Dual battery configuration - a test question

I agree. Its just an IGN dcdc module with the capability of connecting the 2 batteries at once and does not incorporate the charger for this issue......or am I missing something?

Hmm, the momentary button is a great feature, piece of cake to add to a system that doesn't have one (like mine) . . . think that'll have to happen, make any sort of jump starting needs very simple.

Les, it certainly is a worthwhile change.

I installed a normal toggle switch in the centre console of the cabin in place of the momentary type.

Simple to link all three batteries for very cold (snow type) starting and winching. I also have a led in the cabin to show when the solenoid is activated either by it's own circuitry or the switch. Nice and bright one that "hits" the driver in the eye and reminds him, or her, that the toggle switch in "on".

Phil

Edited: Change to a better image.

The front yellow switch is the Redarc solenoid (ie front - bonnet location). The rear yellow switch is the compressor solenoid (ie rear - located at the rear of the car).

Nice set up Phil.
Think I'd look for an actual momentary button you'd just push in on the dash, start up, then releases automatically.
Simpler when you can't rely on the old brain cells to remember these things :)

No good for winching though Les.

Recently it took the group 6 hours to do the 12 km long Mount Sunday Track because of all the winching. Two hours just to winch all 9 cars up the bad steep rocky section.

Even though the led is there, we are yet to forget the switch. As far as I know, it really wont hurt to be left on. We don't have a BCDC.

Phil

True, but if I ever fit a winch and use one (I have one new and sitting outside, along with a hitch cradle :)), I'd be leaving the engine running anyway, both to cover the current draw and more, and drive assist rather than dead pull.

Mt Sunday in the Alpine Nat Pk ?
Walked along / up to that summit, when doing the Aust Alps Walking Track :)

I took a whole weekend cutting, shaping and testing the holes for the switches.
And it was worth it. You can tell what's on at night out of the corner oy your eye.
We also run the motor when winching. Always have and will. I think that you would have to be a mug not to.

That's the track mate. And we went there just after heaps of rain. You can walk - I will drive. The amount of oxygen my blood can carry is stuffed - so I drive.

I have a nice big dent in the steel side steps now; thanks to that track.

I am about done with damaging the car in the high country. We will stick to the deserts I think, from now on. But then again; they, the mob, may change my mind.

Phil

Like Phil, I too have used a SPST (ie: On/Off) switch to control my Redarc solenoid on the Chevy.

My reason is a little different......

I have a single 100a/h aux battery inside the canopy that runs a 60 litre Engel full time. Under the bonnet there are 2 factory-fitted batteries, needed to fire the 6.6 litre donk.

On the canopy there are 2 large solar panels which feed the aux battery via a solar regulator contraption. By switching the solenoid ON I can keep the front batteries charged off the solar panels. I have no idea what wattage the solar panels are, but the original owner was using them to charge THREE aux batteries to run 2 fridges (one as a freezer) as well as a 2000 watt inverter to boil his kettle etc.

I generally leave the switch in the ON position virtually all the time.

Giving me ideas now Roachie.

Catchya

You can also get the bidirectional SB12 which will connect if the voltage on either side goes over 13.2v That automatically connects / disconnects the two batteries when solar charging.

Less- pk ranger ....... you alternator will not cover the winch current ....... most winches will draw 400 amps at stall ...... that is way more than your alternator and more than double most starter motors.

winching hammers batteries ..... getting a second battery on the circuit dramaticaly reduced the wear and tear on the batteries and give a much more solid source of supply.

the two batteries will also accept more change than the single battery ....... so sucking down 200 to 400 amps with the winch then putting back 100ish from the alternator ..... becomes more viable on a 1:4 duty cycle.

personally I use a manual switch rather than a solenoid, because most solenoids are not rated as high as manual battery switches.

cheers

Someone of like mind. That's exactly why we only have an SB12 installed. Puts all three batteries on line as required.

Phil

If you're going to be doing a lot of continuous winching use a snatch block whenever you can the benefits far out way the extra work involved in setting it up several times because of the shorter pulling distance.

I have previously checked that with Redarc Phil. It's perfectly acceptable to short the input to the output of the BCDC's for the purpose of Jump starting off the aux battery.

I just use a VSR, so assume all ok to set up to bypass that if ever needed ?

I have never heard the acronym VSR before now. From a very brief Google search I think that it is the same as a "solenoid" that most of us here are referring to.

I am not sure of your point so will explain one part.

You can over ride the automatic (turning "on") function of my Redarc solenoid by wiring in a manual switch. I use a toggle switch in the console in the cabin. When you turn the switch on it activates the solenoid and connects both crank and accessory batteries together in parallel, so that you have maximum available cranking, or winching, current.

Yes you can use a solenoid (another name for an electrically, not electronically, operated switch) in place of the Redarc. But to what end? Save money? Not worth it.

