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Battery Charging Using Solar Power

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poxkix

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hello everyone! I am new here and I hope I came to the right place about my questions.

Regarding from the title, i'm trying to construct a solar powered charger that stores the power to the battery. My question is, what kind of battery should I use? I have search for a while and found out some information that 'golf car batteries' are the choice to use, how is this true? What are your inputs on this guys? Thanks.
 
Golf cart batteries are a good choice, they're designed to be robust in general and for deep discharge. Something like a car battery would be a poor choice because they're not designed for deep discharge, they're designed for cranking amps only to start the car, then the cars alternators immediately provides a float charge to keep the battery full. Another good choice would be marine batteries, specifically ones marketed as being for 'deep discharge'

Be sure you do your research, there's a lot that goes into the practicality of a solar battery charger that will determine it's lifespan.
 
Deep Cycle Battery

Here is all you need to know about batterys.

Basic principal about them.
 

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Golf cart batteries are a good choice, they're designed to be robust in general and for deep discharge. Something like a car battery would be a poor choice because they're not designed for deep discharge, they're designed for cranking amps only to start the car, then the cars alternators immediately provides a float charge to keep the battery full. Another good choice would be marine batteries, specifically ones marketed as being for 'deep discharge'
Be sure you do your research, there's a lot that goes into the practicality of a solar battery charger that will determine it's lifespan.

Yes it seems golf cart batts are the best choice.
If I were to use the golf cart batt, should I go directly for the 12v batt or two 6v batts?
Actually the battery will be attached by other components. It will be used to charge devices like phones, mp3 players, and Ipods also PIC's (Programmable Integrated Circuits) are involved to control the system. Maybe this info can help clear things.

Also "RV" battery. (deep discharge)
I think that will complicated, here where I live, we don't have RV's here so no source for the batt.

Here is all you need to know about batterys.
Basic principal about them.

Thanks for the image. Noted.
 
You should tell us what the capabilities of your solar system is, as it will help guide you to the best battery and size.

Its no good having a big battery bank and a small toy solar cell, the solar system needs to recover charge in the battery in a reasonable amount of time.

Any lead acid battery sitting around in a discharged state will die fast.

A solar charger is rather cheap to buy and would be hardly worth building your own.
 
You should tell us what the capabilities of your solar system is, as it will help guide you to the best battery and size.

Its no good having a big battery bank and a small toy solar cell, the solar system needs to recover charge in the battery in a reasonable amount of time.

Any lead acid battery sitting around in a discharged state will die fast.

A solar charger is rather cheap to buy and would be hardly worth building your own.

okay. Presumably the system will support 4 compartments. Each compartment will charge any kind of devices depending on what will be placed (ex. cellphones, ipods, and others). And there will be several PIC's, small lcds, and keypads too.
This kind of lcd:
**broken link removed**
 
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Misunderstanding............

I was asking about your solar cells that will be used, not what appliances the battery will be charging.

I cannot access your link posted above because it wont copy and scroll the link at the same time.

Dont use the "CODE" tags, just post the link direct into the reply box, the forum will do the rest.
 
Misunderstanding............

I was asking about your solar cells that will be used, not what appliances the battery will be charging.

I cannot access your link posted above because it wont copy and scroll the link at the same time.

Dont use the "CODE" tags, just post the link direct into the reply box, the forum will do the rest.

oh, sorry for that but maybe the information will help others to understand what the system does and can help me realize this idea

About the solar cells, I still don't have the idea what to use, i'm still trying to understand how the battery loses its power and how much panels does it need to charge with maximum efficiency.

link edited.
 
poxkix,

You have to define the load, the exact amount of current and over what time period it will be drawn for and how often those power draws will occur before anyone can say anything of a technical nature. What you want to do is so vaguely defined that you simply haven't given a place to start from.

ex. cellphones, ipods, and others
Is absolutely not enough information about the devices you will be supporting to start with.
 
poxkix,

You have to define the load, the exact amount of current and over what time period it will be drawn for and how often those power draws will occur before anyone can say anything of a technical nature. What you want to do is so vaguely defined that you simply haven't given a place to start from.

Is absolutely not enough information about the devices you will be supporting to start with.

What is my basis for defining the load and current?

The expected power draws is random, because there is no definite time when someone needs their device to be charged. So what I thought is during daylight is present it will continue to charge the rechargeable battery lets say the golf cart batt. when the battery is full, maybe a PIC and a relay is present to cut off the connection from the source to the battery.
 
What is my basis for defining the load and current?

The expected power draws is random, because there is no definite time when someone needs their device to be charged. So what I thought is during daylight is present it will continue to charge the rechargeable battery lets say the golf cart batt. when the battery is full, maybe a PIC and a relay is present to cut off the connection from the source to the battery.

The crucial point, which you still haven't answered, is how big the panel is - and what you might expect to get from it.

You would need an massive panel to make any kind of overcharging facility required, more likely the panel wouldn't be capable of overcharging it.
 
The crucial point, which you still haven't answered, is how big the panel is - and what you might expect to get from it.

