Honda Generator.

Joe, you left out only one thing...with your system of paralleling four big batteries without dedicating a battery to starting the motor, you ought to have a big honking jump start unit on board so you can get the motor going if you should happen for any reason to discharge your batteries too low to start the motor. Maybe you never will. But then again strange things happen. Of course you can wait for the generator to recharge the batteries - but sometimes you just want to get going. Whatever a person decides to do for electrical power, it seems to me a big jump start unit is kind of the ultimate peace of mind.
 
Joe,
For many of us with twin engines the picture is a little more complicated. Twins require separate and more complex battery setups. Your system with a single engine is simple and elegant but when dealing with twin engines two separate systems are required. I only have two batteries-one for each engine. They are always isolated and I take all house loads from one battery or the other. While cruising I use #l on odd days and #2 on even days to even out the use. I don't yet have a battery charger but since I just acquired a Honda 2000 for RV use I will install one this next season. This system works for me since I have no high amp draw equipment like heaters or microwaves.
 
Pat-

You're right about the jump start unit. I have one in the floor compartment at the foot well for the helm, and leave it plugged into the 120 volt system so it gets charged whenever the system is powered up from either the generator, inverter, or Shore Power. I haven't had to use it yet, but it adds a bit of peace of mind because it's always there. I mentioned this on the other thread on jump start units a couple of days ago.

Ken-

You're quite correct about needing two batteries or two battery systems with twins! Good point! I left this out because I just don't face that problem, so it's not on my mind.

This problem with twins comes about because each motor's alternator is sensing the voltage built up in the battery being charged, and adjusts the charging rate to match the state of charge of the individual battery. The problem when trying to use a single battery bank is that each motor senses the voltage applied by the other alternator and can't do it's job effectively. If one understood exactly what was happening with these sensors and relays, perhaps a system could be designed to overcome this problem. We need an electrical engineer at this point, I guess. Would be a fun project. Might be a very marketable product involved.

Both Pat and Ken have very valid points! I wrote the post once, then lost it in cyberspace, and wrote it again near midnight, so it might have other omissions as well.

Fun talking with you both!

Joe. :thup :teeth
 
Joe,

I talked to the chief engineer at Balmar about the "two engines charging one battery bank" question. His opinion was that it can't be done in such a manner as to take advantage of the full charging capacity of each engine. As we know, these outboards don't put out a lot compared to the big 100-200 amp alternators used on trawlers etc.

The simplest solution I could figure, and I'm not an electrical wizard or engineer, was to have two AGM dedicated start batteries. When they are fully charged, which takes a very short time, the BlueSeas ACR connects a AGM house battery to each start battery and brings it up to full charge during the day while running. At anchor, the two 255AH house batteries are connected using the "1,2,both, off" switch. The ACRs open automatically isolating the fully charged start batteries.

The combined 500+amp hours is sufficient for the 2000w inverter and all house loads for a couple of days at least. I also select batt 1 or 2 to run house and electronic loads underway by the odd or even day of the month. This was the most idiot proof way I could think of. If I forget to isolate the 2 battery banks before starting up, no harm is done other than less than optimum charging until I remember.

I think for this Summer, I'll put a reminder tag on the steering wheel or ignition switch.

With the ability to manually connect a house battery or both house batteries to either start battery, I feel a jump start unit is unnecessary weight. I also carry a Honda 2000i for hot water in the AM.
 
Roger-

That sounds like an excellent solution to me! Well thought out, practical, and as simple as possible under the circumstances. Great job!

This solution and others of this quality should be documented or made into an easy to find "Sticky" of some type for others to find easily. Some of our best thinking is often buried in innocuous threads that belie what lies within! I could easily sort through all of these threads and write a book digesting the real problems, facts, pros and cons, , and solutions out.

Your work has always been of the highest quality as documented in your photo album, the electrical layout and execution being a model for others to emulate.

