Charging batteries with generator

[Ricco1]

One of the replies in the thread 'electricity for an idiot' thread I wrote suggested I break down my 'ignorance' into smaller areas, and ask specific questions. I think this is a good idea, hence the deluge of questions from me tonight.

 

This one concerns generators. I inherited a generator with the boat I just bought. I don't think it's a brilliant one, 650 watts, but was considering the possibility of using it to charge my batteries, rather than running the engine every day.

 

Obviously I'd need a charger and then work out how to best connect it to the battery/s. Might this be a viable thing to do or should I forget it and just use the boat's engine?

[ditchcrawler]

One of the replies in the thread 'electricity for an idiot' thread I wrote suggested I break down my 'ignorance' into smaller areas, and ask specific questions. I think this is a good idea, hence the deluge of questions from me tonight.

 

This one concerns generators. I inherited a generator with the boat I just bought. I don't think it's a brilliant one, 650 watts, but was considering the possibility of using it to charge my batteries, rather than running the engine every day.

 

Obviously I'd need a charger and then work out how to best connect it to the battery/s. Might this be a viable thing to do or should I forget it and just use the boat's engine?

You said in one of your other posts you had a charger

[Richard10002]

One of the replies in the thread 'electricity for an idiot' thread I wrote suggested I break down my 'ignorance' into smaller areas, and ask specific questions. I think this is a good idea, hence the deluge of questions from me tonight.

 

This one concerns generators. I inherited a generator with the boat I just bought. I don't think it's a brilliant one, 650 watts, but was considering the possibility of using it to charge my batteries, rather than running the engine every day.

 

Obviously I'd need a charger and then work out how to best connect it to the battery/s. Might this be a viable thing to do or should I forget it and just use the boat's engine?

 

I use a generator via the shore power socket, and a charger, which is then connected to the batteries via an isolator. Quite straightforward. Most suggest that it is better to have the wear and tear on a relatively cheap generator, rather than on an expensive engine.

[Ricco1]

You said in one of your other posts you had a charger

 

Yes, it's wired into the electrical system somehow, I'll see if I can work out how tomorrow.

 

I meant a 'normal' charger, like you might charge a car battery with; a plug then a box then a positive and negative crocodile clip to connect to the battery terminals.

I use a generator via the shore power socket, and a charger, which is then connected to the batteries via an isolator. Quite straightforward. Most suggest that it is better to have the wear and tear on a relatively cheap generator, rather than on an expensive engine.

 

 

 

That just might be possible with my boat. How do you find the charging time for the batteries, does it take longer than using the engine, or less time?

[ditchcrawler]

 

Yes, it's wired into the electrical system somehow, I'll see if I can work out how tomorrow.

 

I meant a 'normal' charger, like you might charge a car battery with; a plug then a box then a positive and negative crocodile clip to connect to the battery terminals.

IF you have a proper charger, correctly connected to your batteries and correctly connected to your shore supply 240 volt system. Use that.

Stop trying to bodge things that could end in a fire or with some of your ideas electrocution. Generators generate 240 volt, inverters supply 240 volt. both can kill you as easily as mains voltage in a house.

[Ricco1]

IF you have a proper charger, correctly connected to your batteries and correctly connected to your shore supply 240 volt system. Use that.

Stop trying to bodge things that could end in a fire or with some of your ideas electrocution. Generators generate 240 volt, inverters supply 240 volt. both can kill you as easily as mains voltage in a house.

 

I don't want to take risks like that, that's why I'm asking so many questions. And quite honestly, I'm completely ignorant on this topic. I'm looking for workarounds of course, using logic. Logic can be good, but can be dangerous allied to lack of technical knowledge, as I'm finding out! But finding out that these workarounds are unsafe is increasing my knowledge, I'm really grateful for that. I think Richard10002 might just have described exactly the system that's set up on my boat, I'm going to check it out tomorrow.

[Arthur Brown]

Having a flat battery is the end of cruising without help, so an alternative method of charging is very good. An automotive marked charger will probably peak at 6 amps which is fine for topping up small car batteries but for charging a flat starter battery it will take a LONG time. Better to look for a charger better scaled to your battery and generator. A 20 or 25amp three stage charger should run nicely from an 800w generator and achieve a reasonable charge time.

 

Properly install the charger and the cables with fuses or breakers, and leave some ventilation for cooling.

 

If you cruise then the engine alternator should do the charging for you, without cruising you really do need to get you power needs met by a generator or shoreline.

Edited August 16, 2013 by Arthur Brown

[bottle]

If the boat came with the generator and you already have the charger (wired correctly I hope), then possibly there is a connection cable for connecting the generator to the shoreline socket.

 

 

ps. never, never use crocodile clips for any connections, except 'jump leads' for emergency starting and even then very, very carefully.

