Hi,
I’m a live camera operator and I shoot outdoors, we hook up our gear to a powerpack and leave it running for the whole day, pretty much close to a constant load.
At the moment I borrow gear, but I’m looking to purchase my own powerpack and I just have a question for the runtime. The unit I’m using atm (not Bluetti) is rated for 512Wh, the rated draw we have is roughly 30W constant, but the estimated runtime is only 9 hours? And the estimated runtime was correct, at the end of the day after 8 hours the pack was mostly depleted.
But I’m not sure why this is the case, if my maths is correct on paper we should be getting 17 hours of runtime (512/30) I know you get conversion losses but it’s looking like 50% efficiency here. Would expect 80-90% or something. The pack is a newer pack too so I don’t think the battery degradation is that much of a factor.
What am I missing here? I was looking at the Bluetti AC50B which is a 448Wh pack, but I’m not sure if it will be enough if that is the real world use case. What are your experiences with Bluetti powerpacks and do you think I may need to size up? Prefer to have a pack that can be rated for at least 10 hours of use in my case, sometimes the matches go overtime and should factor in battery degradation too.
The first Q. is; Are you running your camera gear from AC or DC supply? This makes a difference in the calculation.
Second point, low loads over time, such as 25-30W, are less efficient on a power station, than higher loads over shorter time. This is due to self consumption and efficiency loss.
Here’s an example; I have a Bluetti AC70. it has a 768Wh battery and 1,000W inverter. It is used on my home Fibre internet input, WiFi router and Home security base station. The total Watts draw using 240VAC (AU) is 25-27W.
If you divide 768Wh by 25W = 30.7 hours. However, I have run tested the AC70 to 0% charge in 24-25 hours. (not connected to the grid) It is normally connected in UPS mode, pass through power and backup for grid failure.
You are always better off, calculating your total Wh use (worst case scenario), then add 25% safety margin.
For your use, I would go for at least 750Wh of battery. Which makes the AC70 ideal.
I should note, Yes, the 1,000W inverter is overkill for my use. However, it’s also a “balancing act” with battery capacity. This was my number one criteria, in giving 24 hour backup.
Yeah I read a bit more and didn’t know how much the inverter soaks up, and the power station itself also takes about 10w to stay on (AC50B) so you are right the longer the use case the less efficient it is.
Also most packs limit the total usable capacity for longevity reasons, so your looking at 80-90% out of the box
For the above example it is from AC supply, but I may be able to run it off the car port to avoid AC. I’m getting mixed answers whether it will save me more power, DC to DC is usually more efficient but it can vary depending on what unit you use and brand, it may be not much better than DC to AC. I guess I’ll just have to test and find out ahah. But thank u for your response.
These power stations are primarily designed to provide inverter AC power. That they are powered by battery allows the addition of 12VDC output, but that is even voltage changed as the batteries are a higher voltage for the inverter.
Using the cig socket 12VDC @ 10A for 120W may work, but often it is not as economical as AC loads.
Not to mention, I’m not in favour of using cig plugs, they’re not a positive contact plug, easily vibrated or knocked loose. Whereas an AC plug takes a lot more abuse. Plus, I’ve seen an Engel 12V fridge cig plug get hot enough to not touch with a 40W load. Why I’ve replaced that one with Anderson 50A, not powered by a power station, but by an auxiliary 4x4 deep cycle battery.
Brand name also matters. Some of the cheaper, lesser know units have terrible efficieny. Theres 4 or 5 manufacturers of these types of units that capture the majority of the market share and a lot of it has to do with the quality of their products.
100% agree. There are cost cutting measures at the component level and also along the supply chain potentially in order to maximize profit margins. All you have to ask yourself is how is Bluetti able to supply a power station with an inverter, MPPT charge controller, and a kilowatt battery at only so much dollars, yet a quality MPPT charge controller and inverter from say Victron is the same if not MORE than the entire Bluetti unit. They cut cost somewhere.
So you have two things. The inverter conversion efficiency (or better yet conversion loss) which is what % of battery is lost converting DC to AC. The battery is natively DC, its using the inverter to convert the 12V battery from DC to AC. This process alone is not 100% efficient. This is listed in the manual generally and its 85% +/ a few percentage points for the AC50. Next you have the idle draw of the inverter itself. This is essentially what the AC inverter itself uses just to keep itself on. Think of it like the fan connected to the circuit board. It draws its own power to cool the unit down, and pulls from the battery. The inverter is no different. It needs a power source. The larger the inverter, the more idle consumption. A lower wattage inverter may only consume 0.5A@12V, but a large inverter (say 3000W one) may consume 2A@12V.
