Originally Posted by
trout1105
I have NO idea HOW these devices work ....
My suspicions are that you probably do, just don't yet realise it.
My thoughts are that they're operation is 'just like' a 240v modern smart/multi stage battery charger, with the main difference is that instead of 240v coming in(then rectified and transformed) the input is 12-14 or so volts coming off the vehicle electrical system.
Like Tombie said, you're vehicles volts in plus whatever amps can be allowed through the input side(ie. Watts) will give you a digitally regulated output for the battery type you want to charge up.
Think of them in this manner: take a typical modern battery charger like a C-tek type. Also take a 12 -> 240v Inverter with you on your travels. Hook up your inverter to the car, hook up the Ctek to the aux batteries .. basically the same thing only a bit less wasteful.
If you're auxiliary batteries are flooded cells, sounds to me like a bit of waste of $s.
If any other type like AGM or Lead Crystal or whatever is 'the next best thing since sliced bread' ... then they can be handy to keep the auxiliary batteries in better shape.
More importantly the question(ie. if you need them) would be better answered if you stated the type of batteries you have as the auxiliaries in whichever vehicle you want to use it for.
The way I'm seeing it is that, say for example you want the Redarc 40 Amp model to charge your 200Ah aux regular flooded cell batteries.
Your alternator can output near on 100A. So you can run the DC-DC no worries, as the input side(your car) allows about 1200W or so of power into the DC-DC.
But now, you have 40 amps output for those 200Ah aux batteries, as that is as far as the DC-DC will allow.
But, if your aux batteries were AGM which usually require 14.7v, just using a normal VSR solenoid won't give you that in most vehicles(if any. Your D2 won't!!), so the AGM could be an advantage, even tho it's still only allowing 40Amps through to the batteries.
The advantage being the 14.7 volts when set to charge AGM batteries.
If you have a smart battery charger at home(the multi stage/Ctek type that allows you specify a battery type) .. think of it as the same thing, difference being that it's not 240v mains input, it's typical vehicle input .. some usually say 9-30v, so can work in trucks and stuff too.
But in your hypothetical application(say the D2) the input is going to be about 14v .. 13.8 to about 14.4 from what I've seen out of my Discos so far.
I'm not exactly sure your setup(s) but sounds like one main battery for starting and then two auxiliary batteries down back for power usage. You have a solar panel too.?
If this is right, I'd leave the anderson plug in all the time so that the batteries just charge up .. assuming a regulated solar panel for the aux batteries.
Leave the anderson plug in, assuming that the solar is charging up the system.
The standard 'dumb' VSR will keep the starter battery connected for a period after shutdown, and with the solar charging the system now, it will keep the VSR on and continue to keep the starter battery topped up too.
If you don't have a regulator on the solar to the aux batteries, don't do the above.
I've done this many times, not with solar, but the 240v charger, where I've connected it to the aux battery after getting home. It keeps the starter battery topped up for example if it's going to be a bit frosty the next morning.
Oh! and the reason I pop it on the Aux, is sometimes I park in a certain spot and the cable lengths are just perfect. But the point is that some VSRs have reverse sensing ability(Redarc does), so any charging power coming into the aux will also charge the starter.
A topped up start battery is better than one sitting un topped up, yeah?
The other thing that is a bit unclear is your solar setup. Sounds like it's hard mounted to the roof or something. So always connected and hence charging the aux batteries all the time?
So, you have a VSR fitted and solar always on fitted? If you have a VSR, which one?
Arthur.
'99 D1 300Tdi Auto
'03 D2 Td5 Auto
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