Adding an extra battery

[lchil02]

I have a 22 FR Vibe 34BH with 165W solar and a 30 amp Solar Controller to keep my 65W battery charged. I want to replace the battery with 2 100ah lithium ion batteries in parallel. Do I also need a dc to dc charge controller along with an inverter to run my 120v system?
Hoping someone can help!
My battery currently just runs my 12v fridge and slide outs.

[bikendan]

Moved thread from the Boondocking sub-forum to the Electrical, Charging Systems and Solar sub-forum since the OP's questions are specific to Electrical/Solar.

[TitanMike]

Originally Posted by lchil02

I have a 22 FR Vibe 34BH with 165W solar and a 30 amp Solar Controller to keep my 65W battery charged. I want to replace the battery with 2 100ah lithium ion batteries in parallel. Do I also need a dc to dc charge controller along with an inverter to run my 120v system?

Hoping someone can help!

My battery currently just runs my 12v fridge and slide outs.

Your current converter/charger will charge your new lithium ion batteries to around 85-90% state of charge and your current solar controller, when changed to lithium/LiFePo4 charge profile, will finish the job.

If you wish to charge the lithium batteries while driving ( towing ) then a dc-dc charger is highly recommended. Existing charge circuit from tow vehicle is severely limited in the amount of current it can deliver to trailer batteries so unless one drives all day the batteries will come up short for charge.

A dc-dc charger can be purchased for just over $100 and adding a larger (#6 or bigger) wire fron tow vehicle battery to trailer will deliver 20 amps plus, depending on size of dc-dc charger.

I've done this with my truck and trailer to charge my two LiFePo4 batteries and I always arrive at my next campsite with full batteries.

Sent from my SM-N950U1 using Forest River Forums mobile app

[2WheelJon]

TitanMike is spot on. I would take issue with one thing, however. If you’d going to spend the money on new batteries (LiFePO4s aren’t cheap) to it right and spend another couple hundred $ and get the specific charger for them. These new batteries charge at a higher voltage and have a different charging cycle than conventional lead-acid batteries.

Outside of that, I agree with TitanMike.

[tomkatb]

What’s the plan?

Where you live and play matters.

Compressor fridge rv’s are hard on batteries. “The weak link.”

You will consume o about 100 amps per day. A 200 amp battery bank will last two days. Weather dependent.

Out west solar works great. In the Midwest it rains, campgrounds are full of shade trees and solar can only supply 25 amps of charging per day per 100 watt panel. I would need 10. I use a cpap machine which is a big user.

So recharging might have to be at a campground or with a generator.

My wife discovered Harvest Hosts. So now we boondock! Last year about 20 days. We have a gas electric fridge.

I have a 420 amp gc2 battery bank and a generator.

What works in Colorado will not work in Ohio.

Study up. I like the 400 amp lithium batteries on Amazon and a generator. No solar.

Ask questions.

[lchil02]

I really appreciate the help! I am planning a trip to the Grand Canyon; staying every other day at an rv park with hook ups and the other days at a harvest host. Will a 200ah Lifepo battery handle the fan blower, fridge, and a cpap machine overnight?

[2WheelJon]

Originally Posted by lchil02

I really appreciate the help! I am planning a trip to the Grand Canyon; staying every other day at an rv park with hook ups and the other days at a harvest host. Will a 200ah Lifepo battery handle the fan blower, fridge, and a cpap machine overnight?

Find out the amperage draw of each of the devices you listed. Determine the approximate time each will run. For example, if the CPAP machine runs 8 hours and draws 5 amps it’s using 40 amp hours. Add all these numbers up and you will get the answer you’re looking for.

My two 100 Ah LiFePO4 batteries can run the furnace in 35 degree weather, water pump, lights, and 12 volt parts of my propane frig and hot water heater for more than two days without charging. But that’s me. Do the math to figure out your situation.

[tomkatb]

First question. Do you plug the cpap into a 12 volt outlet or 120 volt ac?

They use much more power on ac.

With the furnace, cpap and water pump plus the fridge likely you will use 150 dc amps per day or so. Every rv is different.

If you charge on Monday night and Tuesday morning you will be swell on Tuesday. Your battery will run out on Wednesday. likely at 2 am Thursday morning the DW is going to ask you why it seems chilly in the bedroom.

You need a battery monitor.

We have about 220 amps dc in four GC2 batteries. We have a gas fridge and a cpap on 12 volt. We can go two nights with some furnace. We use about 100 dc amps per day. Less without the furnace.