[Ricco1]

If the boat came with the generator and you already have the charger (wired correctly I hope), then possibly there is a connection cable for connecting the generator to the shoreline socket.

 

 

ps. never, never use crocodile clips for any connections, except 'jump leads' for emergency starting and even then very, very carefully.

 

There is a short connection cable. A boat safety certificate was issued only last month. As the boat hasn't been used for a while, is that a fair bet that the electrics are all set up correctly?

 

My generator is only 650 watts, still practical to use for charging?

[bottle]

 

There is a short connection cable. A boat safety certificate was issued only last month. As the boat hasn't been used for a while, is that a fair bet that the electrics are all set up correctly?

 

Probably but without actually seeing your boat, like everyone else on this site cannot be absolutely sure.

 

My generator is only 650 watts, still practical to use for charging?

 

Yes.... but it will depend on the size of the charger.

 

sorry to be non committal but I do not want to advise you incorrectly.

 

I see on one of your other threads that you will take Tony's advice, good luck as he says it is a big learning curve, just take it easy.

 

ps. I am no expert, just self taught, lots of research and internet trawling.

[Tony Brooks]

Sorry about this but once again there can be no definitive answer because the answer will depend upon the "size" of a charger.

 

First of all that 650 watts is probably a lie. All AC devices apart from those that simply get hot suffer something called a power factor. This varies from item to item so once again it is not possible to give a definitive figure but a bit over 0.7 is usually good enough. In effect thugs means your generator may only have an effective output of 0.7 of the claimed output - so you can only work on about 500 watts and maybe a bit less.

 

Now at 100% efficiency a 12V 50 amp charger will require 600 watts of input so your generator will not power it while it pebbly will power a 10 or 20 amp charger.

 

Just to further complicate the issue. The voltage regulation and wave form delivered by cheap generators can be absolutely appalling and it is not unknown for items with electronics inside them to refuse to run. If your charger turns out like this some people have solved it by running the charger in tandem with a 100 watt light bulb. This is a "suck it and see" situation so if you are gong to buy a charger I would advise that you take your generator and make the vendor show you that it will work with the generator.

 

If you have a car type charger, as has been said, will have such a low output it would never provide a meaningful degree of charge but if its a modern one with two stages (a light that changes when it goes into float mode) it may show if your generator output is good enough to run a larger charger.

[by'eck]

 

There is a short connection cable. A boat safety certificate was issued only last month. As the boat hasn't been used for a while, is that a fair bet that the electrics are all set up correctly?

 

My generator is only 650 watts, still practical to use for charging?

 

A 650 watt output generator is very low compared with most used on boats and that may not be a continuous rating since manufactures tend to claim the max (short term) output.

 

It may just about power a 12 volt 20 amp battery charger though, which again is the very minimum size you should be considering. This means it would take a while (say up to 5 hours) to re-charge a single battery (standard 110 Ah discharged to 50%). If you have a bank of three similarly discharged that's as much as 15 hours, so as you can see not very practical.

[FadeToScarlet]

If you've got the genny already, getting a 20 amp charger and installing it would probably help.

 

It won't recharge as fast as the alternator off the boat's engine, but it would be quiter with less vibration, probably, which you'd find easier to tolerate.

 

If you had a depleted battery bank, you could use the engine to bring the state of charge up to 80% or so, and then use the generator to finish the charge off once the batteries get more charged and start accepting less current,

 

We had a 650w generator (Honda EX650) with a 20a charger on the last boat, and there was enough capacity in the genny to power the TV or radio from the 240v whilst charging.

 

The best thing to do would be to not let the batteries get that depleted- I'm a real fan of solar, we've enough to keep us self sufficient from about April-September without having to run the engine to charge, and it's great.

 

If I were in your situation, I think I'd get a 20a charger to wire in and use with the genny, which will help but not completely solve charging, and then get as much solar as I possibly could once I'd saved up some pennies.

[Richard10002]

There is a short connection cable. A boat safety certificate was issued only last month. As the boat hasn't been used for a while, is that a fair bet that the electrics are all set up correctly?

 

My generator is only 650 watts, still practical to use for charging?

The BSS is no guarantee its OK. I had a BSS a couple of weeks ago and the electrical inspection was fairly quick, although the inspector asked me several questions which I must have answered OK. He didn't run or test anything electrical.

 

Could you ask the previous owner? Who did you buy it from? Usually, if it looks like a duck, and walks like a duck, "it's a duck", so I'd be tempted to connect it all up and see what happens...... But I would want to understand it first!

 

e.g. Run a power tool or something off the genny - see what happens.

 

Is there a 240V system in the boat? I.e. ordinary household plugs?

 

Follow various wires from the charger and the shore power input and see where they go, and what they're connected to.

