Which Converter

[David 70]

I recently replaced my absorption cooling unit on my 1201 Norcold with the Amish dual compressor unit. I installed 2 new GC2 golf cart batteries also. I spent the last week at a tractor show with no electricity. The fridge worked fine as long as the batteries stayed up. JR says with my size batteries the fridge should run 11-18 hours on fully charged batteries. Therein lies my problem. It takes 4 hours or so to bring the batteries back up to 12.6 volts from 11.9. My converter is a model 7455T, 55 amp. I want to put a new PD 9200 in. What are thoughts on the amperage rating needed. Will 60 do it or should I go with a 70 amp. Will the amps make much difference when it comes to charging time if nothing else is running?

[ArtJoyce]

If it takes a 55 amp converter 4 hours to bring it up to 12.6v. I don't hinkly 5 more amps (60 amps) or 9% more amps will by you much. That would be about 24 minutes faster to get to 12.6v if just assuming the battries are taking as much as you can feed them.

Flooded cells battries while charging; as the voltage builds up develop internal resistance and slow the rate they absorbed amps. In effect making the converter amp ratting a moot point since the converter ratting far exceed the abortion of the batteies.

[johnhicks]

Spell heckler is our friend.

[twinboat]

It's not so much your converter as it is the wire running to it.. I would buy a stand alone converter and install it near the batteries with 2 gauge wire.

[d23haynes57]

You have a lot of wrong stuff going on here. To begin with why would one choose a refrigerator option without having a 24-to-48-hour power supply?
For the limited performance of this maybe an inverter and residential fridge would be cost effective. You are going to need more batteries, and they need an upgraded design, AGM Or Lithium.

For the 2 conventional golf cart batteries, the preferred charge rate is 6 to 8 hours. You go up to a 4 rate as a quick charge. Your batteries are rated ~220 A/H so your 55 A/H charger is correct for that application. If you're going to upgrade, especially as you have other loads now running while charging go right to something in the 100 A/H range, as long as your generator can support it. Consider an inverter charger combination as this will give you other benefits.
As part of this upsize the batteries. Lithium can charge at near 1/2 capacity or even faster. A 400 A/H bank will somewhat more than double your run time and a 150 A/H charger can fully charge it in less than 4 hours. They will also weigh a lot less. Yes, there are other considerations, but this is likely a direction worth pursuing.

If you would like more direct help OK to P-mail me.
My login name here @ hotmail.com.

[Mark_K5LXP]

Originally Posted by David 70

It takes 4 hours or so to bring the batteries back up to 12.6 volts from 11.9.

If these are before and after static voltages (not charging or under load) you're replacing most of the available capacity in 4 hours. One has to wonder just what your actual power draws are if you're using up most of the capacity of a ~220Ah battery in under 18 hours. I think before you go through replacing what is probably an adequate converter or dropping large dollars on lithium you should consider getting a battery monitor and having a better idea of usage and remaining capacity.

Mark B.
Albuquerque, NM

[David 70]

Denis, thanks for the explanation. My batteries are rated at 225AH so I don't know if they would be considered 450 total or not. I plan on doing some kind of upgrade this spring. My fridge was at the point that it would not keep the bottom below 50 and the freezer much below 30. I pulled it out and there was a big burn spot above the boiler, so I decided I was not going back with a gas one. I'm looking into some solar so that is another decision as to what. It has the factory 10 watt one, but we all know how good they are and at 20 years old they are way less efficient. I'm thinking I need more batteries also. It's all something to figure out over the winter. The wiring is just whatever the factory put in, so I have no idea what it is yet. I was pressed for time with a tractor show coming up so I done the quickest thing I could.
Mark B. These voltages are what the gauge shows in the panel. They are goofy sometimes and I have a digital gauge that I am going to put in that reads directly off the batteries. A load meter would be a good idea also so it is something I will think about over winter.

[d23haynes57]

Originally Posted by Mark_K5LXP

If these are before and after static voltages (not charging or under load) you're replacing most of the available capacity in 4 hours. One has to wonder just what your actual power draws are if you're using up most of the capacity of a ~220Ah battery in under 18 hours. I think before you go through replacing what is probably an adequate converter or dropping large dollars on lithium you should consider getting a battery monitor and having a better idea of usage and remaining capacity.

Mark B.
Albuquerque, NM

Agreed! That should have been part of the plan once becoming dependent on battery for anything critical. Still, I see folks doing all sorts of stuff not always being satisfied with the results. There is value getting a pro, having an engineered solution, not a salesperson selling products or vehicles.

[d23haynes57]

Originally Posted by David 70

Denis, thanks for the explanation. My batteries are rated at 225AH so I don't know if they would be considered 450 total or not. I plan on doing some kind of upgrade this spring. My fridge was at the point that it would not keep the bottom below 50 and the freezer much below 30. I pulled it out and there was a big burn spot above the boiler, so I decided I was not going back with a gas one. I'm looking into some solar so that is another decision as to what. It has the factory 10 watt one, but we all know how good they are and at 20 years old they are way less efficient. I'm thinking I need more batteries also. It's all something to figure out over the winter. The wiring is just whatever the factory put in, so I have no idea what it is yet. I was pressed for time with a tractor show coming up so I done the quickest thing I could.
Mark B. These voltages are what the gauge shows in the panel. They are goofy sometimes and I have a digital gauge that I am going to put in that reads directly off the batteries. A load meter would be a good idea also so it is something I will think about over winter.

Your 2 GC batteries are 2 6-volt batteries in series. That gives you 12 volts nominal at 220 A/H capacity over a 20-hour rate. The rate is important for lead acid batteries. Drawing at a faster rate reduces the voltage further due to internal resistance and reduces overall capacity. Same if you charge too fast. The voltage will rise before the battery actually charges and will be short charged, also reducing available capacity. AGM greatly improves this power delivery and charging resistance, but Lithium makes it almost disappear. If not for Lithium and related tech we still would not have electric cars.

[David 70]

I knew there were going to be problems when I done this but time constraints got me only part way to where I want to be. I was just wondering if there was any advantage to going with a higher amperage converter. As stated above I plan on more batteries so I will put a 60amp converter in so I can get a smart one. The one now is 20 years old, so it is old school. 60 amp is the smallest there is without going below 55.

[David 70]

Their advertising states they draw 11.6 amps at 12v (139 watts)

[Persistent]

Lots of good advice posted above.

Lead Acid Batteries

225 amp hours will last 225 ah / 11 a = 20 hours
Other 12 volt appliance will also use some of those amp hours.
Battery bank will be flat out dead after 20 hours.
It takes 14 to 18 hour to fully charge any lead acid battery.
You can probably get to 80% state of charge in 5 hours with a high capacity charger like your 55 amp charger.
You can probably not charge the 225 amp hour battery bank any faster.

Double the amp hours of battery capacity for better performance.
Double the capacity of the charger for the same charging times on the 450 amp hour battery bank. So, 100 amp charger would be useful for a 450 amp hour battery bank.

Lithium Batteries

Lithium batteries can be charged much faster. A higher capacity charger will be extremely useful for lithium batteries.
A 200 amp hour lithium battery may accept 100 amps of charging.
A 400 amp hour lithium battery may accept 200 amps of charging.
The battery bank may be fully charged and balanced after 3 hours using a high capacity "lithium capable" battery charger.

[David 70]

I am looking into some solar, but it gets really confusing once you start looking at the different setups. I need to start asking questions from the suppliers as to recommendations. E-Trailer sells Go Power that evidently is a Dometic subsidiary. I need to contact them and ask questions.