Before you buy a Power Bank from Talent Cell or Others Please Read This

[curtisca17]

10 hours ago, AstroKeith said:

I believe a so called boost converter will allow you to get the stated capacity out a lot of the time.

Advertising gives a capacity which is either a) available from a lower regulated voltage output, ie 5V USB, or b) unregulated 12V output allowed to drop down to 10V (or even less). Neither of these is right for most astronomy set ups. So using a boost converter allows you to get a useable voltage right up to the point where the pack shuts down at say 10V. You will lose about 5% with a good converter, but in case a) that will already be factored in.

I've started to use USB C to 5.5/2.1MM converters that have a PD trigger circuit in them. See below. With a power pack with PD or equivalent outputs I'm getting the rated capacity at a perfect 12V. 

 

One cannot defy the laws of physics.  If the power bank is not designed to output 12V then, while a boost converter can raise the voltage to 12V, it cannot fill in the lost capacity due to the need to boost the voltage.  I am not talking about the efficiency of the boost converter which, as you say, is typically 95%.  I am talking about the total energy (this is what we really use) in the power bank.  It may have 72Wh at a lower voltage but that means it will not have 72Wh at 12V.   That is precisely what the voltage versus capacity curves I measured and included in the video show.   Otherwise we have invented a limitless energy source.  The boost converter raises the voltage but at the cost of some of that 72Wh, not just the efficiency loss.  

So, yes a boost converter will get you 12V but the output will shut down before you have gotten the rated capacity.

[GTom]

I don't buy a power bank, buying 12V LiFePO4 packs, got a Miady 7.2Ah working perfectly fine, paid 40 quid on Amazon last year. The jury is out if I just buy two more of the same type or try to find a 150-160Wh unit that is airline-compatible. LiFePO4 provides remarkably stable voltage between 10 and 90% charge, compatible with all astro-junk we're using without adding any additional reg circuits.

Edited August 1, 2023 by GTom

[adyj1]

9 hours ago, Shimrod said:

 

 

Could either of you share a link for these? I also seem to struggle to find my power cables but have a gazillion USB cables lying around! I think it would be handy to have a couple of these in my cables box for emergencies.

I bought these (in 5.5 / 2.1 guise) ;

https://www.ebay.co.uk/itm/175828428910

Can't say for sure they're any good, but cheap as chips with free postage and reasonable-for-China delivery time... 

Edited August 1, 2023 by adyj1
Typo

[adyj1]

6 minutes ago, GTom said:

I don't buy a power bank, buying 12V LiFePO4 packs, got a Miady 7.2Ah working perfectly fine, paid 40 quid on Amazon last year. The jury is out if I just buy two more of the same type or try to find a 150-160Wh unit that is airline-compatible. LiFePO4 provides remarkably stable voltage between 10 and 90% charge, compatible with all astro-junk we're using without adding any additional reg circuits.

I'm just looking for what to take on a trip to the USA in October (annoyingly a week After the eclipse) , so I'll have a look at these - thanks. 

[GTom]

17 minutes ago, adyj1 said:

I'm just looking for what to take on a trip to the USA in October (annoyingly a week After the eclipse) , so I'll have a look at these - thanks. 

Email the specific airlines and airports you are planning to use and print the outcome. BTW you'll most likely get these cheaper in the US, if you can get it shipped to where you are staying can just order from the American amazon/ebay.
Make sure what you are buying has all kind of CE, FCC, whatever labels and terminals are sealed.

One strong argument though for the bigger Celestron powertank is that it maxes out the allowed capacity, close to 160Wh (hopefully real...). Can't find many other 12-13Ah (150Wh) LiFePO4 units.

