Is a dc-dc charger comparable to a simple solenoid isolator?

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solidute
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Is a dc-dc charger comparable to a simple solenoid isolator?

Unread post by solidute » October 22nd, 2016, 9:09 am

just a quick question regarding dual battery set ups these days

i have a redarc dual battery isolator - their fancy version of the basic solenoid, the simplest dual battery system.

anyhow i am wondering about the new craze of using dc-dc chargers(???) for a replacement of these isolators. whats the go? is there something specific to look for? pro's vs cons etc etc?

i wanna upgrade before my trip next year but not quite sure where to start as ive only just heard of this system (yep heads been under a rock) and dont have much idea about it but it does sound better

cheers
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solidute
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Re: Is a dc-dc charger comparable to a simple solenoid isola

Unread post by solidute » October 26th, 2016, 9:41 am

so no-one has an opinion on dc-dc chargers? bugger.

well i guess its off to ask a question elsewhere.

cheers anyway
"Now and then it's good to pause in our pursuit of happiness and just be happy"
-Guillaume Apollinaire

Peter Aawen
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Re: Is a dc-dc charger comparable to a simple solenoid isola

Unread post by Peter Aawen » October 26th, 2016, 10:33 am

There's a little bit on the Forum about them if you do a search. Probably a fair few opinions too, but clearly not too many people discussing solenoid isolators vs dc-dc chargers, altho from a quick search there do seem to be a couple?! :ooh:

But for what it's worth, when it comes right down to it the Dc-Dc chargers provide almost exactly the same isolation capabilities as a solenoid isolator but somewhat smarter charge capabilities - after all, the only things a solenoid isolator really does for you is to isolate your batteries when the ignition is turned off & link your batteries in parallel when it is turned on; with the 'smart solenoids' adding a 'system' voltage sensing capability so that the linking doesn't happen immediately you turn the key but is held after turning the ignition on until the alternator starts providing charge voltage to the whole system, which is usually within moments of the engine firing up anyway!! That generally means you stand a little less chance of being stuck immediately due to battery equalisation once one battery gets substantially discharged or dies; but either way, because they work off 'system voltage' & not individual battery voltage, any solenoid system can hide one dead or dying battery in your set-up until it's too late to avoid dragging the whole system voltage down below the level necessary to start your engine & operate your vehicle & accessories if you don't look after all the batteries properly or pay attention to how they are functioning during operation - & that means you can still get stuck unable to start your engine when you least want that to occur!! But they are cheap, simple to wire & install, & with a little care & maintenance, they can be a very cost effective isolation system, albeit with a few traps for the unwary!

Because Dc-Dc Chargers actually check the individual battery voltage & not just the 'system voltage', they can go beyond just a momentary delay in the linking to avoid the 'battery equalisation' problem solenoid systems have as well as the hiding of dead or dying batteries, & by 'optimising' the charge voltage output, they can also reduce the required re-charge time for the aux battery too. So there are clear advantages to running one of them, but you do still need to learn & understand how to maintain & keep an eye on your batteries during their use & storage/downtime, or you can get caught out - it's just somewhat less likely to occur! Still, only you can decide if the extra cost & loss of simplicity in the wiring, etc is worth it for you & the way you use your vehicle & batteries.

Have Fun! ;)

Oh, & they can make it easier to link in additional charging systems too, solar panels, generators, even a 240v charger or battery tender. :thumb:
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Yendor
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Re: Is a dc-dc charger comparable to a simple solenoid isola

Unread post by Yendor » October 27th, 2016, 4:44 pm

You haven’t really given enough information about your setup for anyone to give you accurate advice.

What type of second battery do you have? where is it mounted? What do you run off the second battery? When you camp how long does the vehicle sit before being started/run? What vehicle do you own? Do you use solar panels when camping?

Chances are if the old basic VSR isolator has been working for you in the past and your setup hasn’t changed then the DC-DC won’t be of any benefit to you.

mydmax
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Re: Is a dc-dc charger comparable to a simple solenoid isola

Unread post by mydmax » October 27th, 2016, 7:05 pm

If your wiring is thick to prevent much voltage drop a solenoid simply connects the batteries together. When this happens there will be flow from the battery with a higher charge to the lower one until some balance of voltages happen.
The lower one will lessen the system voltage and if the alternator regulator can charge to the proper voltage for your battery types, then all will charge.

If wiring is small,too small, there will be too much voltage drop and full alt voltage won't be applied to the aux batteries because of the distance/resistance. This can result in insufficient charge amount and no full charge ever happening.
With a DC/DC unit, it sucks plenty of current but does apply a full voltage to the batteries because it is situated at the battery/s, but can take longer because it's ability to bulk charge is less than an alternator.
The alt reg charges proportional to the voltage difference it sees, ie, certain current flow. The DC/DC unit applies less full current flow but can sustain it until it sees a certain voltage threshold is reached before it reduces it's applied voltage and therefore current flow.

I have never used a DC/DC/ unit but a mate recently added a vehicle and solar input one to his caravan with new batteries after charging problems. Now he has no problems running his big Waeco upright van fridge.

My setup has only a solenoid link but has worked well. Perhaps i can do better.

solidute
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Re: Is a dc-dc charger comparable to a simple solenoid isola

Unread post by solidute » October 31st, 2016, 9:22 am

Yendor

it's a simple under bonnet arrangement. no solar or anything, no sitting at camp undriven. i have gotten enough info from elsewhere to suggest my battery is my downfall.

at the end of the day all i wanted to know was whats the difference between the 2 types as a dual battery system. are there pros and cons to a dc-dc. i wasnt actually trying to fault find, i was looking at the alternatives to see if i would change or not due to some chatter i had heard not long ago. clearly a dc-dc charger is not a suitable option as a dual battery system, maybe in the camper trailer but i dont have a battery in there i have an arkpak with a built in smart charger that i use for "base camp" which is portable not fixed.
"Now and then it's good to pause in our pursuit of happiness and just be happy"
-Guillaume Apollinaire

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