Quote:
Originally Posted by supernovatx
Battery + connected with - disconnected. Attach multimeter to positive terminal, neg to battery ground and I'm getting -00.1V is this to much loss?
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no idea what you are measuring here and what is connected and disconnected. 0.1V is NOTHING - so you are obviously not measuring with any load. In general the loss needs to be measured while you draw a huge load (cranking). Anything else is pretty much meaningless.
Your voltage numbers in your first post sound O.K. and it seems you battery is charging - or better said; it was charging at the time you took these measurements. I have not seen any clear evidence that your battery was empty. A 70% charge is pretty normal for a car battery. And it should start a car just fine.
What exactly is the nature of the "car won't start"? Does it crank over or not? Does the cranking sound slower than normal when it happens? The reason I am asking this is that you could have an issue (maybe intermittent) with your starter or starter relay (the big one attached to the starter motor)
To reallly get a good idea you need to measure the voltage at the battery while cranking. This will tell you if the battery can supply the current demanded by the starter. If the voltage goes down quite a bit it points out a bad battery (high internal resistance).
Next check the voltage at the starter motor while cranking. And if the loss is more than a couple of volts compared to the measurement at the battery you either have a bad relay or bad cabling.
Then you can measure the voltages across the relay while cranking to find out if it is the cause for the drop. In a healthy system the battery voltage shouldn't drop much below 11 volts while cranking and the loss from the battery to the starter motor shouldn't be more that 0.5V.
Ingo