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Posted (edited)

Hello,

How do I create a mobile power bank for my equipment? How much power do I need for this rig? I don't need to use it for imaging two or three nights so I'm fine using a smaller and lighter battery. I'm not an electrician or anything :)

I currently have a battery set up but it isn't working for me because it ends up saying low voltage after about 30 minutes (I'm using a huge 100Ah battery). I need a regulator/stabilizer to run the mount and Primalucelab Eagle computer.

The electronics I am using:
SBIG ST-8300M w/ filterwheel and OAG camera
Astro-Physics Mach1GTO w/ CP4
Moonlite Nitecrawler 3"
Primalucelab Eagle 2
Primalucelab ECCO w/ dew heater band

Thanks :)

Christopher

 

 

SVX152_2.jpg

 

Edited by stardude07

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what type of battery is the 100Ah one and how old is it? If its dropping to low voltage after such a short time it sounds like maybe one cell is failing and then the volts would drop to 11.2v or there abouts. It would be worth using a multimeter and checking the terminal voltage at the battery off load after charging and then while on load and see what is happening. Assuming its a regular SLA battery it should read around 13.6v after charging and settle time, if left a few hours (or next day having sat unused) check again and see how far that drops. If it then reads 11.xv with no load then it'll confirm a cell has failed.

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It is a deep cycle battery (marine) and is about a year or year and a half old. I checked the fluid levels and they haven't really decreased but by a few millimeters however the plates are completely submerged. What is very strange is the in-line voltage meter on the battery reads high however the Primalucelab Eagle says it's receiving lower than 12v after 30 minutes or so. The multimeter says each port shows 12v-13.6v depending on the charge. So I'm quite confused.

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Posted (edited)

If the voltage on the battery itself reads OK but the Primalucelab Eagle says it's too low then the wiring from the battery to the Eagle is not thick enough or one of the connections between the two is giving a poor contact. This would lead to the resistance between the battery and Eagle being too high causing excessive voltage drop. Can you post a picture of it all connected together or describe how it's done.

Alan

Edited by symmetal

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I see. Here's how it goes:

The Eagle is mounted on top of the telescope which has a cable made by Primalucelab that screws onto the back of it and goes through the mount down to the battery box (the battery box was built by a friend and has worked up until me taking a 3 month break from using the battery/telescope). I see how the wiring is connected but I'm not an expert on it so I'll see if you can decipher how it's all linked up.

PS Something interesting is that I don't seem to have any power issues if I have the charger hooked up to the battery while I'm running the telescope. It's been taking calibration images for the past 14 hours with now power issues. The Eagle reads 12.4V while the battery volt meter reads 13.39v.

 

1342181593_Inked64436951_108592827080249_435572330207379456_n1_LI.jpg.798c6a314ee6ac5eec41e56307a4aa7b.jpg           Line comes from Eagle, through mount down to the battery box.

 

Inked1_LI.thumb.jpg.2735a595b601a1f4ed3535008c50baa5.jpg          Line comes into the stabilized (or regulated?) cigarette lighter and down to the battery I think.

 

Inked2_LI.thumb.jpg.7e1624771da1060371bc17855f732910.jpg          Line jumps through all kinds of confusing places and then down to the battery.

 

 

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IF both of the meters are correct, then you are dropping 0.9 volt between battery & mount, so I suspect that some of the connectors\wiring have some resistance, possibly due to non use, so give everything a good clean, even fuses\fuse holders are not immune to tarnishing.

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Posted (edited)

Thanks for the pictures. The wiring thickness and construction looks fine. I see you're using a voltage stabiliser to feed power to the Eagle. This is probably putting out 12.0V irrespective of the battery voltage. If you have a bit of resistance on the connectors it could easily drop by another 0.2 to 0.5V by the time it reaches the Eagle. It doesn't look like the stabiliser is adjustable but if it is I would adjust it to give out at least 12.5V which should cure your problem. On your last photo the battery voltage is going in the bottom of the stabiliser and the stabiliser output comes out the top going via the switch and fuse to the cigar socket feeding the Eagle. Give these connections a little wiggle to check they are all tight and remove and re-seat the fuse whose contacts may have become a little tarnished as Julian said. You can measure the voltage going into and out of the stabiliser on its terminals, the voltage coming out should be no more than about 0.1V higher compared to the Eagle voltage. That's assuming the voltmeters are calibrated to read correctly which isn't always the case.

Edit: The stabiliser is adjustable, as looking at this one which looks very similar, the blue potentiometer next to the output terminals, labelled CV, sets the output voltage. This is just visible on your photo. So after checking the connections are tight adjust this potentiometer until the Eagle is happy with the voltage. I would set it to read 12.5V at the Eagle and then as a check, measure the voltage at the stabiliser output terminals. This would probably read 12.6 to 12.7V which would be fine. 

601083945_VoltReg.png.8d3ecc4fcf1423facefdba4444357cd2.png

Alan

Edited by symmetal
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Thank you for all the great information, I will test this out either tonight or tomorrow and let you know the results.

Christopher

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I finally solved the issue. It turns out I did need to up the output voltage regulation. I set that to around 14.1 volts. Thank you all very much! Problem solved!

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Glad that fixed it. Does it need to be as high as that. What does it measure on the Eagle, as the Eagle manual suggests 12.8V at the input to the Eagle as the camera and any 12V equipment will get this same voltage.

Alan

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I called around to all the companies for the products I use and they said about 14.1 is the median for all devices.

Christopher

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