Dual battery setup

[tommy222220_0]

4GA wire is good stuff, voltage drop ought to be quite minimal - just make sure there's a fuse near the battery because if it shorts out (say it gets snagged by something as you're driving along) it will do a considerable amount of damage.

I'd go for a fuse just after the positive of each battery.

4GA wire is perfect.

If your earth points are reliable then you can earth them front and rear, but personally I think running the dual cables is far better - you KNOW that you won't have to worry about that part.

I wouldn't bother. I run 2x120ah AGM's in the back of my ute. used 4GA cable with redarc solenoid for +ve. Earths back to chassis near rear of cab, just make sure you grind the chassis contact point down so its metal on metal contact, then give it a lick of paint for rust protection. Been running great for a few years. Always have cold beer and light went we set up camp

 

[Geoff.stc]

I have just ordered a new Navara D40 ST-X.

I need a dual battery system for my Waco fridge which I had hooked up in my previous Prado.

I am planning on placing the extra AGM battery in the canopied tub within a battery box. The power and earth leads will run back to the main battery via a Redarc isolator and fuses. This system worked fine for the Prado which I am getting rid of.

HOWEVER, I have read in another forum (Exploroz) that this setup does not work in the LATEST Navara due to "the fact that the alternator rate of charge is set by the computer and can fluctuate between 11.9v to 14.9v constantly." The writer in the other forum went o to say that you therefore need to purchase a 12v to 12v battery charger from Redarc.

Does anyone with a late model Navara know anything about this? I don't want to waste money with something that isn't going to work......

Thanks in anticipation.

 

[Old.Tony]

Welcome to the forum, Geoff.

Yes, the new alternator does vary the output voltage as described and I think they have an isolator that works with the variation.

I'd be interested in finding out what happens if you drive with your headlights on - anyone with a new D40 tried that?

 

[mike1303]

I'm of the opinion that the redarc bcdc chargers store the necessary charge in capacitors then discharge to the batteries the same level every time?

Sorry if that's rubbish I'm still looking into everything it's all new to me at the moment

 

[Geoff.stc]

Thanks for the replies.

Knowing very little about auto-electrics - so if I use the Redarc bcdc charger, would I still need the Redarc isolator?

 

[Nomadic Navara]

I'm of the opinion that the redarc bcdc chargers store the necessary charge in capacitors then discharge to the batteries the same level every time?

Sorry if that's rubbish I'm still looking into everything it's all new to me at the moment

DC/DC chargers (battery boosters or what ever other name you wish to call them) are like having an inverter and a multi stage battery charger in one box. The difference is, when you have an inverter driving a battery charger you have two lots of power losses. On the other hand the battery booster does it in one hit. That way you have less power losses in the system.

PeterD

 

[Old.Tony]

Thanks for the replies.

Knowing very little about auto-electrics - so if I use the Redarc bcdc charger, would I still need the Redarc isolator?

The Redarc BCDC charger will perform the function of isolator as well - they will only charge the battery when there is power available to them. As Nomadic points out above, they are like having an inverter+charger in a single box and there are indeed losses involved.

I think if the voltage booster mentioned has a smart-charging facility (that is, it will properly boost, bulk and float-charge the auxiliary battery) then it is a reasonable choice - but I have one of these devices and I do NOT use it, because mine doesn't have any 'smart' functions at all and if it could charge the aux battery for 10 days straight at 4A it would happily do it.

The Redarc BCDC (just like the C-Tek D250S) is a smart charger designed to monitor and maintain the auxiliary battery properly. If you can get a booster that does that, great, get it - but if not, the BCDC or D250S are excellent units. Both have versions that allow input from solar panels as well, so that the one unit will perform the same function whether you're driving along (power from alternator) or sitting there cracking a coldie (unregulated solar panel - the unit has a regulator in it). With the price of folding, 120W portable solar panels dropping all the time, this might be a worthwhile investment if you can manage it.

 

[mike1303]

The Redarc BCDC charger will perform the function of isolator as well - they will only charge the battery when there is power available to them. As Nomadic points out above, they are like having an inverter+charger in a single box and there are indeed losses involved.

I think if the voltage booster mentioned has a smart-charging facility (that is, it will properly boost, bulk and float-charge the auxiliary battery) then it is a reasonable choice - but I have one of these devices and I do NOT use it, because mine doesn't have any 'smart' functions at all and if it could charge the aux battery for 10 days straight at 4A it would happily do it.

