1/2/Both/Off Switch >>> Alternator Diodes

[rardiH36]

My alternator is Yanmar OEM 1980 vintage. After all these years, still puts out charge voltage when the engine is running!

My 1/2/Both/Off switch is wired so that "OFF" totally removes both my batteries from the alternator charge circuit. I know that moving the switch to off when the engine is running causes a spike of "whatever" that can result in the alternator's solid state circuitry (the diodes) to fritz out.

But what about the opposite? If I start the engine with the switch in the "OFF" position, and then move it to say (both) to connect the alternator charge current/voltage back to the batteries, will that cause damage?

This is reason I am asking. I want to see if the heavy duty Li-Ion jump starter I have for my car will start my boat's Yanmar engine with absolutely no (zero) assist from any 12v battery still in the circuit. Even a very depleted battery will still have some residual voltage/amperage left that might assist the jump starter. I have already successfully started the engine with a pretty depleted 12v lawn motor battery substituted into my boat's battery circuit. With the normal batteries disconnected. In this "experiment", the alternator is sensing the load of the lawn motor battery. So all is good.

My concern about these Li-Ion jump starters is that when connected normally, do they also direct voltage/current towards attemtping to recharge what might be totally dead batteries? If it takes me say 30 seconds between the time I connect the jump starter cables to the battery posts before I actually push the start engine button, might there be not enough reserve still left in the jump starter to start the motor? The way around this scenario is to disconnect the batteries from the circuit and start the engine with only the Li-Ion jump starter. Then after a successful startup, turn the 1/2/Both/Off switch back to 1 or 2 or BOTH so the engine's alternator can begin to recharge the boat's dead batteries.

Thoughts?

 

[Davidasailor26]

Lots of factors to consider here. The risk to alternators happens when they’re putting out lots of amps to a battery and then suddenly have no sink for that current, causing a voltage spike. If the switch is already Off then there can’t be any current going to the batteries, thus no risk of a spike. What I don’t know is if the lithium booster itself could be a sink briefly after the engine starts, and if it will suddenly shut itself off or if unplugging it would cause a spike, without having other batteries in the circuit. If the boost pack doesn’t absorb significant current from the alternator then I’d guess there’s no risk of that, so your strategy could work. But I’ve never looked at the exact functioning of those boost packs to see if they absorb charge that way, so your mileage may vary.

Practically speaking though these boost packs are generally built for starting much larger engines than most of us have, even with dead batteries. I have one and I figure if I ever use it I’ll just connect it in parallel with the start bank the way its instructions suggest.

 

[rardiH36]

David26,

Gosh you are a quick typist and very good at getting your thoughts together in short order!

Thanks your comments. One realization that I have is that compared to most newer cars (and maybe also newer boats?), which I believe now have very efficient brushless starter motors, my 1980 starter motor is a real current hog. It protests unless my two group 27 deep cycle batteries are pretty much fully charged. Hence the Li-ion jump starter probably needs to have virtually 100% charge to devote to my start engine task. I have looked up on the internet for information whether these jump starters don't actually put anything out until the sudden demand of the ignition switch being activated. But I haven't been able to find a clear answer. If they don't do anything until the sudden demand for starter motor current, then maybe my concerns of the jump starter depleting itself into the dead battery might not be warranted. But I don't know.

 

[dlochner]

It shouldn't take both batteries being fully charged to start the engine, unless the batteries are pretty old and have lost much of their capacity. If that is the case, then new batteries should be at the top of the list. Also make sure the battery connections are clean. It may also be time for the starter to be rebuilt with new brushes.

To test the the starter with the batteries, disconnect the negative lead from the battery and connect the negative lead from the Jump starter to the battery's negative lead. The Jump starter positive can go to the battery's positive. Place the switch on 1 or 2 depending on which battery you are using.

 

[Davidasailor26]

It shouldn't take both batteries being fully charged to start the engine, unless the batteries are pretty old and have lost much of their capacity. If that is the case, then new batteries should be at the top of the list. Also make sure the battery connections are clean. It may also be time for the starter to be rebuilt with new brushes.

+1 for all of this. Connections and crimps can fatigue over time; and some older boats weren’t designed with much margin for error in their wiring harnesses. If starting is iffy I’d check the voltage at the starter when cranking, and compare that to the voltage at the battery posts. If the difference is significant then start tracing wires to see where the drop may be coming from.

 

[Rick Webb]

If the test is will the jump starter alone start the boat? But you are concerned about the alternator remove the concern by removing the belt and taking the alternator out of the equation.

 

[east coaster]

Maine Sail aka marine how to has a couple of great articles on battery switches, alternators and wiring. I don't have one but Sterling makes a device that stops/prevents alternator damage if switched off while running. It's all on marine how to website.

 

[Stu Jackson]

This is reason I am asking. I want to see if the heavy duty Li-Ion jump starter I have for my car will start my boat's Yanmar engine with absolutely no (zero) assist from any 12v battery still in the circuit.

Then just disconnect the boat batteries. Remove the (-) from the battery's post(s). Should be easy to do. Keep thre jumper pack connected so the AO has somewhere to go. Then shut down engine quickly.

 

[rardiH36]

So many good suggestions from very knowledgeable boaters. I have taken everything "onboard".

I wasn't clear about both batteries being "pretty much fully charged". If one of my two batteries is at max capacity (i.e. at say 11:00am when the solar panel charge controller shows +/- 14v), then it on its own will will start my engine without hesitation. But if the other battery is say reading 12.2V, and I use only that battery, the starter motor will protest before turning over.

