Do I need an alternator

[newhaul]

New engine install volvo md2b .
1963 columbia defender . 400 watts solar 400 watts wind. Do I need to in st an alternator. The engine is a dynostarter unit the dynostarter produces 11amps to charge start battery.
I have 200ah lifepo4 ( soon to install. ) now if I don't install an alternator and associated extra pulley the engine will fit in the existing engine room enclosure. With the alternator (65amp) I would need to build a new door assembly to add 5 inches to the center of the access to accommodate it.
I also have a 1k generator onboard for the just in case moments.
My total power draw underway would be about 35 ah per day including refrigeration .

Do I really need an alternator and associated charge controller ( Lfp specific unit) ?

[sailorchic34]

If you have a honda generator then no you don't need an alternator. Solar will keep the batteries up, just fine. That is except when the clouds are heavy for a few days. Then you need a different source to keep the batteries happy.

I'm generally of the opinion that if you have solar, then having a big alternator and exterior controller (on a smaller low power boat) is not required.

[newhaul]

Originally Posted by sailorchic34

If you have a honda generator then no you don't need an alternator. Solar will keep the batteries up, just fine. That is except when the clouds are heavy for a few days. Then you need a different source to keep the batteries happy.

I'm generally of the opinion that if you have solar, then having a big alternator and exterior controller (on a smaller low power boat) is not required.

SC thanks for your reply
its not a Honda its actually a harbor freight cheapie but it runs good .

[S/V Illusion]

Originally Posted by newhaul

SC thanks for your reply
its not a Honda its actually a harbor freight cheapie but it runs good .

My experience with cheapie generators indicates you will need an alternator, if not now then soon.

[a64pilot]

Or a Honda

[newhaul]

Originally Posted by S/V Illusion

My experience with cheapie generators indicates you will need an alternator, if not now then soon.

that lil hf unit has lasted for about 5 years and this is second boat and at a boat buck I can replace it several times for the Hondas cost.
Now I will carry an internal regulated alternator , belt and the adapter pulley just in case but hope to never need to remove the doors to charge batteries. Would just rather not actually have it mounted all the time unless someone can give me a good reason otherwise.

[nickseeger]

Having extra charging sources is always good. I solved this problem by getting a Delco (marinized) 85 Amp alternator from a regular auto rebuild shop. Cost $ 135.00 or so. To marinise the alternator all it requires is a small shield to prevent sparks. If you have a diesel engine this is really not a concern, but good to do anyway. As for the alternator, it's all the same on land for autos etc or boats, the only need for marization is to prevent spark in regular fuel environments. The alternator will only engage and run if the batteries request it. So in a no wind area, and it's also cloudy..you'd still have your alternator to generate power....that's my solution.

[guyrj33]

I think the answer is dependent on the type of sailing you will be doing and also where you will be sailing.
200AH of Lithium means you can use about 80%? of capacity which should see you through a couple of days.
If you're sailing at night or using an autopilot frequently that could double your power budget.
I'd hate to see you in a position of approaching a harbor at night with low batteries and unable to use your autopilot for example.
Your 11amps or dyno will probably be enough to see you through a low battery situation.
Depends on the type of sailing you do.
Definitely install a battery monitor.

[noelex 77]

35 Ahrs a day is very low. 400w of solar and 400w of wind should be much more than you need to cover requirements without thinking about the generator even in unfavorable conditions.

Normally, the alternator is easy alternative supply of electricity so it makes sense. Most marine engines have an alternator fitted as standard. However, given the difficulties fitting an alternator in your case I would not bother.

[stormalong]

Here in Puget sound I think your 400 watts of wind will disappoint you.



You say nothing about your electrical demands. Do you have refrigeration? Are you day sailing or cruising? Is the boat in a marina with shore power nightly? All these questions need to be answered before deciding your question.

[hellosailor]

440W of solar panels will give you about 25 amps output for an equivalent of five hours each day, so about 125 amp-hours of "12" volt power. If you consume 35AH per day, your panels will keep up the batteries all by themselves. "If" and "If".

[waterman46]

Better check your stated amp-hour requirement per day. Seems unreasonably low if you are running any kind of refrigeration at all, plus normal other demands, even at anchor. While underway you will use more electrical power. Ask yourself, do you use radar, autopilot, chart plotter, VHF, depth sounder and other instruments underway, for longer than one day and a night before anchoring/docking? Can you get significant charging from solar while sailing or motoring? Will it be sunny every day you are on the boat? Is your generator easy to use and can it be used underway? Do you want to have to run it while at anchor instead of getting free charging from an alternator while motoring?

[newhaul]

Originally Posted by waterman46

Better check your stated amp-hour requirement per day. Seems unreasonably low if you are running any kind of refrigeration at all, plus normal other demands, even at anchor. While underway you will use more electrical power. Ask yourself, do you use radar, autopilot, chart plotter, VHF, depth sounder and other instruments underway, for longer than one day and a night before anchoring/docking? Can you get significant charging from solar while sailing or motoring? Will it be sunny every day you are on the boat? Is your generator easy to use and can it be used underway? Do you want to have to run it while at anchor instead of getting free charging from an alternator while motoring?

ah is actually estimated on the high side. And yes I have a counter for ah in and ah out.

Will be running custom build technautics holding plate system 1.5 cf freezer and 3.5 cf spillover fridge. Estimated at just under 25ah underway nav lights at night at anchor , anchor light at night and 2 lights in cabin for about 3 to 4 hours a day . Vhf as needed approx 30 min per day . All lights led so power usage underway approx 2ah in port all lights approx 1ah.
Second largest power hog is my watermaker. 4ah per hour when needed approx 4 hours per week if underway for more than 2 weeks. Not needed at anchor. No chart plotter no radar no nothing that wasn't stock for the boat. Sheet to tiller steering so no auto pilot.

I have as stated 400 watts solar and 400 watts wind feeding a 200ah Lfp bank so have approx 160ah available before bingo time.
I don't motor unless necessary. ( its called a sailboat for a reason) last boat did about 15 hrs motoring per year so likely less than 20 hrs a year motoring this boat.

[newhaul]

Originally Posted by stormalong

Here in Puget sound I think your 400 watts of wind will disappoint you.



You say nothing about your electrical demands. Do you have refrigeration? Are you day sailing or cruising? Is the boat in a marina with shore power nightly? All these questions need to be answered before deciding your question.

I am estimating my refrigerator usage from experience with technautics systems.
Have counter so the rest is known usage as stated approx 35 ah day once the refer is in and operating.
No don't do marinas much but when I do its reciprocal moorings .
And no I don't plug my boat into shore power. Even in my home marina. Unless needed in winter.

[newhaul]

Originally Posted by noelex 77

35 Ahrs a day is very low. 400w of solar and 400w of wind should be much more than you need to cover requirements without thinking about the generator even in unfavorable conditions.

Normally, the alternator is easy alternative supply of electricity so it makes sense. Most marine engines have an alternator fitted as standard. However, given the difficulties fitting an alternator in your case I would not bother.

I should have posted a picture of the front of the engine to show the optional alternator mounting position and how far the drive pulley extends past the flywheel.