Looking to make a field battery

Hi Brian
I have two thoughts on what you have drawn
1) If you are going to draw 80amps or close to it, your 100amp battery isn't going to last very long.
2) It would be much better to use multiple batteries which will also protect one piece of equipment from spikes from another.

My setup uses one battery for the camera, one for the mount and focus motor, and one for the computer.
All 100amp and 80apm/hr batteries. With this setup, I can easily get two nights of imaging, 3 in the summer.

Scott

Thank you for the wiring unlimited document Greg, that has been a very useful read! I will need to go through it again another time or two.

@Greg McCall, do you mind posting a picture of fuse bussman? I would like to see how it is connected and how you connect the charger to it.

The back of the power poles mount look like this, so that is why I had to lines coming out of the fuse block. Is it better to have a single line and split it at the plug?



Regarding the 80 amp fuse. I was just trying to make sure I can run all the plugs at once, but that will be far from the norm. I was also planning on using one of the many wire size calculators online. I tried to indicate that by drawing fatter wires in my diagram.

Most of the time it will be just me using it, but I want to be able to support my friend when he wants to go.

My telescope will take 4 amps to run the camera/telescope/etc and a separate 5 amp line for dew heaters on the extremely rare nights I need those (I live in Phoenix). 
My computer has a large battery that can last most of the night, but would pull 2.5 amps from that cigarette lighter. The cigarette lighter is rated for 15 amps, so I figured I would have a fuse big enough for those times I want to plug something else into it.

On a normal night for me, I should be able to have ~16 hours of battery life. An 8 hour night would take me to 50% which I hear is fine for LiFePO4 batteries. On the battle born website, it states:
"Conversely, LiFePO4 (Lithium Iron Phosphate) batteries can be continually discharged to 100% and there is no long-term effect. You can expect to easily get 3000 – 5000 cycles at this depth of discharge."

When my friend comes along, he will be using 2 more power pole connections and a usb connection for his camera. His gear pulls around 4 amps.
I will still have 8-10 hours of battery life between the two of us.

It will be learning experience with the battery to determine how it actually fits into my use case along with the random cellphone or tablet that is charged to keep the support crew entertained.

Regarding using separate batteries. I have an iOptron CEM 70g, which passes electricity from the ground to the dec plate, so I have been running everything off of a shared line already.

I’d say that if you like the way you have everything setup, stay with that. The one thing I would change is, unless you really want to spend $900 on a single lithium-ion battery, I’d go with 2 or 3 good AGM 100+ Ah deep cycle batteries, and you’d probably still have some cash left over.

Thanks for the feedback guys. I would like to stick with LiFePO4 just for the weight and deep discharge advantages. I have updated my fuse to an MRBF as suggested.

I have been looking at the victron battery protect to add the ability to automatically disconnect the battery when it is below a certain charge. It seems like you need to have one for the charging line and one for the load line. Is there a better solution for this?

https://www.victronenergy.com/battery_protect/battery-protect
Page 3 here
https://www.victronenergy.com/upload/documents/Manual-Battery-Protect-12V-24V-65-A-100-A--220-A-EN-NL-FR-SV-DE-PT-ES-TR-IT.pdf

Thanks. I'll switch it down to a 40amp fuse.

I found a pelican box that everything should fit comfortably inside of.
https://www.pelican.com/us/en/product/cases/cargo/bx80

I attempted to draw it up in CAD. I didn't realize the radio and speakers were going to take up so much space, but there is still plenty of room between that and the battery.

How did you strap your battery down to make sure it doesn't move?

Looks like the very special briefcase of the US president.  

Nah, seriously: Looks very professional!

>What suggestions or changes do you have? 

A fire extinguisher 🤡

Seriously, this is an inspiring project. A power pack like yours would also be great for black-outs during and after a typhoon, etc.
Best luck!
Robert

Getting a headache looking at this already  the magic of electrics isn't made for me.
But I am interested in one day getting a field battery, but would get one off the shelve most likely. 
Since.. well.. I'm not expert on magic.. Probably something, including solar power, that you'd throw in the back of a caravan or camper. 

Question: how do you know if a battery is powerful enough to keep your stuff running?
is there a simple way of knowing? Or would it be:
- calculating the watts for every single item individually,
-adding it up..
-times it by the hours I'd want to run it,
- and figuring it out that way.
...

Hi Steven,

This is exactly what you do. Each device should have how many amps it draws available on the manufacturer website for you to add up.
As a rough approximation, you could power everything through a kill-a-watt type device to see how much power you use in a typical night and convert from your mains voltage down to 12 volt to determine your amp hours needed.

That is incredibly cool and very professional looking. Thanks for the inspiration! I think it's time for me to break out my electrician's tools and get to work on something similar for myself.

Hi Brian
Very impressive. I have two questions though
1) How much did you end up spending on the whole package?
2)How long will it run your set up before needing to be recharged?

Scott