Dual Battery

ctxkid said:

Occasional_panner said:

Just had another look at the vehicle 8.(
I should not have added the two readings as the auxillary feeds from the main battery, not direct from alternator, so the max it was making is in fact 26.9A @ idle, which is still very handy.

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my idc gives 14.4v @25amp at car idle

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Yeah, that's good, I never really bothered to check current readings. Might disconnect the redarc tomorrow and just see what the ranger does on it's own to the start batt, then plug the redarc in again and test that on the aux. What the aux gets will obviously depend on the state of charge the start battery is.
It appears my earlier tests showed a max of 26.9 from alt@ idle, but start was taking some amps and aux took the rest.

You are measuring amps ie current draw ?
Turn your headlights on and load the alt up and you will find your amp reading increases
Your alt will only supply to meet demand so your really only measuring the demand at the time of test ie current draw.
So load at time of test will determine the reading regardless the vehicle. Revs above 1200 / 1500 rpm if you load it up enough will probably get you an amp reading of approx 95% of alts amp rating.

So Mr Ampere tells me

Sweeper said:

You are measuring amps ie current draw ?
Turn your headlights on and load the alt up and you will find your amp reading increases
Your alt will only supply to meet demand so your really only measuring the demand at the time of test ie current draw.
So load at time of test will determine the reading regardless the vehicle

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Correct, but I would actually like to find out the max amps the alt will produce at idle rpm, with and without the bc/dc. I remember reading that they trick the alt into producing more than normal. In the redarc manual the blue wire is connected for "smart alternators" I didn't bother doing this so that "trick" effect really shouldn't apply in my case.

If you have smart alt will probably need to connect
With smart alt vehicle controls alt output, you want the redarc to do so. In effect the blue wire gives the redarc control of alt output

Davent,

Back to the original question, I'm assuming the battery in question is pretty flat, so the answer is regardless of alternator probably not.

There are many variables charging a battery, the important ones are; how big is the battery, how old, state of charge, is holding charge, ambient temperature, length and gauge of wiring etc.

Then comes the question of how much available output from the alternator over and above what the car itself needs.

However, if the battery is in good condition, reasonably charged to start and under no load, then the alternator will charge it. The only way to find out how much is to use a clamp ammeter to check the alternator output and that can vary i.e. daytime no lights or night time with vehicle lights on, air conditioner etc......

Sweeper said:

If you have smart alt will probably need to connect
With smart alt vehicle controls alt output, you want the redarc to do so. In effect the blue wire gives the redarc control of alt output

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the idc has a wire to hook to the ignition, tell it that you are on a smart alternator :Y: the idc shuts down and activates through this wire if running a smart alt

OK this info is only relevant for the Ranger, other vehicles will possibly be different, possibly similar.
I flattened the main and aux battery.
Disconnected the aux completely.
Started up and checked current into depleted main batt at 26.8A
While engine still running connected aux direct to batt.
Charge from alt remained the same.
Disconnected aux and reconnected via redarc 1225d
Charge from alt still the same max at 26.8A

So yes at idle at least the ranger will give very reasonable amp output if enough drain is placed on the alternator, obviously if the voltage was up on both batteries that current amount would be a lot less. But the objective was to determine max amp output at idle possible.
So it's not almost nothing as some would have you believe it's a tidy amount.

Anyone that wants to dispute this simply do your own testing, vehicle will vary anyway.

At idle and with draw, an alternator will charge a battery. The charge rate is set by the regulator and draw, not the revolutions of the motor.
As load is put on the alternator for more draw (depending on age of car tech) the engine rpm will compensate for the load on the motor from the alternator.
Also vice versa, as engine rpm is increased, voltage and amperage is regulated to compensate. Otherwise the higher we rev the more charge, that would be crazy.

Older cars sometimes needed the regulator to be excited, thus giving it a slight rev. But that is pretty old and has not been the case for a while, they have used light bulbs to do that.

I can charge a battery at 800rpm or 200rpm and it will make no difference at all to the output. Output is controlled as I said by the alternators regulator (now mostly computer controlled in conjunction with reg) and state of battery.

Hope this helps.

Late model cars, even as old as 10 years will have Smart Battery Modules. They do all sorts of calculations in order to try to prolong battery life even measuring the battery's temperature.

Try being the optimum word.

Bue wire on Redarc SBI systems if for Override function. Press button and jump start from auxiliary battery whilst holding down button.

It basically bridges the post connections temporarily when pressed.

Redarc blue wire on SBI and BCDC two completely different functions

OP is aux batt earthed via body or to primary batt earth? With blue wire not connected the alt probably can't see/sense second batt

On Redarc BCDC blue wire is a sense low voltage wire, so goes to positive main battery to trigger charge at 12v instead of 13.5

Model pending BCDC1220 Yes BCDC 1220-IGN no blue to ignition

hAyyoUinAU said:

Late model cars, even as old as 10 years will have Smart Battery Modules. They do all sorts of calculations in order to try to prolong battery life even measuring the battery's temperature.

Try being the optimum word.

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the idc25 has a battery temp monitor for just this reason , not used with standard alternator

?

No I can't, I just wondered why everyone was getting so wound up. layful:

Oh and obviously I meant 2000rpm. That's a given

will it put a charge into the battery answer yes biggest issue having the engine ideling for an hour or so which is not the best thing to do

seems there are a few different opinions on this subject, my 2 bobs worth, my RANGER has an episode last year running the bushman fridge and radio for 4 hours started the mongrel 3 times then when I was ready to go , NOTHING !!!!!! dash lights flickered , what the f is the battery flat, light bulb moment, I have 2 x75 amp hour agm's in the back, hooked one up and still nothing, then a Pajero man pitched in, hooked up his smart cables and still nothing even when his engine valve bounced, so I called the NRMA in Bathurst, perhaps I had terminal electrical meltdown, the technician found me , the bloke hooked up the smallest 40amh battery and away the Ranger went broom broom bot was I happy, question time tested my age batteries full charge, the Pajero hookup , no explanation, you will be fully charged by the time you get home further advice, the alternator reads the battery voltage and for the first 10 minutes the regulator allows a max charge then it returns to a trickle charge, the Ranger has 4 computers ,i think, the main computer kicks in to protect the battery from fully draining so the electronics are preserved. I had a battery charger but did not want to disconnect the vehicle battery , the advice ,,, carry a small 12 volt battery and connected in parallel with the main battery , before you disconnect the main battery, this will keep the computers running ,,, simple ehhh , don't ask about why the secondary battery not installed, there no room in the engine bay in the Ranger, you have to stuff it in the back , so I use my CHRISTIE gen/charge invented and made by a genius from horsley park specifically for camping and battery charging, no sun , no worries.

all the pro advice I have recieved is consistent , the vehicle alternator is not capable of fully charging a flat battery , as it takes about 10 hours on constant charge, so you drive for 5 hours and camp for 4, at the end of a week your battery is flat , dual batteries is another sales "you gotta have" thing i like it simple my car battery is for the car my camping batteries are for camping and the Christie generator/charge will and does charge flat lead acid batteries in 1 hour without damaging the battery, now lead acid batteries are as cheep as chips, i can buy 4 of those for the price of an agm

Jeez Guys we are all supposed to be Mates here and to help one another, If someone does not know all the facts or gets it mixed that's no excuse to turn on them, It would be better for all if the wiser folks re-explained it to us dumb %$&ers, I admire electronics but I bloody hate it coz it has a mind of it's own and hurts so I try to avoid it, Give me a Motor to Blue Print and I will shame the Devil him self, but when it comes to being a sparky I am a bleedin Numb Nuts. We are not all born with the same skills. :Y: