Will the alternator charge my second battery with a dual battery set-up???

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Just make sure the alternator drive belt can handle the extra load.

The company here has just setup an LC200 fitted with a 390 amp alternator, so I’ll ask them if there were other modifications needed to be made.

[Shangus Find all posts View Profile Close Shangus]

The company here has just setup an LC200 fitted with a 390 amp alternator, so I’ll ask them if there were other modifications needed to be made.

Keen to here how you go. I'm currently looking at getting a high output one sent over from the states. Only around 200amps not 390. It would be good to know if there's an importer over here.Only mods should be upgrading the the main positive and negative power cables , the big3 as they say,but I'm unsure about the cables to the alt fuse till I talk to a good sparkie so whatever you can find would be appreciated.
Cheers Shangus

[Rexracer Lurker Find all posts View Profile Close Rexracer]

I'm an Auto Electrician, and i will start by saying i don't normally comment on forums that involve work but i though i would voice my opinion on this topic, i have a lot of experience in this field as its what i specialize in, no shameless plugs here though, just want to give the members of this site my experienced opinion, i too have a Prado and for what its worth a Hilux as well, i find this post interesting, some good advice and some ordinary advice....so break out the popcorn as im about to reopen a large can of worms......

Alternator Fuse Diode - yes you will see a voltage increase, and maybe that's enough for the charging of an extra auxiliary battery, however why would you want to 'modify' a reliable and factory designed system to trick itself into outputting a higher output than designed ? this system is designed like that to reduce fuel economy for one, and how is your alternator and other factory designed systems going to last the long term if the alternator is set to maximum output all the time ? my advice is stay away from this set up, sorry LeighW but i think this is a cheap and cheerful way of doing a dual battery system, and why anyone would want to jeopardize their new $60k + new Prado with some cheap cheerful mod i have no idea, if they work with no side effects then lucky you, you are more game than me..............go ahead school me if you like

DCDC charger - So they arent cheap right ? neither is a Prado, so why go cheap on your new car ? There are a few big advantages with a DCDC charger for charging a auxiliary battery in any car let alone the Prado with a temperature compensating alternator, here are is my experienced opinion.
1. Charge Rate - The second battery charge rate can be tailored to suit the battery chemistry type, this is very important as the chances of your start battery and the auxiliary deep cycle battery wanting the same charge rates and charge times is zero, battery life will suffer greatly if a battery is overcharged or undercharged, plain and simple.....
2. Independence - with a DCDC charger the auxiliary battery will run completely independent of the start battery and the rest of the cars electrical system, so even when in charging mode with the car running the two battery systems are running completely independent of each other, if there is a fault on the auxiliary battery circuit this will not effect the cars electrics, worst case scenario it trips the circuit breaker of the DCDC charger, which has a considerably less threshold than a standard isolator setup.
3. Battery Life - The DCDC chargers on todays market are staged chargers, meaning they charge the same way most of your modern 240 to 12v chargers do, with a Boost stage, Absorption stage and most importantly a float charge, the float charge will not only trickle charge the battery and safely get the battery up to 100% but it will also avoid overcharging the battery, this will increase battery life.

Warranty wise i think you will find most dealers like to play hardball if they think they can get paid twice the labour rate of warranty and get full retail for their parts if you have modified your vehicle at all, however if they can prove that the DCDC charger was at fault (cant see that happening though) then at least you will have the backing of a large company like Redarc or CTEK that will help you fight the dealers claim that the product is at fault, again i really cant see this happening, but how will an eBay seller or some small company help you get an issue fixed on your $60k + 4x4 if something goes wrong ?

These are the questions you need to ask yourself fellow Prado Owners, i hope this helps

[D4D Addicted PP Member Find all posts View Profile Close D4D]

1. Charge Rate - The second battery charge rate can be tailored to suit the battery chemistry type, this is very important as the chances of your start battery and the auxiliary deep cycle battery wanting the same charge rates and charge times is zero

Zero huh? Try again...

[snewby Junior Member Find all posts View Profile Close snewby]

You can just see my CTEC on the top left....(sorry its a 120-2007)

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

This all a bit of a pointless discussion nowadays. It seems to me that both systems will work, which is better just depends on how you want to prioritize the different pros and cons and how you interpret the information.

Given the number of people running diodes and the length of time they have been around and the distinct lack of people coming forward with any issues suggests that problems they create are somewhere in the vicinity of non existent. Likewise with a DCDC issues seem to be non existent from a point of view of them causing damage.

