Which is the best battery chemistry for UPS ?

[Spirit]

I want to build uninterruptible power supply 12V, 0.5A, with batteries of 3-4Ah for home alarm sistem.
UPS is specific for using batteries because in normaln situation, batteries are always in stand by mode. Only if there is some fault, batteries must work.

I think that LM2574 is good choice for alarm power supply, and battery charger must have inteligent controls like MAX712 for Ni-MH.

Because of that, I am not shure if Ni-MH batteries are good for this type of usage?
I need long lifetime and 3-4Ah storage with max 0.6A current.

Which battery chemistry is the best for that UPS?

If anybady has any schematic of something like that, please share with me.

 

[techie]

NiMH and NiCd batteries have an annoying hysterisis which is particularly unsuitable for UPS use. Lithium is quite expensive. That leaves you with the LeadAcid type. That is why almost all UPS have LeadAcid batteries. They are cheap and relaiable and the sealed type do not require any maintenance.