Portable mount battery

[adiastro.photo]

I am getting more confused as I read reviews and forums, therefore I thought it'll be best to just ask the experts here: :help:
How do I power my goto mount with portability in mind?

Portability is a key requirement
I'd want to be able to bring the entire dso imaging kit with me when I travel by land or air. Therefore those bulky gel deep cycle battery won't work.

Power

The battery only needs to power the ioptron cem mount. I haven't bought the mount yet but am thinking hard about the new cem26.
If it can power dew heater then it's a nice to have.
It needs to be able to survive a minimum 4 hours imaging session, ideally 6.


Form factor & safety

As compact as possible, ideally approx the size of a mobile power bank
Not weighing more than 800g
Safe for air travel, therefore maximum 100Wh


Here are 3 options that I evaluated:
Option 1: Celestron powertank lithium LT
https://www.celestron.com/products/powertank-lithium-lt

Pros:
+ Claim to be designed specifically for telescope mounts
+ Claim to have stable 12v output
+ 73.3Wh so this is OK for air travel

Cons:
- Expensive
- Mixed reviews
- 12V output is only 3A, whereas ioptron mount specs says it needs 5A, so not sure if this will work
- Bit bulkier than the other 2 options
- Practically impossible to find stock anywhere right now


Option 2: Talentcell
YB1208300-USB: https://talentcell.com/lithium-ion-battery/12v/yb12011000-usb.html

Pros:
+ Seem to have good reviews known for powering telescope mounts
+ Just under 100Wh, which is perfect for air travel

Cons:
- There's a mixed review saying that voltage isn't stable and tend to drop below 12v
- Specs says output is a range: 9V-12.6V and maximum of 6A
- Not many sellers in Australia and they can jack up price. Last I checked this is around $190 mark

Option 3: Jump starter like this one
https://www.amazon.com.au/GOOLOO-18000mAh-Portable-Starter-Booster/dp/B0748D8KT6

Pros:
+ Cheaper compared to the other two options
+ Plenty in stock
+ Covers wide range of function, including jump starting a car and as a flashlight

Cons:
- Hard to find detailed information on 12v stability and drain
- No information on mAh, therefore can't work out how long a full charge would last
- I don't know how to calculate the wattage so not sure if this is allowed in airplanes


Keen to know what your thoughts on this are.

[Merlin66]

Why not consider a 20Ah gel cell golf buggy/ mobility scooter battery?
With a good triple stage charger they last for years (Mine are now 13 years old (!!!!)) and still good to go.

[AdamJL]

OP mentioned airline compatibility and portability as a must. a Gel cell also weighs way too much compared to modern lithium tech.

@OP, in that list I'd choose the first one as it's apparently regulated 12V DC but as you mention, the amperage could be an issue.
The 5Ah is usually only when slewing for many mounts. You can also move it manually :)
My EQ6-R draws 1Ah or thereabouts when not slewing.

[Rerouter]

They are rarer these days, but look into external laptop batteries, e.g. BP160 and the various clones, the charge balancer / maintenance in these units is surprisingly well built, my one is still working 6 years after purchase, I will note at the 5 year mark, 2 of the cells failed shorted due to being flat for too long (9 months) but even with this, it still outputs 12V without issue. just loosing some capacity (all batteries are a series string, it has a built in buck converter on the output),

Ignore any claim of mAh, look at the watt hours and divide by 12, that will give you your expected 12V Amp hours.

[SteveInNZ]

I tend to measure stuff so that I know what I'm going to get.
My CEM25 draws 0.4A while tracking and a max of 0.8A slewing both axis. I bought this mount specifically for international travel and have taken it to the US (from New Zealand) a couple of times. My strategy is to take a Lithium battery pack in carry-on and buy a gel starter pack from KMart when we get there. They're cheap over there and then we donate it to Goodwill when we're done.
That way, I know that as soon as we land, I have enough power with me to image with a DSLR for an evening and don't have to rush to find a KMart. Once I have the starter pack, I have enough power to run a cooled camera and dew strips or to do multiple nights without worrying about recharging.

My Li power pack is labelled as 4.5Ah @ 12V but when I burn tested it, it would last just over 5 hours @ 0.4A. It was a few years old by that stage.



The 5A requirement from iOptron is for a mains power supply. Power pack manufacturers can be quite generous with their specs and while a 2A supply for example, may supply 2A at room temperature for a short time, it may not behave out in the desert or in the cold or with sudden current demands. As power problems are difficult to diagnose, it's prudent for a company like iOptron to specify an over-rated supply as the cost difference is small but the implication is large.


