Lithium battery ??

Nick
I have only used small prismatic cells but prefer those over cylindrical. I have both types and two dedicated chargers which vastly slow the charge after initial bulk delivery. While one type has many cells banked in parallel circuits the prismatic is more like each cell of a conventional battery, in my view, others may differ. Although they will accept high charge rates I am not so sure they like it, as many believe. Acceptable rates ,yes. Bill Shortens 8 minutes would ensure a short life, ie, Shorten'ed.
There are many alt powered switch mode chargers to suit. Most also accept solar which will be less charge rate anyway. Lithium seems to be the way to go but check the cell balancing/ management and discharge draw ability is suited to your application with whatever you choose.
Seeing they hold their voltage until very near the end, a monitor to read ins and outs is a good thing to include.

Hi Nick,

It is my understanding that you need a DC/DC Charger with a high amperage output to take full advantage of a LiFePo4 battery’s ability to rapidly recharge. Something like a Redarc 1240. Trying to charge one battery from another battery is really not ideal, as once the voltage of the two batteries equalises, you have two not fully charged batteries.

The set up in the back of my wagon is that I have a 100 AmpHr LiFePo4 battery being charged from the vehicle alternator via a Redarc 1240 DC/DC charger. I have a seperate solar input into the Redarc via an Anderson plug on the back of the car.

I would humbly suggest that you seek the advice of a competent Auto Elec.

Macca.

I only know what I've read and take no notice of what a battery seller says to promote their batteries.
Just dug this up if you want a summary: https://blog.epectec.com/lithium-batteries-cylindrical-versus-prismatic

For RV use I don't think it matters whether they are cylindrical or prismatic. The performance and longevity is similar. Cylindrical can be cheaper but not as easy to assemble as prismatic.

I have cylindrical - 100Ah and 125Ah Sunyee batteries (I trust the brand because they have been around for 16 years) and because they were cheap. I have 4 batteries spread between my Troopy, caravan and tvan.
I prefer good brand chargers that you can put custom charge settings into - so use Enerdrive DC2DC and a Victron IP22 240V chargers.

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Hi Nick,

For the user there is little difference between cylindrical and prismatic cells. The choice is made by the manufacturer based on his preference of manufacturing. In essence, a cylindrical cell is a prismatic one rolled up! Because a pack of cylindrical cells leaves spaces between, they occupy a larger final case volume than would equivalent prismatic construction.... but not much. Some may falsely argue that this assists heat dissipation but heat in the spaces has no ventilation so....?

Lithium batteries do not "like a fast charge" but they will 'accept' higher charge rates than lead-acid batteries. Mind you, higher charge rates mean higher cell temperatures which contribute to cell degradation and shorter life, so it is wise to use a charging system that limits the charge current to protect both the battery and vehicle alternator. To that end, a dc-dc charger with both alternator and solar input ability is appropriate. Some people have arranged for their lithium battery to be charged directly from the alternator or from a dc-dc charger designed for lead-acid batteries, but that is not my way of treating an expensive lithium battery.

Lithium batteries are expensive so there is the temptation to buy a cheaper brand but that can be a greater cost in the long term due to inferior build quality. My philosophy is to protect my investment by purchasing a reputable brand even if at a greater initial cost. Then use a quality dc-dc charger and battery monitor system.

Hi Nick,

I have been trialing two 100Ah built up batteries for a few years and for the past 2 years or so an 80Ah drop in my car.

The 100Ah are mounted in a camper and charged by an Enerdrive DCDC which does has a Lithium profile, a MPPT with a Lithium profile and the existing Projecta AC charger. However I do not use the Lithium profiles in the chargers that have them, I use user parameters that are basically the same as the Gel profile on the Projecta charger which does not have a Lithium profile. Note the Lithium settings on the other two chargers are more or less the same as their Gel profiles anyway. If AC is available I generally just charge the batteries using the power supply settings as it brings them very close to fully charged. If cycling daily then I use settings similar to the GEL settings to bring them up to fully charged a bit quicker.

The 80Ah in the car is directly charged off the alternator via a VSR, via 6B&S cable. With a modern alternator your not likely to get more than 60A flowing into the battery, less if it is an unboosted low output voltage type.

With my setup power to the van is taken off the VSR, power to the aux in the car is taken off the same point, I have done this to control the max current draw from the alternator. When the van batteries are low the DCDC in the van draws around 50A, this pulls the charge voltage to the aux in the car down so it will only charge at around 10A - 15A until the batteries in the van are charged then it increases.

After several years of use the van batteries still test over their specified Ah capacities. The car aux still tests over its specified capacity, actually it is exactly the same as the Ah capacity shown on the test sheet when I purchased it. It is also mounted in the engine bay and so far it has not been affected by the heat.

To date I have found the Lithiums much easier to maintain than lead acids, they will happily accept whatever I throw at them and aren't fussed about not being fully charged, I used to spend considerable time managing the old lead acids, chasing sun etc but with the lithiums I just glance at their SOC in the morning to check the chargers are keeping up with the demand and that's it.

Once a year I fully charge them and let the cell balancers do their thing.

Nick, as suggested above, there's not a great difference between prismatic or cylindrical cells in performance or reliability. There's a HUGE amount of good and easily found info on the web regarding these two cells types, and proper charging of them. Here's another comparing cell types you mention: https://www.lithiumion-batteries.com/cylindrical-vs-prismatic-cells.php

In general, the recommended charging rate for a 12V LFP is 0.3C, ie 30% of battery capacity.

High charge rates = more heat, and heat will reduce battery life over time. Solar charging is fine, if obviously a little slow.

Some batteries will have their recommended and maximum charge (and discharge) rates listed. [Not that you asked but higher discharge rates are often a decent indicator of BMS, cell and build quality. Always ask what the cell grade is - A grade being the by far the best. ]

If charging from 240V ideally you should use a charger with an LFP profile. LFP's charge differently from LA batteries (higher voltage, no float etc). As has already been stated, the critical thing is that once charged your battery should not be put onto a float stage.

Again there is plenty of useful and easily understood info around regarding charging, eg https://offroadliving.com.au/blogs/12-volt/can-i-charge-my-lithium-battery-with-a-lead-acid-charger