Dual battery setup for 2.8 1GD

[LeighW]

The Enerdrive DC2DC units might be more suitable in this situation, they monitor the input voltage and when they see the alternator has started charging they turn on, they continue to monitor the input voltage and if it drops the charging stops and it monitors the input voltage to see if it recvovers if it does it assumes the voltage drop is caused by the wiring and starts charging again. It continues to monitor the input voltage at regular intervals. If the input voltage drops to much and the unit determines the alternator is still charging it reduces its output current to protect the undersize input wiring.

Disadvantages of these units are they are quite big and not waterproof as they have a cooling fan, advantages apart from above are they a fully user programmable have a display to show you what's going on and appear to be very robust.

[LeadWings]

The issue I had was when I first started the car in the morning at idle, when the DC-DC kicked in and sucked the 30A it needs to make 25A to the battery the voltage would sag till the alternator/engine responded the higher load and pulled the volts back up again, but the voltage sag caused the Dc-Dc to trip. When diagnosing the issue I had my volt meter on the DC-DC in, which is where I saw the voltage drop (briefly) to around the 11V I mentioned.

If I put the idle up button in or held the revs up, this would not happen - ie the voltage would not sag as low.

If it did not drop when the DC-DC first kicked in, then it would be all good from then on and with an alternator output of 13.4V I see around 12.2V at the Dc-DC - so Drivesafe this agrees with the numbers you noted.

So really the issue was a cold engine just idling and the low voltage the system runs at, and the time it takes to respond to the fairly sudden demand of an additional 30A. For other loads (eg turning spotties on) this would not be an issue, but for the DC-Dc that has a low voltage cut-out it can be an issue.

[drivesafe]

Hi LeadWings, as Michael posted, that is a huge voltage drop.

If your alternator was operating at 13.6v, with a 40 amp current draw over 10m of 6B&S twin ( 2 x 6B&S ) you should still be getting 12.48v at the input of your DC/DC device, so something is seriously wrong with your setup.

Even with an alternator voltage of 13.2v, you should be getting at least 12.1v at the input of the DC/DC device.

[rpn]

I used one of these in our camper trailer, very happy with it. I found even with 6 B&S/AWG cable (about 10m worth from battery to camper battery) I needed the IGN sense wire connected as the voltage in goes down to around 11 V at times.

I originally allowed for the IGN sense but after measuring main battery volts when the engine is running decided it wasn't needed.

Maybe try measuring the voltage drop across connectors (Anderson etc) and terminals in the cable run, both pos and neg. May have dirty or loose connections.

[120D4D]

That's a huge voltage drop LeadWings and suggest your alternator is putting out around 12.5v on idle?

[LeadWings]

Last night I installed a Projecta IDC25 DC-DC charger in our 2.8 GXL. It's quite straightforward to install, although a little fiddly routing the heavy cables around the engine bay. I haven't connected the IGN sense wire as yet, it seems to work without it. Certainly better charge volts on the Aux battery compared with main battery.

I used one of these in our camper trailer, very happy with it. I found even with 6 B&S/AWG cable (about 10m worth from battery to camper battery) I needed the IGN sense wire connected as the voltage in goes down to around 11 V at times.

[rpn]

Last night I installed a Projecta IDC25 DC-DC charger in our 2.8 GXL. It's quite straightforward to install, although a little fiddly routing the heavy cables around the engine bay. I haven't connected the IGN sense wire as yet, it seems to work without it. Certainly better charge volts on the Aux battery compared with main battery.

Happy with the pricing, the IDC25 kit with 50A fuses for each battery was about $300 delivered, plus a few $$ for cables and terminals. I used a Century deep cycle battery that I had from a previous vehicle and sat it in a modified Piranha tray and used the standard Toyota clamp mounts.

[LeadWings]

Hey dbc,

No solar panels yet but I did wire up the Anderson plug to the solar input so it's ready to go. my dad is going to give me a good quality solar panel that's surplus to his need but it is an inbuilt regulator. Does this mean it can't be used with the bcdc1225d?

Just put a set of Andersons (or the same connector that you have for the leads to the battery) between the panel and the inbuilt regulator - then you can use it normally (ie to charge other batteries) but when you want to use it on the Redarc bypass the inbuilt regulator and connect the lead to the Redarc straight from the panel outputs.

