Protection PCB not working?

[hamoidar]

Hi folks, I've got a problem. For the past couple weeks I've been building a saber. I just finished the electronics today! I've got a PC 3.0 running on two 2400mA 18650 batteries protected with a 7.4v PCB. The PC drives a red/red/white tri-star, with two accent LEDs. The saber's got a recharge port, and R.I.C.E.
Here's the problem... When I first removed the kill key, the saber did nothing: no boot sound, beeps, etc. Upon testing the voltage coming from the protection PCB, I found it to be only 0.4v, even when the batteries were both at 3.7v. So I plugged my charger into the hilt for a few minutes, and then tried out the saber. Success!!...for about 10 seconds. I can repeat this cycle indefinitely: charge for a few, run for a few, die. :cry:
I cannot find any shorts within my circuitry, nor can I find a reason that the PC would be pulling the 7A required to shut off the PCB!
Any help is greatly appreciated!

[amwolf]

Well, my first thought would be to plug the thing into the charger and go away for a while. Those 18650's take a good chunk of time to charge fully, and you could be dancing around the bottom of their storage limit. It's been a while since I've drained the batteries on my PC saber, but I think they just shut off when the power gets too low. Eliminate that potential problem, then see what's next.

[Forgetful Jedi Knight]

amwolf has it right. Recharge the batteries fully, and then try it out. It will probably work a lot better. ;)

[hamoidar]

The batteries are fully charged...upon plugging them in the charger light is red for a few seconds, and then switches to green. I also measured them at 7.41v combined. Any other ideas?

[Forgetful Jedi Knight]

Did you wire up the PCB yourself, or is this a pre made pack? Also have you tried running everything outside the hilt?

[hamoidar]

Did you wire up the PCB yourself, or is this a pre made pack? Also have you tried running everything outside the hilt?

Yes, I wired it myself. However I have had alot of electronics experience, and don't think I wired it wrong.

Here are a few pics of my setup:

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[Forgetful Jedi Knight]

Were the batteries fully charged BEFORE you added the PCB?

[hamoidar]

Were the batteries fully charged BEFORE you added the PCB?

Yep, they were both at 3.7-9v.

[dgdve]

Are they unprotected cells to start with? (Maybe its a dumb question)

I would remove and clean everything. Then check to be sure each individual battery is good to go (at 4.2 full charged) before attempting to rebuild the pack.

[Obi1]

Maybe a dump question, but many of the 18650's have the protection circuitry included in the pack. I'm not an expert on batteries, but can it be that the additional protection PCB and the ones coming with the batteries clash?

[Forgetful Jedi Knight]

Maybe a dump question, but many of the 18650's have the protection circuitry included in the pack. I'm not an expert on batteries, but can it be that the additional protection PCB and the ones coming with the batteries clash?This is a good question. Did you use unprotected cells when making your pack?

[hamoidar]

Maybe a dump question, but many of the 18650's have the protection circuitry included in the pack. I'm not an expert on batteries, but can it be that the additional protection PCB and the ones coming with the batteries clash?

Actually I got it working. Turns out one of the batteries was only at 3 or so volts, while the other was fully charged, and I think the PCB sensed the imbalance and cut the connection. I thought that the batteries were charged because the overall voltage was within the acceptable range...
I really appreciate all you guys help! :D