Your Questions About Solar Panel Installation

Mary asks…

can a 50 watts solar panel charge a 100amp battery?

i did an installation of a 50 watts solar panel to charge a 100amp battery but the battery was not charging. i want to be sure that a 50 watts solar panel can charge a 100amp battery

ssadmin answers:

Sandy is correct. If you have a 12 volt battery, and the solar panel puts out a max of 8 volts, you will never charge the battery.

In real life, you would put some electronics between the array and the battery to control the rate of charge, when you get the voltages corrected. If not, you could overcharge and damage the battery.

Actually, if you did this installation without even checking the voltages, you need to get it reviewed by a good electrician or electronics technician.

George asks…

Solar Installation – Novice (needs help)?


I'm preparing to install solar power into my computing room as a method to reduce electric cost's and as a backup in case of a power failure; I decided this as my documents we're corrupted when our Power Supplier fed a small 100W's into our entire household, damaging my SSD (data drive – non-mechanical).

So far I snagged up a couple of online bargains to get started such as some 12V 90AH Battery's and Solar Panels.

I currently have:
2 x 12V 90AH Battery's (

2 x 12V PV 80W Solar Panel (

In order to power up to a 1kW – 240V appliance, how would this need to be setup / what else do I need? I'd prefer to draw the power from the mains during daytime, and automatically switch to the solar / battery's after sunset or a power-cut.

The power drawn won't likely reach 1kW for more than 10 minutes, depending on the task I need computing; else it will drop to around 230W an hour.

Also how many hours of power can I get from a single day's worth of charging, let's saying I'm using 100W an hour? (an average of 11 hours sunlight).

If you have any advice / answers then please let me know, as I'm lost to what needs doing next.

Kind Regards,


ssadmin answers:

Lead acid batteries are 50% efficient while charging, you will also need 24 V to charge each 12 V battery. You can expect maybe 8 hours of usable sunshine per day which if you assume you will get a full day of sunshine each day then you would need at lest 21 of those panels. If you assume a 50% chance of having a good day of sunshine then you would need enough battery power to last 5 days so you would need 24 of those solar panels but if you assume you needed to recharge all those batteries on the sixth day then you would need 388 of those solar panels.

A purely solar powered solution should cost about $30,000 not including the energy needed for air-conditioning.

I would suggest you buy a surge protector and a UPS instead. If you really want to be able to take a long term hit on the grid, have a transfer switch and a generator that can be started when you're on UPS battery power. Select a tri-power generator and connect it to your natural gas line, if the natural gas line is broken, you can use propane or gasoline with the same generator. In the future there will be hybrid diesel generators that can run mostly on natural gas with just enough diesel for the compression ignition and could switch to running entirely on diesel or bio-diesel.

Joseph asks…

photovoltaic solar panel system?

What is the average installation labor cost for photovoltaic solar panel system, on a house that is 2000 Sq. Ft. Who installed it, how long did it take.

ssadmin answers:

It depends on the size of the system. $3/watt is a typical installation price in most parts of the country, after rebates are considered. In wealthier areas, or where rebates are higher, it may be more. That's only for the labor, not the materials. With materials included, it will be more like $8/watt.

If you want to see a breakdown of how much our system costed, it's at . But we self-installed, so it's not truly a fair comparison.

Nancy asks…

[DIY] Solar Installation – Help Needed.?


I've now got a 12V (Open Circuit) 80W solar panel, two 12V 90Ah battery's, 12V DC to 240V AC – 1000W Inverter, and a 10 Amp Charge Regulator (12V).

But I'm baffled as to how I setup it, I've got a rough idea in mind:

Is the above correct? If so, how do I insert the second battery into the system? Otherwise, if I'm wrong then what do I need to correct it?

Kind Regards,


ssadmin answers:

There are three phases to charging a lead acid battery, the bulk charge, the absorption charge and the float charge. The bulk charge is at a constant current and the voltages can be as high as 24 V, the absorption charge is at a constant voltage, usually 14.4 V which is the voltage a car alternator will provide. At best, your set up could do a float charge at about 13.5 V. The danger is overcharging, you can damage a battery by charging too long at 14.4 V and even at 13.5 V, it's not a good idea to charge forever. Lead acid batteries are fairly forgiving which is why they are used so often, especially the ones you can top off the water in the cells but even with lead acid batteries, a charge controller and frequent testing helps a lot. Just connecting a 12 V battery to a 12 V regulated supply won't charge it, the voltage has to be higher. Don't try to hook your inverter output to the mains unless it's an inverter that can synchronize with the mains, the grid tie inverters will synchronize with the mains and are of course much more expensive. The inverters in UPS systems that are on bypass all the time and only switch on when mains power is lost have a circuit to detect when they are in synch so they can switch back to the mains but often don't have a means to stay in synch. We used to use a light bulb between an alternator and the mains to detect when they are in synch but the advantage of a mechanical system like an alternator is that they will tend to remain in synch, inverters don't have a natural mechanism to do so.

You can hook up the second battery in parallel with the first. It's a good idea to rig up the wiring so you can disconnect one battery without disconnecting the other so you can take charge measurements ( just disconnecting one lead is enough, perhaps the ground so if the lead touches anything, you're still fine, you just want to read the voltage across the battery some time after disconnecting it to see what it's charge is, the chart in the link is 3 hours after disconnecting the battery ).

Sharon asks…

How much does it cost to install solar panels in your home?

Installation plus the solar panels, roughly?

ssadmin answers:

Basically, you're looking at about $10-$12 a watt. So, for a 2 kilowatt system (small house with minimal demand), you're starting at about $20K. And, for a 3.5 kW system (most common size), you're starting at about $35K. An especially large house might require a system as big as about 5 kW (about $50K).

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