Why does a CTec read less V than other charges

Alby
Is this from solar? how many W?
CJ

No that is from alternator in a typical dual battery setup, the reading is from my second battery.
I have solar as well but it is not connected at the moment

Thanks Phil for the feedback;
Please advise, does your voltage slowly creep up (over hours) and then settle at the level you indicated?
Or is it, similar to connecting to a charger, that the voltage reads high as soon as the bulk charge starts?
Cheers, CJ

CJ,
The voltage measured at the battery terminals varies with
- the state of charge of the battery
- how many amps are going into it
- the battery capacity and
- what condition the battery is in (amongst other factors!)
In most camping situations it will read below 14.4V.

Example #1: You are camped, the battery is down to 50% (say 12.3V) and it starts getting recharged from the solar panel (say 2-3 amps going in when the sun is out) then the voltage will rise slowly and would take a long time to reach 14.4V.
If the alternator was recharging it through the CTek, it would probably get the full 20 amps and the voltage will get to 14.4V within an hour or two.

Example #2: The battery is almost fully charged (say 12.8V) and the same 2-3 amps going in from the solar panel, the voltage will most likely reach 14.4 and sit on that voltage for a long time before dropping down to float (around 13.7).
If the alternator was recharging it, then voltage would reach 14.4V within a minute or two stay up there for an hour or two then flick down to float voltage.

And just to add, that if you are only reading 13.6V at the aux battery with the alternator running thru the Ctek, then either the battery is mostly discharged (and accepting the full 20A from the Ctek) or the wiring is crappy or the earth is crappy. Check the voltage at the Ctek input when the alternator is running.

I tested a mate's Prado and Caravan wiring once because the caravan battery was not charging thru the anderson plug and he had 6mm automotive wire all the way and poor earthing. He had no current going in when the motor was running. Good earths between each battery and chassis are important.