My next project is Dual batteries with Perko switch. Whitch optima blue tops should I go with? The D34m or the D31m?

What ever one will fit they are bot good bats one is 55 amp hrs and the other is 71 Amp hrs

Grant- <BR>I just got 2 blue tops (D34m) and a perko switch to replace my old batteries and relay setup. In your opinion , where is the best location to land the Perko switch and what size wire do you use when you guys are installing the switch ?

I would mount the perko switch in the Garbage and mount a battery switching solonoid where ever it will fit.

I second that! Ditch the Perko switch and go with an automatic battery isolator/combiner. There's only one- <a href="http://www.hellroaring.com" target="_blank">www.hellroaring.com</a> The best on the market. A little pricey, but you'll understand when you use it! Get the remote swith for it. You can pop your alternator using a perko switch and/or forget to switch it and deaden a battery. This device does it all for you automatically! And when you're out on the boat all day chillin, relaxing, boarding, dealing with family and/or children and sippin on the beverage of your choice, the last thing you want to do is worry about where the switch is on the batteries or if you're going to pop the alternator when you switch it. <BR> <BR>My $.02 or $.04 whatever the case may be!

What do you guys think about this "battery link ACR" that West marine has? Looks like it would be better than a perko switch but not as pricey as an isolator. <BR><a href="http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&amp;langId=-1&amp;catalogId=10001&amp;productId=223149" target="_blank">http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&amp;langId=-1&amp;catalogId=10001&amp;productId=223149</a>

I don't get why people still want a Peko switch. <BR>Solonoids are so simple, i've used one for 3 yrs <BR>no problems. Perko's are for fishin boats. <BR> <BR> steve210,use a solonoid and leave all the switching to the trolling motor guy's <IMG SRC="http://www.wakeworld.com/MB/Discus/clipart/happy.gif" ALT=":-)" BORDER=0>

The ACR (<a href="http://www.bluesea.com/product.asp?Product_id=53476" target="_blank">http://www.bluesea.com/product.asp?Product_id=53476</a>) is the way to go. It is made by blue seas systems and they only make high quality marine grade electronics. While perko makes all your lower quality latchs hinges lights and a bunch of crap zinc coated parts. Ive seen many of the perko swiches burn up. If you want a manual battery switch (which you should have along with the ACR) buy a blue seas battery switch. They make a whole line to fit your application. Go to <a href="http://www.bluesea.com" target="_blank">www.bluesea.com</a> and check it out. No use building a high quality electrical system with a crappy switch connecting it all.

For those who dont know the acr is a battery sensing relay. It basicly isolates the start battery from the house bank when the start battery drops below the set voltage. Set it high (ie. above the 12.6 your battery sits at) and it'll charge both banks with the engine on and then only draw from the house bank with the engine off. It has a manual override where you can wire in a switch to connect the house bank and start bank if some how you start battery went dead and so then you can start your engine from the house bank. I work at a marine store in seattle and would be glad to answer any more questions <a href="mailto:davidbuswell@comcast.net">davidbuswel l@comcast.net</a> about the ACR. BEP marine (<a href="http://www.bep.co.nz/" target="_blank">http://www.bep.co.nz/</a>) also makes a simaler product called the VSR voltage sensitve relay but it is not adjustable and doesnt have the override.

Don't you guys run into alternator problems? I have an alternator that is rated over 100amps. I think if it had to charge two batteries and run the stereo and a few other things while the boat was running that it would be way over 100 amps. Is that way of thinking not correct?

No, the alternator will only put out what it is capable of and that is why some alternators do burn up. The load on them sits very high for a long time and the internals cook themselves from heat.

