sorry - another generator question

[Mandy]

I am a generator virgin and so know nothing! I have searched this site for an answer to my question but can't find or understand one! What size generator would I need if all I really want to do is keep my 5 batteries charged while living on the cut?

[bottle]

One big enough to run the charger that is big enough to charge the batteries.

 

A bit flippant but true, the charger should be of the type that is three or four stage (some argument discussion as to whether four stages exist ). An ordinary 'car battery charger' will not do.

 

Now I could be wrong here but someone will confirm ot not the charger needs to be rated at approximately 10% of the battery bank.

 

The actual 'load' of the charger will be greater.

 

If you know the size of your battery bank then the true experts can give a better guideline.

[Mandy]

One big enough to run the charger that is big enough to charge the batteries.

 

A bit flippant but true, the charger should be of the type that is three or four stage (some argument discussion as to whether four stages exist ). An ordinary 'car battery charger' will not do.

 

Now I could be wrong here but someone will confirm ot not the charger needs to be rated at approximately 10% of the battery bank.

 

The actual 'load' of the charger will be greater.

 

If you know the size of your battery bank then the true experts can give a better guideline.

charger...3 or 4 stage...rated at 10%...Sorry, when I said I was a generator virgin I meant it - I have no idea what you are saying! I have 5 plus 1 batteries. Up to now I have lived in a marina and so have had a landline, but I may be moving soon to an on line mooring without electricity and am worried about keeping my batteries charged.

[churchward]

Do you already have a battery charger on board that runs from the land line 240V system and how many watts output is this?

 

A 1Kw generator will be able to run a 30amp charger say but not a huge amount of other load. The most popular size of generator for live boards seems to be a 2kw as this leaves lots of power for running other items as well as charging the batteries. Some generators have a direct DC output as well but this generally is not very useful as it will be low ampage and will take an age to charge a large battery bank.

[bottle]

Hi Mandy

 

A generator on its own will not charge a battery, hence you need both.

 

A 3 or 4 stage charger is a type of charger that charges the batteries in 3 or 4 stages, that doesn't help you really and I cannot explain it, I was just making the point that one for car battery charging (as per Half**ds) would not be suitable.

 

If you know your battery sizes (ampHrs, it will say on the label) you can work out the size charger required, for instance if you have a 500 ampHr battery bank you will need a 50 amp charger.

[Justme]

One big enough to run the charger that is big enough to charge the batteries.

 

 

AND to run all the loads at the same time.

 

That way you can charge up & run all the big loads like the washer etc at the same time to reduce the cost of running it.

[johnjo]

How are your batteries charged at the moment?

 

Will running your engine not charge them? as, if so, you would also get hot water while charging, assuming you have a chlorifier.

[nb Innisfree]

I would say a 2KW will comfortably run an 80amp charger continuously which should be ok, you could go to 20% of battery capacity (in your case that would be 110amp if your batts are 5x110ah) or even more, some say up to 45%. We occasionally use our Kipor 2KW sinewave and it takes about 2-3 hrs for a daily charge. If you have the space then a 3KW would give you a bit more margin allowing you to comfortably run a washing machine. The 2kW sinewave is a good compromise IMO as it can be used to run most electrical items. Big gennies to run a W/M and charge batts at the same time would need to be 4KW+ which start to get unwieldy and you can separate w/m and charging times anyway.

[Mandy]

Hi Mandy

 

A generator on its own will not charge a battery, hence you need both.

 

A 3 or 4 stage charger is a type of charger that charges the batteries in 3 or 4 stages, that doesn't help you really and I cannot explain it, I was just making the point that one for car battery charging (as per Half**ds) would not be suitable.

 

If you know your battery sizes (ampHrs, it will say on the label) you can work out the size charger required, for instance if you have a 500 ampHr battery bank you will need a 50 amp charger.

Sorry, I was being particularly thick! Yes, I already have a battery charger. I am not on the boat at present so can't say what wattage it takes. I have been speaking to a boater here and he said that if all I want to do is charge up the batteries, then I only need to spend around £70 on an 850 watt generator. Money is really tight at present, so if that would be enough for my charger, I'm tempted to go with that.

[bottle]

Mandy

 

Do not go with that, maybe money is tight but money well spent on a good generator is well spent, cheap ones do not last long (someone will now pop up and say there cheapo chinese one has lasted).

 

Depending on the charger it is very doubtful that an 850 watt (generator)one will be big enough.

 

I have a 7Kw onboard generator, the boat is all electric but as many on here have said you will probably be looking at 2 to 3Kw depending on your onboard equipment.

