Depends on what you're going to use them for...?

If you just want to experiment, get a marine deep cycle battery...Here on this page linked to are some other components you may find useful...

http://www.amazon.com/Solar-Panel-Value-BP350J-Replacement/dp/B0036Z7MFM

When your panels are "12 Volts", you can use these to charge 12 V or 24 Volts batteries, the last when you connect these in series.

The panels however, can supply around 17 Volts each (their MPPT) and you need to control the charge to not destroy your battery. For cables, minimal requirements are for 100 Watts/12 volts = ca. 10 ampere.

A MPPT charger gets you more net output, because otherwise the panels will work at the "real" battery voltage -

Good Question! Long Answer for this one!

if you have 50 watts or 500watts the ability to charge a battery is simply TIME. Once a battery is charged you have many options within the capacity of the battery.

First think about how you will use your stored energy or better yet, what are you planing on running with the battery. Basically your loads or uses for the electricity tells you how big a battery you want to charge. For the most part golf cart batteries are vary good for their price, should last many years. Your typical automotive or marine battery is designed to start engines not run things for a LONG time.

As for loads they will let you know how fast your battery is run-down and your input watts from any charge source let's you know how fast your battery is charged.

I am using solar and wind to charge 48vdc forklift lead acid batteries. We do shallow discharges @ 15%. The intent is to have many cycles over many years. Their are some other charging called equalize and pulsed charging but that is kind of long winded.

I hope this helps!

well i brought that http://www.gpbatteries.com/solar/SA_spec.pdf crap 2 C if it does anything or i have to dismount the solar cell and try to find a use for - - well it charges 2 x AAA or AA NiMH-s in 2 to 4 days (4h of afternoon sun at 60°North) t.m. the product is pretty usable . . . so

i gess the cost-back comes from me not buying the non-rechargables not so much from using solar power

so it's what power you replace with solar (it's likely pointless to run your washing machine from solar cells - at least as long as you have cheap night time "Electric Company Power" in hand)

http://www.hot.ee/rjc/files/CR4/PICT7600mfd.jpg -- no much time/need for the alternate NRG subject

so don't just build "something" - all exited of your new toy
i suggest it's worth to pay people already experienced in
the field to set up something (that has been proven worth of)

by the way for 2-nd pair of calculator solar cells i had to
re-create and reweld the (+)(-) terminal outs (primary came off
when i tested the strength of welding - confirmed weather it secured)
<< this is for indoor conditions

you likely want to take special care of the terminals area
(just as you do for your car battery) + what i cant tell you but the specialists can

I am going to disagree heartily. If the poster has anything remotely resembling a brain and handyman skills, all the experts are going to do is financially rape him and it will not be a pleasant experience. Off grid battery power is invariably lead acid. The costs of lead acid flooded cells are way lower than any other technology. To protect terminals from corrosion you can simply use the same methods and "tricks" used with car batteries and forklift batteries. I smeared Vaseline all over mine and never had a problem. it's cheap and just as effective as the more expensive solutions. If you insist on spending more money, go to Auto Zone or equivalent and buy the spray can and seal 'em up with that. The fact is, you can and probably should do this yourself. After the "experts" are done with you, it will be up to you to make any future changes and/or repairs. I checked the costs repeatedly of using the so-called experts. You are better off just building an overkill system (more panels and more batteries) than spending that same money on experts. You can get four times (or more) the system if you do it yourself. I took electrical engineering, both electronics and power generation/distribution. All you need to know I learned in the first few weeks of school. If you feel you need an education, the Navy NEETS modules are available online in pdf and they are FREE. They are designed for a person to learn the material on their own without an instructor.

Hi Jerrys,

Can you explain more about the effect of battery internal resistance? As for forklift traction battery, i understand the internal resistance is relatively higher. Does this mean it take longer time to charge higher internal resistance battery vs lower internal resistance battery? Or have to increase solar panel in order to get it full charge in time? I'm looking into using optima battery which they have lower internal resistance (like around 0.0025ohm) per battery.

I'll start by saying i would not spend my money on an expensive brand of battery. Seen lots of advertising hype and I'm suspicious. Optima may be a great brand or even the best, but in a solar system you need amp-hours and lots of them. You are better off with spending the money on Napa's big L16 batteries. The low internal resistance which car batteries have is very nice when you are starting an engine, a LARGE, INTERMITTENT load. In a solar application, it doesn't matter. You aren't doing huge intermittent loads, you are doing small(er) more continuous drains. Hence the need for deep cycle batteries. Anyway, the math is fairly simple if you only want an approximation. In reality, the internal resistance is not a constant. If you connect a small load to your battery, the output voltage will drop a little because of battery internal resistance. A larger load you will notice. If you battery bank is wimpy, it WILL drop below the low voltage cutoff level of your inverter and your inverter will go offline. (THIS IS WHY you need a big battery bank for solar systems. In an automobile, the alternator is doing everything after the engine starts. It's only for starting the engine.) Now, you'll go to check your battery, and it will be fine because NOW THERE IS NO LOAD!! If it's a 12 volt battery, it's going to be 12.8 volts x internal resistance. The internal resistance is not a constant and, in reality, if you graph battery voltage versus load with battery voltage on the y axis, it will arc downward as load increases. Kirchoff's voltage law explains this pretty clearly. All of the voltage "consumed" by each device in the circuit must add up to the battery voltage. That battery is both a source of voltage and a load because of internal resistance. The voltage consumption due to internal resistance must also be counted in the calculations. I can't emphasize this enough, a solar power application is going to take more battery power than you think. Forget small batteries. It really doesn't take much in the way of discharge for a sudden surge to trip off your inverter due to low voltage. Your batteries total output from a fully charged state will depend on how QUICKLY you discharge them. Check battery ratings, they'll be for two different time periods. Say you get two hours at 100 amp -hours. Thats 200 amp hours. Now lets say you discharge at only 10 amp-hours. will you get 20 hours? No, you will get much more than 20 hours. Look into this. A GOOD battery vendor or manufacturer of quality deep cycle batteries will put this info out there.