The Offshore Voyaging Reference Site

Lithium Start Batteries

There are now battery vendors advertising drop-in lithium batteries rated for engine starting.

If ever there was a solution looking for a problem, this has gotta be it.

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Jesse Falsone

I wired my lithium bank (3x100ah Kilovault properly T-class fused) so that it could be used as an emergency start for my Westerbeke via a 1/2/off switch (i.e. no mixing chemistries). Cold starting current was measured at 281 amps and the engine starts very quickly. I know it’s not an ideal solution but I think better to have this capability than no backup starting capability at all. It’s also incentive to keep my lead acid AGM starter battery in good condition.

Jesse Falsone

I think it was a Fluke (belonged to a friend) and the current was actually less – 188 amps. I actually have a plot that the meter produced.

Stein Varjord

Hi John,
Lithium fanboy here, 🙂 chiming in just to support the conclusions.

While LFP cells separately are vastly superior to LA on current capacity, (cranking power), the necessary electronics will completely sabotage that on close to all drop-in batteries. Buying a lithium battery, even one made for this function, to use it only for starting an engine, is a poor choice for reliability and economy.

The only scenario I can see a lithium battery as the normal starting battery, is if it’s the house bank. The backup power should then be some other system, probably based on a robust LA battery.

The house bank is often close enough to the engine(s) to do the starting job well. However, to anyone who wants this: The engine room is a bad place for LA batteries and even worse for lithium.