Battery Charging question - WFCO vs dedicated Battery Charger

[dbarks]

Greetings:

I am looking for some advice on the best way to recharge my batteries.

- 2021 22MLE with WF-8735 converter / charger
- 1 75ah AGM, adding a second battery (still deciding on a second 75ah AGM or maybe a Lithium)
- Dry camping for 2-3 nights occasionally - for the purpose of my question let's use the example of 3 nights in Rocky Mountain National Park in July (no hookups)
- I have an inverter generator - generator hours are 7:30 to 10 and 4-8:30
- Want to run furnace all night and then recharge during the day

So...

I have read info on running a furnace all night on batteries ~6.5amp per hour when furnace is running etc.

I am concerned that even if I can run the furnace all night, propane fridge and occasional LED lights and water pump - I won't have enough generator hours to charge the batteries back up.

So is it faster to use 2 dedicated battery chargers (say 8 amps) or run the batteries in parallel (get a second matching AGM) and have the WFCO do all the charging?

I have thought of getting a second Lithium (since they charge faster) and run the Lithium all night and switch back to the AGM during the morning generator hours and and charge the Lithium during the day since it will charge faster?

[MoonShadow_1911]

Greetings:

I am looking for some advice on the best way to recharge my batteries.

- 2021 22MLE with WF-8735 converter / charger
- 1 75ah AGM, adding a second battery (still deciding on a second 75ah AGM or maybe a Lithium)
- Dry camping for 2-3 nights occasionally - for the purpose of my question let's use the example of 3 nights in Rocky Mountain National Park in July (no hookups)
- I have an inverter generator - generator hours are 7:30 to 10 and 4-8:30
- Want to run furnace all night and then recharge during the day

So...

I have read info on running a furnace all night on batteries ~6.5amp per hour when furnace is running etc.

I am concerned that even if I can run the furnace all night, propane fridge and occasional LED lights and water pump - I won't have enough generator hours to charge the batteries back up.

So is it faster to use 2 dedicated battery chargers (say 8 amps) or run the batteries in parallel (get a second matching AGM) and have the WFCO do all the charging?

I have thought of getting a second Lithium (since they charge faster) and run the Lithium all night and switch back to the AGM during the morning generator hours and and charge the Lithium during the day since it will charge faster?

First, I love RMNP! I grew up backpacking all over RMNP above Georgetown.

Now, do not mix battery types. Especially LiFePO4 and any other type. Charge rates, Ah, and other factors can potentially cause issues with either battery, like over charging or over heating.

If you go with 200 Ah of LFP4 batteries, that will most likely get you through one night. You will want to swap out your WFCO charger to a LFP4 compatible charger. Something else to remember as well, with the proper LFP4 charger, a "dead" battery can be fully charged in about 4-6 hours, give or take.

If you go with adding another AGM battery, that might last you all night and, with a 12V automotive fast charger, connected to the generator, will still take you 10-12 hours to fully charge the AGM batteries.

Just remember whether you use the onboard charger or an automotive charger, when using a generator to power the chargers, it naturally puts out 12VDC, then converts it to 115VAC, then converting it back to 12VDC via the converter or battery charger.

My recommendation is to bite the bullet and go LFP4. (I'm still trying to convince the wife to do this!)

As for switching between the two types, I think that would end up being a PITA. Just my two cents, adjusted for inflation.



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[Scott'n'Wendy]

Agree with everything Moon said...except I have no idea what RMNP means.

But I think you are over estimating how much battery your furnace will use. It will not be running ALL night.
I get through the night with the 'el cheapo' dealer installed battery. Temps of 30-40*F.
87ah best I can calculate. Nobody was proud enough of the battery to put their name on it.
A 200ah LiFePO4 would undoubtedly be much better.

[xrated]

Agree with everything Moon said...except I have no idea what RMNP means.

But I think you are over estimating how much battery your furnace will use. It will not be running ALL night.
I get through the night with the 'el cheapo' dealer installed battery. Temps of 30-40*F.
87ah best I can calculate. Nobody was proud enough of the battery to put their name on it.
A 200ah LiFePO4 would undoubtedly be much better.

Rocky Mountain National Park would be a great guess!

[Ynot4me2]

Agree with everything Moon said...except I have no idea what RMNP means.

But I think you are over estimating how much battery your furnace will use. It will not be running ALL night.
I get through the night with the 'el cheapo' dealer installed battery. Temps of 30-40*F.
87ah best I can calculate. Nobody was proud enough of the battery to put their name on it.
A 200ah LiFePO4 would undoubtedly be much better.

Rocky Mountain National Park = RMNP
I also agree, go straight to LifePo4 and change the charger to lithium compatible. Progress Dynamic is highly reviewed on here and will recommended a replacement for the WFCO.
I never dared to try one evening running a furnace on the dealer group 24.
I'm going lithium is soon as I can for this reason. I've read that the WFCO charger in the 22mle is built in to the panel so there's a little extra work that needs to be done.

