Aux battery for beginners

[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 !

[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

[zoti]

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

[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.

[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

[truepaul]

[Vanagon Nut]

[metropoj]

[crazyvwvanman]

There is an issue with or two your diagram.
The control wire to the 120-902 should NOT be from 'ignition on'.
It should be from a source that is 'off' during starting but on when key on or engine running.
This is easy to do.
The fuse could be 5 amp.
Also, the 120-902 needs a small gauge ground wire, not shown.

The starter motor stud is nearly directly connected to the starting battery so using it instead of the battery is fine, even preferred in this case.

Mark

[metropoj]

Beginner here raising his hand too !

I also spent a lot of time perusing through SO many threads

I hope this isn't seen as a hijack ( not intended ) but thought maybe my questions may help the OP as well ?

I got a TF49 new so cheap that I couldn't say no. NOW the real money is in the system to run it !

I took lots of info from several threads and decided to try a diagram with a Flooded Group 31 under rear bench, a Shore Charger > 6 AMP, a White Rogers Relay 120-902 Isolator, some fuses here and there and wire the fridge direct to the house battery for now ( will consider the fuse panel later on ). Will use wire feed from the old Westy Relay under drivers seat or wire into fuse panel for ignition on trigger for White Rogers 120-902 Isolator

I see many run an additional wire from the Isolator to the Start battery. Why is that ?

If I don't want to combine the 2 batteries to the Isolator. Is that ok ?

I thought my 120A Alt will charge both system separately and without the need to "combine them" so that is what I don't get. Did I get that wrong ?

I used Visio and some incorrect drawing shapes to represent different things ... can't be any worse than an outboard motor shape, lol !

Comments and hope it helps out the OP too.

_________________
John.
86 TiiCo powered Westy.

[dabaron]

[zoti]

[SSWesty]

For the stock fridge propane will get you about 2 weeks of runtime depending on the amount of cooking you do with the factory stove. To gut it out with solar and batteries it would seem like 400 watts of solar might keep up if you have sun. Stock fridge on DC with the engine off is the wrong tool for the job.

[zoti]

So how would you run a fridge for a longer period of time?

[SSWesty]

[izzydog]

Ok, this is good start.

You don't really need to charge the start battery with solar. If you are worried about your start battery being charged enough to start (in case there is a mystery drain on it) you can always jump your start battery with your aux battery. Done it a few times myself.

A 100AH lead acid battery is really only 50AH of usable battery if you only allow a 50% discharge to your aux battery. 50AH might be enough for a day or two depending on how much sun is shining on your panels. I have two 100W panels and a 100AH lithium battery. As long as I can get a good, long day of sun, I can run my fridge and lights for many days. Lithium batteries are expensive up front, but pay for themselves in the long run when you consider replacing lead acid batteries every 3 years or so and that's if you've taken care of them and not discharged them too deeply.

My panels are the thin, flexy type that I store in the upper bunk when traveling. I have a 50ft cord exiting the license plate door (via Anderson plugs) that allows me to put the panels in the sun and the van in the shade. Mounting them to the van means you have to park in the sun. Not a great idea out here in CA when temps get near 100F.

I still have an inverter in a box from 10 years ago that I've never used. Most everything I have runs off 12V these days so no need for the inverter.

My solar controller and battery monitor are made by Victron and, via bluetooth, allow me to monitor what's going on with AH left in the battery and watts coming in via the solar panels. These are good things to know in the middle of nowhere and you are not sure what's left in your system. Having a battery monitoring system is another plus for lithium batteries.

If I were you, I would buy components that could be used with a lithium battery and when you are ready to jump from lead acid to lithium, you'll already have what you need. This is the bluetooth solar controller I use: https://www.amazon.com/gp/product/B075NPQHQK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Hope that helps...

[Vanagon Nut]

[zoti]

I know ow to install things but not familiar enough with solar and correct wiring setup.

Here's what I would like to do and maybe someone can help.

As far as consumption I plan to run:

- 12V fridge
- Maxxair fan
- Charge cellphone , iPad etc. (no computers)
- Led lights
- 110v inverter (optional)

I was planing on a 100W panel and 100AH battery. My trips will be a few days long at most. I'm thinking of keeping the option of adding another 100AH battery and and optional extra 100W folding panel that I can set up next to the camper if I need the extra charge.

I would like the solar to be able to charge both the aux and main car battery and same with the alternator.

Is there a good schematic I can work of and a good list of parts I will need?

Would this kit e a good place to start? (I'm not looking to spend thousands on a setup).

https://www.amazon.com/ECO-WORTHY-Controller-Inver...amp;sr=1-7

[dabaron]

[izzydog]

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