You would need an massive panel to make any kind of overcharging facility required, more likely the panel wouldn't be capable of overcharging it.

I still don't have the idea how big the panel is. I was thinking of making the panel just big enough to charge the battery in maximum efficiency assuming in direct sunlight. But I do not know what to consider in a battery to be the basis for the computation to determine the size of the panel.
 
I still don't have the idea how big the panel is. I was thinking of making the panel just big enough to charge the battery in maximum efficiency assuming in direct sunlight. But I do not know what to consider in a battery to be the basis for the computation to determine the size of the panel.

You need to work backwards from your power requirements, and how long you expect the battery to be able to supply that requirement.

As far as panels are concerned you need to be aware of their overly optimistic specifcations, the spec is generally the maximum theoretical output, which you are unlikely to ever approach in practice, and what peak output you do get is likely to be for only a short time per day.
 
The expected power draws is random, because there is no definite time when someone needs their device to be charged.
There is NO WAY to proceed if you can't define a range of device power draw requirements. You have to START somewhere. Pick SOME point, how about charging an Ipod Touch battery full from 20% twice a day plus powering an undefined 500ma load for 2 hours. Pick sane starting requirements and then as Nigel said you can work backwards from there to define the size of the lead acid battery you'll need and the wattage of the solar panel. The biggest problem you'll have is sun coverage, most people think that solar panels are the be all end of all of free power. Have a weather front sit over your location for a week with full clouds and you might see that you have to define your requirements based on your specific situation. The specific location you'll be using this in and during what time of year will be a good place to start.

You're going to find very quickly that designing a reliable functional useful solar panel supply is a bit trickier than you first thought.
 
You need to work backwards from your power requirements, and how long you expect the battery to be able to supply that requirement.

As far as panels are concerned you need to be aware of their overly optimistic specifcations, the spec is generally the maximum theoretical output, which you are unlikely to ever approach in practice, and what peak output you do get is likely to be for only a short time per day.

I am suppose to use a 12v rechargeable battery. One question that is always in my mind is that how much of a panel is required to fully charge a 12v batt. in just a short time. Should a computation be done? Because I don't want to buy a large panel not knowing that it only needs a small one. I think the battery to be used is enough to be the basis for what size of panel to be used and how long the battery can supply the required poqer consumption.

I'm not really a know how about this stuff but I really need help to get this done.
 
Why we ask for figures on the solar cells or the demand on the battery is you need to be able to replace the power used in a reasonable time period.

As you have little idea of whats required, then lets say you need to replace the power consumed in 24 hours within 24 hours, (not a hard rule but a starting point)

So if you remove 5 amp/hours from the battery, then your solar cell needs to be able to replace 5 amp/hour within the next day.
Lets guess you get 6 hours of reasonable sunlight (winter time) per day 5/6 = 0.83 amp per hour.

As Nigel stated not many cells deliver their full rated power, so to be on the safe side lets cut the rated power by 50% this would mean you would need a cell that is rated around 1.6 amps per hour at 12 volt to recharge your battery each day allowing for a 5 amp/hour daily useage.

This would be somewhere around a 20 watt panel and about 500mm square in size.

As you see without actual figures to work with it is all guess work and your system might be well under rated or over rated.
The problem is when it is under rated and the battery remains in a discharged state as it will soon die.

Over rated and then you need the solar charger to protect the battery on the long sunny days.

It is always better to have larger panels than needed and a charger to protect the battery, but this cost more to setup, but makes for a reliable system.

Pete.
 
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Ok,,

The reply -
Another source for batteries are forklift trucks, my mate up the hill is too far from the mains and runs a wind/solar system and uses a couple of old forklift ones for his storage.

The question -
I have a solar cell attached to my wireless doorbell and it's failed to keep a pair of batteries charged (undervoltage i believe - doorbell is uses 3v and rechargeables I believe are 1.2v each. I've replaced the "C" sized cells with a PCB 3.6v Nimh 80mA. Well, I had.
We had a rare sunny day yesterday and the solar cell appears to have been working well because the loud pop I heard was the Nimh exploding!
As a result of this I think I need an over voltage protector as I checked the output of the cell and it was producing just under the 6v! Oh well, crappen happen.
Anyone got any suggestions of how to do this, or a link to a thread that'll help?
Thought about a Zenner but as far as I can make out they block until X voltage then allow flow, but what I really need is the reverse, something that'll allow flow until X volts.

Of course, I may be totally wrong in what I'm planning, but I'm sure someone will put me right - just bear in mind I'm an elecrtician with a SMALL amount of electronics knowledge!

Cheers, Hobbit.
 
You are right about the zener, and also wrong,.........confused yet?

For starters a zener diode will conduct backwards when the rated threshold voltage is reached.

What you can do is place the zener backwards between V+ and ground, this way it allows the battery to charge until the threshold voltage of the zener is reached, then any excess voltage above the threshold is shunted to ground.

It would pay to add a resistor in the V+ line from the solar cell prior to the zener so the current is limited to not blow the zener up.

Pete.
 
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