 

From previous threads, I have picked up that the Honda is the one to go for, yes expensive but the quality is there.

 

Obviously I do not know the generator that has been recommended but I suspect its noise level will be a lot more than the Honda, another consideration especially if you have neighbours.

 

Edit: thick fingers to go with brain

Edited November 18, 2009 by bottle

[Lady Muck]

I bought a cheap genny (Wolf) from Halfords. It is now dead, only having been used a handful of times.

 

After being nagged and lectured about gennies by our boat engineer, I now have a Honda, Eu20i - not cheap at all. If you know anyone with a Costco card it is worth buying a genny from there, we saved about £100 on the cheapest price I could find online, paid about £800. I noticed last time I was there that they also had some cheap 1kw Chinese gennies for under £100 that would also probably do the job, but no idea how reliable. Alot of boaters swear by Kipor, which seems to be essentially the same as the Honda gennies, but I've no idea how easy it is to get parts /get them serviced, my engineer said this is why he recommends the Honda, it can be properly serviced and repaired (and I think the warranty period is much longer than for cheaper brands).

[g-man]

I am a generator virgin and so know nothing! I have searched this site for an answer to my question but can't find or understand one! What size generator would I need if all I really want to do is keep my 5 batteries charged while living on the cut?

 

From my experience a 1KW generator will just about charge 5 batteries whilst running an inverter with a few lights on etc. However if you can afford it get at least 2KW as it'll be more comfortable running equipment like a washing machine and vacuum cleaner.

 

I tend to think of my gennie more as backup to the engine, OK the gennie uses less fuel maybe 1/2 to 3/4L per hour against 1.4L per hour but red diesel is also cheaper than petrol and the engine heats up the water as a bonus. Swings and roundabouts

[Mandy]

From my experience a 1KW generator will just about charge 5 batteries whilst running an inverter with a few lights on etc. However if you can afford it get at least 2KW as it'll be more comfortable running equipment like a washing machine and vacuum cleaner.

 

I tend to think of my gennie more as backup to the engine, OK the gennie uses less fuel maybe 1/2 to 3/4L per hour against 1.4L per hour but red diesel is also cheaper than petrol and the engine heats up the water as a bonus. Swings and roundabouts

Really good point. I've been trying to work out whether it is more expensive to feed the engine or the generator, so your comments are helpful. Someone today pointed out that it costs £4,000 or so to replace an engine but only a couple of hundred to replace a gennie, so I'm still not sure what I'll do!

Oh and last question - will an 850 watt generator power a 30 amp charger?

Edited November 19, 2009 by Mandy

[WotEver]

Oh and last question - will an 850 watt generator power a 30 amp charger?

Yes, but a 30A charger is really too small.

[smileypete]

Really good point. I've been trying to work out whether it is more expensive to feed the engine or the generator, so your comments are helpful. Someone today pointed out that it costs £4,000 or so to replace an engine but only a couple of hundred to replace a gennie, so I'm still not sure what I'll do!

Oh and last question - will an 850 watt generator power a 30 amp charger?

Hi,

 

Should do, if it's only running the charger and nothing else at the same time.

 

B&Q have a cheapo genny for £50 (clicky)

 

Might be worth doing a 'power budget' of what you'll use.

 

A small genny and charger will only cover use of a few lights, pumps, and an hour or two on the lappy.

 

If you're running a mains electric fridge or high power items on an inverter, a bigger genny and charger will almost certainly be needed.

 

May be worth investing in some LED lights for places where lights are on longest.

 

cheers,

Pete.

Edited November 19, 2009 by smileypete

[NBMike]

I bought a cheap genny (Wolf) from Halfords. It is now dead, only having been used a handful of times.

 

After being nagged and lectured about gennies by our boat engineer, I now have a Honda, Eu20i - not cheap at all. If you know anyone with a Costco card it is worth buying a genny from there, we saved about £100 on the cheapest price I could find online, paid about £800. I noticed last time I was there that they also had some cheap 1kw Chinese gennies for under £100 that would also probably do the job, but no idea how reliable. Alot of boaters swear by Kipor, which seems to be essentially the same as the Honda gennies, but I've no idea how easy it is to get parts /get them serviced, my engineer said this is why he recommends the Honda, it can be properly serviced and repaired (and I think the warranty period is much longer than for cheaper brands).

And Costco have an excellent reputation with any problems with your purchase. They give you your money back - no quibble!

[david and julie]

And Costco have an excellent reputation with any problems with your purchase. They give you your money back - no quibble!

