Why lead-acid? Why not try Ni-Cd batteries with their zero maintenance demands?

These are large truck batteries actually. Ni-Cd might just be too small. They are to power a 12V supply at 10Amps for at-least 2-3 hours.

Consider switching to marine 'domestic' storage batteries instead. These have a gel-based electrolyte and require negligible maintenance. Unlike a motor starter battery, which is designed to give a lot of current for a short time, the marine domestic battery is designed to give a lower current over a much longer time. 30Ah is well within the capabilities of a single battery pack. UK retail prices start from about £55GBP each, including taxes.

Do you mean the 'Low maintainance' types?

They are known to have a very low life and sometimes ruin themselves very early. I do not know that for myself but all the reviews are pretty bad.

There will also be a risk of pressure build up causing cracks and leakage since these batteries will be placed out of human reach.

Do you have a website i could visit for where you told me about the above battery?

Mrinny,

I'm making an assumption that this is some sort of redundant power supply.

Based on this assumption, I would suggest you look at the following site:-

http://www.yuasa.com.au/asp/index.asp

and use their product guide to find the most appropriat battery either AGM or Gel batteries in the SWL range.

Without more information on the application of the battery there is little else of value I can add.

Sapper.

Here are some tips that could help:-

1) Use sealed lead acid batteries. Or Gel, which are also sealed. Best are "Leisure" batteries as they are better if ever deeply discharged, normal ones do not like this at all....

2) never charge to completely full, therefore you need to put a bigger battery in than your needs dictate. When charging make sure that it never drops below 12.6 volts (assuming a 12 volt battery) and never goes above say 13.4 volts when charging, this will give about 70% capacity at best. (Normally one would charge to about 14.4 volts, but some gassing will occur then)

3) prevent major changes of temperature with good insulation. Monitor the temperature with an attached thermometer.

4) read the manufacturers data on temperature and charging and monitor the charge cycle accordingly. High temps mean a lower charging current is needed.If you stick to the voltages I mentioned, you can forget changing the charge as that will be within the allowed range.

5) If not using sealed batteries, remember the gas is explosive, no smoking or naked lights and good ventilation at all times....