Dual battery in 2012 GXL

[Kimberley prado Lurker Find all posts View Profile Close Kimberley prado]

I am wanting to put a dual battery system in my 2012 GXL. Do I need to put in an expensive bcdc charger to charge both batteries or will a voltage sensitive relay do the job.?

[kenny5000 Advanced Member Find all posts View Profile Close kenny5000]

Search and you shall find all the info you need:

http://www.pradopoint.com/showthread...-Battery-Guide

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

Short answer no, VSR will work better, if you have a low voltage alternator also fit a booster diode.

Cheers
Leigh

[GEEEXL Member Find all posts View Profile Close GEEEXL]

Short answer no, VSR will work better, if you have a low voltage alternator also fit a booster diode.

Cheers
Leigh

Leigh, I have a 150 series d4d prado built 25/12/2014 - how I work out if I have a low voltage alt or not ?

G

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

If it is not the new 2.8Ltr and the OEM alternator is fitted it will have the low voltage high compensation type alternator.

The other test if your not sure is to check the voltage across the battery terminals after driving for 30 minutes or so, if the voltage is less than 14V with the engine at 1500RPM then
you have a low voltage unit.

Cheers

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

Hi Leigh

I am having a dual battery setup installed in new Jan 20166 2.8L GXL Diesel Prado by the toyota dealer. Is this going to be an issue.. I run a couple of Engels mainly. What type alternator do the new facelift prados have??

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

They appear to have a fixed voltage output of around the 13.6V range, unfortunately they
no longer appear to have the ALT-S fuse of the earlier models so some research will be required.

See the dual batteries in the 150 electrical section

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

Alt-S Fuse

They appear to have a fixed voltage output of around the 13.6V range, unfortunately they
no longer appear to have the ALT-S fuse of the earlier models so some research will be required.

See the dual batteries in the 150 electrical section

Thanks LeighW - What ramifications does the Alt-S fuse have if no longer fitted??

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

My booster diodes replaced the ALT-S fuse to increase the charge voltage.

If yo can't boost the alternators output then you may need to use a DCDC charger.

[crog Lurker Find all posts View Profile Close crog]

13.6v is a low float voltage for a 12 V battery (without temp comp) or 2.26Volts per cell but as engine bay is hotter than nominal 25 Deg C this is why your alternator is putting out this voltage to protect the battery life and hence the battery will be fine and draw as much current as needed to charge the battery and operate in a float (trickle charge mode) which maximises life.

As mentioned it is actually on the lower side which has be done to protect the batteries which need to tolerate higher temperatures in the engine bay and allows for the temperature compensation of -3mv/Deg C /Cell ie lower voltage at higher temps. Be careful increasing charging voltage too much with booster diodes as it will dramastically shorten your battery life particuarily VRLA which likely second battery will be

My recommendation is leave it as it is and you should be fine at 2.26V output of the alternator

If you want to know more from my text book

"The correct setting of the charge voltage limit is critical and ranges from 2.20V to 2.45V per cell. Setting the voltage threshold is a compromise, and battery experts refer to this as “dancing on the head of a needle.” On one hand, the battery wants to be fully charged to get maximum capacity and avoid sulfation on the negative plate; on the other hand, an over-saturated condition causes grid corrosion on the positive plate and induces gassing.

The temperature changes the voltage and this makes “dancing on the head of a needle” even more difficult. To get a complete charge and prevent overcharging, warmer temperature requires a slightly lower voltage threshold and colder temperature prefers a higher setting. Chargers exposed to temperature fluctuations should include temperature sensors to adjust the charge voltage for optimum charge efficiency.

The charge temperature coefficient of a lead acid cell is -3mV/°C. Establishing 25°C (77°F) as the midpoint, the charge voltage should be reduced by 3mV per cell for every degree above 25°C and increased by 3mV per cell for every degree below 25°C. If this is not possible, it is better to choose a lower voltage for safety reasons. Table 2 compares the advantages and limitations of various peak voltage settings."

As most engines are hotter than 25 voltages need to be lower. PM me if you want more detailed info

[crog Lurker Find all posts View Profile Close crog]

Sorry quick question are you running pure dual battery in parallel or do you have a low voltage disconnection control unit on the main battery to ensure you don't pull both down below cranking voltage if you discharge to much?

A VRLA (sealed battery valve regulated lead acid) typically second battery) is not designed to crank a starter but for deep cycle loads so you need to protect the main battery which will be flooded cell and has ability to deliver high short circuit currents.

It is not as simple as running them in parallel off the alternator I have seen too may issues with this setup when guys have run accessories too long

just be aware of the above it catches guys out

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

Crog,

I would like to know where you get your info from, the 13.6V you specify is for
batteries being float charged 24/7, not for charging in a cylic situation. A
dual battery system is a compromise, yes the rapid charging will have some affect
on battery life but in cyclic operation no one is going to wait days for there
battery to charge.

There are VRLA that are designed for use as cranking batteries.

Car batteries are not trickle charged, they need to recover their charge as quickly as pratical to ensure they car start the car at the next attempt. Cars have until recently always ran charging voltages of around 14.5V@25, this is from the time of electromechanical regulators which by the way were temperature compensated as has been just about every car generator/alternator known to man, they used these voltages as they have proven over a 100 years or more to be a good compromise between battery life and rapid recharging.

Stating a standard temeperature compensation table that are intending for charging batteries in an controlled enviroment is pretty useless in regards to under bonnet temperatures that vary greatly. Also as the alternator and battery are generally mounted in a cool stream their temperatures will differ from the "under bonnet" temperature. The actual temperature sensing is done in the alternator and it is the temperature of that sensor that will determine the charge voltage to be applied.

As for booster diodes dramatically shortening battery life that is just plain rubbish, if used in
junction with high compensation alternators it restores the voltages to what have been the
norm for over a hundred years, the are thousands of my units alone in use and I haven't
seen anyone one on this or others forums complaining of this issue.

Another new member that has not even bothered to read the wealth of information contained in this forum or perhaps just another troll?