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Chopperp

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Joined: 03/01/2018
Location: Australia
Posts: 1057

Posted: 08:00am 01 Feb 2021

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Hi all.

Just wondering what the thoughts are on using a "Smart" 12V charger on a battery with equipment e.g. a 2-way radio, connected.

I have a couple of so called Smart chargers & the outputs can go over 15V at times. As well they seem to rely on a low-ish charge current to switch back down to the trickle or maintenance charge & voltage.

My thoughts are that if a load is attached to the battery, the charge current may not drop low enough for the charger to detect when the battery is fully charged. (I think some chargers will time out if full charge is not reached in a given time frame).

You will also have the varying load such as a radio on transmitting, upsetting the charging routine.

In my thinking, a fixed voltage charger (or power supply) my be the better way to go in this scenario.

Thanks,

Brian

ChopperP

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Joined: 09/08/2007
Location: Australia
Posts: 4406

Posted: 08:42am 01 Feb 2021

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You are probably right Brian.
It does not take much to outsmart a "smart" charger.
They seem to be more suited to just straight charging a battery that has been removed for charging.

A typical automotive system has an alternator regulated pretty much to about 14.2v or something close to that all the time, and the system loads are all over the place, with some very large and sudden changes.

Constant voltage charging does seem to work quite well in that application, and its simple.

Cheers, �Tony.

Chopperp

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Joined: 03/01/2018
Location: Australia
Posts: 1057

Posted: 09:13am 01 Feb 2021

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Thanks Tony

I know some modern vehicle alternators (D-Max) drop their voltage after a bit to save some power. Frustrating when trying to charge an external caravan battery without using a DC-DC converter.

Brian

ChopperP

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Joined: 09/08/2007
Location: Australia
Posts: 4406

Posted: 09:27am 01 Feb 2021

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One solution to the caravan problem, is to fit a second alternator that works completely separate from the cars existing electrical system.

Far fewer problems and surprises !

Cheers, �Tony.

Murphy's friend

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Joined: 04/10/2019
Location: Australia
Posts: 648

Posted: 09:00am 02 Feb 2021

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Chopperp said Thanks Tony

I know some modern vehicle alternators (D-Max) drop their voltage after a bit to save some power. Frustrating when trying to charge an external caravan battery without using a DC-DC converter.

Brian

Brian, I happen to drive a D-Max with that smart alternator. There are two ways to outsmart it.
1. drive with the headlights on.
2. remove the 'smart' sensing bit (just cutting a wire) and replace it with a small switch so you can choose 'smart' or 'dumb'.

I have the second option.

Chopperp

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Joined: 03/01/2018
Location: Australia
Posts: 1057

Posted: 09:52pm 02 Feb 2021

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Hi Guys,

Re D-Max.
A friend of mine traveling from Toowoomba around Australia in his new D-Max was wondering why his van or auxiliary battery (or both) wasn't charging.
I think he tried various things & it wasn't until he got to Kununarra, WA that an auto electrician told him why & promptly sold him & installed a DC-DC converter at a much inflated price.
No suggestion of turning on the headlights, which he would have known about.

Brian

ChopperP

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