Dual Battery

[EzDingo]

If you leave the cut-out voltage set below 12.7v all the time, you will end up shorten the operating life span of your cranking battery.

Interesting and perhaps a thread of its own but can you explain why? As I leave mine at 12.6 mostly (even when not needed) I want to understand the logic behind this.

[drivesafe]

Hi again EzDingo, with a cut-out setting of 12.6v, you will do little if any harm to your cranking battery as you will be drawing less than 5% off the capacity of your cranking battery “IF” your cranking battery is in a good condition and was in a fully charged state.

5% extra ( 5Ah if the you have a 100Ah cranking battery ) would be the very maximum additional power made available to your fridge, and this does not take into account the lose of power through the inefficiency of a DC/DC device.

So you will gain, at the very best, just an additional hour and a halfs operation of your fridge, and certainly nothing remotely close to an extra days operation.

If your were to set the Cut-Out voltage lower than 12.6v, then your cranking battery would be continually discharged down to that lower level every time you turned of your motor.

All batteries have a total energy throughput over the life span of a battery.

The more energy you draw through the battery, the sooner it will die.

If you leave the setting low while you are NOT using the fridge, the DC/DC device will still draw power from your cranking battery while the motor is off, and even at a lower current draw when the auxiliary battery is fully charged, you will still literally ware your cranking battery out for no real gain.

While inefficient, having the lower Cut-Out level while camping, it is still a way of increasing your fridge run time while camping, but at all other times, it would be far better for the longevity of your cranking battery, if you set the Cut-Out leave back up above 12.7v when not camping.

[EzDingo]

Thanks for the explanation... I think I follow what you mean... There are so many variable and inconsistent information its hard to know what's what unless your an expert... All I know is:

- My batteries are both dual purpose AGM styles.
- Day to day in normal life they sit at about 12.7-12.8
- VSR cut off is set to 12.6 for no reason other than that's my common setting for single overnight style touring stops when travelling. On a 18-24hr touring stop with fridge, lights and maybe a laptop/phone recharge it ends up the next day I am still always over 12.6 and VSR has not cut out yet... 2 days though and it will go to aux only)
- In everyday life (just starting the car and doing local trips) it never drops below 12.6 or cuts out.
- A search for AGM battery voltage state of charge comes up with various figures ranging from 12.6 being about 90% to 12.6 being 75%... ???!!!

In summary whenever I have randomly checked both batteries of a morning when not travelling they are always 12.7-12.8. I am assuming this to be healthy and my set-up nothing to worry about. Both batteries individually are getting drained less when starting the car and both are recharging once on the go... Alternatively it could be one battery is being drained more by starting the car and both are being charged while driving...

[drivesafe]

Hi again EzDingo, do you have an INTERVOLT DC/DC unit fitted, or are you using a conventional VSR?

The reason I ask is because they will cause different types of discharging of the cranking.

[EzDingo]

do you have an INTERVOLT DC/DC unit fitted, or are you using a conventional VSR?

No its not the DC/DC unit I posted a link to... I have the same mobs conventional VSR unit being the EBI Pro.

[Greg Grey Grumbly]

Dual Battery System - Home of 12 Volt Kit

Having now had the new Paj for three days, I'm wanting to get on with a decision on the dual battery setup. I've read up on the pros and cons of a VSR vs DCDC Charger system and although a VSR may be a simpler install in some respects, the DCDC system seems to me to the way to go, mainly because it would have the least effect on warranty with not fiddling with the variable output alternator. As I have the 5 seater version a cargo area install is not out of the question but I'd probably like to stick with the under bonnet system and leave the cargo area free for all the other stuff. A fridge slide will be goiing in though, going up to 4WD Supacentre next week to have a look at there slide.

The system I'm looking at is the Home of 12 Volt 85 AmpHr (http://homeof12volt.com.au/product/4003/) which seems very close to what I'm after, to run the Bushman fridge and power up the caravan DCDC charger while travelling throught the rear anderson plug.

The $999 system comprises:

FULLRIVER 12V 85AH AGM BATTERY
PROJECTA IDC25 CHARGER
BATTERY TRAY
ACCESSORY CONTROL BOX plus
6MTR 6MM TWIN CABLE 8MM TWIN CABLE
YELLOW RING TERMINAL

The accessory control box is really not needed as the Bushman just wants a cargo area Anderson plug and the caravan connects to the towbar Anderson plug, both powered up from the second battery. Has anyone installed one of these kits and if so thoughts on the install and performace.

[Ian H]

All ok except....the van should run off the main battery and not the aux battery. You say it has its own charger so it has to bypass the charger in the car.

You'll get advice to the contrary in here as we've had this discussion recently but be assured, a caravan is always best hooked up to the main battery. Check any caravan forum or check the Redarc web site where you'll find wiring diagrams for that set up.

As for the battery, I've got an 85ah Exide under the hood as the aux and it runs the fridge fine. Just needs to be topped up with solar or connected to another source if you aren't moving around. My fridge runs as a freezer most times so it draws a lot more than if it was just set as a fridg so I've got a 150w set of panels plugged in to an Anderson plug on the front bumper to keep it topped up

[Greg Grey Grumbly]

Dual Battery System - Home of 12 Volt Kit

Thanks for that advice Ian, which I'll follow.



