Simple second battery connection

Diamond I take it the above setup means the spare battery is only in use when the ignition is off - and the main is used when driving? When does the charging happen for the spare? or are they both on when ignition is on? Would the above setup mean my radio and clock etc would have to be reset everytime the car starts?
I ask all this as I want something similar to above but had figured an isolator switch was the easiest way to go, just swap back and forth every couple of months or so.
Any help would be great.

gday slammin.
when your ignition is turned of only the second battery is being used so you have all your accesory conected to it spottys/winch/fridge ect.
once your car is running the solinoid opens so both batterys are being charged.you normal every day car functions clock ect will not be affected.and problem with isolater switch if something happens when your camping and yopu forget to switch it you run the chance of flatening your main as well.ive had mine 2 yrs no problems and $30+wire isolater switch probly cost nearly thatšqUC3<BuIL

Bob
Post ID 5991 (July 14th) in the archives covers some of the debate/aspects that you are interested in.
I have used the solenoid setup as I described in there and have been very happy with it and with no problems so far.
The offer a diagram is still there.
The issue of correct charging of batteries for longevity is also worth a search.
Do an archive search though to satisfy yourself.
Cheers
OskarMrs Oskar on Big Red

Hi Bob,

I'll happily agree that some systems are overpriced, but there is more to charging a battery than simply having a switch, or an automated switch using a solenoid.

For example, some battery management features that come to mind that are readily available in many good battery management systems are:

1: Isolate second battery from main battery when vehicle engine is not running so that you don't flatten your main battery when running accessories. (this is about all the solenoid or switch is capable of).

2: Sense the level of auxiliary battery and cut - out if level gets too low to prevent total discharge which can damage a battery.

3: Sense the level of main battery and only allow a charge to be passed to the second battery if the main battery is fully charged, thereby ensuring that your main starting battery is always at it's peak.

4: Sense the voltage level of the second battery, and if the level is low, allow a trickle charge to slowly bring the battery up to a point where a full charge can take place without damaging the battery.

5: Apply a full charge when second battery has a sufficient state of charge to safely accept it.

Anyway, that's why I will be fitting a battery management system to my vehicle instead of just a solenoid. This will give me better battery performance, longer battery life, and always ensure that my main battery in in a good state to charge the vehicle.

There is obviously alot more to charging batteries, and it IS a science, but having said that - like I said in my previous post, a solenoid will do A kob - just not the BEST job :-)

If that's what you want - go for it.

Cheers,

Luke.

OOPS....

>This will give me better battery performance, longer battery >life, and always ensure that my main battery in in a good state >to charge the vehicle.

...that should of course read start the vehicle, not charge the vehicle :-)

...and kob should of course be job....

apologies for any other typos :-D

Luke
You are correct of course about each of these points and I have no argument with any of these.
My personal preference, however,is "simple is best" and thus I only have a couple of points to trouble shoot if a problem occurs and there are no electronic bits for me to "wonder" about. The cost is not an issue I just can't help myself D.I.Y.ing.
Besides I make it my business to know what's happening "under the bonnet" anyway so the simple system suits me fine.
I agree that the store-bought systems are best for most people whether they are technically minded or not.
Don'k worty aboit the typo's we kbow whar you meam.
Cheers
Oskar

Mrs Oskar on Big Red

G'day there Oskar,

I understand people liking simplicity, and DIYing - I'm an avid DIYer myself, and like to do as much as I can myself on my GQ shorty.

I like to muck around with electronics too, and recently built an electronic ignition for my GQ SWB which is working brilliantly. I've also built a solid state battery management system based on an Electronics Australia (now Silicon Chip) circuit. It will be installed with some additional safeguards to circumvent the well documented potential reverse current problem.

Total cost for my Electronic ignition - around $60 bucks :-) and IF it fails, I can return to standard points while out on the road in about ten minutes :-)

Total cost for my battery management will probably work out to be in the order of $120 +/- fully installed with all cables etc (not including the cost of a battery tray and second battery).

The solid state system will theoretically be more reliable than the mechanical operation of a solenoid, which can be prone to failure after a period of time, as well as having all of the extra functionality and safeguards. The problem is that when it (the solenoid) does fail you will generally not know about it until you need the power and it's not there.

If my battery management fails it will let me know immediately.

Anyway, each to his own - if you like simplicity, that's fine. Like I said in my first response to this thread, I just think it's important to know exactly what you will and will not get with a solenoid Vs a solid state battery management system before you make up your mind.

Cheers,

:-)

Luke.

Luke
I like your style.
Keep it up.
OskarMrs Oskar on Big Red

Luke
BTW what system are you considering?
OskarMrs Oskar on Big Red

Hi Oskar,

The base kit I have built can be found here:

http://www1.jaycar.com.au/productView.asp?ID=KA1782

I'll be adding some modifications and improvements as I go along...but nothing major - it's really quite a good kit.

There is one potential flaw - which is the possibility of a reverse current leakage from second battery back to main battery via the FET protection diodes, but this can only happen under certain conditions which under normal circumstances should not present themselves.

I may take steps to provide absolute isolation to guard against this though - still undecided on that one.

The reverse current 'problem' with this particular management system actually has potential gains also if the condition of the main battery is insufficient to start the vehicle but the second battery is in good condition - but that's another story :-)

Anyway,

Cheers,

Luke.

On a lighter note.........
Some guys I know in the heavy duty electronics business sometimes refer to FET's as Flame Emitting Transistors.
When they do go "poof" they go "BANG"
Have fun
OskarMrs Oskar on Big Red

Hi Terry,

I think whether the alternator is going into float mode isn't really important here. What we have is the second battery connected to the primary battery by means of an isolator switch/solenoid, or solid state management system.

When the primary battery is fully charged it is used to supply a charge to the second battery, the alternator will charge the primary battery as appropriate - ie: the level of the primary battery will be kept at an optimum level via the normal operation of the alternator, whilst the secondary battery is kept at an optimum level via the primary battery.

If the alternator went into float mode, and only a trickle charge (less than the current drain) was applied to the second battery - then the battery management systems would be useless (which they certainly are not). Indeed, they work very well.

Anyway, that's my understanding - what are others thoughts?

:-)

Cheers,

Luke.