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-   -   Charging Dual Batteries With Perko Switch (http://www.wakeworld.com/forum/showthread.php?t=745381)

jmcdanie 11-04-2009 6:32 AM

Hello WW. <BR> <BR>I am rather new to the board (been lurking for awhile though). Just purchased a 2010 MB Sports TWB a couple months ago (had a SeaRay I/O). MB makes an awesome boat! <BR> <BR>These boats come standard with dual batteries and a perko switch (and just about anything else I could think of). I have put the boat in a garage for the winter down the road from me, but it is not easy to go out and swap the charger from one battery to the other every once in awhile. I do not really want to pull the batteries if I do not have too (with the SeaRay, I would just pull the one battery and leave it in my garage on charger). <BR> <BR>I have read multiple posts about charging and everything from the archives, but I am not very good at reading between the lines and I could not find a post that directly answered my questions. <BR> <BR>So, the questions are: <BR>Since I have dual batteries and a Perko Switch, can I use a trickle charger to charge both batteries at once? If so, how can I do that? Do I need the Perko set to ALL or do I need to rearrange the wires with + to + and - to -? <BR> <BR>Any help would be appreciated.

05mobiuslsv 11-04-2009 6:58 AM

You can trickle charge both and set the perko to All to do so.

dudeman 11-04-2009 7:19 AM

This is what I use. Seems to work well for the price. <BR> <BR><a href="http://www.amazon.com/Battery-Tender-022-0165-DL-WH-2-Bank-Management/dp/B000NCOKV0/ref=sr_1_3?ie=UTF8&amp;s=automotive&amp;qid=125734 7845&amp;sr=8-3" target="_blank">http://www.amazon.com/Battery-Tender-022-0165-DL-WH-2-Bank-Management/dp/B000NCOKV0/ref=sr_1_3?ie=UTF8&amp;s=automotive&amp;qid=125734 7845&amp;sr=8-3</a>

chpthril 11-04-2009 7:23 AM

Just put the Pos (+) wire from the charger to the "C" (common) terminal of the Perko and run the switch in "Both". This is the same s the alternator charging. Just make sure the Neg (-) of the charger goes to the engine or the neg (-) of the main/starting battery.

bill_airjunky 11-04-2009 8:14 AM

<a href="http://www.amazon.com/Battery-Tender-022-0157-1-Power-Charger/dp/B002DU3S9A/ref=sr_1_1?ie=UTF8&amp;s=automotive&amp;qid=125734 9458&amp;sr=1-1" target="_blank">Here is the Battery Tender</a> that Deltran customer service recommended I use in the boat. I think the difference is it's "waterproof" and shock resistant.

innov8 11-04-2009 8:22 AM

I run the 2 bank battery tender in my shop and it works great. <BR><a href="http://www.batterystuff.com/battery-chargers/12-volt/multi-bank/BT2b022-0165.html" target="_blank">http://www.batterystuff.com/battery-chargers/12-volt/multi-bank/BT2b022-0165.html</a>

david_e_m 11-04-2009 9:32 AM

Joe, <BR> <BR>It's a very good question. <BR> <BR>Get a true marine multi-stage dual-bank charger (Guest 5amp + 5 amp for example). It will wire independently and permanently to both batteries. During charging you'll set your Perko to 'OFF'. <BR> <BR>The starting battery is normally fully charged and only needs maintenance attention. A majority of the available 10 amp current is diverted to the stereo battery so that it is properly recharged (conditioned, desulfated, etc.) immediately after an outing and then settles into the maintenance mode also. <BR> <BR>Treating both batteries as a single unit when charging or treating a deep cycle battery like an automotive battery with a trickle/tender-only charger will lead to a shortened battery lifespan. <BR> <BR>David <BR>Earmark Marine

dudeman 11-04-2009 9:34 AM

Doesn't the battery tender settle into a maintenance mode after the batteries are charged? From what I've read, they claim it does.

