Generator question

dbird · **Joined:** Mon Feb 23, 2009 10:02 pm **Posts:** 45

I came upon a You Tube video showing a portable generators exhaust being routed into a 55 gal barrel of water via a braided metal hose. The exhaust/engine noise was reduced by probably 80%. What is everyone's thoughts about utilizing this same technique with a portable generator off the swim deck. I have a great running lightweight generator that is just slightly quieter than a 747. I would use it very sporadically, just to charge batteries. This would NOT be used for extended periods of time or overnight on the hook. I have considered the issue of back pressure, anyone else have any thoughts. I realize a Honda generator would be ideal, but this one was free.

ric · **Posted:** Wed Jan 04, 2012 10:13 am

I made a post about this (battery issue).

It's cheaper/easier to swap the electrics on the boat for more efficient products. Just going to LED lighting can make battery runtimes go from 3-4hrs to 24hrs. If you have a TV, sell it and purchase an LED/LCD. A 19" LED HDTV draws 25 watts at full power. I bet your anchor light is doing more then that if it's a standard bulb.

Start with the bulbs. Purchase LED navigational lights. Purchase LED bulbs for interior lights and gauges. If you have an old tube tv, get a LED flatscreen they're like $150 now (make sure and get LED, the standard LCD's draw tons of power)

I did that to my boat. With just my single dual purpose battery my runtime with anchor light and radio going went from 4hrs to 18hrs by just swapping to the attwood LED pole.

Your boat is a 1993, it's time to update it to 2012 technology instead of band-aiding it with 1993 ghetto engineering.

Paul I. · **Posted:** Wed Jan 04, 2012 10:29 am

You just want to charge up the batteries, right?? I take it you have 2 batteries right now. Why not add a 3rd battery with a combiner to keep it charged up. Changing over to LED lighting will help too.

Running a generator that is not made for a boat, is not the safest thing to do. Never mind setting it up too. The 3rd battery, your just moving a switch.

dbird · **Joined:** Mon Feb 23, 2009 10:02 pm **Posts:** 45

Thanks for the responses. I currently have two deep cycles in parallel plus a starting battery. This whole generator idea would only be to charge the deep cycles. The generator I'm talking about is 4 stroke, its just pretty darn loud. (Coleman 1850 I think) I agree that safety is of utmost importance, but I don't believe the Honda's/Yamahas that everyone uses are marine rated either. The braided hose w/adaptor is exactly what I was thinking. The LED upgrades have already been done, the TV never gets used.

Paul I. · **Posted:** Wed Jan 04, 2012 11:41 am

Just a thought? Batteries should not be connected in parallel, except when needed. One of them can discharge into the other, making them both dead. A combiner or even better a isolator, should be used.

Stupid question, if all you want to do is charge up the 2 batteries. Then why not start the engine off the starting battery and charge them up. It would be faster & easier to do. The alternator is going to put out 50-100 amps, depending on speed of the engine & ......... The on board charger is going to put out between 5 to 20amps depending on the charger.

For give me, I too have 3 batteries, all AGM & (no genset) go on 1 to 3 day trips with out any power problems. I just start the engine for hot water and charge the battiers too. More often, I need the hot water way before they need a charge.

dbird · **Joined:** Mon Feb 23, 2009 10:02 pm **Posts:** 45

Paul, I think you are right. It's a slow day at work here in the winter..... just thinking of projects for the spring. Thanks for the insight. As far as your comment regarding the batteries, could you explain why having the two deep cycles in one bank is a bad idea? I thought that was common to have numerous batteries in parallel on the "house" side of things.

ric · **Posted:** Wed Jan 04, 2012 1:59 pm

You def need an isolator. No two batteries are the same, so the difference in voltages will cause them to "charge" eachother until they are both dead. It also limits the amps allowed across the terminals to avoid fires. If you get real fancy, you can get a low voltage cut off switch that shuts off the circuit when it gets around 50% discharge or 12.0v so they last longer.

Just doing that and doing a full LED light swap along with getting more energy efficient appliances will probably get the battery life you want out of the boat, without firing up the 747 APU.

Two good AGM deep cycles (over 180 amp/hr total and 100 usable) is enough power to run 60 watts of power draw for over 20 straight hours. To give you an idea... a standard anchor light at night is 35w. Run that from dusk to dawn (10hr), that's 2.8 amps x 10hrs or 28 amps. You just wasted 28 of those available 100. If you run it for 2 nights, that's nearly 60 amps of the available 100 just running a stupid light. If you change that to an LED anchor light that takes 1.8 watts, it will use 2 amps per 10 hours or a total of 4 amps! You have 95 amps available still! That's enough to watch a decent LED/LCD TV that draws 50 watts for 23 hours! If you didn't use the LED anchor light, you'd only have 10 hours of TV with the LCD/LED. If you're using a 13" TV/VHS old school combo TV... that thing is drawing 300-400 watts! Just that TV alone will drain your house batteries in under 4 hours!!!

