CTEK D250S DC to DC battery charger

[Strick]

Gday guys,

Bit of a weird one here. I have a CTEK DC to DC D250S controlling my dual battery system. Main battery going to the alternator pictured connection, with my secondary battery going to the battery pictured connection. Earth to the chassis rail.

Now, it seems im getting 23.7v on the service battery connection at the CTEK its self. The reason I was looking is due to plugging in my fridge from the connection at the back and it wasnt working. Voltage check on the plug 23V, check on the fuse block 23V, check on the battery 12.6V, check on the CTEK 23v.

Have I simply interrupted the charging cycle, which would mean that the voltage is at its max to get max amps into the secondary battery? Will it even out once charged.

This doesnt seem very good as it means a non consistent supply to my rear cigarette charger for my fridge. Or is the unit faulty.

The battery has 12.6V so I would of thought this would be what would be read at the fuse block, but for some reason im getting the 23V.

Ive had one of these units in another car and it didnt miss a beat!

 

[Strick]

Upon further investigation this morning, the voltage is jumping all over the place when running ( constant supply to main battery) so seems like the internal voltage regulator is stuffed. Will have to swap the unit out.

 

[JCruse]

Can you tell me the benefit of a DC to DC charger in a truck?

I think they use them on boats where there are multiple whole banks of batteries, and diesel generators. But in this case why not use the Alt?

I'm sure there's a good reason, it's just that I don't know it.

 

[Strick]

Gday mate, the idea is that the dc to dc unit ensures the main battery is charged first, then charges the aux battery. My unit also has a connection for solar panels, which means when Parked up for a long time will charge both batteries.

Also has inbuilt cut offs and temp sensors etc.

 

[george_tlc]

You don't need a DC to DC supply to deal with charging the main first. Many marine combiners will only connect the aux battery (for charging) once the main battery has reach a specified voltage (level of charge).

Anyhow, from my EE perspective, a complicated DC to DC charger it's just another piece of electronics that is liable to fail.

I'd rather have a separate solar charger that deals with MPPT or PWM charging versus an all in one unit that if it fails prevents any charging from either the alternator or solar. Though at least you can always revert to jumping the aux to the main to charge while driving along - assuming you've brought cables with you or have some other way to join the batteries.

KISS and redundancy is not a bad thing when out in the bush miles from a repair workshop...

cheers,
george.