[AstroKeith]

4 hours ago, curtisca17 said:

One cannot defy the laws of physics.  If the power bank is not designed to output 12V then, while a boost converter can raise the voltage to 12V, it cannot fill in the lost capacity due to the need to boost the voltage.  I am not talking about the efficiency of the boost converter which, as you say, is typically 95%.  I am talking about the total energy (this is what we really use) in the power bank.  It may have 72Wh at a lower voltage but that means it will not have 72Wh at 12V.   That is precisely what the voltage versus capacity curves I measured and included in the video show.   Otherwise we have invented a limitless energy source.  The boost converter raises the voltage but at the cost of some of that 72Wh, not just the efficiency loss.  

So, yes a boost converter will get you 12V but the output will shut down before you have gotten the rated capacity.

I'm sorry, but we dont agree. At all.

A pack of 72Wh capacity is a measure of energy stored, regardless of voltage. It is the capacity available when drawing a current until the pack output voltage drops to the stated minimum, usually 10V. The product of that current, voltage and time gives Wh.

Now consider using a 'boost' converter with steady 12V output. Observe the current and voltage at the input to the converter while running the pack to minimum. You will measure the same 72Wh. The output will be about 72Wh *0.95. But, the time to minimum will be less, since to maintain the regulated 12V output,  the converter will have drawn more current. Hence no infinite energy source. No gain has been made.

The trade off is using unregulated pack output, the voltage drops steadily until the powered equipment fails to operate correctly, typically 11V. Or draw a slightly higher current through a converter but do so until the pack voltage drops to 10V.

Indeed the use of a converter is about the only way to extract the rated capacity before the pack shuts down, unless your equipment is happy to run at 10V. This is demonstrated by the specifications for many power banks applying to the USB sockets only. The pack designers can extract all the capacity down to shut off, if they regulate it to 5V.

I have a new power bank rated at 86Wh. From the unregulated 12V socket I can get about 70Wh before the volts drop to 10.5 and my drive complains. If I use the 12V converter output (USB C PD) I get almost 90Wh.

[adyj1]

7 hours ago, GTom said:

Can't find many other 12-13Ah (150Wh) LiFePO4 units

I've seen these - look any good? 

Ultramax NP12-12 / LI12-12 12v 12Ah LiFePO4 LITHIUM Battery https://amzn.eu/d/j9lCYSo

[fireballxl5]

14 hours ago, GTom said:

Can't find many other 12-13Ah (150Wh) LiFePO4 units.

 

They fall outside your range so don't maximise the allowance or exceed it, but I've been using the 7Ah and 16Ah models of this Tracer battery for 5+ years now.  They've given excellent performance with a range of astro gear. I've also taken the 7Ah unit on flights a number of times without issue. When I bought the 7Ah airline allowance was only 100Wh.

https://tracerpower.com/products/batteries/tracer-12v-16ah-lifepo4-battery-pack/

Edited August 2, 2023 by fireballxl5
Corrected quote and added context

[AstroKeith]

+1 for the Tracer batteries, but they are expensive.

I have added these https://www.amazon.co.uk/gp/product/B08JV8MPHK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 to my kit. I now have 4 of them.

Only about 8Ah but with some useful connections. I use the USB C PD output to supply a regulated 12V, and the USB A to supply 5V equipment.

[GTom]

5 hours ago, adyj1 said:

I've seen these - look any good? 

Ultramax NP12-12 / LI12-12 12v 12Ah LiFePO4 LITHIUM Battery https://amzn.eu/d/j9lCYSo

That one looks good! For US-flights you might need American FCC marking on it because of the BMS chip.

[adyj1]

4 hours ago, GTom said:

That one looks good! For US-flights you might need American FCC marking on it because of the BMS chip.

BA allow up to 150Wh , but I have found out I'll be going with Virgin and they have a 100Wh restriction so these are now no good for me 😞

 

[Carbon Brush]

Another 'before you buy" comment.

Take a look at supporting approvals and safety documentation.

Is there any offered by the battery manufacturer?

With Tracer you have access to all the approval and test documents.
Very handy for settling arguments with check in staff.

[EarthLife]

On 01/08/2023 at 03:15, curtisca17 said:

Yes, one can put a band aid on a bad design to get it working, but there is no free lunch.  A boost converter will give the voltage needed but will not be able to do it for the rated capacity.  So, for instance, you are paying for 72Wh at 12V but only getting, say 55Wh.  I don't consider that fair advertising. 

