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  #11  
Old 02-10-2013
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Re: Are portable generators safe?

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Originally Posted by sstuller View Post
It's fun comparing a battery bank to your savings account. If you have a regular income your savings account doesn't have to be as big as the case of the fellow whose income is intermittent. He needs an account big enough to cover the times when there is no income. A generator is similar to a regular income while relying on solar/wind is like the fellow who gets temporary employment and has to put a lot in the bank to cover periods of unemployment. Trojan Battery calls that time period the "days of autonomy". It recommends five days of battery capacity if you are relying on solar only while saying two days of autonomy is sufficient for dependable charging. The battery consumption in both cases may be the same but the charging frequency determines your battery capacity. Thanks. Steve S.
I have to respectfully disagree with this.

Though I see the theory in what you are saying, in practice it doesn't work that way at all. In practice if you are using a generator to keep your bank charged then your bank will almost always be less than fully charged. As soon as the generator stops running the loads you have on the bank start depleting the bank and you aren't likely to restart the generator until you "need it" (meaning the bank has dropped to some specific level of charge or something like 12.1 volts, or whatever ..). So with a generator your bank is usually in some state of discharge.

With solar and wind it is just the opposite, because your solar panels are almost always charging unless there is bad weather or at night, you battery bank's natural state is charged, and it is only at night and during storms that it becomes discharged, and left on its own it will charge right back up.

I know it sounds like semantics, but it really feels different in practice. With a generator you are always kind of feeling guilty because you know you are slowly destroying your bank because you didn't get up and go out and start the generator when you should have, or didn't let it run as long as you should have to get a full charge on the bank (which can take many hours for acceptance charging). With a solar system it feels totally different, you feel like you are harming the bank if you put a huge load on it, but you know in the back of your mind that won't last and that once you stop abusing the bank it'll go back to "normal", normal being fully charged. When you walk away from your boat with a generator you're thinking, wow, I shouldn't have left without charging the bank, and I should come back in a few weeks and charge it again. With solar you walk away and think, wow, I'm sure glad I have solar, I turned the lights off and in a day or two the bank will be fully charged and it will stay that way until I get back.

I have a generator too, and I use it often if/when I run the bank down, but solar gives me peace of mind and if I had to have one or the other I'd keep the solar panels.

To use your savings account idea, using a generator feels like work, you have to do something to put the money back into the account. But solar panels feel like a trust fund, it just magically happens, and even if you run the account to zero all you have to do is stop spending for a while until it recharges. Like I said, I know it sounds like semantics, but it really feels different in practice.
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Re: Are portable generators safe?

I was just reading the latest issue of Boat U.S. mag. and in the section 'Ask the Experts'..Tom Neal mentions the use of portable generators on board could cause excessive zinc consumption due to the fact of the boat unique wiring thus inducing current into it's bonding system.. He therefore does not use them anymore aboard his boat.
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Old 02-10-2013
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Re: Are portable generators safe?

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Originally Posted by aa3jy View Post
I was just reading the latest issue of Boat U.S. mag. and in the section 'Ask the Experts'..Tom Neal mentions the use of portable generators on board could cause excessive zinc consumption due to the fact of the boat unique wiring thus inducing current into it's bonding system.. He therefore does not use them anymore aboard his boat.
Not only that the CPSC is looking into mandates for safety with these types of devices. People assume they are safe but the threat of CO poisoning is very real and the reported cases of CO poisoning from portable generators has skyrocketed.. I see boat owners nearly every weekend with the Honda up on the bow and a dorade, port or hatch directly behind it wide open....

To the OP I will mention it again AGM vs. FLA makes ZERO difference to the size of the bank. If you drop the size you simple run the generator more often. FLA and AGM BOTH taper/limit acceptance charge current once in absorption mode so both types of batteries have about 35% usable capacity.

35 usable Ah's on a 100Ah bank means you are running the generator A LOT.... Maybe this seems fine to the person running the genset every few hours, but try thinking about your neighbors.. You also lose the benefit of any Peukert effect on bank size which can't be under estimated.
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Old 02-11-2013
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Re: Are portable generators safe?