Sorry if I raved on if I misunderstood you Les.

Phil

Phil.

A VSR such as the Redarc SBi12 is not the same as a solenoid. It's a solenoid with some added electronics that detect a voltage over say 13.2V. It's a Voltage Sensitive Relay. In the application above, that will not work because it will always close ( short) when the alternator is running, bypassing / shorting the BCDC.

This application calls for a standard solenoid ( a relay if you like) that only closes when the button is pressed, eg when jump starting.

While a VSR, like the SBi12 can also have a momentary button input for jump starting, the application is different. Eg if you don't have a BCDC.

No drama Phil, the Voltage Sensitive Relay is a valid tool for dual battery setups, possibly the simplest setup that works well.
It suited me at the time, and still does, will research some more if switching to something else might be better if incorporating an override, or for when using a winch eventually . . . if I ever fit it :)

Tony

According to your comment "This application calls for a standard solenoid ( a relay if you like) that only closes when the button is pressed, eg when jump starting."

The accessory battery in that case would not get any charge unless the switch was on. Did you mean that?

I am aware of the difference between a "solenoid" and the Redard isolator. I am being lazy and just referring them as "solenoids".

A story about "solenoids";
The first computer that I worked on was in 1968 and called STRAD. It had a wopping 46 Kbytes of RAM memory in the form of streaming magnetic tape. WOW! It was basically a big room full of cabinets with heaps of "solenoids", that included automatic fantastic semiconductor devices, your voltage sensing relays, manual and magnetic gizmos. Thousands of them. If STRAD seized up we would actually kick the base of the suspect cabinet and "reboot" STRAD. And I believe it was the same throughout the industry. Hence the term reboot. Bloody solenoids - hate them after that job. However they do work and were all referred to as "solenoids" for ease of explanation to non scientists.

Phil

Phil, I had no doubt you would spot a solenoid from 50 paces. I thought the VSR terminology was new to you from your post though.

Phil said: "The accessory battery in that case would not get any charge unless the switch was on. Did you mean that?"

Yes I did mean that wrt a standard solenoid Phil. In this application ( ie the one referred to by the OP) the BCDC charges the accessory battery. The only reason the solenoid is there is for jump starting, or winching where the current is required to flow in the reverse direction from the Aux to the starter motor etc.

Why all the complexity.

A VSR appears to be simply an automated voltage sensing switch.

The Redarc SBi12 200 amp isolator is in essence "smart" relay (ie solenoid) that will switch on or off under control of a voltage sensing circuit plus a manual override.

In other words, to be "trendy", a VSR with an external manual control option. You lot will have me drinking coffee and wine next. Who was it that said "the get go" in this thread. Gee it's nice to talk like a Yank NOT. Yes - I am laughing.

People we are stuffing around with terms, adjectives and acronyms like smart and VSR that manufacturers sales staff have added and invented to make a sale.

Just like the meerkat word "Simples". Made up to make a sale.

Phil

I'm have no idea what you are talking about Phil.. Did you start that wine already?

Trendy? Coffee and wine? yanks? Meerkats? Simples?

HUH???

The Redarc diagram referred to by the OP has a BCDC and a plain old solenoid. No VSR. No Smart solenoid, It's this thread that made it complicated.

The redarc diagram is simple and works if used as described. That's all I know. A VSR, smart solenoid, SBi, etc won't work in this application.

I would consider that "VSR" is a typical acronym invented by the latter day trends to make more sales.
A simple VSR is nothing more than an electronically or manually controlled solenoid/relay. It can be a very basic cct board involving an op amp, a few resistors, a diodes or two and a few capacitors on a cct board, or a single chip with those components grown on it. I made heaps of them for safety sections on my train layout. No big deal. Voltage drops, chip switches and the output tranny turns a relay on or off. Simple.

That's where I had some fun and went OT and brought up the habit that sales staff have in inventing acronyms, words and sayings to simply help make a sale. Most of which are spelt incorrectly and imported from "yankland".

Don't worry about it. Lifes good. I was just having a bit of fun. I may exit now methinks.

Phil

RMD

I think the wire you are referring to is brown, not black. Brown is the output wire of a BCDC.

A Momentary switch is a classification for a push button switch that is only closed when you press it. It doesn't mean it is only works for a moment LOL. In this case you would press it "for a moment" while jump starting the vehicle from the secondary battery.

The source is Redarc, the manufacturer.

It all makes perfect sense to me unless I'm missing something.

I turned up my screen brightness and yes, the black wire is brown.

If the momentary is used ONLY for starting on the odd occasion, you could not buy the solenoid and put a battery isolator in there. Just turn it on to start and turn it off again if isolation is required.

So what is the test Zippo? Please explain!

