RV install Input.

[deffords40]

( there are better options at an added cost. )

I'd be all ears for anything you recommend as useful in the hybrid paradigm.

I was studying the MarineHowTo "Easy LiFePo4 Conversion" article, which seems to get mentioned fairly often. That recommends the Orion XS DC-DC. Definitely a better unit, but only charges in one direction. I liked that the Renogy is bidirectional to keep the lead topped off, should I go for an extended period without running the engine (she's heavy but supposed to be a sailboat).

These guys over at Sterling did a video about a single LiFePO4 giving the business to an alternator just a handful of minutes into charge.
No lithium dropout, just pulling too much current.

 

[grizzzman]

I'd be all ears for anything you recommend as useful in the hybrid paradigm.

I was studying the MarineHowTo "Easy LiFePo4 Conversion" article, which seems to get mentioned fairly often.

I have followed Rod years ago. He is a great resource.

That recommends the Orion XS DC-DC. Definitely a better unit, but only charges in one direction. I liked that the Renogy is bidirectional to keep the lead topped off, should I go for an extended period without running the engine (she's heavy but supposed to be a sailboat).

I myself prefer the Victron architecture and individual components myself.

These guys over at Sterling did a video about a single LiFePO4 giving the business to an alternator just a handful of minutes into charge.
No lithium dropout, just pulling too much current.

If it were me I would install a large case alternator with an external adjustable voltage regulator outside of the engine compartment. ( This will remove a fair amount of heat away from the alternator) Set up to charge the LFP bank then the DC to DC charger set up to charge the FLA bank. LFP will accept higher amps much longer than the FLA bank. This is a big deal if you want to limit engine run time for charging. I prefer separate components. This assumes that you want the two banks separated.

 

[Stircrazy]

I'd be all ears for anything you recommend as useful in the hybrid paradigm.

I was studying the MarineHowTo "Easy LiFePo4 Conversion" article, which seems to get mentioned fairly often. That recommends the Orion XS DC-DC. Definitely a better unit, but only charges in one direction. I liked that the Renogy is bidirectional to keep the lead topped off, should I go for an extended period without running the engine (she's heavy but supposed to be a sailboat).

These guys over at Sterling did a video about a single LiFePO4 giving the business to an alternator just a handful of minutes into charge.
No lithium dropout, just pulling too much current.

that's a very old video now and it was rigged up to make that happen, look at the setup. in a vehicle you would never be able to put that much draw on an alternator as the fuse would blow first. that is pure sales propaganda.

 

[deffords40]

that's a very old video now and it was rigged up to make that happen, look at the setup. in a vehicle you would never be able to put that much draw on an alternator as the fuse would blow first. that is pure sales propaganda.

And if the vehicle is a boat?

 

[HRTKD]

And if the vehicle is a boat?

I would hope there's a fuse there too!

Victron did a similar video. I picked it apart a few years back. It's an extreme case but there are cases in the Ford/RV community of a LiFePO4 battery bank killing a set of alternators.

 

[HarryN]

that's a very old video now and it was rigged up to make that happen, look at the setup. in a vehicle you would never be able to put that much draw on an alternator as the fuse would blow first. that is pure sales propaganda.

The challenge is that if you blow the main fuse on an alternator - the voltage will spike and the most likely result is a blown alternator, as well as some of the attached electronics.

Modern automotive alternators are operated very differently than an alternator even 20 years ago. The size of modern Li battery banks in vans and RVs, especially in a low SOC - start to look like an energy black hole to the vehicle power system.

There is even enough difference between a 2016, 2017, and 2023 Ford transit to approach each one slightly differently.

 

[deffords40]

If it were me I would install a large case alternator with an external adjustable voltage regulator outside of the engine compartment. ( This will remove a fair amount of heat away from the alternator) Set up to charge the LFP bank then the DC to DC charger set up to charge the FLA bank. LFP will accept higher amps much longer than the FLA bank. This is a big deal if you want to limit engine run time for charging. I prefer separate components.

Got it. Externally regulated alternator into LFP house bank, into DC to DC, into starter lead acid.

This assumes that you want the two banks separated.