Now imagine if you change all your lights to LED?! The problem isn't the sound of the generator, the problem is you shouldn't need to use it at all. You're bleeding power. We didn't have the knowledge or technology back in 1993 when that boat was made, but we do now and it's easy and cheap to retrofit. Also modern inverters also have a much much better power conversion factor. If you have the original one and let's say for example it's rated for 400 watts... it could be using 800w to make that 400. Good modern ones are over 90% efficient now and only use what you use. A 400w inverter on a 20 watt blender will only use 25 watts from the battery... not 450.

Paul I. · **Posted:** Wed Jan 04, 2012 2:20 pm

dbird wrote:

Paul, I think you are right. It's a slow day at work here in the winter..... just thinking of projects for the spring. Thanks for the insight. As far as your comment regarding the batteries, could you explain why having the two deep cycles in one bank is a bad idea? I thought that was common to have numerous batteries in parallel on the "house" side of things.

When one of the batterys eventually dies, it will drag the other one down but this happens whenever two batteries are in parallel and one dies, the only difference here is it is going to happen sooner to both. Since there wired in parallel all the time. So big deal, you gained some use out of the bad one and the good one will not be permanently damaged - just charge it up again. But when you really need it, it may not work!!

I would at least add a combiner to charge them and a battery switch to put them into parallel when needed.

dbird · **Joined:** Mon Feb 23, 2009 10:02 pm **Posts:** 45

It sounds to me that I need to get the house batteries separated more than anything else. As mentioned, the LED upgrade (except for the gauges) has already been done, and the tv doesn't get used unless we are on shore power. I have not yet run into any power issues, I was just considering the generator idea as a backup plan. Thanks

ric · **Posted:** Wed Jan 04, 2012 4:08 pm

well, if you're worried about charging why add a second engine to charge when you already have one? Rule of thumb is your alternator should have 25 to 50% of the battery bank capacity. You have three batteries and if they are the usual size you need a 85 to 120 amp alternator on the boat's engine. If it's the factory alternator with an internal regulator... it will never charge them fully because it doesn't have the circuitry to know if they are charged or not.

They sell alternators with external regulators that are designed for marine/battery bank applications that are battery "aware" and capable of fully charging banks of batteries very quickly and will not overcharge them. They are very popular in the sailing community because their inboard engines purpose is mainly power generation/battery charging.

I would look into that if you're going to be out on extended trips. I hate band-aids. Carrying around a small generator to charge batteries is ridiculous, especially rigging up a hose to the water to quiet it down.

dbird · **Joined:** Mon Feb 23, 2009 10:02 pm **Posts:** 45

Uuugh, Again, I don't have a charging problem. It works just fine. I was just curious about quieting a free generator. Will definitely look into the isolator before spring.

ric · **Posted:** Thu Jan 05, 2012 12:19 am

dbird wrote:

Uuugh, Again, I don't have a charging problem. It works just fine. I was just curious about quieting a free generator. Will definitely look into the isolator before spring.

My wife would have beat me across the head if she caught me engineering a hose to the exhaust of a generator and having it blow the water and sounding like bong rips from college. The guy side of me wants to try it out and design a cool quick release hose system that would accomplish this feat using aerospace technology, but in the end you're still just that guy on the dock who duct taped a piece of garden hose to his generator cause he was too cheap to buy a quiet one.

That being said, the highest rated rubber/plastic based pipe around is only good to 500*f. You would have to make said pipe out of metal to avoid burning your boat down after it has time to heat up (and not just make a video). That or design a heat sink/aftercooler setup to first cool the exhaust in the working range of the pipe. Boat engines use water.

dbird · **Joined:** Mon Feb 23, 2009 10:02 pm **Posts:** 45

I haven't engineered a thing. Just asked a question, which is what I thought this forum was for in the first place.

Paul I. · **Posted:** Thu Jan 05, 2012 8:52 am

dbird wrote:

I haven't engineered a thing. Just asked a question, which is what I thought this forum was for in the first place.

You are fine! Just add a switch to separate the 3rd battery. Again, you could add a combiner even better a isolator. OR you will need to close the switch to charge them off the engine. No need to over think this.

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