Battery Recomendations

[Elp]

1 hour ago, Carbon Brush said:

Simple tests. No rocket science.
Grab a few car bulbs and a multimeter. A few bits of wire and tools/materials to prepare & hold the kit.

Isn't it easier just fitting an in line voltmeter? Less than a tenner from Amazon, spliced and fitted DC female pigtails on either end, battery into meter, meter to mount/computer controller. Gives V/A/Wh etc live readings.

[CraigT82]

33 minutes ago, Elp said:

Isn't it easier just fitting an in line voltmeter? Less than a tenner from Amazon, spliced and fitted DC female pigtails on either end, battery into meter, meter to mount/computer controller. Gives V/A/Wh etc live readings.

This would have the bonus of being able to monitor the draw in real time. Helps with balancing (if you get a meter with a readout of at least 2 decimal places) 

[Elp]

9 minutes ago, CraigT82 said:

This would have the bonus of being able to monitor the draw in real time. Helps with balancing (if you get a meter with a readout of at least 2 decimal places) 

The cheap ones will only give an indication as I doubt they're very accurate, but it was enough for me to determine the power input I needed for a custom rig I've put together. The initial LiFePo4 batteries I bought (to DIY a power pack) dropped voltage too quick, but I think that's where the regulator above comes in, batteries won't work without a regulated supply.

[CraigT82]

OK did a bit more testing in my setup with the Anker 521.

I had AZ-EQ6, 533mc pro, ASIair, EAF, guide camera and two dew straps (40cm and 20cm) - all switched on and plugged into the Anker which was fully charged.

The mount itself plugged was into the Cigar socket, and then everything else plugged into the AC outlet on the Anker (power going through a Pegasus Astro 12v 10A mains brick to the ASIair and from there to the peripherals).

When the mount was just tracking, the total power draw (mount, camera etc etc) was 26 watts which would drain the 521 battery in a little under 5 hours, according to the display. 

With the mount slewing in both RA and Dec the power consumption jumped to 37 watts.

No low voltage warnings anywhere from mount or ASIair during tracking or slewing. 

Probably need to try this again when the battery is more discharged to see how that effects things but hopefully gives you some food for thought as to what power pack to go for - I believe - as others have said - the harmonic drive mount will draw more power but I’ve no idea how much. 

Edited September 25 by CraigT82

[AstroKeith]

I took a look at the Anker 521 specifications. I have a few Anker bits and they are all of good quality.

I was surprised to see that the USB C PD output does not support 12V, only 5,9,15 & 20V.

This immediately rules it out for me. 

They dont specify their inverter efficiency, but others have done some tests and indicate it to be perhaps 85%.

[Elp]

1 hour ago, AstroKeith said:

inverter efficiency

See my previous query, what if you use one that has 12v outs?

[CraigT82]

2 hours ago, Elp said:

See my previous query, what if you use one that has 12v outs?

Yeah that should be more efficient as there is no internal inverter taking the DC to AC and another external inverter taking it back to DC again for the kit. I think the Bluetti units seem to have a 12v dc output in addition to the cigar socket so they would be a good one to go for if you didn’t wish to use the cigar socket to the AC outlet. 

[AstroKeith]

3 hours ago, Elp said:

See my previous query, what if you use one that has 12v outs?

 

30 minutes ago, CraigT82 said:

Yeah that should be more efficient as there is no internal inverter taking the DC to AC and another external inverter taking it back to DC again for the kit. I think the Bluetti units seem to have a 12v dc output in addition to the cigar socket so they would be a good one to go for if you didn’t wish to use the cigar socket to the AC outlet. 

The dc to ac inverters are inherently less efficient, mainly I think because they are constrained to run at 50Hz. So as Craig says, plugging into the ac outlet on a power pack, and then using a dc power supply to get your 12V gives a double loss. But at least you get a stable output, but not for very long!

Considering the complexity and value of our astronomy gear, we really shouldn't be running it off raw battery voltage. So you either find a power pack with a regulated output, or add a dc-dc converter (refer to my earlier link). dc-dc converters can be 95% efficient as they run at 20kHz typically which makes losses easier to manage.

The problem with the 12V regulated outputs, is that they are 12V. Add a couple of metres of cable and the mount or camera etc will see around 11volts. Loads of threads on here and CN about problems this produces.

The advantage of an external dc-dc converter like I linked to is that you can choose a 13.8V version. Just about perfect.

BTW, all the built in capacity monitors, and the in-line sort you can buy are inaccurate especially when stepper motors are used in the mount. These monitors seriously underestimate the current being drawn as they dont sample the spikes.

[CraigT82]

Right so looping back to @groberts original question, I think my course of action in his shoes would be to get one of the larger battery packs (at least 500Wh I’d say) with two AC outlets, and I’d run the mount off one AC outlet and a power brick, and all the other kit off the other AC outlet and another power brick.

That way all your kit sees nice stable power and shouldn’t have any issues operating everything. 

Down side is using the battery DC-AC-DC is inefficient so will effectively reduce the overall capacity of the pack, hence going for one of the larger ones to begin with. 

You can also try it all out just using the 12v outlets from the pack and see how it all works in anger, if no issues then happy days and do away with the AC power bricks. 

I’m surprised no one using an AM5 portable imaging rig has chimed in yet, must be someone out there? Maybe posting the same Q on cloudy nights might generate more help? 

[iantaylor2uk]

I use two Jackery 240s, one for the mount (an RST-135) and the other for the ASI Air Pro and ZWO camera, and these still have more than 50% left after 4 hours. I only cool my ZWO cameras down to 0 C. If you cool to lower temperatures then that would obviously draw more power.

Edited September 26 by iantaylor2uk
typo

[Elp]

My last session I powered my AM3 with this, got 3 hours+ of data as I was dithering every 10 minutes so ran slightly longer. Everything else was powered by a separate battery. It's a 100Wh so gives you an idea, but as stated the mount was beeping all night due to "low voltage" (it ran perfectly fine).

 

https://www.amazon.co.uk/TalentCell-Rechargeable-11000mAh-20000mAh-Portable/dp/B06Y5G3C8Z/ref=mp_s_a_1_3?crid=2PHNQC1402IJP&dib=eyJ2IjoiMSJ9.vnF27gXR1njUqrh1OLT_K6_qSGizcglhHJ0ifW_tH_3gfbT-4SE6kxjXm45q8T7SqW3Jj_fIkrE0wUNNzA6fC3mFOs_pYNs55C2K2COgHN21dygt--uqITZERl1VBQSrsRXDsMGB6XF8yf_7lB5-F2uV_QLCpY1rrzM__VJoiT0_luVeHMrwwLO8VGJr9FbYOcQyfORJdCwnIFGWPdOMzA.iPbw_vAxu7ab1pjJOclt8Ws-L2LeS_T0MPQCb0U_pts&dib_tag=se&keywords=talentcell&qid=1727362286&sprefix=talentcell%2Caps%2C952&sr=8-3

 

[groberts]

Thanks everyone - now thinking of getting the Bluetti AC50B.  

https://bluettipower.co.uk/products/ac50b-portable-power-station?variant=45680765075622

Any comments please before I push the button?

Graham

 

[Elp]

12 hours ago, groberts said:

Any comments please before I push the button?

Probably the best in their range for capacity vs price. I find it a bit odd though that their smaller EB3A has 2 off 5.5mm DC out ports, which is missing on the higher model you're looking at. It should be back in stock this month (Oct).

[Jules Tohpipi]

On 24/09/2024 at 14:35, AstroKeith said:

If you need a good voltage, then consider a dc-dc converter. supplier link this will give you that 13.8V constant until the battery output shuts down.

Thanks for your wisdom on this thread. I'm already in possession of a dc-dc converter (near identical to the item in your link) that's intended for a battery project still yet to be started. However, I ordered one with 12V output (not 13.8V). Should I have ordered the 13.8V version instead? Planned use is with my AZ-GTi and 10" Goto Dob; however, an AM5N is on the future shopping list. Both mounts say 12V in the manuals. Would I be correct in understanding you're recommending 13.8V to compensate for voltage drop down the cables? 
 

Edit: I’ve read page 2 of the thread now and seems the answer is yes

Edited Tuesday at 22:23 by Jules Tohpipi

[groberts]

Sorry, maybe a stupid quesion, but looking at the AM5 the input socket says DC 12V ~3A, is a battery that supplies DC 12V and 10A okay to use?  

 

Edited Tuesday at 15:56 by groberts

[Cornelius Varley]

12 minutes ago, groberts said:

Sorry, maybe a stupid quesion, but looking at the AM5 the input socket says DC 12V ~3A, is a battery that supplies DC 12V and 10A okay to use?  

 

Perfectly safe. The mount requires a minimum of 12v/3a. A psu that produces a higher output or a high capacity battery is OK. The mount will only draw what it requires.

[groberts]

Another basic but possibly important question:

I'd certainly use the DC 12v 10A cigarette lighter connector to the mount but if I wanted to separately run a cable using 5.5mm 2.1mm plugs out of the battery - which is rated 10A e.g. like the Bluetti EB3A - either into the ASIair or dew straps which are recomended as 12V 5A, will that also be OK, or do I need to drop the amps to 5A + if so how?   

[symmetal]

The electrical resistance of the device being powered determines the current it will draw from a fixed voltage supply. As long as the supply is rated capable of supplying that current or more it will be fine. You can connect your dew straps, or anything else which requires a 12V supply, directly to a 12V car battery and they will only draw the current determined by their resistance, even though the car battery is capable of supplying 200 amps or more. 🙂

Ohms law states  I= V / R   (current  = voltage / resistance)

Alan

[Cornelius Varley]

24 minutes ago, groberts said:

Another basic but possibly important question:

I'd certainly use the DC 12v 10A cigarette lighter connector to the mount but if I wanted to separately run a cable using 5.5mm 2.1mm plugs out of the battery - which is rated 10A e.g. like the Bluetti EB3A - either into the ASIair or dew straps which are recomended as 12V 5A, will that also be OK, or do I need to drop the amps to 5A + if so how?   

No need to do that. If you use a psu you only need to ensure that it meets the minimum requirements ie a psu rated at 12v/5A will deliver 12volts at a maximum current of 5A. If the device draws 12v at 3A the psu won't mind but probably would if you try to draw 12v/10A. For a battery the devices will draw what power they need until the battery is flat or the voltage from the battery voltage falls below a useable level and they cease to operate. Mains power units are rated in Volts/Amps and batteries in capacity ie 75Ah.