Battery Charging Question Using Charger w/ Shore Power

[jonshonda]

So I know my WFCO 8935 Converter/Charger isn't anything to write home about, so I want to use the dedicated battery charger I bought for charging my two 155ah GC batteries. I plan to wire a disconnect for the batteries when not in use, and I am not understanding if the converter will do what I want it to.

My question is: If the camper is plugged into shore power and I have the batteries disconnected from the trailer, will the converter have enough juice to supply my battery charger if plugged into the camper? Its a 15a charger.

I know Precision Dynamics makes a converter swap, but that puppy is over $200.

[A32Deuce]

First a converter converts 120 volt to 12 volt. Now you could hook up a charger and have the option of turning your converter off.

[Bama Rambler]

You can do what you're wanting if I'm understanding correctly.

You want to plug your RV into shore power and then plug your dedicated charger into a 120 volt receptacle on the RV. That will work assuming that you're plugged into 30 amp shore power. You would open the disconnect to isolate the batteries from the RV so the dedicated charger isn't trying to supply power to the RV. In that case, the converter will still supply 12 volt power to the RV but it won't be charging the batteries.

Assuming that your charger is 15 amps at 12 volts then it's only drawing about 2 amps at 120 volts with losses.

[jonshonda]

Originally Posted by Bama Rambler

That will work assuming that you're plugged into 30 amp shore power.

Not on 30a service. Typical home outlet.

[A32Deuce]

You need to know how much voltage your present converter is putting out. If not enough to keep your bats charged, then it may not be enough to run anything else.

[jonshonda]

Originally Posted by A32Deuce

You need to know how much voltage your present converter is putting out. If not enough to keep your bats charged, then it may not be enough to run anything else.

It's a brand new WFCO 8935 in my 2018 Roo. I can measure, but will assume it ain't gonna cut it w/ my big batteries.

[A32Deuce]

If its putting out 13.6 volts then it will charge any size bat. Just may take a little longer. Capacity of the battery is the difference. Amp hours and how run down will determine how long to charge.

[Bama Rambler]

Originally Posted by jonshonda

Not on 30a service. Typical home outlet.

You should be fine as long as you don't try to run any heavy current draw devices (A/C, Microwave, hair dryer, etc.). But that's the same even without the additional charger.

[jonshonda]

Originally Posted by A32Deuce

If its putting out 13.6 volts then it will charge any size bat. Just may take a little longer. Capacity of the battery is the difference. Amp hours and how run down will determine how long to charge.

It might be marketing fluff but Precision Dynamics disagrees pretty strongly with thinking that "any converter will do". They have been in the business for longer then I have been alive, and are know for good quality products.

Charge Wizard RV Battery Charging

[A32Deuce]

Then why do you have a WFCO and not a progressive.

[jonshonda]

Originally Posted by A32Deuce

Then why do you have a WFCO and not a progressive.

That is what came with the camper. Don't want to drop an extra 2 bills on one.

[A32Deuce]

The one with the camper well do what you need till it dies. Mine did, then I changed to much better!

[Herk7769]

So, dipping my toe in this water ....

The WFCO 8935 is a 35 amp 3 stage converter (meaning it will create 35 amps of DC current at maximum output).

http://www.americanrvcompany.com/ass...s/wf8900ss.pdf

http://www.americanrvcompany.com/ass...ges/wf8900.pdf

The converter will supply charging amperage to the battery based on its 3 stage charge profile. As long as there are no other 12 volt demands on the camper (lights, furnace, fans, etc.), the great majority of that current will be available to charge your batteries.

Will that converter charge a huge battery bank? Yes it will.

Will it fill it quicker than a WFCO 8955 (55 amps) or a WFCO 8975 (75 amps)? No, because more current will be available while in Bulk charge (stage 1 - Capacity below 50%)

Once the converter switches to stage 2 (Absorbtion - above 50%) the ability of the battery to accept current becomes the limiting factor determining how long it takes to charge the battery. Your WFCO 8935 can easily supply the 10 amps or so the battery needs in stage 2.

In "FLOAT" (stage 3 - 90% to 100%) - all converters are basically the same, providing 1-2 amps till 100%; then cycling on and off as needed to maintain 100%.

Charging "efficiency" is what folks talk about. The time it takes to go from zero to 100%. The bigger the converter, the faster you get to 50%.

[A32Deuce]

X2!

[Herk7769]

One other thing...

Folks talk about the Progressive unit with reverence because you can FORCE the converter to stay in bulk charge beyond 50%.

This is great if:

1) You closely monitor the flooded cell maintenance type batteries for water loss. Keeping the batteries beyond 50% in BULK will boil out the water and generate a fair amount of hydrogen gas. Be sure your battery compartment is open. Service your batteries regularly with distilled water.

2) Never use this feature with maintenance free type batteries (including AGM). These batteries do still vent from a small gas vent in the battery case when overcharged; you just can't refill them and once the plates get sulphated they are ruined. AGM batteries will get dry spots and caked sulphate in the glass mat shorting them out.

3) Only use with care when you are in a jam, knowing the risks you are taking with your battery.

[A32Deuce]

If you have to do something like that, take it out and use a bench charger. Being in a hurry is when bad things happen!

[jonshonda]

^Great info! I guess I have been conditioned to "think" WFCO converters are junk based on the negative reviews from boondockers and dry campers. Maybe their aren't "that bad". I want my batteries to get a full charge w/o loads, as I depend on them and have zero intention of using solar or a genset at this time.

I guess I will have to see how well the WFCO performs, or just keep charging with my off board charger.

[SidecarFlip]

Originally Posted by Herk7769

So, dipping my toe in this water ....
.

Careful Herk.. Dipping your toe in the water can cause nail fungus.....

[A32Deuce]

I don't replace anything till it brakes and I can't fix. I will research different systems, and if there is something that will go, then I may look for the best part/price and have it handy. There is a lot of good info on here, just have to weed through the chaff!

[TGR]

The data in Herc7769's tells me that there is no benefit in using a 15A battery charger when there is a higher capacity charger built into the WFCO converter. Just letting the WFCO do the charging without having to mess around with an external battery charger seems the best choice to me.