[dBC]

my dad is going to give me a good quality solar panel that's surplus to his need but it is an inbuilt regulator. Does this mean it can't be used with the bcdc1225d?

Yes, I'm afraid so, unless you can find a way to isolate the regulator and tap in directly to the panel output prior to the regulator.

[2016VX]

Nice. Did you get a solar panel for it as well? You may already know this from your research, but in case not, the Redarc charger needs an unregulated or "raw" panel as it does its own MPPT. More as a test than anything else, I picked up a small cheap-n-cheery panel from Whitworths. It works so well that I now stick it out in the sun whenever I'm camped somewhere for multiple days.

Hey dbc,

No solar panels yet but I did wire up the Anderson plug to the solar input so it's ready to go. my dad is going to give me a good quality solar panel that's surplus to his need but it is an inbuilt regulator. Does this mean it can't be used with the bcdc1225d?


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[dBC]

Just a 40W. I think it was this one, although they occasionally have them on special:

https://www.whitworths.com.au/main_i...AbsolutePage=1

I just cut the alligator clamps off and put Andersons on so I can plug it straight into the Redarc, which is happy to do its bulk/absorption/float cycle on the strength of just a 40W source. Obviously the bulk stage isn't 25A in that case, just whatever it can muster from the available power source... about 2-3A from memory. "Constant current" is a bit of a misnomer in that case because the charge cycle is power limited.

[brogers]

What was the wattage of the panel dBC?

[dBC]

Will see how it goes in the summer when we venture back up to Fraser Island for a couple of weeks.

Nice. Did you get a solar panel for it as well? You may already know this from your research, but in case not, the Redarc charger needs an unregulated or "raw" panel as it does its own MPPT. More as a test than anything else, I picked up a small cheap-n-cheery panel from Whitworths. It works so well that I now stick it out in the sun whenever I'm camped somewhere for multiple days.

[drivesafe]

I think that 25A charger from Redarc really hits a sweetspot of price, charge times and battery longevity for those of us stuck with the low alternator output voltages of the 2.8L.

Speed of charging and improved longevity can be achieved just as well and most likely even better, when charging off an alternator, even with the lower voltages in new Prados.

For example, with one of my isolators and only using the same amount of capacity that you would use with your single battery setup, while camping, because the amount of used battery capacity is spread over two batteries, neither battery is discharged to anywhere near as low as you have to discharge your single battery, to get the same amount of energy required while camping.

Not having to discharge any battery as low as you have to, will mean an improvement in battery longevity.

Again, because batteries in setups using my isolators are not discharged anywhere as low as you have to discharge yours, will mean the batteries would back to a near fully charged state in a shorter drive time than what the DC/DC device could do.

This to would improve longevity.

Another improvement when using one of my setups is, because the current load needed to power accessories, is spread over two batteries not one like yours, this means the current load applied to each battery is much lower than in your setup and this will not only improves longevity but a lower current draw placed on any lead acid battery also means you have a greater amount of energy available ( see Peukerts Exponent ), so this to adds to the batteries longevity.

And one more MAJOR advantage to using one of my isolators over using any DC/DC device, is that because of the way my isolators work, where the auxiliary battery is allowed to continually back discharge into the cranking battery when the motor is off. This progressively raises the settled charge state and condition of the cranking battery, which means BOTH batteries are likely to have a far better lifespan than your DC/DC setup could ever achieve.

dBC, you MIGHT get a single advantage when topping of your battery while driving around town, but you need to know all the real world facts about battery use and maintenance before thinking that that one POSSIBLE advantage outweighs all the real world disadvantages not covered in the glossy advertising used to sell DC/DC devices.

[2016VX]

I agree dBC. I did a heck of a lot of research (mostly from this forum) and I kept coming back to the BCDC1225D. 40A was too much for me and anything less seemed like a waste of time. Will see how it goes in the summer when we venture back up to Fraser Island for a couple of weeks.

The hardest part was feeding the cables through the car to the rear. The 3rd row seats create issues when removing the trim, but otherwise was relatively straight forward! Piranha battery tray is also built like a brick "Out House".