When to stop charging with generator?

[duggybuggy]

I have a portable generator. As well as 240v outlet, it has a 12v outlet with a lead, and I use this 12v outlet to charge my battery. My understanding is that it supplies this voltage at a current of 8 amps.

I know this isn't much, 8 amps, but I don't need a lot, and my 230ah battery will probably only accept a fairly low charge current anyway because it is never allowed to get very discharged.

But I want to keep it charged to the brim to keep it in good condition, and being charged to the top I will then be able to equalize it every six weeks, which I can only do if it is fully charged.

The solar panels are good for this because they can slowly take the battery to 100%, as the last bit to the top will be only at a dribble because the battery will only accept a dribble when it is near the top. It wouldn't be worth me running the generator to get that last bit to 100%.

So what I would like is to know:

a) when I am using the generator to charge, how many amps is the battery accepting as I do this.

b) If the battery only will accept say 2 amps at a particular time, then maybe the generator supplying at 8 amps might not be good for the battery and could damage/age the plates.

I did have a battery charger with a current readout, a needle indicator, but this went dickie and then stopped working.

I would buy another charger, and would welcome any advice on this, perhaps recommend a model.

Or maybe I don't need to buy another battery charger and can continue with the generator's 12v 8amp output if the 8 amps will not harm the battery, and if I can use my multimeter to find out hoe many amps the battery is taking in.

What do you reckon? What do you think i should do? I need to know when it was not worth running the generator.

I have a supply unit which i can set the amps and the voltage, and there is a digital readout for both volts and amps. This is what I will use to equalize the battery ( I set the voltage to 15.7 volts and the current to 3 amps. Then I clip it to the battery and what the read out slowly climb to my set voltage and then hold it at that for 4 hours).

So maybe I could use this power supply unit as my charger, and use my multimeter to know what is going on with the amps supplied and being accepted.

[Pete7]

Originally Posted by duggybuggy

I have a supply unit which i can set the amps and the voltage, and there is a digital readout for both volts and amps. This is what I will use to equalize the battery ( I set the voltage to 15.7 volts and the current to 3 amps. Then I clip it to the battery and what the read out slowly climb to my set voltage and then hold it at that for 4 hours).

I was following this until the last part, what is this supply unit?. 15.7v is very high for charging batteries and they will need topping up frequently if you do. Might be better to charge at 14.6-14.8v depending on your battery type. Have a read of the table on page 2:

https://cdn.shopify.com/s/files/1/06...22295855460459

Using the 12v circuit on the generator to charge batteries is hopeless. Use the 240/110 circuit to run a decent charger and you will drastically shorten the charging times. When to stop charging is up to you but I used to get fed up waiting when the current dropped to single figures. I now use solar instead.

Pete

[denverd0n]

Originally Posted by Pete7

Using the 12v circuit on the generator to charge batteries is hopeless. Use the 240/110 circuit to run a decent charger and you will drastically shorten the charging times.

This ^^^^^

A good charger run off of an AC circuit on your generator will almost always be a better way to charge the batteries.

[a64pilot]

Get a charger, run the generator until the battery acceptance rate is what the solar is making, then turn off the generator, finish charging with Solar, of course this means early morning generator runs, not late in the day.
A battery will only accept the correct current rate as long as voltage is correct, so if you had a 100 amp charger, you will not overcharge or harm the battery.
The little 8 amp charger it is unknown voltage, is not a three stage charger, it not adjustable for your battery chemistry and is honestly next to useless compared to a real charger.

[sailorboy1]

The answer for me is that once you learn what your solar will do in a day, with what the conditions are looking like for the day, that you run your generator in the morning till you get the battery to the condition that the solar for the day is going to result in what you want to get to that day.

[adlib2]

'I would buy another charger, and would welcome any advice on this, perhaps recommend a model.'

I've had a few chargers over the years and for the past 6 years have used a Sterling 50 amp 4 stage charger and am very satisfied with it compared to others.

[Maka]

Good question. Good reply's.

[newhaul]

Get and use a good ac battery charger off your genny to bring the batteries up to about 80% in the morning and polish them off with solar for the rest of the day.
I would have to recomend caution using the dc tap on the genny most of them are un regulated and.can fry a battery in fairly short order.

[SouthernPride]

Wouldn't hurt to run it down to single digits once a month or two. You will get a reall good idea of how long it will last if you run into charging limitations and will recalibrate the battery cells.

Another thing to consider and do if you are concerned about longevity is move the battery to the coldest spot possible. A cool battery is a happy battery.

[Dave22q]

You are either sophisticated in electricity or not. If not, get your self a smart (4 stage) charger sized for you battery bank. You are not going to learn enough to select the right charger here. Find a good marine electrician and follow his advice. DIY is not smart strategy when the risks are high.