Let’s assume the idle consumption of the inverter itself on the AC50 is 10W That would be 0.83A@12V.
Using ChatGPT (take accuracy with a grain of salt) but the inverter size is 700W which corresponds to the typical range of that inverter. A 30W constant load would mean the battery needs to supply a minimum of 30/0.85 or 35W to convert from DC to AC power. Now throw in the 10W which is required to run the inverter. So that’s 35+10 or 45W.
30/45W= 66% total efficiency at 30W constant load.
The larger your inverter the more inefficient your power station will be at handling lower constant AC loads. It is simply inverter overhead/system sizing mismatch. The ecosystem expects you to use larger loads with a large inverters and smaller loads with a smaller inverter. If you need a power station that meets both high and low demands you will suffer at one end of the spectrum. A larger inverter that uses small loads will be inefficient, while a small inverter that is always at the top end will be inefficient. If I stress my EB3A inverter using my space heater at level 1, it consumes 550W, but its efficiency is at best 65%. On my AC180, its nearly 90%. But on my AC180 a 20W load is 40% efficient, but on EB3A its 70%. Your system should be sized to what you use most commonly. If that 30W constant load is the most important to you, a smaller inverter is necessary. If you have the ability at all to charge from a DC source, like USB type C, that would always be your best bet because DC is the defacto most efficient way to charge low wattage consumption devices. I bought a Dreo fan which I can convert from 24V AC to 12V DC. It uses around 26W@24V on AC on full but only 13W@12V, but since my AC70 uses around 10-12W to just run the 1000W inverter PLUS i lose another additional 10-15% converting DC to AC power, my overall efficiency is just 65% or so (26W / 26W + (10W for idle inverter + 4W for conversion loss). My fan plugged into DC does not need to convert to AC so I gain 15% immediately back. I generally run my Maxxair fan and Dreo together to improve efficiency and airflow. The maxxair uses around 27W, and the Dreo 13W, while the idle consumption (how much the DC side uses, instead of AC inverter side) is about 5W, so the overall efficiency is essentially 40/45 or 88%! Now if I JUST ran the fan at 13W, I’m only getting 13/18 or 72% which is getting close to the AC efficiency at that point. Keep in mind the more important aspects are runtime and solar regeneration potential. Even at 72%, the runtime of just running the Dreo fan at 13W, means the overall power consumption is 18W. That’s still 27 less constant watts being used. The runtime would be 42 hours just running the Dreo fan but if I run both Dreo + Maxxair its only 17 hours. What’s better 88% @ 17 hours or 72% @ 42 hours?! The better question is when do I need to run them. Efficiency is nice, but who cares about efficiency losses if you have the ability to easily regenerate that power back on a full sunny day or it can’t even make it through the night.
If your vehicle has a small inbuilt inverter, don’t use it. They are often not pure sine wave = dirty power = not good for sensitive electronics.
Cig sockets powered by the start battery. Some vehicles have 2 or 3 installed. They are often in parallel, which means the output is still 120W max from all of them, not each.
For both of these options, you risk draining your start battery to the point of not able to start the engine. Start batteries are not designed to provide constant power of long periods of time, without the engine running.
As mentioned, and, Your need is a constant low wattage supply, therefore, inverter size is not critical. However, capacity is and I’ve shown what you need earlier.
The other good thing in using your device AC power bricks is, a regulated correct voltage output, if they were supplied with the device. Using DC from a 12V source will only give you 12V and or 5V USB and you rely on your device internals to manage that load as these outputs are not regulated output, other than a maximum output.
I’m not using a car ahah, but still interesting to know
I think for my use case, a AC plug is the way to go. Some of the sites I will be visiting do provide a powerpoint so it’s better if I just have my set up to assume an AC source from the get go. It’s not the most efficient but I can just get a larger pack as you suggested.
I’ll need two power packs for redundancy anyways, so I think I’ll purchase the AC50B, see what real world numbers I get, and if it can’t do 10 hours on a single charge I’ll get the AC70B. Not all my shifts are 8 hours long so a smaller pack isn’t bad either.
Which makes the AC70 ideal.