Prado alternator votage

You must check it with everything switched off and battery fully charged to get a real indication of what the voltage is.
If 14.1 v and with diode 14.6 it may then begin to overcharge normal batteries, perhaps ok for some AGM though. Why not fit a switch in that line which use the original connection OR brings the diode into the circuit for times when you require a faster of higher recharge. I did that on my HJ61 Landcruiser.

14.1 is about were 99.9% on Alternators charge. Why bother fitting a diode at all?

Depending on the circumstances of test and the accuracy of the meter there might be some errors.

There have been some changes over time with alternator voltages

prior to 05 most toyota alternators with have had pretty much fixd chraging voltages of 13.8 volts .... this was considered optimum for screw to batteries.
If you buy an after market alternator for that era of vehicles now it will probably have a charging voltage of 14.2 volts ..which is considered optimum for sealed maintenance free batteries.

Some of the later series vehicles have some level of voltage control by the ECU.
Yeh and they tend to reduce the end stage charging voltage to save fuel ... not so good for batteries.

With the modern cars, you cant just probe the battery after 15 minutes of running and know what is going on.

Not super confident about what is happening with that particular toyota and what heppens with the charging profile .... someone ela my have more detail.

If you have sealed maintenence free batteries 14.1 should be adequate.

If you are tyring to push voltage all the way to a trailer, bumping up to 14.6 volts may be worthwhile ...... a standard wet sealed maintenence free starting battery should tolerate 14.6V reasonably well, in cool weather ...... but might show stress in the heat.
Though the temperature compensation in the alternator may drop that voltage in the heat.

do you have an accurate meter than you can leave connected and drive around to see what goes on.

cheers

With the old input your battery looks like it was being undercharged with the risk of sulphation and premature failure. Suggest that you put it on a 240v charger with a recondition cycle.

Apart from that if you get the charging algorithm from the manufacturer for that battery or its type you can check the voltages needed for the recharge stages. I'd expect 14.6 to be good for the bulk stage but too high for absorption.

Where and how are you measuring alternator output?

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I presume that this is the cranking battery and not an AGM auxiliary battery.
In which case the 14.1 volt alternator output should be fine.
14.6v is a bit too high unless it is coming from a dc-dc charger with a multi-stage charging algorithm that reduces the voltage on reaching full charge.

HI,
You might find this useful.

Battery Monitor.

bill

When your measuring the alt output is that at idle or with some decent rpm behind to get it working it makes a big difference.