Solar Charging Your Portable Comms Batteries

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teotwaki
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Solar Charging Your Portable Comms Batteries

Post by teotwaki » Thu Nov 16, 2017 5:48 pm

I've bought a few of these off of eBay and they are a good bargain for 2.5 Amp or less charging using the MPPT approach to PWM charge controllers

https://www.ebay.com/itm/MPPT-Solar-Cha ... 2749.l2649

Image

This one is based on a chip from Consonance, the CN3767. (Lithium battery versions will use the CN3791 chip) The CN3767 is a charge controller that employs PWM step-down (buck) switching.

I've reversed engineered the PC board components based on the info in the datasheet http://www.consonance-elec.com/pdf/data ... CN3767.pdf

Max current is limited by the large current sense resistor R5 at 0.050 ohms for 2.5 Amps. The MPPT point for the panel is 18 volts as set by R1 & R2, a voltage divider set to apply about 1.25 volts to pin 6. You can adjust the ratio to match your own panel's MPPT voltage point if different..

The eBay listings have a "best offer" button so I've gotten two boards for $12 and free shipping which was not that slow from Hong Kong

Larger image here
http://i.ebayimg.com/images/i/172831351 ... -l1000.jpg
My adventures and pictures are on my blog http://suntothenorth.blogspot.com

CrossCut
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Re: Solar Charging Your Portable Comms Batteries

Post by CrossCut » Fri Nov 17, 2017 8:21 am

Will make nice upgrades for my solar trickle chargers in my polebarn and BOV. Thx!

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teotwaki
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Re: Solar Charging Your Portable Comms Batteries

Post by teotwaki » Fri Jun 15, 2018 11:21 am

Long term report on the ChiCom MPPT charger circuit boards

Image

I have some that have been out in the field continuously since Jan 27th. Each of them are attached to a 10 watt (measured 0.6 A peak) panel and a 7 AH gel battery and they have worked flawlessly. They power some field experiments that are collecting data and sending it back in a radio burst. In standby the experiment's total current draw is 80 milli-Amps. In transmit it is about 250 milli-Amps. If there is no sunlight each battery will last for two days without recharging.

One small note with the circuit components is there is no reverse current diode in the circuit. Take a look at the data sheet in the link.
http://www.consonance-elec.com/pdf/data ... CN3767.pdf Otherwise the circuit has good components.

If the board has a battery attached and no solar panel you must avoid shorting out the solar panel plus (+) input to ground. Shorting that lead will burn out the 0.05 ohm current sense resistor on the PCB. Ask me how I know.....

I modified my boards by desoldering the tab of the input FET and inserting a good high-current low voltage drop diode. I had some Motorola MR850 Ultra Fast Recovery Rectifier Diodes. Because the FET uses the PCB as a heat sink I soldered a small copper fin to the transistor's tab.
My adventures and pictures are on my blog http://suntothenorth.blogspot.com

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