Modems on GL-AR750S

We have a number of GL-AR750S routers that are running USB power banks for an event timing project. We have tried a couple of modems and both significant increase the current drain (like +0.5amp and more). ZTE hostless modem on tethering and a Quectel modem.

Would anyone know if these modems from Teltonika would work?

Just wondering if using CATM1 the current drain can be reduced.

Maybe not. The modem always use power. 0.5 is not too much.

You can use smartphone USB tethering? When smartphone is fully charged, it consumes little power.

Odd how people respond to tell me that my question is irrelevant. Really need to stop posting replies if you can’t answer the question.

We are powering this device over 24hrs. Battery banks over 20,000mah are not common and difficult to ship. At the moment the device is only lasting 14hrs.

The Teltonika modems have a max current drain less than half of the modems I’ve tested hence the question.

And we are deploying a few of these in to remote locations that are not staffed… so connecting up a mobile phone really is not a serious option.

Max power consumption on that modem is still >0.5a (0.72A max).

I’m not an expert on cell modems, but I would assume power draw is a function of how much transmit power you have to use based on the location where you are. It seems plausible that if you’re moving to a band with better coverage you might reduce your power draw, but again, not really my wheelhouse.

If it were me (it’s not) I think I would try to upgrade battery packs first, looking at the Wh rating rather than the mAh rating. I have two “20,000mAh” batteries, one which is 97Wh and the other of which is 84Wh. :person_shrugging:. The real cutoff for shipping and availability is the 100Wh limit for flying on airplanes, so it might be worth also looking into whether the banks you’re using are close to that.

I don’t think anyone here is suggesting your question is irrelevant, but I’m also not sure you’re going to find the answers you need outside of a forum specializing in cell stuff. Your OP didn’t clearly indicate you were powering these from batteries (missing a word by power bank - I misread and thought the AR750 was powering something not being powered by something), which is kind of a critical detail in this situation - otherwise, as @alzhao notes, the extra half an amp isn’t a big deal.

Best of luck in your search. I personally would be interested to hear how it goes.

Thanks for your considered thoughts. I guess 1/2 amp is a big deal in this situation, and the difference between operating for 14hrs and 30hrs. But thanks for your reply…

And yes current consumption does go up considerbly with poor network coverage.
Just trying some tests with switching off Wifi on the router and if forcing the modems to use only 2G will make a difference.

Possible. I’m not sure if you have one of these or know about them, but a high quality USB tester (I have this one) can be useful in determining what is affecting your power draw when you turn things on and off.

More broadly in thinking about things after my first cup of coffee, what you’re trying to do is going to be very challenging. Assume you can get a battery that is close to 100 Wh for the project. After switching losses, etc, you probably only have 90 Wh to work with (discounting a bunch of factors like temperature that can substantially reduce your efficiency). If you need this to last 30 hours, you’re talking about an overall max power budget of 3W, which is quite challenging. You’re noting that the modems themselves are drawing 2.5 of that, which doesn’t leave a lot for anything else (and this is all with zero margin for error). I would probably want to be under 2.5W total if I were doing this for a real production design and 30 hours was critical.

Again, not my circus, but the most straightforward solution to me given those constraints would seem to be using two battery battery backs - one to power the external modem and one to power the router. Alternatively, some battery packs will let you both “charge” and discharge at the same time, meaning you could chain multiple banks together to increase your overall power budget.

A lot of the design targets for power in this area are really about heat dissipation, not about energy drain.

Anyway, like I said I’d be interested to know what you come up with.

Feel a bit thick… can’t believe I didn’t think of the daisy chain idea as we are using pass through batteries. Will see if can get the current drain as low as I can then look at daisy chaining another battery on.

FYI we are charging the batteries using PoE and poe / 5v splitter, where we have power.

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