No, I did say "test question" and not trick question for a good reason. And the fuse rating - if selected in accordance with Redarc's suggestions - shouldn't enter the discussion. (Nor should the alternator connection, unless someone want to place it other than to the cranking battery terminals.) It was to survey whether others saw it as OK or problematic.

Note the title of the Redarc PDF file - "the-ultimate-dual-battery-setup".

I'm in the same boat as Boobook - I did ask Redarc the same question some time back (although I had no plans to do it at that time). They advised back then that it was OK to bridge the input and output of a BCDC unit of the types listed on that diagram ( I use a BCDC1220-IGN). But recently that diagram came up again in discussion, so I emailed them.

I had been waiting, holding off responding until the Leigh or AllanB types made a comment, and for a further reply from Redarc. But I will throw in my 2p worth here anyway.

The DC-DC charger will be trying to output the voltage for the stage of charge of the auxiliary battery, for the sake of argument pick 14.1V in boost. The main/cranking battery can be whatever it is at the time.

Now you parallel the two batteries via the solenoid. That dictates that their terminal voltages are the same (excluding volt drop caused by current flowing BETWEEN THEM). So now you have the BCDC trying to deliver a set voltage to a pair of batteries that are feeding it.

If the alternator is (a) not running - you're trying to "jump-start" from the aux - or (b) not delivering that 14.1V figure, then the BCDC will be outputting its max output current trying to lift the two batteries to 14.1V FROM THOSE SAME TWO BATTERIES. Almost a perpetual motion machine but with losses of course. (If the alternator output IS above 14.1V I'd expect the BCDC to accept that without drama, although again I don't know as it would try to go to a float voltage.)

To quote Phil above: "But that doesn't sound logical to me. I don't know if that is a problem or not." Those were my thoughts, as the discussion I saw recently related not to jump-starting but for WINCHING.

When I put the question to Redarc last month: "Can you please assure us that the configuration shown in that diagram is definitely safe and functional." their reply - which I won't quote verbatim as I don't have that permission - was that it was an error and the models listed were incorrect (for that task?). While they hadn't tested it, they couldn't assure it was OK.

That's where it sits. I don't know, Redarc have clearly seen a problem now, and I for one won't be trying it out and risking the magic smoke getting out of my BCDC. If I hear any more from Redarc I will update this thread.

From a purely theoretical point of view:

I'm assuming the inputs and outputs are isolated in the Redarc as they are in my Enerdrive, connecting the input to the output should not cause any problem.

Think of it this way the input side of the DCDC charger is isolated from the output side, just drives a transformer, no different than any other load being connected to the battery lights etc.

The output side will act like a battery charger, and raise the battery voltage upto whatever it decides is appropriate if it can, it doesn't know its connected to its input it just a battery, same as connecting an AC charger to the battery.

As there are losses in the charger it will eventually flatten the battery trying to charge it / maintain the charge. No damage should occur to the unit as the overload protection should protect it.

I was recently setting up an Enerdrive unit, pain in the bum as you must have input voltage on it to program it. As the unit is mounted in a van and it was inconvenient to connect the car I just connected the input to the output, charger didn't start charging anyway as it needs to see alternator voltage be for it will fire up but even then I don't see it being an issue.

The input and output have a common earth Leigh. Therefore I can't see how they are isolated, but I agree there must be overload protection somehow.
I have concluded that shorting the input and output is electrically the same as when the two batteries are coincidently at the exact same potential. Current limiting and protection takes care of it all.

Yep negative is common, positive obviously has to be isolated, the max current will be limited by the chargers output capacity, ie its constant current stage.

From what I have read many use a a similar setup for jump starting without any issues.

Tony, I agree that when they are coincidentally equal (I/O voltages) there is no issue. Otherwise the least that I'd expect with bridged I/O is the unit would sit there on current limit trying to lift itself by its bootlaces.

Leigh, I have used the output (aux battery) to feed the IGN lead in the -IGN unit before now to "transfer" some charge without running the motor. The BCDC doesn't know or care where the IGN feed originates.

Anyway, it will be interesting to see what Redarc's final view is.

Ok, apologies, I really thought this was a test to see if we could spot what was wrong - because there really seems to be a problem with this circuit.
First, I agree with HKS and others - I've used this same output-to-input test on DC-DC chargers to see how they go under maximum load (the charger current-limits at its max). So I agree there'll be no damage to the DC-DC charger - so no problem there.
But the reason I pointed to the fuses is this:
The solenoid is there to give us an emergency jump-start capability, so we need to look at the starter-motor, which is connected to the start-battery. Because the start-battery is flat, the starting current is going to come from the Auxiliary Battery. That starting current is going to flow straight through those fuses, rated at 40 or 60 Amps each (depending on the size of your BCDC). The starting current is up around 200 Amps. See the problem?
It will take about a second or two to blow those fuses, which puts my DC-DC out of action, until I notice it and replace the fuses, if I have spares.
I'd hardly call this The Ultimate Circuit - what d'you reckon?
(it's also the reason they don't fuse starter motors)

AJC, I'd agree it's not the b-all and end-all. Yes for jump-starting the fusing would be an issue that would be hard to avoid. And the same applies to winching duty, the current-time product would be a problem.

