LiFePo4 conversion

[Sailor now Trailer]

I am in the process of converting from flooded lead acid to LiFePo4 and have a few questions. I know a little about 12v systems but the switch to lithium introduces some issues (non-issues?) .
First issue is alternator charging while towing. Having spoken with two different people, as you might expect, I got two differing answers. First response was that lithium batteries appear as a "dead short" due to how much current they will absorb, causing the alternator to pump out amps to fill the perceived void, eventually burning out an expensive alternator.
Second person told me that because of the length of run to the battery in a 21C, he didn't see it as an issue, and thought it would be fine. After reading lots of threads, some have opted to wire in a DC-DC charger, which seemingly has a secondary issue of the emergency brake being disabled unless another wire is run? Others have simply taken the charging wire out of the equation. I would like to keep things simple and, because of the length of run to the battery, how much juice is actually getting to the battery? If this is an acceptable solution, i would take that route. Anyone who has eliminated the charge wire, how/where did you accomplish it?

I sized the ANL fuse at 250A, the battery is 280AH. Does that seem a reasonable size to use, the inverter is rated at 1500W?

Lastly, if I splice in the Victron shunt into the battery cable, will that account for amps going in/out? There is only two wires going to the negative post, the large cable, probably #2 at least, and a #10 I think, is the feed from the roof top solar panel? I understand all loads and power sources need to terminate opposite of the battery side of the shunt. Do I have that right?

Once again, thanks in advance. This forum is a valuable resource.

 

[Centex]

... Others have simply taken the charging wire out of the equation. I would like to keep things simple and, because of the length of run to the battery, how much juice is actually getting to the battery? If this is an acceptable solution, i would take that route. Anyone who has eliminated the charge wire, how/where did you accomplish it?

I'm one who elected to disconnect the 12V+ charging wire from my tow vehicle to the trailer.

Your 2016 21C may have a different type of junction box at the transition from the umbilical cord to the trailer wiring, but the principle should be the same. Your umbilical cord-to-trailer wiring junction box may be located on the trailer frame, or within the front of the trailer - just follow the umbilical cord to find it.

Simply disconnect and insulate the 12V+ charging wire from the umbilical cord at this junction, ensuring that all other wires at that connection remain intact with the rest of the trailer-side wiring. This eliminates charging from the vehicle while ensuring all other trailer functions (e.g. breakaway brake, etc) are unaffected. The disconnect is easily reversed (charging from vehicle restored) if desired at a later time.

Others have achieved similar results by pulling the 12V+ charging circuit fuse in their tow vehicle; my approach is trailer-specific, ensures that the tow-vehicle remains totally OE with no effect when towing other trailers. This approach avoids any potential 'fault detection' which may arise in some modern tow vehicles - the tow vehicle just behaves as it normally would when towing a trailer without a house battery.

Hope that helps, Have Fun!

 

[JohnK-ESC]

I too am one who has disconnected tow vehicle charging as part of the lithium mod. Unlike Centex I was not thinking about towing more than one trailer which I do not, so I made the disconnect at a relay under the TV hood. Making it trailer specific rather than TV specific is a good point Alan.

John

 

[dstreight]

I opted to utilize a DC-DC charger (Sterling 1260) and dedicated positive and negative heavy gauge leads from the tow vehicle's battery (2007 HD2500 & 1999 LandCruiser) to an Anderson Powerpole connector at the bumper.

Even with the 400A LFP battery in the Escape at or below 50% capacity, I've never seen more than 30amps flow from the Sterling into the battery even though the Sterling is rated to output up to 60A current. Alternator ratings: 145A & 100A stock alternators, respectively. I've never witnessed the LFP loading either alternator outside of their available capacity.

Yes, as long as all negative leads are on the upstream side of the Victron shunt (SmartShunt 500A) you will see both positive and negative current flow to the trailer battery. Utilize a simple busbar to eliminate stacked ground/negative terminals.

 

[Perry Butler]

ith

When I purchased our LiFePO4 batteries I asked mechanics from two different Ford dealers if I'll ruin the alternator. They claimed that the Ford alternator is "Smart" and it won't happen. I did find out the alternator was definitely "Smart". It provides 5 amps to my batteries the first 5 minutes of charging, but then essentially nothing after 5 minutes because it see's the AGM battery is at 14.8 volts (fully charged).

15 months, 200 nights, and over 16,000 miles pulling the camper with our LiFePO4 batteries and all is well.

Talk to a knowledgeable mechanic about your tow vehicle.

OTOH, we don't want or need a DC-DC unit.

Enjoy,

Perry

 

[Sailor now Trailer]

Thanks for your quick reply

 

[Sailor now Trailer]

Found this searching. It seems to me I read somewhere that the charging regimen for LiFePO4 and AGM's are pretty similar.
The 230 amp alternator controls the main truck battery in the Ram EcoDiesel, which is a 12 volt, 800 cca, AGM battery

 

[John in Santa Cruz]

Yes and no. LFP batts charge most efficiently with a ~ 50A charge up to 14.4-14.6 volts, hold that voltage an hour after the current drops to zero, then you can optionally drop to around 13.6V holding.

