Direct-Connecting deep-cycle Lifepo4 to LC200 Alternator ? (1 Viewer)

[cnd]

The specs on my LC200 Alternator says it puts out 14.6 volts and can handle 150A.
I'm planning 300AH or 400AH Lifepo4 batteries (to power my fridge, induction cooker, air-fryer, charge my eScooter, etc etc.)
I've already got 600W solar and a 50A MPPT charger.

It seems kinda crazy to spend huge money on a DC-DC charger to take my 14.6V from the alternator, and turn it into 14.4V for the batteries? (do they do anything else? if yes, can we believe their claims that they do?) It's pretty much guaranteed that the long cable run involved will drop those 0.2 volts anyhow? Not to mention, I don't think I can charge from solar and alternator at the same time, and the DC-DC are usually only 50A themselves.

I read @GLTHFJ60's experience:-

I have a custom (deep cycle) LiFePO4 setup in my truck, charging directly off of the alternator, for the past 2 years.

Is it possible/sensible/advisable to charge Lifepo4 direct from my alternator? What's the best connection strategy to disconnect the alternator when the vehicle is not running (or when the voltage at the Lifepo4 side reaches 14.4v / 100% or when the incoming current is pointless (like, 5A or less say) or when temperatures or other safety issues are detected) ? Do professional "smart" disconnect mosfets or relays exist for this purpose (if yes, what would they be called?)

Am I missing or forgetting something here, or is my understanding totally wrong?

I am very keen not to catch anything on fire of course or do anything (overly) sketchy, and I am also keen not to impact the charging on my (lead acid at the moment) starter batteries - and of course not to burn out my alternator (are they rated to put out 100% for extended periods?) - I have read a pile of people saying that disconnecting the Lifepo4 when charged will "destroy the alternator" and produce back-EMF etc etc... but I think those folk don't understand that "charged" means the Lifepo4 is more-or-less matching the alternator output voltage, so any "sudden" disconnect is going to be less than 10A or so - i.e. less than flashing your headlights anyhow.

 

[e9999]

don't know about the direct connection to the alternator but a few things come to mind:
- IIANM, my "12V" LiFeP chargers put out an actual 14.6V, not 14.4V
- AFAIK, it is normally not a problem to connect more than one charge controller to the same battery, the controllers just adapt to whatever battery voltage they see, so I would think it is not an issue to have the solar controller connected to a battery already connected to the alternator
- OTOH, are you sure your alternator does indeed put out 14.6V? That's a bit high for the expected lead acid starter battery

 

[Mrtwooooo]

I think you should also consider that if you just connect the lithium battery to the alternator then all that's going to happen is the battery will get charged and held at a constant voltage while the engine is running.
If you connect the lithium battery to the system using a DC to DC charger in the middle then the battery will be charged based on the charge profile for bulk charging and float charging states. Doing things this way seems like the lithium battery would be happier.

 

[e9999]

I assume that an LC200 alternator would have some sorts of smarts about it. Does it do anything special? And if so, how would that impact an additional connected battery?

 

[jgranthevagrant]

I'm looking at the same or similar issue. Direct connecting an alternator to a LiFePo4 battery. Apparently this can be hard on internally regulated alternators, as the Lithium batteries can accept a much higher charge than the lead-acid batteries, to the point that the alternator can't keep up, and burns out. Both Victron and Battle Born mention this in videos. I am not sure what the solution is yet, so let us know what you find out. I would rather not fry my alternator or the battery.

 

[spressomon]

After wondering about the same thing awhile ago I learned multiple charge sources operating simultaneously...work just fine for current flow to the battery. I use a Sterling BB1260 DC-2-DC charger and rooftop solar to charge a 7500Wh LFP battery in our Escape 15A trailer. And the Sterling serves as an isolator too. I use a Victron shunt to monitor the inflow/outflow of current into the LFP and can see the separate source current flow into the battery. I usually see ~20A flowing from the Sterling into the LFP plus another 15A flowing from the 400w rooftop array while motoring down the highway.

I don't know anything about the alternator in a 200-Series...whether its "smart" or not. But, the voltage output of any alternator will vary with engine speed as well as being impacted by resident load(s) on the alternator to power everything related to the 200. When we use our '07 Chevy Silverado HD2500 to tow, with its stock 160A alternator, I typically see ~20A current flowing into the LFP from the Sterling BB1260. One of these days I plan to swap in a Mechman higher output alternator...to be able to deliver up to 60A of current into the LFP.

