FWIW. The main reason I built this flashing LED indicator, was to give a visual warning without having to 'read' a meter or gauge. When down to the stated 10.5 volts, the LED flashes.
ptn. I was viewing one night before making this unit & my 'power on' LED went out. (only runs on 3 or 4 mA). Thought I had a bad connection or broken wire. Turned out that the battery was down to 4 Volts. Yes, 4 volts. Took home, charged up as per normal = no probs....Now I don't have to worry.
HTH.
L.
ps. I have built a 'float charger' tho, so can leave battery on indefinitely.
pps. Total cost of indicator= <$6.00.