Redarc battery isolator question

Hi Jim,
Thats right, turn the head lights on for a couple of seconds and you'll hear it click, turn the lights off, and the red light will stay off.
I only found out about this myself the other day.

Lex.
This a very good solution and I wish I had thought of it before putting in a ignition slave relay.
Not because of the cost of the relay, but due to the differential between the drop out and pull in voltages of the Redarc, your method will achieve a lot less drain on the starter battery.
Regards Dennis

Mine stays on for hours, even with the fridge running, if I don't knock it out

So when you switch the ignition off- the batterys stay in closed-circuit (ie connected) ??
Isn't that against the idea of a battery controller isolator??

Maybe your voltage shut off is set too low. Mine was set at 12.6- 12.7v. I vaguely remember reading that you can adjust it somewhere.

Cheers
Dave

Hi Signman,
Yes they stay together untill the voltage between them drops to the predetimined level, in my case 12.6 -12.7v. After the vehicle is running the batts are around the 13v+ mark and it draws from both untill you hit the nominated voltage. Then it will isolate them and the accessories will only draw from the aux battery leaving the main at the voltage nominated earlier.

Does that make sense?

Cheers
Dave

I should correct my comment re "could see the main battery being flattened in some circumstances, if I forgot about it."

It will not flatten the main battery but it will pull the best off the top of the charge in the main and as my vehicle is a turbo 1hdft I believe that they were putting 2 batteries in some models due to the demands of starting the engine, I presume in cold conditions.
Regards,Bruce.

It's called "surface charge".

Despite a full battery being around 12.7V, after charging it may be at 13.7V until the surface charge dissipates.
This occurs (say) overnight on an open circuit battery (no load; not connected) or after a few to several minutes with load (ignition, headlights, etc).

Hence the redarc is not a problem. When the battery reaches its "normal" full voltage, the redarc will switch off.

Normally such voltage sensing isolators are set higher than battery-full voltages eg - low to mid 13V. It is not surprising redarc increased their set voltage - why discharge a battery to ~12.5V (ie, typically about 10% discharged)?

The problem setting the voltage too high is when the alternator is unable to supply the load and dips below the set voltage - the isolator then separates the batteries. Is that really what you want in that situation.
But voltage sensing isolators (should) have timing delays to ride through short-term dips as well as limit cycling in some situations. Typical delays are 10-30 seconds for both on & off, though some only have off delays.

Now there is a simple solution to all this.
And certainly those that are using an ignition switch(ed relay) to connect their batteries should be using that system - in most vehicles it merely involves the reconnection of one wire.
But rather than repeat other posts.....

Come on ChipPunk - don't leave me in limbo. Please explain the bit about reconnecting one wire. I haven't seen other posts with that mentioned. Yes I did search and found quite a few Redarc related posts but not one discussing what you've mentioned about the wire.

With my redarc setup, Instead of just allowing the earth wire to go directly to earth, via the screw holding the solenoid in most cases.

I cut the wire, and routed the wire into the cab, where it goes thru a on off switch on the dash, and then back to earth.

What this does is allow me to manually turn off the solenoid if I want to
Say if I dont want it to operate after turning off the vehicle, ie allow the fridge to gobble up the surface charge instead of the solenoid doing that.

I also made up a short piece of wire left over from running the 8gauage to the back of the vehicle for the fridge/ lights etc with 2 clips on it, that I can bridge the top of the solenoids nuts manually, and not have to use the 1 amp or so it needs to connect, good for charging both batts when on solar, or getting a few extra amp hrs from the batteries for the fridge.

hope this helps.

Trains

LOL! I'm somewhat cautious after the recent closing remarks for Dual Circuit 2x Aux Batteries where I merely mentioned the method..... (Conclusion - do not value-add info else or do not respond to distractors - wink.)

But since in this case you are the OP....

If you have a typical charge lamp - or rather, an "SL" type alternator/regulator (detail below), then instead of connecting a relay from a switch or Ignition or Accessories position, you connect it to the charge-Lamp's "L" circuit.
Hence when the vehicle is charging, the isolating relay is energised and connects the main battery to whatever (aux battery, fridge, PC etc).

If you know how to add a $0.20 diode, it is easy to add manual triggers with low-voltage cutouts, latching outputs etc.


Questions? I'll respond only to the OP unless it's simple or a point of correction, or if sanctioned by respected members.
This method is someone else's (from overseas forums).


The following is merely extra info and background. Stop here if it's too much to handle..... And cheers!

The "L" method does what most isolators attempt to do - namely determine when the system is charging and then connect the auxiliary batteries etc.
But this uses the "smarts" (sic) of the alternator. It hence overcomes the need for on or off delays, and complications due to typical voltage fluctuations or cyclic switching.

The saving of all that "smarts" means it only costs a relay. And you can choose its size.
The alternator - actually its regulator - need only be capable of energising the relay. Most are capable except for newer & "DP" type alternators.

If you want to add more circuits (eg - batteries) - just add more relays.
BUT the extra relays should be driven from the first relay's output, as should any high-current relays. (Typical automotive relays of 60-Ohms or higher (<250mA) should be fine. MOSFETs can be used if relay currents are too high, or replace the relay(s) all together. With 60A MOSFETS available for under $3, why not? Or make it a "hybrid"... LOL.)


An "S-L" type alternator refers to alternators with regulators that have a charge-Lamp output. This is the "L" or "Lamp" circuit, often called "D+" in single-wire alternators.
Note that although the alternator may require a charge lamp (or other parallel paths/lamps) to ensure charging, the relay circuit does not.
The "S" refers to its "Sense" wire which is not included externally in single wire alternators but is irrelevant to this discussion. (Phew! The complications of describing 2-wire types with Ig & L, or 3 wire with Ig, S & L etc as opposed to "true" 2-wire S&Ls like many older Bosch alternators....!)

Newer EMS-interactive alternators include the DP types. If there is an accessible charge lamp terminal in the dash or loom etc, then they are similar (albeit using a MOSFET interface - whether inverting or not). But let's KIS for now.

Why is it- if you get a product to do a particular job,
you have to modify it, add extra wire, relays and widgets to make it do what you want it to do ??
I think I'll stick with the good old proven solenoid unit. When it's on/ it's on- and when it's off/ it's off !!!!

ChipPunk
Thanks for that reply but in all honesty I'm an electrical dummy so I understood bugger all of that (not being rude - I'm seriously challenged with vehicle electrics). You obviously know your stuff in that field. I think I'll just ignore that little red light or, if I remember, I'll turn the lights. Those 2 I can manage!

No problems!
I gave the descriptive version.

It is the same as an ignition-contolled or switched relay (isolator).
But instead of connecting the relay's #86 to/from the ignition or a switch, it connects the the chargeLamp circuit.

(If you know where that alternator/regulator is, it is easier than wiring to the ignition or a switch.)


Signman - I rarely hear of people buying relays and then complaining that they have to wire it up. Those types usually get electrical people to do the job.