Charge in series.

[Trendkilla254]

So in the new host I am working with I won't have access to the batteries. I want to make a charging port for 2x 18650's wired in series. Does anyone have a good configuration or know how I can wire this up for charging?

Found this Link I assume it is the same for Li-Ion.

 

[Benm]

It's a bit tricky.

You can charge 2 cells in series just from the outermost connections, ending the charge at a total of 8.4 volts for the pair etc.

The downside is you can get problems with imbalance between the cells, where one is already full and the other is still discharging and such. Using protected batteries doesn't make this better: the 'good' protected cell will cut out of circuit when full, leaving no path for current to go through the other one that isn't full yet.

The upside of protected cells is that the weak cell will not over-discharge or even become reverse biased since its protection will open the circuit when the cell voltage drops too low.

Given all of that: yes, you can do this with protected cells to some degree. You could top up or recharge 2 cells in series from only the outer terminals several times without much of a problem.

You should, however, take them out and charge them individually every say 10 cycles or so to keep them balanced.

The only way around this is to build the charge circuit into the unit with access to the middle tap that interconnects the cells. It seems this is not possible in your host, so i'd go for the charge in series, take out to balance once in a while approach. This should be fine for a host that has a charge connector but also removable batteries.

 

[Cyparagon]

The only reliable way to do this is to balance the cells while you're charging them. Most series chargers will have extra terminals for the "center taps" and you'll need to make these taps available to the charging port. You can also build a balancer into the battery pack itself.

 

[Trendkilla254]

Alrighty, thanks for the input yall. I decided to solder in the Balance Plug. I took the center tap wire and split it into 2 wires. I then made two separate connectors for each battery that way. I'll then take and make a plug for it to just use 4 alligator clips to attach to my normal 18650 charger, that or my Li-Po charger for my R/C might do Li-Ions also, in that case I'll buy a JST-XD connector. Either way Now that I blew up my PL-450 diode being stupid I'm not sure I'm going to continue with this host or start over completely. I was originally going to put it in an old small cordless screwdriver I had. I'm thinking now I'll just get a Nerf Gun and paint it really nice. I wanted a "Laser Gun" now that I have my 5mw Light Saber Done. I want it to be small though. I want it to be usable as a pointer. I think my project just got bigger by destroying the diode. I may end up getting the small nerf gun that has 2 barrels. Take out one barrel for the 445nm NDB7242E I just bought, and Maybe I'll add an additional safety switch for another diode for popping balloons. I dunno about the latter though. I've not really been into burning and I can't say that it's the most appealing thing to me. "I just like the pretty colors." I'm also waiting to see that new RGB host that Ehgemus has been working on for someone. I'd be really interested in scrapping this whole LaserGun project for that.