Dual Batteries (Perko switch)

How do you run your dual battery switch (Perko)? Assume starting battery is #!, and acc/Stereo is #2.

Do you keep selector on battery #1 while running boat and then select battery #2 when stopped and running stereo? Or do you run with selector switch on both, then switch to battery #2 when engine is off?

After stopped for a few hours and battery #2 is 50% depleted, do you switch to battery #1 to start and run on that, or switch to both to start (drawing down battery #1, but allowing #2 to accept charge)?

Can you switch from battery #1 to battery #2 while engine is running?

The way I used to do it was when WB on both when listening to music and chillin on #2,but now I have auto switch.

Big Ed, I used to have an auto relay too. Here’s why I went back to a switch. I was at a beach for about 6-7 hours jammin the radio….totally depleted battery # 2 ( down to 10.9 volts) Battery #1 still has full charge. When I turned the key it switched to both batteries. B/C battery # 2 was so low it pulled from battery # 2 untill the charges equalized around 11.2-11.5…..basically depleted both batteries. Luckily it started, but we were the last ones left…..if it wouldn’t have started it would have been a long swim home.

Now with the switch I have total isolation if needed. You can’t get that with a relay. Your either both batteries or battery #2.

If yours is wired differently , I’d like to know how?

I believe it is wired different but if the boat starts right away there just isn't enough time for the batteries to equalize!

I'm gonna have to get on this guy to send me the blueprint of the whole duel alt install + 3 batt for system and one for boat.

Run your batteries with the mindset of using one battery as your primary and one as secondary backup. Use your primary battery for ALL functions. If you are parked with the boat and listen to the stereo then go ahead and continue to use the primary while stopped. If you try and start and the primary does not have enough to crank then switch the perko to the secondary battery (which should be 100%) for start then switch back to the primary after start to let the alternator recharge the primary battery. Make sure you use deep cycle batteries (not starting batteries) for this procedure (A starting battery is not designed to repetitively discharge and recharge like a deep cycle).

You can switch from battery one to battery two with a perko (it will connect the battery you switch to before disconnecting the battery you switch from).

Do not switch to off with the engine running, it may cause damage to the alternator if your perko does not have alternator field disconnect capability.

Do not use the perko in "BOTH". It will align your batteries in parallel and they will both drain at the same time (thus eliminating the concept of primary and secondary). If you use both it should only be when one battery alone will not start the engine.

To charge the secondary battery select it on the perko and let the motor run for about 30 minutes each day you run the boat. That will keep the secondary battery at full charge.

When running the boat set it to Both so it charges both. When you stop to listen to music set it to one of the batteries. If you drain that one go take a few sets (on both) to charge it back up. I never tap into my other battery for playing music for fear of being left stranded.

Great post topside marine, exactly the info I was looking for.

When running the boat, I've been running the perko on "both". I see your point. It really doesn't make sense to do that. My #1 is a starting battery. #2 is two 6V batteries in series. I guess I'll be starting on #1 then switching to #2 untill they get low. Using #1 as a backup/starter only. Knowing this helps

"You can switch from battery one to battery two with a perko (it will connect the battery you switch to before disconnecting the battery you switch from)."

I would not touch the battery switch when running, some contacts have a bit of slack in them especially when getting old and you may have a disconnect when moving the contacts form battery #1 to #2 or selecting both. This momentary short will collapse the field on the alternator, a sort of de-magnitization. I run #1 all the time (like topside says) and when you need the extra juice for a start select BOTH, it will not equalize the battery in the few seconds it takes to start the boat it will only put both batteries online for charging. After starting run at a "higher than idle RPM" on both batteries for at least 30 minutes then switch back to #1 after you stop the engine. If #1 gets fried then select 2, but always do selecting with the engine off!

i was told not to run mine on both because it is hard on the alternator. topsidemarine's comments are exactly what the car toy's installer told me.

I agree about leaving the Perko on #1 all the time, but I also have this connected between terminals #1 and #2 of the Perko:
http://www.yandina.com/c100Info.htm

This automatically connects the 2 batteries when the alternator is charging (senses >13.3V) so both batteries are always charged. And they are both still isolated when not charging. You never have to move the Perko switch.

This has a slight advantage over a relay that combines whenever the ignition switch is on, because it also protects against alternator failure. If your alternator fails while you are running, the batteries will isolate so you only drain one. When your engine finally dies and you discover your primary batt is drained, you can then switch to your backup battery and get back to the dock. If you were using a relay, then both batts would be drained by the time your engine died.

(Message edited by flsurflover on October 28, 2005)

what about having two deep cycle batteries and using them for starts and services??
What are the odds on this batteries for starters?

Adam:

I am not sure what the "auto" switch you used before was but if it connected the two batteries together with the engine not running then it wasn't a very good one!

The "battery combiners" that I am familiar with sense the voltage on the two battery systems and will connect them ONLY when one has a voltage sufficiently high (usually around 13 volts) to indicate that not only is there charging going on but that the primary battery has a significant amount of charge on it. Note that the battery combiner should never have to pass more current than the alternator is capable of putting out.

I have made the mistake of using a simple relay driven by the ignition to combine batteries. In that case you can get pretty much what you describe. The dead battery shouldn't be able to pull the fully charged battery down any significant amount very quickly. What can happen, however, is if your starting battery gets low, then you connect a fully charged second battery you end up passing starting current through the relay, which can be way more than the relay was intended for.

Here is how the combiner is supposed to work:
Let's say you parked the boat and ran the stereo off the second battery. Some time later you go to start the boat, starting battery is nearly full, the stereo battery is way down.

The combiner looks at both batteries, one is at 12.4 volts, the other is at 11.5 volts. Neither are high enough to cause the combiner to connect.

