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What are people's recommendations for a power tank to power my go-to scope ? 

Thanks.

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I've been using the same 20Ah gel cell batteries for over ten years. With a triple stage charger they seem to last forever.

These are the golf buggy/ mobility scooter type.

Highly recommended.

 

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I use Tracer LiFeP04 batteries which have better discharge characteristics than old style gel batteries. Lot smaller and lighter too. Downside is they are rather expensive to say the least. ?

I already have a couple bought for other purposes so cost wasn’t a factor but gel batteries are a tiny fraction of the price which would be a factor if I had to buy new batteries.

Edited by johninderby

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John,

With the limited number of recharge cycles.......it will be interesting to see if they are still viable in ten years time.

 

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At 1400+ charge cycles (discharge to 8.0v) don’t think it’s going to be a problem.

Edited by johninderby

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I'll be honest, hadn't considered normal sized rechargeable batteries (AA), as assumed they wouldn't have a large number of recharge cycles and also they wouldn't last long before needing a recharge ... was looking at mainly powertanks, but batteries may be an option.

 

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9 hours ago, Merlin66 said:

I've been using the same 20Ah gel cell batteries for over ten years. With a triple stage charger they seem to last forever.

These are the golf buggy/ mobility scooter type.

Highly recommended.

 

Sorry but I have to argue.

At work I have been using (and throwing away) lead acid gel cells for 40+ years in a wide range of equipment.

Regardless of how well you look after them, they degrade on a daily basis. There is a cumulative loss of capacity and increase in internal resistance that is a consequence of the construction.
I first learned this from a manufacturer of high quality cells and battery packs.

This is a temperature dependent factor. If you want the cells to last longer, keep them in the fridge until they are needed.

Any cell that is several years old will have suffered significant capacity loss.

It is just that if you only use a fraction of cell capacity in a session you don't notice the degradation.

As an example, our work burglar alarm has lead acid backup. In the annual test, the battery is swapped out if it is measured at 2/3 original capacity, or at 5 years, whichever comes first.
In practice, these batteries (stored and used at reasonable temperature and kept properly charged) are thrown out well before 5 years.

At work in new equipment design I no longer specify lead acid. NiMH/NiCd sometimes, but increasingly Lion.

At home, as my old battery packs in torches, scope kit or anything else require renewal I am tending towards lithium.

For astro work lithium gives far less performance fall off at freezing type temperatures.
Lithium has typically 3x the power to weight or power to volume ratio of lead acid. Less to carry into the field.

When you buy a lithium battery pack, it often has included circuits to prevent over charge, over discharge and charge at too high temperature.
This is going to ensure you have a product with long life.
My experience has been that the quoted cycle life is often exceeeded. Don't forget the cycle life is often quoted to 65% or 80% of original capacity. It depends on the manufacturer.
As battery does not suddenly stop working at 1000 cycles or whatever is quoted.
Further if you buy a pack tht has UN38 transport approval - like the Tracer packs in the UK - you are assured that you have a pack that has been subject very rigorous testing.
It is not going fail catastophically like some (or is that a lot) of the chinese imported stuff.
 

Hope this helps, David.

 

 

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I have no professional experience with rechargeable batteries but my other hobbies have given me a wide amateur experience with all types of rechargeables.

The significant power to weight ratio improvement of Lithium over Lead Acid is very apparent with power hungry pursuits like electric biking where lead acid batteries are now untenable, giving very limited range and/or weigh as much as the bike itself.

In model aircraft and drones, lead acid is not even an option because of the weight, and lithium is the only electric way.

Lithium permits thousands of discharge/recharge cycles before degradation, whilst lead/acid is "only" hundreds.  Coupled to that, even in "deep cycle" varieties, lead acid depends on not being more than half discharged each cycle, (so about half the stated amp/hour capacity) to last the longest.  It is still the favoured choice for cars because the intial heavy draw of engine starting is then immediately followed by constant powerful recharge, keeping them fully topped up in normal use.

The main downside of lithium is their requirement for very carefully managed recharging, or they can explode.  In the majority of consumer applications this is automatically taken care of by built-in "battery management systems" or "BMS" for short. These make charging a safe plug in and forget process, automatically monitoring individual cell voltages and controlling the amps applied till the maximum safe voltage is reached.

