# Capacitor for high current discharge

• ramonegumpert
Two... it sounds like you're trying to protect your battery from overcharging. If the voltage is lower than the regulator needs, then there will be no charging.f

#### ramonegumpert

Dear Experts

i have a solar panel but the current is not high enough .

I have about 5 volts to charge giving about max 100mA (specs).

I am thinking of using a Capacitor to store all the low currents such that when the capacitor is fully charged, I need a circuit to discharge all the high current in the capacitor to the battery.

I am not sure if this is the same as hooking up the panel to the battery without capacitors.

I also not sure is there a minimum current (at 5 volts) the lithium ion battery would accept current? Am I right to say any small amount of current will charge the battery at the right voltage and the only difference is how long it takes to charge?

By the way, I will add a rectifier to maintain a steady voltage.
But does this not mean that if voltage is not sufficient, there is no charging at all vis-a-vis without a recitifier ?

Eg. If I use a 7 volt rated solar panel, connecting to a rectifier taking about 2 volts, the remaining 5 volts will charge the battery. But if the sun is not strong enough, producing only 6 volts or less, the rectifier may not have 5 volts output . What happens? No charging?

Thank you for reading my question.

Have a nice day.

Best regards
Pascal

i have a solar panel but the current is not high enough .

I have about 5 volts to charge giving about max 100mA (specs).

I am thinking of using a Capacitor to store all the low currents such that when the capacitor is fully charged, I need a circuit to discharge all the high current in the capacitor to the battery.

I am not sure if this is the same as hooking up the panel to the battery without capacitors.
It usually is no different.
I also not sure is there a minimum current (at 5 volts) the lithium ion battery would accept current? Am I right to say any small amount of current will charge the battery at the right voltage and the only difference is how long it takes to charge?
Li-I batteries are very fastidious and fussy, and are not safe to experiment with. They are easily damaged and can catch fire if conditions are not to their liking. https://www.physicsforums.com/images/icons/icon9.gif [Broken] Can you use NiMH cells instead?
By the way, I will add a [strike]rectifier[/strike] regulator to maintain a steady voltage.
But does this not mean that if voltage is not sufficient, there is no charging at all vis-a-vis without a recitifier ?
If the voltage is lower than the regulator needs, then there will be no charging.

A 7v panel delivering 100mA should be about right for 5 x NiMH cells, each 1.2v. Place a current meter in series to verify that charging is proceeding okay. No regulator required.

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By the way, I will add a rectifier to maintain a steady voltage.

Uh ... I thought solar cells produced DC voltage, no? You have one that produces AC voltage?

Dear NascentOxygen and Phinds

Sorry, my bad, I incorrectly used the word 'rectifier' for regulator.

NascentOxygen has given me great advice. I really appreciate your kind help.

By the way, I could not find a 7V solar panel at 100mA. The store only has 6V at 100mA.
So, I bought another 4 x 5v panels rated at 100mA and connected them as 10v pairs.
Because of the potential difference, I drop the voltage down using a regulator at 5.5v and connected a 1 farad capacitor at 5.5v before regulator whose output goes to charge the battery.

Based on the voltmeter, it seems that adding a cap stabilized the voltages a bit especially when the sky is cloudy. Is this observation making sense?

If I add a same cap after the regulator, would that make it even more stable? But what happens when the sky is too cloudy? would that not make the capacitor discharge to the solar panel? So, I added a small zener diode to block the discharge.

Still my phone, which has a larger lithium battery than iphone, is DIScharging rather than charging my phone.

That is why I wondered is it due to the position I placed the diode ? I could not understand why the phone is not being charged. For example, after 5 minutes, the charged % actually dropped rather than increased.

Best regards
Pascal

By the way, I could not find a 7V solar panel at 100mA.
I didn't suggest you would. It was you who nominated that figure of 7V.
The store only has 6V at 100mA. So, I bought another 4 x 5v panels rated at 100mA and connected them as 10v pairs. Because of the potential difference, I drop the voltage down using a regulator at 5.5v and connected a 1 farad capacitor at 5.5v before regulator whose output goes to charge the battery.