Why does a CTec read less V than other charges

Submitted: Sunday, Dec 07, 2014 at 14:23

ThreadID: 110361 Views:3378 Replies:4 FollowUps:5

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CSeaJay

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Question (hopefully not a silly one)
1) When I charge my battery with a 240V charger, and take the V at the terminal, it usually reads 14.+ V
2) When I charge the battery from a 80W sloar using a $70 simple solar regulator from JCar, I read 14+V at the battery terminal
3)When I connect that same panel to the same battery but through a CTec D250s Dual, then I only read 13.6V at terminal

Is this to do with the smarts of the CTek, or is something wrong? Note all the correct lights are on, no error flashings etc.

I would welcome comments on whether I should have the Ctek checked out?

CJ

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Reply By: HKB Electronics - Sunday, Dec 07, 2014 at 14:57

Reply By: AlbyNSW - Sunday, Dec 07, 2014 at 16:08

Reply By: Member - Phil G (SA) - Sunday, Dec 07, 2014 at 21:40

Sunday, Dec 07, 2014 at 21:40

I run two of the D250S duals. They settle on around 14.4 volts (at 20 deg) in charge mode from solar panel when my battery is close to fully charged. The voltage will read lower if the battery is discharged and the panel's output is insufficient to bring it up to 14.4V.
An ammeter (clampmeter) is great in this situation to let you know how much current is actually going into the battery.
Also it takes up to a minute for the CTek to sort out what's going on before it sends full charge to the battery. From your description above, it suggests you need give it a few minutes before it gets up to full charge voltage.

AnswerID: 542693

Follow Up By: CSeaJay - Monday, Dec 08, 2014 at 11:22

Monday, Dec 08, 2014 at 11:22

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

FollowupID: 829199

Follow Up By: Member - Phil G (SA) - Monday, Dec 08, 2014 at 14:41

Monday, Dec 08, 2014 at 14:41

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.

FollowupID: 829219

Follow Up By: Member - Phil G (SA) - Monday, Dec 08, 2014 at 14:51

Monday, Dec 08, 2014 at 14:51

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.

FollowupID: 829222