What if you want to combine?

Yes I have been running a hybrid system going on for 6 years now. My system has been directly connected to both banks ( types ) for over a year full time now. I use nothing for separate charge/discharge cycles. The charging systems are all set to LFP charging profiles. Many here said that you could not connect FLA to LFP but I did it anyways and it works just fine for me.

I have to engage in some interpretive liberties to mentally piece together how the hybrid system on your trailer now operates. Is it that you combined both FLA and LFP when both were fully charged (to prevent runaway current flow across disparity)?

And then charge both according to an LFP charging profile, as you note, which implies the FLA never sees the higher 14.4 voltage and/or extended absorption phase of traditional lead-acid charging?

HOWEVER- because lithium's resting voltage is higher than that of lead, and because the two systems are never taken apart, the lead in fact sees a constant elevated voltage "charging pressure", which is essentially the resting voltage of fully charged lithium.

Everything works out fine as long as either-
A) during use, the lithium (mostly) stays at its elevated voltage relative to the lead (and this should be easy since - if I recall - a 20% state of charge lithium battery begins to approach the resting voltage of fully charged lead; as long as you run the lithium batteries between 100% and 20% state of charge, they are still above the voltage of fully charged lead)
Or B) the entire bank gets fully charged and then spends significant amount of time at that fully charged state (wherein the voltage pressure of fully charged lithium is allowed to work on the lead for a sufficient period of time before next discharge occurs).


That's my best guess. What's actually happening?

I myself prefer the Victron architecture and individual components myself.

Which components have you had the best luck with?

 

[grizzzman]

Got it. Externally regulated alternator into LFP house bank, into DC to DC, into starter lead acid.

Correct

What if you want to combine?

I do not have enough info to advise you.
Keep in mind that at the very least the starter battery should be isolated from the house bank.

I have to engage in some interpretive liberties to mentally piece together how the hybrid system on your trailer now operates. Is it that you combined both FLA and LFP when both were fully charged (to prevent runaway current flow across disparity)?

I will make this simple. The LFP bank(s) are directly connected to the FLA bank 24/7/365. The charging ( mostly solar ) is set up for 14.2/13.6 (float well pass though ) as well as the mains charger. ( very rarely used )

And then charge both according to an LFP charging profile, as you note, which implies the FLA never sees the higher 14.4 voltage and/or extended absorption phase of traditional lead-acid charging?

The truth is that you have mostly used up the LFP capacity ( unless your LFP bank is small and large loads are applied ) by the time you make use of the FLA bank.
I started my adventure with a DIY 150 AH and a 208 AH GC2 banks so when I brewed coffee or ran the microwave the FLA bank would assist for a bit. I now have added 300 AH of additional LFP so I do not see much coming out of the FLA bank anymore. If for any reason the LFP(s) banks shut down I am not in the dark. ( highly unlikely now with the added 300 AH bank.

HOWEVER- because lithium's resting voltage is higher than that of lead, and because the two systems are never taken apart, the lead in fact sees a constant elevated voltage "charging pressure", which is essentially the resting voltage of fully charged lithium.

The FLA's built in resistance due to it being fully charge along with a short absorption time and the fact that it drops to 13.6 negates the " overcharging" issue. Remember at 13.6 the FLA bank is floating. ( This is the happy spot for FLA )

Everything works out fine as long as either-
A) during use, the lithium (mostly) stays at its elevated voltage relative to the lead (and this should be easy since - if I recall - a 20% state of charge lithium battery begins to approach the resting voltage of fully charged lead; as long as you run the lithium batteries between 100% and 20% state of charge, they are still above the voltage of fully charged lead)
Or B) the entire bank gets fully charged and then spends significant amount of time at that fully charged state (wherein the voltage pressure of fully charged lithium is allowed to work on the lead for a sufficient period of time before next discharge occurs).

Well essentially the FLA bank gets at least in my case a trickle charge all night.

View attachment 241825
That's my best guess. What's actually happening?

Yes.

Which components have you had the best luck with?

Victron equipment is robust, interconnects so all charging, inverter, control components through in my case Bluetooth and is incredibly adjustable and also has presets for quick set up.

