Thread: D4 - Lithium AUX battery under the bonnet.

Originally Posted by drivesafe

Hi Folks and first off, my apologies to the OP, he was not visiting Tamborine Mountain, it was actually Briar who was planning the visit.


To that end, any update on your visit Briar?

I did go up to Tamborine Mountain but as no one had asked for any specific info from DCS I didn't feel compelled to go. We did a a couple of small walks to Curtis Falls and the Skywalk. The Skywalk is quite well done and worth a visit. Lunch at St Bernards overlooking the valley. Very pleasant. Still a bit of a hot day, so went back to the air con.

Originally Posted by drivesafe

Hi Sean, how do you charge the lithiums while driving?

Enerdrive EN3DC40+ DCDC charger.

Hi folks and sorry for the delay in replying but I am flat out.

If lithium batteries are so good as cranking batteries, why is it that not one single vehicle manufacture is using them. And if someone does know of any, please post it up as I have not found one.

This is a strange situation when you consider that they could replace a 100Ah lead acid battery with a 25Ah lithium battery and achieve the same starting CCA.

This would give the manufacturers a cranking battery of less than 1/4 the size, probably less than 1/5 weight and with a theoretical life expectancy well over that of the manufacturer’s warranty period.

So again, why is it that not one single vehicle manufacture is using them?

The above aside, here are some things to consider, if you are leaning towards using a lithium battery as a cranking battery in a vehicle specifically designed to use a lead acid cranking battery.

PLEASE NOTE, the following is “THEORETICAL” as I can not find any genuinely useful data on vehicles using lithium cranking batteries.

With most new vehicles having some form of SMART alternator operation, there are some unanswered potential problems that I see occurring in most vehicles makes, not just Land Rovers, but the following is based Land Rover operation.

First and foremost, the BMS in a Land Rover is specifically setup with algorithms designed to charge and maintain the lead acid cranking battery while also reducing exhaust emissions.

To do this, the BMS monitors the cranking battery in a number of way, with the primary monitoring of the battery’s voltage, at startup and the current draw of the battery after startup.

If the BMS determines that the cranking battery is fully charged, it will step down the operating voltage of the alternator. this can have the alternator running at 12.8v and even lower in some cases.

This is the NORMAL operation of modern alternators and at 12.8v, the vehicle’s electrical needs are still being met by the alternator while no additional unnecessary energy will be absorbed by the battery.

The lower voltage means the vehicle’s power needs are being met at the lowest energy rate, and the battery is drawing no energy, so the total exhaust emissions are as low as possible.

Being as the operating voltage of any lithium battery is 13.1v ( minimum ), until the battery is near flat, if the BMS “sees” that the battery is at 13.1v, and “thinks” the battery is fully charged, within just a few minutes of starting the motor, the alternator voltage will drop to under the 13.1v and as such, your vehicle’s electrics are now running off the lithium cranking battery and the alternator will be contributing no energy at all.

Around town, this may or may not be a problem, but say you leave on the first day of your big trip, and you drive for 5 hours, to get to your first overnight stop.
You could easily be running off your lithium battery for that 5 hours.

The reality is that you could not run off a single lithium cranking battery for 5 hours. You would be lucky to run much over 2 hours, “IF” the battery was fully charged in the first place.


Just before Christmas, I had a customer phone me with what, at first, sounded like an alternator problem.

He had just arrived home after his final leg of his trip. He had been camping overnight before his 5 hour trip home, but on the way home, his Traxide Dual Battery system's In-Cab Module started flashing 5 short reds and a long green.

This indicates that the battery voltage was somewhere between 12.45v and 12.7v while he was driving.

I have had customers on numerous occasions, phone me about this happening while driving, and in most cases, it is just the vehicle’s BMS running the alternator at a lower voltage because the cranking battery was in a fully charged state.

But on a number of occasions, customers have called me and told me the flashing LEDs had tipped them off that their alternator was failing.

When this customer told me he had been camping the night before, and therefore, his batteries would not have been fully charged. So even after a 5 hour drive, the voltage should not have dropped so low and my assumption was the he may have an alternator problem.

After a few more questions, he told me that on his last night, he had been on a powered site and all his batteries would have been in a fully charged state at the beginning of the days drive.

