using my generator

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Lunasea

Veteran Member
Joined
Jan 1, 2014
Messages
38
Location
America
Vessel Name
Fishbone
Vessel Make
1990 Nova/ sedan
*a couple of questions?

Planning to anchor out, so I disconnected power and operated on bank one (I have 2 banks and can select both or either) as if I was anchored.

the boat has an original analog meter that doesn't show much deflection between 12 and 13 volts, someone installed a digital meter but it floats between 12.2 and 12.8 when I am on battery only so I cannot rely on it.

so I am not sure when to start my generator

I went 8 hrs then started the generator and it shows a load, charging at 14+volts.

I am currently*using bank 1, should I be charging on both banks anyway?

I don't think the generator will unload when the batteries are full, so how do I know when to stop charging?

its not easy being a newbie

I appreciate any comments you may have,

thanks
 
For me, battery charging is something I do when I run the genset for some other purpose. Like running some 240v appliances,running the eutectic fridge compressor,for hot water etc. Generators are best run loaded, I doubt battery charging is enough load, you risk glazing the cylinder bores. Mine often gets run early morning/late afternoon.
The generator is sending amps to a battery charger which will sense when the batts are full, it`s easy to get them to about 80%, the last 20% takes a long while. The reduced charge will reduce the load on the genset. You may as well charge both banks, especially if the charger has 2 bank charging.If those batts are flooded types you can top up, check them regularly if using the charger, you`ll soon get how much water they use.
It`s a crude method, but 12.6v or above, without any charge input, is effectively full. There are State of Charge (SOC) meters. You could also use a multimeter to take the voltage at the batts, but allow time,?1/2 hour, after charging. A load tester you can get cheaply on ebay, will help too.
Fortunately there are others much more knowledgeable about electrics who will come to your help.
 
I wanted to maintain minimal electrical dependence by not having electrical stove, electrical air conditioner, electrical heat, and other electrical draws, but the half-sized refrigerator is an exception as well as navigational devices.. Decided to duck the cost (acquisition dollars, space, and maintenance of a generator. So I'm dependent on the engine's alternator and marinas' electrical hook-ups to recharge home batteries. Fortunately, my boating waters are in a temperate zone.
 
Using 2 batt banks for the house is no longer considered good practice, as the larger combined bank suffers less from the electrical draw.

Using a rotary switch to combine the house and start banks for an emergency start is still good practice .

With one alt the start and house are combined , after engine start with a solenoid or an electric gadget.

A SOC meter is the only way to know State of Charge and keep the house batts happy.
 
You should designate one bank as your house bank and only use that one to power lights and other appliances at anchor. Even better would be to replace that battery with either a large Group 31 AGM or a pair of 6V golf cart batteries wired in series.

What kind of charger do you have, how many amps?

You say your digital meter fluctuates between 12.2 and 12.8. That may be entirely normal and correct. 12.8 indicates a well charged battery. The voltage can drop a half volt when DC appliances are turned on which loads the battery and pulls down the voltage a bit. The voltage will recover when the loads are removed. A bigger battery bank as discussed above will dampen that out a bit.

Batteries don't need to be recharged until the resting, ie no load and no charging, voltage drops below 12.0. That is a crude indicator of 50% discharge. A real SOC meter like Balmar's, Xantrex or others will do a better job of monitoring SOC.

I operate my genset like Bruce described above. I run it for about 20 minutes in the morning for coffee and about 30-45 minutes at night for hot water. That is sufficient to keep the batteries charged with a 100 amp charger. I have never run it just to charge batteries. Unless you have unusually high DC loads you probably don't need to either

David
 
A couple of questions for the OP
What is the size of your Charger, generator, and battery banks?
Is your charger wired to charge both banks independent of Batt seletor switch position?
Are all batteries the same type?

Some points:
Sitting at anchor on BOTH combines the banks and each battery is discharged less between charges. This should make your batteries live longer assuming they are the same age and type. Its important that you have a separate Gen start battery lest you run the bank down and cannot start the gen or main engine.
Running the generator to power a small (<50 Amp) charger is running the gen lightly loaded and could cause problems. Search the TF for "glaze" or "glazing".
A fully charged lead acid battery is 12.78 volts with no load and no charger. A completely dead battery is about 11.8 volts. So it is VERY important to take voltage readings with no load or charger.
 
Lunasea said:
*a couple of questions?

Planning to anchor out, so I disconnected power and operated on bank one (I have 2 banks and can select both or either) as if I was anchored.

the boat has an original analog meter that doesn't show much deflection between 12 and 13 volts, someone installed a digital meter but it floats between 12.2 and 12.8 when I am on battery only so I cannot rely on it.

so I am not sure when to start my generator

I went 8 hrs then started the generator and it shows a load, charging at 14+volts.

I am currently*using bank 1, should I be charging on both banks anyway?

I don't think the generator will unload when the batteries are full, so how do I know when to stop charging?
Click to expand...


Depends maybe a bit on what you mean by "floats between 12.2 and 12.8"...

If you mean it gradually declines from around 12.8V when you think the batteries are probably fully charged... down to about 12.2V eventually... then that gauge may be enough to give you the clues you need. Run the genset and charge the batteries when you see 12.2V (or thereabouts) on your digital gauge. Then you can stop charging when you see 12.6V or better... or at least sufficient voltage to run for a while, if you get tired of listening to the generator.

(We charge morning and evening at anchor, every day, though... but mostly because we need the genset to do other stuff too: electric cooking, heating water, etc.)

OTOH, if you mean the gauge bounces around all the time mostly between those two voltages, maybe use a handheld mutlimeter to see if the gauge needs replacing, or if there's something about your system that needs some additional attention. (If the multimeter "bounces" too... maybe there's another issue.)