Somewhat related/not related: My '99 UZJ100 with 100A alternator will rarely output more than 14.0v. I need to rely upon 120v chargers to keep the dual Odyssey AGM batteries in healthy condition relative to the charge voltage and profile they need (14.4+v depending upon battery temp) which is similar to the voltage needed for LFP. Keeping charge voltage & charge profile per the MFG's recommendation has paid dividends for the life span of these batteries with 10+ years realized.

Given the investment for all related equipment you are using, installing a DC-2-DC charger is the best strategy to protect your investment as well as provide proper charge profile for the LFP in addition to serving as an isolator along with protection for your alternator.

 

[jgranthevagrant]

I think that charge voltage contributed to the demise of my AGM. I think it was rarely at 14.4v from the alternator. My alternator (s) are old and not smart. 60 amp is the max output, but there are two running off the engine. My concern would be the LFP battery drawing too much from the house alternator, but maybe the BMS in the battery itself would prevent this?

 

[e9999]

What a source produces at any given time is a function of both source capability but also load demand, of course. If the source is well designed and the nominal rating meaningful, it should be able to produce that consistently, likely even continuously, so since it's unlikely that the LFP battery would often demand its maximum input current given its internal resistance and typical state of charge, I'm not seeing that an LFP battery would be much more taxing than a lead acid, especially given the BMS limitations on input current. A dumb lead acid battery may easily take up all the alternator's capability if it's very discharged or running a winch for example. The LFP BMS limitations may or may not match the alternator capability, of course, though. My newest 100Ah LFP battery has a limit of 100A in or out, so at least I know it's not going to draw more than 100A ever if the BMS does its job, and if the alternator is capable of more than that, then it's not an issue.

(Spresso: 7.5kWh with one battery...? How big is that thing?)


[Free (gratuitous?) editorial comment: I don't know why some folks seem to have such a hard time wrapping their heads around the idea that you can connect more than one charge controller / source to a battery. It's not like they will fight each other. Each controller/source has an algorithm that tells it to do something based on what they see the battery voltage is at any given time. They don't know what actual battery is there and why it does what it does, only the voltage, so having, say, 2 controllers, it will charge the battery twice as fast; well, no biggie, it's the same as if the battery was instead 1/2 the size as far as voltage changes seen by either controller, the controllers will be just fine with that and chug with it. When they see the battery is "full", well they will just simply wind down. (Oversimplifying a bit here admittedly.) ]

 

[LandLocked93]

Yes, it's a smart alt.

Not to mention, I don't think I can charge from solar and alternator at the same time, and the DC-DC are usually only 50A themselves.

Yes, you can. The RedArc BCDC does exactly that.
The charge algorithm in the BCDC is critical for maximum battery life.
The alt does not have or perform that algorithm.

 

[sdnative]

Yes, it's a smart alt.

Yes, you can. The RedArc BCDC does exactly that.
The charge algorithm in the BCDC is critical for maximum battery life.
The alt does not have or perform that algorithm.

I am not aware of any Land Cruiser alt that uses a smart alt (maybe the 300 series?). The 200 series is temperature compensating. The 200 series alt will drop down to low 13.xx volts when warmed up, hardly sufficient to directly charge a LiFePO4 battery.

I believe a LiFePO4 battery would live a long happy life with just bulk charging at 0.5C to 80-90% SoC. There is really no need to perform an absorption charge unless you are trying to squeeze that extra bit of energy in there.

 

[sdnative]

since it's unlikely that the LFP battery would often demand its maximum input current given its internal resistance and typical state of charge, I'm not seeing that an LFP battery would be much more taxing than a lead acid, especially given the BMS limitations on input current. A dumb lead acid battery may easily take up all the alternator's capability if it's very discharged or running a winch for example. The LFP BMS limitations may or may not match the alternator capability, of course, though. My newest 100Ah LFP battery has a limit of 100A in or out, so at least I know it's not going to draw more than 100A ever if the BMS does its job, and if the alternator is capable of more than that, then it's not an issue.

LiFePO4 batteries have very low IR, and can draw very high current if available. The BMS does not regulate current, it is just a switch that turns on or off depending on a number of monitored conditions.

Your battery may be rated at 100A (100Ah @ 1C), but again, the battery/BMS does not regulate that, and the battery will certainly provide more than that if the load demanded it (until the BMS opened on over current - if properly configured)

 

[Shoredreamer]

Lots of good info already, some other observations or info:

It’s not recommended to wire in parallel, lithium and lead acid. Two different chemistries act and function differently.

