Keeping a start battery charged

[wingssail]

Originally Posted by slug

Using the a single bank for starting and house subjects equipment like electronics to voltage spikes

Not s good way to go

I doubt that (voltage spikes). What it does is subject equipment to voltage drops. Often, when the house batteries are a bit low, cranking the engine, drops the voltage on the house system below the threshold for some devices.

In my case the Lowrance GPS is one which frequently drops off-line. It comes back up automatically as soon as the cranking of the engine ceases. Then the voltage on the house system returns to the level it was prior. There is no spike (the alternator does not jump into action and throw a surge, because it ramps up over time).

Even though we profess to having a simple boat we have quite a bit of sophisticated electronics and electrical equipment, . We've been operating it this way (normally starting on the house system) for 34 years. We have never, to my knowledge, damaged any electronic or electrical or other equipment doing it this way.

Your statement is an unsubstantiated boogie man. Further, I am not a follower of recommendations if they do not make sense to me and they have not been to my satisfaction, and are contrary to my own experience and I do not parrot "common knowledge" just 'cause it's been repeated forever by a lot of other sheep .

[a64pilot]

Then if you want to leave it on, Get a voltsge stabilizer, I’ve checked mine and It does in deed hold 13.8 even with the bank low or in equalization at 15.5V, and enables you to operate things when you equalize, like a fridge for instance without concern.
I’ve not checked, but think that my 360 lb 660 AH banks voltage drop isn’t much cranking my little lawnmower sized Diesel, cranking a 540 cu in aircraft engine with a 20 lb battery is of course different.

[parkstone bay]

Originally Posted by wingssail

Why, exactly?

Because the starter battery and its wiring is (or should be) designed to handle large current draws for very short periods, (typically at least scores of amps, but for a maximum 5 seconds, because you don't crank the engine for more than 5 seconds). The domestics bank and its wiring is (or should be) designed to handle a number of much smaller current draws for very much longer periods. On a sailing boat, you will have a number of (usually) quite low power individual demands (plotter/nav instruments, radio on standby, radar, lights for a night passage etc), but that demand will be constant(ish) for perhaps 10, 12, maybe 24 hours.
The demand pattern is different, and hence the two types of batteries are different, and should be reserved, in general, for their allocated duties.
And, as others have said, the voltage drop during start-up can cause electronics to drop out. Having separate start and house batteries eliminates this .

[wingssail]

Originally Posted by rslifkin

Personally I prefer not to start engines from the house bank due to the voltage dip issue. Most electronics won't be damaged by it, but some will restart. Not a big deal, but I like being able to have stuff on and not worry about it. For example, I may have the plotter on to make a route before I start up. It's nice not too have to restart it and instead let it just stay on.

Yes, I agree that it would be nice not to have anything, (in my case one of the GPS') shut down when I start. If I am worried about that I switch to the start bank to start. Its higher amperage output prevents that.

But in my case, and I really need to emphasize this, I do not believe in purchasing and installing extra devices because of some perceived extra convenience when the result is more complexity and the original "inconvenience" was really not that troublesome. I will put up with some rare and minor inconvenience for simplicity and reliability and to retain control over my devices. In that sense I am a purist.

BTW my plotter does not drop off, it has it's own internal battery to cover such situations, and only one of my four GPS units even skips a beat. It is another boogie man.

Too many of us are electronic tinkerers instead of sailing enthusiasts and spend more time selecting, buying, installing, trouble shooting and fixing than we do sailing.

[wingssail]

Originally Posted by parkstone bay

Because the starter battery and its wiring is (or should be) designed to handle large current draws for very short periods, (typically at least scores of amps, but for a maximum 5 seconds, because you don't crank the engine for more than 5 seconds). The domestics bank and its wiring is (or should be) designed to handle a number of much smaller current draws for very much longer periods. On a sailing boat, you will have a number of (usually) quite low power individual demands (plotter/nav instruments, radio on standby, radar, lights for a night passage etc), but that demand will be constant(ish) for perhaps 10, 12, maybe 24 hours.
The demand pattern is different, and hence the two types of batteries are different, and should be reserved, in general, for their allocated duties.
And, as others have said, the voltage drop during start-up can cause electronics to drop out. Having separate start and house batteries eliminates this .

Well, you have drawn a nice straw horse to support your argument but it is BS. Nothing (except the battery type issue) you say, true as it is, supports always using a starting battery for starting the engine and never using the house battery to do so.

There is NOTHING about using the house bank to start the engine that presumes that inappropriate sized wiring is in play. Both house and start batteries should be (and in my case, are) wired to the battery switch with heavy duty 2/00 cables. Likewise the cable from the battery switch to the starter is also heavy duty 2/00 cable. Likewise the alternator output cables to the battery switch are 2/00. Likewise the cables from the battery switch to the inverter charger and to the windlass are also 2/00. From the switch to the The DC panel and downstream to ALL of the domestic and electronic items the wiring is with smaller wires and cables appropriate for their amperage needs. There is no inappropriate sized cabling.

The only inappropriate usage is the battery itself. The house bank is not able to supply starting amperage with out dropping voltage, it is not designed to do so. But for 1-2 seconds it does not hurt.

