too low to start the engine - not sure what the actual voltage was at that point, but it charged right back up (this happened on at least two occasions when we had an electrical gremlin - since resolved) I can see no difference in the voltage readings from new till now as a consequence. We have a smart charger and I make it a point to top up the batteries on a monthly basis. An interesting point made by an Optima tech at one of the races was that it would not hurt to EQUALIZE these big Optimas about once a year. He said this was not the official company position but in his lab testing it had proven beneficial - I tried it for two hours on the start battery last season but couldn't tell any difference one way or the other - might have needed more time.