10 "Banned" DIY Repairs That Will VOID Your Boat Insurance

[dlandersson]

10 "Banned" DIY Repairs That Will VOID Your Boat Insurance

[Russ]

Yep. Household wiring is no good on boats. Vibration is the key to failure.

I think I also read in Nigel Calder's book that pure solder joints are not recommended either as extreme heat could cause them to fail. I crimp everything and then solder it.

[Ixneigh]

That was interesting. Esp. the part about lithium phosphate batteries. Friend of mine just did the swap out they talked about.

Ix

[Be Free]

The two problems addressed in the video re: lithium batteries is alternator damage due to overheating and unexpected disconnection as well as the consequences of those problems.

The key to not melting down your alternator is to avoid connecting it to something it was never designed to charge. They key to avoiding an unexpected disconnection is to not have switches between the battery and the alternator. Avoiding both of those problems is trivial. I'll address keeping the lithium battery charged a little later.

Your outboard was designed to charge a lead acid battery. While there is a partial overlap in the charge profile, lead acid batteries are meant to be charged at a lower voltage and a lower amperage than lithium. The lead acid charge profile tapers off as the battery is charged; the lithium profile is virtually the same from start to finish. Lithium needs a higher voltage and really prefers an amperage that is close to a magnitude greater than your alternator can provide.

The alternator in your outboard was designed around the needs of the outboard and a lead acid battery. Using your outboard alternator to directly charge a lithium battery is not quite as bad as trying to put a square peg in a round hole. It's more like putting an octagonal peg in a round hole. You can make it work but it's not right.

The fix is not difficult and it is not particularly expensive.

If your keep a lead acid battery wired directly to the outboard you can't blow your diodes due to an unexpected disconnect whether from a BMS cutting the connection or an inadvertent switch to "off" with a battery switch.

Most of the outboards that our boats carry do not have a lot of excess charging capacity compared to the "appetite" of a lithium house bank. That said, I still hate to waste electrons on those (hopefully) rare occasions when I have to run my outboard for hours rather than minutes over the course of a day.

The next problem is how to keep all of those spare electrons from going to waste. The answer is a battery-to-battery charger connected to your start battery that takes the excess capacity of your alternator (after the start battery has been recharged) and feeds it into the lithium house bank in the same way a dedicated shore-powered lithium battery charger would. The output of the B2B charger is identical to the output of an AC powered lithium battery charge albeit at a significantly lower amperage.

Your alternator is happy. Your start battery is happy. Your house bank is happy. Your insurance company is happy. Your checking account is slightly peeved (but when is it not?)