Steve

[Zuts]

I have one of these and it works great, it is also very light but rather expensive. I have currently had it for 3 years.

https://www.batteriesdirect.com.au/shop/product/24486/v-lfp-12-15.html

Lithium Iron Phosphate chemistry, LiFePO4
180 Wh/20hr
12 Volt 15Ah/20hr
2 kg

[adiastro.photo]

Thanks Steve, I have the exact thought process, that's why I choose the CEM26 over the CEM40. Good idea to buy a battery in destination country as you suggested. :thumbsup:
Now, what I am still not fully understand is CEM25 tech specs (https://www.ioptron.com/product-p/7100e.htm) mentions 12V DC(9 ~ 15V), 1.5Amp as the power requirement. Whereas CEM40 (https://www.ioptron.com/product-p/7420.htm)and CEM26 (https://www.ioptron.com/product-p/c261b1.htm) specs both just say 12V DC, 5A. Although they actually say it only draws less than 1A when slewing. So like you said, if iOptron specifies 5A to make it easier for them on paper then I suppose in theory using a 3A power supply shouldn't be an issue.
Although I'm not sure if say the voltage drops to 10V, will the mount be damaged. Seriously I find it hard to believe that an electronic equipment manufacturer doesn't account for input voltage tolerance, but who knows.


Thanks @AdamJL, yes, portability is key. Airlines will only allow batteries up to 100Wh to be carried without special permit.
Biggest problem with Celestron is finding stock in Australia.



Brilliant idea.
As you said, it's hard to find these days, but I wonder how a laptop external battery differs from those laptop charger powerbanks like this one (https://www.auspowerbanks.com.au/product/asus-87w-pd-laptop-power-bank/)? Internally, aren't they both just a series of lithium cells?

[DeWynter]

They are using the same 18650 Li-ion batteries (as well as Tesla cars).

[mura_gadi]

Hello,

Once you go over $250, its probably worthwhile getting a generator. If you like to go camping then it is almost certainly worth it.

Little $250 generator, 240vpower point plug, about 70db at 5m from memory. A nice extension cord and place it the other side of the car, be next to nothing.

8hour run time on a 2.1litre tank.

No idea about travel on a plane though, should be safer than a battery if its emptied.

Just make sure your up wind of the gen. when you set up for pollution and noise and should be good.

Steve
PS. This model was closer to 250 last I looked...now $320, but never have to worry about recharging batteries, just extra fuel and they won't go flat or loss charge quickly. If you run from a powerboard then home and darksite cables are the same, battery charger costs etc.
https://www.ebay.com.au/p/6031262717?iid=271531776044

[SteveInNZ]

It's not so much a case of making it easier for them on paper, it's simplifying the spec so that the user doesn't needlessly create a problem for themselves. In your example, if I were to select a 3A supply, I'd get one that I know can supply 3A continuously, over the temperature range, etc. But for all I know, you may pull a plug pack out of your bottom drawer that was originally used to power a desktop toy.

All electronic equipment is designed for a range of input voltages. If the manufacturer has specified 12V, they will have designed for 12V plus or minus some amount which varies depending on the application. IMHO, specifying an input of 12V (9-15V) is naive. Someone will try and power the mount from an inadequate 9V supply and have problems. If they used an inadequate 12V supply, it probably wouldn't drop below 9V and the user is happy.

Anyhow, the CEM25 (and I'd expect the CEM26) is well behaved if the supply drops out spec. The motor torque drops so it may start loosing steps if it's slewing. It makes a noise, but as it's a stepper motor, it does no harm. If the voltage continues to drop, it just turns off.


Steve.

[Rerouter]

Those powerbanks have a usbC output. You will need something extra to do all the handshaking to get it to request 12V out.

If you want to go that path. I would recommend a usbc decoy module and set the jumpers to say 20V. That handles the requesting so you get a fixed voltage out. And on its output use one of the cheap and easy switchmode buck converter modules based on an LM2596 to regulate back down to 12V at a few amps.

Stick those 2 in a small enclosure with a little soldering and now any usbc power bank can run all your gear. And that wont raise any issues at customs becuase its not powered.

Why i went this way is some of those modules can behave weirdly. So the buck convert will keep your stuff safe. E.g. some random power bank only supports 9 and 15V the module might request 15V and cause you some greif.