Sorry to flog a dead horse. I've found several posts / threads regarding external power sources for mounts. At the moment I don't have any gear, but I'm adding up the $ and weight etc before diving in and purchasing everything only to then find out I forgot to consider something plus my budget has been blown WAY over what I initially envisaged haha.
So, I'm currently looking at purchasing an HEQ-5 pro (goto) and initially just mount a 200mm f2.8 lens onto my camera (nex5n) which gives me a 300mm @35mm equivalent, or a 300mm f4 lens (450mm equivalent). I won't be going down the guidescope way at the moment because of cost and apparently wide-field imaging should be alright for a couple minutes / sub so will be relying on accurate polar alignment and worm gears (please correct me if i'm wrong here).
Anyway, to summarise my findings, I can either go for the supercheap auto 900A (i think it's mA?) battery here http://www.supercheapauto.com.au/onl...46#Description which I've read is a 17mAh battery (so lets say effective drain @average of 2A/hour over 50% drain = about 4-5 hours usage) or I can wire my own deep charge battery (which I would rather not do). I've also read differences about charge cycles etc for the two kind of batteries and it's all rather confusing. Is there any reason why I can't use something like this http://www.ebay.com.au/itm/12V-Porta...item3f1b705a52 which says it can output 5A at 20Ah and because it is a lithium battery, I can drain it much lower? There is also the 10A rated one here http://www.ebay.com.au/itm/12V-10A-P...item3f1ad97c3f
Hi Matthew,
I've got an EQ5 GOTO which I believe can draw about 2A. So I bought a 12v 20Ah (I think it's SLA and I think it's a Panasonic) battery from a "batteryworld" store in Sydney (they are in Melbourne too). The guy in the shop made me a cable with a lighter socket at the end while I waited in store, and he did a really good job as it feels nice and sturdy.
All up for the battery and the charger and the cable it cost me $240.
I hope this helps :-)
I gave up on "battery packs" many years ago.
Went over to the 20Ah gel cell (mobility scooters/ golf buggies) battery combined with a triple stage electronic charger (it can NEVER cook your battery) they have lasted over seven years and still going strong.
The max amp draw (at 12V) on the HEQ5pro/ NEQ6pro is, with both axis on max slew, just less than 2A...normal tracking <1A
Thansk for the resposnes guys. How long do you find you get our of your batteries? Are they only ~50% drain types, so you get around 5 hours use? I'm trying to do it a bit cheaper since the mount is already blowing my budget - puts $240 at too high a price to pay. I figure I'd only be using maybe 3-4 hours of juice since I don't see myself sitting out in the cold all night and it should be enough to get some good shots. Of course there is the AP-bug where I'm sure I'll have to upgrade and buy all sorts of accessories later, but we'll deal with that when the time comes
One of the reasons I was looking at the lithium batteries was the charging.. they come with a wall charger and I don't have to deal with hydrogen peroxide gas being created with some of the lead batteries. I also like that about the jump start pack, but I've read that some battery types are better for this sort of use than others. Another reason is the weight. Most of the 12V batteries I've seen (car, marine etc) tend to be pretty hefty and it would be nice to retain some decorum of portability with my rig. At the moment it's mount (~10kg?) + camera + lens, so it's manageable.
Matthew, do you really need the portability of batteries? Many people find they are always within 30m of a 240V power socket even visiting dark sky sites. If you only go bush from time to time, may not be worth spending so much on batteries and chargers. The advice to buy a good quality battery and charger is wise. Powerpacks contain pretty small cheap batteries and very poor chargers. You might only get a year or two.
Decent 240V supply for DSE (or Jaycar) usually about $60 from memory. That's what I use 95% of the time now.
Hi Rob, I live in the cbd so I will have to travel out some distance to get away from the city lights. I'm not sure what most people do, but I figured I would end up heading up the mountains or maybe park off the side of a highway and set up there - and didn't want to kill the car battery. That's why I thought something that would last maybe a few hours would be fine. Don't see myself sitting out there the whole night and I wouldn't want to leave my gear out on its own anyway. I think I'd be pretty happy to have something that lasted 4 hours safely - lets say 30 minutes of me stuffing around setting up and then 2-3 hours for imaging.