Lead Acid charging is far less demanding (and sophisticated).

Having said all of that, my (admittedly more limited) experience of powering telescopes has given me the impression that the amp/hour power requirements are much more limited, witness the fact that many scopes are supplied with disposable battery cell holders.  My Meade ETX125 for example has a built-in holder for eight 1.5v AA batteries.  Compared to this, even the smallest and cheapest 12v lead acid battery has a much greater runtime before needing a recharge.

I myself would probably have bought a Skywatcher or Celestron powertank, (probably the 17ah version), but I already had a pair of 14ah SLA ("sealed Lead Acid") batteries which are now about 4 years old, having been used initially to power a canoe's miniature electric outboard motor.  They are still in very usable condition, lasting for several nights before needing a recharge.

I fitted them, connected in parallel,  into a watertight "lock and fresh" food container with a fuse and a ready-made two way car cigarrete lighter socket and two USB sockets and a numeric LED voltmeter to let me know when it needs recharging.  (I'll take a photo of it and add it to this thread).

That gives me a nominal capacity of 28 amp/hour, but a useable capacity of 14 amp/hour  (to half discharge), compared to the larger powertank's capacity of about 9 amp/hour (half of 17).

It hasn't got a red light or a white searchlight (!), and no radio either (in the dark, at night ??), but it works really well for me.

I am surprised though that there still do not appear to be any  lithium versions of "Powertanks" from Celestron and Skywatcher, they could be half the weight AND twice the capacity of their current lead acid offerings.

 

 

DSCF4216.JPG

DSCF4217.JPG

Edited by Astro-Geek
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I’ve been using a 22ah lifepo4 golf trolley battery i previously purchased for another project. They’re about £150 to buy but give a nice stable voltage and lifepo4 batteries are very safe compared to lipo and have an increased number of recharge cycles. 

Mine will give me about 9 hours run time powering a mini pc, dew heaters, mount and dslr. Total draw is about 30w. So it’s giving it’s rated capacity without issue. A built in BMS cuts off power before it gets to damaging levels of discharge. 

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2 hours ago, Astro-Geek said:

I am surprised though that there still do not appear to be any  lithium versions of "Powertanks" from Celestron and Skywatcher, they could be half the weight AND twice the capacity of their current lead acid offerings.

They do, see here.

Lithium batteries (polymer) do indeed have an advantage of less weight, but they are far more prone to severe consequences if damaged so need to be protected a little more than SLA's,  which can take a bit of a beating.  

The biggest downside of them is cost per Ah, which is significantly higher than the comparable SLA or gel type.

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LiFeP04 (Lithium iron phosphate battery) are an extremely safe battery as unlike regular LiPo batteries they are non combustible. However they are a lot more expensive to manufacture and if buying one you need to make sure that they are UN 38.3 certified. There are cheaper Chinese versions that don’t meet the standards.

Edited by johninderby
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5 hours ago, RayD said:

They do, see here.

Lithium batteries (polymer) do indeed have an advantage of less weight, but they are far more prone to severe consequences if damaged so need to be protected a little more than SLA's,  which can take a bit of a beating.  

The biggest downside of them is cost per Ah, which is significantly higher than the comparable SLA or gel type.

The link you sent didn't work for me.. do you have a product number (or something) for it at all ? Also roughly what kind of life in hours should I expect from a full charge in your experience ?

Many thanks.

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Looking from the list kindly supplied at the LiFePO4 Powertank and Powertank Pro, anyone have any experience as to the run time per full charge (roughly) when using a goto set up ?

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7 hours ago, RayD said:

They do, see here.

Lithium batteries (polymer) do indeed have an advantage of less weight, but they are far more prone to severe consequences if damaged so need to be protected a little more than SLA's,  which can take a bit of a beating.  

The biggest downside of them is cost per Ah, which is significantly higher than the comparable SLA or gel type.

I stand corrected Ray, though it seems a poor relation to the lead acid powertanks, without the seemingly universal car cig lighter sockets.

All of my motorised mounts and dew heaters etc are fitted with cig lighter plugs, even my skywatcher dual axis 6v drive, via a hard wired cig lighter plug with a built in 6v dropper.

 

Edit -  Oops, I didn't notice the inconspicuous cig lighter socket built into the side, behind the orange circular trim.

