Redarc Dual Battery System - Which one?

[bansheebuzz]

One of the most overlooked issue in running a 40amp unit. If the aux battery is dead flat, it will go into the bulk mode and command 40amps into the aux battery. It will therefore draw over 40amps from the main system to run it. The hilux has an 80amp alternator so you have now consumed over half its continuous rated output.

here is a scenario
So you have been away camping for the weekend, aux battery is down and its time to go home. Its 8pm and still 35 degrees in the middle of january

45 amps redarc
15 amps spot lights/lightbar
10 amps head lights
5 amps park lights
10 amp ac and fan(providing its on a low setting more if you like your fan fast)
so if you add that up we are now at 85 amps and i haven't factored in current consumption to run the engine electronics, radio and other minor components.

my suggestion is don't use the 40, use the 25 or 20

[Talktheroo]

One of the most overlooked issue in running a 40amp unit. If the aux battery is dead flat, it will go into the bulk mode and command 40amps into the aux battery. It will therefore draw over 40amps from the main system to run it. The hilux has an 80amp alternator so you have now consumed over half its continuous rated output.

here is a scenario
So you have been away camping for the weekend, aux battery is down and its time to go home. Its 8pm and still 35 degrees in the middle of january

45 amps redarc
15 amps spot lights/lightbar
10 amps head lights
5 amps park lights
10 amp ac and fan(providing its on a low setting more if you like your fan fast)
so if you add that up we are now at 85 amps and i haven't factored in current consumption to run the engine electronics, radio and other minor components.

my suggestion is don't use the 40, use the 25 or 20

x2.
I didn't want to say that or similar, as I said enough yesterday about other issues.
Good on you.
The Roo.

[Alby]

Is the other point regardless of if your alternator can handle it or not is how many amps can your battery handle in charge mode?
You wouldn't connect a 70 ish amp hr battery up to a 240v 40 a/h battery charger as you would cook the battery so isn't this the same overcharging scenario with a 40 DCDC?
I have always been told general rule of thumb is charge rate should be about 10% of your battery's capacity. I know there are some batteries designed for high charge rates though

[mattwhite]

That's what I was trying to get at Alby but I thought a good charger would regulate itself to battery size. Isn't that the whole point of selecting battery type? Type dictates charge voltage.

[jogal]

I've got the 40 amp model in my 2012 and it's connected to a 110amphr battery. It's been in the car since new and runs a ARB 47l 24/7! I've done 120k and fridge has never stopped. I get a constant charge of between 14.2-14.8

[Donk]

Thanks for all the comments guys. Didn't think I would have received so much feedback regarding this topic. So by the sounds of it I should stick with the 25amp kit and steer clear of the 40amp kit? Basically my plans are to have two batteries including the original cranking battery and want to run one 40L engel on weekend trips and two 40L Engels on my bigger trips. I will have a few LED lights, charge various items, run the stereo around camp, run a 12V under bonnet shower among possibly other things. I was planning to fit an ARB battery tray and without having done my research I am unsure what the biggest battery is that will fit. Hopefully they will take a 130a/h battery. I'm sure they generally measure 330mm long.

[martynvella]

Have a good read on the threads on that topic, battery weight is a bit of an issue even if you can fit it in.
I opt for 2 aux batteries for the simple reason if one gets shaken to death I can run on the other one till I can replace them. If you only have one and a cell fails then your out of business.

[Donk]

How do some of you blokes run two auxiliary batteries? Where can I fit two battery trays? Sorry if it's a silly question but I am new to Hiluxes. Picked up my first one yesterday... A 2014 SR5 dual cab.

[Malted]

How do some of you blokes run two auxiliary batteries? Where can I fit two battery trays? Sorry if it's a silly question but I am new to Hiluxes. Picked up my first one yesterday... A 2014 SR5 dual cab.

My 2010 SR V6 seems to have a heap of space available where the diesel variant would normally have the air filter canister.
My work Landcruiser has an Engel smart box in the tray that connects to the 2nd battery under the bonnet.

[martynvella]

How do some of you blokes run two auxiliary batteries? Where can I fit two battery trays? Sorry if it's a silly question but I am new to Hiluxes. Picked up my first one yesterday... A 2014 SR5 dual cab.

The second battery is usually in whatever is being towed so when it is disconnected from the car it still has power.
The other option is to put it where ever it fits. Not a lot of options in a diesel with a tub. I am toying with an idea of the space in front of the spare wheel, might just be able to squeeze in an optima mounted on its side but haven't done any serious measuring yet. That would mean changing the one in the front and trailer to AGM as well.

That sort of expense can wait till I am a lot closer to having some serious travel time when I will actually need that sort of capacity. By then probably wont even be this Hilux I go in. I work on a theory of spending as little on a car as you need to and when you need to. Right now an 80 AH in the car permanently and same in trailer is more than I need.

[mattwhite]

One of the most overlooked issue in running a 40amp unit. If the aux battery is dead flat, it will go into the bulk mode and command 40amps into the aux battery. It will therefore draw over 40amps from the main system to run it. The hilux has an 80amp alternator so you have now consumed over half its continuous rated output.

here is a scenario
So you have been away camping for the weekend, aux battery is down and its time to go home. Its 8pm and still 35 degrees in the middle of january

45 amps redarc
15 amps spot lights/lightbar
10 amps head lights
5 amps park lights
10 amp ac and fan(providing its on a low setting more if you like your fan fast)
so if you add that up we are now at 85 amps and i haven't factored in current consumption to run the engine electronics, radio and other minor components.




my suggestion is don't use the 40, use the 25 or 20

I understand this scenario banshee but don't entirely agree. There has to be some inbuilt fail safe as there is no ignition input the only thing that turns the unit on is alternator output. I don't believe it would be allowed to drain the starter battery for the sake of the aux. If your scenario were that cut and dry the redarc wouldnt isolate the batteries ever. It would simply drain the starter to keep the aux full, no matter what.

