DC - DC Charger Vs Smart Solenoids

[REN470 Member Find all posts View Profile Close REN470]

Hi Leigh,

I have a 2014 face lifted GXL 150 and I'm looking at getting a Waeco CFX40 fridge for the back. I probably never tow a van or camper (wife reckons she's a 5 star girl) but when we go out to the lake we might be there all day and want cold drinks etc. I'm thinking of getting a SBI12 kit and running a second battery under the bonnet and then obviously some wires to the back. I'm not really all that concerned about cost or even if the batteries only last a couple of years I just want the simplest / less complicated solution.
My questions are:

is this the easiest solution ?

Do I need your fuse thingy?

What size wire should I run to the back?

When I get the wire to the back should I put a cigarette plug on it so I can just plug the fridge in - I'm a bit anal and like neat fitments?

What's the best choice for second battery?

The Prado has 5000klms on it, and has had UHF, warn winch and IPF lights added. Don't see much else, electrically, being added.


Thanks in advance.

Also I have read all this thread and as many others as I can on this subject and I admire your patience and persistence to offer logical and factual advice on this subject.

Regards
Errol

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

In my opinion, the easiest solution is to fit a second battery ( preferably two identical like two yellow top agm`s) , parallel them with heavy cable and then get the alternator booster diode thing and plug it into the rear centre console 12 v plug. Not ideal, but it works, will get you out of trouble for the odd picnic. Depends on how much and how often you run your fridge.

or put a couple of frozen 2 ltr milk in the bottom of the fridge and run it as fridge when traveling and then let it be an esky when car stopped. Used to do that in the Liberty for years, with just normal single battery.

But better to run a cable from battery via a 10 or 20A cb or fuse through the firewall, along the passenger side sill back to the rear where the jack is and put a 12v plug in there. Keep the fridge running all the time and keep an eye on the Battery volts. Use something like a twin core 50A rated cable ie 4.5mm2

For example > 24 hours fridge running 4amps draw runs 15 minutes on 15 minutes off > about 48 AH used> two decent batteries supply the 24AH each and lets you easily start the car. With booster diode and measured with a clamp on amp meter at idle the alternator is putting in 30 amps back into a battery. So a short drive and the 48AH are easily and quickly replaced.

Anyway after a few trips you get an idea of what you take out vs what you put in.
For me its not about how much ah capacity your batteries or aux battery has got, its about how easily you can replace it.

I wouldn`t bother with a solenoid to separate the batteries anymore. But would suggest that you fit something like two yellow top agm batteries.
I have got Sidewinder ABR dual battery kit and it works fine, just don`t think I need the complication and will just run two top quality batteries in parallel.


No system is completely fool proof and you need to monitor it anyway, running two top quality batteries together maximises the charging ability of the alternator, and only puts half the load on each battery. In particular as you have a winch , you may benefit from this anyway.

After all the years of having a fridge in the back, I never have parked somewhere for two days without ever starting the car and running both flat just isn`t an issue.

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

Hi Errol,

If your only going to plug the fridge in when your going to use it for the occasional one day trip then you won't need to use a booster, your alternator should be able to recover the charge in the aux over a couple of days without much trouble, using the booster would just speed things up.

As you have no intention of using a camper I would run 10mm2 as this will cope with anything your likely to use in the back, and good quality merit plugs and sockets.

Battery wise I would have recommended something like a Marinepro 730 or similar but it appears Exide have changed the model names so it would seem a Marine stowaway either the basic one or the dual. Marine batteries are good as their made to take a pounding, expected to be left idle for long periods of time so have low self discharge and even the base ones have some deep cycle ability to power navigation lights etc, but really if your only go to use it a few times a year for a day at a time just about any battery would do.

If your likely to do a lot of winching and thinking of using one of the isolators with bypass function then I would be looking at better quality battery ie the stowaways or if cash isn't a problem maybe an optima and upping the size of the cable between the cranking battery and the aux to handle the extra current.

Cheers
Leigh

[REN470 Member Find all posts View Profile Close REN470]

Thanks Leigh, appreciate the advice.

