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By infernoprime

I went to another forum about this little project but after I said I did not understand this field very much yet I felt like I was denied help,but that does not mean I can't do other things.

First off what I want to do is to modify this to accept small dc voltage's around 1-3v from a small solar panel sitting on my desk in the sunlight if it sits for more then a day or two that's fine but I will be disconnecting it during the night.

Will this be very hard to do ?,Also I have a very high Res camera if pics of the unit or board are needed.
User avatar
By phalanx
Hi infernoprime,

In theory there is no reason why you couldn't do what you are suggesting but there are a number of factors you will have to investigate. First you would need to figure out what DC voltage is being created from mains power for the unit to operate. There is a very likely chance that the internal DC voltage is higher than 3V which would mean you would need a boost converter off your solar panel to get the voltage you need. After that there are the power requirements of the charger. If you are charging 2000mAh batteries which take 4-5 hours to complete, that means each battery is likely receiving 400-500mA each. I don't know their charge profile but that would ballpark to around 0.6W per battery. Your panel would need to have enough headroom for 4 times that number if you charge 4 at a time. You would also have to ensure a constant supply of light to the panel. If the unit browns out, the charge cycle will likely start again and odd things can happen if this cycle happens quickly. It's hard to say what the electronics inside the charger do when exposed to marginal power.

In theory everything should work but it may not be practical. If you want to dig into it further, a lot more details will have to be made available. You will also have to reverse engineer the control board in the charger since I'm quite certain Energizer doesn't make the schematic available to the public.

Good luck!

By infernoprime
Thanks for your reply.

I will check into this and get back the details. I am currently learning other fields as well so it mite be a while before I reply but again big help thanks.
By infernoprime
Update: I took some pic's just in case they may help.First off though I will only be charging 2 battery's at a time and waiting several days is fine as I will be unplugging them when night comes so I wont need a blocking diode.

First is the backside: Image

Frontside: Image

Please let me know if these mite help. I am still looking into identifying the mini transformer and what the voltage is being stepped down to. Also please don't rage some things still don't make sense to me as I need them explained in a simpler way.

PS. Phalanx I did read your post above and I will get the precise current and voltage measurements tomorrow if not Friday.

If there is any other info I can provide please let me know.
User avatar
By phalanx
It's hard to reverse engineer boards from pictures but a place you can start is the diode and capacitor to the right of the transformer when holding the board upright. The cathode side of the diode (the exposed lead that bends downward and into the board) appears to be the regulated DC voltage rail and the common ground is the negative terminal of the electrolytic cap right next to the diode. The DC supply appears to be isolated from the mains which is good.

You'll have to tap into those points to measure the DC voltage the charger uses but make sure to be super careful since to the left of the transformer you have exposed 120VAC mains power which can hurt you quite quickly. There are a couple of ICs involved in the process which I'm guessing are part of the regulator circuit used to keep voltages constant during the varying loads of charging.

Remember to be careful. You don't want to be shocked.

By infernoprime
Big thanks for your help bro I am sorry about the way the pictures appeared I put them in as a link.

I also got those measurements for the small solar cell.

These were taken with the sun on them I am not sure what they are on a cloudy day I do know they are only to be used with the sun anyway they are.

User avatar
By phalanx
If those numbers are correct, your panel won't be suitable for powering the CHPROWB4 since it can only deliver about 12mW. You will have to double check your measurements or find a more significant panel for your purposes.

If the measurements are accurate, the solar panel you have would only be suitable for a single cell trickle charger.

By infernoprime
How high of an output would I need then ?.

PS I would also like to ask how you are figuring out how much voltage I would need as this is an area that is hard for me.If you know any sites that could explain this is the simplest of terms that would be nice to.

Again I really appreciate the help you have gone a long way and I hope I can count on your help in the future.
User avatar
By phalanx
It's hard for me to say exactly what you'll need since I don't have one of these chargers. You can get a rough estimate by using a power meter like a KILL A WATT ( to find the power draw from the wall and use it in future calculations as you learn more about the charger circuitry.

I'm not really figuring out what voltages you actually need, I'm more so doing a sanity check on the suitability of your solar panel based off the measurements you posted. From the sell sheet for your charger, it advertises that it can charge a battery in 4-5hrs. I made an assumption of a 2000mAh battery which isn't an uncommon capacity. In an ideal world, to charge a 2000mAh battery in 4hrs requires 2000mAh/4h=500mA charge current. In reality nothing is 100% efficient so you would actually require more than this. 500mA is a lot higher than the 5.33mA from your panel so you aren't even in the same ballpark.

I can also tell from the circuitry on the back of the charger that 2 cells are charged in series which doubles the individual voltage needed to charge a NiMh cell. If you look up the charge profile for a NiMh battery you will see that the charge voltage can range between 1.4-1.6 volts depending on the charge rate. If you double the low end value, you get 2.8V which is higher than what your panel is putting out.

The voltage and current both don't have to be larger than the needs of the charger since there are DC-to-DC converters that can turn a high voltage, low current supply into a low voltage, high current supply (and vice versa) but the important detail is the original power available needs to be higher than the demands of the device you're powering. This is a lesson for another time.

Since your charger has a controller on it, it will be checking for appropriate voltages and will likely terminate the charge cycle if there isn't suitable input power. There are simpler trickle charger circuits you can look up that would be more suitable for small solar panels.

By infernoprime
I would have done that but I am in a position where I am unable to provide for myself at this time. So at the time I was able to scrape enough together from filling out forms online to get this.

Thanks for your very informative post I found another panel which I'm guessing mite be enough hopefully but would be possible to bypass whats converting the 120/220AC over to dc and just connect to the dc side ?.

Again thanks and I am sorry if I don't catch on to things you mite be explaining.
User avatar
By phalanx
infernoprime wrote:Thanks for your very informative post I found another panel which I'm guessing mite be enough hopefully but would be possible to bypass whats converting the 120/220AC over to dc and just connect to the dc side ?
If you refer back to my post just after the one where you posted pictures of the circuit board, I mentioned where the DC voltage is present in the charger and that you have to measure it with a multimeter. To directly apply a DC voltage, we need to understand what that voltage needs to be. Due to having 120VAC (or possibly higher) present in the unit when you make the measurement, you need to be very careful since a shock from mains power can be very dangerous.

By infernoprime
I cannot tell you how angry I am right now for what has happened. I was testing the main wires that connect the wall mains to the board and it sparked I have uploaded pics to show how it looks.

I really need to remedy the situation before I have an anxiety attack. So my first thought was bridging a wire from the mains red wire (small area with flux) over to the left where the first solder joint is on the bottom right corner.



User avatar
By phalanx
Needless to say, you need to be vary careful when working around mains voltage. It's extremely dangerous if you aren't sure of what you're doing.

On that note, not all appears to be lost. From the first picture you posted in this thread, there is a sleeved resistor or some other component that's connected in the area of the wire and pad you burned up. It looks like the unsleeved side is connected to the same trace as the burned pad. Post a better picture of the top but it looks like you could attach a wire to the unsleeved side of that component and be back in business.

Do you have anyone nearby that could directly help you?

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