Generator Size

G

Grey25

Member
Joined
Apr 16, 2020
Messages
10
Fluid Motion Model
R-25 SC
Vessel Name
Sisu L&B
Hello, We have a Ranger 25 SC with 4 AGM batteries. I am looking to get a generator to top off the batteries on those days when we spend a few nights on the hook. We are not high power users (Fridge, water pump, LED lights, stereo). I do not want to add additional weight to boat what would be the smallest generator in size (wattage) that we should get or need. Thank You in advance
 
I dont have a generator recommendation, but a larger solar panel will work just as well...

I have a 340w panel. my house batteries are charged quickly in the morning. some folks have 2-200W panels which at max is 33Amps at 12 volts. that's as much as a generator puts out.

Now the issue is if you have continuously cloudy days... some folks use a portable generator for those cases. there are a quite a few posts on tugnuts with portable generator recommendations - safety is key but they are much smaller/cheaper than an installed generator and can be removed when not used.
 
I have a built in generator and would not buy a boat with another, most likely. The maintenance has been far worse than any other part of the boat and access is beyond ridiculous. It took a well seasoned generator mechanic 2 hours to change a broken switch that was completely inaccessible and multiple parts needed to be removed before you could even see the defective switch. If solar is not adequate, and I'm not sure I'd want to go that route, I'd get a portable generator. Fixing one of them, and doing maintenance, would be a dream by comparison. I have a Westerbeke 5.0 MCG gas generator.
 
Grey, if your 'need' for additional watts onboard is only occasional, that hints at an 'only occasional' solution. You could consider the EU2200 Honda we occasionally use to solve the issue (about 60# with fuel) altho' for mucho dinero. OTOH like Cutwater28GG, we like our 200W of solar altho' that too comes at a price. But are you sure you actually have that 'need'? At summer temps and with relatively new AGMs, you probably have ~350 AH of useable battery capacity. What has been the remaining capacity of your house bank on let's say Day 3 of the scenario you mentioned? The 'internet wisdom' that one "must" only draw down the wet cell batteries by 50% is an imperfect generalization. If 300-350 AH would get you those 3 days at anchor once or twice a season, you are not going to significantly impact your house bank longevity by using perhaps 75-80% of your bank one or twice a year. OTOH if those AGMs are not relatively new, you have used the boat a fair bit and/or your boating season isn't full of warm temps, you won't have 400 AH of capacity. I'd suggest you use one of your next weather windows to put the bank to a test. Be 'modest users' and see if 3 days is do'able. (NB: Quality wet cell battery manufacturers use to publish "# of cycles vs. average capacity used per cycle" charts that predicted performance in the field. I don't see them anymore but they suggested that an occasional deep drawdown would not significantly impact longevity. Much more impactful: low temps, battery aging and, when appropriate, regular equalizing).
 
An AGM cell at 50% has a voltage just at or under 12V without load on the bank (open circuit voltage). With heavy load this can easily drop to high 10s or low 11s. This gets worse as you head towards 25% draw down in the bank.

The result is devices will draw more amps (compared to 13V), generating more heat in cabling, and more likely blow fuses/breakers. And when drawing more amps that means you’ll drain the batteries faster with the same device loads on them.

So regardless of impact to the bank, there are other considerations when drawing down a cell more than 50%.

A few times is fine, but consistent draw down below 50% will impact the number of cycles on your bank.

 
Grey25 said:
Hello, We have a Ranger 25 SC with 4 AGM batteries. I am looking to get a generator to top off the batteries on those days when we spend a few nights on the hook. We are not high power users (Fridge, water pump, LED lights, stereo). I do not want to add additional weight to boat what would be the smallest generator in size (wattage) that we should get or need. Thank You in advance
Click to expand...
I use a 3,300-Watt Gas-Powered Portable Inverter Generator on our 25 Ranger Tug.25 Ranger.jpg
 
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