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Old 05-06-2006, 08:39   #1
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Portable Generator How-to?

I have a portable yamaha generator with a built in battery charger. Several questions:

1. How do I charge a twin battery bank with either the built-in unit or a seperate portable charger? Do I hook up to just one battery - or to both?

2. My shore power system is rated at 30 amps, is it possible to hook up the small generator directly to the shore power system even though the generator isn't anywhere close to 30 amps? This would be more convienent as I have 2 twin battery banks (group 31).

A high amp solar or wind solution is not in the budget at the moment.
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Old 05-06-2006, 12:04   #2
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Very few small generators have a true battery charger. Most have a 12v DC outlet, which is really only suitable for running 12v appliances.

Mine is unusual in that it has a 14.4v DC outlet, which will charge a 12v battery nicely (although I find my solar panel more than adequate for this.

if yours is a 12v only system, you are better off using a standard mains battery charger rated within the continuous capabilities of the generator.

Whether you charge a single battery or the bank will really depend on three factors:

total size of batteries

whether capacity in each bank is the same

size of generator/charger.
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Old 05-06-2006, 12:58   #3
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Talbot-
It's dangerous to generalize about these little gensets. For instance, Honda makes some very nice 1kw and 2kw gensets, but they warn you that the 12V outlet is for CHARGING ONLY. I've seen oscilloscope photos of the "DC" power coming out, and I can tell you it would terminally insult many 12VDC devices, it really is suitable for charging ONLY.

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Without seeing waveforms, your best bet is to ask the manufacturer. Sometimes "making" AC and sticking that into your AC power supply and reconverting that back to DC will work, other times it will burn things out, again because of waveforms and incompatibilities.
Your best bet would be to use the DC output of the genset to charge one battery at a time--assuming they say it can be used for battery charging, as most can--or to set your main power to "both" and charge them together IF they are both in the same charge state. Since your genset may be putting out very loosely regulated power, the odds are it will not be as good for your batteries in the long term as a dedicated "smart" charger would. Might be better or worse than engine charging...but you'd need to know more about voltages and waveforms to be real sure.

Just remember charging onboard can be very dangerous if you wind up getting monoxide from the exhaust on board, make sure that genset is venting downwind of you.
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Old 05-06-2006, 13:11   #4
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Amfivena,

Just plug the generator into your 30a shorepower using a "cheater". I use my Honda EU2000i and charge my batteries using the built in charger in the boat. Many cruisers are using the 2000i now as an economical generator.
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Old 05-06-2006, 13:16   #5
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charging

You should be able to use your charger with the AC from the generator but you need to check to see what the charger wattage rating is and make sure it is within the capacity of the generator. On my boat the Heart inverter / charger can be adjusted to allow for lower draw settings when available power is limited.
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Old 05-06-2006, 13:48   #6
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Thanks for the info everyone.

Ventilation: I'm well aware of the dangers... I went with the 1000 Yamaha as it fits perfectly on my boomkin and thus vents directly over water and as far down wind as possible. We have a CO detector to keep us out of the news on those rare occasions when the exhaust would still make it down below.

I'll have to check out my shore power specs to see if the charger can handle a light load.

Until then I will need to use the Yamaha's built in charger - it comes with a pair of 12v leads. Do I charge each battery individualy, or can I charge one bank at a time by bridging the two batteries in the bank?
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Old 22-07-2006, 18:59   #7
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We plug our portable generator into our 30 amp shore power inlet. Our charger is rated at 2.5kw. Our generator is rated at 2.4kw. But, the charger NEVER goes up to the possible capacity of the generator. Our charging amps stop at about 55 amps. This is at 13.1 volts during the bulk charge phase. This is about 720 watts. Way under the 2400 watts possible. The only way I have been able to cause it to go higher is by turning on another AC load. This will let me go up to about 75 amps for a pretty short time. I took to turning my water heater on while I was charging.

I set my generator in the front of the boat and close the hatches. We have CO detectors in the 3 cabins and one has never gone off because of the generator. But, be VERY careful, it is dangerous. Don't fall asleep with it going. Don't leave the boat with it going. But, I am sure you know all that.

Keith
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Old 22-07-2006, 19:02   #8
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Oh, I looked at the specs on my charger, it says it will decrease its draw when it does not see at 3500 watts. I imagine if your charger is a marine smart charger, it also will limit its draw.

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Old 23-07-2006, 17:32   #9
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On Makai in the rare times we needed to charge we would use our Honda 2kw to charge thru our 100 amp Heart charger. The highest out at 12 volts we ever saw was 77Amps. The limiting factor is the the genset.

