What battery for AUX

[KraftyPg]

Yeah but my house has 240V and when I park in the garage I don't want stray current hitting the ute so I'm going to use some 700Amp 240V fuses with 7 strands on shielded cable from SCA just to be sure.

 

[Krankin]

A 3 inch nail does the trick.

 

[KraftyPg]

But is it good for 700Amps? I've only seen 650Amp nails and when we are talking current more on the safe side is better.

 

[Krankin]

Krafty...just dont put a fuse/cb in that is rated higher than the cable you connect it to.

 

[KraftyPg]

Hmmm ok

Well the LED lights I have in the tub only draw 3/4 of 4/5 of FA so I'll use the 3amp fuse from there and plug it into the isolator and chuck the 3 inch nail.

 

[Krankin]

But is it good for 700Amps? I've only seen 650Amp nails and when we are talking current more on the safe side is better.

they got those 9 inch sleeper spikes down at bunnings ya knows...gal plated too so they wont rust on ya after dem water crossins ya does on da farms mate

 

[KraftyPg]

Ooooohhh you is a thinker my boy!

100 Million points for you...you can cash those points in at the Nav Asia gift shop, but keep it hush hush all everyone will want free points.

 

[Krankin]

Ahhhh, onya matey, mum will be delighted with da free pointy thingys.
Us country folks gotta stick twogether ay mate..

 

[KraftyPg]

Just don't stick me with that 9 inch nail....lets save that for dem weird city dwellers.

 

[Rich64]

Just 1 tip that I gleaned from my investigations into battery's when I was setting up my second battery, and I haven't seen it mentioned here before Don't mix types of batteries, i.e. flodded, gel, AGM etc, unless you have a charger as a battery controller. each of these different types of battery have different charging requirements, so if you want to go AGM for your second battery, then ideally you should go AGM as your main battery too. The ultimate system is to install a dc-dc charger to manage the charging of the second battery, this also eliminates the need to run massive cable to your second battery, and also cures the back feed current issue should your start battery go flat and the ignition is turned on. I hope I've explained it ok.

 

[Old.Tony]

+1 for Rich's advice.

The DC-DC charger will boost the voltage off a long cable run and provide a nice voltage level to the battery being charged without allowing the aux battery to back-feed to the primary.

You can get AGM SLI batteries but with a DC-DC charger or the inverter-normal charger method that I use you can have different battery types without any worry at all.

Most important: fuses. If you're directly connecting cable to a battery and running it somewhere, the first thing that goes in before you "run it somewhere" is a fuse. That's to protect the battery, the cable AND prevent fires. A lead acid battery is an enormous powerhouse and if you run a length of cable that joins the battery terminals together, you produce a heater/welder that can start fires before you can blink.

 

[FatBoy89]

With the dc-dc charger I won't need an isolator anymore right? So if my starting battery dies I need to jump out an connect my batteries with jumper leads?

 

[KraftyPg]

Buy the right isolator and you wont need to connect the two batteries you'll just need to push a button.

 

[FatBoy89]

I know that part. I got a start smart. But now this whole dc-dx charger thing is making me think. Get extra time out of my aux batt. But if I'm getting a 105ah batt I should be alright...

 

[KraftyPg]

A dc-dc charger is a waste of money in my opinion but some people like that sort of thing.

 

[FatBoy89]

I'm not one to waste money. But the idea actually sounds right.
I'll get the battery first, Use the Redarc, hook everything up. And see how that deep cycle battery goes.

 

[KraftyPg]

The problem with most of these things is they sound right, (well expect for those that just sound wrong) but it doesn't always mean they are right.

 

[Old.Tony]

The DC-DC charger SHOULD (see note) isolate the primary from the secondary. There may be a small amount of current loss depending on how the charger works. Generally solid state technology (that is, using a transistor to switch the power supply on or off) will draw a little power, whereas a relay (which is normally open when power is disconnected) totally isolates things at zero power cost. Even if it is solid state, the power drain SHOULD be so small it's not worth worrying about.

Note: not all circuits are equal. As an example, the concept of an inverter generally isolates the input from the output - an electron propagating along the wire in the input side has no physical path to reach the output side. However, to save production costs, they developed an inverter circuit where the negative input is physically and electrically the same conductor as the neutral output and only the positive rail is oscillated at 50Hz then shaped to form the AC wave around the negative line. This is dangerous and Jaycar have replaced all of their inverter lines with 'electrically isolated' models to reduce this danger. There's a chance that a DC-DC charger may have similar characteristics and allow current to flow in the reverse direction under certain circumstances.

 

[KraftyPg]

Anyway pay no attention to me I disagree with about 50% of the hydrogen in tyres theories on the internet, 75% of the Aux battery theories on the internet, and 100% of all the oil in diesel theories on the internet. Internet theories only need one person to voice them and 3 to agree and suddenly they are internet fact, that and I just wanted to follow Dave's lead and end the night on 9000 posts.

 

[FatBoy89]

The DC-DC charger SHOULD (see note) isolate the primary from the secondary. There may be a small amount of current loss depending on how the charger works. Generally solid state technology (that is, using a transistor to switch the power supply on or off) will draw a little power, whereas a relay (which is normally open when power is disconnected) totally isolates things at zero power cost. Even if it is solid state, the power drain SHOULD be so small it's not worth worrying about.

Note: not all circuits are equal. As an example, the concept of an inverter generally isolates the input from the output - an electron propagating along the wire in the input side has no physical path to reach the output side. However, to save production costs, they developed an inverter circuit where the negative input is physically and electrically the same conductor as the neutral output and only the positive rail is oscillated at 50Hz then shaped to form the AC wave around the negative line. This is dangerous and Jaycar have replaced all of their inverter lines with 'electrically isolated' models to reduce this danger. There's a chance that a DC-DC charger may have similar characteristics and allow current to flow in the reverse direction under certain circumstances.

Ummm... What?