Thread: The Battery Posts: final warning

No offense to all, and I have stayed out of these threads because I cannot contribute in anyway, but how many threads are there now on basically the same topic? Couldn't you keep it all in the original thread and let me and others just ignore one thread rather than many?

Originally Posted by roamer

But is it a LR D3\D4 charging system,because it's the varying voltage that is somewhat at question.


Cheers Ken

The alternator is the bit that does the voltage varying, I can get my hands on a d4 alternator and rig that up without excessive hassle, if it doesnt perform as expected during the control then I'll have to work something else out. I have my feelings about how the test will go anyway but dont want to post them up incase it goes ahead and people percive that I have a bias (I Do, nothing beats my DBS when it comes to getting amps back to batteries) that will skew the testing procedure.

Hi Dave, personally I wouldn’t worry about getting to finicky with how the voltages may or may not vary.

Why not just set up to do a worst case scenario and then any body wishing to use the test results as a reference point, can do so knowing they are the worst likely outcome.

I’ve already been doing some testing but they are unlikely to be viewed as unbiased and are more for the benefit of my customers, but it will still be interesting to compere the end results.

the question was asked and in honesty it was a point that I hadnt considered.

given that the majority of the disputing is about the multivolt alternators charging through various means then thats what should (if feasable, Im not going and ripping a complete brain and harness out of a d3/4 just to run the alternator properly) be tested.

If not its going to be a case of some random 100A alternator from my pile chucking amps at batteries.

Hi dave and here is some info based on observations I made of the operation of the D3 alternator.

After the first start of the day, the alternator voltage will by up around 14.4v to 14.9v ( the highest voltage I recorded and this was common ) for 30 minutes. This is a form of bulk charging.

The voltage then drops back to ( on average ) 13.6v and remain there. The lowest voltage I ever recorded was 13.2v and this was rare.

If the motor is stopped and then started again, even with a time gaps of 4 hours or more, between stopping the motor and then starting again, the alternator will again run at a bulk charge voltage but only for 10 minutes, then the voltage again drops.

Note, the transition from the initial bulk charge voltage to the operating voltage is almost instantaneous, taking no more than a second or two to change voltage levels.

yep, IVe noticed it but not because of any specific testing just one of those "huh thats odd" type observations.

I suspect that the change down point is as much draw related as it is computer controlled to conserve energy so if that theory is correct if you dump a decent load on once the output of the alternator goes past the trigger point it should push the volts back up to help deal with the load.

one of the tests I've always wanted to do on the electrical system of a D4 is to get it up and running till the voltage drops to its low charge voltage then whack a honking great load onto it without turning the engine off and measure the amps and volts on the back of the alternator.

Hi Dave, I’ve done a few tests on 3Lt D4s and they have a totally different operating protocol.

The main difference is the way the voltage rises when ever the load is removed from the motor.

I have not had a chance to do what you’re talking about, checking the current load.

Will have to do that one day when I can get a local D4 owner with some time to spare to oblige.

As for the D3 ( + the 2.7Lt D4 ), no matter what the load is, it has no effect on the voltage change.

I first found out about the variable voltage thing when one came in with an intermitant alarm on the inverter that had been fitted in the rear, turned out to be a dodgy earth connection that was dropping the voltage enough that when the alternator went to low charge mode the inverter was beeping off its low voltage protection.

simple fix, made the earth something decent and then instructed the owner to not leave the inverter on if he wasnt using it.