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Old 02-16-2017, 01:46 PM   #1
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battery charging

Hi, I have been boating for about 50 yrs. so I should know the answer to this, But the other day , a friend asked me a simple question, it was, if I have a battery charger hooked up to my batt. & the AC power goes out , will the charger run down ( kill ) the battery ? easy question, but I didn't have a clue !1 thanks Rich S
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Old 02-16-2017, 01:51 PM   #2
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Depending on the charger, most have a drain (measured in milliamps). So, yes, but slowly.

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Old 02-16-2017, 02:39 PM   #3
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Yes/no:

But very, very slowly. Don't worry about it. Not significant.

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Old 02-16-2017, 03:47 PM   #4
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Does this include a standard hard wired multi bank charger? Mine is connected all winter and I haven't noticed any more drawdown than could be explained by self discharge. Unfortunately manufacturers don't seem to make ALL the specs readily available.

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Old 02-16-2017, 03:57 PM   #5
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Yes, each bank is protected from discharging the other ones.

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Old 02-16-2017, 04:13 PM   #6
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Yes, each bank is protected from discharging the other ones.

David
I get that part but I think I heard that people have info that battery chargers do have a slight drain of the batteries when not charging. For my own curiosity I'd like to find out those kinds of specs but I've never seen them from any manufacturer.

Ken
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Old 02-16-2017, 04:41 PM   #7
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I think the term you're looking for is parasitic load.

Parasitic load is a term used with regard to electrical appliances and railway locomotives. With regard to electrical appliances, it represents the power consumed even when the appliance is shut off, that is standby power.

https://en.wikipedia.org/wiki/Parasitic_load
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Old 02-16-2017, 04:41 PM   #8
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Reverse current would have to go through a diode, one of the last things in the charger circuitry. Not much flow there. You've got six diodes doing the same thing in each alternator.

If it concerns you, measure it with an ammeter. Not something I would worry about.
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Old 02-16-2017, 05:49 PM   #9
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I have a Mastervolt Chargemaster 12/50-3 whose specifications state:

DC consumption , display OFF - <5mA
DC consumption , display ON - 130mA

The display is configurable as to whether it is ON or OFF when the unit is in standby mode.



I don't have any idea if this is typical of other makes or models.
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Old 02-18-2017, 06:46 AM   #10
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For winter storage most batts do best simply disconnected at the terminals.
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Old 02-25-2017, 11:07 AM   #11
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Quote:
Originally Posted by richardschmidt2759 View Post
Hi, I have been boating for about 50 yrs. so I should know the answer to this, But the other day , a friend asked me a simple question, it was, if I have a battery charger hooked up to my batt. & the AC power goes out , will the charger run down ( kill ) the battery ? easy question, but I didn't have a clue !1 thanks Rich S


An AC/DC charger is just a transformer and a rectifier. First the transformer windings take you down 110V AV to 12V AC and then the rectifier converts the 12V AC--> 12V DC.

If you lose AC then nothing happens as the rectifier diodes prevent any battery charge from going back through the transformer windings.

There is therefore no loss of battery charge if you turn off AC.
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Old 02-25-2017, 06:51 PM   #12
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Quote:
Originally Posted by lelievre12 View Post
An AC/DC charger is just a transformer and a rectifier. First the transformer windings take you down 110V AV to 12V AC and then the rectifier converts the 12V AC--> 12V DC.

If you lose AC then nothing happens as the rectifier diodes prevent any battery charge from going back through the transformer windings.

There is therefore no loss of battery charge if you turn off AC.
Reality trumps theory every time. Disconnect the 120 AC. Put a VOM set to read amps between the positive terminal and the positive battrry lead. You will measure milliamp flow.

Ted
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Old 02-25-2017, 08:34 PM   #13
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Quote:
Originally Posted by lelievre12 View Post
An AC/DC charger is just a transformer and a rectifier. First the transformer windings take you down 110V AV to 12V AC and then the rectifier converts the 12V AC--> 12V DC.

If you lose AC then nothing happens as the rectifier diodes prevent any battery charge from going back through the transformer windings.

There is therefore no loss of battery charge if you turn off AC.

Welllll , OK .....very simplified!

Before modern 3 state chargers arrived, chargers did use a transformer and diodes AND they also had a capacitor. The transformer was a very special transformer whose magnetic inductance was designed to resonate with an external capacitor to form what was called a constant voltage transformer.

The design is very complex and very frequency sensitive. A few cycles off the tuned frequency, usually 60Hz in this country resulted in large output voltage changes. The output waveform resembles a pseudo square wave with a large voltage spike on one of the edges.

Because the system had a relatively constant output voltage it was used as a constant voltage source to charge batteries.
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Old 02-26-2017, 05:55 AM   #14
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"Because the system had a relatively constant output voltage it was used as a constant voltage source to charge batteries."

The old Const- a -volts were well matched the did a great job of keeping the voltage constant , but to not boil off water rapidly , from charging voltages.

They were really converters , rather than battery chargers.

Todays problem is the chargers are used as dockside converteres which can cause a hassle.

A Big DC load , like a fridge starting with some lights on can tell the charger to begin charging.

Not just making some DC for the load , but actually charging.

This may cause the battset to go to 14.4V before falling back to sitting voltage levels .

If your battset is frequently requiring water , this could be the cause.
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