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Old 04-19-2024, 07:41 PM   #1
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Upgrading to lithium

So I’m upgrading my battery to lithium and putting it under my dinette. Cables will be about 4-6ft in length. Thinking 4awg should be fine since I believe my inverter is just shy of 1000w.

This is on a 2016 Rockeood mini lite 2306
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Old 04-20-2024, 08:48 AM   #2
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Note that your 4-6 feet is actually 8-12 feet of wire for load calculations and wire sizing. Also note that the fuse protects the wire and should be sized for the wire and located near the battery.
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Old 04-20-2024, 09:24 AM   #3
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I would go bigger on wire.

Cause, you never know when the bigger inverter shows up. Only a few dollars for added wire and fuse.

My kid was experimenting with a single agm battery and a microwave.

With #2 wire no go. With 2/0 the microwave works.

With the bigger inverter you could just plug an extension cord into the inverter and plug the whole rv into it carefully!
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Old 04-20-2024, 09:59 AM   #4
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$45 for 4 ga (10 ft red, 10 ft black)
$108 for 2/0 (10 ft red, 10 ft black)

2/0 means you never have to replace the cables if you upgrade your inverter.

But to answer your question, yes 4 ga is fine for a 1000W inverter. 4 ga is good for 135A. Put a 150A MRBF terminal fuse on the battery for that 4 ga wire.
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Old 04-20-2024, 11:30 AM   #5
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$45 for 4 ga (10 ft red, 10 ft black)
$108 for 2/0 (10 ft red, 10 ft black)

2/0 means you never have to replace the cables if you upgrade your inverter.

Buy once, cry once.

I too would recommend the 2/0 wire so not only is the wire purchased once, the work to install it is only done once.
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Old 04-20-2024, 12:39 PM   #6
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Appreciate the info guys. This will be the upgraded inverter as the only reason I did it was to fully charge the lithium battery without having to go with a solar panel setup. Im fine with the ‘buy once, cry once’ mentality but I won’t be doing any other upgrades to this thing as far as power goes so I think I’ll just stick with the 4awg unless 2awg isn’t much more. Headed to the car stereo shop to have em cut me some lengths.
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Old 04-20-2024, 12:42 PM   #7
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Appreciate the info guys. This will be the upgraded inverter as the only reason I did it was to fully charge the lithium battery without having to go with a solar panel setup. Im fine with the Ďbuy once, cry onceí mentality but I wonít be doing any other upgrades to this thing as far as power goes so I think Iíll just stick with the 4awg unless 2awg isnít much more. H4 ga is good for 135A.eaded to the car stereo shop to have em cut me some lengths.
Do NOT let them sell you copper coated aluminum wires. Not good for this application. Get pure stranded copper wires. Welding cable is the best. Auto store battery cables are ok but very stiff.
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Old 04-20-2024, 02:04 PM   #8
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Do NOT let them sell you copper coated aluminum wires. Not good for this application. Get pure stranded copper wires. Welding cable is the best. Auto store battery cables are ok but very stiff.
I echo this. I made the mistake, once, of using "auto stereo" wire. Welding wire is best both thevcopper conductor and much better insulation that's chafe resistant.
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Old 04-20-2024, 02:04 PM   #9
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Originally Posted by CodyP View Post
So Iím upgrading my battery to lithium and putting it under my dinette. Cables will be about 4-6ft in length. Thinking 4awg should be fine since I believe my inverter is just shy of 1000w.

This is on a 2016 Rockeood mini lite 2306
Quote:
Originally Posted by CodyP View Post
Appreciate the info guys. This will be the upgraded inverter as the only reason I did it was to fully charge the lithium battery without having to go with a solar panel setup. Im fine with the Ďbuy once, cry onceí mentality but I wonít be doing any other upgrades to this thing as far as power goes so I think Iíll just stick with the 4awg unless 2awg isnít much more. Headed to the car stereo shop to have em cut me some lengths.
I'm confused by what you are saying here.

