Field Power Supply Ideas

[Slowtwitch]

Hi everyone. I've laid out a small heap of cash already getting my scope and eyepieces etc, but I'm now a little limited on budget for a field power supply for my Celestron Nexstar 5SE. Ive seen on eBay there are small 12v Nimh battery packs designed for boosting a vehicle battery. Has anyone had experience of these, or perhaps have any idea whether they are a good or bad idea for a scopes goto mount? 

Many thanks. 

[Geoff Lister]

I would expect your power requirements are similar to those of the Skywatcher Skymax 127. Have a look at my reply in the companion thread in this section of the forum:-

"Skywatcher AZ GOTO power supply/battery requirements". This may answer your question.

The car booster packs often have a lead-acid battery with a capacity of 7 to 17 Amp-hours.

Geoff

[Slowtwitch]

Thanks for reply. I can't open the link. It may be my phone is the problem. I'll try again when I'm at work. 

[TareqPhoto]

Ok, i bought my mount and i never had an idea about the power supply, and when i saw the power cable i was going to suicide or cry as i bought that expensive mount and didn't figure out how to power it, but, that cable end just lighted up my mind about something i had for a while and didn't use it, wasn't sure if it will work or not, so i searched in the house and found this power battery i bought while ago, so i plugged it in and.... VIOLA, it worked, i immediately recharged it for use.

https://s26.postimg.org/d9yqutbjr/IMG_5415.jpg

https://s26.postimg.org/bw73zicaf/IMG_5416.jpg

I visited one store for Solar items, and saw same this battery there and another one smaller and another one bigger, and they can be charged by sun, so i was thinking if i buy that bigger one with a solar cell for recharging then i am all set, but i asked about that bigger one being overkill or may damage my mount and didn't get the answer, but if your mount is similar to my mount then this battery i have can power it just fine, and i found them cheap in my country, the one i have is nearly about $30-40, the bigger one is about $50-60 at most, and if i add that solar cell it may go up to around $150, but then i can recharge with the sun so i save the electricity at home and have my battery charged all the time during the day time.

[jbrazio]

Where I live the cheapest (and most long term solution) is to buy a common (40Ah) automotive 12V lead acid battery.. I must advise you that it's not the lightest solution. You may also go, as already suggested, to a 12V lead acid battery commonly used for solar applications thus usually overpriced.

[Geoff Lister]

A car starter/jumper pack, similar to this one:-

http://www.halfords.com/workshop-tools/garage-equipment/battery-chargers-jump-starters/phaze-4-in-1-jump-starter

has 17Ah capacity, can be carried with 1 hand, and has a recharging controller built-in. If you plug its mains plug-top supply into a plug-in timer switch, 30 minutes-a-day top up will keep it happy. You may need to make up a lead from the pack's cigarette lighter output to the mount's 2.1mm ID/5.5mm OD power jack.

Geoff

[newbie alert]

The Halfords one in the link above is what I use..had it about 9 months without issues..

I bought a celestron one when I first got my scope and it only lasted about a year before it started playing up...so a 17ah for £40 Or a 8ah for £60....

[Geoff Lister]

Lead-acid batteries like to be kept topped-up, as you do when you use your car every day. Leave the car for 4 weeks in the garage, and it will not be so happy starting the car.

NiCad cells like to be cycled, otherwise a "memory" effect reduces their useful capacity. NiMH cells have a higher capacity than NiCad, and do not suffer, to the same extent, with the memory effect.

LiPO batteries need a dedicated charger to connect to each cell to balance the charge, and are best left half-charged if not to be used for a few days; they also do not like being completely discharged.

The 8 or 10-cell holders tend to give a higher-resistance contact unless the contact surfaces are kept clean. This can give an unacceptable voltage drop when slewing the mount at high speed.

My selection:-

Geoff

[jbrazio]

Geoff I'm not understanding.. You did a good layout of all the cons for each battery type and then in the end of the day you use one battery pack of each kind plus AC ?

[Geoff Lister]

Sorry for any confusion. These are all possible alternatives.

I tend to use the plug-top 12V 2A mains supply in my back garden.

The battery holder supplied with the mount takes 8-off 1.5V alkaline cells. If you use NiMH rechargeables, with a nominal terminal voltage of 1.2V, the output is 9.6V, too low for the mount.

I obtained a battery holder that takes 5 cells each side, so 10 in total, giving 12V, and added the lead and plug. I found that this did not give reliable operation, due to dirt pickup, unless I cleaned the holder's contacts regularly.

I also sail radio-controlled model yachts, so I had some 6V 2600mAh 5-AA-cell battery packs, used to power the receiver and servos. I made up a "Y" lead to join 2 packs in series, to give 12V. these 2 packs fit neatly in the little satchel supplied with the mount. This is what I tend to use if away from mains supplies. I also added a stick-on plastic hook, on the rotating part of the mount, to hold the satchel.

The LiPO battery pack has a nominal 11.1V output so I thought I would give it a try, and it seems to work. It does need a dedicated charger. If not used properly, you can have similar problems to those experienced recently by Samsung Note 7 phone users.

I hope this answers your questions.

[Slowtwitch]

Thanks for all your input guys. I'll have to have a good think about how I'm going to go forwards with this one.