I know one consideration with charging lithium directly from an engine alternator is the charging amperage. DC to DC chargers have set charging max amps whereas alternators will output enough to match demand put on them. This unregulated charging amperage from an alternator may be too high for the Lithium BMS, causing a fault (open circuit), or damage (unprotected cells, BMS error). You’d have to check the battery BMS specs as well as the alternator max output and the do some ammeter measurements in various conditions to verify if this overcharging is a possible scenario. Ex: you want to charge a 110ah LiFePo4 with a 100amp max charge spec. You have a 150 amp alternator. There could be times where the alternator may be able to charge the LiFePo4 over the 100amps.

Opposite problem can happen where the lithium accepts so much current because of its low IR that it maxes out your alternator all or much of the time, potentially shortening the alternator lifespan.

Lithium is still so new in vehicle setups like this that much of this is still unproven or verified with what works or not. Heat, soc, cold, charge, cycles, discharging. I don’t think enough is known yet to what actually works and what damages or shortens the battery‘s life.

Deep Cycle Systems Australia makes some batteries that are built to charge directly via alternator, but those are sold on a case to case basis with a consultation, as some setups it will work for people and some vehicles/setups may not. ULTIMATE DCS 12V 260AH DUAL BATTERY SYSTEM (LITHIUM) – Land Cruiser 200 series (with MPPT SOLAR REGULATOR) - https://www.deepcyclesystems.com.au/product/ultimate-dcs-12v-260ah-dual-battery-system-lithium-land-cruiser-200-series/



I’ve been tempted to try lithium as a starting battery, like this crazy 6c starting/winching battery 12V 80Ah Extreme battery (LITHIUM) - 80ah Deep Cycle Battery - https://www.deepcyclesystems.com.au/product/12v-80ah-extreme-battery/ but with an already existing dual battery setup, I don’t see enough advantages in it for my setup. May be a cool option for someone who hasn’t already built a start/house electrical setup since you can have both starting and house duties on one battery.

 

[LandLocked93]

Don't forget that lithium has a 'flammability issue'. For several reasons that many EV manufacturers are hesitant to reveal.
It is responsible for sinking several car ferry ships thus far - which also happens to be where I draw the line.
I'm generally disinterested in ship-sinking technology installed in my rig. lol

 

[e9999]

^ the LFP batteries don't suffer from the same fire issues AFAIK.

 

[spressomon]

^ correct. LiFePO4 (lithium iron phosphate) is relatively benign compared to LiPo (lithium polymer) as it relates to fire risk.

 

[Vintij74]

investigating these alternator charging issues takes up lots of camping time. My 55amp alternator goes to an Optima AGM under the truck bed & then to dual Victron DC DC chargers that maintain 200AH LiFePo. Normal use hasn't taxed the battery capacity more than 15%. Ran house fridge from my truck inverter for 6hours during an unannounced brown-outs. The biggest concern was that the alternator would cook....and it didn't even get warm while idling engine for a few hours. Also considering a 1999 80A alternator upgrade, w a 50 ammeter in cluster. Just want more time to finish every other project.

I'm considering 400AH to assist w FCAW mobile welding, though I would need at least a 3000W inverter. A portable generator is too tempting for some out there

 

[Vintij74]

investigating these alternator charging issues takes up lots of camping time. My 55amp alternator goes to an Optima AGM under the truck bed & then to dual Victron DC DC chargers that maintain 200AH LiFePo. Normal use hasn't taxed the battery capacity more than 15%. Ran house fridge from my truck inverter for 6hours during an unannounced brown-outs. The biggest concern was that the alternator would cook....and it didn't even get warm while idling engine for a few hours. Also considering a 1999 80A alternator upgrade, w a 50 ammeter in cluster. Just want more time to finish every other project.

I'm considering 400AH to assist w FCAW mobile welding, though I would need at least a 3000W inverter. A portable generator is too tempting for some out there

Edit: OTOH, the Victron DC DC chargers do get hot, so addition heat sink helps. If 120V or solar is available, keep batteries charged and balanced w a nice Victron hardwired charger when parked

 

[LandLocked93]

@RUSH55 you deny what I stated to be true?

 

[RUSH55]

@RUSH55 you deny what I stated to be true?

No. I lol’ed with you at the end.

 

[FrazzledHunter]

The guys who sold me my upgraded alternator recommended this brand as a drop-in replacement for my OEM stock lead acid starter battery.
Their claim is that my new alternator and the OEM alternator I replaced would properly charge these batteries.
There's also a feature on them where they have a self-jumpstart capability. I dunno how it works.
I may upgrade to it one day.

"All Antigravity Automotive Batteries offer much higher power and are ultra lightweight compared to the lead/acid batteries they replace."
REF:
AUTOMOTIVE LITHIUM BATTERIES - https://antigravitybatteries.com/productline/starter-batteries/automotive/