I never said it was a good solution

Just an attempt to make something of an already unsuitable situation really. If nothing else it helps teach them a 'little' about electronics.

[fireballxl5]

Just wondering if there are now other/better options available.  I'm travelling to the see the solar eclipse in April and I'd like to have a 12V supply.  I have a Tracer 7Ah LiFePO4 but would need to take a bulky charger.  Is there a similar alternative that can be charged using a regular USB 5V supply?

[Elp]

I don't think one that charges via 5V usb will be powerful enough to run a rig. Another option would be to try and buy or rent one whilst you're there.

[Carbon Brush]

@fireballxl5 Why not ask Tracer about options for the charger? Though the 4A standard unit isn't that big or heavy.

Using a shorter mains lead (you need a US plug of course) loses some bulk and weight.

Measure the off load voltage of your standard charger and look for something with the correct voltage and lower current rating.
Provided it is a decent design, it will run in current limit without cooking or failing. You can check this out before leaving home.

There is nothing wrong with charging at lower current for longer.
It is just that Li is suitable for fast charge and most people want this!

A lightweight 5V to 14V(?) boost regulator is another possibility.
Again beware of the £1.99 offerings and check before leaving home.

HTH, David.

[adyj1]

11 hours ago, fireballxl5 said:

Tracer 7Ah LiFePO4

Whilst I'm normally in the same way of thinking as @Carbon Brush in trying to find 'good enough' alternatives, there's a lot written about charging LifePo4 correctly or at the very least you will reduce battery life. For something as expensive as this, I'd be looking at using a charger specifically for LifePo4, and take a hit on the extra bulk.

[Carbon Brush]

Thanks @adyj1.

The biggest 'wrongs' on any lithium charging are to charge to a higher voltage on each cell than specified, or to continue a charge current after charging is complete.
See the various online clips of chinese ebikes and the like bursting into flame. Charging to overvoltage makes them into very good firelighters🔥

The argument that you have to charge in a short (few hours) for best life, rather than take your time, is still very much unsettled.
I have used this cell (chemistry) type in an application where charging is at the whim of the weather - solar and wind.
Access to the equipment for battery swap is extremely expensive (around £20K now) so I had to be confident of battery longevity.

I think (fairly confident) that the pack used by the OP will have a good internal BMS (battery management system) and the charger is fixed voltage.
If this is correct, then a charger offering the same voltage, but lower current delivery will not have any adverse effect.
That is thinking about a small plug top or desktop power supply. Assuming the new charger is happy running in current limit for hours. Some are not!
The test is to put an overload (car headlamp, brake light, etc) on the PSU output and watch.
If the PSU struggles with a dim lamp, but desn't seriously overheat, you are OK.
Some supplies overheat. Some shut down on overload and retry at intervals. Some require a mains on/off cycle to reset. Obviously all these are unsuitable.
If you try a USB boost you need to know if the USB source is the power limit, or the PSU is the limit. Another can of worms to open!

At the end of the day it is about understanding the original equipment and the replacement/additional parts you are looking to add.
Oh yes - and measuring real world volts/amps. Not relying on the product label🤔
If you have the skill set to evaluate alternatives, fine. If you don't, stick to the original.

But is the original charger that bulky?

HTH, David.

[fireballxl5]

10 hours ago, Carbon Brush said:

Using a shorter mains lead (you need a US plug of course) loses some bulk and weight.

Yes,  I should try this.

I just wanted to check for new options.  I need to keep astro gear to a minimum but want to take some decent kit at the same time lol. 

[adyj1]

6 hours ago, Carbon Brush said:

If you have the skill set to evaluate alternatives, fine.

You have the jump on me with that, for sure 😉. For one thing, I forgot the BMS was in the battery not the charger... 

I will always bow to real-world proven experience, and you have clearly explained the reasons for your advice. Thank you 👍