[Bob Wobbaz]

So me and a few friends are going to be starting our own movie PKE builds in the coming months but one thing has been puzzling us, the batteries. Obviously, we would like to install a rechargable battery which we can just plug into the mains and charge it that way. The less we take our pkes to recharge the batteries, the less chance of something going wrong whilst we're doing that. Reading through the build of the original prop, there's a socket on the bottom the handle that allows the mains to be plugged in



Has anyone figured out how to do this? What battery types are able to fit in the handle and charge in the manner? We've been looking at emergency mobile phone chargers but haven't had much joy there. If anyone can shed some light on this, it'll be greatly appreciated

[jackdoud]

Paging mburkit...

[GhostGuy]

I've been looking into this myself. Getting a battery pack made in the right shape is easy enough, it's charging it which is the issue.

If you don't mind it taking 15 hours to charge, then no problem. But if you want it to quick charge in an hour ot two, then you need an external charger of some kind because you can easily overcharge the battery if you don't have proper circuitry to detect when charging is complete, and those can be expensive.

[mburkit]

Paging mburkit...

I hate you Jack. I just want everyone to know that first. . .

Yes, I am doing this with my iona pke meter build that I'm doing.



In my original prototype of the pke meter I had, that I made videos of, that pke meter was running off of 2 of these:

3.7 Li-Ion Batteries

Giving a total voltage of 7.4v at 2600Mah.

And I used this charger with them:

7.4v Li-Ion Smart Charger
EDIT: I just noticed that the image says "7.2v" but the actual page says 7.4v. Just so people don't get confused.

Just be sure not to overcharge these babies. Even though the charger supposedly stops charging the batteries once they are fully charged, make sure you take them off once they are done. Better to be careful then not.

[Bob Wobbaz]

Ghostguy: Hmm, well 15 hours, I'm not too bothered, I mean, its not like I'm gonna be using the PKE every day. Is that something relatively easy to do? I mean, i have some knowledge of circuits but nothing in relation to batteries and making a charge system for them

Mburkit: how have you joined both battery packs together? Just by a wire linking them? And that charger, how long does it take to charge your batteries and what indication is there to let you know they're fully charged?

[mburkit]

Mburkit: how have you joined both battery packs together? Just by a wire linking them? And that charger, how long does it take to charge your batteries and what indication is there to let you know they're fully charged?

You solder wires to them. Then you have the positive of one battery wired to the negative of another. Then when using the batteries, you use the positive wire of Battery (1) and the negative wire of Battery (2). You use the batteries in a "series". Check out this LINK for some picture diagrams, explaining the difference between having them in "parallel" or in a "series".

As for how long it takes for them to charge? I'm honestly not sure because I never fully discharged them. I really didn't use the pke meter enough to drain the batteries completely. The longest I ever had it plugged in was for an hour to get a full charge again.

As for how the charger lets you know the batteries are charged, it has an indicator LED on it. Red means the batteries need to be charged; Green means they are charged.

[Bob Wobbaz]

I see, yeah a series would be the same as if you put end to end - + - + AA batteries in a similar fashion right? Do you install a circuit breaker switch to the PKE lights, and then a seperate cicruit wiring down to the charging socket on the bottom of the PKE? Like two sets of wires running from the + of one batter and the - of the other, one set going to the lights, the other going to the charging plug?

[mburkit]

Here's a quick diagram of how it should be set up.

[GhostGuy]

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Ghostguy: Hmm, well 15 hours, I'm not too bothered, I mean, its not like I'm gonna be using the PKE every day. Is that something relatively easy to do? I mean, i have some knowledge of circuits but nothing in relation to batteries and making a charge system for them

I just did some more research on the subject, and you can't make the circuit as simple as I thought you could. I was gonna suggest using a resistor to limit the current from a 12v wall wart to 50mA, but it turns out the voltage ratings on wall warts aren't all that accurate and it could supply as much as 20v, and that would be bad.

Of course there are other ways to limit the current that should solve this problem, such as an LM317 regulator set up to limit current, but that's probably a bit too complicated a solution for you.

Your best bet is to use a relatively cheap charger like this:
http://www.amazon.com/7-2V-800mAh-NiCd- ... B000BOGAXG

The 800mAh rating tells you how fast it charges the battery. The 800mAh rating on that particular charger concerns me because if you're putting AAA rechargables in the PKE, those may only have a rating of around 700mAh, and that means this charger would charge at a rate greater than 1C. 1C being 1x the mAh rating of the battery, aka, a 1 hour charge. Charging too fast... at too high a C rating... greater than 1C... can be bad.

So, pick a battery pack that will fit in your PKE first, see what the mAh rating for it is, and then pick an inexpensive charger which has a lower charge rate than the battery's mAh rating, is the best advice I can give you right now. Also, with a cheap charger like that, I would make sure I unplug the battery after an hour just to be safe. It probably won't go up in flames but it will kill the battery to charge it for more than an hour if it's not trickle charging.

Of course you could go for a more expensive charger that actually detects when the battery is charged too much. Then you wouldn't have to worry about it.

[Ryusui]

I know zilch about electronics, but I figured I'd offer up a thought.
What about using a camera battery for the PKE meter? DSLR battery chargers have a charge indicator light on them - would it be possible (or safe) to cannibalize a charger and battery set for use in a PKE meter? I'm thinking maybe you could take the charger's internals and hook it up directly to the battery, then convert the charger from wall prongs to a wired charger and charger port. Possible? Dangerous?

[ChapterMasterTu'Shan]

Be EXTREMELY careful when selecting available current with rechargeable cells. Ask burkit