I'm looking forward to meeting you and Janet at the SBS/CBGT this month!

Joe. :thup :teeth
 
I went by WalMart yesterday and turned all of the microwaves around to see what the power draw was. The only one which would be handled by the 1000 Honda is the 600 Watt Galvez (sp?). The 700 and 800 watt units refer to the output, not the input--and the amperage draw is over what the 1000 puts out max. The GE 700 watt microwave I have tripped on low, but I will have to experiment some further. We end up using the inverter as Joe says.

There are many ways to wire the two engine boats. But to take max power out of the alternators, two house banks, one off each engine when charging, and then combine them, or use them separately--is the easiest plan.
 
OK, guys, I forgot to convert the amperage to 12 volts in the process of playing with the dog with one hand and trying to type and think with the other. Guess some of my common sense parameters went out the window too with accepting the answers, so I'll correct my homework errors below in red.

flapbreaker":1kmt6vgq said:
So how fast would a 2000 watt inverter drain a 110 amp hour battery?
Click to expand...

Bob may well answer this too, but here goes!

First of all, you shouldn't drain the battery down more than 50%, so we go from 110 AH to 55 AH really available.

A 2000 watt inverter at full power is supplying 120 volts at 2000 watts, so it must be providing 16.6 amps in the process:

Amps X volts = watts, and 16.6 amps X 120 volts = 2000 watts

Now to provide 16.6 amps at 120 volts the battery must provide 10 times the amperage at 1/10 the voltage, so we draw 166 amps of current out of the battery instantaneously.

Now we have 55 AH in our battery to draw out, so knowing

amps X hours = AH , and hours = AH/amps, therefore

hours = 55 AH/166amps = .33 hours


So we have .33 hours of run time for our inverter running at a full load 2000 watts on our 110 AH battery.

Furthermore, we need to subtract about 10% for the inefficiency (released as heat) of the inverter, so we get 0.3 hours of real run time, about 18 minutes or so from this rough calculation that doesn't consider everything, either.

Sorry if this is too detailed or wordy, but my background as a science teacher is hard to leave behind!

And now I've corrected my homework. :oops: Do I have to stay for detention too?:unlove

Joe. :thup :teeth
 
Joe,

There is more to the story than simple math.

If an inverter is putting out 16 amps at 120 volts, it is drawing 160 amps!! from a 12 volt battery. The ratio of 120 volts to 12 volts is 10 to 1, so the current draw on the 12 volt battery is 10 times the output current at 120 volts. Actually, considering efficiency losses, the draw would be higher.

That 110amp hour battery won't last long when the draw is 160 amps!!

Most 'experts' say that wet lead acid batteries should not be discharged at rates higher than 25% of amp hour capacity so for a 110 AH battery that is 27.5 amps. 27.5 divided by 10 is 2.75 amps at 120 volts, which is 324 watts. (120 volts times 2.75 amps)

A correctly sized battery bank for an 2000 watt inverter would be 160 times 4 = 640 amp hours of capacity. Since only 50% of the bank is available, the run time would be: 320 amp hours divided by 160 amps = 2 hours.
 
I am with Larry on this one! I do not like inverters at all. We do not have enough battery power aboard to handle the very rapid, heavy loads that inverters put on them. On top of that, there is a 10-15% efficiency loss even on the best setup.

I have two Honda i2000 gensets which can be put together for heavy use on the farm. I do leave one on the boat all the time, though.

They are great, quiet, powerful, and will run a very long time on half load, will run a 9-12,000 BTU A/C unit aboard, heat the water, run a battery charger - whatever. And great resale value too.

John
 
I agree with Larry, the 110 amp hour battery will give only about 25 or so minutes at 2000 watts draw without possibility of battery dammage.

