Thread: Aux battery sugestions

For the OP.....

130Ah AGM battery off fleabay $200
Narva marine isolator off fleabay $30
Battery box with volt meter and multiple USB, cig socket, Anderson outlets off fleabay $100
Cabling from local auto sparky $50
Dirty old Disco 2 alt, no solar.

Been running 50L fridge, minimal LED camp lighting, charging phones, tablets etc for up to 5 days without driving.

Originally Posted by rangieman

Ok ill chime in here as my car came fitted with a redarc no offence To tim as i have used your gear on cars ive set up in the past
My Redarc will kick in charging the second battery normaly with in seconds of start up after a night with the engle running of the aux batt .

Now i have not done the heavy winching you do but honestly to me it does sound like you have issues somewhere else .
As what you are describing does not add up .

Any suggestions where, Regards Frank.

Originally Posted by drivesafe

Hi Tank, depending on how old the Redarc is/was, newer units cut-in around the 13.2-13.4v.

This is low enough to allow for low voltage operating alternators, and you should have been getting power to your auxiliary battery in no more than 30 seconds.

Again, there is something not right with your electrics, but I can not give you any real assistance because you need to get a lot of voltage readings at different stages of your trips and at different places in you setup.

This is no more than an UNEDUCATED guess, but the problem seems to be with the supply coming from your alternator.

Just a suggestion, have you checked all the connections, including any motor to chassis earth straps/cables?

Supply from alt. is 13.8 at idle and over 14 at revs, I'm fanatical about proper earth connections, Thanks again, Regards Frank.

Originally Posted by Tank

Supply from alt. is 13.8 at idle and over 14 at revs, I'm fanatical about proper earth connections, Thanks again, Regards Frank.

In that case then, (and like rangieman said too), the Redarc will kick in after about a few seconds after start up.
As soon as the redarc senses more than 12.7v it connects the aux battery.

Did you wire in a manual override switch too?(and an LED).

Once the main battery has dropped below 12.7v(ie. 12.6v or lower) the redarc will isolate the batteries.
if the main is a bit low(eg. 10v or whatever) you hit the manual switch(if fitted) and it holds the two batteries connected for a jump start.

I agree with the other comments that something isn't right if your alternator couldn't charge the deep cycle aux battery in about one hour.

Hi AK38, the Redarc cuts-in at around 13.2v and cuts-out at around 12.7v.

All VSR type isolators deliberately cut-in and cut-out at different voltage, otherwise, when a motor is turned off and the batteries settle, once the voltage gets to around the 12.7v mark, the isolator would rapidly turn on and off until the voltage dropped below 12.7v

Tank, just another possibility, try testing your isolator and see when it actually does cut-in and cut-out.

If for some reason the settings in your isolator have drifted up, then this would account for the strange operation.

NOTE, a poor earth connection on the isolator itself can cause the cut-in and cut-out settings to drift up and sometimes, not work at all.

Originally Posted by drivesafe

Hi AK38, the Redarc cuts-in at around 13.2v and cuts-out at around 12.7v.

...

Ah, OK.(makes sense too). Didn't know that(and it doesn't say anywhere on all the paperwork I have for it).

I've never seen below about 13.4-13.5v with the car running, as I probably don't have enough accessories to put such a load on the battery.
driving lights are LEDs(180w). I think an Engel draws about 4-5A IIRC, so that's even less than the driving lights, so no point in borrowing one to push it to see.
I know that they've built a delay into the box's brains, so that it only ever connects after a few seconds after start up.

I thought that the way it works was the way Tank explained it, in that it first allows charge to the starting battery and then it sends charge to the aux after main is at a certain level.
But from what I've noticed, the other week when I had to run the car with no alternator. One of those days it rained all day, I had to drive for a few hours in the rain with wipers lights etc, and by the time I got home main battery was down to about 11.9-11.8v.
Aux battery basically unaffected still at 12.6-12.7v.
When I got home I hooked up the charger to the main battery of course; charger immediately settled at about 14.7v and within about 5 sec the redarc lit up too and charged both batteries because the aux shot from 12.6 to 14.7v too!

