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Mtnmann13 · 10-07-2020, 09:30 AM

Hello All,
I’m new to forum posting( never posted on a forum before, here or otherwise) so please forgive any new comer fouls. I have a 07 gearbox that has a high pitch sound coming from the power converter under load. Can someone explain why I have two power converters? One is a 45 amp and the other is 75 amp. The trailer is equipped with an onan 5500 genset and is wired for 50amp shore power. Why would I have a 75 amp converter with only 50 amp power? I’m fairly mechanical/electrical savvy , but new to these systems. Thanks for any help you can provide!

jcussen · 10-07-2020, 09:52 AM

The converter is 12 volt only [although your 120 volt breakers may be in it the same box.]. The 75 and 45 rating is the dc amps they can supply to charge your batteries and run 12 volts loads. Perhaps PO wanted the ability to charge batteries faster so added second converter. The sound may come from the cooling fan.

richard5933 · 10-07-2020, 10:06 AM

Don't confuse the 50-amp service of your coach with the amp rating of the 12v charger/converter. Those are two totally separate systems, and the only point they touch is where your charger/converter gets its power from the 120v system to charge your batteries and make DC power.

Your 50-amp service refers to the ability to bring in 50-amp AC electrical power through the pedestal by using your shore power cord. It has four conductors - one ground, one neutral, and two hot lines each bringing in up to 50 amps.

The amp rating of your charger/converter refers to how much 12v DC power they can send to your battery bank(s).

Why do you have two charger/converter units? My guess is that one is providing power to keep your house system up and the other is dedicated to charging your chassis batteries. It might not be the case, but that's what I'd check out first. Makes sense to have a smaller one for the chassis batteries since they won't have much of a draw while you're parked/camping.

Mudfrog · 10-07-2020, 10:07 AM

Ya don't see many TTs with built in gensets. I'm kinda thinking that the previous owner installed the Onan and the 75 amp power supply in an attempt to camp off grid more easily. Maybe to be able to get more charge into the house batteries with less genset run time?

Are both convertors hooked to shore power? I was thinking that maybe the genset supplied voltage to only the 75 amp charger and that the shore power cord went to the 45 amper.

Not sure if a set up like this would be a route someone would go,,, really just thinking out loud here..

Mtnmann13 · 10-07-2020, 10:30 AM

Thank you for your help. The trailer is a toyhauler. I’m confident the genset is factory equipment. It is also equipped with a battery master switch. I’ve noticed when the battery is on, and we are plugged into shore power I get a swooshing sound, similar to water running. If I disconnect either one source it goes away and all is good. When I’m on shore power and turn on the flood lights outdoor , it starts making a high pitch squeal noise. It also does it when the presided to a switch house lights turn on. If neither of those is on, I can run a/c and all the other lights without the squeal. Both converters are next to each other ( under a cabinet) so I can’t tell which one the squeal comes from. I don’t replacing one or both if necessary, but I’m trying to avoid a couple of very expensive guesses.

twinboat · 10-07-2020, 10:44 AM

See if the converter/chargers are plugged in, or on seperate circuit breakers.

Turn each off, one at a time, to find the one making the noise.

Some folks add a second converter to recharge large battery banks, how many batteries do you have ?

If you dont have a large battery bank, you don't need over 100 amps of charging capacity.

If you want your batteries to last, leave at least one on while in use or on shore/generator power, so the converter/charger or chargers can charge them up.

Mtnmann13 · 10-07-2020, 10:54 AM

They are both plugged into the same outlet under the cabinet. I will unplug them one at a time. Generally with rv’s , would these both go directly to the battery, then battery power to breaker box? Also, I have two 12v batteries

Skip426 · 10-07-2020, 11:13 AM

Quote:

Originally Posted by Mtnmann13

Generally with rv’s , would these both go directly to the battery, then battery power to breaker box? Also, I have two 12v batteries

Welcome to iRV2.

A lot depends on location of the 12 volt system components , if the converter is closer to the batteries, than to the 12 volt fuse panel , then the wiring would go directly to the battery , if the 12 volt panel is between the converter and the batteries , then both the converter and batteries would be connected there; to avoid extra wiring .

twinboat · 10-07-2020, 11:24 AM

Most factory converter /chargers run to the 12 volt fuse panel. That way they can work even if the battery is switched off.

With 2, 12 volt batteries, you can use either converter/ charger. The 45 amp one is probably stock, but if its bad, use the 75 amp one.

Mtnmann13 · 10-07-2020, 12:55 PM

Thank you all sooo much. I have some more to try tonight after work. I’ll post results for anyone’s future reference.

Mtnmann13 · 10-07-2020, 09:54 PM

On shore power, when I unplug the 75 amp converter the 45amp one starts really whining. When I unplug the 45 amp, the 75 amp fan turns in immediately, but it doesn’t whine. Would anyone conclude the 45 amp is going bad? Or just overloaded?

Persistent · 10-08-2020, 08:38 AM

"Can someone explain why I have two power converters? One is a 45 amp and the other is 75 amp."

Many TT's come with a built in charger/converter that also has a service entrance for the 50 amp AC and a fuse box for the 12 volt system all combined. In any case, I expect the 45 amp converter/charger is the original.

Larger battery banks will charge faster with larger converter/chargers. Owners often want to minimize generator charging time and may add a faster charger. The 75 amp charger may do that job.

What amp hour capacity does your battery bank hold?

Removing the 45 amp charger may be difficult if it is attached to the service entrance and fuse box and so may have been left in place. It may or may not be operational.

Posting make and model of the converter/chargers would clarify this a little.

"The trailer is equipped with an onan 5500 genset and is wired for 50amp shore power. Why would I have a 75 amp converter with only 50 amp power?"

TT's can have multiple power sources. Most have shore power and battery power. Yours also has generator power. Some have inverters to make 120 volt AC from the 12 volt DC battery bank. Some also have solar power.

The shore power provides more power than the battery system. It is used to run A/C, microwave, electric water heater, battery charging, etc. Battery power provides lights, water pump, controls for propane appliances, etc.

The generator is used to replace shore power. It may be rated for 45 amps at 120 volts.

50 amp 240 volt AC shore power provides 50 X 240 = 1200 watts of power.
45.8 amp 120 volt AC generator provides 45.8 X 120 = 5400 watts.
45 amp 12 volt DC converter/charger provides 45 X 12 = 540 watts.
75 amp 12 volt DC provides 75 X 12 = 900 watts.

I wish you good luck and happy trails ahead!

Mtnmann13 · 10-08-2020, 09:42 AM

Thank you for your reply. The converters are WFCO brand. No solar or inverter. I’ll pull the batteries and check the amp hour rating. Thanks again for your help

twinboat · 10-08-2020, 10:16 AM

You don't need to pull the batteries to find the AH rating, 2 12 volt batteries will have 120 to 200 AH total.

It may be a good idea to get a simple load test of them if you don't know the age or condition of them. Bad batteries can work the converter harder.

Another way to test them is to disconnect them after charging them for 6 to 8 hours, wait a 2 days, and see if the voltage drops below 12.6 volts.

As far as the last post about how they may wired here and there and where they are, we already know that they are next to each other and plugged into standard outlets.

Just unplug the 45 amp one and let the 75 amp one run for 6 to 8 hours and see if the fan stops or only runs occasionally.

If the batteries are low, the converter/charger amp output will be high and the fans run to cool it down. Its automatic..

That goes with turning on 12 volt lights, pumps and fans. Any 12 volt items use power and the converter/charger will ramp up its output to handle that. More output, more heat, more fan running.