Here is one for traxide and other gurus

[jx2mad]

My L322 has a 50A cct to the rear of the car. I have had a tow connector fitted for my van. However sometimes I will need to run my Waeco fridge in the back of the car. I know that I can plug it into the power outlet in the rear but I feel I should run it off a second battery. I have a 110A deep cycle battery I can use but I need some advice in how to connect this up. I need to be able to charge this battery but it must be isolated from the main starting battery. I do not want to overload the 50A supply and cause problems. My auto elec friend says I should not use this cct but install a dedicated supply to the rear (almost impossible), However the 50A supply is electrically the same point as the positive terminal of the starting battery so I don't see a problem. Your thoughts and suggestions please. Jim

[Blknight.aus]

grab a disco1 or RRC VSR, hook it up to the 50a circuit, hook a 100A relay to switch the 50A cuircut supply and control that with the output leg of the VSR, hook up your load to the output of the relay.

IF you're going to use it to charge batteries I strongly suggest that you install some form of current regulation. A 10 amp self resetting thermal type circuit breaker wired across a 60w headlight bulb will provide up to about 11amps constant charge and about 15A peak. Wire that between the battery you're going to charge and the solenoid.

While the engine is running the relay will close and connect the aux battery and the load to the main battery. IF the aux battery is drawing too much current the circuit breaker will open and the headlight bulb will carry the current providing a maximum of 5 amps of current flow to keep topping up the battery untill the circuit breaker closes again then the cycle repeats untill the battery is sufficiently charged to not exceed the nominal amps of the circuit breaker.

When the engine is off the relay is open Isolating the main batttery from the load/AUX battery. The AUX battery provides up to 10a of power through its circuit breaker to the load to keep things running.

ITs a prudent idea to install a 40A fuseable link or fuse between the battery and the regulator just in case the circuit breaker welds shut or you short the wiring.

[drivesafe]

Hi Jim, you have me as pre the “cct” not sure what that means.

Hi Dave, while your 60w light globe is a great short circuit protection and indicator, it will not pass 5 amps between the alternator and a flat battery.

The 5 amps through a 60 watts globe will only occur if there is a 12v difference across the globe.

With an alternator voltage of 14v and a low battery voltage of say 11.5v, you only have a voltage difference of 2.5v and you would be lucky to have a current of 1 amp through the globe.

I use to design and manufacture home security systems and I used the same set up to charge and maintain the alarm’s back up battery and at best it only trickle charged a low battery off the 13.8v supply voltage.

Plus, a low 110 Ah battery could easily pull up to 40 amps so a 30 amp auto resetting circuit breaker on a dedicated power supply cable is really the only way to get the battery charged in a reasonable time frame and wiring an L322 RR is a nightmare.

[jx2mad]

Hi Dave. What is a VSR?
Hi Drivesafe. cct is short for circuit.I worked in telecommunications for 34 years so sorry for telespeak. I gather that the only way is to run a dedicated CIRCUIT from the main battery via an isolator solenoid. Or else run fridge off main battery and carry a fully charged jumper battery? Jim

[drivesafe]

Hi again Jim, VSR stands for Voltage Sensing Relay and is another name for the average dual battery isolator.

I should have picked up on the CCT.

If your thinking of using the power cable running to the rear of the L322 this will be a lot easier than running a dedicated power cable but it will be a bit light on power if your battery is low. Otherwise this is a better option.

[harlie]

The circuit that feeds the rear fuse box is fused at the front by a 100amp fuse – not 50.

My setup (powered from the rear fuse box) has now completed 2 trips away without any issues. Only issue I would expect from now on is my 40 amp fuse may be a little light when the battery is very low, I can replace it with a 50...

After reading a rather heated thread I did some reading. The author quoted in the thread states that “3 stage charging” is needed, the same author also published “Table 1 gives a rough guide (of charge state), but only after batteries have rested for at least 12-hours”. In Table1 he states that a well rested battery with a voltage of 12.75 is considered 100% charged.

We returned home on Sunday night – the camper is parked and isolator turned off. On Thursday night I checked the battery on the camper. The multimeter shows 12.82V and the built-in digital voltmeter on the elec panel shows 12.8V. So I take this to mean that a charging source drawn from the rear fuse box work fine - Or is the 12.75V theory on a rested battery also crap?

Seems the “3 stage” argument is indeed advertising hype - might even seem that the author hasn't actually tested his theories in a real world application.

To answer your Q – Install a VSR (get one from Drivesafe) as per my instructions in another thread. Make sure the line to the Van battery also has a fuse/breaker as close to the Van’s battery as possible - I used a 70amp manual breaker that can be used as an isolator as well.

[Blknight.aus]

Hi Jim, you have me as pre the “cct” not sure what that means.

Hi Dave, while your 60w light globe is a great short circuit protection and indicator, it will not pass 5 amps between the alternator and a flat battery.

The 5 amps through a 60 watts globe will only occur if there is a 12v difference across the globe.

With an alternator voltage of 14v and a low battery voltage of say 11.5v, you only have a voltage difference of 2.5v and you would be lucky to have a current of 1 amp through the globe.

I use to design and manufacture home security systems and I used the same set up to charge and maintain the alarm’s back up battery and at best it only trickle charged a low battery off the 13.8v supply voltage.

