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  1. #1
    Petty Officer 1st Class cvtech1's Avatar
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    Default Charging batteries with perko switch

    I recently had a perko switch added to my boat and was wondering can I charge both batteries at once? I put a charger on the positive side of one battery and the shared ground of the other. The one charged battery seemed to leak after being charged awhile. Was this the correct way to charge or not? Again, can I charge both at once? Thanks.

  2. #2
    Supreme Mariner Silvertip's Avatar
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    Default Re: Charging batteries with perko switch

    Sure you can. Set the switch to BOTH and connect the charger to either battery. BOTH puts both batteries in parallel so both will charge. As for the leakage you mentioned, do you mean it leaked electrolyte?

  3. #3
    Petty Officer 1st Class cvtech1's Avatar
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    Default Re: Charging batteries with perko switch

    Yes, it had some liquid on top of the battery and I believed it came from the place where you add water. I had the charger on overnight at 6amps. Thanks.

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    Default Re: Charging batteries with perko switch

    2 problems
    You can charge both batteries at the same time if they are both in good shape and the charger is fully automatic. I dont think this is a good idea. If one battery is weak shorted or just old it may never charge up enough to shut the charger off. So the charger will charge the good battery past its requirment. That is when it leaks.

    If you put a 6 amp charger that does not taper down and shut off when the batteries are charged it will also overcharge both batteries.

  5. #5
    Petty Officer 1st Class cvtech1's Avatar
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    Default Re: Charging batteries with perko switch

    Thanks, but how will know if the battery/batteries are in good shape? To be safe are you saying batteries should be charged seperately? One thing, one is a auto/ starting, the other is a deep cycle (large) I assume it is a deep cycle. It was the one hooked up and leaking. Thanks again.

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    Supreme Mariner bruceb58's Avatar
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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by Lyle29464 View Post
    So the charger will charge the good battery past its requirment. That is when it leaks.
    Totally not true. If you have a bad battery it will hold down the charge voltage so the good battery never gets fully charged. The bad battery will be getting all the current and that is why it will start boiling and leak.
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    Supreme Mariner Silvertip's Avatar
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    Default Re: Charging batteries with perko switch

    You will only know if you have two good, bad or otherwise batteries if you charge them, then take both to any major auto store and have them load tested.

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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by bruceb58 View Post
    Totally not true. If you have a bad battery it will hold down the charge voltage so the good battery never gets fully charged. The bad battery will be getting all the current and that is why it will start boiling and leak.
    ok ok it was 2 am. LOL

    anyway You should not charge 2 at the same time. The miss match will shut one down early. Also most battries need to hit 14.2 volts to help clean off the plates. If your charging 2 at a time you will need a big charger 3 stage charger.

    Tip I think everyone needs a load tester. It will tell you a lot and save you money in the long run. Maybe the short run. how many times have you see someone replace a battery only to find the new one dead in a few days.

  9. #9
    Petty Officer 1st Class cvtech1's Avatar
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    Default Re: Charging batteries with perko switch

    Thanks for all the advice.I will get them tested.

  10. #10
    Supreme Mariner Silvertip's Avatar
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    Default Re: Charging batteries with perko switch

    I take issue with the notion that two, three, or four batteries in parallel will not charge ALL batteries to their full capacity. Why? Because the charger cannot tell which battery is full and which is not. It is monitoring the system, not an individual battery. Parallel systems have been used in diesel powered cars and trucks for decades and if that were an issue an alternate charging system would have appeared long ago. Here are a couple of references the nay-sayers may want to read.

    From Superior Battery Manufacturing:
    Batteries may be connected to the charging source in series, parallel or individually, depending upon the type of charger used. More than one battery (all must be of the same voltage) can be charged on high-rate fast chargers. When this is done, connect the batteries in parallel, i.e., connect the positive (+) terminal of one battery to the positive terminal of the next battery and negative (-) terminal of one battery to the negative terminal of the next battery, etc. The number of batteries that may be connected in parallel depends on the current capacity of the charger. The output of the charger will divide equally among the number of batteries in parallel if they are identical (same rating, same state-ofcharge, etc.) and there are no high resistance connections. For example, if five batteries are being charged in parallel, and the charger output is 20 amperes, each battery will receive 1/5 of the total output, or 4 amperes.

    And you just might be interested in this device which does exactly what is not being recommended. This device just happens to be made by one of the major battery charger manufacturers in the country.

    http://www.centurytool.net/6075_300a..._p/aso6075.htm

    Lastly -- just what do you think a combiner and a switch accomplish? They both allow charging two batteries, or two parallel banks from a common alternator. This is simply not an issue unless you actually have one really rotten battery in the system and that should be obvious without even using a charger.

  11. #11
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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by Silvertip View Post
    I take issue with the notion that two, three, or four batteries in parallel will not charge ALL batteries to their full capacity. Why? Because the charger cannot tell which battery is full and which is not. It is monitoring the system, not an individual battery. Parallel systems have been used in diesel powered cars and trucks for decades and if that were an issue an alternate charging system would have appeared long ago. Here are a couple of references the nay-sayers may want to read.

