Thread: How long does your battery last?

It's important to measure the stationary current drain, to get the real one you must lock the car with the bonnet open and measure after minimum 1.5 hours as the SLABS to "go to sleep". For a "sleeping" D2 up to 20mA is acceptable and knowing that and the AH of the battery you can make a rough estimation...

So it's good to know that cos parasitic drain on D2s is very common, one of the quite common but not well known issues is diode pack partial fault, it has 8 junctions in it and if only one or two are shot it will not affect the charging voltage but it will not be be "healthy" for the battery due to the AC component and it will create a parasitic drain through the shorted junctions, this is detectable only with oscilloscope cos it will pass a normal charging test without problems... i saw that 3 times out of 9 untill now with the oscilloscope on friend's cars which had greater than normal(between 60-180mA) drain but they all passed the charging test at different garages

here is some basic info Testing an Alternator With an Oscilloscope | Circuit Specialists Blog, i've seen myself those kind of images not once and the voltage measured with multimeter was nice 14 - 14.4V on the battery with running engine...just that my mates didnt know why the battery dies too soon

Put a ctek trickle charger on it. Problem solved. Much cheaper than continually buying new batteries. Or disconnect your battery when you store it. I disconnected mine, went away in my defender for 18 months, then reconnected the disco battery and it fired up first go.

Like the others have said there is always a small amount of current draw on D2s and these are the only ways to solve it IMHO.