 

[SoggyShoes]

So @grizzzman or anyone else, then could a LFP be used as a "trickle charger" for a starting battery during storage?

I have a 12v 304Ah LFP and am wondering if that could be a way to maintain my RV starting battery. I would only hook the charged LFP up to the starting battery when storing (never when the engine is on). It would be isolated from the house and 24V battery systems.

 

[deffords40]

So @grizzzman or anyone else, then could a LFP be used as a "trickle charger" for a starting battery during storage?

I have a 12v 304Ah LFP and am wondering if that could be a way to maintain my RV starting battery. I would only hook the charged LFP up to the starting battery when storing (never when the engine is on). It would be isolated from the house and 24V battery systems.

Appears so. By voltage, it appears you could connect them at any state of charge as long as LFP voltage > starter voltage. The danger appears to be rate at which LFP accepts charge, but that won't happen from a standing lead acid battery with its lower voltage even when fully charged. Or the rate at which LFP can discharge current, but that won't happen either due to internal resistance of lead acid battery. But I can only repeat what I've read.

Maybe ask this guy on youtube. He'd probably rig it up to see. Batteries that refuse to explode were made for him.

The charging ( mostly solar ) is set up for 14.2/13.6 (float well pass though ) as well as the mains charger.

My boat presently has a lead acid starter battery, two 6v FLA trojan T-105s in series for a 225Ah house bank, and another lead acid in the forepeak for the windlass. Perkins 4108 diesel and a 100amp internally regulated alternator. I began a week or so ago thinking I'd just hang one or two LFP 100Ah batteries off the house using Clark's bank manager.

But then the issue of overdrawing the alternator came up. I should also say my first trip will be motoring 1300nm up the Atlantic coast in a "new to me" boat, and so am hording cash for the unexpected rather than extensively upgrading components.
Clark has a video on modifying a stock alternator which I've watched more than once. The discussion of the modification is described in 1 or 2 sentences and is over in about 10 seconds. I probably shouldn't dive into it, since the timing before the trip and margin for error is slim. Prior owner cruised the boat all over the caribbean extensively, including motoring for days between the Mexico, Belize and the US. The systems, as is, should get me home. Just need some extra capacity for laptop / internet and remote employment while making it home.

The next idea was the internally regulated alternator into the lead acid starter battery, and from there the less expensive renogy DC-DC charger into a new lithium house bank and bypass the 6v FLAs.
Now, I'm thinking they can be used. Alternator into starter, with DC-DC to a busbar with the two 6v FLA in series and new LFP connected in parallel directly - never to come apart. Clark's idea is overly complex, as long as the charging sources into the hybrid bank are set to lithium charging profiles.

On that note, I'll post the video I wanted to share. Did you see Rod Collins "15 year old lithium battery update"?

Minute 9:45 -18:00 or so. He charges to 13.8v at .4C, holds for 1 hour of absorption. And floats at 13.5, sometimes. Other times, no float.

 

[Stircrazy]

The challenge is that if you blow the main fuse on an alternator - the voltage will spike and the most likely result is a blown alternator, as well as some of the attached electronics.

Modern automotive alternators are operated very differently than an alternator even 20 years ago. The size of modern Li battery banks in vans and RVs, especially in a low SOC - start to look like an energy black hole to the vehicle power system.

There is even enough difference between a 2016, 2017, and 2023 Ford transit to approach each one slightly differently.

the problem is it doesn't even remotely show how it would work if we were charging a battery from an rv with the alternator. you figure the length and size of wire plus the usually 40 or 50 amp fuse on the trailer charging circuit, there is no way you are going to get enough amperage to blow the alternator little lone charge your battery properly as the voltage drop will be horrible and the output of the alternator is wrong.

now people add things in like larger wiring and dc to dc chargers, but if your doing stuff like that, I would hope you know enough to put the safeties' back into the system to prevent this from happening, its all part of knowing what the minimum standard you should be doing, or don't do it.

like I said this was intentional set up as a marketing tool for their products, very short heavy guage cables, a battery that would accept a large amperage charge, no fuses and so on... is it possible, yup but so is winning the power ball