How smart is the isolator??
Submitted: Tuesday, May 25, 2010 at 17:20
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Does the isolator know if the batteries are being charged by the alternator or a charger.
I put the smart charger on the auxilliary for a once a month boost (actually this is the first time for the current auxilliary. The last one recently died aged 8 years) and noticed for the first time that the cranking battery is also getting charged. Probably a "
well derrr" but I did not think they would connect and have never checked it before.
Does this happen with most isolators that the gates will open no matter which battery the charging voltage gets connected to? Would there be any benefit putting the charger onto the cranking battery instead or even placing on the negative of one and the positive of the other. Should I disconnect them and charge only the auxilliary given they are different sizes and age.
Reply By: Member - John and Val - Tuesday, May 25, 2010 at 17:52
Tuesday, May 25, 2010 at 17:52
Doesn't sound right. Depends on the isolator, but I wouldn't expect it to know that charging voltage is available at the auxilliary and try to charge the cranking battery.
I would NOT connect the charger's positive to one battery and negative to the other - both the negatives should already be tied together via the chassis anyway (so that connecting to either negative is in fact connecting to both), but the charger positive should be connected to the battery you intend charging.
If it's a solid state isolator, perhaps it was triggered on a once only basis by some voltage spike (such as could occur if the charger was running when connected to the aux battery, or perhaps during installation of the new battery?). Could also be that it's died and is connecting the batteries permanently together, something you may not notice in normal use.
John | J and V
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Reply By: Sand Man (SA) - Tuesday, May 25, 2010 at 18:32
Tuesday, May 25, 2010 at 18:32
Spade,
Interesting post mate.
In my opinion there are "dumb" isolators and "smart" isolators.
In fact, I wouldn't even call a "dumb" isolator an isolator at all.
I once put a query to the technical department at Piranha re the DBE150S Isolator I owned and received a reply that this (smart) isolator kept the primary and secondary batteries electrically separated from each other at all times.
This is exactly what I would expect from an ISOLATOR and not "sometimes" having them connected to each other and sometimes not.
Bill.
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Follow Up By: Mike DiD - Tuesday, May 25, 2010 at 21:45
Tuesday, May 25, 2010 at 21:45
"received a reply that this (smart) isolator kept the primary and secondary batteries electrically separated from each other at all times. "
. . . . ummm, how is the Auxiliary Battery going to get charged ? What is the "Isolator" useful for then ?
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Follow Up By: Sand Man (SA) - Wednesday, May 26, 2010 at 07:39
Wednesday, May 26, 2010 at 07:39
Mike,
The primary gets first shot so to speak, then after the Piranha has determined that it has reached a certain voltage level, it swaps over to the auxiliary.
The electronics in the isolator control the changeover (and change back when necessary) but the two batteries are isolated from each other at the relay. Therefore they are never paralleled together and a flat auxiliary will not drag down the voltage in the primary (and vica versa).
I would assume all "smart" isolators work on a similar principal.
Bill.
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Reply By: ChipPunk - Tuesday, May 25, 2010 at 21:39
Tuesday, May 25, 2010 at 21:39
Every car is fitted with an isolator the Sand Man describes. Fit a battery anywhere and it remains isolated at all times - exactly as per "the primary and secondary batteries electrically separated from each other at all times".
Yep - very smart indeed.
But many prefer practical isolators that keep batteries separated but allow both/all to be charged.
Lots of ways to do this. Some even purport to involve "microprocessors" - now that's hi-tech - way different to normal analog electronics or circuits that others use. They may even be using 32-but architecture now.... just for that ultra-fast intelligent response.
Alas I have my cheap simple isolator (relay) that doesn't have the above problems.
But as per J&V and Derek wrote, most isolators do not "sense" the 2nd battery(s) unless they are still connected.
If those isolators are connected the wrong way around, the they would probably never connect except when being externally charged.
But there are dual-ended sensing isolators - though they tend to be equalisers and converters (dc-dc) whether with or without isolation.
And chargers should be charging across one battery (except maybe for "balanced" matching parallel connections with diagonal power feeds).
Remember - systems are designed with battery voltages in mind (ie, 14.4V, 13.8V etc) - not dash or load or alternator voltages (within reason of coarse!).
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418145