Perhaps I should note that I am talking about a 24 volt system so you have anywhere from two to four batteries (100 AH to 200AH) so there is a lot of battery capacity to deal with. I'm at a crossroads where I have to decide whether I go with just solar which means more panels and more batteries or go with the generator and its' problems. Or all of the above. I'm relying on solar now but demands are minimal. When I start thinking about increasing demand then things start to get complicated. Thanks. Steve S.
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Re: Are portable generators safe?

An estimate of potential demand is one KWH to two KWH per day for several days in a row. Given cloudy weather you would need a huge battery bank if you are relying on solar only. It seems to me that a generator is unavoidable. Thanks.
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Re: Are portable generators safe?

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Originally Posted by sstuller View Post
An estimate of potential demand is one KWH to two KWH per day for several days in a row. Given cloudy weather you would need a huge battery bank if you are relying on solar only. It seems to me that a generator is unavoidable. Thanks.
1-2 kWH is 1000 - 2000 watt hours...

1 kWH = 1000 WH / 24V = 41.6Ah's / Day
2 kWH = 2000 WH / 24V = 83.3 Ah's / Day

There are plenty of boats out there with wind and solar producing 40 - 80 Ah's per day..

Our little 140W panel pumps out about 27-35 Ah's / day....

Do you not also have an alternator? Still with a 100Ah battery bank and 80+/- Ah per day of use, and only a generator, your really digging into the DOD of the bank or running it a lot... Remember that you still really only have about 35 Ah's to use in a 100Ah bank unless you let the gen set recharge for 8-10+ hours to get to full...
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Re: Are portable generators safe?

A 100 ah bank isn't sufficient for more than one day of hanging on the hook.
The usable 35 ah goes pretty darn quick, even at 24v.

Like Wind_Magic I think you have your analogy with savings account somewhat off.
The Solar input is like a salary with commission; constant input, sometimes with a bonus. If you plan your array sizing right that's how it works.
At 300w, I plan on 50ah a day, and on good days I'll have 90
To get the same from a portable 2kw generator plugged into my charger (which is a 20 amp) - assuming my bank is down enough in charge to accept a bulk load - I'd have to run the generator for 2 hours to get 40ah (max) then go to absorption charge mode for a couple hours to top off. Let's call that 6 hours of running a generator.

Every day.

The solar panel just quietly and efficiently puts in 8 or 9 amps a hour, then tapers down to fill it and I do nothing. Even on a cloudy day I get SOME charge, and with 500 ah, I got a lot of days of hang time waiting on some sun shine.

To your original question - yes, portable generators are safe provided you use them properly. They even have a purpose - in my case for running 120v stuff that my 1kw inverter can't handle (air conditioner, bread machine, tools, stuff). As a primary (non- inboard / alternator) method of charging, no way.

It's the exact opposite of your post, you have no autonomy at all, especially on a mooring. You must row out, check the state of charge, fire up the gen, sit there and wait several hours, then row back.
With solar you just have to sit at the yacht club bar and be smug.
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Re: Are portable generators safe?

As far as battery configurations, I found that having 2 banks was the only way for us to maintain what we needed.

When underway by sail, we primarily depend upon our solar panels to charge our batteries. So, we are charging one bank, and using the other.

Otherwise, with only 1 bank, we would fall behind because we were using and charging the same bank of batteries.
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Re: Are portable generators safe?

You folks are really helping me to make a decision at this fork in the road. It's beginning to look like solar is a better choice than the gen set route. The moment of truth will come when I have to put my money down i.e. place my bet on one or the other. Hopefully reason will prevail over emotion. Thanks. Steve S.
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Re: Are portable generators safe?

I can't over emphasize the value of having TWO BANKS of batteries to go along with a robust solar power system.
Otherwise you are setting yourself up for a guaranteed slow decline.

Two banks provides you a lot of wonderful benefits!
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