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How to charge rechargeable batteries for a project?

I am going to build a solar powered USB/ Ipod Charger and I have a questions pertaining to it. A solar cell will charge 4 AA rechargeable batteries (NiMH) in a battery holder and these batteries will power a device through a Minty Boost. Now, I have little experience with creating electronics. So I was wondering if I can connect the solar cell directly to the battery holder (with a diode of course) or do I need to connect it to another component and then to the battery holder. Thanks.

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Justin Lam8 years ago
To charge your batteries with the charger it came with, the batteries will be in parallel. You can't use batteries in parallel to charge any other device (because in series (+ ends connected to - ends), the voltage of each rechargeable battery creates 4.8V. In parallel, the amps are added up instead of the voltage.). I was trying to figure this out myself, as I'm doing a similar project, and if you look around instructables, many iPod chargers use a 6V solar cell connected to batteries in series (so you can charge AND use the batteries without switching around the configuration). Now, the problem with having a 6V solar cell is efficiency. It's not going to charge fast, but better than nothing. Go to a warehouse store or thrift shop, pick up a couple solar garden lights, and just take out the solar cell from those. I picked up some garden lights for $3 a pop, which is much cheaper than actually buying a 6V solar cell (which goes for around $12). Three garden lights (usually around 1.5-3V each) will have enough voltage, and enough amps to charge the batteries. I'm not sure if you need a voltage regulator or anything, but you should check with a multimeter to see how many volts/amps it'll produce. Wire the solar cells in series (so the voltage will add up), and voila. It should work, but always use a multimeter to see if anything will go wrong. And since it's the summer, you shouldn't have any problems finding some sunlight.
Chowmix127 years ago
yes, it is perfectly fine. just make sure it is not to powerful, and you will be fine. the charge method is called trickle charging. it uses such low amps to charge the battery that you do not need to stop charging them, they will just keep the batteries topped off. you will need a diode, and wire the solar cell in parallel with the battery holder. in solar lights, they use the same principle, to keep the batteries topped off until the the night falls and the LEDs are activated.
Yan_Sue7 years ago
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If you need any help the batteries , welcome to email us :info@toppower.co.uk

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oOANOo7 years ago
i have the same question (https://www.instructables.com/id/SCZ5MZ6FNNJYKX1/)
"Can i solder the sola cell directly to the batteries? and i think its not always on because if you close the altoids tin its "off" ???"
hmbscott8 years ago
It may possibly dangerous to directly wire batteries between a solar panel and the batteries without a charge controller. There would be no way to limit current in that case because the solar panel is always on. It seems likely that at best you could damage the batteries and perhaps make them rupture or overheat, which could be dangerous. I'm just saying, be very careful with that.
Orro8 years ago
Hi I am not quite sure but I think you might want to pull out the charging curcit out of a battarie charger. Thanks Orro