Originally Posted by AK83

I thought that the way it works was the way Tank explained it, in that it first allows charge to the starting battery and then it sends charge to the aux after main is at a certain level.

Hi AK83, a number of dubious VSR suppliers either attempt to imply, or just lie and say their particular brand of VSR isolator does not start charing the auxiliary battery until the cranking battery is first fully charged.

Not only is this a lie, it is totally unnecessary in the first place.

By implying that an isolator does not turn on and start charging an auxiliary battery, is an attempt to make the isolator look like it is some very clever piece of equipment but the reality is that now days alternators are so large, that they are capable of charging a number of low batteries at the same time and still meet of the power requirements of a vehicle.

The truth is, VSR isolators turn on ( cut-in ), depending on the vehicle, with in seconds of the motor starting. Even when the cranking battery has been so low that it could not start the motor and the vehicle had to be jump started. Seconds after the motor is started, the isolator will have turned on.

Tank, in your case, something is just not right.

There is no way that with a healthy alternator and a correctly operating isolator, that it would have taken up to 30 minutes for the isolator to turn on.

While on the subject of porkies, this is another one that does the rounds on a regular basis.

Originally Posted by Tank

Alternators Do Not Fully Charge Vehicle Batteries Most of you will be shocked to know that your fully charged car battery is only about 80% charged.

There are lots of vehicles running around with cranking batteries at 80% and lower. But the low battery is not cause by an alternator being incapable of fully charging the battery, the problem is that the owners of these vehicles don't drive them long enough to allow the alternator to do what it is designed to do.

When ever you hear or see someone making these claims, you can be sure they are trying to sell you something you never needed in the first place.

If you have a low auxiliary battery and you are doing lots of short drives, then a DC/DC device is the last thing you want as it will actually chock the charging capability of an alternator.

Again Tank, in your case where the DC/DC device is actually charging the battery better than with out it, with the size of cabling you have, everything is pointing to there being a problem.

Thanks for that drivesafe.
It's kind'a what I thought I knew about what I have.

ps. the only reason I have this Redarc SBI12, is that my brother bought it(S/H) a long time back to fit to his Patrol.
He sold the Patrol and had it sitting doing nothing.
After joining up here and various readings of lots of stuff, I was 99.9% convinced that I was going to get one of your products.
Anyhow a few weeks back bro was clearing out stuff and snaffled the Redarc.
The handy part of it was that it was purchased with so much extra stuff that it made the cost of actually fitting it close to zero.
I purchased new battery terminals and cable lugs to have what I wanted.

All cabling(4AWG) was good quality and plenty of it(I have a ton of it left over).

About 20 or so years ago I remember building a aux battery charging box from a kit published in Silicon Chip. I fitted that to my RRC to have an aux battery for a trip up the guts.
I do remember that kit was of the type to charge main battery first, then the aux battery.
As long as the main battery was in good health the aux battery got a good charge within an hour or so.
I tested it to see what'd happen if main was low on capacity, so I replaced my good battery with a dead one(my father had) and went for a drive.
I constantly stopped every 10-15mins to see how the indicator was showing. It had an orange indicator for aux and a green one for main.
It worked basically as stated.
Main battery was still showing on and aux was still off for about the first 20-30mins.
I can't say exactly when the aux indicator light did come on, but it eventually did.

ps. I don't think Redarc have any data indicating that their SBI12(100 amp model) are smart type DBS.
They simply state that it isolates the aux when the a min reaches a min voltage of 12.7v.
That's about it.
The other option is that you can manually hook them up(jump start) if you use the optional momentary push button switch.
Push the button(just a momentary push, not push and hold) and they connect for a few seconds till you start up.
I've never timed it, but it feels like about 5 sec or so.