MacGregorSailors.com

I don't think your supposed to charge lithium batteries from the ETEC alternator on the OB - well, unless the lithium battery is like a really really big BANK of batteries (like the way they do them in a Tesla car) or if it's like a really BIG battery - like in a Prius, or a Chevy VOLT car. The Prius has a special alternator set up so the battery does not get high voltage when full even though the engine is not supposed to start when the battery is full. The guy that TRIED to 'splain it to me (unsuccessfully) said that the batteries will be ruined fast if you overcharge them. I was too stupid to understand him but I can repeat some of the things he told me.

He said lithium batteries should not be charged from a voltage source that is over 14 volts - unless the batteries are pretty dead. They said that if the lithium battery is almost fully charged and you hook it up to your ETEC60 it will overcharge the battery because the ETEC alternator puts out over 14 volts at full throttle. So that means you need to disconnect your lithium battery from the OB when your underway or you might overcharge the battery.

Pretty sure the regular batteries can take a 14 volt charge for many hours on end but apparently you can't do that to a lithium battery.

Anyways, he said it's a bad idea, but I'm sure you guys know more about this than I do.

I did have a question for TOMFOOLERY - are we supposed to connect the neutral in our AC system to the negative equipment ground in the DC system?? I did not do that - are you saying we SHOULD, or we SHOULD NOT? I got confused on that one.

And what about the Equipment ground on the AC system? (Like the ground wire on the AC receptacles - aka - the little green screw and the green pigtails - the GREEN wire - should THOSE be grounded to the same DC equipment ground too??? I have green wires on all the AC stuff that grounds the receptacle boxes and junction boxes and stuff. I ALSO have green wires that are grounds for all the DC stuff. I don't think I have those two systems tied together right now - should I?

Probably. It's too complicated to make a blanket, absolute 'yes' statement, but if you have anything metallic under water that's connected to the DC system, or any DC appliances, then I can't think of anything that removes the requirement.

https://www.proboat.com/2011/10/demysti ... onnection/

https://www.westmarine.com/WestAdvisor/ ... Conditions

https://www.westmarine.com/WestAdvisor/ ... ng-Systems

Here's video of kids nearly drowned in a pool due to stray voltage (a ground fault in the pool system). They lived, but it could have been much worse. Same principle applies to ESD in marinas. (disclosure: I was the one who pushed for M. Holt, of who's Code Forum for pros I am a member, to make ESD more public in his awareness campaigns.)

https://www.mikeholt.com/newsletters.ph ... terID=1445

This is the tragic story that brought it home for me, some time ago. (Edit: That's not the original video, which had a detailed explanation with graphics of the second boat tapped into the first boat's electrical system, but it conveys enough to get someone's attention.)

https://www.youtube.com/watch?time_cont ... jtgQoJTQWw

Oh, and it's not just faulty boat electrical systems - improperly connected/protected boat lifts and other near- and in-water equipment can cause ESD in fresh water lakes and pools, too. Lots of examples out there.

And for the old-timers out there who've been boating for decades, my 85 YO FIL tells me that it was 'common practice' to remove any bonding conductors between the boat's DC negative pole and the equipment grounding conductor of the AC system, as it would cause accelerated electrolysis and galvanic corrosion due to leakage current from the other guy's boat, which likely had an improper AC wiring system too. But there are galvanic isolators, which prevent the AC shore power system equipment grounding conductor from being part of the circuit that's eating your lower unit or aluminium outdrive up.

http://www.boatus.com/seaworthy/galvanic/default.asp (about 2/3 down the page)

But this is getting off the OP's original topic.

Québec 1 wrote:My wife and I don’t buy batteries,sailing gear,anything that touches a sail or anchor together. I do that by myself. You must have an interesting wife if you discuss new tech battery gear.

Ha! Interesting. When I told my wife I was researching lithium batteries she wanted to know more and eventually she came to be the one to push towards that. I was apprehensive only because of the price. She's my best friend man. Plus, if we sink, I can give her half the blame.

BOAT wrote:I did have a question for TOMFOOLERY - are we supposed to connect the neutral in our AC system to the negative equipment ground in the DC system?? I did not do that - are you saying we SHOULD, or we SHOULD NOT? I got confused on that one.

And what about the Equipment ground on the AC system? (Like the ground wire on the AC receptacles - aka - the little green screw and the green pigtails - the GREEN wire - should THOSE be grounded to the same DC equipment ground too??? I have green wires on all the AC stuff that grounds the receptacle boxes and junction boxes and stuff. I ALSO have green wires that are grounds for all the DC stuff. I don't think I have those two systems tied together right now - should I?

