Maker Pro
Maker Pro

Energizer CHPROWB4 Project

I have posted on a few other forums about this looking for help but everyone seems to leave a few comments about helping then just quits.

The general idea is I have a solar panel (5v) all I want to do is feed the dc from the panel into the dc part of the charger. to power it from dc instead of ac. I do not plan to do anything else if I don't have to.

And please go easy on me.
 
The part # you gave seems to be a bundle of CHPRO charger plus 4 batteries. This charger (linked below) has the AC mains wall plug directly on the rear of it, unlike some that have a separate AC/DC adapter (usually at 12VDC).

http://data.energizer.com/pdfs/chpro.pdf

Because of this, it will require more significant reverse engineering on your part, to disconnect the AC PSU subcircuit and determine the appropriate DC output from it. Really I mean do it the other way around, determine the DC output from it, while charging 4 x AA, THEN disconnect it out of the circuit, let's call that point X in the circuit.

Next with that charger, or one that had a separate AC/DC adapter, you would hook your solar panel up to a series diode, then to a boost regulating power supply set to the correct voltage the charger needs. That would be connected to point X in the circuit, and the charger ground.

Supposing it might need 12VDC, the charger itself can do 4 x AA at 500mA. Rough guess is that when all is said and done, your 5V panel will need to output 1 amp or more.

Frankly, that is not a good choice. You'd be better off just connecting the solar panel directly to the batteries with a schottky diode in series. You'd not suffer as much loss, with the downside being you would need to manually terminate the charge once the voltage gets up to around 1.45V, except it'll only get there for 2 x cells not 4 as 5V just isn't enough for 4 cells to finish charging..

I'm stating this with the assumption that your solar panel is small and not going to be producing 1A. Even then, a 5V panel won't fully charge 4 x batteries as this charger design charges them in series. You'd still need a boost circuit to get the voltage up closer to 6V to completely charge 4 cells.

Can you just add another few solar cells in series with that one to get the voltage up a bit higher than 5V?
 
Last edited:
^ How high means what voltage? Doing what exactly?

Your two parameters, that charger, and a 5V panel, are both sub-optimal choices. I would go as high with solar panel voltage as you can reasonably go, because it's easier to shed voltage than gain it, especially on cloudy days.

0.5A @ 12V might be a good start, but solar panels are invariably changing in output depending on sun. A wide input range buck converter set to the input voltage of a charger that takes DC input (normally from an AC/DC wall wart) is the only simple route unless you reverse engineer what you have.
 
I want to say a big thanks for the help you guys gave me. This is a harder project then I thought it would be. So I will put this one hold.

I lastly have two things to ask for suggestions.

1.I learn in a unique way and the material I have now to learn electronics from does not give me a clear cut answer as to how the item works or how to test it and not go on yapping.

2.Could you recommend a good AA Solar charger I could use with my panel. I will only be charging one battery at a time since I won't be pulling a lot of power from it ?.

Again thank you for the help.
 
Last edited:
The most efficient way to do it would be to put a diode in series with the panel output and run that straight to a 1 x AA battery holder, then actively monitor the battery voltage -or- keep feeling the battery to pull it when it starts to get hot.

Not knowing what the expected current output of your solar panel is, this may work or this may risk overcharging the battery before you'd notice it got hot. It would be good for you to test this, see what you can get out of the solar panel. If it is a fairly low rate to the point where it would take several hours to recharge a battery, then you should factor for the average current over that many hours, to get an idea how much margin the solar panel has versus your expectations for how long it'll take to recharge a battery.

It would have been a lot easier if you would have just told us in the first place, exactly what solar panel you hoped to use including the specs for it.

Generally a "good" charger would at least use Delta -V charge termination but all I'm aware of, need more than 5V input. Perhaps someone else knows of one.

Otherwise there are so-called USB chargers that are trickle charging the cells. They're little more than a battery holder with a resistor in series and can be found on eBay for about $1 to $3. You'd still want a diode in series between the solar panel and the USB +/- contacts used for power input, but could just remove the USB plug to solder to the charger circuit board.

However, I would suspect that you want to lose the least amount of charge current possible, so I would try wiring it up without the series resistor to see what current it uses to charge without it.

There are purpose specific solar chargers that include the solar panels but their price is significantly higher. I am wondering if that's even worthwhile or if you would be as well off to just take a few charged AA cells with you?
 
I am sorry I did not include the specs of the panel. Other times I posted elsewhere They only wanted the voltage.

I did not want to have to monitor the voltage that's why I chose this model as I would be sleeping when the sun comes up.

specs: 2.5w 5v 500ma.

Also would you please explain the factoring part again in layman's terms as I like to keep things simple when explaining.

Again big thanks for your help I apologize if I am difficult to talk with as this is not my intention.

PS This project is at the house so nothing is going anywhere.
 
Your 5V/500mA solar panel would produce that in best case conditions. Outside, pointed at the sun (following the sun's track in the sky), no clouds, etc.

These are significant variables. If you expect it to charge well when the sun comes up, you'll need to aim it before you go to sleep, and keep re-aiming it.

Let's suppose you have a good day and get an average of 1.5W/hr out of it while the sun is up. That might be too optimistic, you'll have to try it and see.

Once you determine what power you're getting out of it in your worst case "needed" charged scenario, then you can figure out what charger you can use, or you can put more solar panels in parallel for more current, or more in series with a boost regulator board.

Since you don't want to have to monitor it, it does seem easiest to get a voltage boost regulator board, boost the voltage to 12VDC, to input to a charger that accepts that, which is *almost* any charger that comes with an AC/DC adapter that plugs into a barrel jack on the charger. Other input voltages are possible but 12VDC is by far the most common for a charger using an external PSU. Some of these chargers also include a car cigarette lighter adapter which is also a sign it can take 12VDC input.

Once you have such a charger, one that comes with an AC-DC 12V switching power supply, you can measure the current it consumes from that PSU while charging the needed battery(s).

You'd produce an equation, watts output from the solar cell, into a boost 12VDC regulator board, calculate the output as watts multiplied by the efficiency of the boost regulator board, divided by the 12VDC output to get amps, and then you see if the output current in amps is enough to power the charger based on the measurements you made of it running off a PSU instead.

My replies have been in a fairly random disorganized state because all the information wasn't presented up front in a concise manner so we could just do calculations instead of guesswork.

Frankly if this is only being used at home then I don't understand the need to charge batteries with a solar panel. It would only take a couple cents worth of power to charge a battery from an AC/DC switching PSU running on the AC mains power grid.

Another alternative that would give you a more consistent result would be using a solar panel, with a boost voltage charge controller, to charge up a 12V battery, then that battery is connected to the charger so it is in a known good, ready state whenever you want to charge batteries.

I think I'm about done with this topic because there's only so much I can add without wasting your time if you don't already have enough to go on. ;) It all starts with taking some measurements.
 
Top