The 150 series Dual Battery Guide

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

foxpro,

It is not practical to swap the batteries around, the sense point for the alternator voltage regulator
in the Prado is the main fuse box, if you extended the battery connection cables to the passenger
side you'll affect both the charge voltage and available starter current, both guards would have more
or less the same rating, overseas models most likely have the starter battery on the right side, some
of the display Grandes when they first come out had factory batteries fitted to both sides.

If you decide to go with an AGM and intending to charge of the alternator, make sure it can tolerate
high inrush currents and under bonnet temperatures.

For what it is worth I agree 100% with Leigh, just not worth the trouble of swapping the starter battery around. If you want more AH out of the aux then go AGM and put it in the back. That is what I did.

[MelbournePark Member Find all posts View Profile Close MelbournePark]

MelbournePark,

When you say an AGM will charge faster what AGM are you actually referring to?

A lot of AGM"s have quite low maximum recharge rates, ones that can accept high
recharge rates state around 3 hours to fully charge.

I have done extensive testing with MarinePros and they will charge from around 50% SOC
to fully charged in around 120 minutes and have hard data to support it. If your referring to an Optima it is not a typical AGM deep cycle battery, it was specifically designed for rapid recharging off an alternator?

Can you supply some model numbers and link to data sheets?

What would be the advantage in a DCDC charger in the above install, it will slow recharge times considerably unless a 40A or higher unit is installed and then more or less match the alternator?

If you look at it from the solar side, none of the current crop of combo units have very efficient mppt controllers built in, granted if your on a tight budget and not worried about efficiency or redundancy they could be a good choice, but if you want maximum efficiency out of your panels a good quality mppt charger would be a better choice?

They all need to be checked before buying. I'm not going to publish all the batteries with their stats here. Its buyer beware.

As far as the Marine Pro quick charging, does the 620 charge in the same time as the 730 in a dual setup?

You've said you have a Marine Pro as your starter, and an Optima as your spare. You've also said that the Optima charges very quickly. I presume you are running a D34 for the spare, with a 720 as your starter battery?

I also think charge depends on what style of camping / touring your going to do. If you're an itinerant / nomad like I tend to be - and go from place to place every day or two - then IMO a fast take-up battery makes a lot more sense.

Another issue is the amperage available. Lets hope that the Prado with your volt enhancer equipped has an excess of 60 amps after it runs its air con, thermostats, radars and smarts and computers and network et, sat navs, ABS and crawls and all the other stuff. That means with two batteries receiving charge, they'd have 30 amps available for each. So I think that in that case, an AGM with a 30 amp input capacity, is all you need.

And if you had a 10 amp accepting main battery, then would a higher accepting AGM be a benefit? Perhaps not if the starting battery played a major game in providing power.

For instance, if you had a 730 with 100 amps as your main battery, it would likely have 50 amps to be re-charged. If that took two hours, then what would be the point in having an AGM that would charge its own amount (a D34 with 60% to recover would require only 33 AH to recover). But the real main issue would be recovering the 50 amps from the slower accepting Marine Pro 730. Therefor - its more sensible to have two marine Pros and save the money. Why have a fast recovering on the second battery when one half the cost will match the main battery's re-charge?

Likewise for any other battery. Add a trailer onto the back of the Prado with a couple of batteries in the trailer, and the benefits of 30 amp accepting batteries in the vehicle would diminish. Ultimately its about the bottlenecks IMO. I'll post a couple of batteries that appealed to me a later on, in another post.

I'll finish this post here - its gone too long. Apologies to all.

[MelbournePark Member Find all posts View Profile Close MelbournePark]

As far as publishing data, you've mentioned Optima brand a lot. Could you publish their discharge graphs here?

As far as solar goes for Fox - yep, its a complex field, and really much dependent on how long he's camping, and for what periods. Solar - there's a 50% difference from cloud to sunny. And with fridges, there's a big difference from frozen compared to 5C, and from warm weather compared to stinking hot. 240 watts of solar cost some, and then you have to get it into the battery, with the vagaries of the weather too.

Incidentally as far as using the motor - I would like to add the comment not to run a diesel stationary for charging please. Our Prado diesel engines are not designed for that.

As far as DC - DC units and all the rest, and even the voltage of solar units (some are said to be only 17) everything has to be checked out. No need for Fox to do that though - he's doesn't want to spend much, he made that clear. So solar is out. IMO the longer one (ie Fox or myself) delays solar the better, because its cost is dropping all the time. These thin film solars appeal to me too due to their size and weight and evidently their efficiency - but for their current cost.

