LifePo4 - drop in replacements. Anybody fitted?

[California_Ocean]

Problem with the lithium is that you will need a booster to charge it.
The alternator does not deliver the power consistently enough for a lithium battery.

You just need a booster and the battery. That’s all (exactly the same as every van in the world)…the Vw sistem will still show you the battery level (in volts) no problem. The only thing with that is volts are not really a good way to measure you’re lithium battery so you will need a Barrett with Bluetooth or shunt to know the real status of the battery

The alternator will deliver all the power it can, consistently, even if it is a smart alternator. It has to do with ohms law, V=IR ... the alternator will regulate to a set voltage, (which is not the optimum voltage for charging a Li battery) and the low internal resistance of an empty Li battery will cause massive amounts of current to be supplied by the alternator - which will cause an alternator to overheat and possibly burn out. With the engine at idle, there is insufficient cooling for the alternator to run at full load. Explained in this video:

Additional to limiting the load on the alternator, a DC-DC converter will charge the Li battery with the correct voltage and use a 3 stage charging algorithm - which will make your Li battery last longer.

 

[Corradobrit]

The alternator will deliver all the power it can, consistently, even if it is a smart alternator. It has to do with ohms law, V=IR ... the alternator will regulate to a set voltage, (which is not the optimum voltage for charging a Li battery) and the low internal resistance of an empty Li battery will cause massive amounts of current to be supplied by the alternator - which will cause an alternator to overheat and possibly burn out. With the engine at idle, there is insufficient cooling for the alternator to run at full load. Explained in this video:

Additional to limiting the load on the alternator, a DC-DC converter will charge the Li battery with the correct voltage and use a 3 stage charging algorithm - which will make your Li battery last longer.

There are voltage regulators builtin to the system that throttle the alternator output to prevent overheating scenarios you describe. The charge state of the batteries is not the variable controlling the alternators output.

 

[California_Ocean]

There are voltage regulators builtin to the system that throttle the alternator output to prevent overheating scenarios you describe. The charge state of the batteries is not the variable controlling the alternators output.

Generally, standard regulators on automotive alternators are not designed with direct charging of Li batteries in mind, they were designed to run a vehicle electrical system and top-up a lead acid starter battery in parallel. Li presents a real challenge to most automotive alternators due to the large charging current the battery will draw - connect a discharged Li battery to a standard alternator and the resultant smoke in the video I linked will be the result - even with temperature sensing, it will damage the alternator if permanently throttled and running in an over-temperature state.

In marine installations, smart regulators like a Wakespeed WS500 are often coupled with high-output alternators to overcome the shortcomings of a standard regulator and alternator when charging Li batteries (or large Lead Acid battery banks).

https://oceanplanetenergy.com/high-output-alternators/

I would certainly not recommend connecting Li batteries to a standard automotive alternator without a DCDC charger. One of the main tasks of the DCDC charger is to protect the alternator from the Li battery by limiting the load the battery can put on the system and in addition, the DCDC protects the Li battery by providing the correct charging profile for Li.

Unlike a lead-acid battery the internal resistance and corresponding voltage of a lithium battery does not rise until it is nearly 95% fully charged. This can cause alternators to run longer at full output which can cause alternator burnout. The length of a time a lithium battery can draw a constant current at or above the alternators max output can exceed the design parameters of the alternator. This can cause the alternator to over heat and burn-out. Alternators are internally cooled by a fan on its rotor. Lithium batteries will draw a high charge current at all times meaning alternators are prone to burn-out at low RPM when charging lithium batteries at high currents.

Can I Charge My Lithium Battery With an Alternator?

Unlike a lead-acid battery the internal resistance and corresponding voltage of a lithium battery does not rise until it is nearly 95% fully charged. This can cause alternators to run longer at full output which can cause alternator burnout. The length of a time a lithium battery can draw a...

solarboxaustralia.au

Additionally, one of the most fatal results of charging Li from alternators is when the Li battery BMS decides to disable charging (can be for a number of reasons related to the internal parameters measured by the BMS) ... this results in a load dump which will happily destroy most alternators.

 

[Wild Rover]

I’ve just fitted a pair of Renogy Smart Lifepo4 100Ah batteries with the Renogy combined DCC50S MPPT and DCDC charger, with 3x100W solar. The Renogy batteries used pouch cell technology, so they are bit smaller and lighter than most other manufacturers for the same power density.

The combined charger has some unique features and also some quirks to be aware of in the way it works, for example that it charges both a lead acid starter battery and the Lithium house batteries, and the algorithm it uses to distribute charge from the alternator and solar source when the engine is running is a little unusual.

It limits charge from the alternator to a safe level, as expected, and solar panels must be connected in parallel, and you may want a solar disconnect switch, the batteries also have lots of smart protection features.

There was a little minor fettling of connectors etc involved though. They had a sale on recently so it all became more cost effective than ever before. It has been powering my Starlink internet and recharging my ebike and powering everything without needing to run the engine, well worth the investment for me. Their flexible solar panels have been producing 327W in direct sunlight, which is fantastic and they are optimised for low light. Excellent value in my view. I live in my van and am super happy with the value for money Renogy offers.

Reviews…
Battery:

Controller:

Solar panel :

 

[Wild Rover]

I’ve just fitted a pair of Renogy Smart Lifepo4 100Ah batteries with the Renogy combined DCC50S MPPT and DCDC charger, with 3x100W solar. The Renogy batteries used pouch cell technology, so they are bit smaller and lighter than most other manufacturers for the same power density.

The combined charger has some unique features and also some quirks to be aware of in the way it works, for example that it charges both a lead acid starter battery and the Lithium house batteries, and the algorithm it uses to distribute charge from the alternator and solar source when the engine is running is a little unusual.

It limits charge from the alternator to a safe level, as expected, and solar panels must be connected in parallel, and you may want a solar disconnect switch, the batteries also have lots of smart protection features.

There was a little minor fettling of connectors etc involved though. They had a sale on recently so it all became more cost effective than ever before. It has been powering my Starlink internet and recharging my ebike and powering everything without needing to run the engine, well worth the investment for me. Their flexible solar panels have been producing 327W in direct sunlight, which is fantastic and they are optimised for low light. Excellent value in my view. I live in my van and am super happy with the value for money Renogy offers.

Reviews…
Battery:

Controller:

Solar panel :

Linked the wrong solar panel review video. Mine is a Renogy flexible panel, not rigid.