Charging my batteries via small generator

[pcatterall]

We are planning a fairly long passage and expect to have little opportunity for topping up via shore power so need to consider our battery charging (Having been marina softies to date).
On my last boat I had a small 'emergency' cheapo genny 600watt type which would power drills and such. I used it to charge batteries now and then but via the DC charge bit and it was predictably slow to charge ( around 4/5 amps I think)
I am considering getting another similar genny and assume that I can use it to power my 20watt basic mains charger, what sort of charge might I expect from this arrangement?

We are considering what we need by way of more 'sustainable' power and thinking around the 100watt solar panel size. But in the short term I thought the genny route would help and the genny is always a useful item to have to hand.
Grateful for your advice.
PS will my basic charger be upset by incorrect 'waveforms' or whatever from the Genny?

 

[sailorman]

We are planning a fairly long passage and expect to have little opportunity for topping up via shore power so need to consider our battery charging (Having been marina softies to date).
On my last boat I had a small 'emergency' cheapo genny 600watt type which would power drills and such. I used it to charge batteries now and then but via the DC charge bit and it was predictably slow to charge ( around 4/5 amps I think)
I am considering getting another similar genny and assume that I can use it to power my 20watt basic mains charger, what sort of charge might I expect from this arrangement?

We are considering what we need by way of more 'sustainable' power and thinking around the 100watt solar panel size. But in the short term I thought the genny route would help and the genny is always a useful item to have to hand.
Grateful for your advice.
PS will my basic charger be upset by incorrect 'waveforms' or whatever from the Genny?

i was virtually given a new in box 850watt genny last w/e from a very nice forumite. i started it for its very first time & connected to the batt charger the charger was putting in 15amps

 

[Mistroma]

....I am considering getting another similar genny and assume that I can use it to power my 20watt basic mains charger, what sort of charge might I expect from this arrangement?
....
PS will my basic charger be upset by incorrect 'waveforms' or whatever from the Genny?

I assume that you meant 20A charger and not 20W. I imagine that a 600W genny would be able to power a 20A charger. I still have my old Yamaha EF600 which I bought many years ago and it worked on my last boat with a 20A marine charger.

20A at around 12.8V is 256W but charger won't be 100% efficient so probably needs 300W.
A 600W genny will probably be rated at only 400W continous but perfectly fine for 300W.

I've heard that some chargers are picky about waveforms but also heard that some are specifically designed to accept poor waveform AC. So I guess that a lot depends on the charger that you have but 600W genny should be fine (but little capacity left over).

I think that my EF600 could be used with both DC and AC feeding a charger at same time. Other generators would probably allow this as well. But I seem to remember that the usable AC output was reduced so total A to battery might not be increased by much.

 

[William_H]

Battery charging

The problem of battery charging is that you need lots of volts to push big amps into a battery. ie 15+ for 20 or 30 amps that you want to charge at. This explains why a 12v output will not charge much current although it might provide 12v power at high current. It means you need a battery charger to provide the higher voltage. Will your charger be efficient on bad AC waveform is a question. I don't know but you need to find out. Or go for solar and a good charge controller on the engine alternator. In any case fit an amp meter so you know how much is going into batteries. good luck olewill

 

[pcatterall]

Thanks guys, good advice as always!
Thanks OW for the explanation about the poor charging from the dc side. I may look for a cheapo 850 rather than 600.

 

[cliffdale]

I used to have a Honda 1000w suitcase generator. It struggled to run the on board battery charger. It would cut out several times particularly when you first switch the charger on. The initial draw was more than the honda could give.

I upgraded to a 2000w and this works fine.

If you are planning a long passage, I would go for a 2000w genny.

I'm in the same position as you, planning a long passage.

I have 500Ah of batteries, 2000w petrol genny and will be fitting 100w solar panel.

The solar panel will not be enough to keep batteried topped up but I have 2 back ups, genny and diesel engine.

Cliff

 

[Jabs]

Have you considered an uprated alternator on your engine?

It is relatively easy to add, say, a 120 amp generator but a 120amp charger would be a beast.

Running the engine every few days also benefits the engine.

Work out your daily power budget and decide from there what you need in terms of charging.

120 amp hours per day would be a lot and running your engine for say 75 minutes would do it.

Tony.

 

[charles_reed]

I'd suggest to anyone, that the best approach is to analyse the problem rather than try any number of solutions.

The start is to work out your daily usage - mine is the equivalent of 80ah/day under way, 60ah at anchor - most of that being the computer and fridge.

I've got 316watts of solar panel, a 120amp alternator, feeding 330ah of battery through a smart controller and an MPPT controller.

At anchor @ about 36N @ midsummer, I can go 8 days on 2/3rds of the total battery capacity, before system volts drop to 12.2 @ rest. It takes about 4 hrs of engine running or 24hrs of shorepower through a 20 amp charger to fully recharge the batteries.

I use the cheapest flooded lead-acid batteries I can find which do me 5-10 years between replacements (cost about €0.85/ah).

From those observations I feel most posters are at risk of gravely under-rating their power requirements.

 

[TQA]

Have you considered an uprated alternator on your engine?

It is relatively easy to add, say, a 120 amp generator but a 120amp charger would be a beast.

Running the engine every few days also benefits the engine.

Work out your daily power budget and decide from there what you need in terms of charging.

120 amp hours per day would be a lot and running your engine for say 75 minutes would do it.

Tony.

Be aware that a typical 3/8th / 10mm belt will struggle if the alternator is giving 120 amps or anything close. You really need a twin belt system or one of these new flat multigroove belts.

 

[William_H]

Have you considered an uprated alternator on your engine?

It is relatively easy to add, say, a 120 amp generator but a 120amp charger would be a beast.

Running the engine every few days also benefits the engine.

Work out your daily power budget and decide from there what you need in terms of charging.

120 amp hours per day would be a lot and running your engine for say 75 minutes would do it.

Tony.

An uprated alternator in itself will probably do nothing for increasing charge rate. You need a smart charge controller to increase the voltage so increase charge current through the charge cycle. And as said a decent belt drive system. good luck olewill