As far as alternative batteries, its worthwhile for Fox to consider some choices. I think weekend camping and a few longer trips per year, one doesn't need to invest in the best cycling long life system. I do think though that a real cycling battery - rather than a marine style - is worth considering for the spare battery if its usage is considered. A problem though with such batteries, is that they do tend to take up power slowly, due to their heavier plates and that may not suit Fox. I'll check my database too.

I'd like to publish some notes too on battery longevity published by manufacturers, but perhaps when this site calms down. Its interesting to read what the manufacturers say about such things IMO. When I do I'll post the linkages so people can read the sources.

The restrictions for Prado users though for the second battery in the front is probably 260mm and not over 24kg - at least for Fox. The 620 at 260mm and 18.11kg and 75AH seems a safe low cost bet if the Marine style suits his usage.

And by the way, the weights for the Marine Pros were not from the current website, which is wrong. I spoke to Century and the weight of the 620 is 18.11kg, which makes sense. Sometime their website will be updated.

[MelbournePark Member Find all posts View Profile Close MelbournePark]

foxpro,
... overseas models most likely have the starter battery on the right side, some
of the display Grandes when they first come out had factory batteries fitted to both sides.
...

The overseas Prados use both batteries for starting. They do this because of European winters, where it can require lots of battery to start a diesel. -25C is not uncommon in Berlin. Some Prados are also now assembled in Russia, and lots of the East can be colder than Berlin.

i checked this out some time ago, and found the battery replacements recommended weighed close to 22kg.

[foxpro Member Find all posts View Profile Close foxpro]

LeighW
I value your insights. I'm not really worried about cracking guards. It was a point to consider but as I want a second battery anyway I have to take this route and trust Toyota has this issue under control now. From what I gathered from this thread battery space is restricted to about 260mm wide aux batteries b/c of the aircon pipe although some squeezed larger units in by either bending the aircon pipe or living with cramped interior. TJM apparently has a special tray for Prado 2014 GX's now which allows 305mm batteries. I will check space again when my el cheapo unit arrives from ebay.

I got the point of not swapping aux and starter battery. Thanks for the advice. I don't consider this further.

[foxpro Member Find all posts View Profile Close foxpro]

mjrandom
Putting the aux inside the car makes sense but I'm cramming for space so the only logical solution for me was under the bonnet. My goal is to set the Prado up as a tourer fit to take three adults around Australia w/o a trailer. It will have a customized cargo area with only three seats remaining.

[foxpro Member Find all posts View Profile Close foxpro]

If you decide to go with an AGM and intending to charge of the alternator, make sure it can tolerate
high inrush currents and under bonnet temperatures.

I have got a thermal sleeve for the aux battery and for the rest just hope that the battery is up for it.

[foxpro Member Find all posts View Profile Close foxpro]

I
Main battery
Its silly not to replace your main battery IMO.

It might start with the Marine Pro 620 as aux and drop in a new starter should I feel the need to.

Yesterday I have wired up the Sidewinder rear connection and DC panel in the bottle jack door. Looks neat and did not require any holes to be drilled through plastic except for the bottle jack door now being a dedicated power panel.

[foxpro Member Find all posts View Profile Close foxpro]

For people who have installed the Sidewinder DBi-140. What is the best location for it? The manual recommends drilled and screwed onto the inner guard but I have seen pictures somewhere with it being mounted on top of the plastic fuse box.

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

Inner guard is more secure and better practice.

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

Have a look for factory weld nuts/holes in the guard and make up a little bracket. Plenty to choose from in a Toyota.

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

MelbournePark,

What an amazing transformation it has been, from someone who admitted knowing little about batteries a few days ago to now being a battery and dual battery system expert

I actual have a Optima D27 as a start battery and a Marine pro as the aux, the Optima depending on how you use the vehicle is not an ideal choice for a cranking battery but was put there for evaluation purposes. The Optima may provide higher CCA but in my observations this has not been the case, and due to its lower Ah capacity is not a good choice if your vehicle is garaged for long periods.

The fact that a battery has a maximum recommended charge rate of 20 - 30 amps doesn't mean that is the maximum charge rate the battery will accept, it is purely a warning that it shouldn't be charged at higher than that rate, all large capacity lead acid batteries will pull higher than 20 - 30 amps in a highly discharged state, the manufacture is simply advising the current should be limited to less than the max allowed.