Most vehicles can't deliver anywhere near that current and voltage to a trailer.

 

[Sailor now Trailer]

Thanks for the photos, easy remedy!
Bob's your uncle ��

 

[Shadious]

Thanks for posting this, I’m about to pick up a trailer that had lithium batteries added and I needed to figure out how to keep from burning out our alternator. The pictures are perfect!

 

[77FJ40]

I am in need of new batteries. Wondering if now is a good time to upgrade to LFP? It seems like it would be fairly simple but things are rarely as simple as they seem. Is there a good thread outlining what needs to be done for the conversion?

 

[brroberts]

Just type lithium into the search box and you will have days of reading.

 

[GinoandLinda]

I am in need of new batteries. Wondering if now is a good time to upgrade to LFP? It seems like it would be fairly simple but things are rarely as simple as they seem. Is there a good thread outlining what needs to be done for the conversion?

There’s potentially a significant investment in transitioning from lead acid to lithium batteries. Judging by the age of your trailer, you will most likely have to swap you power center or at the very least your charger to one that accommodates the lithium charging profile. Then there is the interaction between your tow vehicle alternator and the possible need for a DC-to-DC connection converter. I had thought about doing this to our previous camper and when I factored in the cost of lithium batteries and locating them in a the coach to prevent theft, a new power center, DC-to-DC, yada, yada, yada, I was approaching 10-20% the value of the camper. That said, we have the whole lithium enchilada in our Escape 5.0 and love it. Wouldn’t go any other way.

 

[oldwave]

Cheap lipos are available a swap for the correct converter wifco is not very expensive (best converters has a drop in and it’s an hours work). If you’re worried about your alternator just disconnect the charging function at the trailer 7 pin box or make sure you disconnect the 7 pin after you stop so you don’t drain your vehicle battery from the lithium as it will try to charge unless you have a dc to dc device. . It’s not that expensive. 100 amp hour is equivalent to 180 to 200 amp hour lead acid as you can discharge deeper. They charge faster and if you have an inverter put out more continuous current. Downsides ? If you camp in cold weather you can’t charge under about 35 degrees unless you buy a heated version.

 

[Perry Butler]

I don't march to the same drummer as most here. We try to camp without services as much as possible, and camp winters when the temps get below 20F.

Things we found out you don't need:

Our WFCO converter crapped out on us, early in year two with our 5.0. I just pulled the fuses and charged with our 170 watt panel on the roof and a 100 watt portable for the winter months when we needed more power because the furnace is a amp hour hog. I did add 300 watts to the roof to eliminate needing the portable, but that's because I didn't want to deploy the portable all the time. Worked fine for our last three years (over 400 nights, with 1/3 in the winter with heavy furnace use). We don't have a converter running in our current Bigfoot either.

Didn't need a DC-DC controller from the truck to the camper. Our 2019 has a smart alternator, so a DC-DC is not needed, nor did we have to disconnect the charge wire from the 7 pin plug. The burnt up alternators were from old stock, before they became smart. Our 2015 also had a smart alternator. If you have an old truck go to your dealer and ask if the alternator is smart.

____________________________________________​

We ran our 5.0 for three years without a functioning WFCO controller. Your existing WFCO will charge a LiFePO4 battery to 80% and that's good enough. Solar provided us with plenty of power to keep any batteries balanced, 100% full 75% of the time, and was our only source of power for those three years. Invest in solar first!

We do have a separate Victron IP22 30 amp Smart Charger that can be used anywhere, for any standard camper configuration: standard leaded, AGM, SiO2, LiFePO4, etc. We did need it twice in winter 23 and once last winter.

We had a chance to move from 200 ah's of LiFePO4 to 412 ah's of LiFePO4 that cost us nothing, except to trade an expensive camper cover for the batteries. With 412 ah's, I doubt we'll ever need the portable or charger again. The IP 22 works fine with the 400 watt inverter in our F150 (set at 27 amps/hour).

If all we did was late spring/summer/early fall a 100 ah LiFePO4 battery would be just fine. It's that furnace and now my wife's CPAP that suck ah's.

Fun fact: unlike any leaded battery, LiFePO4 does not need to be charged to 100% all the time. In fact it's better for the battery if you don't. Buy enough capacity and you're golden. Once Terry got her CPAP we needed a larger battery bank. I advise campers today to purchase a 3-400 amp hour battery bank, especially before adding a DC-DC controller or a WFCO LiFePO4 converter. After having the Victron IP22 I'd never purchase the WFCO lithium specific charger. The IP22 is much more versatile.

We don't camp in hot, humid, oppressive weather, instead choosing winter/spring/fall, except for the family campout the end of June and a couple of other weeks in June or late August/September. So we don't need a genset when boondocking.

I chose not to waste my money on a LiFePO4 replacement charger (total waste IMO) or a DC-DC, and spend that money instead on more solar and a IP22 charger. Solar is the best investment you can make. Once installed it works 24/7/365. Works for us and many others.

Enjoy,

Perry