charging multiple dslr batteries

E

emiliozv

New member
Joined
Apr 8, 2018
Messages
14
Hi guys, this is my first thread here and I want to start easy. Thanks for reading this.

I would like to start a really small diy proyect, and I need to solve some doubts first.
For my nikon d750 dslr camera, I have more batteries than I can charge at once. I have 5 batteries and specific chargers for 3, so I would like to build something to charge as many as I want at the same time, using my balance charger (IMax b6ac).

The camera runs with batteries that claim to be:

Li-ion 7.0v
2000mah
14.0Wh

1st question: My multimeter reads 8.4v when fully charged and 7.4v when the camera tells me to replace them, so I think: the batteries are made from 2 cells of 3.7v nominal voltage connected in series?

2nd question: Could I charge them with the balance charger (IMax b6ac) i have for my li-po batteries I use for my RC's? It is capable of up to 22,2v; up to 6.0A, LI-ion up to 6 cells.

3rd question: Does the charge have to be balanced like with my 3s li-po's?

4rd question: Would it be better to do it in series or paralell and why? In both cases I would have to build the right cable adapter.

Thanks!
 
Lithium Cobolt Cells
4.2 * 2 = 8.4V
3.7 * 2 = 7.2V

So yeah, after a full charge they are going to be 8.4V. You have 2 standard LiIon cells in series there.

2) Yes, you should be able to
3) All Lithiums should have a certain level of balance done. But 2 in series could be a bit different and they generally aren't bms'd. So you should be fine just connecting the Pos/Neg of the pack. But, if you wanted to run a balancing on them, then you could open the case on the end they are bridged on and connect your balance wire there.
4) Series increases voltage, Parallel increases capacity/current. When charging multiple of these packs, you want to do it in parallel, not series. That way each pack is balanced with the other pack. If you connect them in series, you complicate things drastically as you don't know really what the condition of "each" cell is.

And welcome to the club :)
 
Thanks a lot for your fast and accurate response and for the welcome.

Related to the 3rd question, I assume you are talking of the balance of the 2 cells into the batteries. But I dind't even thought about it; I was asking about balancing the different batteries (packs) before or during charge.
When does this happen? automatically when they are connected in paralell to the charger?
Thanks again.
 
emiliozv said:
I was asking about balancing the different batteries (packs) before or during charge.
When does this happen? automatically when they are connected in paralell to the charger?
Thanks again.
Click to expand...

It happens when your packs are connected in series. There is no balancing between packs connected in parallel as the charger will see them as one 2S/7.4V pack.

Your EN-EL15 batteries have BMS inside and 5 contacts (+, -, Temp, Data, Balance). I'm not sure if it will be charged if you apply 8.4V to + and - without connecting the Data and Balance pins.

P.S. Take a look at the inner world of EN-EL14 - they must me similar with EN-EL15
 
thunderheart said:
emiliozv said:
I was asking about balancing the different batteries (packs) before or during charge.
When does this happen? automatically when they are connected in paralell to the charger?
Thanks again.
Click to expand...

It happens when your packs are connected in series. There is no balancing between packs connected in parallel as the charger will see them as one 2S/7.4V pack.
Click to expand...

Well, I was stating this as that each pack would be at the same exact voltage when they are all connected in parallel. Individual cells that are connected in series can only be balanced with each other through the use of balance leads to each cell in the series. So a 2s pack would have 3 wires, 3s pack would have 4 wires, etc.
 
Exactly. The question is what the Data pin does and will it prevent from charging in this case? And if he wants to charge 2 2S packs connected in parallel - how should he balance the cells inside the packs?
If the Data pin doesn't block charging, he can connect 2 packs in series to form a 4S pack and charge them as a 4S pack with balancing (if he knows which one is the balancing pin)

untitled.gif
 
Thankyou all.

