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Old 08-01-2018, 17:38   #1
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AC amp rated shortfall Question on components for a Marine Battery Charger

I purchased a Pro Charge 12volt 60-amp Ultra charger. This is my first fixed installation dealing with AC marine components in making wire connection to my new battiery charger in my boat. As a result, Iím a bit confused about the AC Amp componet rated outputs.

Iím attempting to learn as I go as it is me at the end responsible for understanding how systems work.

Why is it on a quality an AC 240 volt single phase plugs sockets and wire leads manufactured for the marine environment are at rated at only 10 Ė 15 amps and not higher? Does this effect and limit the charging of my batteries by my Charger to only 10-15 DC amps from an AC input to my charger?

I want to charge up my two AGM battery banks, one is 5 x 100 = 500 amps, and the engine starter is 2 x 100= 200 amps using the full capacity of thePro Charge 60 amp Ultra?

I notice that 3 phase AC is rated at 32 amps, still well short of the DC 60 amp new Chargers rating.

Iím missing (AC to DC amp Knowledge) I'm guessing there is a significant AC to DC amp charging ratio if so what it is?

Or do I need to find another solution to makeup the shortfall in AC to DC Amps for the charger?

Thank you for reading my questions,

S/V. Skoiern IV Kryg.

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Old 08-01-2018, 17:52   #2
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Re: AC amp rated shortfall Question on components for a Marine Battery Charger

You need to get a handle on using watts, a measure of power. watts = volts x amps. So 10 amps at 220volts is 2,220 watts. 60 amps x 13v = 780 watts. So in your case the power available on the AC side is far more than needed on the DC side.
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Old 08-01-2018, 20:10   #3
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Re: AC amp rated shortfall Question on components for a Marine Battery Charger

Before you start messing around with AC connections, it is essential (i.e. life saving) that you understand the basics of electricity. Please take a look at Amps v Amp hours v Amps/Hr for a start.

To answer this part first:
> I'm guessing there is a significant AC to DC amp charging ratio if so what it is

There is no AC to DC ratio. What there is - is a Voltage to Voltage ratio:

To get you started.

10 or 15 Amps is meaningless unless you know what Voltage you have..
The basic unit of power is a Watt. Watts = Amps x Volts and conversely Amps = Watts / Volts.

15 Amps at 240 Volts = 15 x 240 = 3,600 Watts. That's a lot of power - enough to kill you easily.

When you reduce that voltage down to 12V DC, you still have the same power (Watts) but now you have it at 3600/ 12 = 300 Amps.

Your batteries are not 500 Amps and 200 Amps, they are 500 Amp hours and 200 Amp hours. That's a totally different thing and tells you how much energy they contain.

Your 60 Amp battery charger is capable of putting out 60 Amps at a nominal 12 Volts. That is 720 Watts. Assuming 100% efficiency in conversion, that would require 720 Watts going in. Since the power going in is at 240 Volts, that means that your charger will require 720/240 = 3 Amps - well within the capacity of your 10-15 Amp 240 Volt supply.
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Old 09-01-2018, 21:07   #4
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Re: AC amp rated shortfall Question on components for a Marine Battery Charger

Quote:
Originally Posted by StuM View Post
Before you start messing around with AC connections, it is essential (i.e. life saving) that you understand the basics of electricity. Please take a look at Amps v Amp hours v Amps/Hr for a start.

To answer this part first:
> I'm guessing there is a significant AC to DC amp charging ratio if so what it is

There is no AC to DC ratio. What there is - is a Voltage to Voltage ratio:

To get you started.

10 or 15 Amps is meaningless unless you know what Voltage you have..
The basic unit of power is a Watt. Watts = Amps x Volts and conversely Amps = Watts / Volts.

15 Amps at 240 Volts = 15 x 240 = 3,600 Watts. That's a lot of power - enough to kill you easily.

When you reduce that voltage down to 12V DC, you still have the same power (Watts) but now you have it at 3600/ 12 = 300 Amps.

Your batteries are not 500 Amps and 200 Amps, they are 500 Amp hours and 200 Amp hours. That's a totally different thing and tells you how much energy they contain.

Your 60 Amp battery charger is capable of putting out 60 Amps at a nominal 12 Volts. That is 720 Watts. Assuming 100% efficiency in conversion, that would require 720 Watts going in. Since the power going in is at 240 Volts, that means that your charger will require 720/240 = 3 Amps - well within the capacity of your 10-15 Amp 240 Volt supply.
Hello StuM, Your thoughtful reply is very helpful, as well as the link. Its is just the kind of information to my questions I was seeking.

Many Thanks, Kryg
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Old 09-01-2018, 21:09   #5
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Re: AC amp rated shortfall Question on components for a Marine Battery Charger

Quote:
Originally Posted by Paul L View Post
You need to get a handle on using watts, a measure of power. watts = volts x amps. So 10 amps at 220volts is 2,220 watts. 60 amps x 13v = 780 watts. So in your case the power available on the AC side is far more than needed on the DC side.
Hello Paul,

Your reply is very helpfu. Its is just the kind of information to my questions I was seeking.

Many Thanks,
Kryg
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