Thread: Beware Charging Dual Battery in D4.

Originally Posted by RoverLander

What is the cut in voltage level? I assume its somewhere above 13V? Also if the voltage drops below that level but stays above 12V then I assume it stays connected. This would overcome the D4 droping below 12.7V while driving

Hi again Peter, you have it in one and the cut-in voltage level for my isolators is 13.15v.

As to needing a special charger to fully charge Calcium/Calcium ( Ca/Ca ) batteries, this is just another one of the many cons being used to get people to think they need to buy a specific product when there is no need to.

You can NOT fully charge a Ca/Ca battery buy an alternator, a true statement. The problem is that when you read some of the advertising hype about these Ca/Ca batteries, while the advertisers never actually state how high you can charge Ca/Ca batteries with an alternator, the impression you get and it’s deliberately intended, is that you are going to end up with a battery thats just got enough power to start your motor, if your lucky.

Again this is nothing short of a truck load of horse dodo.

According to info supplied by battery manufacturers, like Exide, while a standard vehicle alternator can not fully charge a Ca/Ca battery, it can charge them to between 95 and 97% SoC.

Further more, using the experience from the use of Ca/Ca cranking batteries in D3s, most give above average life spans and yet very, VERY few of these batteries have ever been fully charged.

Add to this the fact that within a very short time from now, MOST automotive batteries will be Ca/Ca type batteries because they are cheap but are proving to be excellent value because of the above average reliability and Ca/Ca Batteries have numerous other advantages over the rest of the batteries in use now, so again don’t get caught by the advertising B/S.

Originally Posted by drivesafe

Hi RoverLander and Blknight, and close Blknight.

I don’t actually use comparators but similar.


My SC80 keeps the cranking battery and any number of auxiliary/house batteries connected and what ever loads are applied to the auxiliary/house batteries is shared with the cranking battery.

When the common voltage of all the batteries reaches 12.0v, the isolator cuts out and protects the cranking battery from any further discharging.

This is not aimed at you Blknight, but a correction of a commonly stated but totally misleading bit of advertising hype, used by most dual battery isolator sellers and thats the myth that an isolator whats till the cranking battery is fully charged before connecting the auxiliary/house batteries.

ok so OOC

which side of your units are you sensing the voltage for cutout from, the crank battery or the aux battery? (Im assuming the crank)

whats the end effect of the aux batteries getting charged to a higher state of charge than the crank battery (say youve flattened the batteries to the point of cut out over night and then during the day the solar system on the aux battery has charged the aux battery)

Hi Blknight, correct, the existing SC80 and SC80-LR take their voltage readings from the cranking battery input.

The effect of charging the auxiliary/house batteries after the SC80 has isolated the cranking battery, would be that the auxiliary/house batteries would be charged but even if their voltage rose above the cut-in threshold, the cranking battery would remain isolated and only once the motor was started, would all the batteries be parallel connected again.

Over the years I have considered connecting the cranking battery to the auxiliary/house batteries if they were charged by some other source, such as solar or battery charger, but, if the cranking battery is in good condition, at 12v the cranking battery still has heaps of power reserved to be able to start the motor.

On the other hand, if the cranking battery is faulty and was the cause of the common battery voltage dropping down to 12v and the SC80 isolating the cranking battery, connecting up to a fault cranking battery has two major potential drawbacks.

1. There would be a fair waste of power and the cranking battery would continually pull the auxiliary/house batteries down to 12v, preventing them from charging to a higher level.

2. A more serious situation could also be caused by reconnecting the auxiliary/house batteries to a faulty cranking in that the auxiliary/house batteries could actually mask the faulty cranking battery to the point that you are unaware of a faulty cranking battery until the auxiliary/house batteries fail, and at this point, you could be stranded.

Hi guys n gals. For a newbie LR man like myself these forums are fantastic. Just as I am thinking what to do with the next little project you have thought through it and my little D4 is turning into an awesome machine. It doesn’t matter wether it is bull bar, power, tyres or rack!

Just a note of thanks to all you who contribute regularly to the forum.

well done, keep up the good replies....

