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Lithium and DC-DC Charger?

Ramblin__Ralph
Explorer
Explorer
My two group 27 lead acid batteries need replacing. Even though I'm too old to get maximum benefit from lithium longevity, I am thinking about going with a single 100 AH LifePO4 lithium. Doing some research it appears that a DC - DC charger is needed between the truck alternator and camper battery to protect the alternator. Would this still be required with only one 100 AH battery? Truck is a 2006 GMC 2500HD. Also have 125w of solar.

Thanks,
Ralph
Ralph
2006 GMC 2500HD, XCab, SB, 6.0L w/2001 Lance 845
Bilstein Shocks, TorkLift Stable Loads, 100 Ah LiFePo4, 225 watt solar
My RV Travels Webpage / Yearly Campsite Map / 740 Campsites / YouTube Videos /
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30 REPLIES 30

time2roll
Explorer II
Explorer II
NRALIFR wrote:
Would a lithium battery that’s being charged by a DC-DC charger that’s limited to 50 amps output and fused on the input side at 50, 60, or even 75 amps on the input side even need an LI-BIM?

:):)
The DC-DC rated at 50 would there in limit the charge current to 50 amps. However I recommend 80 amp fuse on the input and appropriate wire. These chargers do draw up to about 50% more if needed to put the rated output and voltage on the battery. So in a word, NO. You should not need an additional limit device.

deltabravo
Nomad
Nomad
I ordered the Renogy unit and returned it two days later. The reason for returning it was because it was too big for the extremely limited space in my AF992.

About the same time I returned it, I discovered Victron makes a DC to DC charger. It's smaller capacity, but will serve my needs. It's the Orion Smart TR 12-12 / 30 unit. Like all my other Victron kit, I can configure / monitor it through the Victron Connect Bluetooth App.

The Victron unit is about 1/3 the size of the Renogy.
2009 Silverado 3500HD Dually, D/A, CCLB 4x4 (bought new 8/30/09)
2018 Arctic Fox 992 with an Onan 2500i "quiet" model generator

NRALIFR
Explorer
Explorer
Would a lithium battery that’s being charged by a DC-DC charger that’s limited to 50 amps output and fused on the input side at 50, 60, or even 75 amps on the input side even need an LI-BIM?

:):)
2001 Lance 1121 on a 2016 F450 ‘Scuse me while I whinge.
And for all you Scooby-Doo and Yosemite Sam types………..Let’s Go Brandon!!!

wintersun
Explorer
Explorer
Add the Precision Circuits LI-BIM along with the lithium battery. It is sold by Battle Born and others and serves to protect the lithium battery from overly aggressive alternator charging.

A single 100AH lead acid provides 50AH of charge capacity for whatever you are operating off 12VDC. A 100AH lithium battery provides up to 100AH of capacity or double that of the lead acid. My RV only has space for two Group 31 batteries and so I removed the two flooded ones and put in two Lithionics 125AH lithium phosphate batteries.

An unexpected bonus is that the lithium recharge to 100% SOC is less than a quarter the time of the flooded batteries. The solar panels and charge controller is also more effective as more charge can be applied while there is enough daylight.

NRALIFR
Explorer
Explorer
Alex, I like your review of the Renogy unit. I’m glad to see more TC owners making use of them. In my opinion, they are just what some of us have been needing for years.

Your installation looks very much like mine using a Redarc 40 amp DC-DC charger. Mine has a solar input as well, which I’m not using yet but probably will at some point. I used 4 AWG wires on mine as well. It works very well, and I’m glad I went that route.

It’s nice seeing someone else come to the same conclusions I did about their value. You said “having the Renogy DC50s in your camper increases the likelihood of your batteries arriving at close to a full charge when you arrive at camp.” That is exactly what I’ve been saying about mine. I can’t overstate the importance of that for me. I need to be ready to dry camp for at least a few nights at all times, and arriving at my destination with a depleted battery just, at minimum, makes my job more difficult, and at times takes options off the table for me.

Thanks for the update on your install.

:):)
2001 Lance 1121 on a 2016 F450 ‘Scuse me while I whinge.
And for all you Scooby-Doo and Yosemite Sam types………..Let’s Go Brandon!!!

c_traveler2
Nomad
Nomad
Ramblin' Ralph wrote:
My two group 27 lead acid batteries need replacing. Even though I'm too old to get maximum benefit from lithium longevity, I am thinking about going with a single 100 AH LifePO4 lithium. Doing some research it appears that a DC - DC charger is needed between the truck alternator and camper battery to protect the alternator. Would this still be required with only one 100 AH battery? Truck is a 2006 GMC 2500HD. Also have 125w of solar.

Thanks,
Ralph


hi Ralph it's awhile since I've visited RV.net. I'll tell you about what I'm using that does both solar and dc-dc in a single unit and I've been using for over a year. I'm going post a link to the story I wrote for Truck Camper Adventure. If you don't have a compressor refrigerator one Lithium battery (100ah) should do you fine.

Renogy unit
2007 F-250 4x4 /6.0 PSD/ext cab/ 2020 Bunduvry

Lance 815/ 85 watts solar panel (sold)
2020 Bunduvry by BundutecUSA

Travelingman2 Photo Website
Truck Camper Trip Reports 3.0
travelingman21000 YouTube Videos
Alex and Julie's Travels Blog

deltabravo
Nomad
Nomad
NRALIFR wrote:
Even in a TC, the charging circuit to the camper batteries is surprisingly long, and while you can minimize the voltage drop, you can’t eliminate it. Install a DC-DC charger with adequately sized wires and forget about voltage drop entirely.


