charging NiCd from solar cells - Electronic Circuits Projects Diagrams Free

mettam · 23rd September 2006, 02:21 AM

I have 3 Solar Cells connected in series the + is attached to a diode and the diode is connected to the + of the Nicd battery, the - of the solar cell is connected to the - of the battery (see attached photo to see what I did.)
Can someone tell me if I have attached the battery the correct way to the solar cells for charging.

Justin.

audioguru · 23rd September 2006, 02:42 AM

Your wiring is correct and the battery should charge if the solar panels can supply a total of 6.3V at 60mA.

mettam · 23rd September 2006, 03:20 AM

Quote:

Originally Posted by audioguru

Your wiring is correct and the battery should charge if the solar panels can supply a total of 6.3V at 60mA.

The Cells each are 2V at 200mA, considering they are connected in series of 3 does this mean they are supplying 6V at 600mA ?

Would you know what my NiCd should read once fully charged ?

If I look at 4 AA batteries they are about 6V and 1.500A. I'm not sure about how to read the Amps on my multimeter, I think it is telling me 1.5A. Could this be correct ?

Should these 4 AA NiCd batteries once fully charged read roughly the same Amp as 4 AA Duracell ?

audioguru · 23rd September 2006, 03:55 AM

Quote:

Originally Posted by mettam

The Cells each are 2V at 200mA, considering they are connected in series of 3 does this mean they are supplying 6V at 600mA ?

Of course not. Voltages add in series, currents add in parallel. It will be 6V at 200mA at noon on the equator on a bright sunny day with the solar cells pointing directly at the sun. The voltage and current will be less in all other conditions so the Ni-Cads might not fully charge.

Quote:

Would you know what my NiCd should read once fully charged ?

My old Ni-Cads were 600mA/hr and measured 1.45V each when fully charged and still on the charger. My new 2500mA/hr Ni-MH cells last more than 4 times longer.

Quote:

If I look at 4 AA batteries they are about 6V and 1.500A. I'm not sure about how to read the Amps on my multimeter, I think it is telling me 1.5A. Could this be correct ?

You are not supposed to short a battery with a multimeter. You are only measuring how much current the wires can or cannot handle (the wires might catch on fire).

Quote:

Should these 4 AA NiCd batteries once fully charged read roughly the same Amp as 4 AA Duracell ?

No. Removed from the charger their voltage will quickly fall to about 1.25V each.

Oznog · 23rd September 2006, 06:39 AM

The voltage tells you little about the state-of-charge. State of charge is not a simple thing to determine on NiMH. In fact, the voltage initially increases while charging, though only slightly, and near the time where it reaches full charge it actually decreases for a brief time.

It gets rougher with solar cells because the current is not consistent. You may get 200ma at first, but later in the day you have only 50mA. With the drop in current, the battery voltage will go down. Likewise, a fully charged cell that was at 1.25v under a cloud may be suddenly exposed to 200mA as the sun comes back. It may take awhile for the battery voltage to rise again.

You may have problems with overcharging, because those look like fairly small batteries. 200mA could be enough to dry them out if left on too long after fully charged. But then again this probably isn't going to be a setup used for a really long time.

hawk2eye · 23rd September 2006, 07:56 AM

Quote:

Originally Posted by mettam

I have 3 Solar Cells connected in series the + is attached to a diode and the diode is connected to the + of the Nicd battery, the - of the solar cell is connected to the - of the battery (see attached photo to see what I did.)
Can someone tell me if I have attached the battery the correct way to the solar cells for charging.

Justin.

++++++++++++++++++++++++++++++++++++
I would add:
The charged voltage , unloaded battery is a useless indication of the capability of the battery.

A good test would be to load the a recharged battery
with 10% of maximum capacity for 20 seconds while monitoring the battery voltage. A fully charged NiCd battery is not in good condition if its voltage drops by
10%.

hawk2eye

bananasiong · 29th September 2006, 04:59 PM

Hi,
Can this solar panel charge NiMH batteries?
Can they be charged and used simultaneously?

Thanks

audioguru · 29th September 2006, 05:51 PM

Quote:

Originally Posted by bananasiong

Hi,
Can this solar panel charge NiMH batteries?
Can they be charged and used simultaneously?

The battery is 1.45V x 4= 5.8V when fully charged. The diode adds 0.7V for a total voltage needed of 6.5V. The solar cells are only 6V so the battery will never fully charge.

The solar cells meet their spec for only 1 hour per day when it is sunny at noon.

It will take many days to partially charge the battery when it doesn't have a load. The battery will go dead if there is a load, because the voltage and current from the solar cells aren't enough.

bananasiong · 29th September 2006, 06:41 PM

Quote:

The battery will go dead if there is a load, because the voltage and current from the solar cells aren't enough.