[mullerwh Member Find all posts View Profile Close mullerwh]

Leighw, I have read much about the new low voltage alternators on the diesels and has been testing the voltage via a cig socket volt meter for the last few weeks to understand how much it drops. On my 2010 150 Diesel the voltage stays consistently at 13.8 even with the lights switched on. When I put the lights on high/bright it drops to 13.7v and goes up to 13.8v the moment I switch it off. What is 'a standard' voltage one is to expect? I'm putting my dual battery system together with a Fullriver AGM 120h and are trying to make a call on whether I need the booster or not. If I add 0.5v to 13.8v is that not too high?

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

Hi REN470 and while Leigh is “SORT OF CORRECT” in that you will keep your auxiliary battery is a reasonably charged state without having one of his booster diodes fitted, I would suggest you still go the extra cost and fit one of his fuses.

While you will gain a faster recharge of your auxiliary battery, the higher operating voltage the fuse provides also means your cranking battery is maintained i a higher state of charge.

This one advantage alone will pay for the fuse, because of the extended operating life you will get from your cranking battery.

Also as Leigh suggested, if you install a winch, a combination of an Optima Yellowtop as your auxiliary battery and one of Leigh’s fuses, increasing the overall voltage, and you will then have the most advantageous winching system available.

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

13.8V is fairly normal for a 150, around 14.4V@22 is ideal if you can achieve it. 13.8V will charge
the battery but it is generally considered to be a trickle charge rate. If your touring for example
and stay somewhere for a couple of days then increasing the voltage will charge a 100Ah battery
that will accept high charge rates from 50% SOC to around 85% SOC in about and 1 hour and a half
and near fully charged in around 2.5 hours.

At 13.8V probably around 2 hours to say 75% and quite a bit longer to 95%.

If you only going to use the aux for a day etc and then leave it charging for a few days
with no load on it you can probably get away with the 13.8V as the battery will eventually
fully charge.

Cheers
Leigh

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

Hi mullerwh and if you normal maximum operating voltage is 13.8v then no, the 0.5v increase will not be too high and will be an advantage to your whole electrical system.

BUT.

Using any device that measures the voltage at a cigarette socket you risk getting erroneous readings and usually, the error reading is lower than the actual voltage at your battery.

The only way to accurately know what the voltage is at your battery, is to set up so you are measuring the voltage at the battery terminals.

I have seen cig socket volt meters close to a volt lower than the battery terminal voltage.

[REN470 Member Find all posts View Profile Close REN470]

Hi REN470 and while Leigh is “SORT OF CORRECT” in that you will keep your auxiliary battery is a reasonably charged state without having one of his booster diodes fitted, I would suggest you still go the extra cost and fit one of his fuses.

While you will gain a faster recharge of your auxiliary battery, the higher operating voltage the fuse provides also means your cranking battery is maintained i a higher state of charge.

This one advantage alone will pay for the fuse, because of the extended operating life you will get from your cranking battery.

Also as Leigh suggested, if you install a winch, a combination of an Optima Yellowtop as your auxiliary battery and one of Leigh’s fuses, increasing the overall voltage, and you will then have the most advantageous winching system available.

Thanks Drivesafe, appreciate the help.

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

Long story short.
I have a Prado 150 TD.

I have a century 105ah AGM battery that's mounted in a battery box. This will be mounted in the boot next to the fridge. I want to be able to plug the battery into the car (as a 2nd battery)

I have an engel 40ltr fridge.

I want to tow my parents caravan that has batteries (in the van) that charge via an Anderson plug while he is driving. I have been told my parents have a redarc isolator setup with a cable running to the back of the car with an Anderson plug for the trailer to plug into. It only charges the caravans batteries when the car is running.

Do I get a DCDC charger or just an isolator? considering the 2nd battery will be in the back of the prado, would the dcdc mount in the back or in the engine bay? can a redarc have multiple devices attached to it?

Do I get a redarc isolator or a

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

If old 150 you can use either, personnal prefernce which you prefer.

2.8Ltr model then at the moment probably the DCDC is the way to
go until a bit more research is done.

Keep in mind though if charging multiple batteries the more batteries
connected to one charger the longer it will take to charge them so
for instance if you have a 20A charger, charging one 100Ah batteries
discharged to 50% 3 -4 hours recharge time, two 100Ah batteies
6 - 8 hours recharge time. Depending on how many and how deeply
you discharge the batteries a VSR might still perform better than a
DCDC charger in the 2.8Ltr.unning accessories connected to the auxillary
batteries whilst charging will also lengthen recharge times.