Dedicated starter battery or lithium jump starter?

[Reefmagnet]

My boat has two battery banks, but no dedicated start battery. The engine is 30 something horsepower. I was planning on installing a small dedicated starting battery, even though it's always used the house bank for starting but then I got to thinking...

Would one of those compact lithium emergency starters substitute? I see a lot of advantages over a conventional battery. Anyone with an opinion?

[mikedefieslife]

I see a starter battery as a waste of time, space, and weight. Any decent house bank will have enough cca to start a 30hp engine. If the **** hits the fan then as you say a small powerbank could be hooked up direct to the starter to get the engine running.

[john61ct]

As long as you have enough redundancy for **your** comfort level.

I prefer the second bank to be Reserve, only used to run the Essentials (engine / safety / navigation) if the larger Main bank fails. Regularly tested.

Cranking engines is easily switched to either bank.

Note the little jumpstarter is then third-level backup, belt & suspenders. It must be refreshed charged and periodically replace. I would also test that regularly.

Another idea, a 12V string subset of a larger bank that is usually shallow-cycled, has LVD isolate it if drawn deep so it remains at SoC well higher than needed to crank.

Keep it in the main bank for Peukert benefit for normal operations, but also keep it from being drawn too low when House loads are more demanding, or weather reduces solar input.

[RobD527]

I have no dedicated start battery, I do have solar, a portable jump starter and a portable generator so I'm not the least bit worried about getting the engine started

I don't live on the boat so the portable jump starter is handy to have in my vehicle if I need it or to help someone else that needs a jump

[a64pilot]

I have two banks, ganged into one with the combiner switch.
I can’t understand, why people with only one engine think that they need all these redundant engine start sources.
Do they also have three fuel tanks?

[Stu Jackson]

Downside I see of a separate pack is just when you need it you have to jump around doing wiring, or unwiring.


All I do is turn my switch to the reserve bank.


Your boat, your choice.

[Reefmagnet]

Thanks for the responses, guys.


Yep, with multiple house banks there shouldn't be any need to require a dedicated starter, but when traveling to remote locations it's reassuring to have a backup. Deploying a dedicated starter battery is probably a little bit of overkill though in this case, and I was concerned about mixing AGM (house) and FLA (starter) chemistries.



And that's why I think the idea of the lithium jump starter has some merit. It provides an emergency power source and they generally have USB and 12 volt outlets (and even lights) included which can make them handy for plenty of other things - for example powering a fish finder on the dinghy, charging phones when on shore and even last ditch emergency use. I can't see any difficulty in creating a circuit that allows the unit to be quickly connected and disconnected for engine starting or portable use.



Having said that, some of these things seem to have pretty woeful connectors and jumper wires which would concern me. I'm also wondering what their track record is like when it comes to spontaneously bursting into flames if they short out or otherwise fail?

[john61ct]

If they are used for other things you need more than one, keep one always fully charged or Murphy will strike.

It is consumer grade kit, so if critical replace on a schedule, IMO 2-3 years max. Those are the ones to charge phones etc, give to the kiddies.

[anchorbend]

I have had one of those small batteries for two years. I have used it once to start a 400 cubic in. truck engine with no issues. They hold the charge for quite some time and recharge quickly. They are also good for charging phones, tablets etc.. A boat battery may not have enough juice to start your engine but combined with a small battery, there should be enough to turn it over.

[john61ct]

They make bigger ones for big diesels, fit in cargo pants pocket not shirt pocket.