I thought, when there is no load, the batteries will be charged by the solar panel? Why the batteries will go dead? The voltage and current from the solar cells aren't enough for what??

audioguru · 29th September 2006, 06:56 PM

Quote:

Originally Posted by bananasiong

I thought, when there is no load, the batteries will be charged by the solar panel?

Never enough charging voltage, very low average charging current. After many days of sunny weather the battery will never fully charge.

Quote:

Why the batteries will go dead? The voltage and current from the solar cells aren't enough for what??

You need to calculate how much load. For running a watch maybe? What about during bad weather when the solar cells won't have much output?

bananasiong · 29th September 2006, 07:07 PM

I'll use it to run a DC motor.
Three things are connected in parallel: Solar panel, rechargeable batteries (Ni-MH) and load (DC motor). I'll start with the fully charged batteries, the DC motor is powered by the batteries, then the solar panel keeps on charging to the batteries. Is this possible? I've never tried them out, I'm still planning.

audioguru · 29th September 2006, 07:14 PM

Do the math.
Is the average solar cell current more than the motor's current? I doubt it.

bananasiong · 29th September 2006, 07:23 PM

Of course no, but why do we need to concern this??? The motor is not running all the time, then the batteries will be charged when it is not running.

audioguru · 29th September 2006, 07:34 PM

The solar cells are in bright direct sunlight only at noon on a sunny day. They will charge the battery for only 1 hour each day! You could make a moving platform point the solar cells at the sun as it moves, then maybe the battery will charge 3 hours each day.
You don't say how much current the motor uses, you don't say how long you want it to run each day.

bananasiong · 29th September 2006, 07:45 PM

Quote:

Originally Posted by audioguru

You don't say how much current the motor uses, you don't say how long you want it to run each day.

I have not decided yet. The motor is a toy car motor. I just want to know whether it can be charged or not when it is running. It is not fully depends on solar energy. Maybe without solar cell, it can run 1 hour continuously, with the solar cell, maybe extra 5 minutes?

23rd September 2006, 02:42 AM	(permalink)
audioguru Experienced Member	Your wiring is correct and the battery should charge if the solar panels can supply a total of 6.3V at 60mA. __________________ Uncle $crooge

23rd September 2006, 06:39 AM	(permalink)
Oznog Experienced Member	The voltage tells you little about the state-of-charge. State of charge is not a simple thing to determine on NiMH. In fact, the voltage initially increases while charging, though only slightly, and near the time where it reaches full charge it actually decreases for a brief time. It gets rougher with solar cells because the current is not consistent. You may get 200ma at first, but later in the day you have only 50mA. With the drop in current, the battery voltage will go down. Likewise, a fully charged cell that was at 1.25v under a cloud may be suddenly exposed to 200mA as the sun comes back. It may take awhile for the battery voltage to rise again. You may have problems with overcharging, because those look like fairly small batteries. 200mA could be enough to dry them out if left on too long after fully charged. But then again this probably isn't going to be a setup used for a really long time. __________________ I thought what I'd do was I'd pretend I was one of those deaf-mutes.

29th September 2006, 04:59 PM	(permalink)
bananasiong Experienced Member	Hi, Can this solar panel charge NiMH batteries? Can they be charged and used simultaneously? Thanks __________________ Superman Returns.. http://www.supermanhomepage.com/imag...an-returns.gif My friend created this account for me.. LOL http://bananasiong.myminicity.com oh.. somemore http://bananasiong.myminicity.com/env

29th September 2006, 07:07 PM	(permalink)
bananasiong Experienced Member	I'll use it to run a DC motor. Three things are connected in parallel: Solar panel, rechargeable batteries (Ni-MH) and load (DC motor). I'll start with the fully charged batteries, the DC motor is powered by the batteries, then the solar panel keeps on charging to the batteries. Is this possible? I've never tried them out, I'm still planning. __________________ Superman Returns.. http://www.supermanhomepage.com/imag...an-returns.gif My friend created this account for me.. LOL http://bananasiong.myminicity.com oh.. somemore http://bananasiong.myminicity.com/env

29th September 2006, 07:14 PM	(permalink)
audioguru Experienced Member	Do the math. Is the average solar cell current more than the motor's current? I doubt it. __________________ Uncle $crooge

29th September 2006, 07:23 PM	(permalink)
bananasiong Experienced Member	Of course no, but why do we need to concern this??? The motor is not running all the time, then the batteries will be charged when it is not running. __________________ Superman Returns.. http://www.supermanhomepage.com/imag...an-returns.gif My friend created this account for me.. LOL http://bananasiong.myminicity.com oh.. somemore http://bananasiong.myminicity.com/env

29th September 2006, 07:34 PM	(permalink)
audioguru Experienced Member	The solar cells are in bright direct sunlight only at noon on a sunny day. They will charge the battery for only 1 hour each day! You could make a moving platform point the solar cells at the sun as it moves, then maybe the battery will charge 3 hours each day. You don't say how much current the motor uses, you don't say how long you want it to run each day. __________________ Uncle $crooge

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