[BruceS]

I recommend to also carry a cheap "dumb" charger in case you find your batteries REALLY flat one day. A lot of smart chargers won't start charging until they "see" a battery. (over 11V or something)
20a or 40a ones are pretty cheap.... brand Misto I think they are?

[Pete7]

Originally Posted by Dave22q

You are either sophisticated in electricity or not. If not, get your self a smart (4 stage) charger sized for you battery bank.

Agreed.

Originally Posted by Dave22q

You are not going to learn enough to select the right charger here. Find a good marine electrician and follow his advice.

Really? he has a single 230 amp battery, how difficult can it be? Spending a few hours reading CF about batteries and asking questions will do just nicely with free advice from people who have been there and got the t shirt. One of the really great things about CF, so many people willingly giving up there free time to help others for no other reward than an occasional thank you.

Originally Posted by Dave22q

DIY is not smart strategy when the risks are high.

What risk?

Pete

[duggybuggy]

Cheers everyone. I am going to get a sterling four stage charger, wack it on in the morning and then polish off with solar.

This charger shows the amps and volts, so I should be able to understand a bit more about what is happening.

Pete, that unit is a lavolta variable DC bench power supply unit BPS305.

Dave, you are right that the risk is high.......The TV is my lifeline.

Thanks for all your help. I'm happy again........£300 lighter......But happy......☺. Cheers....And all the breast for the new year.

[Dockhead]

Originally Posted by duggybuggy

Cheers everyone. I am going to get a sterling four stage charger, wack it on in the morning and then polish off with solar.

This charger shows the amps and volts, so I should be able to understand a bit more about what is happening.

Pete, that unit is a lavolta variable DC bench power supply unit BPS305.

Dave, you are right that the risk is high.......The TV is my lifeline.

Thanks for all your help. I'm happy again........£300 lighter......But happy......☺. Cheers....And all the breast for the new year.

Excellent plan

As to sizing it -- from 20% to 25% of battery capacity in A/H is optimal provided you don't exceed about 80% of the generator s capacity. Sizing it right is important.

Sent from my D6633 using Cruisers Sailing Forum mobile app

[Hobbitt]

Bingo, newhaul.

Nearly every 110 volt utility generator has some provisions for supplying 12 ir 24 volts DC, But it is important to remember that these generators were built to provide something near normal 110 volts and 60 cycles. The simple design of a rotating generator armature does that well and provides an almost perfect sine wave similar to the power company. As opposed to this relatively clean power, a DC to AC inverter that we are all familiar with, generally provides a relatively trashy modified sine wave which started in the electronica as a pulsed square wave bug became distorted by the very nature of the electrical used.

As a byproduct of generating the AC voltage, they tap off something that can be converted to around 12 volts of DC. But because this is more of an advertising gimmick rather than a serious production of DC power, these 12/24 volt taps usually do not have much regulation. The 12 volts us simply 1/10th of the 120 volts of AC. They suck off 24 volts and then cut it in half to get the DC at the correct 12 volts. Sadly, this DC is far from pure because it pulses 60 times a second and, again, the sloppy tolerances of the generator components really serve to help clean up the pulses. But any control of the voltage to provide 12 v DC at whatever the advertised amps are is only a rough guess at what the average MIGHT be.

Why is this all important? As many have pointed out, the amount of voltage is really what controls the charging action of the battery. we all know that 15.5 volts will charge a battery faster than 14.5 volts....no matter what the rated amperage of the charging system is. The voltage regulator, if any, is like the very old generator regulators on cars. A couple of electrical coils in the regulator open and close as the voltage of the generator changes. When the voltage is low the voltage coil closes its circuit and allows electricity to pass through the regulator to the battery. As the voltage gets higher than it has been set... the coil opens and the circuit breaks any electrical connection to the battery. In a similar manner, the current coil is usually closed and stays that way until it senses that the current passing through to the battery is too much, and then the coild opens the circuit and stops all electricity. So basically, this type of regulator gets charging power somewhere in the vicinity of what the user or mechanic wants. But it is really not controlling anything very scientifically. The problem is that this is the way that it has been done for 50 years. We know better as witnessed by some of the amazing electronically controlled 4 stage chargers that are constantly querying the battery condition to decide how to set the appropriate voltage and limit the current. What is so alarming to hear some of these comments is that few people understand that the 12 volt DC outlet from most home generators...lacks even the poor controls of the old car regulators.

A boat owner needs only to go and purchase a new heavy duty deep discharge house battery and they will soon realize what a good quality represents from a strictly financial point of view. Regardless of what kind of boat you have or how you generate the battery charging electricity, we have to respect how hard we work our batteries on a daily basis and how much more we depend on them to be there when we need them.

Good luck.