Lithium batteries

I've had a look around the forum and there are a number of older threads that look like they might be useful but I guess those were conversations that ran their course at the time and, bearing in mind the notice which talks about accidental bumping, I thought it probably best to start a new thread.

So here goes.

I've heard a lot about lithium batteries - the advantages being especially how they will tolerate being stored part charged (SoC) and their ability to withstand much greater depth of discharge (DoD). I also heard that they can stand many more charge/discharge cycles; the disadvantages I've heard about include cost, instability and they won't take charge below 0°C.

This last one was the killer as far as I was concerned but then I heard of a new chemistry - lithium titanate (LTO) which is stable and takes charge down to -20°C and below. Unfortunately there doesn't seem to be very much info about the practicalities of using these cells so I'm hoping someone has knowledge they can share. Of course, I'd love to hear all the reasons why I shouldn't even consider using such a new technology but be warned, obstinacy runs in the family...

My plan is to build a 12 volt battery to replace my existing 460Ah bank of 4 SLA batteries that live in the engine hole and power a 3kVA inverter. Don't ask me why the boat builder went for 12V to power such a monster inverter - to run it at its rated power means supplying 300A which is a big ask for even proper leisure batteries and the ones I have are well past their prime. And SLAs take time to recharge - even if you've drawn 75A out you can't necessarily put that much back (and, indeed, I can't - the alternator is rated at 150A which means its theoretical maximum output would only be 37.5A per battery). But LTO cells will take charge at 10C which for a 40Ah cell is 400A.

The other problem I foresee is that LTO cells will take charge at 10C which means they'll try to suck as much charge as they can from the alternator even when it's not running at its rated speed which is likely to lead to overheating and ultimately destroy it. Frankly, this is my greatest concern. Should I buy a new alternator that's designed for charging lithium cells? Does anyone know where I can get one?

 

Lithium batteries are usually manufactured with electronics Management Systems to each individual cell because they are extremely sensitive to charge and discharge parameters. This might be a consideration if you will be building a system from Individual lithium cells.

I haven't used LTO batteries, but they will most likely require special Chargers with strict top limit voltages when charging. Someone may have to build you Custom Electronics to clean up the typically dirty voltage output from an alternator.

Running the alternator below rated speed shouldn't be a concern as the electronics can easily handle the lower current draw being pushed out. Running continuously over rated speed would be more of a concern because the increased power dissipation required would stress the electronics and wiring. Charging at 400 amps would require large cables for connections between alternator, batteries, and inverter.

 

I'd wary of Li batts on a boat, due to their tendency to burn/explode in spectacular fashion. Thats gonna be bigger issue on a boat than a car. IIRC any Li-batt aircrafts are gonna have the batts isolated and always ready for automatic ejection. I wouldn't want a Li-batt-boat unless it was made by Toyota, and even then I'd wait for couple years to let the early adopters sort it out.

 

Yeah, this requires further investigation. My original plan was 5S6P for 11.5V 240Ah. I'm now thinking 6S10P would be better (apart from doubling the cost) since the draw from each cell would be 30A rather than 50. There are commercially available BMSs out there but I haven't yet got as far as asking the manufacturers if they will do what I want.

The issue, as I understand it, is that the alternator will try, due to the extremely low internal resistance of the cells, to output as much as it can but it won't be effectively cooled meaning that it will overheat.
I wouldn't be charging at 400A with my existing alternator as it's only rated 150A. The existing cables have to handle 300A to run the inverter (I'll be checking they're up to the job).

I'll refer you to Lithium-titanate battery - Wikipedia https://en.wikipedia.org/wiki/Lithium-titanate_battery
Due to their high level of safety, lithium-titanate batteries are used in mobile medical devices.
and
Microvast, based in Houston, Texas, makes a lithium-titanate battery that it calls "LpTO". In 2011, the world's first ultrafast charge bus fleet was launched in Chongqing, China. An 80 kW LpTO battery system was installed in 37 twelve-meter electric buses, which can be fully charged within 10 minutes with a 400 kW charger.

Trying to remember: was it Airbus had to ground one of their new planes 'cause the lithium batteries caught fire?

 

Have you priced them yet?
Delivered?
With taxes, tariffs, and fees?
Don't forget the weight and cost of the fire enclosure and fire suppression system and alarms.
And don't get them wet, under any circumstances.

 

It was Boeings new high tech 787.