When you hit the starter, battery 1 drops to 10.5 volts, battery 2 stays at 11.4 volts. Combiner keeps them separate.

The engine starts, alternator starts pumping out minimal amps because the RPM is low. Voltage on battery 1 climbs to 13.0 volts. This is still below the threshold for the combiner, batteries are kept isolated, what little amps the alternator is providing goes into battery 1, making sure it gets charged up.

You idle out of the 5 MPH zone, and hit it. RPMS climb up, the alternator starts cranking out maximum amps, battery 1 voltage climbes to 13.5 volts. Now the combiner connects the two batteries.

You're going fast so you crank up the tunes to hear the music over the wind noise. Maybe it is getting dark and you turn on the tower lights. Maybe it is cold and you are running the heater. You left the blower on so it is drawing current, and you are trying to empty the ballast tanks so the pumps are running. Bottom line, the alternator can't keep up, and voltage drops below 13.0 volts. The combiner senses this and isolates the two batteries, making sure the starting battery is kept full.

The combiners are essentially fool proof. Just make sure that you get one that will handle the current rating of your alternator. If you have a 150 amp alternator, makes sure the combiner can handle 150 amps!

Rod, my post may have been confusing. When you turn the boat off it isolated both batteris, when you turned the boat on it combined both batteries.

Adam,what Rod is saying is....it still will be isolated until certain amps.This is how mine is hooked up,exactly how Rod explained.The start battery is always isolated until alt. provides enough amps and then batt. are combined.

I was using the stinger isolator/relay.
Rod is talking about a battery combiner.
I think Rod thought I was talking about a combiner not a relay??

Ed when you referred to auto switch I thought you were talking abotu a relay not a combiner.

relay,combiner....what's the differents.

Batteries... Horsepower... beer and women
the more you have the merrier you are

combiner.
http://www.yandina.com/c100Info.htm

relay
http://www.stingerelectronics.com/web/prods/fans.asp

Now I'm not sure....it looks like I got a relay.I'm gonna call this guy right now,just need to find his #.Tho he told me that I can run the other 3 batteries dead and I'll always have the starting batt.good.

Here is my schematic, everything is on order, installation should start next week. I have traced the currents frontwards and backwards and I believe it's foolproof. One thing about electricity, it always flows through the path of the least resistance, and that's not always the desired path when you just use the relay.

This thread has been helpful.

Mike

battery schematic Boat Battery Diagram.pdf (17.6 k)

One more thing... The C150 battery combiner is not spark protected so you will need locate it outside of the engine/fuel compartments. The C100 is spark protected so it can go inside the engine compartment, but it's only good for a 100amp alternator (which is just right for mine for now).

Mike, the schematic looks good to me except the dual batts for the stereo. It looks like they are wired in series which would give you 24V to your stereo.

I am considering an almost identical setup to Mike's. I agree about making sure the batteries are not put in series as in his drawing. I already have 2 batteries and a perko switch, but want to add a third. How big should the wire be that joins the two batteries together? Would 1/0 be plenty? I noticed that the wires to the perko switch are 2/0. WIll the difference in resistance be significant enough to make a difference?

I'm not the smartest guy in the world but isn't it right how Mike drew it up?

Wow I'm lost. I wired my Perko how the package said, with the only exception being ground my stereo batteries to the main battery. So, start/charge to perko, main battery positive to #1 on perko. The two stereo batteries wired together (positive and negative) to each other then the positive to the Perko switch position #2. The one ground connecting the batteries to each other (both stereos and main), and then one ground from there to the boat ground. Seems to work? I hope

Big Ed,

Mike has put the batteries connected in series, from positive of one battery to negative on the other. This will increase the resistance, right? Unless he is using 6 Volt batteries.

Shouldn't he just join the negatives together and the positives together to keep the resistance the same?

(Message edited by talltigeguy on October 30, 2005)

oops he has the negative of the other batt....never mind.

If I recall an earlier post from Mike, he said that he was using golf cart batteries, which are 6 volts each, so wiring them in series as he has shown is correct.

The size of the wire that you need is a function of the current you will be drawing, the length of the wire, voltage drop that you can tolerate, and the temperature rating of the wire. It is not possible to say what if a wire is big enough unless you know the factors.

The wire sizes that Mike has listed look very reasonable for the amperage I would expect and the lenght of wire that is normally encountered wiring a ski boat.

Hi all,

Sorry I hadn't looked back at this post for a while. The wiring diagram is for golf cart batteries. In my application they seem to be the best solution when considering weight, size, and cost per amp hour. I know there are a few issues with wet lead-acid batteries but I can deal with them. Using the trojan T-105's I can fit them nicely side by side just in front of the factory ballast tank behind the driver in my 211. They only weigh 62lbs. each, cost about $80 each and provide 225 amp hours total (that's not each since they will be wired in series, if you have two 12v batteries then you double the rating). My batteries will be very accessible and they can be placed upright. I was considering the new large blue tops but they won't fit side by side in that location.

The 1/0 wires feed from the batteries to the amplifier power distribution blocks, it's overkill but I want to minimize voltage drop and provide maximum capacity for bass hits without the assistance of a capacitor. The #2 wires back to the main starting battery are sized to handle short cycle starting currents if I ever switch the perko to both in start mode. The #8 wires on the C100 are sized to protect the relay inside the C100 (they are small intentionally to reduce the inrush current, note these wires should not be cut shorter than the factory length).

I am also adding an accurate digital LCD voltmeter on the dash with a A/B rocker switch so I can monitor the voltage at each battery bank. The voltmeter and battery combiner arrived last night, my project will start next week after I get my boat back from a few warranty issues at Correct Craft.

"Coming soon" - photo how-to on the voltmeter install.