Added 4 100ah LiFePO4 in parallel to my TC. Truck is 94 Ford F-350 XLT crew-cab IDI 7.3 L diesel dually. Understand that these suck up juice so fast that ordinary alternator will burn out with this high draw. What to do? Other folks have this problem. Race cars, off road vehicles with banks of lights for night desert runs and ambulances with lots of medical equipment. Several manufacturers make high output alternators for this purpose. I checked with PowerMaster and Summit Racing who both said they had model to fit my truck and that it could handle the new battery bank. They have alternators for pretty much any year or model truck. Original alternator was 90 or 110amps. Not many amps needed back in the day, plus this one was at least 12 years old, so time to replace it anyway. Cost for high output alt is double at around $300 vs 150$. Alt delivered and note inside said it had been measured at 207 amp output. local garage installed it with no problems. Know that there are several ways to address problem, dc to dc etct To me they seem to restrict charging speed which is big advantage to these batts. Will this work? It should. Will find out. If I wind up on the side of the road I will let you know. Will be far from the bigger mistakes I have made in my 66 years.

Simple. Install a DC/DC charger in the alternator charge line to your rv battery bank. Victron makes a top notch one.P

If the wire is good those 4x LFP could absorb 400+ amps. What is really needed is an alternator that will limit amps and allow the voltage to sag and match the battery much like a standard battery charger. Balmer and Victron have regulators for the boating world that will actually limit the amps.

With high output race car alternator you do not need to be worried about too much output from it because that is what it is designed for. Will not burn out. Cannot overcharge and harm batt bank because the BMS(Battery Management System) stopes the alt from overcharging of the battery bank. Simple. Gives you the fastest charge available. DC to DC is useless and just slows down your charging.

retiredgeologist wrote:With high output race car alternator you do not need to be worried about too much output from it because that is what it is designed for. Will not burn out. Cannot overcharge and harm batt bank because the BMS(Battery Management System) stopes the alt from overcharging of the battery bank. Simple. Gives you the fastest charge available. DC to DC is useless and just slows down your charging.The BMS does protect the battery from over current and more. But that is not your case. Your batteries can be charged up to 400A and the alternator is 200A. And the engine etc need amps. Does your alternator limit the amps to 200A when the demand is higher? If not you may indeed end up on the side of the road.

How big is the charging wire from the truck to those batteries?

My new race car alternator for LiFePO4 batt bank

Grit_dog
Navigator
Sep 06, 2022
time2roll wrote:
Great to hear the alternator is working great for you.

Ditto
time2roll
Nomad
Sep 06, 2022
Great to hear the alternator is working great for you.
retiredgeologis
Explorer
Sep 06, 2022
No troll here. Been on site since 2007. Yes the Rv place made a mistake and installed European converter and replaced it. What’s this got to do with alternator debate?
What’s with all the attacks? Just wanted to post info on my new Lithium battery pack.
As for the charge lwire from alternator, do not know. But never had a problem and previous owner had hitch in bed for towing so I assume it is substantial. Have never had a problem and new high output alt is working great with new batt Lith pack.
If you want to debate this, fine, but name calling in not called for.
Bedlam
Moderator
Sep 05, 2022
Wire size depends on run length and desired amperage. There is not one answer to your question without more detail.
2oldman
Explorer II
Sep 05, 2022
I guess I'm not getting an answer.
Camper_Jeff___K
Nomad III
Sep 04, 2022
It is all about the internal resistance and admittence of the lifepo battery. Those batteries want a lot of current. The BMS is Lord and Master over those characteristics. The Victron has circuitry to deal with that accordingly. You can get an external BMS that may better regulate the output to input of your alternator. I have a 160 amp alternator with a 30 amp dc to dc. 30 amps limit is a good point when it comes to night driving with everything on. Headlights, windshield wipers,defrost compressor, heater blower on high, all the running lights, stereo cranked up. 30 amps leaves headroom for everything else to run if needed.
StirCrazy
Moderator
Sep 04, 2022
Ed_Gee had the answer, DC to DC charger.
pianotuna
Nomad III
Sep 01, 2022
retiredgeologist,

Even with 875 amp-hours of marine batteries I was able to "kill" two 60 amp fuses. They were fed by a #8 wire from a 130 amp alternator. (duty cycle 1/3)

After the 2nd failure, I replaced the fuse with an automatic 50 amp circuit breaker.

I did "double up" on the charging path adding a 2nd #8 wire connected to the starter battery--equipped with a 2nd 50 breaker.

I have a way to monitor charging up to 70 amps--and the circuit breakers did cycle under heavy loads. (an inverter running the 1400 watt electric water heater)

My loads would be tiny compared to the LiFePo4 batteries.

Make and model of the "racing" alternator would be useful.

Duty cycle for the alternator is???

Even if it is continuous duty, an automatic circuit breaker would be a nice addition--say 200 amps? (size wire appropriately)
2oldman
Explorer II
Sep 01, 2022
How big is the charging wire from the truck to those batteries?
CA_Traveler
Explorer III
Sep 01, 2022
retiredgeologist wrote:
With high output race car alternator you do not need to be worried about too much output from it because that is what it is designed for. Will not burn out. Cannot overcharge and harm batt bank because the BMS(Battery Management System) stopes the alt from overcharging of the battery bank. Simple. Gives you the fastest charge available. DC to DC is useless and just slows down your charging.
The BMS does protect the battery from over current and more. But that is not your case. Your batteries can be charged up to 400A and the alternator is 200A. And the engine etc need amps. Does your alternator limit the amps to 200A when the demand is higher? If not you may indeed end up on the side of the road.