Keeping a start battery charged

[a64pilot]

Originally Posted by wingssail

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).

Or you plug the shorepower cord in and Bob’s still your Uncle.

If you have a battery go bad, remove it from the bank, or in my case I have two house banks, ganged together with the battery switch to both, so select the one without the bad battery, and Bob’s still in the family, but do wire around the bad battery when you get a chance.

Or if your stupid and sailing and choose to ignore the low voltage alarm for whatever reason, when you get around to it, crank the Honda, and after an hour or so, Bob’s back.

But having all these single use batteries laying around is foolish and wasted money and weight.
Most have one fuel tank and think nothing about it, no reserve tanks, but have to have several different starter batteries?
Best in my opinion to have two house banks, gang them together as one but can separate with the switch and then you have no dead lead, remember the larger your house bank is, the shallower you will cycle it, and the longer it will last.

[noelex 77]

You cannot start most modern diesel engines without a battery. The battery need not be large, but it needs to be healthy to generate the high current needed.

It is therefore prudent on cruising vessels to have two at least reasonably independent batteries, or battery banks, that are capable of starting the engine.

Especially if one of these options is a single start battery, as is common, its capabilities need to tested regularly, preferably each start. A single battery only has to lose a small amount of health before it is incapable of delivering the high current demand needed to start a diesel engine, especially under adverse conditions such as cold temperatures or a small air leak in the fuel system.

With minor variations the basic model for all cruising yachts for some years has been a large domestic bank and a single start battery, or small battery start bank. With the ability to start the engine from the domestic bank in the event of a failure of the start battery. I cannot see an alternative system offering the same advantages.

[mitiempo]

Originally Posted by wingssail

"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......

The picture is of a Victron battery monitor.

If the switch in the lower left is off the house bank is not connected to any charge source or load.

Every load needs a fuse sized for the load and wire size used. This prevents fires.

I do not think it is hard to decide if a fuse is blown.

It is a simple system that is wired properly. Battery switches - one for the house loads, one for the engine start, and one to cross either way if needed. 3 charge sources going to a charge bus with proper fusing. An ACR to take care of the start battery from any charge source.

You're suggesting that it should be imperfect?

[wingssail]

Originally Posted by a64pilot

Or you plug the shorepower cord in and Bob’s still your Uncle.

If you have a battery go bad, remove it from the bank, or in my case I have two house banks, ganged together with the battery switch to both, so select the one without the bad battery, and Bob’s still in the family, but do wire around the bad battery when you get a chance.

Or if your stupid and sailing and choose to ignore the low voltage alarm for whatever reason, when you get around to it, crank the Honda, and after an hour or so, Bob’s back.

But having all these single use batteries laying around is foolish and wasted money and weight.
Most have one fuel tank and think nothing about it, no reserve tanks, but have to have several different starter batteries?
Best in my opinion to have two house banks, gang them together as one but can separate with the switch and then you have no dead lead, remember the larger your house bank is, the shallower you will cycle it, and the longer it will last.

OK, good answer, but, you asked how it could happen, I gave you some ideas. There may be others.

[mitiempo]

Originally Posted by a64pilot

Or if your stupid and sailing and choose to ignore the low voltage alarm for whatever reason, when you get around to it, crank the Honda, and after an hour or so......

But having all these single use batteries laying around is foolish and wasted money and weight.

If you are dragging the anchor towards a lee shore you probably do not have that hour for the Honda to charge anything.

Who said anything about "all these single use batteries" lying around. You are the one with the separate generator battery and 2 house banks. A single house bank of whatever size and a separate dedicated start battery that can also start the generator is a reliable system with a backup if either bank fails for any reason.

[a64pilot]

Originally Posted by noelex 77

You cannot start most modern diesel engines without a battery. The battery need not be large, but it needs to be healthy to generate the high current needed.

It is therefore prudent on cruising vessels to have two at least reasonably independent batteries, or battery banks, that are capable of starting the engine.

Especially if one of these options is a single start battery, as is common, its capabilities need to tested regularly, preferably each start. A single battery only has to lose a small amount of health before it is incapable of delivering the high current demand needed to start a diesel engine, especially under adverse conditions such as cold temperatures or a small air leak in the fuel system.

