View Full Version : What is the benefit of a Perko switch, over an Isolator?

ian ashton
04-29-2010, 11:23 AM
Why does everyone seem to choose the Perko switch over an isolator? It seems like an isolater would be way easier, without having to screw with the switch position and all that. Is there a major benefit to the switch, other than the switch is cheaper?

04-29-2010, 12:07 PM
I think part of it is the fact the Isolator is harder to use with a Wall charging system at home. Not positive but i think thats is.

I was about to pull the trigger on this a few months ago. Now im on the fence as to what i want.

I dont like switching my Perko all the time but then again i understand it, im comfortable with it and it works lol.

ian ashton
04-29-2010, 12:25 PM
I'm just lazy, I'd rather it be automatic. I never charge my battery manually (unless its out of the boat and on a trickle charger), so that wouldn't be an issue for me. I think I'm going with the isolator.

I also don't need a 'dead' switch, since I leave my boat in the water and need the bilge to work at all times. I've never had an issue with killing the battery either, so I think the isolator is the way to go, I just want to make sure there isn't some huge reason I'm missing.

04-29-2010, 12:44 PM
I have been told that one downside is that if you are on lake and isolator goes bad you will not realize until its too late and both batts run dead.

04-29-2010, 12:54 PM
I have been told that one downside is that if you are on lake and isolator goes bad you will not realize until its too late and both batts run dead.

Well i guess that could be the case but then i personally have never seen one go bad, or heard of it. I've had ISO or ACRs on every boat and wouldn't do otherwise. All it takes is for you to forget to switch just one time and you could potentially be stranded.

I too never worry about charging batts in the boat when not running, don't see the need nor do i want to have to mess with a Perko, just a pain in the rear. It might be that for the guys with overkill stereos and huge battery banks shorepower charging is neccessary to keep all that topped off. But then a high end alt like a Balmar would keep them up too, that is unless you spend more time playing your stereo than actually boating.

04-29-2010, 01:13 PM
I just installed the BlueSeas ACR as per Razzman's help (shoutout!)
Anyhow, for me that seemed the best way to go!

And what's the big deal with charging the batts with the isolator? Can't you just hook up the charger to one battery and the isolator will detect it and charge both at the same time??

04-29-2010, 02:16 PM
From what ive read and im no expert on Isolators due to the way they charge and protect the starter battery you have to have a On Off type switch to run a house charger on them.

They work by once the Start batter is charged 100% then it allows the secondary battery to charge. A house charger will since the Starter is 100% and shut off and this will not allow the Iso to switch to the secondf battery. If you connect to the second battery then thats how to charge it but then you will still have to manualy put it on the first battery as the isolator wont switch it.

This is what i understand from the posts on other forums and from reading about multibanks battery systems like i have and the troubles with charging at home with a Iso installed. This is whats keeping me from pulling the trigger.

I dont want to make my charging difficult, yet i also dont like switching my Perko.

04-29-2010, 02:36 PM
Mike that is only the issue with charging at home right? If that is the case then no issues since you should be on the water and not at home.

you da man
04-29-2010, 02:37 PM
I use a Perko on my boat (3 batteries) and don't find it a problem to switch it. I have a Promariner onboard charger and store my boat in an enclosed storage unit with power and timer.

04-29-2010, 03:23 PM
I use the simple method. If i know that i'm not going out for 3-4 weeks then i simply make sure the ACR switch is off (which it always is) and connect two trickle chargers to the batts, plug them into a gang plug, connect an extension cord and run it into the garage. Done. Hurts nothing, no issues and the batts stay charged. Some people will say trickle chargers don't do the job ... I say BS! They are maintainers and automatic only allowing a charge when needed.

I use the battery tender jr brand and they work fantastic. They have a quick connect harness that stays on the batt so connection takes seconds without even taking the box cover off. In fact that's the same charger H-D uses re-branded and i've used one of those for years on the bikes. I would average 5 years on a Harley AGM batt, almost unheard of, all due to maintaining.

There was a thread on WW a couple years ago where "G" (who has 5-6 batts) simply installed a bunch of battery tender jr's into a plastic box, hung it over the boat and plugged them in and his batts stayed perfect. His system has four ARC amps, three subs, six coax, tower speakers, two playback LCD screens, etc. You get the point. He did find afterwards that his alt couldn't keep them all charged so he added a Balmar 160a alt later.