I think you only need + and - to charge them, because look at this dual charger I have with interchangeable battery holders for different camera models:
Just 2 connectos to the battery, then it has 3 wires and 2 are connected in the black holder (you can see the picture where i wrote "connected"; i tested it with the multimeter).
Then it goes into the charger (yellow) with 3 pin connections.
I think the 3rd wire (connected to mid pin and electrically connected to -) is for balancing the cells into the pack (battery).



image_hwbzhw.jpg



image_pbdxom.jpgimage_rgbifu.jpg
 
emiliozv said:
I think the 3rd wire (connected to mid pin and electrically connected to -) is for balancing the cells into the pack (battery).
Click to expand...

No, because

Just 2 connectos to the battery
Click to expand...

So your charger just charges but doesn't balance the 2S pack.
Korishan told above that for balancing 2S you need 3 wires, 3S - 4wires, XS - X+1 wires.
And you balancing pin can't be shortened with any of other pins because it would result in short circuit and battery failure/explosion
 
Ok I think I was not understanding all well
Now I see that in my scheme the balance wire is not present. It would have to come from the bridge between the - in the cell 1 and the + in the cell 2 of the 2s pack.
So this charger is not balancing the charge between both cells in the pack?... oh crap. Should I then use the official charger (with 5 pins) from time to time to balance the cells?
I don't know what is the white wire for then...

Edited after thinking for a while:
If the 2s pack is made of 2x 1S cells IN SERIES , they should balance automatically, as you said before right?
And I supose the white wire is for measuring the voltage to cut when it gets to 8,4v
 
Automatic balancing doesn't exist. That's why you need balance charger like Imax B6.
Balancing is being done after the batteries are fully charged. It's being done by comparing the cells' voltages and discharging the cell which has higher voltage to the level of the cell withlowest voltage.
For example, you have 2 cells in series. After being fully charged the first cell's voltage is 3.94V and the second one's - 4.18V.
The balancer connects the B wire (which is connected to - of the second cell) and the + wireto its internal load and slowly discharges the second cell down to 3.94V. After balancing both cells will have the same voltage and the 2S pack will be balanced.
untitled7.gif


Should I then use the official charger (with 5 pins) from time to time to balance the cells?
Click to expand...
Yes, you should, if you don't want your batteries to die faster.


I supose the white wire is for measuring the voltage to cut when it gets to 8,4v
Click to expand...
I'm not sure but i think it's for temperature monitoring (is connected to a thermoresistor)
 
In most cases the 3rd wire is a temperature probe. Only the charger uses that connection but it is not required for charging.
 
So my charger is considering my packs as a 2S 7,4V cells, making an unbalanced charging, and nothing crazy has happened yet. The thing is that it is double and faster than the original one. I think I will finish the charges with the official charger from time to time, just to recover possible differences in voltages between the cells from several unbalanced charges.

Following this method, I see no problem in making a custom charge with my imax b6ac, building a cable for paralel balanced charge with the following settings:
5 batteries of 7,4v (2S) in paralell balancing the packs (not the cells inside de packs). I would limit the voltage end to 8.4v, and possibly finishing the process with the original charger one by one.
Do you see any problem here?
Thanks!
 
If 1 pack is causing dbl charge rate, then connect two packs in parallel. They'll share the load and effectively make it 1/2 of what the charger is outputting. If you want to slow it down a little more, put 3 in parallel
 
emiliozv said:
Following this method, I see no problem in making a custom charge with my imax b6ac, building a cable for paralel balanced charge with the following settings:
5 batteries of 7,4v (2S) in paralell balancing the packs (not the cells inside de packs).
Do you see any problem here?
Thanks!
Click to expand...
I just don't understand what you mean by "parallel balancing" or "parallel balanced charge"? It sounds like "solar Moon" to me.
 
thunderheart said:
I just don't understand what you mean by "parallel balancing" or "parallel balanced charge"? It sounds like "solar Moon" to me.
Click to expand...


I mean this:

image_ljypvr.jpg



And each 3S battery is like this:

image_ofmumm.jpg
 
You'd better not to do that. It will work, but it will take way more time and if a cell in a 2S pack is dead or almost dead it will not leave the balancing to be done correctly.
 
Thanks!, BTW, do you see this normal? I'm having issues with this RC transmitter and I saw this:


image_wuixtp.jpg
 
You must log in or register to reply here.
Back
Top