hiriskpaul wrote:odysseus2000 wrote:What confuses me are the statement that lithium ion batteries can not provide enough starting amps. At my local garage I watched a mechanic start a diesel with a flat battery using what appeared to be a small lithium ion battery pack. There are several similar sized devices on eBay, all saying they can produce around 400 amps to start a car & are lithium ion battery packs.
Are these devices not as described or is there some other “magic” that allows these starting feats to happen? Or are marine diesel in need of many more than 400 amps to start?
Regards,
Lithium can produce very high current but the typical, off the shelf leisure batteries have BMSs to limit the maximum discharge current. Normally the maximum discharge rate corresponds to the battery capacity in Ah, so a 100Ah battery would be limited to 100A. Any more than that and the BMS disconnects until the load is removed. Those little LiFePO4 jump starters are specifically designed to deliver much higher currents, but for short periods.
Thank you!
So in principle with appropriate wiring & two batteries with appropriate BMS one could replace both the starter battery & the bulk storage battery with LiFePo. To have just one battery like as in a car would need a BMS with no or a very high current limit for discharge & a charging management that would both ensure correct charging & heating during cold weather. The latter probably troubles the concept as several days in the cold would exhaust the battery due to its heating mandate else one would have to schedule a pre-heat before starting. The use of a mains heater as is common in Canada for oil sumps would also make this feasible, but few in the uk would like the inconvenience.
The blessing of having a BEV is that with the large battery & an HVAC (heating, ventilation & air conditioning) one can more quickly warm the battery pack & one also isn’t troubled by needing high cranking amps to start.
Regards,