innov8 11-04-2009 9:36 AM

Yes Randy they do. <BR> <BR>"he Two Bank Battery Tender Charging Stations are two encased 1.25 amp battery chargers. They're designed to fully charge a battery and maintain it at proper storage voltage without the damaging effects caused by trickle chargers." <BR> <BR>(Message edited by innov8 on November 04, 2009)

dudeman 11-04-2009 9:40 AM

Thanks Jeff, that's what I thought. Guess we're good. <BR> <BR>(Message edited by dudeman on November 04, 2009)

bill_airjunky 11-04-2009 9:44 AM

Hey David, What do you recommend for a "true marine multi-stage dual-bank charger"? Is the two bank Battery Tender good or is there something else?

innov8 11-04-2009 9:44 AM

Yeah I have been using them at my dealership for our boats and they work excellent. <BR> <BR>I have a 2 bank system on every boat.

david_e_m 11-04-2009 9:59 AM

Randy, <BR> <BR>Sure they do. The concern would be that the charger has enough capacity to chemically excite a discharged battery, particularly a deep cycle type, in order to desulphate the thicker plates. Rule of thumb is to use a charger that is at bare minimum, 10% of the total amp/hour rating on the batteries. More would be better. <BR> <BR>Also, avoid an automotive charger that has a 'fast charge' mode. Its not the same as a marine 'bulk' mode. <BR> <BR>Bill, <BR> <BR>Whenever possible, step up to a Guest 10 amp or ProMariner 20 amp dual-bank charger. Same functions, just more capacity for conditioning. <BR> <BR>David <BR>Earmark Marine

moon 11-04-2009 12:15 PM

Don't mean to hijack but over the summer I installed the Guest 10 amp dual bank set up which charges each battery at 5 amps. My problem is that I have 3 batteries. One starting battery and two batteries hooked in parallel for accessories. During the season the accessory batteries were each connected to the two banks and I didn't really worry about the starting battery, but during the winter I want to remove all three batteries from the boat and charge them all at the same time. Is the Guest battery charger capable of doing this? Can I hook one bank up to the starting battery, and then keep the two accessory batteries connected in parallel and the other bank hooked to one of those batteries? Any input or suggestions would be appreciated. <BR> <BR>Thanks, <BR>Moon

david_e_m 11-04-2009 2:10 PM

Moon, <BR> <BR>While its less than ideal, it will work the way you described. At first glance that would appear to be only 2.5 amps per each of the paralleled accessory batteries. But, some marine chargers will allocate the current to the bank in need and a starting battery arrives in storage usually fully charged. <BR> <BR>You could also add a very small single-bank 'tender' to just the starting battery. Again, this battery should never be deeply discharged so it doesn't require the additional current. It should always be limited to the maintenance level. Then you would have the total 10 amps available to the two accessory batteries. Unfortunately, you would be circumventing the isolation that treats the two batteries individually. But if they're identical this is an acceptable compromise where you wouldn't need a second isolation switch. <BR> <BR>David <BR>Earmark Marine

bill_airjunky 11-04-2009 2:35 PM

Thanks David. <BR> <BR>Hey Moon, it looks like <a href="http://www.boatersland.com/pmr31313.html" target="_blank">Promariner has a 3 bank charger too</a>.

moon 11-04-2009 2:53 PM

Thanks Bill, but I've already got the charger and just trying to figure out how I can use it on three batteries for the winter. My wife would be pissed if she new I was getting another charger in less then a year. <BR> <BR>David, two more questions. When charging the accessory batteries do I just keep them connected in parallel and have the single bank connected to one battery (will this charge both of them?)? Or, do I keep the batteries connected in parallel and have the + from the charger connected to + of one battery and the - from the charger connected to - of the other battery? Also, with this charger I can keep them connected all winter long without worrying about the batteries or the charger getting to hot? Thanks for all your help. <BR> <BR>Moon

chikara22 11-04-2009 6:45 PM

My be a dumb question, but, why do you have to switch the Perko switch to off when charging the batteries? I am running a Promariner 20 charger on two Blue top optimas (1 starting and 1 for stereo) in my boat and have not turned the Perko switch off during charging. What am I at risk for damaging if I don't turn the Perko switch off?