    From Superior Battery Manufacturing:
    Batteries may be connected to the charging source in series, parallel or individually, depending upon the type of charger used. More than one battery (all must be of the same voltage) can be charged on high-rate fast chargers. When this is done, connect the batteries in parallel, i.e., connect the positive (+) terminal of one battery to the positive terminal of the next battery and negative (-) terminal of one battery to the negative terminal of the next battery, etc. The number of batteries that may be connected in parallel depends on the current capacity of the charger. The output of the charger will divide equally among the number of batteries in parallel if they are identical (same rating, same state-ofcharge, etc.) and there are no high resistance connections. For example, if five batteries are being charged in parallel, and the charger output is 20 amperes, each battery will receive 1/5 of the total output, or 4 amperes.

    And you just might be interested in this device which does exactly what is not being recommended. This device just happens to be made by one of the major battery charger manufacturers in the country.

    http://www.centurytool.net/6075_300a..._p/aso6075.htm

    Lastly -- just what do you think a combiner and a switch accomplish? They both allow charging two batteries, or two parallel banks from a common alternator. This is simply not an issue unless you actually have one really rotten battery in the system and that should be obvious without even using a charger.
    might read the fine print in both posts Mine and Your. I say YOU NEED A THREE STAGE BIG CHARGER To DO IT. Your says you need a fast charger and then the regular charger. This is the same thing. But The original post seemed to indicant that he was using a small automatic or trickle charger. bringing up several batteries that have been discharged on one regular size charger will never let them gas. They will have a very short life. One very small battery charger will hold many fully charged batteries at 100% for years.

  12. #12
    Supreme Mariner Silvertip's Avatar
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    Default Re: Charging batteries with perko switch

    He has his charger set on 6 amps. If the switch is set to BOTH both batteries will charge just fine at 3 amps each. Obviously a bigger charger gets the job done quicker but 3 amps will do the job. Besides, the starting battery is very likely not deeply discharged so it will actually "help" the charger since there will be a tendency to equalize the two batteries just as there would be if the charger were not attached. And I will repeat -- just what do you think happens when the engine is running and the switch is set to BOTH. People have used switches for years on very low output alternators. Not much advantage in doing that I agree but never-the-less, it isn't an end of the world either. I guess all of the manufacturers need to pull all of the switches, combiners, and isolators off the market as they are battery killers huh!

  13. #13
    Supreme Mariner bruceb58's Avatar
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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by Lyle29464 View Post
    bringing up several batteries that have been discharged on one regular size charger will never let them gas.
    What in the heck are you talking about?
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  14. #14
    Petty Officer 3rd Class EricKit's Avatar
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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by bruceb58 View Post
    Totally not true. If you have a bad battery it will hold down the charge voltage so the good battery never gets fully charged. The bad battery will be getting all the current and that is why it will start boiling and leak.
    I fully agree with that. I'm wondering if there is any case where a bad battery gets to it's full voltage and stops getting any current instead of sucking all the current. Would this allow the other battery to charge?

    The only reason I think that can't be is because there would be a battery only "allowing" a 12V difference on the nodes, so there could never be more and it would always suck the current to compensate.
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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by bruceb58 View Post
    What in the heck are you talking about?
    Let me try it this way. If you want a good long life out of a lead acid battery you really need a 3 stage charger. In the first stage the battery receives much more current than any 6 amp. charger can deliver. This is why I was saying do not charge 2 batteries at the same time. Some one questioned this, because they have seen 2, 3 and 4 batteries on a diesel being charged at the same time. They also have a 150 or 200 amp alt. we still are talking about a 125 Jonhson that might charge 10 amps on a good day if all conditions are met. Or on the home charger at 6 amps. That was the question that started this post. back to the 3 stage. As the lead acid discharges the buildup on the plates begins. The buildup if not removed is the death nail in the battery. It takes a gas type action to remove most of this. The gas builds up between 14.2 and 14.7 volts If you are running a small charger or trying to charge 2 batteries it is highly unlikely your unit will bring the voltage to the necessary level to make the gas. (14.2) after the fast start ( high current ) the stage 2 kicks in and drops the current flow to a level that the battery can absorb. stage 3 is just a float charge.

    If you are just mainting a fully charged battery or more you can just hook 5 of them up to any charger that will shut off when fully charged and all is well a 1 amp is as good as a 50

    If you recharge many times at a slow rate your battery will have a faster buildup on the plates and a short life.

    a motorcraft battery used in a truck will have a normal life of 7 years. Of course most all cars have a 3 stage charger. ( alt)

    a trolling motor used several times a summer and slowly charged will last a few years. It is the number of discharges and how they are recharged that determine the life. Yes age as a bit to do with it but not as much as you might think. The same trolling motor recharged with a 3 stage will last 2 to 3 times as long and do better from day one.

    I really would like to know if this has helped anyone?

    Thanks Lyle

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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by EricKit View Post
    I fully agree with that. I'm wondering if there is any case where a bad battery gets to it's full voltage and stops getting any current instead of sucking all the current. Would this allow the other battery to charge?

