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b) For batteries left in storage off the radio, we recommend a monthly multi-meter voltage check to decide if they need topping up. If voltage drops below 7.0V, batteries should be recharged. Typically it takes it takes 3 months for a battery to self discharge from 8.0V to 7.0V.
Battery warranty and life
Batteries are warrantied for 12-months or 450 charge counts, whichever is soonest.
The actual life of a battery is affected by its operating environment and care, you should expect approximately 80% capacity at around 450 charge counts as a norm.