Upgrading existing RV lead-acid to LiFePO4?

[thebogeyman]

Be gentle with me. New to this :-D

I am looking to update my RV's 12V system. Currently have 4, 6V golf-cart batteries installed in parallel/series. It's been working pretty well, but the lead-acid batteries are now nearing the end of their useful life.

So, I am looking to grab a single 12V, ~400Ah LiFePO4 battery. Ultimate goal would be to install some solar, but for now, one step at a time.

We only boon-dock about 25% of the time, and I have a built-in generator in the RV, but currently no solar.

Am I right in guessing that I would also need to update/upgrade my RV's inverter/charger so that when plugged into shore-power (or running the generator), the LiFePO4 battery is being charged? The RV has a 5,500 W generator, and a 50A shore-power setup.

EDIT: I should also add that the current 12v lead-acid setup is used to start the generator when needed. Would it be recommended to keep a single 12V lead-acid battery for that (and use a DC-DC charger to keep it "topped up")?

 

[HighDesertOffgrid]

Am I right in guessing that I would also need to update/upgrade my RV's inverter/charge

What inverter/charger do you have?

 

[thebogeyman]

What inverter/charger do you have?

Not 100% sure. Whatever came with the RV (which itself initially only came with a single 12V deep-cycle lead-acid battery).

Like I mentioned, I converted the single 12V lead-acid, to 4, 6V lead-acid in series/parallel.

Just looked at an old pic from the RV, it looks like a WFCO-9855 "Power Converter". Interestingly, the blurb on their pages says:

WF-9855-AD Deck Mount Converter Charger - 55 amp deck mount converter/charger that DETECTS lead-acid or lithium-ion batteries and AUTOMATICALLY changes the charging profile based on the battery.

 

[thebogeyman]

I reached out to WFCO (https://www.wfcotech.com/). They stated that I do not have the "-AD", and that for a lithium battery, I would need to update to a charger/inverter that supports LiFePO4 chemistry.

They also suggested I avoid Amazon due to the proliferation of counterfeits.

Open to suggestions from the audience.

 

[HighDesertOffgrid]

You don't have a optimum situation for LFP.

The easy way:
If you choose to go with an LFP, I would recommend a Powermax 55 amp converter, switch it to constant voltage, and set the potentiometer to 13.8v.
Only charge above freezing. Connect to shore power for 24 hrs after boondocking to fully charge the battery.
There are more expensive and complicated options.

No battery or generator specifics so I won't address the starting issue.

 

[thebogeyman]

Thanks for the recommendation.

Agreed. Not an optimal situation.

But, to get the same capacity as a similar-sized LFP offers would take more space & weight that my RV's battery compartment has to offer.

The 4, 6V golf-cart batteries I currently have, while offering higher capacity that a couple of 12V batteries, weigh close to 350 lbs (I think around 80 lbs each), and take a lot of space. Not to mention the regular maintenance.

A LFP gives me considerably more overall power, along with the ability to run some (120V) devices via an inverter, which hasn't really been an option that made sense until now).

 

[littleharbor2]

Thanks for the recommendation.

Agreed. Not an optimal situation.

But, to get the same capacity as a similar-sized LFP offers would take more space & weight that my RV's battery compartment has to offer.

The 4, 6V golf-cart batteries I currently have, while offering higher capacity that a couple of 12V batteries, weigh close to 350 lbs (I think around 80 lbs each), and take a lot of space. Not to mention the regular maintenance.

A LFP gives me considerably more overall power, along with the ability to run some (120V) devices via an inverter, which hasn't really been an option that made sense until now).

You could've easily ran an inverter off 4 golf cart batteries. Short run time items like a Mr. Coffee maker or quick warm ups with a microwave oven are doable. Be sure to pour coffee into an insulated carafe and shut off the coffee maker. I would usually turn on my inverter at the beginning of my camping weekend and shut it off when packing up to leave. The key is having an inverter that is frugal at idle and not putting a big drain on your batteries.

 

[Road Dog]

If it were my rig i'd choose 2x 300Ah Epoch batteries. When paralleled will start the gen easily, have bluetooth monitoring and internal heating. I would add a modern 50A converter/charger with a LFP charge profile, and a Victron 50A DC>DC charge controller to charge from your alternator. This would be a solid system to replace the GC2 batteries with 1/2 the weight, 2x the available Ah, and zero maintenance. About $2500 all in.

 

[thebogeyman]

If it were my rig i'd choose 2x 300Ah Epoch batteries. When paralleled will start the gen easily, have bluetooth monitoring and internal heating. I would add a modern 50A converter/charger with a LFP charge profile, and a Victron 50A DC>DC charge controller to charge from your alternator. This would be a solid system to replace the GC2 batteries with 1/2 the weight, 2x the available Ah, and zero maintenance. About $2500 all in.

Thanks @Road Dog .

Not sure I would need the Victron you mention. I have a PD9360 ready to go (Amazon link).

This is all going in my 5th wheel / toy-hauler, which has a built in generator (Onan 5500), so hen that's running the batter will be getting charged. When I am not using the RV, it's stored at home, and plugged in to a 50A shore-feed.

 

[Bop]

Despite what many think- you CAN use your existing charging system on LFP batteries- but in the process you do lose some of the potential storage capacity (about 15-20%)- mind you that still gives you about 10-15% more than the previous L/A setup had (when new)...

If anything it is slightly 'gentler' on the LFP than using the 'proper' charge profile!!!

So you 'can' get away with using your existing charge controller, just ending up with a bit less actual storage capacity (shorter run times) than you could potentially have using the 'proper one nothing to stop you using your existing setup as is to begin with, and later getting a better solar/vehicle combined charge controller when finances allow and add some panels... (again, despite what many 'online armchair experts' believe, go a series high voltage array- you will get better performance than a low voltage parallel array- even with shading. lol- also MPPT only NEVER PWM!!! MPPT will give you 30% more daily generated power than PWM with properly matched panels (look at ALL the panel specs- not just the wattage- Voc or voltage open circuit can cripple a system especially if used with a PWM and the wrong panels!!!)


(been installing (and using) offgrid solar since the 1980's lol- indeed I'm living fulltime offgrid again and have been for the last three years- no generator required lol)