Long post but that's the reason i don't see the need for a big onboard charging system. To me, and let me quantify this is just my opinion, they are just more for the bling factor. Somebody started adding them to wakeboats and now it's one of those must have options. Again just my 2 cents worth and opinion.

04-29-2010, 04:21 PM
Rather than use the term 'isolator' which is often confused with a diode-steered device, I use Automatic Charging Relay, Voltage Sensing Relay or Combiner/Separator. The benefits are:

Its automatic and therefore convenient.
It can protect your alternator from abruptly seeing an inordinate load.

The cons are:

ACR & VSRs manifest in a number of wiring schemes according to the individual manufacturer. Many of these schemes are suitable for preserving the starting battery against drain while using instrumentation (chart plotter, fish finder, GPS, etc) that draws very little current. These schemes often contradict what is really needed for large audio system usage. You'll note that ACR/VSRs are not usually used in circuits applicable to trolling motors which closely parallels a large stereo at rest.
Oftentimes, low voltage will keep the relay or solenoid from closing or staying closed which results in a lack of alternator charge and deeper cycling which reduces the stereo battery lifespan. An ACR/VSR makes an AC shore charger essential.
None of the ACR/VSR manufacturers have a scheme to facilitate the use of an AC shore charger. They expect two battery banks to be charged via a single-bank charger or the ACR/VSR stays closed with high voltage thereby circumventing the individual battery bank profiles and charge program.
ACR/VSR schemes must be flexible to fit the system size. There isn't a single prescription that fits all systems. As the stereo current draw increases, and as battery amp/hours increase and depending on the size of your alternator, your design should be altered to fit the situation.
Many of the ACR/VSRs are dual-sensing rather than using a directional priority charge system. And this dominoes into additional complexities.
In most cases you have to supplement an ACR/VSR with some form of switch or additional relay to provide a.) emergency bypass, b.) AC charging isolation and/or c.) elimination of small current draw while the boat is in storage. Again, it differs with each system.

In summary, my take is if you're doing it on the cheap or you don't have the tolerance for the added technical issues then just stick with a simple switch. Know when to connect the stereo bank to the alternator in order to strike a predetermined balance between preserving your alternator or extending your battery(s). Keep in mind I'm still a major advocate of an ACR/VSR if you're going to do it right.

Earmark Marine

04-29-2010, 04:24 PM

I regularly talk to 'G' (Grant West). He has seriously changed his tune related to AC charging and no longer prescribes to using 'tenders'.

'Tenders' are fine for motorcylces, ATVs, UTVs, seldomly driven weekend cars, etc. They maintain starting batteries (not deep cycle) that are put into storage in a fully charged state. However, deep cycles that are seriously discharged are another story. Issues of desulphation are well cronicled everywhere. Check in with any boat dealer who sells tournement fishing boats. They don't use 'tenders' on trolling motor banks because the batteries don't last as long. Its not just about restoration speed.

Earmark Marine

04-29-2010, 05:12 PM
However, deep cycles that are seriously discharged are another story.

David your right there, one should never hook any seriously discharged battery up to a tender and expect it to do the job regardless of what it's in. A tenders purpose is, as i said, is maintenance and not meant to restore any battery seriously drained. If one were to use a tender, like i do, i always make sure my batts are up to speed before connecting to the tender. And i do that by using the boat or i top them off with a higher amperage charger at home after. They're out of the boat off season and stay on a tender all winter out of the cold. Consequently i'm on year three with the same batts without issues with a personal best of four.

Now that being said i also do realize that some people load their boats up (just like cars, RV's, etc.) with all kinds of audio gear and goodies pushing the limits of the system and then have to make amends for doing so, like not paying attention to details like batteries but i also feel some of the stuff being added these days is just overkill too. Just my opinions, i learned years ago (dating myself) when batteries were nowhere near as good as now and AGM was a dream how to take care of them and make them last. Try running race cars and track trailers on deep cycles long term and see how long they last! ;)

05-27-2010, 04:26 PM
12v 80amp relay hooked to the accessory position of the key switch is the way to go.

06-02-2010, 05:12 PM
I second the relay but I would use the RV isolation relay for about $18 and wire it to the ignition with a disconnect switch. Keep the relay away from areas that may accumulate gas fumes. I don't think the hydrogen gas accumulation would be significant to prevent it from being mounted next to the batteries.