2020 Alternator Issues

[gedakbx]

We have put 75 hrs on our new to us 2019 since may running on both batteries with no issues. The alternator should have no issues charging both batteries at once.

[Hayden]

That's the bit I don't get, if I've been running dual mode since the start, why would there be such a discrepancy between the two batteries?

[gedakbx]

That's the bit I don't get, if I've been running dual mode since the start, why would there be such a discrepancy between the two batteries?

Sometimes one just get week and will drag the other one down. How old are they

[gedakbx]

Never mind I see your boat is a 2021. I would check for loose connections at the alternator itself. I had charging issues on my last boat once and it was a loose power wire on the alternator

[Hayden]

I checked the connections on alternator. All looked solid. I made a quick video showing us testing the battery voltage (on battery terminals) and alternator voltage (on alternator terminals) under 3000 rpm load.

Is there anything else I can do to prove/disprove that this is an alternator failure?

https://photos.app.goo.gl/gctPey6cZtCL1xoe9

[boating406]

I checked the connections on alternator. All looked solid. I made a quick video showing us testing the battery voltage (on battery terminals) and alternator voltage (on alternator terminals) under 3000 rpm load.

Is there anything else I can do to prove/disprove that this is an alternator failure?

https://photos.app.goo.gl/gctPey6cZtCL1xoe9

Voltage is normally 14-14.4 on my cars I work on. 2021 mojo showed 14 on the dash with 1&2 batteries on.


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[Hayden]

Voltage is normally 14-14.4 on my cars I work on. 2021 mojo showed 14 on the dash with 1&2 batteries on.


Sent from my iPhone using Tapatalk

Is that under load (ie. 3000 rpm) or idle or engine off?

[2in2out]

Voltage should be between 13.7-14.4 vDC when charging from alternator, and that charge is “bulk” charge.

Here-in lies the problem of using one battery during float time. Lead acid and AGM batteries once depleted past 50% capacity (critical depth of charge) will drop 20-30% from total capacity. So, if you drop a new LA battery below 50%, the new capacity is going to be 80% or less. This won’t affect CCA until you reach 50% of original capacity as that is related to charge cycles, depth of charge, and charge rate, but dissipation rate will decrease. AGM batteries can handle more cycles and decay is on the lower end of scale.

So now you have a battery that only has 80% capacity, and you drop it below 40-50% of its original capacity, and now you have a battery that has only 40% capacity. This cycle continues and it depletes CCA, and if starting in parallel, the discharge rate in attempt to equalize both batteries and crank the engine can pull the second battery below 50% under high dissipation load which accelerates second battery decay.

LA and AGM batteries are best charged slowly with absorptive charging, as rapid charging and bulk charging can overheat the cells slowing electrolysis. Multiple rapid charges at depth weaken the transfer of electrons between the solution and electrode plates and mesh because heat created during the reaction causes solute to gas, being unavailable to receive electrons.

The process of relying on manual methods to balance battery drain are antiquated and would easily be solved with adaptive shunts and load managers that keep dissipation at above 60% capacity.

The dual battery switch is a tradition embedded in any leisure boater, but is a relic of a time when tech couldn’t adapt. If you look in any emergency vehicle built after 2006 that utilizes multiple battery banks and has extreme electrical loads, load managers will shut down systems in order of least needed to highest priority and maintain a starting voltage of >12.7vDC. The battery banks are paralleled to maintain constant states of dissipation and charge, so the batteries fall in the same replacement cycle and don’t have to take care of each other.

Until boats are fitted with load managers to reduce parasitic and non-charge state drain, and because we are human and fallible, floating on one battery versus both, and running on both batteries offers the least probability of an incapacitating event.

We ran our boat on both batteries, and floated on one, being mindful to switch to Bat1 on odd days, and Bat2 on even days. But even this system has a failure point. Maybe weather and work have only allowed us to boat on odd days. Bat1 is going to get battered and it’s life cycle is only going to shorten.

I argue that modern leisure boats need solar battery chargers to maintain battery systems and extend battery life. A 30amp panel and 40amp PCM charge controller would cost less than $200 and could be incorporated into the unusable dash space. This would provide enough absorptive charge to reduce most parasitic and entertainment voltage uses prolonging the dissipation time, keeping the dual battery switch as another safety-system factor.


Currently boatless

[boating406]

Is that under load (ie. 3000 rpm) or idle or engine off?

Idle or higher rpm. If you have a massive stereo and running all 6 pumps you could see the voltage drop.

13.7 - 14.4 like the above poster mentioned.


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[996scott]

I don't have much to add because when it comes to electrical stuff i am an idiot. Is it possible that you just have a battery that is going bad? I've had a battery crap out in just a few years and others that have lasted 10 yrs in my car.

As far as using 1 battery or both when running the boat our dealer said to always use 1+2 so that you keep both charged up. I've seen at least one other video from another dealer doing a walk through on a new Moomba on youtube and they also said to use 1 + 2 as well.