Dual Battery Help

[jmsj]

Hi There,
I am really struggling with my dual batter setup..
I have installed these so many time before but the NP300 is totally different and I just cant get it to work.

Giving the variable alternator I am trying to run a 25 amp DC-DC charger but where I think the issue is that my earth is really really poor when I earth directly to the chassis?

I am running a 4G wire for the battery to Chassis and when I test the earth I can not even light up a test light?

Has anyone had this issue?
Or has any got a wiring diagram for a dual battery setup (battery in tray)?
Should I join the earths up from the main battery?

Any support would be greatly appreciated.

Cheers

 

[Old.Tony]

I ran both positive and negative cables from the front into the tub for mine. I didn't want to risk a possible poor connection between the tub and the chassis, for instance, becoming a nuisance at some later point. I also only used 8Ga cable, because it is rated for 56A continuous (and came in paired fig8 ) and the voltage drop over 6m is very small under a modest (10A) load, and under higher loads (I've had mine loaded up to 40A, probably closer to 45A) it still performs excellently.

The DC-DC charger is an option we considered as well, although it's not how I'm currently doing things and I'm considering simply upgrading my current setup to a slightly more advanced but technically the same ... I have a PWM solar controller with a 120W solar panel charging the battery and the incoming 12V simply powers an inverter which powers the fridges while driving. Both fridges (Engel 60L as fridge, Stirling 40L as freezer) switch to 240V when available thus unloading the battery, allowing the solar to maintain the battery. I'm upgrading my PWM controller to a MPPT controller and probably will connect a smart charger in the mix as well, so that it will charge the battery at night/poor weather which is needed given how much power I'm asking of the battery.

On the subject of your alternator, there might be some value in testing whether or not the "green wire mod" works and returns your alternator to "dumb" mode which is better for dual battery systems, but since the world is moving to the smart way, we really need to find viable long-term solutions for managing power "the smart way". Although my car has a dumb alternator, I think I prefer my method - but the canopy allows it, and if I was eager enough, I could pop the 120W panel off and put a 220W panel up there and never have to worry again. I don't think we gain a lot of "future" by taking backward steps with the alternator, so I think the path you've chosen is the better way - it may only need that extra earth. What happens when you simply connect batt -ve to the rear with a jumper lead?

 

[jmsj]

Thanks for you reply. I really appreciate it.
The extra earth has almost fixed the problem I think...
It seems to be working fine whilst the car is stationary but when I just got back from the service station the charger was turned off.....hmmm
So I shut down the car and restarted and it fired back up again appearing to work normally.
I couldn't see anything in the booklet that would indicate why this may happen.
any thoughts?
Cheers

 

[happy john]

The earth is nearly always the culprit in any install that has problems. I never have any connections that can fail and run the best cable I can afford direct from the alternator to the charger in a continous run and solder/crimp the terminals. You make no mention of the brand of charger, perhaps that would help with an answer to your last post as there is many new chargers around now.
Cheers

 

[Old.Tony]

It's possible that the charger doesn't like transient on/offs. Easy to test: start the car, check, turn off, check, start, check. I have a charger that spends 2 minutes doing a "refresh" of the battery when it's first turned on, and if it gets interrupted in that time it has to start all over again. Annoying, because a "refresh" in this case is a boost to 15V at 2A for 2 minutes - it's long enough to cause damage to Gel batteries. Thankfully my Optima D31A 75Ah is an AGM, but I have a 100Ah Gel DC battery that I want to be able to use on occasion too. I have an Aldi charger (from about a year ago) that barfs when its input power is switched off and on again. Needs to be manually restarted.

So as John says, tell us what the charger is and hopefully someone's seen it in action and will have a definitive answer!

 

[jmsj]

Thanks Again,
This is the charger I am running:
http://www.supercheapauto.com.au/Pr...attery-Charger-DC-DC-In-Vehicle-20-Amp/374624

 

[jmsj]

Thanks Guys,
I am running a Ridge Ryder 20AMP.
Got it from Supercheap auto.
All wiring is at or above spec also.

 

[happy john]

That's the Super Cheap model, looks like nobody has an answer but I think Tony's suggestion is on the money. You should be seeing 14.4 volts or so when fully charged.

 

[jmsj]

Hi Guys,
I completed the stop and start and start process and the charger performed as expected but when I drive around the block it has turned off?
There are 2 things I am not 100% about.
1. I have run the earth for the 2nd battery to a solid earth near the main batter but not directly to it because when I read some wiring instruction from redarc it was recommended not to do this?
2. The charger is mounted on it's side and not flat. I have read that some charges don't like this.

But my assumption is that the charger wouldn't work at all if the above was a issue?

 

[Old.Tony]

Earth to the battery = one connection on that end of the cable. Earth to chassis then chassis to engine and engine to battery = 3 connections. I'd rather one - less potential for faults.

Chargers are solid state. You could install them upside down with the front panel facing the ugliest Penthouse centrefold ever and it'd still work. Must be something about that charger. Orientation of brake controllers is important, or anything else that measures the vehicle's angle, but you could roll your car and the charger should still work.

Vehicle starts are actually worse than short transient on/off periods - during starting, your battery isn't OFF, it's simply providing a lot of amps and should still be capable of delivering 9-10V during cranking. I wonder if that's confusing the charger? The only way to avoid it is to put a relay in the charger's positive input line (cut the wire, connect one side of the cut to pin 30 and 85 and the other to pin 87). Run a wire from pin 86 into the cabin, to a switch on the dash, and the other side of that switch to a good earth point inside. Whenever the switch is OFF, the relay won't trigger and the charger will be OFF. Turn on the switch and when the ignition is on, the relay closes, giving power to the charger.

 

[happy john]

Well said Tony, that aside I'd take the supercrap charger back and replace it with a Ctek.

 

[Skip91]

Hi all, for those running the Supercheap 20 Amp DC-DC charger. i sat my charger on top of the "hidden fuse panel" which is the box behind main battery with enough slack so it could be moved out of the way if need. below is how i wired it up.

8G + from main battery to charger with 30amp fuse
8G - from same location main battery bolts to the body (basically next to the battery)

8G + from charger to the tub and in to Second Battery, also with a 30 Amp fuse
8G - from Second Battery back out of the tub (same hole as the + came in) down under the car and bolted it to wherecthe factory fuel tank guard is connected to the chassis.
The + & - in the tub are on an Anderson plug to make removing the Second Battery easier.

Have had this in since Xmas and had no Dramas.