If your charger(s) is (are) set to charge when the genset is on, I'd guess the set-up charges both banks at the same time. The battery banks will each accept as much charge as they can accept.

Eventually you might want to learn more about your DC systems: what exact batteries, how many in each bank, what charger(s), etc. The boat may not have been optimized for longer-term anchoring, and if so, you could read some of the battery/charger threads about how to beef up your system for that.

-Chris
 
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wow, a lot to digest over night.
I have 2 banks with 2 8D and 1 4D batteries each. I have a blue sea 40 amp battery charger for the 2 banks. It was installed when I purchased the boat earlier this year, as the other one had failed. I questioned the installer if this was the best lay out for the batteries and he assured me it was, but I thought that I should have the 8Ds as the house bank and the 4Ds as the start?

The fluctuation in voltage would go up and down over about a half hour, it would drop to 12.2 and later be back to 12.6.

when I started the generator, the battery charger didn't come on, so I assumed that the generator was charging the batteries directly?
 
Lunasea said:
I have 2 banks with 2 8D and 1 4D batteries each.

I have a blue sea 40 amp battery charger for the 2 banks.

The fluctuation in voltage would go up and down over about a half hour, it would drop to 12.2 and later be back to 12.6.

when I started the generator, the battery charger didn't come on, so I assumed that the generator was charging the batteries directly?
Click to expand...


Hmmm... mixing batteries within a bank (e.g., two 8Ds and a 4D) is generally not recommended.

Is this maybe a twin engine boat? Is it remotely possible the 4Ds are not actually connected to the 8Ds? Maybe 4Ds connected to each engine, and maybe only charged by each engines alternator? Just a thought...

A single 40-amp charger probably can be sufficient, but could also bear some examination depending on how often/long you might intend to anchor out at any given time. Wouldn't speculate about that just now, although you could maybe in the meantime read some threads about battery charging, acceptance rates, etc.

That meter fluctuation over that short a period suggests hosed meter or something else in the system might need attention. Perhaps try the multimeter test right at the batteries (unloaded), then try the multimeter test at the built-in meter connections (also unloaded). Outcome of that testing could instruct... but could also be something as "simple" as a loose connection somewhere...

If the charger didn't come on... might just be a breaker than needs activating? Does the charger automatically start charging when you're on shorepower? Could be a generator's alternator is charging something directly, but I'd guess that would likely only be the generator's own start battery, if there is one...

-Chris
 
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I asked similar questions 4 years ago and was directed to review Nigel Calder’s Boat Owner’s Mechanical and Electrical Manual. It was good advice. It takes a while for all of this to sink in but pay special attention to comments about “Partial” or “Incomplete Charging” of deep cycle batteries which occurs with use of generators over longterm anchoring.

Jim
 
"Hmmm... mixing batteries within a bank (e.g., two 8Ds and a 4D) is generally not recommended."

The size of the batts 8D -4D is never a problem.

Mixing the style , start -deep cycle , AGM - WLA can lead to problems.

The batts size 8D , 24,27,31 is like a shoe size , just what fits where .
 
I've been resisting responding to this thread, but here goes. If you have 4 8d's and 2 4d's then you have at least 1000 Amp hours of battery capacity. A 40 amp charger is very small for this amount of battery capacity. It will certainly charge your batteries, but it will take a lot of time to do it unless they are not very low. Generally, for flooded lead/acid batteries, a charger that has an output equal to 10-15% of the AH capacity is normal and will result in more reasonable charge times.

All that said, nobody can give you accurate advice without knowing exactly how your battery banks are set up with respect to your charger and engine(s) alternator(s). Also, it would be very helpful to know if there is a display panel from your charger to indicate the charger's state as its running? Except for "Resting" battery voltage, the battery voltage seen during use and charging (taken ALONE) does not give very accurate information about the state of charge of the batteries.

You or somebody will need to figure out what is connected to what and how the batteries are connected to each other and/or the engines. With that data, there are lots of people on this forum who can give you very sound advice as to how to use and charge your batteries.

Ken
 
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Would I be incorrect in also pointing out that the wiring to the voltmeter could be part of the 'problem?' Depending on where it is in the circuit and the size and quality of wiring, some items coming on and off line could be causing voltage drop seen at the meter?

Just another example of the unknowns here.
 
chriscritchett said:
Would I be incorrect in also pointing out that the wiring to the voltmeter could be part of the 'problem?' Depending on where it is in the circuit and the size and quality of wiring, some items coming on and off line could be causing voltage drop seen at the meter?

Just another example of the unknowns here.
Click to expand...

It could be exactly that, for example if a very heavy load came on, like somebody using a microwave through an inverter, it might actually be normal to see a temporary voltage drop. But again, not enough data yet.
 
Would I be incorrect in also pointing out that the wiring to the voltmeter could be part of the 'problem?'

Possible but doubtful. There is minuscule current flow through the voltmeter wiring itself.

Depending on where it is in the circuit and the size and quality of wiring, some items coming on and off line could be causing voltage drop seen at the meter?

Yes, exactly. Normal connections in the heavier wire to the loads would cause voltage fluctuation seen by the voltmeter depending where the higher resistances are in the circuit. The worse the connection or higher the current flow, the bigger the voltage drop or fluctuations. When you are only working with 12 volts, it does not take much.

Just another example of the unknowns here.
 
thanks for all the input, I am going to bring in an electrician to sort it all out for me and set me straight. I will let you know how it all plays out.


thanks
 
Before calling for help read one of the N.Calder books on boat electrical systems , so you will know what you want , after you decide what you need the system to do,
 
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