So his D4’s BMS had determined his cranking battery was in a fully charged state and shortly after starting the final drive home, the BMS lowered the alternator’s operating voltage.


So in this type of scenario, when the BMS lowers the alternator’s operating voltage to anything below 13.1v, as the lithium battery’s voltage is now the highest voltage source, it will be supplying all the vehicle’s electrical power needs.

Even with two 75Ah lithium batteries, a 5 hour drive will take them to a near flat state at 12.7v, but even though the lithium batteries are now down to the alternator's operating voltage, the BMS will not increase the alternator voltage above 12.7v ( and could be as low as 12.45v ), because the BMS will still “think” the cranking battery is fully charged.

From this point on in the trip, the alternator will supply the vehicle's power needs at the lower voltage, as it is intended to, but because the voltage is too low to charge the lithium batteries, they will remain low and near flat.

So you could quite easily arrive at your first nights camp with two flat lithium batteries.

This is just one scenario, but imagine if you are towing a caravan with a DC/DC device charging the vans batteries, and the problem just became so much worse.

There are just too many unanswered questions about using lithium batteries as cranking batteries in most new vehicle’s, not just Land Rovers, and none of these sellers seem to be interested in putting up info about these potential drawbacks on the websites.

You asked. I delivered.
Porsche have had it as an option in the GT3 for over ten years. It’s not a cheap option, but available. And yes, it’s not in the engine bay as such so it’s not exposed to heat, which is the point of this to be fair.

Porsche AG: World Debut: Starter Battery in Lithium-Ion Technology - Porsche Middle East

Thanks for that and here is a YouTube clip about that $5,000 battery.

Porsche Motorsport Lithium Iron battery LiFePO4 all you need to know - YouTube

BTW, an interesting point made in that video, was that the vehicle's BMS ( Battery Management System ) operation had to be reprogrammed to allow proper use and charging of the lithium battery.

This is something that can not be done in any Land Rover's BMS and can only be done on a few other makes. Most new vehicles having no way to alter their BMS operation.

It is this specific inability to be able to modify the BMS that has the potential to cause quite a few problem, that these sellers are not addressing.

A real irony is that older vehicles, those that do not have SMART alternators, will actually be more suited to having a lithium cranking battery. But will still have some potential problems, if the lithium battery is not monitored in some way.

Originally Posted by drivesafe

BTW, an interesting point made in that video, was that the vehicle's BMS ( Battery Management System ) operation had to be reprogrammed to allow proper use and charging of the lithium battery.

This is something that can not be done in any Land Rover's BMS and can only be done on a few other makes. Most new vehicles having no way to alter their BMS operation.

Is this purely a programming thing, or would some change in hardware also be required?

Smarter folk than me have worked out how to program out the EGR valves, and change the engine ECU for more output etc - could an additional battery type profile into the BMS CCF (noting there are several there for the global market already) be that far from viable?

Hi verbs, the first problem would be knowing exactly which algorithms would be needed for what type of lithium battery.

With lead acid batteries, you only need two different CHARGING algorithms, one for wet cell type cranking batteries and one for AGMs, but the AGM type CHARGING algorithms work fine with wet cell batteries.

Actual operating is the same with either type of lead acid battery.

There are some many different factors with lithium batteries that unless, like in the case of the Porsche setup, where the lithium battery is a specific type designed for that vehicle, you may need to buy a specific type of lithium battery that is catered for by who ever sets the CHARGE and OPERATING algorithms for a given type of lithium battery.

I have already stated some of the potential problems and this is for a lithium battery that we do not have specific specifications for, such as the battery’s Shut-Down voltage, and what happens to the alternator if the lithium cranking battery’s BMS, forces it to shut down.

When an alternator is allowed to operate with no battery connected, it can create very high voltage spikes that will quickly damage a vehicle’s electronics.

So do we have to program the VEHICLE’S BMS to turn the alternator off if the lithium battery’s BMS shuts down.

This type of situation would literally turn the vehicle into nothing more than a coffin on wheels, with no motor, no power assisted steering, or brake booster, no lighting so the hazard lights are inoperative.

As posted earlier in this thread, there are just too many Unknowns where lithium cranking batteries are concerned.