 

Costco are fantastic if you want to return something or have a problem, the only issue I have with them - which is not their fault - is that I invariably get sidetracked and the single item I went there for ends up a couple of hundred quid more.

[Mandy]

Yes, but a 30A charger is really too small.

That's what I've had on the boat since I bought it and haven't had any troubles yet - although of course mostly I've either been on mains or been cruising, so I may find it too small in the future. But then I don't run anything like washing machines or freezers.

[Lady Muck]

And Costco have an excellent reputation with any problems with your purchase. They give you your money back - no quibble!

 

That's good to know, we've only had the card since Easter, but I now take the boat close by there every month, to stock up on cheap Rioja! Last summer they had excellent two-man canoes for £300. I'm going to get one in the spring.

[Proper Job]

Yes, but a 30A charger is really too small.

A 30 amp charger isn't to small. It will just take longer to put the same amount of charge in.

 

I have a Stirling 40 amp multi stage charger that runs via a Honda EU20i.

 

When running at such a low load, the genny is very quiet.

 

An 850W genny will be noisy as it will be running at a good load. Cheap genny's don't usually have much in the way of silencing either, so you had better have forgiving neighbours.

[WotEver]

A 30 amp charger isn't to small. It will just take longer to put the same amount of charge in.

Which is exactly what I meant by too small. OP is used to being on hook-up, so if the charger took 12 hours to fully charge the batteries, so what? I don't think she'd want to be running a genny for those kinds of durations.

[NBMike]

That's good to know, we've only had the card since Easter, but I now take the boat close by there every month, to stock up on cheap Rioja! Last summer they had excellent two-man canoes for £300. I'm going to get one in the spring.

When I was building my boat I bought one of their car ports to be able to weld in the rain. My mate used to borrow it each June (Only 2 of them) as a prizegiving tent for his amatuer footie club. It came back the last time with a load of bits missing. I asked Costco how much it would cost to replace the missing bits and was told - we don't do 'parts' bring it back for a refund. This was after 2 years of very hard use. I also took back a car battery with a dead cell after 18 months - full refund!

Well worth the membership fee.

Mike

[Guest]

Hi Mandy

 

Whilst you may elect to buy a cheep genny as a quick solution, in the long run you should consider taking a more scientific approach.

"Living aboard" against "Summer cruising" place different burdens on your system, as I have recently discovered!!

You will after all be depending on those batteries every day!! Failure to properly charge will result in premature failure!

 

First you will not be able to make an informed decision unless you know what power you are using (As mentioned by SmileyPete).

The size of the battery bank is less significant.

(If you only use 10% of the Amp Hour (Ah) capacity, then you only need to replace this 10% when you charge.)

 

An energy audit is a bit of a tedious process, but eventually will be well worth the effort.

Basically you need to list every item, its power consumption and how long you use it for on average.

I can send you a spread sheet which does all the calculations and has sample numbers in it, which you are welcome to use.

(As also hinted on this thread swapping lights for LEDs may also end up on your "To Do" list!)

 

Then you will know how much charge you need to replace.

With wet cells you can generally charge up to the capacity / 8 (Or about 10% as others have said.)

However lower charge (and discharge) rates should improve the life of the batteries.

You can charge faster, but doing this regularly is pretty much guaranteed to reduce the battery life.

 

At a guess you have 5 x 110 Ah = 550Ah So MAX charge rate is just over 60A

Very roughly this equates to about 1.2Kw from a generator for a modern switch mode charger.

(Your 30A charger will be taking about 600W)

Word of caution. Cheaper generators may well not give anything like their rated power when driving a modern (Switch mode or "Digital") charger.

The Honda units are very good (and quiet!) (Other electronic generators are available!!)

 

As an aside what I tend to do is run the engine for half an hour or so, to heat water and put some charge into batteries.

I then run the generator / charger to finish the job, as the charger is better than my engine / alternator set-up.

[nb Innisfree]

Then you will know how much charge you need to replace.

With wet cells you can generally charge up to the capacity / 8 (Or about 10% as others have said.)

However lower charge (and discharge) rates should improve the life of the batteries.

You can charge faster, but doing this regularly is pretty much guaranteed to reduce the battery life.

 

At a guess you have 5 x 110 Ah = 550Ah So MAX charge rate is just over 60A

 

Though 10% charge rate is often quoted it can be exceeded, the 1 amp per 1% of battery capacity is sometimes quoted, i.e. for a 50% SOC 100ah battery then 50 amps charge can be put in, 80% SOC then 20 amps and so on. Though this will reduce battery life it needs to be considered against engine wear and fuel usage.