Upgrading to Lithium Batteries

[xrated]

Unless you are changing the charger to a higher amperage converter or adding additional draw devices, there really isn't a "need" to change out the wiring. Is it better? Sure. But it's unnecessary. Changing over to Lithium doesn't do anything to require thicker wires. Your fuses and such will all still work for a lithium battery.

Unless you are also planning on increasing converter ability that will exceed the current 6ga or otherwise increasing load, I wouldn't invest in thicker cable. The benefit will be minimal vs cost.

6 ga wire/cable has an ampacity rating of 55 to 65 amps, depending on the insulation class temperature rating of the wire.......choose wisely, or just take the worry out of it and go with a #4 ga wire.

[Txdabj1]

I just did this, a month or so ago.

Same trailer, same setup.


Two 100Ah Battle Born batteries and new, compatible 60-amp converter/charger.

There is also (if I remember correctly) a low-voltage detection circuit that has to be either added to the main circuit breaker panel or a new, replacement panel (with the circuit built-in) installed.

I was lucky - all my stock panel needed was a chip swapped out to add the detection circuit.


ALSO, the batteries were moved to the inside of the front storage compartment, across from the Nautilus.

There were several reasons for this:

1. It makes it harder to steal those expensive batteries

2. It keeps them warm, in the wintertime

3. It shortens the cables, reducing voltage loss (not much, but we are not talking mega-current, here)

4. It reduces tongue weight a smidgeon

5. No need to buy an additional/bigger/heavier battery box


Tongue weight on these trailers is always an issue, so any ounces you can save, do so! (Said he who added a washer and a dryer!)

A heavy, metal dual battery box is not the way I would want to go.


The stock 6-gauge cables are plenty big enough.

Unless you totally deplete the batteries and manage to get them to draw the max current out of the converter (meaning nothing else in the trailer is drawing current), you are not going to get any benefit out of larger wire other than peace of mind and a lighter wallet.

Don’t fret about voltage drop through the wire.

It IS a thing, but it is more theory than worry.

Less than a 1 volt voltage drop is not worth the time, money, effort or worry.


Your OCD may vary!


Bottom line: it ain’t necessary, but it won’t hurt.


The neat thing about these Battle Borns is that they have so many charge cycles that you don’t really have to be religious about how much goes in them how many times at what rate of charge or discharge or…

The things are going to last ten years, pretty much no matter how you use them.

Most folks will have traded units, by then.

Natajaagihe, how did you learn about the low-voltage detection chip and where did you buy it?

Thanks for that sage advice!

[Txdabj1]

Xrated, thanks for sharing your knowledge. There are a lot people that agree with you about increasing the size of the wire and it’s benefits.
I prefer to increase the wire size but I have to balance my preferences against my elevated blood pressure! I will be able to get a better idea how much of a challenge this will be after I get started on replacing the converter/charger.

[Txdabj1]

One more thing I will on this topic is changing out the converter/charger should be relatively simple. When I was assessing how much trouble this job was to be I just removed the metal grill in front of the furnace and the converter is right there in the front of the opening!

[xrated]

Xrated, thanks for sharing your knowledge. There are a lot people that agree with you about increasing the size of the wire and it’s benefits.
I prefer to increase the wire size but I have to balance my preferences against my elevated blood pressure! I will be able to get a better idea how much of a challenge this will be after I get started on replacing the converter/charger.

You're welcome. I know that this doesn't necessarily work for your trailer, but I did move my Converter/Charger (CC) quite a bit closer to the actual battery. Mine was in a space to the rear of the front baggage compartment and everything was 6 ga wire. I ended up mounting the new one in the front baggage compartment, overhead and shortened the distance by 6 or 7 feet. As you can see, two sets of wires coming off of the CC. The heavier gauge wires (#2 welding cable) go to the battery. The other set of two is the OEM wires (6 ga) and those go directly to the 12VDC fuse panel and are wired in parallel to the cables going to the battery. I have a Meanwell CC...NPB 750-12 and it is rated at 43 amps output. When charging my LFP battery and it is in Constant Current mode (Bulk charging), the battery is getting charged at a 42.xx amp rate. That is very, very close to the maximum that it is capable of providing.