We have helped several cruisers configure thier charging with 1kw units. The 100 amp charges would have to be configured to have a reduced max amp draw on 110 volts to prevent the charger from overdrawing the genset and tripping.

Only in emergency would I ever use the 12 volt output from the genset. It is only 8 AMPS @ 12 volts vs 77 amps @ 12 volts via the 110 charger. It would take forever. Waste of fuel.
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Old 25-07-2006, 09:27   #10
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Strygaldwir,
Have a look at this article from Xantrex which talks about inductive and resistive loads. The short of the article is if you are using your generator for charging only, then you need to put a capacitor in the output from your generator.

http://www.xantrex.com/web/id/735/docserve.asp

The other neat feature of the Link 2000 battery monitor/charger is you can control how much charge current the charger uses which is useful when using the smaller generators.

Kevin
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Old 25-07-2006, 09:56   #11
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KevinE,

Interesting although I don't know if I understand it, being a bit challenged when it comes to anything electrical. I do know I have seen 80 amps out of my Zantrex inverter/charger when using my Honda EU2000i. I think the Zantrex is a 100 amp charger. The Honda has an inverter in it, (hence the "i"), don't know if this makes a difference. All I know is that this is the most common portable generator as far as cruising goes. Most have a 2000, the 1000 doesn't seem to cut it.
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Old 25-07-2006, 11:36   #12
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KevinE;

Thanks for the link. It explained a lot of what I was seeing. When I turned on my resistive loads (AC waterheater), the charging rated would always go up in the bulk (charge) phase. I may add a capacitor to the generator, if there is a convient way of doing it. More likely, I will build and intermediate plugin box and hose it there. Or, I'll just live with it as it is. Hopefully the additional solar panels will mitigage the necessity of using the portable for charging.

Keith
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Old 25-07-2006, 12:15   #13
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"The short of the article is if you are using your generator for charging only, then you need to put a capacitor in the output from your generator." Actually, the metion using BOTH a resistive load AND a capacitor, not just one. And they suggest it only for their own inverter/charger equipment, I'm not sure how well it would work with other designs and products.

I don't think their tip applies to the Honda's EU-series, which are sold and rated with the 12v output being suitable for battery charging ONLY, and not suitable for running 12V equipment. I've seen oscilloscope traces run on that output, and while it is suitable for battery charging, it would indeed give any 12V equipment a heart attack. In fact, quote the opposite, adding a suitably large capacitor might smooth it out enough to run DC equipment on it, but that could well bring on other problems.

Vasco-
At least for the US models, those Honda EU10000 models also have a bridge cable available, you can buy two of the smaller units and bridge them for higher power output operating as a single unit. One might ask "why on earth" but it would give a certain flexibility and redundancy that way.
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Old 25-07-2006, 20:29   #14
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Charging

I have a 1000 watt Honda which I assume is similar to your unit. It puts out 7 1/2 amps when charging DC. Sometimes I use the AC side and an automatic charger. If either charger system is connected to one battery, then turning the selector switch to both should charge both. Same thing with a solar panel, but you are going to need two 65 watt units to get about 7 amps. I have one 65 watt unit. The alternator is the best for charging away from the dock, so fishing ( trolling ) works well, as long as you catch something now and then. If you charge both batteries together, it is best if they are both the same type and age. Mine are not, but it is not a perfect world. And I did have fish for dinner two times on my latest cruise, and the fridge was on for over one week, and the frozen stuff stayed frozen. Sometimes I charge both together but often one at a time, and then I check the volts with a meter.
Michael
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Old 26-07-2006, 06:49   #15
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"Do I charge each battery individualy, or can I charge one bank at a time by bridging the two batteries in the bank?"

Actually, charging battery banks in parallel should not be a problem, the only time you have to worry about the size differential of the batteries is when they are in series. Most chargers are of the constant voltage type, i.e. they maintain a "float" voltage (unless they are in boost or equalize mode), and generators do the same thing, unless their charging voltage regulator is broken. The batteries will accept the available current the charger will produce depending on their size (the larger one will charge slower given a finite charge current then the smaller one). When the charger reaches it's float charge voltage then both batteries will be at about 80% charge. The rest of the charge (final 20%) will occur while at the float voltage (the final 20% of teh charge takes 80% of the charging time). The math works out that they will reach a full capacity state at about the same time (assuming both batteries are in the same condition).
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