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[jmbopp]

Three trailers ago I installed a deck mount IOTA-55 converter to supplement the single stage Elixir I had. That converter is now mounted inside the hookup center in our Imagine, charging two 6V batteries along with 200W of portable solar with a Honda 2000i generator as a final backup.

The WFCO doesn't readily go into bulk mode so it makes a poor charger for running off a generator, hence the upgraded converter. The factory WFCO is still installed but turned off at its breaker.

This has worked well enough and I can't justify the switch to lithiums with the associated costs of a new converter, solar controller, and DC-DC converter.

[Riverbug]

Three trailers ago I installed a deck mount IOTA-55 converter to supplement the single stage Elixir I had. That converter is now mounted inside the hookup center in our Imagine, charging two 6V batteries along with 200W of portable solar with a Honda 2000i generator as a final backup.

The WFCO doesn't readily go into bulk mode so it makes a poor charger for running off a generator, hence the upgraded converter. The factory WFCO is still installed but turned off at its breaker.

This has worked well enough and I can't justify the switch to lithiums with the associated costs of a new converter, solar controller, and DC-DC converter.

Don't want to start an argument here or anything, just want to point out that it isn't actually a requirement to purchase a new converter, solar controller, and DC-DC charger because a lithium battery is purchased. You can simply replace the existing battery with a lithium battery without doing anything else and you can still get benefit from it. Naturally, a lithium charger will charge faster and to full capacity vs the WFCO stock converter charger. And if you want more, you can add solar and/or DC-DC charger. But none of these things are required. I installed an SOK 206 AH battery last June and did not replace the stock charger or add anything else yet. This spring I am adding a DC-DC charger and a lithium converter/charger/inverter because we will spend more time unhooked. Anyway, just didn't want OP to believe that investing in a lithium battery means an immediate investment in all those other things is required. You can do those things without lithium batteries too. I do agree with others that say lithium and AGM together are not ideal though.

[Victory1]

I have a 2022 Imagine 2800BH. I currently have the dealer installed flooded lead acid battery at about 100ah in my rig. We spent a total of 3 night boon docking on the last trip we took. All three nights were separated by nights we spent plugged in so the battery was as charged as it could get when we boon docked.

Temps at night were in the 40-45 degree range and we set the thermostat as low as it would go - 60. Although the heater ran through the night the battery fell below the 50% mark and probably pretty close to 20%. I believe I did some damage to the battery due to depth of discharge. On the third boon docking morning I didn't have enough battery capacity to run the slides in or run the tongue jack. I had to plug the trailer into the truck to run these things.

I have decided to put a lithium bank in the 300ah range with a 60 amp converter in my trailer. I think with the limited charge time you will have, lithium would work well for you.

Certainly a second LA battery and a supplemental charger may work just fine. The issues I see with that route are charge times and depth of discharge.

If you are going through the expense and trouble of adding a lithium battery and compatible charger, that would have to run separately from the LA battery, ( as others have said you shouldn't mix battery types in the same system) to your existing set up I would ditch the LA battery altogether. After running through the options I have chosen the lithium route.

Good luck with your decision!

[AZMike]

Agree with everything Moon said...except I have no idea what RMNP means.

But I think you are over estimating how much battery your furnace will use. It will not be running ALL night.
I get through the night with the 'el cheapo' dealer installed battery. Temps of 30-40*F.
87ah best I can calculate. Nobody was proud enough of the battery to put their name on it.
A 200ah LiFePO4 would undoubtedly be much better.

Wow, you must be lucky (or I'm not lucky)! Before I switched to LiFePO4, I was barely able to get a night from my original battery. There were a couple of times I had to hook the jumper cables to my truck battery just to get the slide in in the morning. Was my battery bad? Maybe, but I didn't care anymore since I made the lithium upgrade.

[dbarks]

Thanks for all the comments.

So to try and summarize:

My main question: If I run the furnace all night how long will it take to charge the battery so I can run it again the next night.

Recharge times - FLA - slow, AGM better, Lithium fastest. Moon says ~10 hours for FLA. That is too long to run the generator so that is no good.

Scott 'n' Wendy say you won't run the battery down in 1 night. So I am thinking 2 new AGMs with some charger time and some solar might make it 3 nights. I might try that. If I am wrong, no more boondocking for me. Risky business.

Buying a 100 ah Lithium is also a possibility. Lots of good comments. This is no doubt the future.

BTW - I asked the WFCO guys how many amps they charge at (I wanted to compare to the 8 amp charger I have and they said:

"Hi Daniel,
The output is variable, up to 35 amp, and depends on how discharged the battery is."

I asked then again - 35 amps?? I thought that was not too good for a FLA or AGM to be charged like that.

They said all the power will go to the battery less any other consumers (lights, pump etc.) that happen to be on.

Honestly, I find that hard to believe. So if I plug into my generator and I get 35 amps going to the battery, seems like it will charge in no time. Comments welcome on that one.