A con-verter takes 120v AC shore power, converts it to 12V DC power, and charges your batteries. An in-verter takes your 12V DC battery power and converts it back to 120v AC power so that you can use your espresso machine while fully experiencing the great outdoors.

Put another way, CONverter charges batteries, INverter discharges batteries.

Virtually every travel trailer is equipped with a converter from the factory. If it came with a battery, it came with a converter. Inverters are less common from the factory, unless we are talking about recent units that are specifically marketed toward boondocking - and those tend to come from the factory with some installed solar.

When you are plugged into shore power, your power center distributes 120v AC power to all of your "household-style" electrical outlets. It also feeds 120v to the converter, which then powers any 12v DC loads in the RV (lights, furnace fan, possibly fridge), while also charging the battery.

When you are not connected to shore power, your 120v AC outlets don't work. Also, the microwave, fireplace, and possibly the TV don't work. Your lights, furnace. and non-residential fridge will still work, but will be operating strictly off of battery.

If you are not connected to shore power AND you have an inverter, the battery still powers the DC stuff as above, but the inverter will be connected to one or more of your 120V outlets (probably not the whole trailer unless you have one much larger than the 1000 watt one you mention), and ONLY those outlets will work on battery power.

The INverter has nothing to do with CHARGING your battery(ies). (yes, I know that there are integrated inverter/converter power stations available, but the two sides still do their own separate duties)

Finally, a 1000 watt inverter only produces a little over 8 amps at 120 volts. That might run a small (800 watt) microwave, a small coffee maker, or a CPAP, but probably not at the same time. It most likely would not run a blow dryer. Also, anything that creates heat (coffee maker, crock pot, hair dryer, etc) suck battery power in a massive way when run through an inverter. The conversion efficiency of the inverter is not 100 percent, but even if it was, 1000 watts at 12v is 83 amps - which means that a 100 amp/hour LiFePo4 battery would be drained to 0V in about 72 minutes.

Many of the cable gauge answers in this thread seem to be based on your INverter terminology. You need big fat cables to move all of that amperage from the battery to the inverter. But if you really meant CONverter, your 4 gauge wire is probably fine.
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Old 04-20-2024, 03:05 PM   #10
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Sorry for the mixup. Maybe this will keep explain it better.
I bought a wfco wf-8955-AD-MBA Main Board Assembly because it has auto detect for lithium and will charge them fully.
WFCO guided me towards this but I believe it’s the same power capabilities as the stock one was. I also got rid my 12v agm deep cycle marine battery because it was too old anyways. I replaced it with 12V 200Ah LifePO4 battery that will go under the dinette.
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Old 04-20-2024, 06:37 PM   #11
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Sorry for the mixup. Maybe this will keep explain it better.
I bought a wfco wf-8955-AD-MBA Main Board Assembly because it has auto detect for lithium and will charge them fully.
WFCO guided me towards this but I believe itís the same power capabilities as the stock one was. I also got rid my 12v agm deep cycle marine battery because it was too old anyways. I replaced it with 12V 200Ah LifePO4 battery that will go under the dinette.
Ok, that makes sense. So you have a 55 amp converter then. The 4 gauge cable you are looking at ought to serve your needs then.

That's what I used when I replaced my 100a deep cycle lead/acid battery with 2 parallel 10a LiFePo4 batteries (based on the battery manufacturer recommendation) a couple of weeks ago. In my case I left the OEM converter in with the understanding that it will charge the batteries most of the way most of the time, and then I also bought a separate plug-in battery charger with lithium capability to top them off a couple of times per year.

The advice that was given upthread to use 2 gauge or larger was likely based on the misunderstanding about having an inverter - pulling 80 amps DC over 10 feet of wire would require larger stuff.

That said, (whithin reason) you can't harm anything by using larger than necessary wire. Up to you.
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Old 04-20-2024, 11:24 PM   #12
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I was In the same boat as you. I installed my battery under the dinette seating as well. I put positive and negative bus bars in the battery compartment and connected all the wires that were originally connected to the battery to them. Then just ran wires to the battery under the dinette.

