The Official Dual Battery Thread

[JimN]

OK, I forgot that they just go to the battery cable at the starter since the battery is farther away from the alternator than in a car or truck. Sorry about that.

[Diesel]

Jim -

Then, there is a 2 AWG battery lead going from the starter to my Perko Battery Switch COMMON terminal. I did not find any wire going directly from the alternator to either battery. This is how my dealer wired in my isolator and battery switch and it worked fine.

IMHO this is a very dangerous way to wire the system. If by chance somebody turned the perko the wrong way (to off) it will instantly kill the regulator in the alternator. The charging lead off the alternator should always be hard-wired (no switch) to at least one of the batteries(banks). It is the safest way to do it, no exceptions.

I understand why the Perko switch was used and I discourage it in any dual battery setup simply because the relay does the exact same thing, is automatic, and costs less.

However in your new setup I do not understand why you would keep the Perko switch at all?? If you just want to cut power I would install it on the 6-8ga lead that powers the rest of the boat harness. As a rule I do not place any switching devices between the charge and starter circuits of the engine harness and engine battery(banks). Too much current and too much risk IMHO.

[prostar205]

Diesel -

Is it OK to add a wire, of appropriate AWG, from the + terminal of the alternator direct to the + terminal of Battery 1 and also keep the 8-10 AWG that goes from the alternator to the starter?

Regarding the use of the Perko, since I already have it and do not have a relay, I think I am going to use the Perko for now. If I determine it is a PIA, I will add either a Battery Combiner or the BW relay.

[zberger]

I still have no idea why you guys are bothering with perko's........................................... ...........

[prostar205]

Zberger -

Suggestions in place of the Perko????

Borg Warner replay?
Battery Combiner?
Isolator?

Need input.

Thanks

[prostar205]

A few more questions.

If I go with a isolation relay, like the Borg Warner R3098 or Sitnger SR200, since ALL the batteries will be in parallel once the key is turned to the ON position, is this a good idea with two difference battery types. My main starting battery will be a standard lead-acid DEKA marine battery while the AUX battery (stereo) is two Optima Blue Tops?

Would I also have an issue with just using the Perko switch?

[prostar205]

Anyone have a comment or answer on my above posted question???

[Leroy]

Prostar; I would say not ideal, but probably not a problem. Main concern is difference in voltage causing one battery to charge more or not allow the other battery to charge enough. I personally like the relay best since it is automatic. You could either measure the voltage on each battery or look at the spec's to see how closely they match. The Optimas are AGM and the starting battery is lead acid so they are indeed different battery types.

[BrianS]

The Perko switch is needed if using the battery combiner because the batteries are not placed in parallel until the system is charging, ie the alternator is turning. Therefore, it is not possible to start the boat from Bank 2 without using the switch (in the event that Bank 1 dies).

With an isolator or relay the batteries are placed in parallel when the key is switched to the "Run" position, so both batteries are used to start the boat at all times.

The Perko switch is designed to sit between your batteries and the rest of the system, ie starter, alternator, etc. It provides total control over which battery is used for starting and which is being charged. It is ignition protected and as long as you use the proper guage cable I see no problem with using one.

[Leroy]

FYI, http://www.yandina.com/acrobats/C150Data.pdf

From earlier thread: http://www.tmcowners.com/teamtalk/pr...p?t=2183&pp=40

[Diesel]

Anyone have a comment or answer on my above posted question???

You will be fine. The only time I try to match batteries is when they are hard wired parallel with no isolator. In this case you will be using an isolator between the two banks of batteries and a charging current will be applied most of the time the banks are connected which will further prevent any damaging discharge between banks.

[Diesel]

The Perko switch is needed if using the battery combiner because the batteries are not placed in parallel until the system is charging, ie the alternator is turning. Therefore, it is not possible to start the boat from Bank 2 without using the switch (in the event that Bank 1 dies).

With an isolator or relay the batteries are placed in parallel when the key is switched to the "Run" position, so both batteries are used to start the boat at all times.

The Perko switch is designed to sit between your batteries and the rest of the system, ie starter, alternator, etc. It provides total control over which battery is used for starting and which is being charged. It is ignition protected and as long as you use the proper guage cable I see no problem with using one.

Sounds confusing

[prostar205]

Diesel -

I had a little change in plans. I am currently only going to use the Perko switch and no isolator - for now. Am I still going to be OK with "mixed" batteries between battery 1 (lead acid type) and battery 2 (Optimas)?

The way I see it is: when using the Borg Warner Relay, as soon as you energize the ignition (motor off), all the batteries as immediately put in parrallel. At least with the Perko Switch, I can turn it to battery 1, start the engine and then turn the Perko switch to both to allow both batteries to charge.

I am now at the point of installing the amps and headunit (Pioneer Premier DEH-P860MP) and I have a few questions. I will PM you this morning.

[OhioProstar]

IMHO it is hard to trust a relay or isolator without upgrading your alternator and associated fuses/wiring. All of a sudden you are spending quite a bit and putting a lot of faith in a single point of failure (isolator/relay). For a lot less you can run a switch($25), I used BlueSea, and a multi-bank changing system($100) that you just plug in at night to keep both batteries changed. If a battery is drawn too far down then you just turn the switch to the back up battery and once running turn back through the ON position to the main bank for charging. I understand that it is not automatic, but it seems the most cost effective and the least problematic in the long run.

[Diesel]

Diesel -

I had a little change in plans. I am currently only going to use the Perko switch and no isolator - for now. Am I still going to be OK with "mixed" batteries between battery 1 (lead acid type) and battery 2 (Optimas)?

You will still be fine if you choose to use the perko. Just don't forget to leave it on both or turn it to off when the battery is running, or etc, etc, etc............

The way I see it is: when using the Borg Warner Relay, as soon as you energize the ignition (motor off), all the batteries as immediately put in parallel. At least with the Perko Switch, I can turn it to battery 1, start the engine and then turn the Perko switch to both to allow both batteries to charge.

You can wire the relay to function how ever you want. If you add a DPDT switch instead of using the ignition switch you will basically have a perko that is controlled from a rocker switch in the dash. A MC bilge switch cover works great since is already says auto, off, and manual. By adding the DPDT switch you can have the relay work off the ignition switch (automatic), completely off (full isolation), or manually closed (full time parallel). This is how my jeep is wired.