Honda Alternator Fuse Blown

J

John&Robin

New member
Hi Brats,
During the engine flush after a couple of days out I noticed the starboard engine wasn't putting out charging voltage. I checked the internal engine fuses and found the alternator fuse was blown. Swapped it for the spare and it's working again. Does anyone have suggestions on what to look for that might have caused this? We've got twin Honda 40's wired to a 1-2-Both-Off battery switch and two 12V batteries. Any suggestions appreciated!

Thanks,
John
 
There was a short somewhere that blew the fuse - maybe. Nobody will be able to tell you where with much certainty as that is complicated and will depend on boat electronics configuration. But, I doubt it is your battery switch that caused it. I can't think of any known smoking gun trouble areas on the honda 40/50 motors that had electrical problems. However, running 2 outboards on 2 batteries connected together on "both" is never a good idea. In fact, I'd never do it because the regulators can and will fail - hope you're not doing that. So, this was a really long way of saying I have no idea.....lol.....
 
Thanks for the suggestion, and yikes, the advice! I always run on BOTH, thinking I'm charging both and that would be a good thing...

Two batteries, one switch, two engines, how should they be set up (if I can lean on your good will and expertise!)?

John
 
Each engine will charge each battery just fine on it's own if they are wired individually. There is not a need to go to "both" unless there is some emergency and one engine will not start. And, if you only have 2 batteries, putting the switch to "both" can cause each regulator to go into a hyper mode of sorts with them switching like crazy and then they fry themselves - eventually. Lots of folks have had this happen. That may or may not have caused your fuse to blow. It's really hard to tell. Do you have a 3rd battery too?
 
That's what the people at the shop said who are supposed to know when I added my 3rd battery, because I wanted to tie both hondas together on a battery and use the other spot for the house so I'd only have 2 to deal with. The parts/tech rep said don't do that, gave the reason, and now I have 2 lead acid starting batteries and 1 lifepo4 house battery. I strongly suspect that many people have gotten away with it.
 
Thanks TR,
We have two deep cycle batteries, lead acid, so I've randomly designated one as house, other for starting when we cruise. I'm on the hunt for a wiring diagram for twins with two batteries as I'm not excited about installing a third but don't want to burn up regulators! Hope you're thawed out up there and getting time on the water.

John
 
Thank you for this info TR Bauer,

When I got the boat it had three batteries which are new and in good condition. All were tied together into one huge rats nest and so I dedicated two to the house bank and one to the engines and didn't have any troubles, so far... I don't know if I can make room for another start battery and it seems a little silly to have 4 batteries on a CD22.

I only charge my batteries with the engines (or an external charger while in the carport), and I was wary of mixing battery types. Have you had any issues in this regard, or do you charge the lifepo4 with a charger and/or solar?

Sorry to hijack the thread like this but this is good info,
Thanks
 
I use a BEP switch cluster with 2 batteries, one for each engine, and they each have their own on/off switch. I have the off-1-2-both and can decide which on I will be using for my house battery. each battery have its own meter inside for monitoring. I try to upload the diagram but it didn’t work.
 
I would also like to know how you are charging the LiFePO4 battery. What have you done to prevent it from ever being attached directly to one of the FLA batteries?
 
John&Robin":2dmwfyfg said:
C-Wolfe,
Thanks for the info, it looks like the solution. Does the 715-S also combine the two batteries, or do you have a separate 1-2-both switch?
Click to expand...

The 715-S has 3 different switch. 2 battery/engine switch (port and starboard ) and a main off-1-2-both (combine). If one battery is dead you can combine to start .
 
Probably the wrong way by somebody. I was instructed that as long as you don't ever run on "all" they are mechanically disconnected from each other. And the volt meter says it is true. So basically, when I set my perko over to the lifepo4 battery, it is just powering the house. Then, if I switch over the starting battery, it isn't tied to lifepo4, except for the moment in time you pass through "all" on the switch, which is about 1/4 a second and supposed to be safe. The bad part is, the only way to charge the lifepo4 with the outboard is on both, which can never happen since you can't run these batteries in parallel, so that kind of sucks. But, I don't do much more than weekends, don't have much power demand, and the lifepo4 never gets that low (so the math says) that I have run into trouble with that. It gets charged by a small charger lifepo4 charger at camp, the dock, or at home. It's not ideal by any means. Is there a way to make it ideal?
 
Would it even actually matter if I ran on "both"? I have read a ton of information over the winter on running AGMs with lifepo4 in parallel and they had favorable results. All had BMS like mine, which is a failsafe, and many folks found that the lifepo4 batteries charged first, and then the AGM charged last. They also found the lifepo4 discharged first as they were using it and then finally the AGM started to kick in once the voltage started to get low enough. These were off the grid living folks doing it repeatedly and they were mixing them for economics. Obviously, they are different batteries and behave differently and running them in parallel is not ideal. However, I am starting to wonder with lower powered charging systems under 14.5 volts and less than 10 amps if any of it even matters enough to reach out to relion and pose the question.
 
If anyone is interested still:

Timothy,

It is ok to run that combiner from time to time, the issues with combining the batteries arise when you turn off the motor. Regarding a fire, our batteries built in BMS provides protection features that would prevent that situation from occurring. What can happen when you turn off the engine is that the LiFePO4 batteries will sit at a higher voltage than your lead acid which would cause some energy to flow to the starting battery from the lithium units (again just turn the switch off to avoid this). That being said, you will not see great performance on alternator charging your starting battery by combining the units as lithium’s higher voltage will cause pushback on the system which will limit the charge rate and could leave the starting battery under charged (not dramatically but likely a bit) this would not be the case if you were utilizing an AGM battery for starting as opposed to a FLA.
 
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