Honda Generator.

thataway · Posted: Wed Jan 09, 2008 6:28 pm Post subject:

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).

Sea Wolf · Posted: Wed Jan 09, 2008 7:54 pm Post subject:

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. Embarassed

journey on · Posted: Wed Jan 09, 2008 8:22 pm Post subject:

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

Dora~Jean · Posted: Thu Jan 10, 2008 2:43 am Post subject:

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.

JamesTXSD · Posted: Thu Jan 10, 2008 8:55 am Post subject:

Good explanation, Steve. I learn a LOT hanging around this place! Thumbs Up

drjohn71a · Posted: Thu Jan 10, 2008 9:09 am Post subject:

Thanks, Steve, Dr.Bob and all! Really helps to get proper perspective!

John

Dora~Jean · Posted: Thu Jan 10, 2008 10:54 am Post subject:

Thanks for the compliments! I was pretty good in school but not very good at teaching...I tend to get too deep. Confused

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.

bshillam · Posted: Thu Jan 10, 2008 12:20 pm Post subject: Leave the inverter home....

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..... Thumbs Up

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.

Doryman · Posted: Thu Jan 10, 2008 12:37 pm Post subject: Re: Leave the inverter home....

Larry H · Posted: Thu Jan 10, 2008 1:59 pm Post subject:

Honda Generator owners,

Here is a link to an RV site showing photos of an exhaust extension for a Honda 2000i.

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/20038531.cfm

Larry H

drjohn71a · Posted: Thu Jan 10, 2008 3:15 pm Post subject:

Bshillan,

you can buy the black "yoke" they make to tie two Honda i2000s together and attach it to the genset. It has a 30 amp, twistlock receptacle into which you can twist lock your shore power line. That way there is not extra wiring and the 110V comes directly into your 110V box just as if using shore power.

John

journey on · Posted: Thu Jan 10, 2008 3:39 pm Post subject:

Well, you can eliminate the inverter, and just run batteries and a gen set. But, if you want to have 110 VAC underway, one must have an inverter. I'm thinking of running the laptop for navigation, or even (gasp) popping popcorn underway. Granted, it doesn't have to be as big, but you still need one. Yes, you can run the generator underway, but that might be messy, hanging it over the transom.

And, just as a freebie, Peukert's Law has nothing to do with recharge. It allows one to calculate battery state-of-charge as a function of the discharge rate. Recharge is a different story, and to the best of my knowledge is more a rule of thumb.

Boris

Addendum:

Peukert's law is as follows:

C_p = I^k t ,

where:

* C_p , is the capacity according to Peukert, at a one-ampere discharge rate, expressed in A·h.
* I is the discharge current, expressed in A.
* k is the Peukert constant, dimensionless, varies between 1.1-1.3 and the age of the battery.
* t is the time of discharge, expressed in h.

Pat Anderson · Posted: Fri Jan 11, 2008 8:32 pm Post subject:

Too esoteric for me, Boris, Joe, et al...

Point of interest, just recently got a flyer from Harbor Freight Tools, they will sell you a 1000 watt generator (Chinese?) for $299...there is a brand new Harbor Freight Tools retail store in Bellevue on N.E. 20th, just a little west of the big Overlake Fred Meyer store.

Sea Wolf · Posted: Fri Jan 11, 2008 11:02 pm Post subject:

TyBoo · Posted: Fri Jan 11, 2008 11:16 pm Post subject:

Hey Pat!! You misspelled esoteric. Of course, I only know that because I had to look it up to see what it means.

I bought a Honda 2000i last month when the lights were out. Paid $999 for it but I was one of three dozen who ordered them the day before. I like and trust the store (get my John Deere stuff there, too) and the unit was serviced, test run and full of gas. I have been wanting one for quite a while so I almost welcomed the excuse to get it now. It's good. I like it.

It is hard to find a price for the things online except for ebay. Most dealers listing them on the web tell you to call for a price. The one for $879 delivered was a good price. The outfit that sold me mine keeps them on the shelf for the same price as he charged during the 5-day power outage. I have seen them on sale there for a hundred less.