 

Check max amps of charger on its label, or google it - if less than about 30Amps, I'd probably connect it all up and see what happens. Tell us the make and model of genny and charger. Take some photos of genny, charger, the area where charger is, and where shore power comes in - then upload them here.

 

 

 

That's me, not you! Someone who knows what they are doing might be able to take a look, measure a few things with a multimeter, read a few labels, and either fire it all up, or not. Have you got anybody nearby who could help? Where are you? You could pay a yards electrician for an hour or two of their time and would probably learn a lot. Someone from here might be in the boat next door and be able to help

[dor]

Really, given your admitted level of knowledge, I would not advise doing anything based on what is said in the forum (no disrespect meant to the very knowledgeable people here) because there are so many variables.

 

And fiddling about with 230V on boats is not recommended if you don't really understand electrics. You need someone knowledgeable to come to the boat, see and understand the setup and advise you accordingly. How you determine if that person is genuinely knowledgeable is another pitfall.

 

And don't run your generator anywhere near any doors or windows (CO).

[Richard10002]

Really, given your admitted level of knowledge, I would not advise doing anything based on what is said in the forum (no disrespect meant to the very knowledgeable people here) because there are so many variables.

 

And fiddling about with 230V on boats is not recommended if you don't really understand electrics. You need someone knowledgeable to come to the boat, see and understand the setup and advise you accordingly. How you determine if that person is genuinely knowledgeable is another pitfall.

 

And don't run your generator anywhere near any doors or windows (CO).

Agreed!

[onionbargee]

if it's a 2 stroke Chinese geny like this DO NOT UNDER ANY CIRCUMSTANCES CONNECT IT TO ANYTHING ELECTRONIC. ( the sine wave resembles a map of the Alps)

Edited August 16, 2013 by onionbargee

[Ricco1]

I've been to the boat today. I think I know the answer to my question now. This is what I did:

 

First, I looked at the charger on board. It's 20 amps. I switched it on. I then fired up the generator and connected to the shoreline socket. I have a reading lamp plugged into the 230 v so tried switching that on. It worked although there was a split-second delay before it came on. So I guess that proves that the generator works, at least to some degree. I can't tell if the generator is charging the batteries. One of two leds came on on the charger, but that's all I know.

 

To complicate this a little my boat only has a small engine. It's a Vetus 11hp. I don't know the size of the alternator, it's not stated on it, but I can probably find out by researching this. The guy who helped me reckoned it wasn't a very powerful one though. I have one leisure battery at the moment but I've decided to increase this to two. I don't mind running the engine/ generator to produce my limited requirement for electricity but obviously I don't want this to be excessive. Without going into things in too much detail (I understand very little) do you think I might be best served having a second alternator fitted, solar panels, both? Thanks.

[Ricco1]

I've just googled it, not 100% certain it's the right engine but it's Vetus, 2 cylinder 11HP so very likely to be the one. The alternator is apparently 75 amps according to the data sheet.

[blodger]

Yes. 100/200 watts of solar would obviate a lot of genny/engine running.

 

I would also double the battery capacity by adding a matching battery so as to operate only at high 'State Of Charge' levels

[Guest]

Last time I looked, Vetus do not recommend running their engines out of gear for long periods at tickover, for charging purposes.

 

I have used a 650W Yamaha genny with a Sterling 30A charger to good effect for over twelve years. The genny can power the fridge freezer alongside the charger without problems. The secret with using a small genny is not to let the batteries get heavily discharged, but if they do a few minutes with the main engine will give them an initial boost.

[junior]

I'm a real fan of solar, we've enough to keep us self sufficient from about April-September without having to run the engine to charge, and it's great.

 

 

 

Do you mind me asking how much solar you have?

[Arthur Brown]

The biggest issue with small generators is that they are usually petrol or two stroke check carefully. Storage of petrol as a fuel takes special care, possibly a second gas locker to let possible fumes vent downwards and outside.

 

Yes a 850w generator will provide plenty of power to run a fair charger. Once the peak charging rte has subsided perhaps a second charger in case the starter motor needs help too. There is nothing that kills cruising like both batteries being flat so the engine will not start to recharge your batteries.

 

Asking an 11hp motor to run a rally big alternator and drive the boat may be too much, start off being satisfied with the hardware that you have.

[MtB]

Aren't we missing something basic here? The OP says he has a genny. All the gennys I've ever owned have a 12v output specifically for charging batteries, and this works just fine for me, for emergency charging a flattened battery.

 

MtB

[Arthur Brown]

Most generators i'ev seen have a 12v output for "charging batteries" too, BUT the maximum I've ever seen was 12v 8a as this will be a peak rating into a flat battery it will be putting less into a part charged battery and less than 8A is almost a waste of time if you are burning petrol and hoping to charge a 100AH starter battery or a 400AH house stack.

A 800w generator will run a 20 or 30a charger or the 12v output will supply less than 8a it's a choice but a poor one.