An update regarding power requirements;..
Inevitably, large sensor/megapixel cameras and/or complex EAA set ups will require more processing and battery power, especially where large blocks of data is being processed and then transferred over a wholly wireless and cable free network from a computer situated at the telescope to a remote laptop (e.g. in the warm!). I eventually decided to purchase an Intel NUC i-5 which offers more than the necessary power and room to future proof. Finding the computing power isn't challenging.
Battery power is hence the last conundrum to be solved and it is not proving easy with the Intel NUC and a large data intensive camera.... unless prepared to take a risk (albeit one that from other CN'er experience appears slight).....
My Evolution telescope has its own internal battery offering up to 10 hours, so that is one requirement neatly ticked off the list. I then built this simple 'cradle' suitable to hold my Tracer 12v 8Ah battery which is used to power my Atik Horizon and Focuser Motor and to also embrace a '2-Power' 27Ah 19v battery to power my NUC i5. If I want to later adopt (say) a slightly larger MaxOak K2 50Ah I can simply make the inner compartment wider by using 40mm M4 bolts/spacers rather than the 30mm depicted. This arrangement is incredibly compact and it all rotates with the mount (so no cord wrap). It simply straps to the Evolution mount arm using (wide/long) Zacfton cable ties. It is neat, but power remains an issue....
The reason I didn't adopt the MaxOak K2 50Ah power bank (n.b. which was highly praised by a couple of CN'ers) was that both its manufacturer (KayoMaxstar) and Intel Support refuse to confirm that its 20v output is satisfactory for the "12v -19v" NUC. KayoMaster even wrote to me (unpromoted) to query my order and to express concern over Intel NUC compatibility. Yet KayoMaster is willing to confirm compatibility with Toshiba, Dell, HP (etc) laptops and with most other manufacturers that specify 20v. Intel NUC's (specified at "12v to 19v", but with a vague reference to + or - 10%) do seem to be a rare beast. I have had mine working perfectly from my Tracer 12v 8Ah. However, Intel Support warned me that if run below 11.6v then damage was also possible (so the Maxoak K2 might have a potential problems at both ends). By contrast, Tracer guarantee power stability at 12v and that is probably why its Li-Po batteries are vastly so much more expensive than lesser known Far East manufactured power banks. The Tracer 12v 8Ah retails at £129.97 which is more expensive than either of the (at least 3 x capacity) 27Ah and 50Ah options discussed here. .
Some CN'ers have tested this further (see posts above) and it appears that the output of a NUC's standard (mains) adapter and the MaxOax K2 both appear to be around 19.3v. There is normally a + or - 5% tolerance, so Intel's (and KayoMaxstar) stubbornness is rather strange. Maybe it is because the NUC is normally a kit computer and the manufacturer has no control over the extra components (but mine is a complete computer). However, Intel Support advised me that if I bought the MaxOak K2 it would be advisable to also get a DEC/DEC converter (£59.99). However, RAC19 has a MaxOak K2 50 Ah (£109.99) and is running his i-3 NUC (I believe that is at 12v) without any mishap. Maybe I am just over cautious? Instead I bought a '2-Power' 27Ah power bank (£118.80) which was the only other compact unit I found at a reasonable price with decent capacity guaranteed to be compatible with a NUC.
Most 'Power Tanks' from telescope manufacturers are limited to merely 7Ah to 17Ah. The biggest Tracer compact sized Li-Po is 22Ah and costs £241. The (brick like) Deben Tracer Lithium Phosphate 12v Battery Pack (£215) is merely 16Ah. A Tracer 12v 40Ah Peli case battery is over £700 and hardly 'compact'. I also didn't want to adopt a massive brick of a Lead-Acid battery as these are at least four times the weight and double the price of these compact units, which would defeat the objective of developing a lightweight, wireless, cordless rig (8" OTA) that I can carry fully assembled from my 'office' to its location. Unfortunately, set up times of 30 minutes are wasteful under typical UK skies where the clouds are never far away, hence my quest.
Sorry for the long preamble to put things into context, but my reason for posting is to report that I got an encouraging five hours duration from the 27Ah '2-Power' power bank into the NUC when idling (simply running Windows on the NUC). This suggests the NUC has less than 20w consumption when idle. However, I then fully recharged the power bank and put it under an extreme load of APPs (probably circa 50w load) and the duration dropped to merely three hours and twenty minutes. It is clearly quite sensitive to wattage 'load' (as we had earlier predicted). I reckon that with the slightly less demanding Atik camera (note; just processing its data) then FOUR HOURS duration is probably the best case scenario (I am still awaiting delivery of my camera to test it more fully - hurry up Santa!). To be fair, from merely the 8Ah from my Tracer I doubt if I will get any longer duration power for camera and focuser. So four hours of EAA on this battery set up looks like the limit.
Three plus hours is fine for me when at home as I rarely get more than a three hour break between the clouds. Also, if I want to be out for longer I do have close proximity to outdoor RCD protected mains power (I then put any adapters in a wholly waterproof socket box). But I suspect folk might be disappointed with three hours if at a dark sky site. However, a Celestron or SkyWatcher 17Ah Power Tank will inevitably last an even shorter duration at 50w (and that assumes you are not also powering a telescope). Most regular laptops will struggle to give you more than four hours without supplementary power, so a second battery does seem inevitable, unless one does purchase a MaxOak K2 (n.b. RAC19 has comfortably had his MaxOak K2 running his NUC for over EIGHT hours - awesome!).
Maybe the only battery solutions for longer duration EAA with a NUC and large sensor camera are to buy TWO x '2-Power' 27Ah (or two x Tracer 22Ah); or invest £700 in a 40Ah Tracer; unless prepared to risk the MaxOak K2; or carry the huge 'brick' of a lead-acid or similar. Frankly, if RAC19's NUC is still alive by the time that I next want to venture to a dark sky site (Spring), I will probably succumb to the MaxOak K2. Thanks RAC19 for your bravery. But if anybody has another idea that provides a certain 19V (or a certain 12v - 18v) from a COMPACT battery or power bank with a capacity above (say) 40Ah then please add to this thread. Or is the Maxoak K2 50Ah unique? Hopefully many more CN'ers will report on their experiences with a NUC (or Compute Stick etc.).
Edited by Noah4x4, 19 January 2018 - 12:48 PM.