7 replies to this topic

[GTom]

I am planning several off-grid trips in the future and instead of buying an otherwise ideal LiFePO4 battery I thought I could use a 110Ah leisure gel battery collecting dust in the shed anyway.

 

However, lead-acid dips quickly below 12V and one could forget 13+Voltages. My camera (Moravian g3) likes 13-13.5V, cooling efficiency is AFAIK the best in this range.

Can I just add a cheap buck-boost converter to push above 12V? Or shall I fear all kind of noise and interference from the converter that affect the camera operation/introduces random noise on the image?

[pedxing]

I use a buck-boost to keep my voltage steady at 13V, that is definitely a valid approach.

 

I haven't had interference problems - I checked mine out with an oscilloscope and there was no significant noise, at least at lower frequencies.

 

I did put an RF choke on the cable I run to the camera just to be sure.

 

Haven't had any issues for several years.

[andysea]

If your G3 is a CCD camera then it can absolutely be affected by power supply issues. I had vertical banding in my G3 16200 which I believe was caused by something in my power train, I suspect too low voltage. Maybe test it first before you waste a night of imaging?

In my experience CCD cameras are way more susceptible to power issues than CMOS, some manufacturers more than others.

Edited by andysea, 30 August 2023 - 08:36 PM.

[TopherTheME]

I wouldn't use a 'cheap' buck-boost converter but a reasonable quality one, such as from a manufacturer like meanwell, should work perfectly fine. 

[TelescopeGreg]

Um, back up.  How long has that battery been sitting in the shed?  If it hasn't been kept on a proper maintenance cycle (float charging, or similar), it's very likely shot. 

 

Just sitting there unloaded, the battery should be at about 12.8 volts, and it shouldn't drop below 12 until it's been drawn on for a while.  That battery is 2x the size of what I use (I have a 55AH AGM), and I don't drop down to 12.0v for hours, even under load.

 

I'd give it a good full charge and take it to an auto parts place and have them do a load test on it.

[SDTopensied]

Check out a LiFePo4 (Lithium Iron Phosphate) battery.  My 100 amp hour lead acid battery weighed a little over 80 pounds.  My 100 LiFePo4 battery weighs just under 15 pounds.  The discharge curve is more like a cliff.  Your buck converter will pull more current as voltage drops, further accelerating the battery's demise for the evening.  The discharge cliff of the LiFePo4 battery will give you the power you need throughout the night and it will fit in a Group 24 marine battery box.

 

-Steve

[Drothgeb]

Like was mentioned, I’d do a load test first. If it test fine. and the standing voltage is 12.6 or higher, it could work. But, the voltage curve and extra drain from the boost converter, still makes it a little iffy for off the grid travel. 
 

My wife and I do off the grid camping, I’ve switched everything to LiFePO batteries. More power and less weight. For the astro rigs, I have (2) 60ah, and a 30ah. I can also pull one of the 120ah out of the camper if I need too. Personally I’d switch just on weight alone. My 60ah are 14 lbs, the 120s are 27 lbs. I just pulled the 105ah lead batteries out of the camper a couple of months ago, no way I’d want to lug them around for astrophotography.

[GTom]

If your G3 is a CCD camera then it can absolutely be affected by power supply issues. I had vertical banding in my G3 16200 which I believe was caused by something in my power train, I suspect too low voltage. Maybe test it first before you waste a night of imaging?

In my experience CCD cameras are way more susceptible to power issues than CMOS, some manufacturers more than others.

Thank you Andy. Will do the tests soon. The cleanest solution is a LiFePO4 battery supplying clean ~13-13.5V DC, in case any issues I'll resort to that. Right now I only have a small, 7.2Ah LiFePO4 unit, but that will be plenty for testing reference.

 

With Lead Acid I expect two possible deal-breakers: too low voltage (might be still OK with a large bank where 5A load means 0.05C) or if a booster applied, noise. Noise can very well cause severe banding as well, saw that with el cheapo CMOS cameras where the cooling and the imaging circuits were not properly separated.

 

Um, back up.  How long has that battery been sitting in the shed?  If it hasn't been kept on a proper maintenance cycle (float charging, or similar), it's very likely shot. 

 

Just sitting there unloaded, the battery should be at about 12.8 volts, and it shouldn't drop below 12 until it's been drawn on for a while.  That battery is 2x the size of what I use (I have a 55AH AGM), and I don't drop down to 12.0v for hours, even under load.

 

I'd give it a good full charge and take it to an auto parts place and have them do a load test on it.

Dont you worry, I kept it fully charged . Not used but not neglected either. It's 3 years old now and got a top-up every 2-3 months.

Edited by GTom, 31 August 2023 - 08:03 PM.