Zippo - absolutely: do I want that winch to get me out, or do I want its breaker to go? (before I get to safety). Tough choices indeed!
Be really interesting to see how Redarc replies.

With such a setup even the VSR won't be happy if you try and crank off the aux straight away, my thoughts are that you link the batteries then allow a few minutes for the batteries to equalise before trying to crank the motor.

I Jump start using a 200A / 600A surge VSR, and have 250A fuses to each battery and 2 B&S cable. It works like a charm in my V8 diesel even with a very low cranking battery and glow plugs working due to cold weather.

It's not an issue if designed properly.

The redarc circuit is fine.

Could someone please tell me what a get go is?

From the get go generally means from the start.

I agree Gramps, I will just get a longer set of heavy duty jumper cables.
Disconnect the winch and don't go where I'll get bogged.
Much easier me think.

Cheers.

Hopefully it's this easy Gramps.

If you want to set up a push button Jump start with Redarc's BCDC product, then do it exactly how they say on their website, and ignore everything on this thread.

If you are happy with jumper leads, then ignore this thread and Redarc's page

I think it really is that simple.

I really don't see the point, how often do you need to jump start your engine, if more than once in a lifetime then maybe you need to replace your cranker more often or stop leaving the lights on etc:(

I always carry a set of jumper leads, if I should need to jump start (haven't as yet)
it is a simply a job of jumpering the two positive terminals and away I go.

As for winching, my winch is connected to the aux, I don't like the idea of being stuck in a river with a flat cranker and no way to start the engine.

Everyone is different I guess Leigh. Sometimes you don't know you have a bad starter battery till you get into the high country in winter etc. Or something fails on a 4 weeks trip. Then it is very handy. For an almost zero investment some, like myself would do it.

Also, to start another useless discussion, I wouldn't generally advocate using the aux battery for winching for a number of reasons.
-Many Aux batteries won't like the high current - 500A plus.
-The main battery will recharge quicker and has the alternator connected to it - less voltage drop.
-If people have a BCDC then they are limited to 25 or 40 A recharging.
-Being on the "wrong side" of an isolator, it's current draw may exceed the limit of the isolator. Eg a Redarc has a rating of 100A continuous, or 400A for 4 seconds. Winching could go for many minutes with 500 or more amps. ( some of the current will come from the main battery and alternator, especially after the isolator kicks back in.

I am sure if you know what you are doing in the set up, then it's fine but this thread shows that is a very small minority LOL.

Those of us with PX Rangers and their BT50 cousins are probably more practised at jump starting than owners of other brands LOL

Due to the peculiarities of the Ranger/BT50 electrical systems it is dead easy to flatten the rather crappy OEM crank battery :-( Mine has been flat about 8 times in the two years since new and of course died an early death. It's been replaced with a stop-start battery which is much more robust.

My second battery is in a compartment in the canopy at the back, not readily accessible, so I have set up my cabling so I can crank off the second battery and winch off either the crank battery only or both if I need to, but not soley off the aux. I have started off the second battery, well, about 8 times :-( but haven't had to do that since the cranker was replaced and I found out more about how to manage the electrical system .

I chose to winch off the crank battery because it's designed to deliver and accept high currents and is supported by the alternator (120 amp, I think), whereas the second battery is an AGM deep cycle and prefers lower currents, so it is supported by a DC-DC charger and therefor doesn't get the full boost from the alternator.

Yes setup needs to be designed for the application, my VSR is rated at 200A plus and has overload protection, when I select winch it disables the VSR to prevent overloading the alternator and protect the cranking battery. My aux is rated for use as a starter battery.

We all have our preferred setups.

Frank P,
Here are some figures that I have just recorded of my original ranger battery and a new one. Charged both batteries the new one on the 22/4 and the old one on the 23/4 with a check 15a charger. The new battery in the vehicle and the old one on the floor. I also had the circuit breaker open on the aux battery and the smart charge has always been disconnected. Vehicle is an auto and was left locked during the recorded voltage readings.

Both batteries settled down to 12.92v for the new battery and 13.1v the next morning. After 12 days the vehicle battery read 12.6 volts and the old oem battery read 12.66v.

Just thought you maybe interested. I just did it to see how the old 2012 battery stood up.

Thanks Eagle.

I didn't take any measurements.

The 2014 BT doesn't have the Smart Charge system that the Ranger enjoys, so that was never an issue. When the OEM battery repeatedly couldn't start the car after having a minor load applied for a short time, or after a cold night, it had to go.