    The only reason I think that can't be is because there would be a battery only "allowing" a 12V difference on the nodes, so there could never be more and it would always suck the current to compensate.
    please read my past post and see if that clears this up.

  17. #17
    Supreme Mariner Silvertip's Avatar
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    Default Re: Charging batteries with perko switch

    It's been covered a thousand times in this forum. Nothing new other than the bit about slow charge rates vs high charge rates. A charge rate up to 20% of the batteries AH capacity is acceptable. Since we don't know what "quality" the posters charger is this is all a moot point. If that's all he has and intends to use, one pays the consequences with battery longevity. However, this gets to be like driving a Prius. One gets so wapped up in trying to beat the next guy with gas mileage that you become a hazard on the road because you are driving to damned slow. Use what you have and be happy with the longevity. Spend some bucks on a better charger and you maybe save the cost of one battery in a 5 or 6 year period.

  18. #18
    Petty Officer 3rd Class EricKit's Avatar
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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by Silvertip View Post
    It's been covered a thousand times in this forum. Nothing new other than the bit about slow charge rates vs high charge rates. A charge rate up to 20% of the batteries AH capacity is acceptable. Since we don't know what "quality" the posters charger is this is all a moot point. If that's all he has and intends to use, one pays the consequences with battery longevity. However, this gets to be like driving a Prius. One gets so wapped up in trying to beat the next guy with gas mileage that you become a hazard on the road because you are driving to damned slow. Use what you have and be happy with the longevity. Spend some bucks on a better charger and you maybe save the cost of one battery in a 5 or 6 year period.
    I like the analogy. Always good info.
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  19. #19
    Supreme Mariner bruceb58's Avatar
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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by Lyle29464 View Post
    As the lead acid discharges the buildup on the plates begins.
    You have this backwards. As a battery discharges, the plates lose material not gain it. You may be associating the sulphating which may occur as a discharged battery sits in an uncharged state. When this happens, its hard for the charging process to replenish the material on the plates.

    Quote Originally Posted by Lyle29464 View Post
    Of course most all cars have a 3 stage charger. ( alt)
    Name one.
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  20. #20
    Supreme Mariner bruceb58's Avatar
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    Default Re: Charging batteries with perko switch

    Let me give a few scenarios..

    1) You have two batteries..one is 80% charged and the other is 90% charged. Assuming they are exactly the same capacity, if you don't apply a charge voltage and connect the perko switch to combine them, after a time, they will both end up at 85% charged minus any energy wasted as heat since batteries do have some resistance.

    2) You connect a charger to one battery and throw the Perko switch to combine. Two things are going to happen. The current from the charger will essentially want to divide in proportion to how the batteries are discharged. The less charged battery will receive the bulk of the current. At the same time, there will be a current flow between the more fully charged battery and the more discharged battery. As the batteries approach equal charge, the charge current will become more equal between the two batteries until they both reach fully charged. There will never be a scenario where one becomes fully charged before the other one assuming all have good cells which have very similar voltage characteristics to each other.

    3) In the case where one battery has a bad cell, the battery charger will never detect that the batteries are fully charged and never get into the final float stage. In this case the battery with the bad cell will get all of the current while that good battery only gets up to the highest voltage that the bad battery will let it(they are in parallel). The extra current given to the bad battery will not be used to charge the battery but will cause gassing of the battery and heat(the energy has to go somewhere).
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  21. #21
    Seaman TexMojo's Avatar
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    Default Re: Charging batteries with perko switch

    Wow, this is too much. I have a perko but I also have a onboard dual charger, I ran the cables straight to the battery bypassing the perko.

  22. #22
    Supreme Mariner Silvertip's Avatar
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    Default Re: Charging batteries with perko switch

    And that would be the correct way to do it since you have a dual output charger. This entire thread is about using a single output charger and whether or not a single charger can charge two or more batteries in parallel.

  23. #23
    Seaman TexMojo's Avatar
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    Default Re: Charging batteries with perko switch

    Quote Originally Posted by Silvertip View Post
    And that would be the correct way to do it since you have a dual output charger. This entire thread is about using a single output charger and whether or not a single charger can charge two or more batteries in parallel.
    I recently had a perko switch added to my boat and was wondering can I charge both batteries at once? I put a charger on the positive side of one battery and the shared ground of the other. The one charged battery seemed to leak after being charged awhile. Was this the correct way to charge or not? Again, can I charge both at once? Thanks

    Thats where the wow, comes into play, everybody appears to want to discuss their knowledge on the problem when it would be alot easier to tell the guy to either buy a dual charger or replace the weak battery. Just my opinion of course.

  24. #24
    Petty Officer 1st Class cvtech1's Avatar
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    Default Re: Charging batteries with perko switch

    I have a small 6v/12v 2amp & 6amp charger that you can on the back of the boat. It is a Schumacher dual rate charger. If this is not a good or the proper charger for long life of my battery can someone recommend a good priced charger. Thanks for ALL the advice. Happy Boating!!

  25. #25
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    Default Re: Charging batteries with perko switch

    I just turn the switch off and charge them seperately. Maybe takes longer, but I have time,,,,,,,

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