As Larry points out, you need a big battery bank to run a large inverter. We had over 800 amp hours to run our air conditioner for a few hours on an express cruiser we owned. The Golf cart batteries hold up better in this type of service. Although some larger boats, with well over 1000 amp hours in the battery banks, can run large loads, this is just too much weight for small boats like the C Dory line. Then you have to look at how these are recharged. We had 150 amp alternators and 130 amp chargers, so that we could fairly rapidly put power back into the the large battery bank.

If you remember the recent thread on the Dashew's power boat--they run the entire 110 volt and 220 volt system off of batteries and inverters, but at 24 volts and with well over 1200 amp hour of massive batteries. They also have very large alternators and chargers, which are specially fabricated to allow adequate cooling etc.

So for any systained high loads, consider a generator. If you only need 2 to 5 minutes for re-heat they 220 amp hours of batteries will suffice. That is what I have powering my inverters (two group 31 AGM batteries).
 
Ok guys, I forgot to multiply the amperage by 10 for the conversion from 120 volts to 12. I corrected my homework on the original post, so it won't throw people who read it later off initially. Sorry, I was trying to play with the dog with one hand and think and type with the other! Should have caught the error from a common sense perspective of electrical experience! Do I have to stay for detention too?

Joe. :oops:
 
A comment on "quickly recharging batteries." Lead acid batteries have a taper charge profile. If you take out 100 amp-hrs, it isn't a matter of 2 1/2 hrs of recharge with a 40 amp charger, and you're back to full charge. It's about 1/2 hour at 40 amps, down to an hour at 20 amps and 5 hours at 10 to 5 amps. To get back to full charge would be overnight. That's why cruisers run their batteries at 85% charge, since the last 15% is so inefficient.

What's this mean? Well, when you figure out how much you take out of your batteries, remember to START at 85% of full charge, and plan to spend a few more hours on recharge.

Now when we go to metal hydride batteries, we'll be able to put full charge in until they're fully recharged.

Boris
 
It's one of those fundamental laws of batteries, it's called Peukert's Law (pronounced "poo-care"). Peukert was a German scientist, and in 1897, he expressed the capacity of a lead-acid battery in terms of the rate at which it is discharged. As the rate increases, the battery's capacity decreases. I won't quote the formula, this isn't school...

Most lead acid batteries are rated with a 20 hour discharge rate. So a 100 AH battery should produce it's full capacity at 5 amps per hour when new (but it may not be worth much if you run it to zero!) Any higher rate will diminish the 'effective capacity' rating of that battery. In other words, if you try to pull 50 amps out of that 100 AH battery, you'll probably get an hour or even less out of it, not 2 hrs as you'd expect. Same goes for charging, you have to limit your charge rate in order to have it accept the charge, just like others have said.
 
Thanks for the compliments! I was pretty good in school but not very good at teaching...I tend to get too deep. :?

But I wanted to add, that's why I like my Link 10 monitors, they take into account Peukert's Law in discharge and charging, very accurate report of your battery(s) state of charge at all times, even while using them.
 
So - based off all your feedback, best to leave the inverter off the system and buy a good gen. I think this is the easiest way to insure I have power when I need it and I can still charge the batteries for the day's use/or the night with the Wallas..... :thup
Thanks Brats, this is helping me too as I am building (or should I say having built) shore power and charger. It's pretty slick but I want to work within the limits of my system.
 
bshillam":3jlvi8jp said:
So - based off all your feedback, best to leave the inverter off the system and buy a good gen. I think this is the easiest way to insure I have power when I need it and I can still charge the batteries for the day's use/or the night with the Wallas..... :thup
Thanks Brats, this is helping me too as I am building (or should I say having built) shore power and charger. It's pretty slick but I want to work within the limits of my system.
Click to expand...

EQ is installing a single 240 Ah underneath my forward-facing dinette seat, along with an inverter. I was getting some battery-envy earlier but now after reading this thread I think it is a good solution. It will give me AC for light and/or short jobs, but the Honda needs to be fired up for more demanding tasks, such as the water heater or long cooking in the toaster oven (which we decided on instead of a microwave.)
 
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