[oldhilux]

I haven't really read all the posts here and I'm not that technical so I may be missing the point, but, I'm sure the redarc only lets amps flow from the starter battery through to the auxiliary battery while the main starter battery is still in good condition (has sufficient voltage).

The alternator tops up the batteries, so if the starter battery can't be topped up sufficiently because of too much current drain the starter battery voltage will then start to drop too low which redarc detects and isolates the auxiliary battery (stops any more amps going to it from the starter) protecting the starter battery from further drain so the starter can still charge normally and continue to run all those other loads (light etc).

When the starter battery is in really good condition (has a high voltage from being topped up well), redarc then lets current flow through again to the auxiliary battery until the starter battery is not feeling too good again (has a low borderline voltage)

[Qwerty]

Hi Guys,

I went the redarc BCDC1220 ... 20amp DC-DC and im glad i did, and didnt get the 40 amp.

REason being is that I quite easily have an alternator shortfall ... even with the 20 amp.

that is, if i am idling, especially in gear (auto) , my alternator output is minimal... so much so that my redarc often puts itself back to sleep because the main battery circuit drops below 12.7v.

It's made much worse if either battery are actually low and in need or hefty charging.

Now, it's mostly not an issue, and if i am idling on tracks at night with spotlights on , i tend to use an IDLE UP switch i instlaled, which brings engine rpm to 1100rpm and therefore alternator at full tilt ... but only just.

If i'd gone for the 40amp charger, I think this "shortfall" would have been much more prominent, and the redarc would have been in a constant state of charging charging, BAIL BAIL.

The good thing is that the redarc does shut itself off (therefore overall the solution prioritises charging / protection toward the starter which is what you want...).

btw, the redarcs (mine anyway) has ignition wire, it only ever runs if the ignition is on and voltage is above 12.7 on starter.

[Qwerty]

One of the most overlooked issue in running a 40amp unit. If the aux battery is dead flat, it will go into the bulk mode and command 40amps into the aux battery. It will therefore draw over 40amps from the main system to run it. The hilux has an 80amp alternator so you have now consumed over half its continuous rated output.

here is a scenario
So you have been away camping for the weekend, aux battery is down and its time to go home. Its 8pm and still 35 degrees in the middle of january

45 amps redarc
15 amps spot lights/lightbar
10 amps head lights
5 amps park lights
10 amp ac and fan(providing its on a low setting more if you like your fan fast)
so if you add that up we are now at 85 amps and i haven't factored in current consumption to run the engine electronics, radio and other minor components.

my suggestion is don't use the 40, use the 25 or 20

Exactly the scenario I have sometimes even with the 20amp (1GRFE , different alternator to the d4d) DCDC.

40 amps would have been too much, and it would have constantly been kicking in , realising a shortfall, and kicking back out.

At least with 20amp, my DC-DC rarely overwhelms the alternator... usually only at idle, and at night with headlights on ... see my post above.

Quite a different scenario to dual batts with a smart solenoid... not even sure what the outcomes are in a shortfall scenario with one of those? Same I suppose, kicking in and out all day long each time the aux battery tries to suck up juice from the alternator andthrow the starter into shortfall.

[mattwhite]

The solenoids just click in and out. I may have to eat humble pie then qwerty based on your experience. I honestly thought the bcdc would be intelligent enough to let the starter sit at a 'float' voltage that still charged it while charging the aux rather than draw it to the point of shut down.

[Qwerty]

nah it doesn't seem to try and "de tune" what its sucking... it simply goes "uhoh, there's a shortfall, I'm outta here" and bails.

it doesn't know what the shortfall is or care, it just removes itself from the equation.

I do get a shortfall even without my DC-DC active ... if i am on the beach with my spotties, lightbar, and foggies all n ... my starter drops down as low as 12.0v if i let it. LIkewise if i pull 40-50 amps using a compressor (winches are the same).

Of course it's a good starter and the charging kicks back up when i take off so i dont end up flat... but its stil a bit dodgy and results in some dipping of SOC on the starter (if i let it).

I stuck a volt meter into my mrs car, and hers does it too (a mazda) ... basically alternators produce SFA at idle.

I guess the underlying case to be made is that there should never be a shortfall while an engine is running...

Idle up button is great for these scenarios

[Qwerty]

btw ... it does take a while, it's not instant, perhaps 60 seconds...

Dual volt meters shows me when it's happening (as opposed to opening bonnet and looking at led lights on the redarc)

[mattwhite]

Just researched it. It shuts off below 12.7 and checks that every 100 seconds.

I have the same charger as you qwerty but have no gauges, just let them do their thing. I'm amazed that they still cycle on and off. Surely it could say put out as much as it could, as long as the starter was above 13 volts or similar. A way to balance the supply and the load.

[mattwhite]

Just researched it. It shuts off below 12.7 and checks that every 100 seconds. It turns on again above 13.2.

I have the same charger as you qwerty but have no gauges, just let them do their thing. I'm amazed that they still cycle on and off. Surely it could say put out as much as it could, as long as the starter was above 13 volts or similar. A way to balance the supply and the load.

[Qwerty]

Sounds about right mate. I think it 100 seconds also probes the target battery to see how its handling things.

As to it cutting out, I guess the idea is that a "healthy" charging system shouldn't Be in the 12's range full stop , least not in traditional Charging systems, so it just bails. Not sure about the modern altys that do low voltage charging , I know my bcdc1220 isn't compatible for that sort of alternator.

Bottom line is if there's a shortfall then there's a problem and something has to give any way.