With minor variations the basic model for all cruising yachts for some years has been a large domestic bank and a single start battery, or small battery start bank. With the ability to start the engine from the domestic bank in the event of a failure of the start battery. I cannot see an alternative system offering the same advantages.

I can, split your domestic bank in half but ganged together with the 1,2,all switch. Then you have two domestic banks that you can easily isolate one if it goes bad.
If you manage to kill the bank down to where you can’t start the engine, you wait until alternate sources, Solar or suitcase gen charges it back up, or often removing loads and letting one rest will recover enough to start a smallish sailboat motor.

Back to how do you discharge a house bank down so low that it can’t start a small motor and not know it, assuming your on the boat?

[noelex 77]

Originally Posted by a64pilot

Most have one fuel tank and think nothing about it, no reserve tanks

Personally, I would think very seriously about this issue. It is not hard to at least have a seperate jerry can with independent clean fuel and simple system of fuel lines feeding this into the main engine, bypassing much of the normal supply. This is especially important if you have a single diesel tank and should be a simple system that is permanently (or at least easily) rigged.

Long distance cruising boats need back up redundant options of critical systems. A seperate fuel, or battery system to help ensure the reliable running of the main engine is easy and cheap to implement. These systems should receive priority above optional extras.

[wingssail]

Originally Posted by mitiempo

The picture is of a Victron battery monitor.

If the switch in the lower left is off the house bank is not connected to any charge source or load.

Every load needs a fuse sized for the load and wire size used. This prevents fires.

I do not think it is hard to decide if a fuse is blown.

It is a simple system that is wired properly. Battery switches - one for the house loads, one for the engine start, and one to cross either way if needed. 3 charge sources going to a charge bus with proper fusing. An ACR to take care of the start battery from any charge source.

You're

Boy, mitirmpo, you are stubborn.

Even if that little round Vectron device is a battery monitor (how would we know?), there is no way, from one simple shunt on the neg line that it can tell you much of anything except the soc of the house battery bank.

The switch on the lower left? But does not the ACR put the batteries in parallel if any charging voltage is present (that is sure what the ACR document I read explicitly states) so then the voltage from the start bank goes through to the charge bus thereby energizing the alternator (and everything else)?

You don't think it is hard to tell if a fuse is blown? Me neither, but tell that to my wife, or even how to figure out which of the eleven fuses to check without proper monitoring of all the devices.

Am I suggesting that it should not be perfect? Absolutely! That is exactly what I am suggesting. I just want it to be very good (perfect is not required), very simple (that is required), and very much safer than this kluge of excess of blind trust in electrical technicians and little black boxes that nobody knows what they are doing at any given moment. In any case this diagram is not even perfect and at any rate perfect is the enemy of good. Making it perfect is uselessly expensive and complex to operate and maintain and if you can't figure it out in an emergency, in the dark, in a smoke filled boat, then it is also dangerous.

By the way, you did not tell us how far your service area and hours extend when people have trouble with your monument to excess.

That's it, I'm done, finished with this thread.

[a64pilot]

Originally Posted by mitiempo

If you are dragging the anchor towards a lee shore you probably do not have that hour for the Honda to charge anything.

Who said anything about "all these single use batteries" lying around. You are the one with the separate generator battery and 2 house banks. A single house bank of whatever size and a separate dedicated start battery that can also start the generator is a reliable system with a backup if either bank fails for any reason.

I actually don’t have two house banks, I have one that can easily be separated into two.
If I’m dragging anchor towards a lee shore and can’t start the engine, I’d set my second anchor, a 25kg Rocna.
Anyone can come up with an improbable chain of events to an unsurvivable situation, you cover the most likely, nothing is 100%.
Do you have a secondary engine? What if your dragging towards that lee shore and the injector pump fails?

Just now I have an extra little $150 battery and was trying to come up with a use for it, and wondered how people kept start batteries charged, without overcharging them was all.

