Hi to all the LFP lovers in here!
So I have been looking into this, but would like to get opinions and gain further knowledge about what may be viable for my application.
I would like to install a LFP battery into my hovercraft, if possible. Currently the craft has a single 65Ah FLA. The weight saving of LFP would be an obvious, and welcome benefit. Of advantage too, would be the ability to take the battery to a lower DoD compared to the FLA, for when the engine is not running but power is being consumed for accessories (VHF / music!) etc. I would like to avoid the extra weight / complexity of an additional starter battery.
1) Cranking current
The overall power drawn to start the engine I have consistently measured at no more than 202 amps. I understand it is inadvisable to regularly draw very large currents from lfp cells, which can degrade them over time, also assuming the BMS will allow it. However I see batteries of say 100Ah available now which are specified and able to supply a continuous discharge of 200 amps, with much higher discharge currents for a limited time. I see for example, the Victron LFP- Smart 12,8/100 has a maximum continuous discharge current of 200 amps. In my application, 202 amps would mostly (hopefully) be a matter of a couple of seconds. I would likely carry a lithium jump starter for backup.
2) Alternator suitability
The current alternator is a Bosch 85A unit with internal regulator. I am happy to replace this with a more suitable alternative + associated regulator / controller.
3) Voltage spike / load dump
I’ve read much about this, and the varying solutions (Sterling APD / TVS diodes). Main concerns appear to be from sailboat owners, where ancillary current draw is low? In my application, with the engine running, the absolute minimum current draw is 12 amps (fuel pump, ignition, ECM, instruments). So if the BMS decides enough is enough, would the resulting jump from whatever the battery was consuming down to 12A still cause an associated spike of concern?
The battery in my application would be mounted inside the cabin, negating excessive heat issues associated with an engine compartment installation. I also have no plans (or desire) to run the craft in sub-zero temperatures! ❄️
Any thoughts and other considerations most welcome!