Hobby charger and Multiple Loose cells...

[kramer5150]

I want to set up a 2 cell and a 4 cell balance charging tray for multi-18650 charging. I tried the search tool and that came up empty. Can someone post pics or a schematic of your trays ? thanks.

*EDIT*
With some education and further research I have realized that my goal is to charge multiple identical loose cells (Lithium Ion) in the same tray. Hence a balance charging tray is not really what I need.

FWIW here are pics of my charger.

Current single cell arrangement.

*EDIT*
I just need to DIY a parallel tray using how ever many 1xcell carriers I want.

:thinking::thinking:

 

[Billy Ram]

Re: Help me make a balance charging tray...?

I'm thinking you may want to contact LuxLuthor and see if he can supply you with his magnet type balencing leeds. Or get the magnets and solder some leeds your self but I hear it's kind of a art. I'm going to just get them from Lux my self.
Billy

 

[Norm]

Re: Help me make a balance charging tray...?

Voltcraft Li-Ion Battery Holder - Newbie Modding Guide
Norm

 

[rmteo]

Re: Help me make a balance charging tray...?

Since you are working with loose cells, you can just charge them in parallel.

 

[Black Rose]

Re: Help me make a balance charging tray...?

Since you are working with loose cells, you can just charge them in parallel.

...and set the number of cells to 1, correct?

 

[rmteo]

Re: Help me make a balance charging tray...?

...and set the number of cells to 1, correct?

Yes. Balance charging is necessary for assembled series-connected packs where you cannot get to the individual cells. Set the charge current to (No. of cells)*capacity. In the example shown below, I set the charge current to 4.8A - assuming that the true capacity is closer to 600mAH than the claimed 1000mAH.

 

[eyrich74]

Re: Help me make a balance charging tray...?

Won't charging in parallel hide poor performing cells?

If you have the capability to do balance charging why not do so and then look at how much work the balancer did to see if any batteries are bum.

 

[rmteo]

Re: Help me make a balance charging tray...?

Yes, it would. But then you would have to muck around making one these charging trays. The main reason these hobby chargers (I have always wondered why they are called hobby chargers when they do so much more than the other professional? types) have the provision for balance charging is two-fold:

1. Battery packs are series connected to get the higher voltages needed - you do not have access to the individual cells' contacts.
2. They are operated at far higher power levels than seen in flashlights - up to multiple kilowatts.

For example, lets say you are using 2 of these in series (12S1P, 44.4V, 5000mAH, 40C discharge rate):

The total out is 44.4Vx200A = 8880 watts at rated 40C output. This is equivalent to about 3,200 CREE LED's driven at 0.750A - typical of a 150-200 lumen flashaholic light (or 260+ SST-90's). At these power levels, charging/discharging unbalanced cells can be hazardous to your health to say the least - hence the need for balance charging the battery packs.

 

[Data]

Re: Help me make a balance charging tray...?

You could build one of these with only 4 stations.

 

[eyrich74]

Re: Help me make a balance charging tray...?

I aspire to building something like that Data - it is my next project, although I have no doubt mine will not be near as symmetrical nor good looking.

For now I have 4x 123 holders JBwelded to a piece of ceramic tile (i like the non-conductive, heat absorbing, non-flammable properties) all soldered end to end with balance leads coming out. I have the main charger connectors on the ends of 1 and 4 but can use a lead with an alligator clip from the charger's + terminal to charge only 1,2, or 3.

 

[kramer5150]

Re: Help me make a balance charging tray...?

Yes. Balance charging is necessary for assembled series-connected packs where you cannot get to the individual cells. Set the charge current to (No. of cells)*capacity. In the example shown below, I set the charge current to 4.8A - assuming that the true capacity is closer to 600mAH than the claimed 1000mAH.

-So all I have to do is wire up how ever many I want in parallel?
-It makes sense that you'd ONLY want to do this with identical cells. But in reality cell capacities can vary greatly over a production batch. What happens to the lower capacity cells in the bunch? Don't they run the risk of being charged over 4.2V?
-Are you doing this with protected or unprotected cells... and does it make a difference?
-If this is all thats needed to charge 2+ cells, then why do the better chargers all have independent/isolated charge bays... with independent voltage monitoring?

:thinking:

 

[kramer5150]

Re: Help me make a balance charging tray...?

I suddenly realize I am in this way over my head!! fascinating none the less, thanks gents!!

Gordon... check your PM.

 

[rmteo]

Re: Help me make a balance charging tray...?

-So all I have to do is wire up phow ever many I want in parallel?
-It makes sense that you'd ONLY want to do this with identical cells. But in reality cell capacities can vary greatly over a production batch. What happens to the lower capacity cells in the bunch? Don't they run the risk of being charged over 4.2V?
-Are you doing this with protected or unprotected cells... and does it make a difference?
-If this is all thats needed to charge 2+ cells, then why do the better chargers all have independent/isolated charge bays... with independent voltage monitoring?

:thinking:

- Yes. Although the particular charging tray shown can hold 8 cells, you can load it with a 1-8 cells. Adjust the charging current appropriately.
- Even if the cell capacities differ (as with production variances - or more likely, different stages of discharge), they will never exceed 4.2V - the charger's CV phase ensures this. For parallel connected cells, the voltage will equalize.
- I do not use protected cells. I don't see any reason why it would be any different for protected cells.
- The reason why the so called "better" chargers (again, why are they better?) have independent bays is that they are designed to charge loose cells as opposed to hobby chargers which are designed to charge series connected packs. This is just my opinion though.

IMPORTANT: Make sure that all cells are of the same type/chemistry (especially do not mix primaries with rechargeables - that is why I recommend using identical cells so that labels are not misread, etc.)

 

[kramer5150]

OK thanks... I am all set.

 

[rmteo]

Looks like you are using a single-D holder for your 18650. In your case, just parallel whatever number of holders you need.

Another solution for 18650's (and 16340's) is to get one of the DSD chargers (DX sku 936, $6.71). Toss the 5V adapter, gut the insides of the charger, connect the cells in parallel, rig up +ve and -ve wires and you have a neat, inexpensive solution for holding 2 cells at a time. Get more if you need to charge 2,4,6 or more cells.

 

[Black Rose]

There are also the LuminousDIY cradles that are available in different cell configurations.

Not sure how easy it would be to connect balance taps on those.

 

[T0RN4D0]

Try searching around for magnet holders