Plug in re-charge for mods

[Rubberjohnny]

Advice needed from a more experienced "Bodger" please.

Mods that use re-chargeable NiMh/NiCad batteries need those batteries charged on a regular (maybe daily) basis. Now that requires removal from the mod, charging and replacement. I want to wire into a mod a standard 2.1mm DC power socket in parallel with the battery pack so each night the mod itself is simply plugged into a charger and removal of batteries is not needed.Nowthe mods batteries (1.2v AAA NiMh) are wired in two packs, each containing 4 batteries in series and the two packs then wired to each other in parallel to give 6volts at the atomizer from all 8 batteries (this has proved a serious vape monster).

Heres the question.
Universal NiMh/NiCad chargers tend to allow for the simultaneous charging of typically 4 AAA or AA batteries-each battery having a seperate position in the charger.Now if I open up the charger and run a fly lead (ending in a 2.1mm DC power plug) off the transformer output will this suffice as my new charging option for the above packs without battery removal or will I need a charger (maybe a mains driven transformer outputing 6volts/lowish mAh).

Many thank's in advance...........a totally mad moder.

 

[Grumpysanta]

On the face of it a good idea, but in practice not so good. First of all you need to protect the batteries in case of shorting the power socket and a simple diode is not enough to protect the batteries, the extra protection circuitry would make your mod a lot bigger than it is already. Secondly you would use NimH batteries as a minimum, NiCad's are just not good enough for what we are doing and the correct charger usually operates charging two in series, so four batteries are using effectively two chargers. Most chargers are using a dedicated integrated circuit which is designed to provide the correct constant current / voltage, for your mod you would have to start from scratch and design a circuit with the correct behavoural characteristics for charging your battery combination. The amount of effort required in my opinion is not worth it. It's much easier to unscrew the mod and change the batteries.

 

[RjG]

no, you can't mod a 1 or 2 cell charger with a wire, wrong voltage

yes, you can just run a 6 volt transformer to charge your mod... but if you don't want to wreck your batteries, you need to stay at or under 1/10 of the NiMh battery capacity. Otherwise they'll get so hot they'll be ruined.

So if you have 2000 mah batteries, 1/10 of that is 200ma MAX
Since you have 2 packs in parallel, you could go as high as 400ma MAX

Charging this way, when a NiMh battery just starts getting warm, it is peaked, you can take it off charge. Anything past that is wasted energy and will just make the pack hotter with no increase in charge.

A note on plain "adaptor" style wall transformers - even rated at the milliamps for what you are using it for, if it's a cheap one you might cook it anyway if your pack is -really- dead, since the pack will suck really hard on it for the next 12 hours straight. A cheapo transformer might not survive that... but it is the way most cheap junk rechargable things you buy work.

Trickle charging methods are not going to give you overnight charging though, you have to choose between slow, safe, low power constant current OR fast peak charging.


If you want a peak charger, your local hobby shop will have a good selection. They don't cost that much... and once you have a decent hobby charger, you can charge ANYTHING, you can start playing with cheap DX lithium ion batteries too If you get one with a cycler, you can test your batteries too, so you know how much capacity they have (very handy)

Or - if you're lucky - look in a box of old junk or ask around, see if you can find an OLD cell phone charger, like an old motorolla flip phone type. The ones you stick the battery in to charge. The older ones used nimh / nicad packs, and they are usually 4 hr peak chargers - you can 80% of the time just pull two wires from that, and get a nice 6v peak charger for free.

How do I know all this stuff? About 10 grand of R/C stuff collected over the years... and I -do- use a bunch of old various brand cell phone chargers to peak charge my gear ;-) (as well as a couple nice hobby shop universal chargers/cyclers )

happy modding

 

[Rubberjohnny]

Many thanks for info. As a sad redundant equipment "magpie" I have a goodly collection of mains transformer chargers in my shed (all Brit "bodgers" invent their best mods in their shed!!) so will dig them out and see if any are applicable. Will report back on sucess (or otherwise) as long as I have not burnt down the family home!!