Tate: <BR> <BR>A Perko switch is the preferred way to wire things up if you want the option of switching to the alternate battery for starting purposes. <BR> <BR>By the way, Perko is a brand, sort of like saying Kleenex instead of facial tissue. <BR> <BR>If you are going to use a battery switch, and don't have any other automatic isolation mechanism, then you certainly want the switch mounted in an easily accessible location as you will be operating it a lot. <BR> <BR>If you have a separate isolation system, such as the diode isolators or a combiner, then I would mount the battery switch in a place that minimized the wire run from the batteries to the starter. <BR> <BR>Several people have referred to "solenoids", which is often just another term for a very high capacity relay. I do NOT recommend a simple relay for connecting the two batteries. <BR> <BR>First off, "solenoids" are often found in two common varieties: Starter and continuous duty. <BR> <BR>The starter relays/solenoids are rated for a LOT of amps but are also rated for intermitant duty. The actual solenoid (the electro magnet part that operates the relay) is built to supply a lot of force to make sure large contacts make good contact, which is necessary for handling large currents. If operated continuously, however, the solenoid coil will overheat and burn out. <BR> <BR>The continuous duty solenoids/relays will tolerate being engergized all day, but they are not rated for the currents that a starter requires. A common way to hook up such a solenoid is to energize the coil from the ignition, which means that the alternate battery will share in the job of starting the engine. When you starting battery grows old and weak, the alternate battery may provide most or all of the starter current, which could damage the solenoid. <BR> <BR>The battery combiner (Hellroaring, Blue Seas ACR, plus others) is the best solution. They are totally automatic and only connect the batteries when the alternator is providing adequate charge. Use this plus a battery switch and you have the best of both worlds. <BR> <BR>

Teddy, wait till you see what I've added in your old boat. including an upgraded alt (135 amp) and two more batteries. And your right most stock alt. won't keep up with aftermarket accessory demands (most stock alt are in the 60-80 range)

Adam-- <BR>How much coin to upgrade your alt ?

i have a Perko switch and dual blue tops, and a 95A alt. i've been ignorantly running it on "all" for two seasons. the only time i switch is to chill with the stereo or ballast pumps on for a long time with the motor off. <BR> <BR>so i am risking my alternator this way, and should be using only one battery at a time?? :\

<a href="http://cm.ebay.com/cm/ck/1065-29392-2357-0?uid=18887770&amp;site=0&amp;ver=EOIBSA080805&amp ;lk=URL&amp;Item=8003227732" target="_blank">http://cm.ebay.com/cm/ck/1065-29392-2357-0?uid=18887770&amp;site=0&amp;ver=EOIBSA080805&amp ;lk=URL&amp;Item=8003227732</a> <BR> <BR>Paid about 120 or so with shipping, 135 amp. I bought one form this guy last year and it took a s*it on me after about 2 hours of running time, but b/c his service was so good I decided to give him another shot on my new boat. A few people on here use them and have had no issues. For the cheap price, it’s hard to beat. I had a local alt guy open my broke one up and he said the guy uses cheaper parts. IF you want it done right talk to grant, he can custom build one to spec, btu it will cost you ($300-500, I think) but it will be designed for a high powered low rpm sound system (if that make sense). IF this one craps out I’ll return it (two year warranty ) and will call grant the next day. <BR>

Adam... I look forward to it. I have moved on to the 1978 Cobalt. What a peice of sh-t! but the my son is worth every penny. Hope all is well!!

Trace: Running on ALL except when you sit and run the stereo is fine, as long as you remember to switch. I know that in my use I may stop for what I thought would be only a few minutes and then that drags into hours. At some point you have to remember to throw the switch, hopefully before it is too late. <BR> <BR>Adam: I am confused about the local guy saying the parts were "cheap". Cheap in what way? Underrated? Did the manufacturer make good on the warranty? <BR> <BR>Ideally, an alternator would be able to crank out its full output indefinately into a dead short. Realistically, it should be able to crank out its full output into 13 volts indefinately. What is bad is if it overheats and destroys itself if it cranks out full output for very long. <BR> <BR>If you have an alternator that will survive providing full output indefinatly then it doesn't matter what your battey configuration is. For that matter, if your alternator won't survive full output forever then keeping the battery load low only removes one possible overload condition. Blasting the stereo while running lights, pumps, etc. will overload the alternator just the same. <BR> <BR>Bottom line: You are better off having a smaller output alternator that will run 100% duty cycle than an alternator that will provide twice the power but overheats.

after draining one of the batts (say 2 for example), i usually switch to the other battery (1), start the motor, and then switch to ALL. (my Perko is make-b4-break) my thinking was that the full battery would equalize with (charge) the discharged battery when i switched back to ALL, thus minimizing the recharge load on the alt. <BR> <BR>i suppose the risk is if you forget to switch to 1 or 2, and run both batteries really low? that would definitely be a high load if you were able to get the motor started.