This is interesting. I have to check, but I don't think I have the neutral AC bus connected to the negative DC bus either.

I know from experience that my marina's GFI will trip if the AC mechanical ground (green) bus is connected to the AC neutral bus anywhere in the boat. It worked fine prior to my marina installing a new electrical system last year, but its a no-no now. The AC mechanical ground and the AC neutral have to stay isolated all the way to at least the shore power connection at the dock. There is a GFI breaker there, and something else in the big main panel at mid dock. Something in the big panel was tripping until I removed the jumper connecting the neutral and mechanical ground busses. Ironically, It is common to connect them to the same bus when doing house wiring.

I'm also trying to think if anything on the DC side has mechanical grounds, and I'm drawing a blank. My memory might be going bad, but I think they are all two conductor wires with no mechanical ground runs. And if they are there, what would they connect to? Lets see... nav lights, anchor light, steaming light, cabin lights, freshwater pump, 12v cigarette lighter type outlets, none of those have a mechanical ground connection. Maybe the stereo and the instrumentation do... I'd have to look.

paul I wrote:Ironically, It is common to connect them to the same bus when doing house wiring.

Only in the service equipment, which is usually the main panel. The grounded conductor (NEC-speak for the "neutral") is only tied to the equipment grounding system, which includes the grounding electrode system (usually ground rods on older houses, plus incoming cold water pipe), and all the equipment grounding conductors (aka "the ground wires", or "safety ground wires"), in one place in the whole system, with that place being the service equipment. On manufactured homes, the service equipment is normally on a pole, and the panel inside the dwelling unit (NEC-speak for "house") is really a sub-panel, with four conductors into it, including separate neutral and ground conductors.

Your house only has three conductors from the transformer to the meter, but there, or inside the main panel, is where it splits for the whole rest of the system. Even outbuildings, which used to be allowed to be powered with a 3-wire feeder, now have to have a 4-wire feeder (since the 1998 cycle, I believe). Same is true of any subpanel within the structure, and electric clothes dryers and ranges/ovens that formerly could be wired with 3-wire branch circuits (with the frame bonded to the neutral) now have to be wired with a 4-wire circuit, with the metal frame connected to a separate grounding conductor. Existing installations excepted, of course.

The boat panel is technically a subpanel, but with only one ungrounded (NEC-speak for "hot") conductor instead of two like your house, plus a grounded conductor (neutral), plus the equipment grounding conductor. No bonding between the neutral and ground, which will trip a GFCI breaker because it causes current to flow on both the neutral and the ground, and that's because the voltage at that point is not at the (essentially) zero potential that Mother Earth is in the same vicinity.

Here u go
https://www.google.ca/search?q=marine+b ... yzCbR_Hu_M:

J

Sorry to butt in with probably a dumb question, but is the OP talking about a Lithium ion battery or a Lithium iron phosphate battery? There is a big difference especially when discussing volatility....

RGF wrote:Sorry to butt in with probably a dumb question, but is the OP talking about a Lithium ion battery or a Lithium iron phosphate battery? There is a big difference especially when discussing volatility....

We're using LiFePo4 (lithium iron phosphate). The safer of the
two chemistries. I don't have a death wish, lol.

First, I probably would not use lipo. I would go with Life. They are heavier and bigger but they are safer if there is an accident involving a battery puncture. Lipo has 'free' lithium which reacts to air and water in a way that would not go well on a boat. Life ties the lithium to iron so there is no free lithium.

Second, Read the charging instructions _very_carefully_ If the battery is set up as an 'automobile' replacement battery then you can charge it of the regular charging system, however, the lithium cells will eventually become un-balanced and reduce the capacity and life of the battery. There is usually a 'special' balanced charging connector that requires a specialized balancing charger to bring the cells back into balance. This does not have to be done on every charge. I do this on my motorcycle lithium battery once a year.

I have been keeping an eye on lithium batteries for years. I'm not ready to trade in my two 6 volt golf cart batteries for house just yet.

I installed a Galvanic Isolator 2016/2017 winter




pricey but as the boat is going to b in the water most of the yr & slipped I figured it was a good investment

J
PS the white power cord is off a power bar that sit,s behind the galley it,s not attached to the Isolator it is attached to the liner , so as not to confuse anyone !