I also installed a DC-DC charger in the battery compartment. I used 4awg wire from the battery to the terminal blocks. I do also have a 1000w inverter that was factory installed. So far all is good. If I upgrade the inverter I will run new wire straight to the inverter and not through the terminal blocks. Since the battery is now closer to the inverter then it was in the battery compartment.
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Old 04-22-2024, 06:09 PM   #13
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Ok so I ran into more problems. I decided to go buy 4awg wires and I put the life4po battery under the dinette. I unplugged the 2 battery wires from the battery box at the tongue at the fuse block pc board inside my main power center and replaced them with the new 4awg wires that ran to my new battery. I had no power for some reason. I had 13.8v at the battery terminals, then at the fuse block where the battery wires plug into I had 13.8v and same volts on the fuse block where the CONverter (I think?) plugs into but then nothing coming out of the converter and nothing at the circuit breaker where to converter plugs into.
I even tried swapping back to the old AGM battery but in the new under dinette location. Still no power.
I messed with the battery disconnect, which I thought would be bypassed since I ran new battery cables, but having it on or off didn't make any difference.
I then put the old tongue battery wires back on the fuse block and hooked the lithium battery up at the trailer tongue...which worked fine. So i'm not sure where my real issue is or if there is something stupid that I'm missing but my way SHOULD have worked.
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Old 04-22-2024, 06:26 PM   #14
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A couple of things. On the fuse panel where the converter and battery connections are there may be some reverse polarity fuses (probably not the problem here if switching back to the original battery worked).

I would check the negative side of things. My tongue battery connected to the frame at the tongue and the fuse panel connected to the frame below my fuse panel to provide the negative path between the two.
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Old 04-22-2024, 06:31 PM   #15
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A couple of things. On the fuse panel where the converter and battery connections are there may be some reverse polarity fuses (probably not the problem here if switching back to the original battery worked).

I would check the negative side of things. My tongue battery connected to the frame at the tongue and the fuse panel connected to the frame below my fuse panel to provide the negative path between the two.
Hmm...this seems interesting. I will have to dig into this cause it will probably be the issue. So maybe I still connect the original negative on the fuse block and then I'll just ground the battery inside to something and see if that works.
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Old 04-24-2024, 08:38 PM   #16
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Youíre amazing TacomaJoe. Knew it was something simple that I just overlooked. Grounded the battery to the trailer and hooked up the original ground from the fuse block. Everything works as it should now. Thanks again.
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Old 04-25-2024, 07:29 AM   #17
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Make sure the GROUND is to bare metal on the frame
improves the charging current a LOT

check where the converter attaches to the frame too
Once I got mine fixed.... saw a huge in increase in the current going into the battery when it is charging.

The factory method will allow the 12v stuff to work and the small current for charging Lead acid is OK too
BUT to reap the benefits of the Lifepo4 fast charging the negatives to the frame connections, need to be really good
Use zinc plated lugs + make sure they are TIGHT .... NO paint on the frame between lug and metal !

ONCE it is connected you can paint (spray or brush) any exposed metal to lessen chance of rust.
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Old 04-25-2024, 07:40 AM   #18
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Do NOT let them sell you copper coated aluminum wires. Not good for this application. Get pure stranded copper wires. Welding cable is the best. Auto store battery cables are ok but very stiff.
Dear God, do they still sell that! I was in the wire and cable business for many years starting in the Ď70s. It was a thing back then. I thought it was gone.
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Old 04-27-2024, 09:50 PM   #19
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Yep the ground is on bare metal. Itís good copper wire as well.
Realized my power jack doesnít work so it must have been wired to the front battery or battery disconnect. Guess Iíll have to tackle that now.
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Old 04-29-2024, 07:22 PM   #20
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Wire size

So I just purchased a 280ah Lipo4 battery to replace my two 6v batteries on my 2017 8327ss. I do not run an inverter and will replace the converter I have now with a 55a unit that is compatible with lithium. Is it okay to use the stock wiring with this configuration?
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