WHat is the 240V supply that you use? a step down transformer?
Hi Matthew,
I'm pretty sure you can get smaller versions of the one I have as it is pretty heavy (maybe 7kgs...?). Also mine is a sealed battery so no worries about ventilation. When mine is not in use it lives on its charger as the guy at the shop recommended, and it can be discharged pretty much all the way without any problems.
I haven't had a full night out with it yet so I don't know how long it will last in practice but in theory it should last well over 10 hours with my setup.
Here is a pic of it for reference:
Hi Matthew
my 2 bobs worth, running a HEQ5 mount on battery power :
My current setup uses a SCA 1900 'jump start' unit which reputedly has a 30+ AmpHr battery and certainly feels heavy enough.
Its weight is actually useful as I hang it from a hook under the centre post. In that way, it provides the tripod with extra mass and stability. (and on those public nights when the visitors kick the tripod : nothing moves ! )
I also added a 'merit' plug which offers more positive connection than a ciggie lighter, and I also secure the cable so there is no weight or pull on the HEQ5 socket when the mount slews. I also used heavier duty flexible cable to minimise voltage drop when slewing.
The big battery also offers enough capacity to run a 12V hair dryer for a few minutes as occasionally required. I do 'park' the scope first though, but leave the power on. By the time I have put the dryer away, the voltage has recovered enough to use the mount again, and I can re-slew to the last target. ( A small battery would be trashed quickly with such a 15Amp drain, however short.)
The battery is also fairly new so I have no idea of its potential life. It was cheap enough in the 1st place, so I am not too concerned. The supplied charger restores the 'full' LED by the following day. It is an unsophisticated charger and should not be left connected for days after 'full' as there is a risk of overcharging which can slowly kill SLA battery capacity.
Anyway, that is what works for me at the moment.
I personally also feel safer with a stand-alone low voltage supply system than extension leads and 240V adapters outside, particularly in dewy conditions.
good luck with your decisions
'M Thanks for your feedback guys. I'm leaning towards the cheapie 900amp version of the super cheap auto jump starter. From what I've read it should give me more than 4 hours of juice and if it comes with a charger, its a pretty good deal. As I am likely to stick with lenses rather than a telescope, I'm not sure if dew is an issue for me. Will have to find that out - if so, I guess I can get a larger battery to power a dew heater or hair dryer as necessary. Maybe rubber banding some of those pocket hand warmers may be a cheap option too
I usually use 240v to 12v 8amp transformer at home but when setting up in remote areas I have found this setup reasonable to use. 2 x 12v 900a jump starters connected in parallel I bought them on sale from Kmart about 2 years ago for $40 each, Im not sure how much they retail for now. They run the 12 inch LX200 and 2 dew heaters on full power for around 6 hours.
There are lots of thread on IIS describing how most battery packs are designed to be short duration high amps jump start devices. They're not designed for multiple discharge/recharge cycles. You can be lucky, but its not unusual for people to spend $100 on a jumppack, later buy a cheapish charger for $60, then later another replacement jumpack. You've spent $200 in no time when you originally didnt want to outlay more than say $60.
On the other hand, for about $200 you would have a quality rig with something like CTek 5 stage charger, and a decent deep cycle battery.
Quality battery is a bit more, but worth it, particularly once you accumulate more gear for dew heaters, laptops etc down the line as usually happens. If you still buy a powerpack, probably worth still buying the decent CTek charger to get best possible life and performance from your battery anyway.
Option for backyard 240V/12V, something like this
(can't find the 3A Dick Smith one I bought years ago for $60)
Trouble with astronomy is there's always a better quality option for 50-5000% more than you really wanted to pay, that you eventually wishing you'd bought
IMHO, the power requirements of your mount would seem to warrant a Gel Cell, which is usually what's inside those Supercheap Jump Starters. Buying a battery on its own without the fancy box probably makes sense. I already had one of those jump starters when I bought my ETX and it works well.