[noelex 77]

There are many different ways of wiring and using a boat’s electrical system. Overall, I favour starting the engine with the start battery rather than house bank as a routine (but have the ability to start engine with both banks). This is assuming a large house bank and small start battery rather than the old system of two equally sized banks. As well as avoiding voltage spikes to sensitive electronics, it makes sure the start battery has not deteriorated to the extent that it will not start the engine.

The house bank is much larger than the start battery and is monitored more closely (with the battery monitor). Even if not used to start the engine, the house bank is reasonably tested with the normal domestic loads. A deterioration in the house bank, especially to the extent that the large house bank could not generate enough current to start the engine, is usually obvious. On the other hand, if the start battery is not used routinely to start the engine, a deterioration in this battery is harder to pick.

Battery ageing is often only noticeable when a load is placed on the battery. Therefore, if you are not starting the engine with the start battery, at least regularly test that the start battery is capable of this task. If you are going to test the start battery is indeed capable of starting the engine why not do this every time you start the engine? The start battery is likely to die primarily of old age rather than use.

[mitiempo]

Originally Posted by wingssail

I really have to agree with A64pilot on this one. I don't think that subjecting the start battery to absorb voltages for long periods of time while it is already at 100SOC is going to be great for that nice Odyssey so therefore connecting the ACR to simply parallel the house and start whenever 13.0 or more volts are present isn't a good idea.

However, I don't agree that getting rid of the start battery is too smart of an option. In a lot of years of cruising we've always be able to start our engine, about 99% of the time on the house bank, but we've had to use the start battery quite a few times (occasionally "Both"). So keep it.

But here is another consideration about using automatic devices, beyond the fact that you can't really tell how they are working. Complexity!

I read Rod Collins paper on the ACR (https://marinehowto.com/automatic-charging-relays/). I don't think he addressed the issue of excess voltage on the start battery very well, but what really struck me was the circuit diagram he showed as an example of a properly wired system using an ACR.

Attachment 218799

Holy friggin' cow, there are four battery switches, and at least 11 separate external fuses outside of the distribution channel, and other than an amp hour counter, a volt meter and possibly an ammeter on the distribution panel, there is no way of monitoring this mess. It has at least four "black boxes" (ACR, MPPT, AC Charger, and presumably a Alt regulator) and no display of what any of them are doing. And still with all of this stuff you have NO WAY of disconnecting the Alternator, solar, AC charger, bilge pump, or ACR from the batteries short of pulling the fuses because the ACR will be combining the house and start bank, so the start bank will be connected through the ACR to all of these devices. AND, you have to go through a fairly complicated process to charge ONLY the start battery if everything is dead and you want just get enough SOC into it to start the engine.

And that is just a fairly ordinary installation.

So with this system you have a lot of components, and you have to be totally trustworthy that they are all doing what they are supposed to do (because you cannot monitor it), and you have completely turned over all control to the devices and it is difficult to quickly change what is going on. On my boat I want a simple set up that I, or my wife, or a crew member can operate. (BTW turning the battery switch to "Off" on my system with the engine running will not blow the diodes in the alternator because the field voltage in the alternator comes from the regulator which is also on that battery switch).

And none of that addresses the extra time you will spend (and you WILL spend it) trouble shooting when the system fails, which it will.

But to those of you (OP not included) who would rather buy something and install it, then another, and another and so on to solve the issue raised by each previous installed item, instead of having a simple system, relying on yourself to keep the switches where they need to be, and going sailing. Go ahead. The marine industry needs you.

And to the OP, I certainly doubt that when you were flying helicopters that you or any other pilot would have been happy to turn over all control to some un-monitorable electronic devices and just trust that they were all doing the right thing.

Look again.
The system has a battery monitor. Everything is fused as it should be. The charger can be turned off if desired with the AC breaker (not shown). There is a service switch to shut the alternator off for service.

It is an excellent system.

[a64pilot]

Any idea that you harming your house bank by using it to crank the engine on an average sail boat is silly and uninformed.
However if you want a battery just to start an engine, your better served with a smaller and lighter and less expensive starter battery, but there is no logical reason at all that a house bank can’t start an average sized sailboat engine with no sweat probably capable of doing it 100 times or more.

What I really cant understand is all these posts or what will I do when I kill my house bank by accident, do some of you really do that? Am I the only person who looks at my voltage and SOC first thing in the morning and again in the afternoon? Am I the only person who has a low voltage alarm?

I guess my answer to them is you will do the same thing when you accidentally run out of fuel, because that’s all a battery bank is, an energy supply, like your fuel tank, except I can refuel my battery bank at sea, I cannot my fuel tank, well actually I can but that’s another argument.

[a64pilot]

Originally Posted by mitiempo

Look again.
The system has a battery monitor. Everything is fused as it should be. The charger can be turned off if desired with the AC breaker (not shown). There is a service switch to shut the alternator off for service.

It is an excellent system.

I can assure you, anything He posts , is in fact an excellent system, possibly sometimes more complex than necessary, but he covers nearly all possibilities.

