Power issues with Celestron Powertanks, the ASiair and AM3

[SiD the Turtle]

I've got a brand new ASIair Plus, a ZWO AM3 mount hosting a Redcat 51 and a ZWO ASI2600MC-Duo camera. This is all working lovely when connected to the wall via a 12v power supply, but I'm having issues with Powertanks.

I have an old Celestron Powertank Lithium Pro which has seen a lot of abuse. When slewing, the power entirely cuts out and the battery dies. So I bought a brand new smaller version, the Powertank Lithium, but it has similar issues. Basically on slewing after a moment I hear a relay-like click in the mount, the same noise you hear when you first power it up. Then it decides it's only going to slew on one axis, and beeps if you try the other.

In the ASiair app it seems to occur when I breach 3 amps, but that's miles under what either battery is rated for. So, I think the ASiair and the mount are fine, as they'll work off of the wall socket. On battery if I turn off everything apart from the mount, it slews fine, so I think it's load. I'm going to try it on my HEQ5 mount via a Pegasus Powerbox to be sure, but anyone else had similar issues? How best to diagnose the cause? Are these batteries just rubbish, or am I missing something?

[Cosmic Geoff]

No idea, except that I stopped using my LiFePo Celestron powertank with my EQ-5 Synscan mount after it shut itself down a couple of times. Now I use a lead-acid car engine starter, which does not have that problem.

[Elp]

I assume you're running the power to either the air and feed the mount from that or the other way around (does the am3 have 12v out capability?).

I think I have the smaller version of your battery the Lithium LT but I also use Talentcells for the heavy lifting. I also don't have the am3 but use ioptron mounts primarily as an equivalent to yours. Neither are capable of powering as per my first paragraph, especially if I try to cool the camera to minus 10 Deg C, the peltier uses a lot of amps especially if using in warm ambient temperature as it has to work harder. The mount just won't have it and is usually the first to complain.

The airs input requirement I believe is 12v 5A so it'd be insufficient to power it via battery and have a voltage drop when everything is running, with mains the voltage is fairly consistent so less likely to run into an issue. Usually the battery has to be 11.5V or higher before something conks out I've found.

I would expect that particular camera also uses a lot of power. I've noticed when using my older 183 and newer 533 side by side the cooling for the latter runs much higher than the older camera so I suspect newer cameras may be less power efficient, this is also backed up by zwo stating specifically on more modern cameras that their cooling requires specific power whereas the older ones didn't have this stated as much.

My solution when using batteries is to use one for the mount and another for everything else. Dew heater bands also have their own supply. At home this isn't such an issue as you say an adaptor usually sorts it.

[ONIKKINEN]

Is your power tank this one?

I was never able to use it with an EQM-35 for the same reasons you are having trouble now. It just cuts off randomly when slewing at full power. At a reduced slew rate it could succeed, but even then not always. I think they put a far too strict battery management system in this thing that cuts off the instant more than 3A is drawn from it, even if for a split second when the slew starts. I think a battery/power station that is rated much higher, like 5A or 10A is necessary for reliable operation. I now have an Ecoflow River 300 which has 2x 3A 13.6v DC sockets and a single 10A 13.6v DC socket, which works well (but of course is much more expensive - no free lunch with batteries).

[SiD the Turtle]

Thanks all, I can't believe how daft I've been. @ONIKKINEN is correct, that's my old tank, and my new one is its baby brother. Both are rated at THREE amps, not FIVE, only the even larger version will do five. I'm simply underpowered, nothing more nefarious.

When the whole system is going (tracking, one dew heater, camera capturing with cooler running, anti-dew on the camera on, guide camera on) it's using about 2.5A. When using GOTO, it peaks at about 4.5A, way above what the batteries can do. Even if I turn down the slew speed it seems to take the same amperage, so no luck there. I guess this matches the AM3 documentation, which states it needs 1.7A during GOTO.

I put together this setup as a travel scope, and by travel I mean small enough and light enough to go in airline carry-on, so a car battery or proper caravan-spec lithium battery is out of the question. However, all is not lost, as @ONIKKINEN suggested, I'm going to run the mount off the smaller battery directly, everything else off the larger one via the ASiair and spread the load. Plus smaller batteries are easier to spread across backpacks for the aforementioned travel, rather than returning this battery and scaling up to a monster one.

 

9 hours ago, Elp said:

I assume you're running the power to either the air and feed the mount from that or the other way around (does the am3 have 12v out capability?).

For reference, the AM3 does not have the separate 12v out option.

Edited April 8 by SiD the Turtle

[Carbon Brush]

A bit late but the answer comes if you delve into the usage details (not just headline information) on the Celestron web site.

The key phrase....The PowerTank Lithium LT and PowerTank Lithium models have a circuit breaker that will shut the battery off if the power draw exceeds three amps or 36 watts.

Note they do not specify an overload/time characteristic. so you have to assume instant shut off.

If you run a lead acid battery, it may have a 10A or larger fuse that that a time/current lag.

In other words an off balance mount, or extra dew heaters, or inrush from a mount computer/camera are more likely to trip a lithium power bank.

This is a good start page.

https://www.celestron.com/blogs/knowledgebase/the-ultimate-telescope-battery-guide-getting-to-know-celestron-powertank-and-powertank-lithium

HTH, David.

 

[SiD the Turtle]

Thanks @Carbon Brush that's good to note and tracks with my findings. You go over 3A, it just turns itself off instantly.

