First Post! Uneven Drain on DIY Hammond style Box Mod. Help!

[mouthbreather]

// A little introduction
- I live in Austin TX mostly off of breakfast tacos and the sweet vapors.
- I've been vaping in some capacity for about 2/3 years.
- Had the usual vape path. started with cig-a-likes, got tired of cig-a-likes, moved on to clearos, got obsessed with aspire clearos, and inevitably ended up in the world of RDAs, mech mods, box mods, etc.
- at the moment, my two favorite RDAs are the Viking RDA by Fight Club Mods and the Doge V2/V3 top cap from Congrevape.
- I typically prefer mech mods, but lately I've been leaning towards Box Mods.

That brings me to my first question for folks. I just finished building my first DIY Hammond 1590B Box Mod. I have a Nitecore 2014 Intellicharger, 4 bay, without the fancy LED screen. I've just got the rows of LED lights.

Everything on my Box Mod works nicely. In fact, it seems pretty beastly. Here's some of the specs
- unregulated wired in parallel
- 1590B Enclosure
- 3 AMP Anti Vandal Switch, the one that sits pretty flush, screw connections/no solder.
- MOSFET with 15k resistor soldered.
- 16 Gauge stranded copper wire with silicone insulation throughout.
- keystone dual 18650 sled.
- Fat Daddy Vapes V4 510 with 22mm washer.
- Magnet Lid Enclosure.

I basically followed find my vapes tutorial so it's a straight forward design. I made some changes:
- fat daddy 510
- 1590B Enclosure
- excluded the fuses on the positive connection. my switch is soldered to one positive battery terminal which is chained to the other battery terminal and that is soldered to the pin in the fat daddy.
- other than that, the mosfet and negative battery terminals follow the find my vapes instructions.

Here's my concern. I bought a pair of Sony VTC4s so they're cycled/charged together only in this box mod.
I've noticed the drain on the batteries does not appear to be even. I'll notice they are showing different 'charges' by looking at the leds on my intellicharger. It doesn't seem to be so drastic as one is fully charged and the other is fully drained or anything. The box mod does appear to be using both batteries and the results would support that theory. They just seem to be draining at somewhat different rates.

Should I be really concerned about this or is this relatively normal for a DIY Unregulated Box Mod?

 

[HMav]

The batteries are being utilizes unequally for the following possible reasons.

1. The electrical path is longer for one battery than another in an electrically significant way (more resistance in the path for one battery than the other).

2. The batteries have significantly different internal resistances (or capacities).

I would be mildly concerned at this point, since it means something isn't right. Try swapping battery positions and see if the same battery still shows a lower SOC at charging time. If it does, get a new matched set for the sake of safety. If it doesn't you can try re-working the electrical path or just make sure that you swap battery positions on each cycle.

 

[mouthbreather]

Hey! Thanks a lot for your advice.

I've heard that, to a reasonable degree, this can happen and it isn't a huge worry. I still like to be as safe as possible with these things though.
- I charged them together and threw them in a ABS Unregulated Box Mod and they drained evenly, so I think that alone isolates the issue to my DIY Box... which is a bummer.
- I'm going to take your advice in any case and cycle them to see if I can figure out where the issue is. I'm not looking forward to desoldering and reworking my wiring though that's for sure.

 

[Rsunderl]

If you have an ohm meter, you could run resistence checks on the various points of your wires before desoldering. Just a thought.