 

lol
Currently I'm more concerned with getting new cells then I'll decide which kidney to sell. The ones on AliExpress don't fill me with confidence.
You must be thinking of some other kind of lithium cells they use these in mobile medical devices

 

The low or high temperature characteristics of a Li Ion battery depends mostly on the electrolyte chemistry. We did several years of research, still ongoing, on electrolyte. The holy grail is to find one that works at high and low temperatures. If you want low temperature batteries, they are available, but not the most common. Therefore more expensive. Also, Li Ion are not strictly batteries, but closer to a battery/capacitor hybrid.

 

Forgive me if this is off topic, but have you looked at sealed nickel-cadmium or nickel metal hydride as a possibility? They I have just about all of the characteristics you have listed and should be a lot lower cost. But they would be heavier and occupy more space compared to lithium systems- if that would be an issue. And I believe they can be built to minimize some of the undesirable characteristics. For example eneloop nimh cells have a very low self-discharge rate, though there may be some trade-offs.

 

LiFePO4/LiFeMnPO4 Batteries have a big chunk of the marine sector. Lots of people using them, they are more stable than the more power dense chemistry found in phones and laptops. If you don't need the temperature range of LTO then they are much more economical.

Cheers,
Mark

 

It was! Thank you

That's useful. I don't really understand the distinction you're making between batteries and capacitors; so, if I may be permitted to take my own thread off topic (well, not really), what makes a battery a battery and why do you say Li -ion batteries are more like a hybrid?

I haven't looked at NiCd or NiMH. Maybe I should. Though larger and heavier than SLA would be a no no. But thanks for the tip.

Yes, I had glanced at LiFePO4 but I baulked due to the temperature range. However, I spotted a post An affordable way to fit Lithium Batteries? https://www.canalworld.net/forums/index.php?/topic/101348-an-affordable-way-to-fit-lithium-batteries/ on a canal boat forum which seems to offer a possible work-around involving retaining the SLAs and using a parallel LiFePO4 bank. I haven't yet read much of the thread but if I can keep the LiFePO4s in the cabin maybe they'd be ok.

 

Batteries release energy through a chemical reaction. Li Ion batteries have a chemical reaction to produce lithium ions. The ions are then moved to one electrode (charge it) in a manner similar to a capacitor.

 

Ok, that's fairly simple. How is that different from other cell types?

 

I've been researching battery and solar tech for a while but don't have experience yet, so don't take this as expert advice:

Large LiFePO4 prismatic battery cells are a good compromise. Safe chemistry, not too heavy, cheap. No messing around with tons of small cells. The weight, slight cost and performance improvments of lithium cells or Lwon't be worth it for lithium (INR, NCR) or these new Lithium Titanate (LTO) cells.
Not sure about temperature ranges. I *think* they are fine to keep at cold temperature as long as you don't charge / discharge them. This video shows how to assemble a solar setup with such cells and a temperature cutoff sensor at 5°. Maybe you could add a small electrical heater to keep them at temperature? Or maybe as long as the water doesn't freeze then keeping them in the bottom of the hull would keep them in ok range?

You can get as cheap as 280€ per kWh on alibaba or 430€ for "Winston" cells already imported on e.g. ev-power.eu. You can probably find better deals in the US.
Good cells can handle 3C continuous so for 400Ah that would be 1200 amps.
Weight is about 10kg per kWh so about 50kg for 4.8kW (12v x 400ah)
You'll need a charger and a BMS too.

400 ah cell: EV-Power | WB-LYP400AHA LiFeYPO4 (3.2V/400Ah) https://www.ev-power.eu/Winston-40Ah-200Ah/WB-LYP400AHA-LiFeYPO4-3-2V-400Ah.html?cur=1
BMS: EV-Power | BMS123 Smart - Complete Set (4 cells) with Bluetooth 4.0 https://www.ev-power.eu/Battery-Management/123-Smart-BMS-Complete-Set-4-cells-with-Bluetooth-4-0.html?cur=1
Chargers: EV-Power | Chargers LiFePO4 https://www.ev-power.eu/Chargers-6V-to-36V/?cur=1

 

The capacity of the batteries decreases with lower temperature. As I said before, the electrolyte is formulated for a specific temperature range. Referring only to the chemistry on the electrodes is not an indication of the battery performance. The elements in the electrodes also can be arranged in a variety of crystalline structures, pore size and grain type. All of them influence the performance and characteristics. At temperatures below the operating range of the electrolyte, the battery simply goes inert. High temperatures are a completely different issue. The batteries can burn or explode, which is really dangerous. That is why proper systems have power management.