RV Full Time Job: How Long Will MacBook Pro Last Connected To 12V Battery?
Working while camping off grid might be tempting idea, but how long will your battery last? Let’s do some experiments and see how long you can work with a MacBook Pro and one additional external display connected to a LiFePo4 100ah 12V battery.
Goal: work no different than every day, just be connected to the 12V (12.8V to be exact, as this is LiFePo4 battery) DC battery and see how long can it last.
Details: programming work (no video editing or gaming, which could increase power consumption a lot) on a 100ah LiFePo4 battery with a MacBook Pro 16" i9 (2019) with additional external 24" display (Dell U2415).
Experiment 1: Use 12V DC to 230V AC power inverter for both laptop and external display
Firstly I connected 300W inverter to the fully charged lithium battery. Then I connected regular MacBook Pro charger cable together with external monitor cable to the inverter. Below you can see the experiment start time and battery status with a load after turning on the inverter.
This was my first try of the new 300W Giandel Pure Power inverter, so I got the unpleasant surprise. It started making some strange popping noise after couple minutes of working, and popping went faster and faster, so I quickly disconnected it to avoid fire or destroying my MacBook. I’ll try this inverter again a bit later and I will write some article or review about it. I suspect that this inverter may be not pure sinus, even though it is marketed as such. But this is just a guess, I am not sure about that. Some devices do not work well with modified sinus — I know that the MacBook Pro and Dell monitor which I am using for this test would not work with modified sinus inverters — I have already tried that with another inverter — it was not powering these devices at all. My watt meter display shows cut numbers (see photo below)— I’ve never seen this behaviour before. If someone know the reason, please explain in the comments. With every other socket this watt meter numbers look fine, without being cut.
Let’s get back to our main experiment. I wasted 5–10 minutes with this issue and connected another inverted (also not tried yet after receiving from Amazon). Let’s see how this one handles the load.
So, this inverter works fine and I was able to work without any interruptions till lunch. You can see the time and battery status below (12:15 — 13.1V):
After turning off the inverter (see that small bulb (photo above) on remote control, which is connected to inverter with a cable) you can see that it shows a bit higher voltage and percentage (no more load on the battery): 13.2V.
Let’s turn DC to AC inverter back on and continue working after the lunch:
I had one more break with inverter turned off, but in order not to make this article too long I’ll just write results at the end of the working day (8 hours of working — easy to be sure, as I use time tracker). So, at the end of the day battery shows 12.9V and 73% under the load (inverter is not turned off yet):
I think we should not look at all to the capacity left percentage, which battery is showing, as I have found a lot different voltage to percentage chart (see the colourful table). After completing this experiment, I can say that this conversion table looks a lot more correct, than my battery BMS percentage readings. After disconnecting the load (inverter) and waiting several minutes (see photo below) battery shows 13.1V, which would translate into 40% capacity left, if we believe this table.
Second day! I left MacBook disconnected during the night, so it would be similar situation to camping off grid somewhere in the wild. Only 67% left from the laptop battery — not very nice considering no one was using it at all and it was 100% charged in the evening :(
External display was plugged into laptop, but power was turned off, so strange that so much energy were wasted somehow.
Let’s connect everything (battery shows 13.0V):
Lunch time! 12.7V. Will it last till end of the day? After turning off inverter it goes to 12.8V:
Starting after the lunch:
After 1,5 hour it’s down quite a lot (went down from 12.7V to12.2V):
After 11 more minutes: 12.2V to 11.8V. Now the battery shows decreasing of percentage by a lot (42% to 27%), and only 11 minutes passed, so tracking this number is not very useful, however looking at voltage and comparing to the chart from above makes more sense.
Battery empty! 11.4 Volts. It even started beeping as BMS detected low voltage, so I quickly disconnected after this happened:
So, how many hours was I able to work (doing my usual job stuff)?
Let’s round it to 8 hours first day and 6 hours second day. So, 14h of work in total from a 100ah LiFePo4 battery connected to MacBook Pro and 24" monitor via inverter. In my opinion — not too good, I was expecting something more like a week.
It seems that I’ll need to do at least 2 more experiments:
- Use 12V plug for MacBook Pro instead of using it via inverter. Maybe it would have less energy loss, if no DC to AC conversion is needed. It would be interesting to compare the results!
2. I should try to optimise my laptop — it used as much electricity as it would have been connected to the wall socket, so it was not in any energy saving mode. Also, turning off some features, like turbo boost, may affect the results. I’ll need to do some research for what could be optimised and I will do another experiment with explanations soon.
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