Mine won"t over 6.47A discharge, (at startup) all setup correctly for 20A discharge. Well after some research and reading the manual (poor written) 3 times, seems like the 20A discharge only occurs and it depends on the actual battery voltage, from what I gather is in steps, up to 20A, as voltage decreases amperage draw increases. This is a bummer, this makes this unit a very slow capacity tester since I only use 12v batteries it will discharge from 5A to 6.7v at low voltage cutoff, I'm only keeping it because it can generate data records for future reference which is helpful if you ever need it, maybe for warranty claims and such. The cable gauge seems inadequate to maintain a 20A draw continuously without heating up IMHO, last but not least the fan quality soks big time the one on my unit makes a sound like the bushing or bearing not sure which type, is worn out and the propeller vibrates a lot. I have contacted the seller in the hopes that I get clarification on these issues and to get a fan replacement, I will update this post as soon as I get an answer. The model I have is the ZKETech EBC-A20, they also have the 40A version but is limited to 5 volts batteries. I own 12v batteries hence the one I got that can do up to 30v but limited to 85 watts on. If you are planning on charging a battery LiPo4 type or maybe LiOn, with this unit, and the charge on that battery is 10v or more, make sure you set this unit to charge at no more than .5A this is stated on the manual, I initially set mine up for 5A charge while the battery was at over 10v LiPO4 type, I started the test cycle and the voltage shoot up to 15v in a few minutes, without warning, luckily the unit survived and the battery over voltage kicked in! Update: Today as I continue to test the batteries, I ran a test cycle, same parameters are before and this time the battery voltage shot up to 19v! Seems that this started happening after I change the charging voltage from 5A to .5A! During the initial charge which is setup for 14.60v with a .10A disconnect set, IAW the manufactures specs. There is no reason why the voltage should go that high unless once the voltage is reached (technically it should cutoff at 14.50v) on the battery during charging and the unit stops the cycle it takes a few seconds for the unit to register this. The chart still shows the highest voltage as the starting voltage for the cycle, in this case it went up to 19v and that is what is showing as the starting voltage? Not sure if I'm expecting too much from this unit at it's price. As far as capacity goes IMHO is pretty accurate and the batteries capacity are withing specs so far.