i’m new to using my AC180, which will be used almost exclusively for power backup in power outages. I’m testing the devices I want to run off it (basic things) to see how much ACUAL POWER IN WATTS they are drawing from the AC port when plugged in VS. what the advertised wattage is. I’m confused on these readings. Can someone explain. This is about the 3rd time we’ve used it – only tested it twice to charge up our phones. Just received ~ 10 days ago new from Amazon.
I plugged in a 300W Imersion coil heater to heat up 13 ounces of water:
The Bluetti heated it up to boiling at 212oF in the exact 9.5 minutes the immersion heater advertised for this volume. i then unplugged the device. I figured that it would use about 48 Watts of stored power from the Bluetti (300W * 9.5min/60min) plus some unknown amount due to efficiency, but it used actually almost TWICE that amount.
I don’t see anywhere on the Bluetti where it says the WATTAGE it actually used start to finish, so I calculated it using the parameters on the bluetti itself.
It started at 80% of total power (1152W) but went down to 72% remaining right after in 9.5 minutes with a 300 watt AC device.
That’s starting at ~ 922 stored watts and ending at ~ 829 Watts = 93 Watts.
CAN SOMEONE EXPLAIN why this is almost 2x the amount it should use if the device itself is correct? I might add that the Bluetti during the heating of the water actually read that it was using between 309 - 313 Watts for 9.6 minutes which is 50 watts, not 93 watts. Thx
There are many variables when using an inverter from a battery source. First the battery - Bluetti power stations keep a reserve capacity to protect the battery, so when you see it read zero capacity, the reserve is not shown. Second the inverter - there is an efficiency loss when converting DC to AC. The Watts you see on the display is what the power station is providing to the device at that moment in time.
I have found the only way to compare is to use an AC power meter between your devices and the source. I have done this with my home refrigerator, a small low watt electric kettle, toaster and sandwich press. One test from mains grid supply and then from my AC180 & AC70. The readings were different between grid and Bluetti in all cases. One thing rarely mentioned is Volts; Here in Australia the grid supply is at a constant 240VAC, most times 243 - 245 VAC. The AC!80 outputs 230VAC at rest and I have seen it drop to the low 220s under a heavy load.
This means results are often variable when comparing between grid and power station. I have also noted differences between the AC70 and AC180 when powering the same device.
If your concern is run time, the easiest calculation is battery % used over time. i.e. my RV microwave uses 14% for a 6 minute frozen dinner, therefore 100% divided by 14 = 7.1 or 7 days use without a recharge. To play safe I would work on 6 days with a little to spare. I do the same with the other items mentioned from both the 70 & 180.
The math is simply Ohms Law - W=VxA (this can be transposed to find any value i.e. V=W/A or A=W/V)
Unfortunately, varying voltages, ambient temperature, battery state of charge, efficiencies etc. there is no simple calculation. In one way you are already on the right track by running a device for a time from a % to another % i.e 80% to 72% is 8%. Therefore divide 100% by 8 = 12.5. Your test took 9.5 minutes, so, multiply 12.5 x 9.5 = 118 minutes or just under 2 hours. Don’t be too concerned about Watts used, only that the inverter is big enough to provide the power needed.
Thank you for your reply. I have ordered an AC power meter at your suggestion and am going to test it as you did your devices and record those against what the Bluetti says. If I understand you correctly, the meter results are likely NOT going to match the Bluetti LED for all the reasons you mentioned, but at least I now better understand why. So TY
Still, Battery Capacity IS an important figure to me, which was the reason for my original concern re: the difference between what I calculated a specific device should use over the 9.5 minutes Vs. what it actually did use. Since battery capacity is advertised in W, it seems to me at least that the amount of watts a device uses/time is important .
I think I need some more testing on my AC180 using the AC power meter that’s coming plus I probably need to do multiple tests that (with use) will use up the battery’s power, then recharge fully and try again. Plus on the different devices I would actually use given a power outage.
Wouldn’t this give me a better idea of how this station actually works for different devices and I could then potentially better guestimate the actual wattage used from 100% to 0% for the different devices?
The display on the AC180 and the power meter between it and the device, or grid to device measure different aspects. The power meter tells you what the device is using, the display on the AC180 tells you what the AC180 is providing.
As also mentioned, testing is the best definitive guide. A constant load, such as lighting, heating and even a microwave when operating are easy to calculate over a given time. Items such as a fridge are not as they cycle on and off relative to set temperature, ambient temp, how often the door is opened and what’s in it. This is where the power meter helps as it not only gives you the Watts draw at any given time, but records the total Watt hours drawn over the test period.
i.e. The test on my home fridge shows 11.5 hours over the test from the AC180. (It is a 500lt fridge freezer) The ambient is reasonably constant as it is in an airconditioned environment. However if I test my 40lt Engel car fridge, in summer here in Au it can reach up to 60C in a 4x4 and the thermostat won’t cycle as the compressor is going 100% of the time to keep it cold. In winter, the opposite occurs.
In other words, you may need to get an idea in both environments. I test household once, but external (camping gear) in climate extremes. That way I know what to expect.
You don’t need to do a 100% to zero test to assess runtime i.e. On the home 60" TV, I ran it from 100% on the AC180 display to 50% and for 5.2 hours. This tells me I can expect approx 10 hours of total capacity. Hope this helps.