Relying on manufactures specs is fraught with danger, after doing acceptance testing for various companies for over 40 years I can tell you that seldom does equipment meet the manufactures own specifications, most equipment needs massaging to meet the manufacturers specs, and in quite a few cases the purchaser has to down grade his requirement (usually the manufactures own specs) so that the supplied equipment can meet the customers specification. I remember many many, moons ago rejecting a batch of batteries due to low specific gravity and low Ah capacity. The manufacture asked how we were measuring the SG, we were using an electronic specific density lab instrument, the manufacturer was still using the old glass tube and rubber bulb type units!

I personally would not recommend any battery to another unless I had tested the battery in vehicle and had logged hard data to prove the battery performed as expected.

You keep saying the slower accepting marinepro to an AGM, I assume you have read somewhere that AGM's charge faster than flooded batteries, some do many others won't, if you took the solid separators out of a 720 and replaced them with glass mat would it now charge faster? There's a lot more to a batteries charge acceptance than glass mats.

Dual battery systems in cars can be quite complex, how many batteries need to be charged, what does the battery require, where are the batteries going to be located, what charge voltage is available, what size cable. It is no good putting two optimas in a trailer and then supply them via the cars aux for instance, unless huge cabling is installed little charging of the Optimas is going to occur until the cars aux gets to a reasonable state of charge, why do it this way then, main reason would be to limit the load on the alternator and isolator. The advantage of having a high charge acceptance battery in the car is the quicker it gets charged the quicker the trailer batteries will charge in this type of setup.

Fitting a booster to the alternator does not increase it's output power ie x watts, only its charge voltage, if you start to add additional batteries then you need to consider the load on the alternator, be the aux charged directly through a VSR or DCDC charger. More batteries more load, once you reach three batteries then you should definitely consider the load on the alternator if three highly discharged batteries are suddenly dumped across it. If the alternator can't supply the amps then the only particle alternative is a bigger alternator. Putting in a DCDC charger to limit the current is generally pointless, if you have 400Ah of batteries your obviously using high Ah, and most are never going to drive long enough to put the charge back in.

Interestingly though I have never came across an instance of an alternator failing due to overload, neither has drivesafe in many many years he has been installing dual battery systems. The manufactures will tell you its possible but IMO this is more from a thermal load perspective than actual amps drawn, if the mounting location of the alternator is poorly chosen and it can't shed its heat load then it will fail due to overheating issues. If the alternator is rated a 100% continuous output (many aren't) and it has sufficient airflow its very principal of operation provides some inherit overload protection. But that's a whole other story.

Better to be safe than sorry so all should ponder battery management when multiple batteries are involved.

You mentioned something along the lines will a 620 charge as fast as a 730 but can't find it again, they are basically the same battery just different plate count, therefore the 730 will have less surface area and peak recharge currents will be lower, however it is also a lower Ah capacity therefore one would expect it to be take similar or possibly less time to charge than the 730, only way to tell is by actual testing.

Charge discharge curves, discharge curves are readily available from most manufactures, Optima being the exception unless they have changed recently.

Charge curves, don't recall having ever seen one but then haven't gone looking for them as it pretty pointless from a dual battery perspective as the charge voltage, available current, wire dimensions, number and quality of connections are going to impact charging significantly anyway. Better to do some actually real time testing.

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

MelbournePark,

What an amazing transformation it has been, from someone who admitted knowing little about batteries a few days ago to now being a battery and dual battery system expert

LOL Leigh I've been reading this thread all the way through with that comment in the back of my mind.

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

LOL Leigh I've been reading this thread all the way through with that comment in the back of my mind.

You deserve a gold star if your reading it all I've just been skimming it for a while now. Like I said a while ago, I am amazed at how complicated you can make such a simple thing if you try hard enough

Cheers Andrew

[Prone Member Find all posts View Profile Close Prone]

MelbournePark,

Fitting a booster to the alternator does not increase it's output power ie x watts, only its charge voltage, if you start to add additional batteries then you need to consider the load on the alternator, be the aux charged directly through a VSR or DCDC charger. More batteries more load, once you reach three batteries then you should definitely consider the load on the alternator if three highly discharged batteries are suddenly dumped across it. If the alternator can't supply the amps then the only particle alternative is a bigger alternator. Putting in a DCDC charger to limit the current is generally pointless, if you have 400Ah of batteries your obviously using high Ah, and most are never going to drive long enough to put the charge back in.

Leigh,

Being a bit pedantic and risking starting an argument I think that the first point in the above is incorrect. There will be a small power increase equal to the current by the voltage increase. At 50 amps the increase will be about 30 Watts for a 0.6V voltage increase.

(Andrew, I agree can I have my gold star please? Maybe I forfeited it by this post though!)

Cheers
Prone