are 4 cells, it is 2s2p - 2 in series increases the voltage to a max of 8.4v while 2 in parrallel increase the capacity from 3100 mah to 6200 mah. So -70% is 1.8 A. The recommendations I have seen for the panasonics are 1 A for a single cell, so 2A for 2s2p should be fine. While notionally your charge time would be just over 3 hours, in pratice it is going to be around 4 hours (amps drop off at the end.)

Initial settings I would use for your pack would be lipo charge, 2A, 7.4v, timer 260 minutes, capacity 6200 mah

On that point can I assume you have figured out how you are going to solder the batteries to get 2s2p ?

[Phireglass]

Yep, i know how im gonna solder em in, i was unsure about the charge rate cause they are 2s2p but thanks for the clarification, i just need to find a good source for the panasonic cells, the link you provided to the dude on ebay wont ship to the us but im sure it wont be hard to find, now i just need to go shopping for the cells, hobby charger, and a heavy duty y-cable but im probably gonna fab something up for that, they seem pretty common so i may justbe able to pick one up online somewhere, thanks for all your help, il post a detailed write up when i swap those out with pics and everything