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 > Lance TC - lithium - DC-DC charger question

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orourkmw

Port Allen, LA USA

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Posted: 05/13/22 03:53pm Link  |  Quote  |  Print  |  Notify Moderator

I’ve just purchased a 2020 Lance 975 that will sit in my 2022 F350. I have to install the Lance 6-pin at the front of my bed. I will also replace the two 12V lead acid house batteries with one 200 ah LiFePO4. The Lance has a battery separator, which appears to be installed just upstream of the house batteries. I think I need a DC-DC charger to protect the 270A alternator (as well as to get charging benefits), and am considering 30A-40A. Lance specifies at least 8 gauge hot and ground wires from the truck to the 6-pin. I am thinking that to protect the alternator from a large current draw, ideally I should run 2 or 4 AWG wire from the truck battery all the way to the DC-DC, and back, and not connect to the 6-pin plug (so skip the 8 ga). I think CamperJeff explained the potential complications of feeding the 6-pin. I would mount the DC-DC at the battery box, which is ~4 foot from the pin connector, so I’ll have to see how to feed the wire through. My questions are these: First, am I understanding this properly? If I can keep the battery separator in-line and ahead of the DC-DC, can I avoid the D+ signal wire that the DC-DC uses to isolate truck from house? I think the DC-DC only takes as large as 6 ga, so I’ll need to narrow down as close to the end as I can manage. Is there still a risk of overheating when running lighter gauge wire between the relatively short run from the battery isolator through the DC-DC to the LiFePO4? Any guidance would be appreciated.

Lwiddis

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Posted: 05/13/22 04:02pm Link  |  Quote  |  Print  |  Notify Moderator

If your roof has sufficient space, solar would be easier. Another option is a AC to DC Lithium charger if your truck has a 120 volt plug that is hot when driving. Mine is a 10 amp charger.


Winnebago 2101DS TT & 2020 Chevy Silverado 1500 LTZ Z71, WindyNation 300 watt solar-Lossigy 200 AMP Lithium battery. Prefer boondocking, USFS, COE, BLM, NPS, TVA, state camps. Bicyclist. 14 yr. Army -11B40 then 11A - (MOS 1542 & 1560) IOBC & IOAC grad


theoldwizard1

SE MI

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Posted: 05/13/22 06:00pm Link  |  Quote  |  Print  |  Notify Moderator

You are overthinking this !!

If you install a DC-DC charger (highly recommended) immediately upstream for the batteries you will no longer need a battery separator. You should not need larger wire either. Your DC-DC charger will act as both a separator and limit the amount of power that can be drawn from the truck.

Add a gauge and shunt on the output side of the battery so you know how much charge it has.

orourkmw

Port Allen, LA USA

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Posted: 05/13/22 06:10pm Link  |  Quote  |  Print  |  Notify Moderator

Yeah, my wife accuses me of over thinking it often! So I could just use the 8 gauge wire and go into the 6-pin plug? That would sure be simplest.

time2roll

Southern California

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Posted: 05/13/22 07:16pm Link  |  Quote  |  Print  |  Notify Moderator

Protect the 270 amp alternator from what? I bet the charge line fuse is 40 amps and it will not have any trouble.
I can't tell if the plan is to push more amps or to limit-reduce amps.

I recommend to connect as designed and see what goes. I think the OEM system will be fine.


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orourkmw

Port Allen, LA USA

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Posted: 05/13/22 08:20pm Link  |  Quote  |  Print  |  Notify Moderator

My main goal is to make sure I don’t burn up the alternator and get stranded. But also, on my last two campers the charge I got from my alternator was minimal. With a compressor fridge (NovaKool) on my last camper I would end a day driving 10% under the SOC where I started, even with 200 W solar. I would like to have a 30A charge or so go into the batteries while we’re rolling (even though I’m back to a 3-way fridge). It sounds like the system as described will be ok on both counts. I’m ordering the Victron 12-12/30 amp Smart DC-DC, and will hook up 8 ga 6-pin. Thanks for the clarity.

theoldwizard1

SE MI

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Posted: 05/14/22 12:15am Link  |  Quote  |  Print  |  Notify Moderator

orourkmw wrote:

Yeah, my wife accuses me of over thinking it often! So I could just use the 8 gauge wire and go into the 6-pin plug? That would sure be simplest.


time2roll wrote:

Protect the 270 amp alternator from what? I bet the charge line fuse is 40 amps and it will not have any trouble.


What he said ! The DC-DC charger also limits the power draw.

Next truck, don't waste your money on the oversized alternator.

mbloof

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Posted: 05/14/22 11:45am Link  |  Quote  |  Print  |  Notify Moderator

+1 over thinking it.

Back in the day, my buddy bought a Lance. Included in the installation was a 8AWG wire ran from the battery to a 50-100A solenoid (switched on/off with the ignition/engine running) a 40-50A fuse and 8AWG wire from the fuse to the Lance connector. He could easily run his fridge on DC and/or charge his house battery(s) with the truck running. Granted this setup won't charge the camper battery(s) all the way because of voltage drops/loss of the wiring+connectors.

Keep in mind that for current to flow there needs to be a voltage difference.

Fast forward to 2021 and LiFePo4 batteries are all the rage. While IMHO they are a better option then FLA batteries by all accounts, they do need/require a higher charge voltage then FLA batteries.

While there are a number of options available to accomplish this a popular one is to employ a DC-DC charger. (there are a number of different OEM's that make them and each have a number of different models to choose from)



- Mark0.

3 tons

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Posted: 05/15/22 10:51am Link  |  Quote  |  Print  |  Notify Moderator

You need only be concerned what the alternator is capable of on a continuous basis, and the accepted norm for this is 25-30% of it’s nominal rating. So for a 270a alternator, the acceptable range would be somewhere between 67 and 81 continuous amps, so having two 200a/r Lithium’s myself (based on charge monitoring…) I in this regard, I don’t see how you’ll have any kind of problem - JMHO

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Grit dog

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Posted: 05/15/22 11:40am Link  |  Quote  |  Print  |  Notify Moderator

I sometimes have to just giggle at responses like "next time don't waste your money on the HD alternator...."


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