Here is a pic of where I located the new CC.....Overhead in the baggage compartment.....

[A.Texas.Yankee]

6 ga wire/cable has an ampacity rating of 55 to 65 amps, depending on the insulation class temperature rating of the wire.......choose wisely, or just take the worry out of it and go with a #4 ga wire.

My point is there's no worry in it. Simply changing battery type and keeping same amperage of the converter will not have any difference on the amperage over the wiring vs stock configuration. The OEM wiring is sufficient (agreeably at the upper limits) and works in hundreds of thousands of campers. Fuses are all still the same to protect the 6ga wire (as long as it was all installed correctly, which is a different issue with the campers).

For Peace of Mind? Sure. But worry? I wouldn't, unless I was already ripping it all out for another reason.

[Najataagihe]

Natajaagihe, how did you learn about the low-voltage detection chip and where did you buy it?

Thanks for that sage advice!

I learned about it from the RV mechanic who installed it.

Since I had never heard of such a thing, I called Battle Born tech support and the first thing the guy said to me, when I asked about it, was, "Sounds like your tech knows what he is doing."

He verified it was needed, then went through the entire installation with me.

Key points:

Due to the ridiculously high cycle capacity of the batteries, the only thing I need to do is turn off the cutoff switch when I am not using the trailer.

This just minimizes the drain on the battery and the recharging necessary to bring it back up.

All those little discharges and recharges add up, over time.


Putting them in the storage compartment will, at least, delay the batteries from getting too cold to charge, if not eliminate that problem, entirely (seeing as I do not, willingly, stay in the trailer at freezing temperatures and the compartment is heated, when the furnace is on).

It, also, REALLY shortens the wire length from the solar controller to the batteries!

(Not to mention putting them closer to the charger, further reducing the necessity of larger wire.)

[Najataagihe]

Regarding the areas of you post that I have bolded above...

Oh, my!

I have not had such a good laugh since my last band practice!

Not for the reasons you may assume, but because I love talking to some one who actually knows something!


AND, you are, obviously, as OCD as I am, but in different areas.

ADD TO THAT, the fact that you would make a d@mned good technician (if you aren't one, already) just makes it a lovely day.

(To Hades with the engineers, build that puppy to last until the sun goes dark...)


You, my friend, are a man after my heart.


COUNTERPOINT:

And, now, we come to the difference between theory and use.

6ga wire is at the very edge of it's current carrying capacity when LFP batteries are installed...especially with a 60A capable charger output. If there are other 12V devices running and the Converter/Charger is trying to charge the battery, all of that current has to go through 6 ga wire. So ... less resistance per foot, can help cut down on the heating of the wire as it approaches it's current capacity.

Big deal.

"Edge of current capacity" is still within capacity.


First, you forgot to mention time. The longer it carries max load, the warmer it gets. This becomes important in a subsequent response.

Second, as long as you remain within the rating of the wire (plus the about 10% built into the standard for safety), you are good to go. That's why we have ratings, in the first place.

Third, max amperage ratings are always rated per foot, so as long as you are within the rated distance, it is a moot point.

You don't have to deplete the battery in order for the charger to go into bulk charging mode, not sure where you got your info on that one.

You misinterpreted my comment.

The reason for stating full depletion is that that is the condition most stressful on the wire because of the TIME it takes to recharge.

Full Depletion: 200Ah

Charging rate: 60Ah

Time to recover from complete discharge: 3 hours, 20 minutes

Theoretically.


So, since a #6 wire will carry 60 amps for 3 1/3 hours, it is well within specs.

Considering it is highly unlikely you are going to completely discharge those batteries, there is no need to worry about it.

You say not to fret about voltage drop....well, that's wrong also. A 1 volt drop will will be the difference between a LFP battery being fully charged, or not An LFP battery is considered to be fully charged at 13.8V...or 3.45V per cell. Most LFP chargers will output 14.5 to 14.6 volts, so a 1 volt drop takes that output voltage down to 13.5 or 13.6 volts, which is obviously less voltage applied to a battery that has to have at least 13.8 volts to be fully charged.