Ditto on charging cable upgrade. this is my project with 4AWG cables between the truck and camper.
2009 Silverado 3500HD Dually, D/A, CCLB 4x4 (bought new 8/30/09)
2018 Arctic Fox 992 with an Onan 2500i "quiet" model generator

NRALIFR
Explorer
Explorer
When I get on Autozone and look up an alternator for a 2002 F350 with a 7.3, I get a bunch of 110 amp alternators to choose from.

The better question however, is how many amps does the compressor fridge draw when running, then size the DC-DC charger a little larger. You could actually size it at exactly the same as the running amps because the compressor isn’t going to be running all the time normally. Don’t size it less though, you don’t want the charger to always be playing catch-up recharging the battery.

:):)
2001 Lance 1121 on a 2016 F450 ‘Scuse me while I whinge.
And for all you Scooby-Doo and Yosemite Sam types………..Let’s Go Brandon!!!

GULFMAN
Explorer
Explorer
I would like to do the same, charge one battle born 100amp battery to run a compressor refrigerator in the back seat of my truck.
Where can I find the size of my factor alternator in my 2002 7.3 powerstroke to determine the size of dc to dc charger.
Looking at dc to dc charger with built in mppt solar charge controller for when Setting still.
Any information Will appreciated.

Thanks

jaycocreek
Explorer
Explorer
Ralph,I was looking at that one also...I am still weighing everything out but that one seems like a good one for my use also and most likely the last battery I will ever buy...My group 27 house battery is starting to show its age..If you get it,keep us up on how you like it...
Lance 9.6
400 watts solar mounted/200 watts portable
500ah Lifep04

Ramblin__Ralph
Explorer
Explorer
Responses to comments since my last post:

- I already have a battery isolator under my hood
- Based on my previous experience with lead acid, I think a 100 AH lithium will fit my needs. No high draw items except for the furnace fan. All lights are LED.
- Have a variety of reasons for not sticking with lead acid : Last ones didn't last long; Won't have to check the water; Lighter weight for my old body; Most likely this will be my last set of batteries, so I thought I would try the "newest trend".

Was going to buy a $900 Battleborn, but checked Amazon and found a $540 one with very good reviews (due late Jan). Even if it doesn't last as long as a Battleborn, it will be long enough for me. 🙂 Probably will put in a 20 amp dc-to-dc charger.
Lithium Choice

Thanks for the comments. Always good to get other opinions.

Ralph
Ralph
2006 GMC 2500HD, XCab, SB, 6.0L w/2001 Lance 845
Bilstein Shocks, TorkLift Stable Loads, 100 Ah LiFePo4, 225 watt solar
My RV Travels Webpage / Yearly Campsite Map / 740 Campsites / YouTube Videos /
Instagram

DiploStrat
Explorer
Explorer
Some comments on lithium (iron) and battery to battery chargers (B2B).

Lithium iron batteries will take a LOT of current. As a test, at a battery manufacturer's shop, I connected a fully discharged, 100Ah lithium iron battery directly to my Chevrolet based Tiger. Drew 100A and, more to the point, kept up that high draw for nearly an hour. Never see charge rates like that with AGM. With a 250A alternator, I was probably safe as I normally use about 125Ah over night, but imagine the draw of a 300Ah battery bank after two days of rain.

B2B first became popular for charging deep cycle lead acid batteries on vehicles whose alternators were set to 13.9v. (E.g. many Toyota, Mercedes, etc.) Most B2B were relatively low amp (i.e. 20-30A) devices, but because they had proper charging voltages of over 14v, they worked much better.

Most American pickups already have charging circuits that run at over 14v, so their utility was limited. But with the new Euro standard and other energy saving circuits, they are experiencing a renaissance.

For lithium they can be ideal as, assuming the proper profile, they can provide the correct voltage and, since they cannot draw more than a certain amount of current (typically 10-20% above their rated output) they can prevent an overload of the factory alternator.

Hope this is useful.
DiploStrat

===========================

1990 Mercedes Benz 917/XPCamper

Website: https://diplostrat.net/

Tiger4x4RV
Nomad
Nomad
I like to think that I belong to the "if it ain't broke, don't fix it" school of RV tech. That makes me wonder what your issue really is.

Have your power needs changed? If no, you might just consider putting in new batteries of the same type you have. If existing batteries are not AGM maybe upgrade to those if their physical size allows them to fit where the old batteries are now.

Maybe you just want a project? OK. That beats COVID boredom.

Wanting to try the newest trend? OK. No shame in that.

Want to add charging from the engine? My 2006 GM truck has an isolator under the hood to keep the coach batteries from drawing down on the engine battery when the engine is off. The engine alternator (heavy duty) and shore power are my only two choices of power for charging the coach batteries. I rarely have shore power and the engine has done the job just fine since 2006. Yes, the Tiger is not a TC and is not demountable like your Lance, but there is undoubtedly a way to hook an isolator (I think they may be called separators now) into your system.

Happy trails whichever path you choose!
2006 Tiger CX 4x4, 8.1 L gas V-8, Allison 6-speed

pianotuna
Nomad II
Nomad II
ticki2 wrote:
This is probably a dumb question , forgive my ignorance . I have been reading about these new technology batteries , lithium and now Sio2 that can be discharged to 80 and 100 percent . How do they power equipment that requires 12v to operate like a furnace sail switch , at this state of DOD ?


BFL13 has iirc run a microwave from an inverter powered by a single 100 amp-hour SiO2 at 20% state of charge. The sail switch would be a tiny load compared to that.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.