Fast charging

[TomJ]

Does anyone know whether the Astro will be USB PD compatible?  If it's Pump Express 4.0, which I hope it would be, then it should be, but I can't find owt from Planet confirming or denying...

[Daniel W]

The Gemini and Cosmo both uses the really old PumpExpress+ (essentially version 1.0), presumably because it's cheap. Until we either get further details from Planet or the Astro starts shipping, I guess they'll use the same old version with the Astro, so they can keep using the same type of wall chargers for the Astro as well.

The marketing says that the Astro will have up to 10W wireless charging, which may have forced them to use something newer. Then again, the power bricks for the Gemini and Cosmo can deliver 2A at 5V, without any particular handshake, and that equals 10W, so my guess is that wireless charging of the Astro won't use any particular fast charging at all, while charging via cable will use the same (up to) 1.67A at 9V = 15W PumpExpress+ as the previous devices.

[sobukus]

I have an Astro now, but cannot see it actually negotiating higher voltages even with the stock charger. I see 5 V and 1.8 A, from around 5 % on up to 50 % … in that range, I'd expect a swich to 12 V.

Can anyone confirm that the device uses higher voltages or currents? I tried in booted state and after switching of, checking with a USB C power monitor.

[sobukus]

The Gemini at least gets to 9 V with the Astro's charger, at around 80 %. The Astro draws 1.5 A at 5 V  around 66 % battery charge. Is this even a regression in the charging, or some tuning that doesn't apply fast charging for the first few cycles? Maybe just a setting that can be configured …

[Zarhan]

Can you check if there's a difference between left/right ports? On Cosmo the other port only supported basic charging, the other one supported faster charge.

How can you see the negotiated voltages? Do you have a voltmeter or can you see this directly from the phone?

[sobukus]

I got USB meters that you plug in between port and device to show voltage and current. I got both a USB-C one (DIGITUS DA-70612) and a plain USB-A one (KCX-017, modern version that can do between 4 and 30 V).

But you're right: I did mix up the ports, as it is the left one on the Gemini and the right one for the Astro (looking on the opened device, facing keyboard and display).

I see the Astro using 9 V and 1.2 A from its AC adapter. Seems like the Gemini there, far from 18 W, though. I am not that keen on max power, but am wondering about the options of having possible more efficient stages of DC to DC conversion when coming from a source like a car battery. But this might be nonsense considering that it's converted down to 4 V for the battery in the end, leaving only the issue of lowering the current on thin cables.

What is disappointing, though, but maybe not the Astro's fault: I only see 5 V 1.2 A on the output of a DC-DC module that claims 'MTK PE1.1/2.0' support, among others (QC 2.0, QC 3.0, FCP, ACP, SFCP). A Samsung Galaxy S5 phone gets 5 V 1.8 A out of this one. I wonder if I'd have more success with a device with USB PD support, as Mediatek PE 4.0 is implemented on top of that (?!).

Do we know what exact spec for 'fast charging' the Astro is supposed to support? There's such a multitude of them that I am just confused.

[Zarhan]

Well, some sort of fast charging is definitely going on, as it says that charging from 40% to full takes only 20 minutes. And the charger is actually noticeably warm.

[sobukus]

From 40% to full in 20 minutes? That's 60% of 4000 mAh battery, 2.4 Ah. Let's use the effective voltage of 3.7 V. That's 8.9 Wh of energy, transferred in 1/3 hour (20/60 minutes), this means the power arriving at the battery needs to be 8.9*3 = 27 W. The charger only claims to be able to deliver 18 W max. and there are losses in further conversion from 9 or 12 V down to the battery.

When 'full' means 80%, then we arrive at about 18 W being pumped into the battery … when the electronics in the Astro itself work with 98.7 % efficiency, this could be barely possible.

I installed the Wattz app from F-Droid to get a display of the power and current going into/out of the battery. Right now, at 65%, it only shows 3.1 W charging (matching what the USB power monitor device says, but also without this one in between). This should be much more. Strange. I wonder if there is some setting. Also: Wattz claims 2000 mAh at 65% … this does not look like 4000 mAh for a full charge.

[Zarhan]

From 40% to full in 20 minutes? That's 60% of 4000 mAh battery, 2.4 Ah. Let's use the effective voltage of 3.7 V. That's 8.9 Wh of energy, transferred in 1/3 hour (20/60 minutes), this means the power arriving at the battery needs to be 8.9*3 = 27 W. The charger only claims to be able to deliver 18 W max. and there are losses in further conversion from 9 or 12 V down to the battery.

