KaitoBT500 Replacement Rechargeable Battery Pack for KA500, KA550, KA600 Voyager Radios

How long can this last in storage without being recharged?

I see mixed reviews. Does this or does this not work with the KA500?

I have an HQ radio with the same exact shape and features as a Kaito. But does anyone know if this will interchange? Same radio, different brand.

My kato ka500 has a single rechargeable battery somewhat larger than a aa. the picture shows this as a battery pack. is it a single battery that fits