redarc isolator question

This has also been on mind,

Do you here a clunk sound every time redarc kicks in?

I disconnect my aux battery every time we are not touring and leave the battery on charge in the shed.

Even with the engine off the aux leads are live!

From my understanding and witnessing, the alternator will charge both at the same time when ever needed, the redarc system just prevents the aux battery drawing from the main battery.

This can be a drain on the stock alternator especially when driving at night charging main and aux batteries and having 6 halogen spotlights in use as well as air-conds and so on. I see my voltage meter on the dash drop big time.

The redarc isolator is just a simple relay, once the voltage reaches a predetermined level, it engages, once below a predetermined level it disengages, this is why they are cheaper than a "smart" battery management system.

Have you considered phoning Redarc and asking them? I am sure they will have the answers you are looking for, and their source is credible. Their number is (08) 8322 4848.

This notion of " fully charged" is a contencious one and trips a lot of people up in a lot of discussions.

All these basic Voltage Sensitive Relays work the same.

They have no ability whatsoever to assess state of charge......they simply switch in when the primary battery voltage rises to a preset point and switch out when the primary battery voltage drops below a certain point......that is pretty well the beginning and the end of it.

The various manufacturers have differing opinions on where those voltage thresholds should be and some offer the ability to change them.....reasons for these voltages being selected is a whole discussion on its own.

The advantage of a VSR over a simple ignition triggered solenoid is that they allow the initial charge to be staged.....If the prinary battery has become discharged the VSR will not switch in till the terminal voltage has reaced a reasonable level and the primary battery has reached a reasonable state of charge.

Most of us our primary battery does not get significantly discharged so it comes up to voltage fairly quickly, so we don't see a significant delay in the VSR connecting the second battery.

Some VSRs employ stratergies to limit surge currents most do not.....getting solid information on this is hard.

cheers

QUOTE:ok so thier advertising blurb says the redarc wont connect to the aux until the main is fully charged"

Where does Redarc say this?..... I have never seen it in there marketing material and I think someone made it up outside of Redarc!

They are pretty honest on how the SBI series work and it has always been said in there marketing hype it is an isolator that disconnects the start battery from the aux battery.

No where in their instructions do they say it will charge the start battery first and then the aux battery.

The Redarc literature does not say "fully charged". It says...... "Put simply, once the start battery is charged by the alternator, the Smart Start SBI will connect an auxiliary battery to the charger circuit."

With respect, you may not see the subtlety but there is a difference between "fully charged" and "is charged". The standard Redarc SBI connects at 13.2 volts and a battery with its terminal voltage whilst on charge at 13.2v would be at a reasonable state of charge. Certainly with its terminal voltage at 13.2 it is at little over a volt below the alternator nominal output voltage of 14 point something so the current into the start battery would probably be of the order of 10A. At this point it is quite reasonable to connect the charging load of the auxiliary battery without excessively loading the alternator. It does not need to determine the resting voltage of the start battery.

If on the other hand, the start battery was at a low state of charge, its terminal voltage would stay below the Redarc cut-in of 13.2v and so prohibit connection of the auxiliary battery until the battery SOC had risen sufficiently. In practice this would rarely occur in a well maintained system as the start battery would not fall below 90% SOC and require little recharge energy. The large 'capacity' of a start battery is to ensure adequate available energy during cranking which consumes only about 1.0Ah during a normal start.
A simple isolator solenoid, enabled by the ignition circuit, will satisfactorily perform as an isolator but will not reserve the alternator to priority charge the start battery on the occasion when the start battery may be of low SOC. Furthermore, if winching from the start battery, the simple ignition-enabled isolator will enable heavy winching current to be drawn also from the auxiliary battery. This is OK if the aux circuit is arranged for that purpose but can otherwise cause overload of the aux main cable and fuses.

Redarc do not make outlandish claims in their literature and they publish a great deal of technical information unlike most other manufacturers/suppliers of similar products.
Furthermore, as has been said above, Redarc staff are highly knowledgeable and very willing to discuss and advise on their products and application over the phone.

Not sure why this is so hard. Leigh has finally said what really happens above.

Jump start - Alternator kicks over and can supply up to say 100amps. Battery can only accept say 30 amps if its in good nick but flat. So the regulated voltage still rises quickly above the 13.2V sensing level for the Redarc and the aux gets charged as well. Nothing wrong with all that - that's the way it should be.

If the Redarc waited until the cranking battery was fully charged, it would have nothing going to the aux for the whole day.

any way.....

looks like the main cause of my trouble is a stuffed battery - at least I hope thats all it is

Ive been leaving it for 3 weeks between driving it

first time i did this it fired up no worries
second time it just turned over and I was able to jump start it using the second battery (I dont have the redarc set up to start off the aux)

3rd time it was dead as a doornail - just operating the dash lights

I jump started it - which if anyone has jump statarted a dead flat cruiser with light jumper leads would know isnt easy as requires leaving the leads atached for quit awhile before being able to start

and took it for a reasnable drive - Now I know a half hour drive wont charge a battery but should put enough in.
I pulled up and it restarted ok. Next day (24hrs later) I jumped in to drive it some more and it was dead flat again
I dont run auxillery stuff off the main except the spotlights and nothing was left on