Plus, a low 110 Ah battery could easily pull up to 40 amps so a 30 amp auto resetting circuit breaker on a dedicated power supply cable is really the only way to get the battery charged in a reasonable time frame and wiring an L322 RR is a nightmare.

the globe isnt there to take the full load of the charging system but to buffer the switching of the self resetting circuit and to provide a limited topping up current to the battery while the CB is resetting This circuit with the 10A self resetting isnt intended to permit for really fast charging of dead flat batteries (I assume that anyone with enough cash to buy a flashy car will have gear with low voltage cutouts in it that would stop you from getting down to low on voltage and needing much more than a 10A charging rate to top up the battery over a days drive). I also use the 10A breaker because most of the electrical systems that get wired down to the back of cars cant really deal with much more than that. on a 50A circuit, allowing a 15A headroom for the load, you could easily run a 30A circuit breaker with a 150W light providing your wiring and fusing was up to it.

I was never any good at verbal descriptions of electrical circuits. so heres an attachment
34899

[drivesafe]

We returned home on Sunday night - the camper is parked and isolator turned off. On Thursday night I checked the battery on the camper. The multimeter shows 12.82V and the built-in digital voltmeter on the elec panel shows 12.8V. So I take this to mean that a charging source drawn from the rear fuse box work fine - Or is the 12.75V theory on a rested battery also crap?

The charging source drawn from the rear fuse box DOES work fine but rested battery voltages are just too unreliable to be of any real use in automotive situations.

In your case if you had connected any form of load to your battery, the voltage would have settled back to around 12.7v depending on the load size.

They are fine for RAPS ( Remote Area Power Supplies ) and UPS ( Uninterruptible Power Supplies ) where batteries can sit around for days or weeks at a time in a NO LOAD - NO CHARGE situation.

In Rv use it is vary rare for batteries to sit for more than a few hours without some form of activity and so OPEN CIRCUIT voltage monitoring is useless.

So Yes, Rested Battery voltage reading are ( not so crap ) just useless.

[jx2mad]

The only way I could fit two batteries under the bonnet would be to fit one of those dual batteries (2 in 1). Any thoughts on these? Jim

[drivesafe]

Hi Jim, as I have just sold my D4, I now have to set up my L322 07 RR and after ruling out the use of the power cable when I wired up my L322 03 RR and taking 7 hours just to run the cable from the cranking battery to the battery compartment in the rear of the RR, I have no intentions of doing that again.

There is a potential problem with using this cable in the back of the RR in that because it is so long, conventional isolators will oscillate if the auxiliary battery is low, because a low battery will cause a fair bit of voltage drop.

My isolator is unaffected by this potential problem so I’m going to fit the isolator in the rear compartment and have a 50 amp Anderson plug on the end of a short length of twin cable and then I can carry a battery, in a plastic battery box, in the rear cargo area when ever I need the accessories powered up for periods of time while the motor is off.

By the way, you can only fit something like a 55 Ah battery in the existing battery compartment in the rear of the RR, and this is why I’m going for a battery in a plastic battery box.

The plastic battery box means I can use a 100+ Ah battery plus if a jump start is needed, I can carry the battery to the front.

[jx2mad]

Thanks Drivesafe. Now all I have to do is to save up for one of your units. I was thinking along the same lines as you with my second battery in a removable box. Jim

[33chinacars]

Hi Drivesafe

Was there a reason that you didn't run extra power lead in you L322 underneath the car . Would save pulling car to bits to fit lead. I'm think of putting a second battery in back cubby hole for fridge and running a seprate lead for anderson plug to caravan. You help grately appreciated as I'm hopless with electric's

Gary

[Blknight.aus]

my usual reason for not running underneath is the potential for damage to the cable..

I will route through chassis though with sufficiently protected cable.

[drivesafe]

Was there a reason that you didn't run extra power lead in you L322 underneath the car

Hi Gary, as Dave posted, in my opinion it's just to risky to run cable under any of my vehicles as I always take them off road.

In your case, with wanting to have an Anderson plug at the rear for powering a caravan or camper trailer, you will need to run the cable through the RR.

Best of luck and if I can help please don't hesitate to ask.

[tebone]

Thanks Drivesafe. Now all I have to do is to save up for one of your units. I was thinking along the same lines as you with my second battery in a removable box. Jim

Hi jx2mad,
i have a 02 l322, i have a anderson plug at the rear which is wired to the main rear power supply cable near the 50 amp fuses. I also have a voltage relay wired to the same area which supplies my removable battery box. I run a fridge/freezer in the back which is pushed back against the rear seats. What this creates is a triange space which my 105amp/hr battery box fits into this space. I also have anderson plugs on every connection so I can plug other things into it eg: solar panels to charge aux battery when camping in one area for a while with my fridge running off aux battery. I have had no problems with this set up. The only thing the voltage relay needs to have a good earth.

Battery $285 Gel 105amp/hr
Votage relay 100amp $80
Battery Box $20

Regards Paul

[drivesafe]

Hi tebone, with the first of the L322 RR, the operating voltage is a constant 14.3v, so voltage drop is not a major problem.

I don't know when the newer variable operating voltage began, I suspect at about the same time or just before the first of D3s came on the market.

From that point on, and low battery will mean the voltage drop at the rear will be such that it will cause problems will ordinary isolators.