When 'full' means 80%, then we arrive at about 18 W being pumped into the battery … when the electronics in the Astro itself work with 98.7 % efficiency, this could be barely possible.

I installed the Wattz app from F-Droid to get a display of the power and current going into/out of the battery. Right now, at 65%, it only shows 3.1 W charging (matching what the USB power monitor device says, but also without this one in between). This should be much more. Strange. I wonder if there is some setting. Also: Wattz claims 2000 mAh at 65% … this does not look like 4000 mAh for a full charge.

It might have been misleading minutes. I just plugged the charger in and it said that time to charge is 20 minutes...I didn't actually clock it.

With Wattz, right now, I'm at 91% charge and it says that there's 11Wh (2,7Ah) of energy. If the battery is 4Ah then something is wrong here. Of course, it might be that some portion of the battery is not really used (like it's with EVs), but that's still quite a bit of different.

If I try charging, I get -4,6W.

I'll let it drain overnight and check what the figures are when SoC gets lower and charging is attempted.

[Zarhan]

My battery had drained to 80% overnight (from 90%). First note: Looks like Astro is *much* less power-consuming than Cosmo.

Anyway, when I now plug in charger, Wattz shows 8 to 9W charging rate (via right port).

I'll let the phone discharge a bit more and see what happens.

Update: At 70%, the charge speed is 12W.

Update #2: At 60%, the charge speed is 14W.

So looks like the rate increases when SoC goes down.

[TomJ]

I'm assuming it's Pump Express Plus, given the relative youth of the SoC and the presence of wireless charging; I have seen this described as PD compatible, but want to understand whether a PD charger (or even a PD compatible version of QC one) would fast charge an Astro.

[Zarhan]

I'm assuming it's Pump Express Plus, given the relative youth of the SoC and the presence of wireless charging; I have seen this described as PD compatible, but want to understand whether a PD charger (or even a PD compatible version of QC one) would fast charge an Astro.

I plugged my wife's Samsung charger to Astro, and got 9,5W at 55%. Astro's own charger still got 14W. So it's at least some partial compatibility.

[sobukus]

I did another round of tests, below 50% charge. At first, no luck with anything above 5 V 1.4 A, even not seeing a difference between the two USB ports. I was not able to eek out more than 5 V (or 5.2 V, if one believes the monitors) even from the Planet AC adapter.

Then, I turned the Astro off and then connected it to power in various combinations of cables, meters, power sources. There, I got more luck. The negotiation of higher-voltage modes is really finicky. Sometimes it works, sometimes not. Powering with the Planet AC adapter, and with my USB-A monitor, I've seen 9.9 V 1.5 A once. With the USB-C one, I'm more likely to get around 9.6 V 1.5 A (numbers might just be a bit off in the monitors).

After having established a connection that does 9 V charging, I turned the Astro on and it was able to resume that mode after booting up, with Wattz showing 14 W going into the battery. So this seems to be the highest mode possible, but getting that depends on a bit of luck, really proper connection with cables and all intermediate sockets … and maybe even a software state that remembers that the connection was tricky before and hence disables the higher charging modes to be on the safe side? Switching off the device resets things each time power is disconnected, I think.


On my DC-DC USB charging module, which supposedly can do all the QC modes and MTK PE, the best I get is 8 W charging at 5 V. The Astro is just not able to negotiate something higher. I don't have other devices that would test this … only the Samsung Galaxy S5 phone which happily draws around 9 W, too. I have yet to test what the Astro does on a proper USB-C AC adapter with PD.

The Wattz app is handy … when I'm pressed on time I'll check if the Astro is in 'safe mode' again and power cycle it to get back to the quick charge negotiation. I wonder if someone can confirm that there is such a thing as a soft disabling of quick charging above 5 V 1.5 A  until next power-off. Maybe I just have a lottery with good/bad USB-C connector fit and wiring.

[Zarhan]

I'm just using Planet's provided charger and cable, nothing fancy.

With Cosmo's charger, I also got lower results in the 8W range.

Although, frankly, I'd *prefer* the very slowest, basic charging - that supposedly increases the lifetime of the battery. Unless I'm in a hurry, of course.  It seems that I get around 5W when I plug Astro to my laptop, but still around 9W when I plug the charger to the left port. So even the left port has *some* form of fast charging.