The Redarc BCDC (just like the C-Tek D250S) is a smart charger designed to monitor and maintain the auxiliary battery properly. If you can get a booster that does that, great, get it - but if not, the BCDC or D250S are excellent units. Both have versions that allow input from solar panels as well, so that the one unit will perform the same function whether you're driving along (power from alternator) or sitting there cracking a coldie (unregulated solar panel - the unit has a regulator in it). With the price of folding, 120W portable solar panels dropping all the time, this might be a worthwhile investment if you can manage it.

That's a great answer! Thanks OT cleared up some things for me!
Not only do we have to choose carefully which device to charge our batteries. We must also choose which batteries to use carefully as well.

I'm going for two 120ah agm. Because my waeco will drain on average 2.9ah at 25 degrees keeping the freezer at -15 and the fridge at 4 I believe.
I've been instructed to avoid draining them past 50% at all times, unless absolutely necessary.
That being said the bcdc 1240 redarc (off ebay for a great price) with the solar panel option is my choice to help trickle charge the system while I'm stationary for more then 3 days (unlikely to happen)

Does that all make sense or have I been misinformed somewhere down the line?

 

[Old.Tony]

That's a great answer! Thanks OT cleared up some things for me!
Not only do we have to choose carefully which device to charge our batteries. We must also choose which batteries to use carefully as well.

I'm going for two 120ah agm. Because my waeco will drain on average 2.9ah at 25 degrees keeping the freezer at -15 and the fridge at 4 I believe.
I've been instructed to avoid draining them past 50% at all times, unless absolutely necessary.
That being said the bcdc 1240 redarc (off ebay for a great price) with the solar panel option is my choice to help trickle charge the system while I'm stationary for more then 3 days (unlikely to happen)

Does that all make sense or have I been misinformed somewhere down the line?

AGM batteries are a little sturdier than that, have a look at the label - you'll probably find that you can consume power until they are at 20% of their charge level (giving you 80% of their rated capacity). That said, a philosophy of not discharging them below 50% is a good one - it leaves you with spare power, and the batteries will last longer.

A decent solar panel won't just trickle charge the batteries, either. Trickle-charging is considered no more than about 1 amp per hour. An 80W panel will output 5A easily in full sun, and a 120W panel can put out 8A or more.

 

[Geoff.stc]

Thanks everyone. I've printed out the details so I can be sure the auto-electrician knows what I am talking about.

 

[damo d40]

Dose any one have battery monitors on there dual battery set up to monitor amps /volts / if so what is a good one

 

[mike1303]

Yep,

Look up the victron BMS 600 costly i know but its unreal, just put one in my truck.
it shows me current volts, AH consumed, current AH draw, % of charge.

http://www.victronenergy.com/battery-monitors/bmv-600s%20and%20bmv-602s/

 

[damo d40]

Thanks mike

 

[mike1303]

there is a NASA built one too, its around the same pricing, but draws a significantly larger amount off the shunt. so i went to this one.

 

[RustyNav09]

Ok quick question.

Starting to get things sorted for my upfront dual battery isolation. I found a picture a while ago where someone had changed the factory dual battery setup to use one standard battery and a deep cycle on passenger side. The part I'm chasing is they cut the original terminal down ans bolted it to an aftermarket terminal to allow for more 12v sources to be installed on the main battery. I can't find the picture anywhere. If its someone who looks at this thread can you post the picture up.

Thanks

 

[RustyNav09]

Don't stress fellas. Found it

 

[YBOD]

Don't stress fellas. Found it

Sounds interesting, can you share the old picture?

 

[longy509]

Hi not sure if this warrants its own thread or not but here we go.
i have a projector dual battery set up i am not sure if it is working properly or not could even be he battery, when i start the ute up the blue light flashes which according to troubleshooting means over current any idea what would cause this.
i also just hooked up a battery monitor it is reading anywhere between

13.8 to 14.4 on the start up battery

11.9 to 12.4 on the second flooded deep cycle battery

also the meter is telling me 3/4 to full charge for start up and
about 1/2 charge for second battery

any help or advice would be appreciated

 

[Old.Tony]

I wonder if the second battery is demanding too many amps because it's been discharged too far? You could try giving it a charge with a mains-powered charger but it's not supposed to be failing like that - the charger should be able to send power to the second battery even if it's near flat.

How long does it remain like this? What's it like after driving for an hour? After about 15 minutes the starter battery should be charged up enough and the secondary should start getting a charge. Is that the case, or does it NEVER get a charge at all? I would wonder if the Projecta unit was ok.

 

[Balis0r]

Don't stress fellas. Found it

I know you said you found it already but was this what you were talking about by any chance? was thinking of buying one myself for my dual battery setup because it's got audio wiring to my CCA battery already

http://www.ozautoelectrics.com/battery-3-way-distribution-terminal-positive.html