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11-20-2012, 05:09 AM   #1
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Battery Adapter or Charger options in India (Urgent request)

Hi all,

I came to India for a short vacation today morning for a few days and realized that I didn't bring my charger for the K-30 with me. I bought this camera couple of weeks back for this vacation primarily.

Does anyone have suggestions for me to keep my camera clicking?
- Any place where I can buy a spare battery charger in New Delhi, India
- Or a place where I can buy a AA adapter for the K-30?
- Or if there is anyone on this forum in South Delhi (near Hauz Khas, Malviya Nagar area) who would charge the battery for me once. I think I will need to charge the battery only once during the trip.

Thanks everyone for any suggestions/ideas.

Gaurav

11-21-2012, 09:39 AM   #2
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Not recommended unless you're good with electrics and can check voltages on a meter..... 12v car battery via the cigarette lighter socket because it will be fused, connected in series with a 12v 5w small bulb, + to + on the K-30 battery, - to -. Ignore the other terminals on the K-30 battery. This will charge at 0.5A or a bit less and the bulb may slightly glow as it will only get about 5v (but it should get warm), so will take about 2hrs to charge a 1000mAh battery if it's fairly flat to start with. Keep checking that the battery isn't warming up any more than barely when it's nearly charged, and stop if it is. The main things to look out for are not ever shorting either battery, having the correct polarity, and the no heating up bit as the battery's internal thermistor isn't being used for overheat protection. Repeat - this could be dangerous if tried by anyone who doesn't understand the principles of electrics and battery charging. You'll have to locate a cigarette lighter plug from somewhere of course. There's also solar panels that could replace the car battery but they will likely take a lot longer to charge up the K-30 battery.

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11-21-2012, 02:55 PM   #3
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Thanks. Do you know what are the other terminals on the battery? I will think about it and may even be tempted to try it out. The issue is perhaps finding the right small bulb because the internal resistance of the battery needs to be similar to that of the bulb for similar voltage drop. Otherwise, the battery may get far less or more voltage than 7v, correct?
11-21-2012, 04:44 PM   #4
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QuoteOriginally posted by agaurav Quote
Thanks. Do you know what are the other terminals on the battery? I will think about it and may even be tempted to try it out. The issue is perhaps finding the right small bulb because the internal resistance of the battery needs to be similar to that of the bulb for similar voltage drop. Otherwise, the battery may get far less or more voltage than 7v, correct?
No, bulbs are more or less constant current over quite a wide range of voltage because as the voltage rises the temperature rises with it and that raises the resistance, and ohms law and all that tries to hold down any current rise. It will never draw hardly any more than the current it takes at 12v which is 5/12A. Most petrol stations and supermarkets sell car bulbs. By the way, your battery is fully charged when it hits 4.2v maximum if you have a meter. I wouldn't use this method of charging regularly by the way, just once or twice - it's always best to use the proper charger.

The 4 terminals? + and - for the battery output terminals, T for the thermistor which is used by chargers to measure the battery temperature, and D is a mystery as most Li-ions have only 3 and if you look inside your camera it only uses the other 3! D measures a few kohms to -ve so may be an optional means of identification by value, perhaps the official Pentax charger looks for a certain value before it will commence charging.

11-22-2012, 05:40 AM   #5
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Thanks Steve. I was concerned that if I connect a bulb in series then the voltage drop across the bulb may be only 3V and so the battery will end up getting 9V that may be too high. My idea was that the bulb must have same resistance as that of the battery.

Or if I buy a spare phone charger like a USB based charger, the output of those is 5V so can I just cut the leads and connect the +/- without a bulb in series? Anything wrong with such an approach?
11-22-2012, 11:34 AM   #6
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QuoteOriginally posted by agaurav Quote
Thanks Steve. I was concerned that if I connect a bulb in series then the voltage drop across the bulb may be only 3V and so the battery will end up getting 9V that may be too high. My idea was that the bulb must have same resistance as that of the battery.

Or if I buy a spare phone charger like a USB based charger, the output of those is 5V so can I just cut the leads and connect the +/- without a bulb in series? Anything wrong with such an approach?
The main problem is that there's no control over the charge current. You could be lucky but I would want to measure the current flow first. The charger might instantly blow a fuse though, probably a non-replaceable one if it does. Something in the 50mA (20hrs) to 500mA (2hrs) region would be needed but with a USB 5v you will probably get a tailing off of the current as the battery charges so the maths gets vague but will take longer than the initial charge would lead you to believe. You would still aim for 4.2v = fully charged though. Make sure you don't buy a high power one, try a weedy one first, it's more likely to work within the required window.
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