[mitiempo]

Originally Posted by parkstone bay

Because the starter battery and its wiring is (or should be) designed to handle large current draws for very short periods, (typically at least scores of amps, but for a maximum 5 seconds, because you don't crank the engine for more than 5 seconds). The domestics bank and its wiring is (or should be) designed to handle a number of much smaller current draws for very much longer periods.

The domestics bank should be wired with the same capabilities as the start battery. That means large (2/0) wiring to the switch. When the start battery is dead or has an issue the domestics bank is your starter and should be capable of this.

[mitiempo]

Originally Posted by a64pilot

Any idea that you harming your house bank by using it to crank the engine on an average sail boat is silly and uninformed.


What I really cant understand is all these posts or what will I do when I kill my house bank by accident, do some of you really do that? Am I the only person who looks at my voltage and SOC first thing in the morning and again in the afternoon? Am I the only person who has a low voltage alarm?

Yes a house bank will have no problem starting an engine. Deep cycle batteries, while having less cranking capability than a start battery, accumulatively have what it takes to start as there are more than one of them.

What if your house bank has an issue like a short circuit causing its demise. Are you going to row? Your logic means there is no reason to carry a spare tire on a car.

Being ready to solve any issue - no matter how rare - is called being prepared.

[wingssail]

Originally Posted by mitiempo

Look again.
The system has a battery monitor. Everything is fused as it should be. The charger can be turned off if desired with the AC breaker (not shown). There is a service switch to shut the alternator off for service.

It is an excellent system.

Nope, it does not have a battery monitor, it has an amp hour counter, and if you think that is sufficient to monitor all this stuff, then you are an innocent babe in the woods.

Turning off the AC does not disable the inverter function, assuming there is one, (maybe it has no inverter or it is separate, more complication, not shown).

And a service switch to shut off the alternator? Where is that hidden little device?

If you add all the stuff not shown, you need a A3 sized page to show it and an ABYC certified operator on board in case something has to be diagnosed or changed in a hurry and nobody else on board has a clue.

[mitiempo]

Originally Posted by wingssail

Nope, it does not have a battery monitor, it has an amp hour counter, and if you think that is sufficient to monitor all this stuff, then you are an innocent babe in the woods.

Turning off the AC does not disable the inverter function, assuming there is one, (maybe it has no inverter or it is separate, more complication, not shown).

And a service switch to shut off the alternator? Where is that hidden little device?

If you add all the stuff not shown, you need a A3 sized page to show it and an ABYC certified operator on board in case something has to be diagnosed or changed in a hurry and nobody else on board has a clue.

Open your eyes. There is a Victron battery monitor shown to the left of the DC panel.

It is not an inverter but a Promariner Pronautic P battery charger - turning off the breaker disables it.

The on/off switch in the lower left will disable the alternator.

Everything is fused as it should be.

Nowhere as complicated as some of the nightmares I see on many boats.

I,m not an innocent babe in the woods but a marine electrician.

[wingssail]

Originally Posted by a64pilot

...What I really cant understand is all these posts or what will I do when I kill my house bank by accident, do some of you really do that? Am I the only person who looks at my voltage and SOC first thing in the morning and again in the afternoon? Am I the only person who has a low voltage alarm?

OK I'll give you two examples:

1. You have been at sea for a few days, sailing continuously, and the extra amperage that is required to run the ship at night is running down the house batteries. You know this by the battery voltage or other monitors, or by a low voltage alarm, but it's midnight and you don't want to start a charging cycle at that time (for whatever reason). You want to wait until the scheduled cycle in the morning. But morning comes and the house batteries are too low. You switch to the start battery and Bob's your uncle.

2. You leave you refer and freezer full of food and the refer system running, on shore power, when you leave the boat for a couple of days. There is insufficient sun or inadequate solar power to keep the batteries up, but shore power does that, until the cord gets unplugged. You come back and the batteries are dead, (plus, the food is rotten. You switch to the start battery and Bob's your uncle (except for the rotten food).

[wingssail]

Originally Posted by mitiempo

Open your eyes. There is a shown to the left of the DC panel.

It is not an inverter but a Promariner Pronautic P battery charger - turning off the breaker disables it.

The on/off switch in the lower left will disable the alternator.

Everything is fused as it should be.

Nowhere as complicated as some of the nightmares I see on many boats.

I,m not an innocent babe in the woods but a marine electrician.

"Victron battery monitor"? It is labeled as an AH Counter.

"The on/off switch in the lower left will disable the alternator" Not if there is any source of charging voltage. In that case the ACR will put the batteries in parallel and the start battery will supply to the Charge Bus and keep the alternator running.

Of course you are a marine electrician, that is why you insist that all this stuff must be installed, without any care in the world about the operator of it all.

Do you fly out to Papua New Guinea in the middle of the night to help some guy's wife figure out why nothing is working, or which of the 11 fuses has blown? Or why the next day the solar doesn't seem to be charging up the batteries (or even if it is or is not putting out amps).

No, I got your philosophy: Make it perfect, Make it expensive, Make it indecipherable, and make them come back to you if anything isn't working.