[Elp]

Try removing the dew heater, I've found these are very power hungry especially if you're running them off the air.

When I tested with my in line power meter with my hem15 I found the peltier of the camera alone pulls around 1.5A but that was when testing indoors, the air itself hardly draws anything, mount when doing goto in both Dec and Ra is around 1-2A and the hem is slightly more power efficient than the am3.

When testing a different rig I've been putting together even a 12V 5A mains wasn't enough, I needed a 10A adaptor so the issue may be a combination of voltage drop and amp draw.

[Carbon Brush]

A note on dew heaters.

If you have a heater that takes say 1A, and run the controller on 50%, it may appear on a meter to take 0.5A. But that is because the meter displays an average.
The reality is that the heater is taking 1A and being turned on/off with a 50% duty cycle.

In this case the full 1A is 'seen' by the lithium pack protection and you get a trip when the draw appears to be below the threshold.
If you have a bench PSU, it may cope, or it may droop causing mount (power failure) trip. It all depends on the PSU construction and dew control timing.

If you have a lead acid battery, the old fashioned wire fuse in general handles the high current on/off without problem.

HTH, David.

[SiD the Turtle]

Thanks @Elp, @Carbon Brush. Indeed if I turn off the dew heater the draw appears to max at about 2.1A when slewing. I guess I could turn off the dew heater, GOTO, do all the usual setting up of tracking etc, then turn on the heater. But as if you suggest, the draw is still high on the dew heater, I might be dancing a little close to the edge. Still, gives me options regardless.

Interesting how even the mains link might cause me an issue if it breaches 5A. I have a relatively cheap Lynx Astro 12v adaptor that delivers 5A that I'm using indoors for testing. I have a ludicrously expensive Pegasus Astro adaptor in a dribox in the garden, and now I know why it was so expensive: it can support 10A. Probably more expensive than it needed to be, but it's been as solid as a rock for years.

[Elp]

2 minutes ago, SiD the Turtle said:

Pegasus Astro adaptor

Although it's not a Pegasus product this is the one I also bought to sort out a power problem I had. The Lynx again is not a Lynx product but that is the one I use if using a single rig setup, but for the new rig I'm putting together it's inadequate whereas the Pegasus one works, so for my needs I suspected I needed more amps, but I think the 10A is higher than the input capacity of the air which is 5A only.

[SiD the Turtle]

Oooh good shout. I don't know how good the regulation is on the Air, but I don't want to cook it.

[Elp]

I wouldn't risk it, my new rig goes through a 12V distribution box probably similar to a Pegasus Power box so those amps are shared.

[Carbon Brush]

Not sure if I'm misunderstanding something in the previous couple of posts. But here goes.

The important thing is to have a power suppy that delivers 12V at more amps than your combined loads.
The individual items look after themselves for current.

A non astro example. On cold morning, your car start motor may demand 400-500 amps from the battery.
When parked with headlights on, the bulbs combined may demand 20 amps from the battery.
When you turn on an interior light, it may draw 0.5 amps from the battery.
Everything looks after itself, regardless of the very high current capability of the battery.

Bottom line. If you buy a 12V 30A power supply to run a small mount, you won't damage anything.
It is the 12V that is the important number.

HTH, David.

[SiD the Turtle]

Thanks again @Elp, @Carbon Brush, this is why I love the astro community, you learn so much and people are happy to share their own knowledge. This is the stuff that's not in the manual!

So electrics are not my speciality so happy to be wrong here, but I guess the concern is if there's any chance you could draw more than the system allows. Take the Celestrons: you pull more than 3A, they shut down for safety. The ASiair can take in 5A max, what if the downstream components ask for 6A and your PSU can provide 6A? Does it cut off, does it try to deliver 6A? Does it cook something on the board? I know the Pegasus Powerboxes are built to be fairly idiotproof to prevent burning out devices or the powerbox itself. Is there a risk here that the Air doesn't?

[SiD the Turtle]

Just to add if anyone finds this post in future, a few points on the guide at High Point Scientific:

Quote

If you have any equipment that requires 12V DC power that you want to run off the ASIAIR’s DC out ports, connect these cables next.
Note: These are not intended to run a mount. Connect your mount to a dedicated power supply or separate power port if your supply/ battery supports this.

...

The longer version is this - the per channel current limit for the ASIAIR is too low for most all the popular 25 lbs and up payload capacity EQ mounts. Additionally you can’t get more power out of the device than you put in, which is an easy calculation in this case since the input and output voltage of the ASIAIR is the same - so we can just look at the Amperage. A popular ultra-portable EQ mount needs 2A, which means that if you add a cooled camera at 3A you’ve now maxed out the 5A power supply with nothing left over for the ASIAIR (or any USB devices connected). Now if you were going to run just an ultra-portable mount and then use the ASIAIR with a DLSR, you could be within the limits of the ASIAIR’s output.

Quote

ZWO has also stated that if you are connecting a power supply that is capable of more than 6A of current, that a 5A fuse should be placed between the supply and the ASIAIR - ergo there is no benefit to purchasing/ using a more powerful supply, only more complication.

 

[Elp]

I'd like the add, the plus is more funny about this than the mini, even with mains power the plus throws a fuss powering my mount and cooled camera whereas the mini just carries on with no hassle. If using batteries it is usually the case the mount needs its own power though with an azgti I can use batteries and power the air then the mount through it.

Edited April 9 by Elp