12v to 12v chargers. Are they necessary.

Submitted: Sunday, Apr 04, 2010 at 17:18
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I have just been reading about the Ctek D250S 12 volt to 12 volt charger. As far as I can see it is designed to go between your alternator and battery to improve charging. Is this really necessary? I would have thought that Toyota, Nissen etc would be up to organising the regulators to get appropriate charging from the alternator. Is there a lot to gain or is this one gadget I can do without?
Apologies if I have misinterpreted its designed function.
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Dave
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Reply By: Member - John and Val - Sunday, Apr 04, 2010 at 17:42

Sunday, Apr 04, 2010 at 17:42
Dave,

I'm not familiar with the Ctek one, but these things do have their place. If for example you have a battery to be charged at the back of the trailer from an alternator at the front of the Cruiser, there is a long run of wire involved and losses in the wire will result in the voltage reaching the remote battery being too low to fully charge it. The alternator is set up to charge the cranking battery that is within a metre of the alternator. In any case the deep cycle battery in the trailer would ideally be charged using a slightly higher voltage than the cranking battery requires.

Putting all that together, the 12V to 12V charger is a valuable addition if you are charging through a long length of wire. It is fitted close to the battery to be charged. It accepts whatever voltage is available and increases it to match the battery's requirements. Don't know the Ctek but most operate so as to provide a constant current to the battery, until a preset maximum voltage is reached, after which they hold that voltage while the current drops to a predetermined level. They then drop the voltage to a lower maintenance level. This is often called 3 stage charging, (though some find ways to call it up to 7 stage) and is probably the optimum for charging.

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John
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Follow Up By: Member - John and Val - Sunday, Apr 04, 2010 at 17:52

Sunday, Apr 04, 2010 at 17:52
Dave

Just had a look at the Ctek specs (here). Nice bit of kit, but at around $350+ certainly not for me!

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John
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Follow Up By: Member - David T (SA) - Sunday, Apr 04, 2010 at 18:01

Sunday, Apr 04, 2010 at 18:01
Thanks John,
Now I understand where they fit in and how they can be useful.
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Reply By: Dennis Ellery - Sunday, Apr 04, 2010 at 17:45

Sunday, Apr 04, 2010 at 17:45
I have a similar 20 amp model from ABR – it’s a very handy unit.
I use it in two situations, when charging from the 4WD’s 12 volt system.
If moving or with the motor running it provides the correct charging voltage and just as importantly limits the current to my caravan battery’s maximum limit, when it is heavily discharged. Thus safely charging the caravan battery at maximum rate in minimum time.
When stationary and with the dual batteries full in the 4WD I use it to pump spare capacity from the vehicle’s batteries to the caravan battery.

Regards Dennis
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Follow Up By: Member - David T (SA) - Sunday, Apr 04, 2010 at 18:02

Sunday, Apr 04, 2010 at 18:02
Thanks Dennis
I can see it can be useful in some circumstances.
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Reply By: Robin Miller - Monday, Apr 05, 2010 at 08:26

Monday, Apr 05, 2010 at 08:26
Hi Dave

No not really necessary , particularly if you have a good setup with heavy wires and fused adequately to your second battery.

But they do do a better job particularly when the car is hot and your alternator voltage is automatically reduced to maybe 13.2 to 13.5 from its cold startup value of about 14.1

When this happens its much harder to charge via a direct connection and it can take some hours to to replace your overnight usuage.
In fact if you have some acessories running off the second battery all the time its possible to have a senario that means it may never get fully charged.

So if a more consistent high rate of charge is what you require then they are worth having.



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Follow Up By: Member - David T (SA) - Monday, Apr 05, 2010 at 10:40

Monday, Apr 05, 2010 at 10:40
Thanks Robin
For the price I think I can manage as I always have. It's nice to understand just what is around and how it can be used.
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Reply By: Bob of KAOS - Monday, Apr 05, 2010 at 10:29

Monday, Apr 05, 2010 at 10:29
They look like an excellent piece of kit, as do all Ctek chargers. Apparently they hail from Sweden.

Its a pity they are as expensive as Toyota parts, otherwise I'd get one.
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Reply By: Mandrake's Solar Power- Monday, Apr 05, 2010 at 13:33

Monday, Apr 05, 2010 at 13:33
Just a thought here ...

An MPPT controller is a DC to DC converter ..

So would it be possible to use one - providing you could match the Alternators output Amps ?

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Steve

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Follow Up By: Mike DiD - Thursday, Apr 08, 2010 at 13:21

Thursday, Apr 08, 2010 at 13:21
Solar Panels are Constant-current sources - Alternators definitely aren't !
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Reply By: Peter McG (Member, Melbourne) - Tuesday, Apr 06, 2010 at 08:38

Tuesday, Apr 06, 2010 at 08:38
David,

If you have a recent Prado or 200 series landcruiser then you will certainly need one if you want to keep trailer or caravan battaeries charged while on the road. The alternator output of the Prado can get down to below 13v when the main battery is fully charged so you won't get anything through to charge the trailer battery.

Even with the Patrol it can be useful. You know that your batteries will be charged to float when you pull up to camp.

The Ctek though only works from 13.2v so not really useful for the Prado situation.

Others are available from Ranox, Projecta and Redarc - and I think others will be on the market before too long.

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Peter

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Follow Up By: Member - David T (SA) - Tuesday, Apr 06, 2010 at 14:19

Tuesday, Apr 06, 2010 at 14:19
Thanks Peter
I have a 100 series. So far charging the second battery ( I have separated the 2 standard batteries and replaced them with N70 size) has not been a problem and the third battery on the Tvan gets topped up from a solar panel as well as from the car. You can always get something better but sometimes I think if your system works then save the money for more travelling.
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Follow Up By: Member - Captain (WA) - Wednesday, Apr 07, 2010 at 19:55

Wednesday, Apr 07, 2010 at 19:55
Hi Peter,

Not necesarily so, I run a wet cell battery in my camper trailer and after 6 nights in the same spot it was down to 12V. Well after a 500km run home the battery is fully charged (showing 12.8V) and when I put it on my 3 stage smart charger, it went straight to float.

The secret is to make sure you use a large diameter wire to your battery from the vehicle (mine is 60mm2) to minimise voltage drop. While its certainly true that the 200 voltage is only ~13.3V after the first few minutes of starting, this will still fully recharge a battery if driven long enough.

While dc-dc chargers can have their place, they are not cost effective IMHO.

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Captain
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