Converter Amps

[jamjrks]

At the risk of getting feedback that I am posting to the wrong forum, I have a question about the Amp rating of a converter. I just bought a new fiver and it came with a 65 amp converter. My previous fiver had a 90 amp converter. What difference does it make since my shore power is 50 amp service? Am I mixing apples and oranges here? Need some RV Electrical Power 101 tutoring here. Thanks.

[Chum_lee]

OP: Yes, you are mixing apples and oranges. (120 volts vs. 12 volts) Your shore power, really 2 circuits at 50 amps each (or 100 amps total) in your case is at 120 volts and runs straight into the to the main converter bus. The rating on your converter, 65 Amp, means that drawing off the main bus, it can convert up to 780 Watts of available power to 12 Volt DC in your case.

Watts = Volts x Amps or 780 Watts = 12 Volts x 65 Amps
7800 Watts = 120 Volts x 65 Amps
Watts = Power

65 Amps at 12 Volts is not the same power as 65 Amps at 120 Volts, power wise. As you can see, the former is 10x less.


The rest of the available 120 Volt power, watts really, (minus the converters 12 Volt conversion losses, internal cooling fans, resistors, etc.) is available to power the 120 Volt consumers in your RV up to the circuit breaker limits which should be 2-50 Amp circuits or 100 Amps total. In theory, the converter is only using about 6.5 Amps @ 120 Volts out of your available 100 amps to generate the 65 Amps you have available at 12 Volts. Make sense now?

work = power

Think of Volts as water pressure.
Think of Amps as water flow.
Think of Watts as the amount of work (power = flow x pressure) they do.

Chum lee

[MrWizard]

Of you are a FHU camper, 35amp converter is all you need
If you camp without hook ups
65amp is much better and 90amp is great
for recharging the battery bank using a generator

[time2roll]

Most only need 35 amps. 65 or 90 is just overkill to brag on the spec sheet.

[pianotuna]

Hi,

What make and model is the converter?

[Sam_Spade]

jamjrks wrote:
Am I mixing apples and oranges here?

Yes.

Follow the link given; more information there than you need or want probably.

Your so called 50 amp service is:
50 amps at 240 volts or roughly 12,000 watts.
That can also be used as two 50 amps at 120 volts; still 12,000 watts.
That's your input when plugged in. Might be somewhat less if a generator is supplying the input power.

The converter takes part of that input power and converts it to 12 V to run the portable 12 V systems and batteries; mostly to charge the batteries.

65 amps is probably plenty for your 12 V system. Only time and your specific usage needs will tell the whole story.

[westend]

50 amp Rv service will handle multiple chargers, all operating at their rated 120V input draw (labeled on converter). DC output is variable by make and model of converter and the battery's SOC.
If you wish to get back up to a 90 amp charge rate, a standalone battery charger would be a cheap addition. IMO, unless you do a lot of generator charging, the 65 amp model should be OK. Battery acceptance rate, typically, gets low pretty fast.

[CA_Traveler]

What's important is battery type, battery capacity, charger quality, DC loads, DC wiring and how you camp.

Your new charger may charge faster and better or NOT. You may need it to charge faster and better or NOT. etc.

Post information on the above to get help. It has nothing to do with 20/30/50A service.

[2oldman]

Apples and oranges. Read this..

12v side of life.

If there was ever an 'RV electrical power 101', that is it.