Thread: Here is one for traxide and other gurus

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.

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.

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

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.

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.

Originally Posted by 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.

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
charge regulator.jpg

Originally Posted by harlie

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.

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