With all the recent threads on batteries, I thought I'd recommend a useful digital multimeter bought to replace my ageing analog one The front of the unit suggests it'll read DC current up to a useful 10 Amps. Just do an eBay search on the model number (it's less than a fiver)
I got a multimeter, but for convenience while out camping on ebay you can get volt meters to plug into cig lighter sockets. Very useful and easier to deploy
if you can i would spend a bit more and get one that does dwell angle and revs as well Something like this http://www.maplin.co.uk/automotive-digital-multimeter-with-inductive-pickup-222059
