The thing that charges our batteries on the engine

[Nous Defions]

I have read some where that: Each engine on the 240 has a rectifier regulator that limits maximum output voltage to 13 volts between 2000-3500 rpm's, with a stator coil output voltage of 8.3v cranking, 36.4v@2000rpm, and 64.7v@3500rpm.

Another site says there are 40 amp magnetos on each engine.

If it's correct that each engine has a 40 Amp charging system does that mean the total amps possible for a charge is 80 amps?

Any electrical guru's out there that can clarify volts vs. amps vs total?

 

[Julian]

@Mainah did you ever dig into this?

 

[Beachbummer]

I was interested in your question and found even more questions in terms of how relevant this information really is to reach a full charge, due to battery's limited absorption rates
Regardless of the answer, it appears much less relevant than I thought.

Check this out if you have some extra time.

How Fast Can an AGM Battery be Charged? - Marine How To

TEST EQUIPMENT USED IN THIS ARTICLE BUY MHT RECOMMENDED TEST EQUIPMENT - AMAZON Baseline Discharge 49.3% SOC PREFACE: This article looks at the *charging times & achieved state of charge of an AGM battery

marinehowto.com

 

[Nous Defions]

How can I use this information to work for me?

 

[Beachbummer]

Beware that it takes time vs current to refill from below 50%.

Figure 15-8 amp Max charge rate, diminishing the higher charge it has, and compare to expected run time.

 

[Nous Defions]

Let me try asking my question a different way. If there are two magnetos with a max charge ability 40 amps each, does that equal a possible 80 amps max? Asking for fusing requirement.

 

[Beachbummer]

Where is the fuse going? Should you not be concerned with the max draw from the starter while cranking for fusing requirements too? or are you fusing the voltage regulator only?

 

[Nous Defions]

The long story is I contacted Blue Sea Systems because this wiring looked different from the instructions provided. The Blue Sea rep sent this back with where he suggests fuses without provided what size. With 4 gauge wire and a charging system of what I believe could be 80 Amps, trying to figure what size fuse is appropriate.

 

[Beachbummer]

Your fuse should support all possible loads (except for starting, since the ACR is not supposed to be active when starting the boat) What's the rating on the ACR? That should be the switch size.

There is a Minimum charging AMP advertised as 23.3-25.3 in a similar engine to yours for the 2008 FX SHO waverunner. If you want to add a fuse, I would suggest a fuse with the rating of the ACR. (Likely 60 or 80 amps? check the ACR and any instructions it came with)

 

[Mainah]

@Mainah did you ever dig into this?

I have never found firm numbers on stator output or tested it myself. 40a each @13.1v seems awful high to me even at WOT. As to the question of fuse ...You should fuse for wire capacity in most cases. In some case you fuse for the weakest link/component in the circuit. I would fuse at or below rated capacity of the wire, fuse, or ACR (whichever is the least) on the load side(s).

AGMs have great absorption and discharge rates. Lifepo4 easily beats AGM but that is a different conversation given the complexities with Lifepo4. I did figure out that running my two g31 AGM as a single bank (combine on) for discharge really helps split the large load I put on them and I get less voltage drop when running three ballast pumps at the same time.

 

[Beachbummer]

Also, Note that in most cases the cables going to the master switch are not fused. I wonder why something like this, or a large breaker of similar rating is not standard.

Amazon.com: Bay Marine Supply – 30A-300A MRBF Terminal Fuse Block Kit (Fuse Included) – Single Stud 5/16" (M8) Compact High-Amp Marine Rated Battery Fuse – 58V DC Maximum IP66: Home Improvement

Buy Bay Marine Supply – 30A-300A MRBF Terminal Fuse Block Kit (Fuse Included) – Single Stud 5/16" (M8) Compact High-Amp Marine Rated Battery Fuse – 58V DC Maximum IP66: Fuses - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[Nous Defions]

Reading Blue Sea Wire & Fuse Size Chart, I should be using a 100-125A fuse if I read the chart right. Charging Amps:80, Wire Size:4.
What I don't want is to be tooling along and blowing fuses because I went too small nor tooling along and having a melt down because I went to big.
Do I trust the instructions and call it a day or am I over thinking this?

 

[Nous Defions]

This may help with not needing to carry extra fuses.

 

[biglar155]

Reading Blue Sea Wire & Fuse Size Chart, I should be using a 100-125A fuse if I read the chart right. Charging Amps:80, Wire Size:4.
What I don't want is to be tooling along and blowing fuses because I went too small nor tooling along and having a melt down because I went to big.
Do I trust the instructions and call it a day or am I over thinking this?

Use the chart. Fuses should be sized to protect the current carrying conductor. The load you expect to carry determines wire size and wire size determines fuse size.

 

[Nous Defions]

So now the big question goes back to 100 Amp or 125 Amp fuse? Why do they give a range? Now I have to also carry two $16 fuses just in case they blow.

 

[Beachbummer]

I think you answered your own question in terms of priority (and I agree with your logic) You are given a range and you prefer it not to blow. The larger fuse will be closer to accomplishing your goals...


And, Why let it blow? Get the breaker that can be reset, so you are not stranded by needing fuse spares.

 

[Nous Defions]

I think you answered your own question in terms of priority (and I agree with your logic) You are given a range and you prefer it not to blow. The larger fuse will be closer to accomplishing your goals...


And, Why let it blow? Get the breaker that can be reset, so you are not stranded by needing fuse spares.

Reading reviews on the circuit breaker (cheap) not willing to chance it. Thinking of being out in the middle of no where and thinking glad I saved $20. I'll spend the bucks and get the fuses!
Thanks for the back and forth, I appreciate it.

 

[Speedling]

This may help with not needing to carry extra fuses.

I started using these on my amps a few years ago. Work great! Know stuff is off without draining overnight too

 

[Nous Defions]

I started using these on my amps a few years ago. Work great! Know stuff is off without draining overnight too

Reading the reviews, some say cheap and after blowing a few times will not work anymore. Also blow very easy like not up to the rating. Also can't find one rated at 125A.

 

[biglar155]

So now the big question goes back to 100 Amp or 125 Amp fuse? Why do they give a range? Now I have to also carry two $16 fuses just in case they blow.

Just to be clear: That fuse you showed is called a Terminal Fuse and requires a special fuse-holder. You can't just drop that over a battery terminal. You have to have this:



Not sayin' you didn't know. Just making sure everyone knows. Amateur electricians burn a lot of things down every year. It's the reason the Electrical Codes exist.