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Charging dual batteries

Old 05-11-2020, 03:45 PM
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Default Charging dual batteries

Hi,
Being a new owner of a 1987 Formula 242 ls, I'm looking for some information on the right way to charge dual batteries from shore with a Perko switch. Should I select one battery at a time or will selecting "all" charge both batteries but at a slower rate.
Again, my thanks for any information
Tony S
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Old 05-11-2020, 04:04 PM
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Single engine I will assume.

Putting the switch to "all" will charge and discharge the batteries as if they one large battery. Depending on your alternator capacity and current battery conditions it could take a long time to adequately charge the batteries in this configuration, unless you are running your motor all day long with little or no load from accessories. I like to keep one battery as fully charged as possible...just in case you need it. Using the "all" setting gives you no backup.

Some options are to alternate days. One day use battery one and the next time out switch to battery two. That way you are keeping one charging and one offline. Or another option is you can switch to battery one on your way out for the day and switch to battery two on your way back in. Again, your mileage may vary on length of running time and how much drain from accessories you use.

Best to start with a good external charger and top them off to get a base level. Charge them separately.
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Old 05-11-2020, 05:54 PM
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Originally Posted by Tony S View Post
Hi,
Being a new owner of a 1987 Formula 242 ls, I'm looking for some information on the right way to charge dual batteries from shore with a Perko switch. Should I select one battery at a time or will selecting "all" charge both batteries but at a slower rate.
Again, my thanks for any information
Tony S
1st check voltage of each battery with a meter with the perko switch off. Charge them individually. Let them rest for a half hr and check the voltage. 12.5 or more. Replace if necessary. Now once they are fully charged and known good you can keep them maintained by switching to "both" and charge with charger or while running.
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Old 05-11-2020, 06:06 PM
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Charge individually with multi bank charger and only place in both when both are needed to start a motor. No need to damage a good bat with a weak one
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Old 05-11-2020, 06:15 PM
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Originally Posted by Tony S View Post
Hi,
Being a new owner of a 1987 Formula 242 ls, I'm looking for some information on the right way to charge dual batteries from shore with a Perko switch. Should I select one battery at a time or will selecting "all" charge both batteries but at a slower rate.
Again, my thanks for any information
Tony S
1st check voltage of each battery with a meter with the perko switch off. Charge them individually. Let them rest for a half hr and check the voltage. 12.5 or more. Replace if necessary. Now once they are fully charged and known good you can keep them maintained by switching to "both" and charge with charger or while running.
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Old 05-11-2020, 07:15 PM
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Originally Posted by AllDodge View Post
Charge individually with multi bank charger and only place in both when both are needed to start a motor. No need to damage a good bat with a weak one
This.

I have a NOCO Genius 20 amp 2 bank charger permanently mounted in my boat and keep the boat plugged in at all times. Currently have 5 years on the batteries and still going strong. Whichever charger you choose, make sure it has a tending mode.

Last edited by JimNut; 05-11-2020 at 07:18 PM.
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Old 05-12-2020, 06:48 AM
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A few good options posted above. I'll add my 2 pennies as well. I have 2 individual chargers in mine. Previous owner installed. A few days before using the boat I'll plug them in. Verify voltage while checking oil and what not. I always place the perko on both. Run the boat to the desired hangout. Switch to batt 1 for stereo purposes all day. When preparing to leave I swap back to both. On the way in this will charge both batteries. Because the alternator is charging obviously, but also because the unused battery is now in parallel with the weaker one. They will balance out over a short period of time.
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Old 05-12-2020, 07:35 AM
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ACR



Or with a single bank charger

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Old 05-13-2020, 12:06 PM
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Nice graphic
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