05mobiuslsv 11-04-2009 7:08 PM

You don't have to.

bill_airjunky 11-04-2009 7:18 PM

Maybe just to isolate the boat systems from the AC and any issues that might come from it? ie; power spikes, brown outs, etc.

jmcdanie 11-05-2009 6:57 AM

Thanks for all the great responses! I will be negotiating with the wife on when I can get a new charger. Will probably just go with the dual bank Battery Tender!

david_e_m 11-05-2009 10:49 AM

Moon, <BR> <BR>If its just for winter maintenance, then there's no point in adding the second, small and very inexpensive 'tender' charger. You would only see a benefit during the season when you're recharging. So proceed as you had planned and if you're looking for an improved scenario, deal with it in the spring. <BR> <BR>I'm not sure it will have an impact, but I guess if we're getting picky, wire the pos. to one battery and the negative to other paralleled battery. In either case, both batteries get charged. The difference in resistance would be immeasurable. <BR> <BR>Your batteries should not get the least bit warm. If they are, it would mean you've got a bad battery(s) that isn't properly charging. Flooded batteries can self-discharge as much as 3 to 4% a month so winter maintenance is preferred as long as its a smart charger like the Guest. <BR> <BR> <BR>Will, <BR> <BR>It does make a difference but there's no major risk. Here's why you should turn the Perko to 'OFF' when AC charging while in storage. <BR> <BR>The two banks of your charger are internally isolated to read and react independently through the various stages. When the Perko is 'ON' the two batteries are in parallel. The charger now treats both batteries as a single battery as you've circumvented the intended isolation. <BR> <BR>When you put your boat up in storage, it's likely that you're starting battery is already fully charged but your stereo battery has not been fully restored from a period of playing the stereo at rest. <BR> <BR>So, while the charger is attempting to restore the stereo battery its also unnecessarily heating the starting battery. <BR> <BR>There's going to be some leveling between the two batteries while the engine is running and the Perko is in the 'ON' position. But chances are you're putting the boat up with different charge levels plus the two batteries are definitely aging differently. <BR> <BR>So, a simple switch selection may extend battery life.

moon 11-05-2009 11:24 AM

David, You The Man!!! You've always been very helpful and informative. <BR> <BR>Thanks A Bunch, <BR> <BR>Moon

chikara22 11-05-2009 5:45 PM

Appreciate the help David. You guys did my stereo system and you have always been really helpful and knowledgeable.

jmanst15 07-17-2013 10:39 PM

Bringing this thread back!!
Hey guys,
Just got a dual battery set-up installed in my boat. Couple questions...

1) My well respected marine only stereo shop said I should always just use battery 1 and o my use battery 2 as a back up for battery 1 if it gets drained during a long session at rest? Should I do this or should I switch to batt 2 when in a cove at rest?

2) when switching to a different setting on the switch should I turn off all accessories?

3) and just to be clear, I should charge each battery independently in the OFF position to maximize battery life in the winter??

Thanks all

chpthril 07-18-2013 4:39 AM


1) Depends on what type of batteries are in each bank, the type of switch and the type of dual battery system.

2) no need to turn off accessories when switching battery banks, but never turn to OFF with the engine running. Also, not all switches are make-before-break, so you need to know what type of switch you have to make sure its safe to switch between banks with the engine running.

3) yes.

I would talk further with your installer to get further details on your specific setup as they know exactly what you have, how its configured and how best to use it.

jmanst15 07-18-2013 8:54 AM

3 Attachment(s)
This is battery 1. The original battery connecter on the negative is here and the accessory post has two cables on it.

Attachment 30906

This is the switch

Attachment 30907

Battery 2 has just one set of cables attached to each terminal.

Attachment 30908

Let me know what you guys think is best for my situation from my OP.

1) My well respected marine only stereo shop said I should always just use battery 1 and o my use battery 2 as a back up for battery 1 if it gets drained during a long session at rest? Should I do this or should I switch to batt 2 when in a cove at rest?

2) when switching to a different setting on the switch should I turn off all accessories?

3) and just to be clear, I should charge each battery independently in the OFF position to maximize battery life in the winter??

jmanst15 07-18-2013 2:41 PM


moon 07-18-2013 11:23 PM

I can't say if your stereo shop is correct or not and I'm not sure this will help because I have 3 batteries, but here is what I do. 1 battery is dedicated to starting the boat and the other 2 batteries are dedicated to accessories. When we are cruising I have the switch turned to setting 1 and that battery is being charged by the alternator. When the boat is turned off and we are just listening to music the switch is turned to 2. The accessory batteries are shore charged when we get home.

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