Check your local tool supplier or even Harbor-Freight(item # 91129 $79.99 on sale $49.99 now).They have a 500amp Carbon-Pile unit(I got mine at Harbor 3yrs.ago for $70)You need to be able to load the batteries to 1/2 the CCA to test them properly(625cca = 312amp load).The small testers will give you a ballpark,but not always accurate,dependable test.For guys with electric-carts,where the battery is everything,the $70+ is well spent.Hope this helps.