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Battery and Solar Charging for small electronics project

Discussion in 'Battery Discussion' started by wayner, Jan 27, 2015.

  1. wayner

    wayner Active Member

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    I am doing a little project where I will be powering a Raspberry Pi computer with a battery and using solar panels to charge the battery. Can anyone suggest some good resources on the web that deal with topics like pros/cons of using Sealed Lead Acid vs NiMH Vs Lithium Ion, whether you need a voltage/current regulator, etc.
     
  2. nwdiver

    nwdiver Active Member

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    Do you have an idea of how many watts you want and how many wh of storage? Is this going to be cycled daily?
     
  3. lolachampcar

    lolachampcar Active Member

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    I just picked up a (Linear Technology I think) development board for a 50 watt solar panel 12v battery charger. The part managed the power, maximum power point tracking and buck switching to provide the charge then float voltage for the battery. I'd have to go look at it again but I think there were provisions for changing the charge voltage, current and float voltage. A search of the Linear site for solar panel chargers should find it. PM if no joy and I'll go find it.
     
  4. wayner

    wayner Active Member

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    This is fairly low power. I will be using a Model A+ Raspberry Pi which draws around 100mA while Idle and about 130mA while under load. The power supply is 5V so that is 0.5 to 0.65 W. I will also be using a USB Wifi dongle which will increase that power consumption somewhat but it should still be well under 1 W. I will be using something called a MoPi that manages the power. This input voltage for this can range from 6.2-20V.

    For the battery I was thinking of using a 12V Sealed Lead acid battery - the type that you use for a security system or UPS that is about 4Ah and 3x3.5x4 inches. I was under the impression that this type of battery is less finicky than "better" battery technologies like NiMH or Li. I have ordered a 15V/300mA/4.5W solar panel on eBay and it is on its way from China. I was hoping that I don't need a controller or regulator if the battery and solar panel are well matched. But apparently with sealed acid batteries they can swell up if overcharged.

    In terms of the cycling that will be done on the battery - I guess that depends on how things work during the day in terms of whether the battery is charging while the sun is out or if the generated power is going to the Pi first rather than the battery. This will likely be used from May-Sep at 43 deg North with direct sunlight for most of the day so there can be as much as 14-15 hours of sunlight. Assuming 150mA draw during night should still give 26 hours of operation with no charging from the solar cells - I will have to see how things go if there isn't a lot of sunlight to charge the cells.

    So I was looking for web sites/forums where people may have used batteries and solar cells for similar applications like remote weather stations.
     
  5. wayner

    wayner Active Member

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    Thanks Alligator, there is useful stuff on that page. But I think that guy is going way overboard with the size of his solar panel and battery as he is using a 50W panel and very large battery. My power consumption, as mentioned above, should be less than 1W.
     

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