Check battery first, first charge it using a suitable charger (not the board you are dealing with), check voltage should be about 12.5 to 14 V), then disconnect your car battery from your vehicle and hook the SLA battery up to your vehicle (already warm) and watch voltage as you power up the accessories in your vehicle (dont try to start vehicle) - if voltage drops below 10V while trying to power accessories (fan blower, dash, interior lights and headlamps) you have a defective battery.
