Battery Charger While Running?

[Roger Long]

We have a dead simple and primitive 12 volt system on our twin engine trawler. A 4D start battery for each engine which I keep connected together with the "1-2-Both" switch and use for the house as well. 12 volt loads are just lights and pumps so this has worked well. Both engines start very easily so little starting load.

The generator is entirely separate except for the battery charger on the 110 volt buss. Just once have I found voltage a bit low (on the previous batteries which were nearing the end of their life) and had to run the generator for an hour before starting the engine.

I have been in the habit of turning off the battery charger whenever the engines are running just in case the older "Tru-Charge" 20 amp battery charger doesn't get along with the alternators due to some design or failure mode flaw in either.

Is this silly or even counter productive?

 

[john61ct]

Doesn't matter either way.

If you needed to go to something more sophisticated for House usage, extended camping on the Hook etc there could be a lot of different approaches.

But if your usage remains as is, you're fine.

Personally I'd keep the two Starters isolated from each other except for when one failed.

 

[dhays]

Doesn't matter either way.

If you needed to go to something more sophisticated for House usage, extended camping on the Hook etc there could be a lot of different approaches.

But if your usage remains as is, you're fine.

Personally I'd keep the two Starters isolated from each other except for when one failed.

I may misunderstand, but it sounds to me like he is using those same 2 x 4D batteries as his house bank as well as his start engines. As such, he wouldn’t want to separate the two start batteries as he would drain one of the much more quickly using it as a house battery.

I agree that it sounds like it has been working well for him so far so don’t see a big reason to make a change.

 

[Roger Long]

I so don’t see a big reason to make a change.

But, what about the charging from two sources (my main question)? Should I continue to turn off the battery charger when the engines are running?

I don't see a problem having both alternators and battery charger connected as long as everything is working properly. It just provides more amps for charging. I'm concerned about what happens if either the charger or an alternator fails and power is fed back into it. Is that a significant concern?

 

[dhays]

But, what about the charging from two sources (my main question)? Should I continue to turn off the battery charger when the engines are running?

I don't see a problem having both alternators and battery charger connected as long as everything is working properly. It just provides more amps for charging. I'm concerned about what happens if either the charger or an alternator fails and power is fed back into it. Is that a significant concern?

Sorry Roger. Your question very quickly went beyond my limited understanding. Better to let the folks that actually know answer.

 

[jleonard]

I have used both and never had an issue. I also sometimes use a car battery charger in addition to the boat charger when the genny is running.
(I was told by an AC-Delco battery expert that this was ok to do.)

 

[kchace]

But, what about the charging from two sources (my main question)? Should I continue to turn off the battery charger when the engines are running?

I don't see a problem having both alternators and battery charger connected as long as everything is working properly. It just provides more amps for charging. I'm concerned about what happens if either the charger or an alternator fails and power is fed back into it. Is that a significant concern?

2 chargers to one battery or bank is ok. What happens is once the charging voltage gets high enough the source with the lower set point will do very little.

Ken

 

[john61ct]

But, what about the charging from two sources (my main question)? Should I continue to turn off the battery charger when the engines are running?

I don't see a problem having both alternators and battery charger connected as long as everything is working properly. It just provides more amps for charging. I'm concerned about what happens if either the charger or an alternator fails and power is fed back into it. Is that a significant concern?

No, as I said no problem.

 

[john61ct]

I may misunderstand, but it sounds to me like he is using those same 2 x 4D batteries as his house bank as well as his start engines. As such, he wouldn’t want to separate the two start batteries as he would drain one of the much more quickly using it as a house battery.

I agree that it sounds like it has been working well for him so far so don’t see a big reason to make a change.

If they're always combined the switch may as well not be there, they'll both run down and leave you flat, or one failing will wreck the other.

Separated, if one goes flat, start the other up, once charging then combine and off you go.

Just a change in usage, not wiring.

Optimizing for real changes would go on for hundreds of posts with many different strongly held opinions

 

[Roger Long]

If they're always combined the switch may as well not be there, they'll both run down and leave you flat, or one failing will wreck the other.

Agreed. Ask me how I know. However, I prefer to cut the house draw down by 50% and keep an eye on the batteries which are fairly new. Improvements to the whole set up are planned. Change is coming.

Since our cooking and refrigeration are AC, I'll probably go with a house bank of golf cart batteries charged only by the generator and an inverter(s) so we can run the fridge and freezer without the generator in the evening quiet time. We can then do battery charging underway when the generator noise isn't an issue. I'll keep it simple and make the starting batteries just that and separated.

For the infrequent (or never) event of one starting battery failing, jumper cables make more sense to me than than a complicated switch set up. Batteries used only for starting should last a long time.

 

[caltexflanc]

Agreed. Ask me how I know. However, I prefer to cut the house draw down by 50% and keep an eye on the batteries which are fairly new. Improvements to the whole set up are planned. Change is coming.

Since our cooking and refrigeration are AC, I'll probably go with a house bank of golf cart batteries charged only by the generator and an inverter(s) so we can run the fridge and freezer without the generator in the evening quiet time. We can then do battery charging underway when the generator noise isn't an issue. I'll keep it simple and make the starting batteries just that and separated.

For the infrequent (or never) event of one starting battery failing, jumper cables make more sense to me than than a complicated switch set up. Batteries used only for starting should last a long time.

This is pretty close to the set up we had on our old Hatteras and it served us well for the first couple of years of full time cruising and minimal marina use. At some point, you will want to have an alternator(or other non-generator dependent source such as solar) charging that inverter bank, but I got away with without having it for a long time. Sans-alternator charging, the generator becomes a single point of failure for your AC system. That, I did not like.

 

[Heron]

Your charger is only going to work when plugged into the dock, or running off a Genset. Underway, typically it's just doing nothing. I don't turn mine off..

 

[Roger Long]

Your charger is only going to work when plugged into the dock, or running off a Genset. Underway, typically it's just doing nothing. I don't turn mine off..

You're kidding.

 

[FoxtrotCharlie]

Your charger is only going to work when plugged into the dock, or running off a Genset. Underway, typically it's just doing nothing. I don't turn mine off..

Unless he is running the genny while cruising