One battery goes flat in 3 seconds- Help please.

Pleaae can someone explain this.

I recently bought a romisen RC-T5 and some ultra fire16340 protected cells.

I am only my second charger having thrown the first one away thinking it was faulty. I am now using a ultra fire charger.

The flashlight works fine on duracell disposable c123 batteries( 3.0 volt) but something very strange happens when using the rechargeables.

I have 7 batteries to use all charged to 4.16 volts. The light takes 3 or 4 batteries. If I put 4 batteries in the light lights up very dim so after a few seconds I check the voltagesand 3 batteries are almost the same but one battery is ZERO volts.

I then try again but shortern the light and put in 3 good batteries, the light usually lights up with a slight flicker then goes out or very dim after a few seconds. Again one of the batteries reads zero volts.

The batteries work ok ( 2 at a time) in my ultarfire c2 so I dont think batteries are the fault.

Like I say , the Romisen works fine on duracell disposables so Im not sure the light is faulty .

Suggestions please, anything I can check ?

Thanks

Mark

ps I put the 2 batteries at zero volts on charge and within a minute or so they were back up to 4.2 and working fine in my c2........perhaps they had not gone flat? could the protected bit on the battery have kicked in and shut off??

Should i try unprotected cells?

Can I convert a protected to an unprotected?

EDIT the flashlight now works on 3 cells but when I put 4 in it goes very dim / off and the last cell goes to zero volts.

the protection is tripping. Use AW brand protected RCR123 for a protected higher current application.... [edit in] after reading the reviews on DX for this light, I'm confused as to why the protection would be kicking, they say it only runs about 2W per emitter on high, which should only be maybe ~600mA drain (probably less) per RCR123, which wouldn't ordinarily trip the protection unless it were set really low, they are usually set somewhere around 1-1.5A.

[edit in]
Better yet, if the light will stay in regulation on a pair of 18650s, which I think it might... 2x18650 would be a much better power source for that light. (Assuming it's the same as this one:
http://www.batteryjunction.com/rc-t5.html

I am not remotely an expert about batteries, but when you say you put the battery that read zero on the charger and it showed full within minutes -- I think that means your battery has almost no capacity left to hold charge.

The analogy (I am now going to prove I'm not remotely close to expertise)

Voltage is how deep the lake is
Amperage is how much water the lake holds

You've got a lake that's a hundred feet deep and six across wide (grin).
So it fills up real fast and drains real fast.

The chemistry determines the voltage; how much of the chemicals are left in it that are actually getting altered determines the capacity.

Now someone will explain this much better ....

Thanks for the reply.

I think the problem may be with the switch. When I unscrew the switch and use metal foil to make the contact the light works.....or at least it did for a while then stopped working . But having said that its not making sense as I put in 4 duracells and it works perfectly. Perhaps its because these are shorter and make better contact at the switch end?

Thanks for advice to use 18650, but I would prefer to keep to the battery type I already have as I then only need one charger in the van. If the problem is due to battery lengh would the 18650 s cure this?

Is a 16340 and a rcr123 the same?

Do you think another type of 16340s would work? If not I will get 2 18650 and a charger .

Many Thanks

Mark

16340 and rcr123 are the same, yes. (the 16 stands for diameter, 34 is length, the 0 means that it's round, an 18650 cell is 18mm diameter, 65mm long and round)

Usually, protected rcr123/16340 cells are a bit longer than primary 123 cells. The shortest 16340 cells that I know, are offered by the infamous AW. AFAIK, they appear to be the only cells that I know that can be used in a fenix P3D for example. Too bad that because of their almost 2mm shorter length, they also have little less capacity. But since the capacity of a battery that you can't use is essentially zero, the AW's make sense (even if they're over twice the price of other brands)

Thanks all,

Is using unprotected 16340s such a bad thing? The ultra fire charger is supposed to cut out when batterys full, it seems to be working ok?

Sorry to be dim ( pun intended) but what does AW stand for?