So its a bit like the Petrol V Diesel, Waeco v Engel, OME v Bilstein, 120 v 150 discussions, none are necessarily better or worse just different, and different people have different needs so different methods suit different people.

Having said all that deep down everyone know that Diesel 120's with OME suspension are the best, and no right minded person would buy a Waeco or an Engel when they could get an ARB fridge........... Oh and White is the best colour as well

Cheers Andrew

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

"I'm an Auto Electrician, and i will start by saying i don't normally comment on forums that involve work but i though i would voice my opinion on this topic, i have a lot of experience in this field as its what i specialize in, no shameless plugs here though, just want to give the members of this site my experienced opinion, i too have a Prado and for what its worth a Hilux as well, i find this post interesting, some good advice and some ordinary advice....so break out the popcorn as im about to reopen a large can of worms......"

The usual one time poster trying to stir the pot, many other auto electricians I supply
don't agree with you?

"Alternator Fuse Diode - yes you will see a voltage increase, and maybe that's enough for the charging of an extra auxiliary battery, however why would you want to 'modify' a reliable and factory designed system to trick itself into outputting a higher output than designed ? this system is designed like that to reduce fuel economy for one, and how is your alternator and other factory designed systems going to last the long term if the alternator is set to maximum output all the time ? my advice is stay away from this set up, sorry LeighW but i think this is a cheap and cheerful way of doing a dual battery system, and why anyone would want to jeopardize their new $60k + new Prado with some cheap cheerful mod i have no idea, if they work with no side effects then lucky you, you are more game than me..............go ahead school me if you like"

As the voltage remains in the range specified as normal for the vehicle how does it jeopardize the vehicle?

1. Charge Rate - The second battery charge rate can be tailored to suit the battery chemistry type, this is very important as the chances of your start battery and the auxiliary deep cycle battery wanting the same charge rates and charge times is zero, battery life will suffer greatly if a battery is overcharged or undercharged, plain and simple.....

Most batteries 97% will fall in the AGM setting ie 14.4V same as the alternator charges at, only really good for a full calcium battery. All battery chargers are only a substitute alternator!

3. Battery Life - The DCDC chargers on todays market are staged chargers, meaning they charge the same way most of your modern 240 to 12v chargers do, with a Boost stage, Absorption stage and most importantly a float charge, the float charge will not only trickle charge the battery and safely get the battery up to 100% but it will also avoid overcharging the battery, this will increase battery life.

Most will never fully charge their batteries, float is a gimick and only really applicable to 24/7 charging. All battery manufactures I have read state charging at normal bulk voltage for up to 24 hours will cause no problems. However they do state that float charge voltages for AGM batteries are critical and can shorten the life of the battery considerable, yet how many chargers have the ability to change the float voltage to suit the battery?


Warranty wise yes the manufacturer should cover his product but when it comes to the car you will be on your own no matter what the manufacture.

Leigh

[OldGreyFart Advanced Member Find all posts View Profile Close OldGreyFart]

Anything is electrical and black magic to me. My 2008 Prado (120 D4D) had a dual battery setup put in when I bought last Sept. I asked the auto electrician did we need a diode and he said WHY? I accepted his advice. He separately installed a battery into my Cub trailer with a CTEK charger in the system.

I have longest trip I have done is 10 days without any problem with the car fridge at all with driving everyday - the small trailed fridge wanted to shut down after about 5 days but the internal lights kept working for the whole trip. I was using the small fridge as a freezer - but worked out later I didn't need to.

The last trip I did was 6 days camping and the trailer fridge and lights worked perfectly.

Nothing special about this setup but it seems to work.

I suppose my real question is how long would I need to drive to keep the trailer battery (its 100amp) charged if I stay out of powered sites?

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Depends on how much you have discharged your battery, charger is limited to
around 20A so around one hour to put back in 20Ah.

The car aux will not fully charge as quick as it would with a booster diode fitted,
but will still replace the bulk charge much quicker than a 20A charger will hence why
you don't have a problem with the in car battery.

Also using the fridge as freezer will greatly increase power consumption.

Leigh

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

I'm an Auto Electrician

For an auto electrician, you haven’t measured the voltage in very many vehicles or you would know that there are still a large number of vehicle makes that do not have variable voltage alternator operations and as such, most of these vehicles have CONSTANT alternator voltages similar to what an Alternator Voltage Booster Fuse creates, so as a "claimed to be" auto electrician, can you explain why none of these vehicle cook their cranking batteries, or damage them in any way.