David
"one day I dream of being able to state something that is technically sound"

Originally Posted by drivesafe

Hi Blknight, correct, the existing SC80 and SC80-LR take their voltage readings from the cranking battery input.

The effect of charging the auxiliary/house batteries after the SC80 has isolated the cranking battery, would be that the auxiliary/house batteries would be charged but even if their voltage rose above the cut-in threshold, the cranking battery would remain isolated and only once the motor was started, would all the batteries be parallel connected again.

Over the years I have considered connecting the cranking battery to the auxiliary/house batteries if they were charged by some other source, such as solar or battery charger, but, if the cranking battery is in good condition, at 12v the cranking battery still has heaps of power reserved to be able to start the motor.

On the other hand, if the cranking battery is faulty and was the cause of the common battery voltage dropping down to 12v and the SC80 isolating the cranking battery, connecting up to a fault cranking battery has two major potential drawbacks.

1. There would be a fair waste of power and the cranking battery would continually pull the auxiliary/house batteries down to 12v, preventing them from charging to a higher level.

2. A more serious situation could also be caused by reconnecting the auxiliary/house batteries to a faulty cranking in that the auxiliary/house batteries could actually mask the faulty cranking battery to the point that you are unaware of a faulty cranking battery until the auxiliary/house batteries fail, and at this point, you could be stranded.

thats about how I had it figured.

have you considered fitting or setting up the units with a manual bypass/reset that will allow you to hook the 2 batteries together for a self jumpstart/recharge? from a couple of experiences with some people who have your units but dont carry the full plethora of gear (read no jumper leads, why would I? I have dual batteries) the ability to trickle charge/jumpstart the crank battery from the AUX battery with the push of a button after some dolt left the park lights on all night would be a good thing.

whats your preferred method of hooking solar onto a traxride dual battery system?

Is there scope within the SC80 to equip it with an auxillary charge socket so that seting up solar is as simple as connecting the solar regulator output to the dedicated port on the SC80?

(I'm currently getting questioned about dual batteries+solar VS gensets with the leadup to school holidays/xmas prep)

hi drivesafe, can i ask one or two questions?

-is it true what roverlander said - that the D4 only charges when the car isn't under acceleration - ir coasting or going down hill?
-what is the reason that the Redarc's don't work - i have had a couple of redarcs in my previous landcruiser and really liked their simplicity and especially the function Blknight talks about - of being able to flip a switch and connect the second and cranking battery for starting?

thanks very much, this is an informative thread
lucas
looking to buy a D4 2.7

from personal experience

the redarcs are as dumb as a post. if anything goes wrong with the system they fail in the position they failed in, which typically is with both batteries hooked together which means 2 flat batteries.

the main failing point of the redarc is the relay they use to control the system.

Originally Posted by Blknight.aus

from personal experience

the redarcs are as dumb as a post. if anything goes wrong with the system they fail in the position they failed in, which typically is with both batteries hooked together which means 2 flat batteries.

Hi Blknight,

I dont have any experience with Redarc isolators. My set up is a DC to DC charger. Basicaly this draws power from the main battery when it is between 12.7 and 32V (for 24 volt vehicles) and converts it to a charge of 20amps and upto 15.2V. The advantage of this is that the second battery gets a full charge regardless of what the car alternator may put out.

As described above, the problem is that the D4 lets the voltage drop below 12.7 on a regular basis while driving which means that it can take longer to charge the second battery.

After more investigation today I wonder how any isolator system can ever charge a dual battery system in a D4. The way that the alternator is regulated it never makes any real attempt to fully charge the main battery let alone any additional batteries. The fact that it lets the batteries run down below 12.7V demonstrates this.

The only answer I can see is a DC to DC charger that activates by detecting that the vehicle ignition is on. This device does not yet exist. I understand the LC200 has the same problem and that people are working on an answer.

I readily admit that I'm far from an expert on Auto Electrics but this is what I've worked out so far from my experience with trying to get my setup working correctly.

Drivesafe, I accept that your system works. Its just that I can not see how it can fully utilise the capacity of the additional batteries. People are getting adequate time from their batteries because they are also drawing from the main vehicle battery (down to 12V). This is a solution that works best at the moment but it is not ideal.

Peter