I haven't closely examined the caravan end yet but it has its own 240 VAC charger but on reflection, I'm not sure if it incorporates a DCDc charger, probably not now that I'm thinking about it.



I'll post an after install report once its all finalised.



Cheers


Greg

[Ian H]

Ok, it's a normal set up and there's no DC charger in the caravan. Same as my caravan with its one battery and Anderson lead direct to the starter battery on the tug. But our Tvan has 2 batteries and it has its own Redarc charger because it's off grid a lot more than the caravan and relies more heavily on 12v power. The fridge for example, is only 12v so that's the main draw. Even in that case, the Anderson runs off the tug starter battery too.
All the 240v charger does is charge the battery when you are plugged in at a park, so you can run your 12v equipment like the lights and water pump as much as you like without flattening the battery.

[Greg Grey Grumbly]

More Home of 12 V Theories

Well after more reading (as I want to get this as right) I'm now thinking that a simple continuous (not VSR) solenoid with a battery box in the rear cargo area is my best solution for a dual battery install in my 5 seat PS. Also, I keep looking at the limited space for engine compartment fitment and I'm thinking the cargo area is a better option. My old NT was tight but the PS is really snug.

Supporting this, I came across an interesting article (search on: dc_chargers_and_the_alternatives_-_vehicle_charging.pdf and the Home of 12v article appears).

This argued that DC DC chargers are not necessarily the best way to go even for 'Smart" alternators. It argues that if the Main and Aux batteries are connected in parallel through an ignition activated, Continuous Solenoid, then both batteries will receive full alternator output until until both are fully charged which makes sense. When the ignition is off, the Aux battery is isolated from the main.

Pros:

• simpler system install and less complexity by removing the DCDC charger
• Aux deep cycle battery is removed from the hostile engine bay heat/fumes
• this should result in much faster charging of the Aux battery compared to DCDC
• much lower cost

Cons:

• a heavier cable is required to run back to the cargo area battery box
• the available battery boxes seem flimsy, the battery must be firmly secured if it is to not become a missile in event of accident
• I'm not sure of the effect on the individual battery life i.e. on starting the nearly fully charged main is connected with a discharged Aux - what is the effect on either battery
• if one battery suffers a shorting failure what is the effect on the other

These are most likely not new questions but I'd appreciate the thoughts of those more knowledgeable on matters 'green steam'.

Greg

[Greg Grey Grumbly]

Dual Battery Kit

Well I pulled the trigger today and picked up my dual battery kit from Sunshine Coast based Australian Direct.
After a good deal of paralyalis by analysis, I chose the KICKASS Complete Dual Battery System comprising a battery box, complete with a Projecta 25A DC DC charger, a range of outlets and and wiring.(https://www.australiandirect.com.au/...PDCDCBATCOMKIT).

I went for this arrangement rather than an under bonnet install based on my experience with the NT Pajero which I think due to heat would destroy the Aux about every 2 years.

The kit seems really well built, cables are solid I also bought the optional metal battery tray so that I can properly anchor it in and prevent it becoming a missile in the event of an accident.

The kit goes in this week, the plan is:

• mount it between the LH rear seat back and the fridge slide
• run the supplied single cable from the start battery inside the LH chaissis rail into a cargo area Anderson splitter, with one to the DC DC charger/Aux battery, the other for the towbar for caravan connection
• pull the DC DC charger ignition feed from one of the cabin fuse box spare slots (23 I think)

I'll post an install summary when finished.

[denisp]

Made up a dual battery system for the Paj. Sport last week. Bought trays seem a little larger than the space. Used $5 worth of 1.6mm steel plate cut and flanged up edges, to fit behind the starting battery. Available space was just enough for a Exide Extreme 650 CCA sealed battery.
Had to make a mounting plate for the charging electrics. Used a VSR100 to provide the charge off the starting battery +ve. At the same time ran the caravan supplies, Batt Charge, Fridge power to the tow bar off the VSR100 auxiliary terminal via resettable circuit breakers.
Fitted a switch to allow the two batteries to parallel.
Denis

[bajabus]

Well I pulled the trigger today and picked up my dual battery kit from Sunshine Coast based Australian Direct.
After a good deal of paralyalis by analysis, I chose the KICKASS Complete Dual Battery System comprising a battery box, complete with a Projecta 25A DC DC charger, a range of outlets and and wiring.(https://www.australiandirect.com.au/...PDCDCBATCOMKIT).

I went for this arrangement rather than an under bonnet install based on my experience with the NT Pajero which I think due to heat would destroy the Aux about every 2 years.

The kit seems really well built, cables are solid I also bought the optional metal battery tray so that I can properly anchor it in and prevent it becoming a missile in the event of an accident.

The kit goes in this week, the plan is:

• mount it between the LH rear seat back and the fridge slide
• run the supplied single cable from the start battery inside the LH chaissis rail into a cargo area Anderson splitter, with one to the DC DC charger/Aux battery, the other for the towbar for caravan connection
• pull the DC DC charger ignition feed from one of the cabin fuse box spare slots (23 I think)

I'll post an install summary when finished.

Hey Greg, how did you go with your install? Keen to see the results.
B

[Greg Grey Grumbly]

Hi B,

Have a look at the Paj Sport thread ‘Wiring for dual battery and fridge, page 2 I think. I posted a full write up with pictures. It’s Woking really well, very happy.

Greg