Battery model recommendation

The performance with and without a battery is about the same I’m at work right now but I look over your question and look at my batteries to verify what you’re asking about

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Got 2 Nitecore NL1832 from B&H photos, and DevTerm claims to have a battery life of ~10h (estimated by the applet, speed mode 1 in the gearbox (single core, up to 720Mhz)). They fit well in the case.

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I’ve bought those same batteries XTAR 18650 3500mAh 3.6V - 3.7V Li-Ion battery (protected) | and I have yet to see the power run out if I charge them in the DevTerm.

I also have bought a charger Keeppower L2 Plus - 2-Bay USB Li-Ion Charger with Display | and for some reason if I charge them in the charger the DevTerm only detects 50% capacity.

Since I’m a total noob maybe I bought the wrong charger?

Do those protected cells you linked actually fit comfortably in the DevTerm?

I ordered a pair of unprotected Samsung INR 18650-35E since I was afraid the extra size of the protection circuit may be too much to fit.

If you’re asking me: No: they do fit very tightly and it’s awkward to put the battery cover in and they are quite hard to get out, but they do fit and work fine.

But I can’t say they fit “comfortably”, so I had to answer “No” instead of “Yes” to your specific question.

Next time I would probably buy them without the knob at the + pole.

I wish I could use these, but way too long

Built-in charging port :heart_eyes:

I ended up purchasing two kinds of batteries before I received my Devterm A06. Although I wasn’t really sure of the risk, I bought unprotected batteries since it sounded like they’d fit better and would be ok as long as they were a reputable brand and I was careful in handling them.

Both pairs of these work fine for me and are of comparable size:

(currently sold out)

Both charge in the Devterm, and also in an external charger, although after testing both it seemed it was best to leave them in the Devterm and charge while I was using it. Though the external charger seems to work fine, I had a few times where it showed fully charged and then when the batteries were put in the Devterm it showed they were at least than full charge. Seems like the device may maintain some kind of memory of the battery and it could get confused if batteries are swapped out?

While they fit in the case fine, removing these (and I expect any batteries?) was difficult since there’s nothing to grab onto to get them out, and care is required. So I put some tape around the middle of them, and made a “tab” out of the excess tape so I have something to grab onto and pull them out. Though to be honest, I’ve left the Sanyo in for a week or so now, and just keep charging in the device when I’m using it, and disconnect when I’m done.

Doesn’t seem like it’s possible to charge batteries in the Devterm when the device is powered off?

For any future revision of the Devterm, it would be nice if a ribbon/string of some sort was added that could sit behind the batteries and allow for easy removal. But my tape trick works too. :wink:

Oh, and I get about 4-5 hours of battery life out of them. (Mostly compiling and testing things – not heavy emulator/game use yet except for testing, and not really any printing either though I have tested it too.) I tend to charge up near to full when I use it, and then next time disconnect and let the batteries drain until a little under 10% and then plug it in again. I’m not sure how low I can go, but I’m not convinced the device stays on or is usable past about 5%, so I start charging at 10% again just to be safe. And if you’re printing anything, I’d say make sure to have at least 50% battery or more as printing really sucks the power.

Running LG HG2s here as they are my preferred 18650 cell. Does the DevTerm only actually charge the battery while the system is powered on?

Sadly, it seems so, at least on my A06.

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Strange: My A-0604 charges fine while switched off. It’s my usual method of charging, in fact: I rarely have it plugged in while it’s switched on.

To double-check, I just plugged my partially-discharged DevTerm into my benchtop power supply: 2A power draw at 5.2V while powered off, which from prior experience will gradually drop to zero once the batteries are charged.


Does the yellow charging LED switch on? Maybe its just that it is of while charging when switched off…


It doesn’t. In fact, I’ve got that in my review notes: “no charging LED.” Turns out there is a charging LED, but it’s only on if you’re charging with the DevTerm switched on; if it’s switched off, there’s no LED but it charges anyway.



Ah! I was under the impression that because the light was off, that it was not charging, I will test this out and plug it in with it off on mine now. Thanks for the information!

I was under the same impression. I was also a bit over cautious about the batteries in general given previous discussions on the forums, and wasn’t sure it was wise to leave it plugged in, with batteries, especially if the light was off and it seemed like it wasn’t actually doing anything.

It’s a shame the light doesn’t come on, and then go off when the batteries are charged. I guess that’s another question – is it safe to leave the device charging when off? Will it properly stop charging the batteries when they are full? Or will it cause problems and potentially damage the device? (And same questions for both batteries that are protected, and batteries that are unprotected, as I’ve got the latter…)

I figured I’d err on the side of caution, but if I knew it was safe to charge when the Devterm is off, then it would be a useful thing.

It is absolutely safe, yes: there’s a battery management system with under- and over-voltage protection. That’s built in to the DevTerm, and is true whether you use protected or unprotected cells; the only time you need to worry about unprotected cells is if you take 'em out of the DevTerm for some reason.

Going back to my tests with the benchtop power supply, I can confirm that the batteries charge as you’d expect: 2A while empty, then gradually dropping as they reach full charge until the DevTerm stops charging automatically. At that point, the supply still reads a 0.001A power draw - but none of that’s going into the batteries, as far as I’m aware.

I’ve left mine plugged in overnight, same as my phone and laptop and all my other battery-powered devices: haven’t had a single problem.


I just received two Nitecore NL1832 batteries, labeled as 3200mAh, 3.7V, 11.8Wh. They are a tight fit, but they go in fully and I can close the battery door without problem.

I charged the batteries, plugged them into the DevTerm, booted it, and let it sit on the empty desktop with an SSH session displaying battery status every minute. 2.5 hours later it shut down with the final POWER_SUPPLY_CAPACITY=21.

Is this an expected power lifetime?

That feels a little low: during my own testing, with an A-0604 running at the default four-core 1GHz setting, I got three hours and 49 minutes of video playback from a pair of no-name “3,400mAh” cells.

Try letting the batteries charge in the DevTerm, rather than using an external charger.


Try letting the batteries charge in the DevTerm

Thanks, I will do that.

Could this be due to using re-wrapped cells that have inflated advertised capacity?

Do you mean mine, or PiNYC’s? Because mine are almost certainly rewrapped and may or may not be anywhere near their labelled capacity in reality, but I’m getting a longer runtime than PiNYC’s branded cells.

If you mean PiNYC’s cells, it’s possible they’re rewraps - Nitecore cells are among the most commonly counterfeited, so depending on where they got them the cells could be fake - but I’d wait to see the results after a full charge-discharge cycle in the DevTerm itself before worrying.