jump starter or spare starter battery for CD 31

[jen1722terry]

We're thinking of replacing our starter battery, which we have yet to use in 9 seasons of sailing, with a compact jump stater, basically a small lithium battery with mini jumper cables.

Any recommendations? Ideas?

Cheers

Jenn and Terry

[Frenchy]

I'd keep the starter battery. If you're worried about it you could have it load tested. That battery can
start your engine, substitute for a house battery in a pinch and can be charged. I don't know if a jump pack can
be charged easily from the alternator. - Jean

[mgphl52]

You could use an inverter to power the charger for the lithium battery.

[gonesail]

consider keeping your starter battery and carry one of the portable jump start batteries for emergencies.

[Kailua Kid]

Congratulations on sailing nine seasons without needing to start your engine! That is remarkable. I agree with the comments above as regards not removing the starting battery, for the same reasons stated. I would only add that even a small diesel requires a pretty hefty amount of cranking power to start, especially after sitting for a while unused because of the very high compression relative to a gasoline engine. That amount of cranking power seems like a lot to ask of a portable jump-start type unit, even a very robust one (unless designed specifically for starting Diesel engines). Please let us know what you decide to do and how it works out for you.

[fmueller]

I’ve done exactly that - I bought a GB 40.

https://no.co/products/power/boost

Two seasons ago I decided to simplify my two battery A/B house setup which was overly complex) into one bank A and get the lithium pack thereby doubling the house bank capacity and simplifying (eliminating) the need to think about the Perko bank switch which just sits in the “Both” position now. So I just dropped the “B” hot and parallel wired both AGMs to the “A” hot. “Both” connects the alternator to the A bank now ... the battery charger is hardwired to the A circuit.

As a test I dropped the remaining hot and started my motor 5 times with the pack. Good enough for me. It does so without apparent strain. I charge it from the cigarette lighter convenience plug I have in my boat while I’m motoring or on the slip hooked up to shore power. The pack holds charge practically indefinitely so this is almost just a once a season task if you don’t use the pack for another purpose but it also makes a great work light.

In time when the AGMs are old I’ll replace with lithium I think, a more complicated and expensive undertaking ...but thereby increasing bank capacity again as lithium’s can be deeply discharged without harm ...

[wikakaru]

I have a lithium starter battery that I keep in the back of my car for emergencies. It cost about $80. The manufacturer says it will jump start up to 7L gasoline or 5.5L diesel engines. I stopped to help a guy with a big diesel pickup (like a Ford F350 or similar) and can confirm that it cranked his truck right up. However, it also nearly drained the battery. So here's the problem: if you run down your house bank for some reason and also have an engine that is reluctant to start for some reason, you will be in trouble.

The original poster doesn't talk about the many details that would affect whether this is a good decision for him, like whether he primarily day-sails or goes on long cruises; where his cruising grounds are and how far they are from help like SeaTow or TowBoat/US; how big his house bank is; whether he has alternative charging sources like solar and wind, and if so, how much charging capacity they provide; whether he has big-draw items like refrigeration that are likely to suck down the house battery bank; how well-maintained and reliable his diesel is; how self-sufficient he would like to be.

I can tell you that one of these banks is probably not up to the task of, for example, turning the engine over long enough to purge air from the fuel system when a leak has occurred.

For someone who mostly daysails in areas easily accessible to marine towing services this would be a simple, inexpensive, light-weight backup to the main house bank that could save you calling for a jump. For someone going on an extended cruise far off the beaten track, a nice big separate starter battery is what you want. Or maybe both a starter battery and a lithium jump starter. Figure out what you are going to be doing with your boat, what you are comfortable with, and go for the solution that works best with your situation.

Smooth sailing,

Jim