Aux battery for beginners

[metropoj]

[Vanagon Nut]

[truepaul]

[kguarnotta]

ok -I'm a beginner on this too. My Syncro came with 2 Aux batteries. They are regular lead acid deep cycle marine batteries.

i've been reading about the LiFePo4 batteries, and how small they can be, and where you can fit them - lots of good info on those threads.

Currently my system works fine for the little I use the aux batteries. I'd like to understand how to calculate what my needs would be if I went camping for a few days, or a day etc.

Could someone point me to a website or basic formulas for figuring out need?

IE - I've got an Engel Fridge, which supposedly draws 1-2 amps/hr, but I'd also like to be able to charge phones and run a heater in the winter ...and other things..lights, maybe radio - I imagine it is probably pretty simple to make a spreadsheet and just input your loads, I'm just not sure how to enter my loads.

This is probably really obvious to determine my needs/wants but I want to make sure I calculate correctly. So formulas anyone? Ideally I'd replace my 2 big batteries with one small battery - or maybe I only need to run one of my aux batteries - most of the time, and just add the 2nd battery when I do a longer trip.

I've also got a 50 amp solar panel that would theoretically be adding or topping off the batteries - probably not faster than I would use...
_________________
-Kevin
Lincoln, MA

'86 Triple Knob Syncro w/EJ22
'78 Westy
'69 Single Cab
'65 Kombi - EZ-Camper

[SSWesty]

kguarnotta page one of this thread may help, l storyboarded it for someone which may help you think about your parameters. https://www.thesamba.com/vw/forum/viewtopic.php?t=718824

You are on the right track to figure out your load which will allow you to make a data driven decision vs winging it with a 100amp battery. Thanks for explaining your situation, some folks just ask what should I do with no info on their usage. It would be like popping on here and asking how much water should I take camping. I have no clue if it's just you camping or family of 4 with a dog going for a weekend or off grid for a week.

You'll need to look up specs for the stuff you run like your Engel. Say it draws 1.5amps running and it runs 50% of the time that would be 12 hours per day X 1.5 amps = 18 amp hours per day. Move on the lights, radio, etc. The formula is simple Volts x Amps = Watts and there are calculators all over online if you need to back into Amps. Some stuff is reported in watts and other stuff is in amps so you may need to use algebra to convert to what you need or use a calculator.

[zoti]

Just purchased parts to make am aux battery build. Should be here next week. I'll make a thread about the build.

[kguarnotta]

thanks sswesty...

I'm going to come up with a list of things I may want to be powering and how long I may need to power them. That thread is helpful...
_________________
-Kevin
Lincoln, MA

'86 Triple Knob Syncro w/EJ22
'78 Westy
'69 Single Cab
'65 Kombi - EZ-Camper

[truepaul]

Hi all --

I want to ask about battery charger wiring. I guess the core question is, do (most, all ?) battery chargers work with the battery negative pole wired to ground ?

I recently bought an industrial (Iota) battery charger, and started thinking about how to isolate the battery -- I wondered whether both terminals should be isolated. So I called Iota to clarify, and they said yes, disconnect both the + and - (ground) side of the battery prior to powering the charger.

Here's my dilemma: this requirement adds complexity and seems less fail-safe. And maybe this isn't really necessary?

I planned on having a (+) side disconnect switch mounted behind the driver's seat ... now I'm looking at mounting a (+) and (-) disconnect, plus an AC on/off switch for the charger ... and they should be activated in sequence. (Right?) It also is a challenge to wire all this, into an already tight space. (My aux battery is under the sink, so the battery and the distribution wiring is there as well). Yikes !

Anyone with thoughts on this, please chime in !