Do I really need a Perko?

[model14]

Doing the restore thing on a 88 ThunderCraft with the 120 2.5L Mercruiser. I am doing a lot of rewiring. Do I really need to install a Perko battery isolation switch? Some say the battery is always draining even with the ignition off. Boat stays on a trailer when not cruising.
Richard

 

[bigdirty]

Re: Do I really need a Perko?

IMO there will always be 'some' parasitic drain on the battery(s), just as in any car/truck, but its not to say you HAVE to install one... you could simply disconnect the + lead from the battery while the boat is sitting not being used.

 

[jbcurt00]

Re: Do I really need a Perko?

you could simply disconnect the + lead from the battery while the boat is sitting not being used.

I think they sell a specific connector for doing that quickly & easily w/ out affecting the terminal connection to the battery post.

Or a switch:

 

[waterwezl]

Re: Do I really need a Perko?

Big dirty is correct in that disconnecting the battery will prevent parasitic draw however I would suggest disconnecting the negative side of the battery as opposed to the positive. I've been a tech for GM for roughly 20yrs and it is always recommended to disconnect the negative first and when reconnecting the battery, connect it after the positive terminal is secure. This is especially important if you have any electronics installed (ie. ship to shore, fish finder, etc. etc.). The little spark ya get when connecting the positive after the negative cable is a spike in amperage that can destroy many of today's electronics...sometimes even letting the magic smoke out of them that makes them work.

 

[waterwezl]

Re: Do I really need a Perko?

Another option is a solar battery maintainer. I have one on my car hauler to keep the winch battery up on it. It's always ready to go when I need it regardless of how long it sits up.

 

[bigdirty]

Re: Do I really need a Perko?

Big dirty is correct in that disconnecting the battery will prevent parasitic draw however I would suggest disconnecting the negative side of the battery as opposed to the positive. I've been a tech for GM for roughly 20yrs and it is always recommended to disconnect the negative first and when reconnecting the battery, connect it after the positive terminal is secure....

See, I NEVER understood what difference it makes, (iE; why it is always recommended to do it this way?) because either way you are 'breaking' or 'making' a complete circuit. Same thing to me as 'which lead and which batt to hook jumper cables to first, blah blah blah...

This is especially important if you have any electronics installed (ie. ship to shore, fish finder, etc. etc.). The little spark ya get when connecting the positive after the negative cable is a spike in amperage that can destroy many of today's electronics...sometimes even letting the magic smoke out of them that makes them work.

Also, from what i understand, IF you get 'a little spark' that is a SURE sign of some parasitic drain somewhere, and I can say from my own exp. I have seen it spark on positive AND negative, regardless of which is secured first....

oh, and :laugh: @ 'magic smoke'

 

[alldodge]

Re: Do I really need a Perko?

Doing the restore thing on a 88 ThunderCraft with the 120 2.5L Mercruiser. I am doing a lot of rewiring. Do I really need to install a Perko battery isolation switch? Some say the battery is always draining even with the ignition off. Boat stays on a trailer when not cruising.
Richard

Agree with bigdirty but your battery should be fine with a couple months of sitting. If after a couple months you find your battery drained some, need to find the source of the drain, put in a switch or install a battery charger/maintainer. I keep mine plugged in year round

 

[bruceb58]

Re: Do I really need a Perko?

You disconnect the negative first on a car because if your wrench touches the chassis of the car, you won't get a short and a very hot wrench.

On a boat, the battery disconnect switch is always done on the positive side.

The little spark ya get when connecting the positive after the negative cable is a spike in amperage that can destroy many of today's electronics...sometimes even letting the magic smoke out of them that makes them work.

Not true at all. There will be the same current flow no matter which you do first/last.

 

[Vintin]

Re: Do I really need a Perko?

I disconnect mine not because of possible parasitic drain...........but because it greatly reduces fire hazard.

 

[waterwezl]

Re: Do I really need a Perko?

I took this straight from GM's service information regarding battery disconnection. I've also seen from personal experience more than one module destroyed because of improper battery installation. Not being argumentative just going based on what I've seen personally. Every electronic device draws a small amount of current for memory. I won't be taking any chances myself regarding electrical systems.



Warning: Batteries produce explosive gases. Batteries contain corrosive acid. Batteries supply levels of electrical current high enough to cause burns. Therefore, in order to reduce the risk of personal injury while working near a battery, observe the following guidelines:

Always shield your eyes.
Avoid leaning over the battery whenever possible.
Do not expose the battery to open flames or sparks.
Do not allow battery acid to contact the eyes or the skin.
Flush any contacted areas with water immediately and thoroughly.
Get medical help.

Warning: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

 

[GA_Boater]

Re: Do I really need a Perko?

Bruce has it right - the reason is when the tool bumps a ground after the negative is disconnected - No sparks. All the GM stuff is because the battery does emit hydrogen gas. Remember the Hindenberg? And today with all the always on electrical equipment in a vehicle there is always a drain. But the negative spark is less of a spark than when you short the positive to ground. And the other thing is per your GM warning:

Warning: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component.

Do they tell you how to to do what I bolded? No, because it can't be accomplished unless all the fuses and circuit breakers are pulled and fusible links are cut. Impossible and improbable and never done.

As far as battery disconnects - Always on the positive terminal. Race cars, trains, planes and boats always disconnect the positive. Look at how a Perko switch is wired - Positive disconnect.

 

[Howard Sterndrive]

Re: Do I really need a Perko?

http://forums.iboats.com/boat-topic...-intelligent-battery-gaurd-review-437508.html
my review of the Nautilus disconnect (remote)
too bad these never caught on outside Canada. Sometimes they come up on ebay. I love mine. I don't have to dig around for some switch.

 

[Howard Sterndrive]

Re: Do I really need a Perko?

As far as battery disconnects - Always on the positive terminal. Race cars, trains, planes and boats always disconnect the positive.

heavy equipment almost always on the negative

 

[bigdirty]

Re: Do I really need a Perko?

Bruce has it right - the reason is when the tool bumps a ground after the negative is disconnected - No sparks. All the GM stuff is because the battery does emit hydrogen gas....

Yup, I got a 9/16 wrench with a chunk out of it from touching a frame, while trying to remove the main 12v lead to a GM starter.. this was 15 years ago, but its still 'burned' into my psyche.. :laugh: ALWAYS DISCONNECT THE BATTERY CABLES FIRST!

And yes, typical lead acid battery's do emit small amounts of hydrogen, but I was under the impression they only do so while being CHARGED, not just sitting...

 

[Sea Stomper]

Re: Do I really need a Perko?

I have a battery switch with two batteries, selects 1,2, or both. I ALWAYS disconnect both batteries even though I can turn them off. My Chrysler outboard powered boat is a salt water only boat and I don't need AN'Y stray currents wreaking havoc as in electrolysis on my 38 year old engine. After 6 years of this practice, I have an engine that does not look at all like a salt water engine. It's very clean. So for me, disconnecting batteries is a corrosion preventive measure and that's all I care about. In fact, when I'm salmon trolling out in the ocean using a 6 horse Johnson kicker, I always turn off the batteries but I do have an isolated electonics power bus keeping the electronics powered up. I also shut off the batteries while halibut drifting out there too.