Ideal or a good way would be to keep the stock alternator and have it charge the start battery, and a second separate alternator with three stage charging for the house, and the ability to gang house and start together, that way you would have a back up alternator.

But really the thread was a brainstorming thread of how do you do it, and possible advantages / disadvantages to different ways.

I’m also replacing my house bank with one I’m a little uncomfortable with and want to have a backup, so I’ll keep a large portion of my existing bank, but not gang it to the new one, but have it as a spare until at least I become confident with the new one.

That makes it a couple hundred lbs of dead lead.

[wingssail]

Originally Posted by a64pilot

I actually don’t have two house banks, I have one that can easily be separated.
If I’m dragging anchor towards a lee shore and can’t start the engine, I’d set my second anchor, a 25kg Rocna.
Anyone can come up with an improbable chain of events to an unsurvivable situation, you cover the most likely, nothing is 100%.
Do you have a secondary engine? What if your dragging towards that lee shore and the injector pump fails?

Ahah! That's a good one. If you are dragging there must be wind blowing. Set sail and use your battery power to raise the anchor and then sailing to safety?Assuming you boat is ready to set sail and will go to weather.

[mitiempo]

Originally Posted by wingssail

Boy, mitirmpo, you are stubborn.

Even if that little round Vectron device is a battery monitor (how would we know?), there is no way, from one simple shunt on the neg line that it can tell you much of anything except the soc of the house battery bank.

The switch on the lower left? But does not the ACR put the batteries in parallel if any charging voltage is present (that is sure what the ACR document I read explicitly states) so then the voltage from the start bank goes through to the charge bus thereby energizing the alternator (and everything else)?

You don't think it is hard to tell if a fuse is blown? Me neither, but tell that to my wife, or even how to figure out which of the eleven fuses to check without proper monitoring of all the devices.

Am I suggesting that it should not be perfect? Absolutely! That is exactly what I am suggesting. I just want it to be very good (perfect is not required), very simple (that is required), and very much safer than this kluge of excess of blind trust in electrical technicians and little black boxes that nobody knows what they are doing at any given moment. In any case this diagram is not even perfect and at any rate perfect is the enemy of good. Making it perfect is uselessly expensive and complex to operate and maintain and if you can't figure it out in an emergency, in the dark, in a smoke filled boat, then it is also dangerous.

By the way, you did not tell us how far your service area and hours extend when people have trouble with your monument to excess.

That's it, I'm done, finished with this thread.

The diagram was posted by Mainsail somewhere to show ACR wiring. There was likely a description along with it that was not posted here. Not sure who even posted it.

The voltage from the start bank cannot go through the ACR unless the start battery is above 13 volts - in other words charging. With the switch off the house bank is totally isolated. There is no reason to ever turn off an alternator when the engine is running. I would put the switch between the alternator and the charge bus though. It is only switched off when working on the alternator and is usually not in an obvious place.

If your boat is smoke filled from an electrical issue there is a very good chance that something was not fused properly. Close enough works for some things but electrical is not one of them.

[BlackHeron]

Cruisers Forum never disappoints...

[a64pilot]

Originally Posted by wingssail

Ahah! That's a good one. If you are dragging there must be wind blowing. Set sail and use your battery power to raise the anchor and then sailing to safety?Assuming you boat is ready to set sail and will go to weather.

Well then let out the rest of your rode, that doesn’t require battery power and sail?

Like I said, you can talk yourself Into trying to cover every unlikely scenario until you never leave the dock.
I hear it all the time, last one from a power boater “we would never travel at night, I’ve seen stuff you could hit”

[BlackHeron]

Super helpful advise when the sea is rolling and the reef is a couple dozen feet off of your transom when you realize the hook isn't holding and neither your start or house banks are able to crank over the auxillary.

Maybe throw the Honda overboard too, on another line?

[Frankly]

Anchors, Light(e)ning protection, guns aboard, now generator start batteries. Must be the slow TV season.

I have been in the single house/start battery camp for 14 years. If the starting voltage drops low enough to trigger a low voltage alarm, time for new batteries (or better wiring).

Put the Odyssey in the car, getting out of Jacksonville might be more urgent than getting the anchor up.


Frankly