Scuttlebutt have an interesting two-part story about upgrading the electrical system in a J/105. Worth a read, even though this is a racing boat.
To me the takeaways are:
- How terrible the electrical systems are in production boats, to the point of useless, at least for offshore use. They were running the engine 8 hours a day to keep up with demand!
- Replacing the stock alternator driven by a single belt is job #1 in any electrical system rebuild.
- Replacing the standard internal regulator that ramps down charge current way before the batteries (lead or lithium) are even close to charged is part of job #1.
- Details like properly crimping battery cables are vital.
- In most cases the best bet with a production boat electrical system is to tear the whole battery and charging system out and start again.
- Read the manuals, several times.
- Most of what you see out there on YouTube about lithium is bogus.
- A dedicated and isolated start battery is the only way to go. Off/one/two/both switches are just silly.
- Seems like Electromaax has some good kit. I spent a little time on their web site and was impressed.
All useful, but the biggest takeaways are:
- Just getting the alternator and regulator right reduced charging from eight hours a day to one.
- They would have got the same benefit with an appropriately sized lead-acid bank, but it would have been bigger and heavier, so in this case lithium was a clear winner, but only for that reason.
- Without the alternator and regulator upgrades, upgrading to lithium would have been a total waste of time and money—getting charging right is the key to success.
Much more on electrical system upgrades: