Hi Bill,
The "C" rating of a battery is it's Ah capacity. So for a 100Ah battery has a C rating of 100. A 2200mAh AA cell has a C rating of 2200mA, etc. etc. Most battery manufacturers recommend charge rates of 0.1 to 0.3C for flooded cells and some AGM will accept 1C.
Typical prismatic cells take a charge or dicharge of about 3C, though their lifecycle estimates are usually based on charge/discharge rate of 0.5C. So your 55kWh bank would be around 570Ah @ 96V and would take a 285A standard charge or a 1710A @ 96V fast charge. For the standard charge, you'll need a generator that is rated for 28kW to hit that number.
When condsidering differnt brands of prismatic LiFePO4 cells, the EV will sometimes choose CALB cells because they seem to support a discharge rate of 4C compared to the Thundersky cells at 3C. The CALB cells are a little more expensive. Both brands will support burst rates of up 20C. Let's plug that into your proposed 570Ah pack. 3C=1710A, 4C=2280A and 20C=11,400A. Obviously, these are completely unrealistic rates, so you won't even come close.
Where this does become more important is in an EV with a 100Ah 156V (15.6kWh) battery pack. The CALBs will handle a 400A sustained load compared to the Thundersky 300A. Both battery brands will support 2000A for very brief bursts. My next EV (temporarily on hold) will have a 160A @ 156V battery so even with Thunderskys, I will be able to run 480A sustained (60mph shound be around 90A) and the Soliton 1 controller will limit the current to 1000A, barely more than 2C.
So for electric boats like we usually discuss here, the high C charge/discharge capacity of lithium cells doesn't really come into play. I find that the small volume, light weight, and very low Peukert Effect are more relevant to our boats.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "Galstaf" <richard@...> wrote:
>
> What is the charge capacity of regular prismatic cell batteries?
>
> I am still interested in the ability to dumping a *large* amount of power into the batteries in a short amount of time with a high rated generator, or hooking up to 2 or 3 shore power drops simultaneously.
>
> A higher capacity genset would also be useful for forcing the boat to hull speed in the case of an emergency.
>
> * Is the high charging rate option for emergencies practical/possible/a good idea?
> * What is the "C" rating for typical prismatic cells?
>
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