Sorry to keep sounding negative, but it appears to only have one, whereas the lead acid power tanks had two.  Strange that the much more expensive item is more limited.

Edited by Astro-Geek

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The Tracer batteries like these have a range of quick disconnect adaptors available to make it easy to connect to anything.

96EDF0E2-32DA-4D65-820B-093EA7C9E650.jpeg

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4 minutes ago, Astro-Geek said:

I stand corrected Ray, though it seems a poor relation to the lead acid powertanks, without the seemingly universal car cig lighter sockets.

All of my motorised mounts and dew heaters etc are fitted with cig lighter plugs, even my skywatcher dual axis 6v drive, via a hard wired cig lighter plug with a built in 6v dropper.

No, not a problem at all.  I don't think they are mentioned that often as they are pretty costly for the relatively low power output.

The Celestron ones seem quite useful as they have lights and USB outputs etc. which can be a plus.  However, you do seem to be paying a premium for the brand name, albeit you will pay quite a bit more for any LiFePO4 batteries over SLA's.

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Take a look at the MaxOak 50,000mAh at around £113 on Amazon. Offers an enormous 185 watt-hours, and when outputting 12v/2.5A will last all night.

The joy of this power unit is that it is no larger than a 10" tablet (but around 1" thick) and is light enough it can be velcroed to a mount. It is much cheaper than the price of a 8Ah Tracer and less than half the price of  larger Tracer units. I have used one for over a year trouble free.  The only downside is the 2.5A limit. 

 

 

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16 minutes ago, noah4x4 said:

Take a look at the MaxOak 50,000mAh at around £113 on Amazon. Offers an enormous 185 watt-hours, and when outputting 12v/2.5A will last all night.

The joy of this power unit is that it is no larger than a 10" tablet (but around 1" thick) and is light enough it can be velcroed to a mount. It is much cheaper than the price of a 8Ah Tracer and less than half the price of  larger Tracer units. I have used one for over a year trouble free.  The only downside is the 2.5A limit. 

 

 

I am a complete newbie, have to admit, so sorry for the silly question. Why is 2.5A limit a downside ?

Just checked out the unit on Amazon, nice price and great reviews. Is everything included when purchased that allows me to hook up my telescope/mount/etc (Would be using it on a Nexstar 6SE) or do I need to purchase anything else ?

Thanks

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15 minutes ago, noah4x4 said:

Take a look at the MaxOak 50,000mAh at around £113 on Amazon. Offers an enormous 185 watt-hours, and when outputting 12v/2.5A will last all night.

The joy of this power unit is that it is no larger than a 10" tablet (but around 1" thick) and is light enough it can be velcroed to a mount. It is much cheaper than the price of a 8Ah Tracer and less than half the price of  larger Tracer units. I have used one for over a year trouble free.  The only downside is the 2.5A limit. 

 

 

Yes, a very compact 50 amp/hr battery pack.  These things keep improving, it's difficult to stay informed of what's available.

The main downside as you say, is the 2.5 amp limit on the single 12v output port. 

It's a bit of a jack of all trades, with the 20v notebook outputs as well as the 5v USB.

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The MaxOaks 2.5 Amp limit at 12v is plenty enough to power a Nexstar SE all night. 

However, if you added (say) a camera, dew shield (etc) and their combined amps drawn down exceeded 2.5 amps it would not be enough. You obviously want a stable 12 volts. But you always want to have more amps available than your equipment rating.  However, your equipment will only draw down what it needs. The solution is get two! 

As regards connections, the MaxOak supplies multiple leads including one that fits the SE series. 

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2 minutes ago, noah4x4 said:

The MaxOaks 2.5 Amp limit at 12v is plenty enough to power a Nexstar SE all night. 

However, if you added (say) a camera, dew shield (etc) and their combined amps drawn down exceeded 2.5 amps it would not be enough. You obviously want a stable 12 volts. But you always want to have more amps available than your equipment rating.  However, your equipment will only draw down what it needs. The solution is get two! 

As regards connections, the MaxOak supplies multiple leads including one that fits the SE series. 

Superb, thank you very much for the info. Only extras I would have would be either the WIFI attachment (so I can use my phone) or the GPS attachment when I go dark and deep somewhere, so I assume they wouldn't make any difference.

Looks like I will be purchasing one of these and getting rid of my Celestron Powertank :) 

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