Our batteries and inverters are covered by a 10-year supported guarantee.
The InstaGen batteries can be discharged 100%. However, we would not recommend to regularly discharge the battery below 10% as this can shorten it's lifespan.
The batteries have a usable capacity depending on what they are rated to in kWh. The inverter limits the charge and discharge rate and is rated in kW. The max charge/discharge rate is 1 x inverter size. A 5kW inverter and 20kWh battery has a max charge-discharge rate of 5kW/h. 5 kW is equivalent to drier, washing machine and lights on at the same time. If heat pumps are also added to the equation then you will need a higher charge/discharge rate.