Dual battery mod... uneven battery drain

[vaper1960]

I got my first dual battery mod (Vaporesso Revenger X) and new batteries (Sony VCT5A)
I love this mod by the way. It has the two batteries in series and I have heard that they often do not drain at the same rate... that is what I'm seeing. Should I swap the batteries now to even them up (before charging) or charge them both and then swap positions in the mod? Or does any of this really matter?

 

[HigherStateD]

I got my first dual battery mod (Vaporesso Revenger X) and new batteries (Sony VCT5A)
I love this mod by the way. It has the two batteries in series and I have heard that they often do not drain at the same rate... that is what I'm seeing. Should I swap the batteries now to even them up (before charging) or charge them both and then swap positions in the mod? Or does any of this really matter?

One battery is draining completely before the other is used at all? I don't have that particular mod, but that doesn't sound right to me. Hope you get a better answer soon.

 

[vaper1960]

@HigherStateD , good to hear from you There is only a light difference between the two batteries (and it seems to be common) I went ahead and swapped the position of the batteries and they are doing fine. BTW, those XMJO batteries are still doing OK (and I use them a lot)
On a side note... how the heck can a mod tell the charge on each battery when they are in series?

 

[HigherStateD]

@HigherStateD , good to hear from you There is only a light difference between the two batteries (and it seems to be common) I went ahead and swapped the position of the batteries and they are doing fine. BTW, those XMJO batteries are still doing OK (and I use them a lot)
On a side note... how the heck can a mod tell the charge on each battery when they are in series?

My guess, it's a series/parallel relay. I don't know exactly how it works, but it's similar to how a diesel starter works.

 

[Richard Winter]

I got my first dual battery mod (Vaporesso Revenger X) and new batteries (Sony VCT5A)
I love this mod by the way. It has the two batteries in series and I have heard that they often do not drain at the same rate... that is what I'm seeing. Should I swap the batteries now to even them up (before charging) or charge them both and then swap positions in the mod? Or does any of this really matter?

Batteries in dual mods can and do drain slightly differently depending on the configuration. A good tip is to mark your batteries either A&B or 1&2 and everytime you've charged them, swap the way you fit them in the mod. This will even up the loading on them.

 

[Richard Winter]

@HigherStateD , good to hear from you There is only a light difference between the two batteries (and it seems to be common) I went ahead and swapped the position of the batteries and they are doing fine. BTW, those XMJO batteries are still doing OK (and I use them a lot)
On a side note... how the heck can a mod tell the charge on each battery when they are in series?

I would think a 3rd wire (balancing wire) would be used between the two cells to monitor the state of each battery. I might be completely wrong tho.

 

[Mooch]

Batteries in series, by definition, are discharged at exactly the same rate (discharge current level). That cannot change.

However, every battery is slightly different so their voltages can be different at different points during discharge. This is normal and is not helped by changing battery position since what causes the different voltages is internal to each battery. Many devices have less than accurate voltage reading accuracy too so don’t put too much trust in them unless it’s a well built Dicodes or DNA regulator board based device.

If you charge the batteries externally, in a separate charger, then any differences in their voltages is “reset” every time you charge them since they are both charged to 4.2V if you let both completely charge. So no worries there unless the difference in voltage when you’ve used them for a while starts to grow larger and larger. That is a sign that one or both of them has reached the end of its life or is damaged.

 

[Mooch]

Batteries in dual mods can and do drain slightly differently depending on the configuration. A good tip is to mark your batteries either A&B or 1&2 and everytime you've charged them, swap the way you fit them in the mod. This will even up the loading on them.

The load on each cell is identical, by definition, in a series-connected device. Each cell is different though and that can cause them to reach different voltages. Swapping positions doesn’t do anything and even if it did it's not needed since the cells are rebalanced when externally charged.

 

[Mooch]

@HigherStateD , good to hear from you There is only a light difference between the two batteries (and it seems to be common) I went ahead and swapped the position of the batteries and they are doing fine. BTW, those XMJO batteries are still doing OK (and I use them a lot)
On a side note... how the heck can a mod tell the charge on each battery when they are in series?

If you add a wire at the junction of the two series-connected batteries (the “middle”) then you can read the total voltage of the two batteries (the “top”) and the voltage at the “middle” wire. Assuming that the wire connected to the “bottom” of the stack of the batteries is at zero voltage let’s you easily calculate the voltage of each battery by looking at the voltages at the “middle” and the “top” wires.

 

[vaper1960]

Thanks @Mooch , I get it now...no worries (the batteries are new and doing fine)
It only showed (according to the mod display) a very small difference so not going to trip on it.