You are forgetting that, as the amperage goes down as the battery approaches full charge, the heat goes down (reducing resistance) and the voltage increases, eventually getting all the way back up to 14.5 volts.

Even if the voltage drop was only .7 or .8 volts and the battery got to 13.8 volts.....the length of time it would take to charge the battery would be greatly extended.

There you go!

It will still get there, it will just take longer.

All of those factors.....large enough wire, good low resistance connections, breakers, battery disconnects, are all a part of getting the most out of the charger and the battery.

Agreed.

My point is, considering the way the batteries are typically used in an RV in the OP's stated circumstance:

Is it necessary to get every possible erg out the system?

In my opinion, no.

In your opinion, yes.

Will any harm be done, either way? No.

Nothing I wrote above is opinion, it is factual information whether you choose to believe it or not......and that should pretty much address all of the bolded statements above.

Agreed, on BOTH counts!

We are in 100% agreement on the theory, just not on this particular application.

[xrated]

Oh, my!

I have not had such a good laugh since my last band practice!

Not for the reasons you may assume, but because I love talking to some one who actually knows something!


AND, you are, obviously, as OCD as I am, but in different areas.

ADD TO THAT, the fact that you would make a d@mned good technician (if you aren't one, already) just makes it a lovely day.

(To Hades with the engineers, build that puppy to last until the sun goes dark...)


You, my friend, are a man after my heart.


COUNTERPOINT:

And, now, we come to the difference between theory and use.


Big deal.

"Edge of current capacity" is still within capacity.


First, you forgot to mention time. The longer it carries max load, the warmer it gets. This becomes important in a subsequent response.

Second, as long as you remain within the rating of the wire (plus the about 10% built into the standard for safety), you are good to go. That's why we have ratings, in the first place.

Third, max amperage ratings are always rated per foot, so as long as you are within the rated distance, it is a moot point.



You misinterpreted my comment.

The reason for stating full depletion is that that is the condition most stressful on the wire because of the TIME it takes to recharge.

Full Depletion: 200Ah

Charging rate: 60Ah

Time to recover from complete discharge: 3 hours, 20 minutes

Theoretically.


So, since a #6 wire will carry 60 amps for 3 1/3 hours, it is well within specs.

Considering it is highly unlikely you are going to completely discharge those batteries, there is no need to worry about it.



You are forgetting that, as the amperage goes down as the battery approaches full charge, the heat goes down (reducing resistance) and the voltage increases, eventually getting all the way back up to 14.5 volts.



There you go!

It will still get there, it will just take longer.



Agreed.

My point is, considering the way the batteries are typically used in an RV in the OP's stated circumstance:

Is it necessary to get every possible erg out the system?

In my opinion, no.

In your opinion, yes.

Will any harm be done, either way? No.


Agreed, on BOTH counts!

We are in 100% agreement on the theory, just not on this particular application.

Thank you for the kind words....and just so you know, I gave up being a Technician upon retirement on April 30th 2020. Actually, "technician" doesn't quite describe it though. I spent 4 years in an Federally approved Apprenticeship program and topped out in Dec. 1980, so 40+ years as a Journeyman Electrician (Maint of Industrial equipment and 12 years on a High Voltage crew...4160V and 13.8Kv starter, contactors, switchgear, transformers, etc)

One other comment, I didn't "forget" the time factor with current flowing through the wire, and the wire rating is very likely the 60° temperature rated insulation, which puts it in to the 55A capacity for that wire. Throw in the higher temperature in the summer time inside of a closed compartment and/or underbelly of the trailer, and it's likely going to get pretty warm when the full charging current is flowing. And yes, I have OCD on some of those things for sure.

As a side note, and a bit of humor injected.....a person that is TRULY OCD........is actually ....CDO........Why?, because they are so ate up with OCD that they have to put the three letters in alphabetical order!

[Najataagihe]

...because they are so ate up with ocd that they have to put the three letters in alphabetical order!

YES! You understand!