You ask hard questions for which there is no easy answer.

Land Rover withdrew their official Land Rover rebuilt units from their distribution system last year, apparently due to high warranty costs. In other words, warranty replacements were costing LR too much money, hence LR only stocks brand new Denso now. Presumably Denso carries the warranty costs now.

In my case, I installed a rebuilt unit branded as WAI, (Wilson to those of a certain age.) Yes, the first unit proved defective after a week or so and the second unit came with the wrong grooved pulley, but two years later, it is still working so it is probably OK.

And your alternator red light is probably working correctly. True it does not show when the alternator is not working correctly however in LR thinking, that does not mean the light is not working properly - dah.

Perhaps someday LR will discover something called an amp meter. It is a wonderful concept - when the needle leans right, that infers amps are going into the battery, left means out of the battery, and really left is bad. Who knows what the future holds but there is always hope. In the meantime, the Prince of Darkness still rides.

 

I see you have a traxide dual battery.

So does that mean you have the main battery then another battery in the back of the car somewhere?

I bought the same jump battery that AAA uses and keep it in the back just in case.

Clore ES5000 'Booster PAC' 12V Portable Battery Booster

 

The 3 has space for a second battery in the engine compartment under that second lid that looks the reverse of the lid that covers the starting battery.

The link below details my install of the second battery using a kit developed by an Australian.

DISCO3.CO.UK Photo Gallery - Traxide Dual Battery install in LHDrive

Below is a link to the Traxide kits. Discovery 3 DBS Kits | TRAXIDE - RV | Traxide - RV

I still take a battery jumper pack with me on trips but fortunately have yet to require it.

The second battery setup that I have works more as a reserve to keep battery voltage up when idling at traffic lights etc and hence to keep the computers happy. The regulator within the alternator is supposed to do that but due to emission concerns, really does not - instead load shedding is favored and to my mind was a compromise but is far from ideal.

In other words, I think a second battery install is a good idea. Most do it when they have installed a winch - it is certainly recommended for that, but I think it is good insurance, period - that and a separate battery pack such as you have purchased.

 

I think this is the link you were trying to post.

Clore Booster PAC Review 2015 - TopTenREVIEWS

The one I use is an older Black and Decker unit with a built in air compressor - that is also something might want to carry with you - a 12 volt air compressor - it sure beats changing a tyre as most flats are relatively slow leaks.

 

I may do that, that interstate battery I have probably is not bad, maybe I could use that as a second battery. I did not think about that other compartment. Nice.

So does it auto kick in? If battery 1 dies does it take over or is it just part of the main? Meaning both are used all the time.

 

I would go by those reviews, the one you linked gives it a 4.7/10 which is incorrect. I spoke with the AAA tow guy and they use them in all the cars. All they do is drive around all day jumping dead cars for the insurance company. He said no issues, they just have to charge them each night. They jump like 16 cars a day.

Plus a lady had jumper cables and even after 10 minutes on the cables my car would barely turn over. Not enough to start. Then the tow guy drives up and hooks this tiny looking jump box to my LR3. One turn of my key and Vroom! its running. I'm like "i've got to get me one of those"


So if its good enough for commercial insurance company I figured it was good enough for me.

That air compressor is a really good idea too. I have one in my garage but that jump pack has a 12 volt receptacle in it. I could run a compressor off it. Not many gas stations in my area even have a air hose.

 

For the second battery compartment, you have to use a shorter H5 sized battery. The brake booster pieces take up too much of the space.

Also when you purchase a battery, try to get one that has no lips on the bottom ends. The lips or tie down ledges consume horizontal length and the brake booster is fatter at the bottom; also there is a 45 degree angled bit at the front inside bottom corner of the battery box; nothing is simple on a Land Rover.

No, the second battery auto kicks out when there is real trouble.

Traxide has at least three of flavours of the switcher device now. As such, you will have to read the stuff on the site to find out how they all work.

Generally speaking, when all is well, the truck runs off both batteries as you asked. The switcher device monitors the system voltage and cuts out the second battery below some predetermined volts number. The idea is that the primary battery could go dead but the secondary will still have near full charge.

In my system, I would then attach a set of battery cables and boost from the aux to the primary to at least get the engine going. Traxide now has a newer switcher variation where you push a button on the dash and the aux battery automatically connects to the primary.

The way the 3's alternator/regulator most often fails is that the regulator fails and goes to a default voltage of perhaps 13.1 volts, (maybe a bit less), and the alternator continues to generate power at the voltage. 13.1 is generally not enough to charge either battery however so eventually the primary battery does not have enough charge to start the engine once shut down.

The 13.1 volt default set point is also why the red battery light rarely goes on to give any warning. As such, regulator failure means no start but while the engine is running all seems OK.

This is why I keep a Scangauge II connected to my OBD port all the time to monitor charging system voltage to give me a warning of electrical trouble. Additionally the Traxide system tends to mask regulator failure so you can go for months with a defective regulator and still have engine starting, at least in the summer. Again, nothing is simple in a Land Rover.

DISCO3.CO.UK Photo Gallery - ScanGauge II on LR3