That said, I've been a fan of LiPo batteries for their capacity per kilo for some time as these are used by RC model aircraft & boats, where size and mass are factors. My dob's equatorial platform uses a 2.2 AH 11.1 volt LiPo, which will run it all night on a single charge, (although I always keep another in reserve). Charging needs to be done with a LiPo balancing charger which can be expensive, but it's only 165gm and measures 100x30x20mm.
IMHO, the power requirements of your mount would seem to warrant a Gel Cell, which is usually what's inside those Supercheap Jump Starters. Buying a battery on its own without the fancy box probably makes sense. I already had one of those jump starters when I bought my ETX and it works well.
That said, I've been a fan of LiPo batteries for their capacity per kilo for some time as these are used by RC model aircraft & boats, where size and mass are factors. My dob's equatorial platform uses a 2.2 AH 11.1 volt LiPo, which will run it all night on a single charge, (although I always keep another in reserve). Charging needs to be done with a LiPo balancing charger which can be expensive, but it's only 165gm and measures 100x30x20mm.
Yes, fully agree, LiPo cells give enormous bang for your buck, all my RC equipment run’s on them
Just be aware of the limited discharge and strict charging requirements.
The rule of thumb for LiPo’s is “don’t charge them in anything you can’t afford to lose”
They have enormous amounts of stored energy that can go wrong and burn the place down
For portability, I use my Heavy Duty 600A rated SCA Jump starter, normally lasts 6-8 hours just driving my HEQ5 Pro. Or when I am at home, it simply powers my dew heater for the finderscope guider.
I just bought a Jaycar 12V socketed mains powered DC power supply which puts out 7.5A, enough to run my Peltier cooler box for the DSLR (5Amps) and potentially the scope too (2A). This cost me $39.
Generally, to power the scope when I am at home, I simply roll out a power lead from the house and use the charger that came with the SCA Jump starter and this is only 1A rated, but seems to drive the scope well, even at full slew speeds without a problem.
The jump starter can be charged from a 12V socket in the car with the supplied 12V plug so, you can top it up on the drive to the dark site just to be sure and then if needed, jump start the car (or someone else's) should the need arise.....I have successfully done this with mine, even after 5 hours running the scope, and when I wanted to go to the shop, I found the car's interior light was still on and the battery was a goner, so I hooked it up and blammo, off I went.
I have used this jump starter to revive about 5 different peoples cars over 2 years and think its the bees knees to have in the boot, especially when you are down the shops and see someone in the rain with a flat battery, out comes the jump starter and they are off again, with a smile on their dial.
You can also take these apart quite easily and replace the battery if it dies later on down the track with one of the better suggested batteries others have mentioned, as it is simply connected with spade lugs and about the size of a small marine or motorcycle 12V battery.
Quite a reasonable price too (about $40-$60) for something so versatile.
wow, this discussion is great, thanks for all the posts guys! has anyone notice any issues with the non deep charge batteries? I read a few technical posts on them and they say for instance, that the ones they use in the jump start batteries don't output constant power. as they discharge, you can experience a decrease in current which may affect your equipment, whereas the deep charge ones are regulated to give constant current as it discharges. Peter and Graeme, do you guys have links to the lipo batteries that you use?
My LiPos come from a crowd called Hobby King in Hong Kong - hobbyking.com . Be aware that there are hundreds of different batteries.
LiPos come in nominal voltages of 7.4v (2S) , 11.1v (3S), 14.8v (4S), and so on. They hold their voltage steady until nearly exhausted. If they are allowed to discharge completely, they are history and cannot be recharged. As previously mentioned, they can deliver huge currents, especially when shorted, and can catch fire if this happens. I ALWAYS remove them from whatever they are powering and put them on the concrete floor when they are being charged, although I have never had a problem with them. If you look after them and charge them properly, you should get 400 to 500 cycles out of one. In a multiple cell pack, a charger which balances the cell voltages is essential, these cost from $7 to $120.