As to your implied threat to a vehicle’s warranty. Because the voltage at the cranking battery is so much better than in normal use, the cranking battery is far FAR more likely to outlast the warranty so as it is in the vehicle manufacturer’s best interest to get longer life spans for the cranking batteries, why would there be an issue with fitting one of LeighW's fuses?

The lower operating voltage is a requirement that the vehicle must meet at the time the Compliance Plate is fitted to the vehicle.

Once the plate is fitted, indicating that that specific vehicle has meet the Compliance requirements at the time the plate was fitted, there is not only no need to make sure the vehicle’s operation remains inside the compliance of the vehicle at the time of the fitting, if there was a need to continue the compliance, you could not turn on the vehicle’s air conditioning without having the vehicle operating outside the compliance requirements.

So not only is there no legal reason for leaving the voltage low in these vehicle, but a number of vehicle manufacturers now offer a number of solutions to raise their vehicle’s operating voltage. A fact that as an auto electrician, you should already be aware of.

VW has two override switches in their vehicles. One overrides the low voltage and Stop/Start programming for each journey if you press the button at the beginning of the journey. While the other switch when turned on, permanently overrides the programming, allowing their vehicles to operate at a constant 14+v at all times.

Land Rovers, fitted with Stop/Start programming also have a trip override switch.

Ford has a dealer supplied option where you can pay a fee and have the BMS reprogrammed to allow their Range to operate at 14+v all the time.

So as an auto electrician, you seem to be some what behind the times as none of these manufacturers find any problem with setting the voltages at levels similar to the voltage levels that LeighW’s fuses operate at.

So can you give a single example of where a battery was damaged in any of these above cases, or can we just take it that you were out to troll the forum?

[maxjj Senior Member Find all posts View Profile Close maxjj]

the only thing I can add, is that my brand new Landcruisers with 2 batteries which are wired in parallel standard from factory sit at around 12.6v if I check them in the morning, that is not fully charged. The charging voltage is just too low. With Leigh`s booster diode its 12.8V

In the Prado and by that I assume the Hilux wasn`t too bad, the voltage in the morning was 12.8v. I suspect that was due to the fact that for general driving the 4 cyl motor runs with higher revs.

I had two Prado`s and even though the charging voltage seemed sufficient to look after the main battery for normal duties, once you also needed to top up an aux battery and keep up to a fridge etc, it just didn`t supply enough. On idle the standard voltage would put out 20A to aux battery , with booster 30A, it allows for much quicker recovery of your aux and standard battery.

I never saw a voltage over 14.6v with booster diode in the Prado, which by the way is what my Liberty runs it continuously. I used to not worry about it over summer in the Prado if I wasn`t running the car fridge, but in the Landcruiser it just brings it up to normal.

[rob_macca67 Avid PP Poster! Find all posts View Profile Close rob_macca67]

Thanks Leigh.... That's what I'm hoping to do. Hopefully the local dealer might help me too (I can dream too )

Well.... Toyota came to the party and supplied and fitted for free a NEW Toyota OEM ALTERNATOR...... gotta be happy with that !!! I also now have a SPARE ALT for those future trips

[BNEGXL Member Find all posts View Profile Close BNEGXL]

Interesting comment,

"and why anyone would want to jeopardize their new $60k + new Prado with some cheap cheerful mod i have no idea"

You're suggesting that by using an Alternator Fuse Diode that I am jeopardising the entire $60k Prado?

So the Alternator Fuse Diode will cause the car to be a write off?

Great opinion I'm sure, for me a little too late, 4 years on and the car is going strong, no hint of a write off.

I suspect the most accurate words you wrote are the last four I quoted from your post.

"i have no idea"

[snewby Junior Member Find all posts View Profile Close snewby]

AJ120... Just added the ARB fridge to the sig list (full house-just for you) :-)

[rob_macca67 Avid PP Poster! Find all posts View Profile Close rob_macca67]

Well.... Toyota came to the party and supplied and fitted for free a NEW Toyota OEM ALTERNATOR...... gotta be happy with that !!! I also now have a SPARE ALT for those future trips

Wow.... Since having the aftermarket alternator installed in our car, I had no need to put the voltage booster diode back in...... Until Toyota recently reinstalled a OEM Toyota alternator back in our Prado. I've noticed the charging volts go from around the low 14volts down to the highest I saw it of 13.8volts.... I since reinstalled the booster diode fuse back in the car and now the charging volts are now at least back up into the 14v bracket again.... Interesting.....

Rob