Battery Meter / AC200Max

Hi Guys

I have been trialing my AC200Max with my camping fridge and I have been getting some unusual results.

I have read that the AC200Max does not read well at low watts

The fridge draws about 32 - 40 watts when starting from warm, and as such would expect the worst performance of the AC200max to be in the 50 - 60 hour range.

I plugged this in on Sunday about 2.00pm with fridge on coldest setting and checked about 8.00pm, and the fridge was down to cold (with ice forming inside) and AC200 was reading about 88% so seemed OK

Checked in morning and was down to about 60%, and went out for the day.

That evening 30 hours after turning on, checked and it was off and the battery was reading 0%. No other loan, AC turned off.

can anyone recommend a watt hr data logger so I can put this on to see if there was some fault / peak load, or whether the AC200 is not recording correctly, or… maybe the battery is not performing to spec??


Terry Archer

From official documentation:

Running time = Battery capacity × DoD × η ÷ Device rated power DoD refers to Depth of Discharge and η is local inverter efficiency.
For AC200MAX, both DoD and η are 90%. If you run a 1,000W microwave oven with it, the running time will be:
2,048Wh × 90% × 90% ÷ 1,000W ≈ 1.65hrs

  1. The formula is NOT suitable for inductive loads with compressors, like refrigerator, air conditioner, etc.
  2. The above data is for reference ONLY.

In real AC inverter efficiency is not 90% on the low power. Actually inverter can use 30W yourself so the result can be less.

To give a comparison our full size single door fridge freezer lasts just over 24 hours on AC from a full charge. This is in part due to the overhead of just running the Ac200max with AC on, even before any power draw. If you take the 30w figure above , 24 hours x 30w = 720W just to run the Ac200max over 24 hours. Similar systems have the same limitation.

Due to this we added a b300 battery to allow for dull days and give more flexibility.