Thread: Dual Battery

Originally Posted by scott oz

Great debate.

Curious I’ve got an “IBS” (?) controller. Had it a number of years and it just sits there, I think, doing its job.

My average drive would be 40 minutes to work each day in city traffic and 40 back. I avoid the short trips.

So my question is how long “generally” does it take to recharge the cranking batter after starting?

Hi Scott and let me guess, the operating info that came with the IBS states that it charges the cranking battery first and then charges the auxiliary battery ( I haven’t read their literature ).

Most dual battery isolator manufacturers make this B/S statement but what actually happens is the isolator measures the voltage on it’s input terminal.

Once the motor is running, the voltage on the isolator’s input terminal will rise and once it reaches a set level, usually about 13.2v, the isolator will either switch on or it will start a short time delay, ( usually no longer than about a minute or two ) and the switch on.

Very, VERY few dual battery isolators have any idea of the state of charge of the cranking battery, they act on the voltage levels the alternator operates at.

So Scott, in your set up, you isolator should be switched on ( cut-in and connecting the cranking and auxiliary battery together ) within a few seconds to a minute or so after you start your motor.

But as to how long it takes to charge your cranking battery, it all depends on how high or low it is when you start your drive.

But on average, with a fully charged cranking battery when you started your motor, a 15 minute drive will replace most of what you used to start the motor.

Originally Posted by DeanoH

Not what I'm saying Dave.

The electrical /chemical characteristics of a lead acid battery are the same regardless of its application. Though in automotive applications heat and vibration play a greater part than in a static situation. Just as electrolyte stratification is a real issue in static instalations but not in automotive. But the battery's characteristics are the same.

A bit like saying, the Puma and TDi engines are the same in respect that they both require the same fuel/air ratio to compress for maximum combustion efficiency. I'm not a diesel mechanic so hope that's a reasonable analogy?

Deano

Deano

no offense mate but no, in the respect that I ment it, thats not a close anology. (but I think i understand where you are coming from with it)

the mechanicals of both engines are of the same generic design, being a 4 cylinder 4 stroke diesel with a turbo. Even though your not a mechanic I could show you the turbo from either engine and you would identify it as being a turbocharger. Its the same with batteries now.

assuming you were a layman, If I showed you a battery from the long discharge bank at ATC on amberly you could identify it as a battery because its got some similar design features, a positive terminal, a negative terminal, casing and caps. If I sectionalised one you could identify its internal parts. But just by looking at it you probabley couldnt tell me how to charge it correctly. you could tell me that yep, whack an X volts charger on and it will charge and it would to about 30% capacity.

batteries generally all look similar and at the end of the day they all do the same thing, provide the power to start the vehicle and hold a reserve of power to keep things going while the alternators not working. Generally speaking if you whack an old school charger on them they will charge but they wont all charge correctly.

To tie it to the diesels example the tdi300 is a mechanical engine and runs a lower boost pressure than the puma, it also doesnt come on boost as quickly so needs to be driven a certain way to be most useful to you. If you drive the puma which is an electronically controled engine with a different turbo and injection system the same way as you would drive the tdi300 you would kill the fuel economy of the engine, shorten the service interval and potentially shorten the life of some engine components. The engine would still work and it would still do what an engine is supposed to do in terms of moving the vehicle but it wouldn't be the best way of doing so with the setup on hand.