Several years ago (and many hundred starts since then), I did remove the original equipment starter for inspection. Quite obvious was the brushes were severally worn. I remember finding online a supplier who sold me a complete new brush plate which I installed. Before closing the starter back up, I did the tests specified in Yanmar's service manual. And I took care to clean the armature. So I am pretty confident that my starter motor is OK.

As to the observation that "older boats weren't designed with much margin for error in their wiring", I fully agree. Just last month I disconnected all of the lugs at both my batteries, at the 1/2/both/off switch, and at the starter motor. All the interfaces were clean. But for sake of good measure, I gave all the interfaces another cleaning before reconnecting. I am not at my boat right now, but from memory the cables between my batteries to the switch and then to the starter are 8 gauge. The total distance between the batteries to the switch to the starter is about 7 feet. I am thinking that 6 gauge might have been the norm only several years after my 1980 construction? I have often thought to replace with larger cable. But the old stuff still does its job!

Good suggestion to remove the alternator belt. Then check that the jump starter on its own will make the engine run.

My question though is still in doubt: Before actually turning the engine start key (or pushing the button), do Li-Ion jump starters when connected per the instructions also direct voltage/current to recharging the 12v battery? Tomorrow I will attempt a new experiment: Using my 2005 Toyota. Firstly deplete my old 12v lawn mover battery to virtually dead. Remove the leads from my Toyota battery. Replace with the lawnmower battery. But also put my Volt/Amp meter in line between the jump starter and the 12v lawnmower battery. See if any current is passing through. If not, then the mystery is solved. The jump starter doesn't do anything until the starter key/button is switched on and the jump starter senses a significant sudden demand for current.

 

[Stu Jackson]

My question though is still in doubt: Before actually turning the engine start key (or pushing the button), do Li-Ion jump starters when connected per the instructions also direct voltage/current to recharging the 12v battery?

Wouldn't that depend on how & what it is connected to when it is turned on?

 

[Tally Ho]

My question though is still in doubt: Before actually turning the engine start key (or pushing the button), do LI-Ion jump starters when connected per the instructions, also direct voltage/current to recharging the 12v battery? Tomorrow I will attempt a new experiment. Using my 2005 Toyota. Firstly deplete my old 12v lawn mover battery to virtually dead. Remove the leads from my Toyota battery. Replace with the lawnmower battery. But also put my Volt/Amp meter in line between the jump starter and the 12v lawnmower battery. See if any current is passing through. If not, then the mystery is solved. The jump starter doesn't do anything until the starter key/button is switched on and it senses a significants sudden demand for current.

I think that the short answer to your question is that if the house or starter batteries are tied in to the system (meaning there is a physical way for the electrons to flow to them) and if those batteries are at a lower charge than your Li-Ion jump-start battery, yes current will try to flow to those batteries.

I am not sure I understand your last comment…unless you mean that the electrons in the jump start battery have someone where to flow...maybe turning the key opens the pathway….but I don’t think a jump start battery has much intelligence to sense a demand for power. The electrons just flow…

My take anyway…

Greg

 

[LloydB]

Wait a minute here - my grandpa explained it with a water hose and a giant tank of water connected to two sprinklers. Just because you turned the water on and over watered the flower box in a half hour doesn't mean that you fixed not watering 1/2 acre of tomatoes yesterday. We won't get into how much water was left in the tank. Or how much water could be sucked back out of the tomatoes for that matter.

 

[rardiH36]

As the original poster of this thread, I thought to finish it up.

I do realize the I am overthinking all this!

At my boat a few days ago, I did do experiments with the Li-ion jump starter device I have:

1) Connecting my Volt-Ohm-Amp meter in series between the jump starter and my 50% depleted small AGM lawn motor battery, and switching the meter to amp read mode, it showed a ~3-amp drain rate from the jump starter to the battery. The jump starter had a beginning voltage of 16.4 volts. (This would be as expected for a 4s Li-ion battery with each cell fully charged to about 4.2 volts.) The initial 16.4v dropped pretty quickly after making the connection to the battery. Upshot: As Tally Ho opined, no intelligent power demand circuit is in the jump starter. I was half hoping that the jump starter wouldn't release the needed high current surge until it detected the sudden demand from the engine's starter. This explains the jump starter's instruction to start the engine within 30 seconds. Waiting say several minutes would probably result in a much depleted jump starter reserve. And only a marginally replenished Group 27 battery. I don't think the jump starter would have much effect charging a large group 27 battery!

2) As suggested by Stu Jackson, I removed the belt between the alternator and the engine. Then disconnected the + terminal cable from my No. 1 battery. Set the 1/2/Both/Off switch to "1". Connected the jump starter + clamp to the now disconnected battery No. 1 + cable. Then connected the jump starter negative clamp to the boat's negative at the battery. The boat's batteries are now removed from the engine start circuit. The only start power is from the jump starter. I turned the engine start key. No hesitation at all by the engine's starter resulted in a quickly running engine. Success! After the engine turned over, I immediately stopped the engine because removing the belt also means the raw water pump isn't rotating.

I will keep the jump starter on the boat. But I still don't know about possible damage to the alternator. A worse case scenario might be that both my Group 27 batteries become severely depleted. Can't start the engine. I have concerns that the depleted batteries will demand so much current from the jump starter that in just a few seconds, before I attempt to start the engine, the jump starter becomes no longer has enought reserve. And anyway, if say the Group 27 battery is down to 10v, will the average voltage/current of a small 16v jump starter and a so much larger depleted battery be enough to start the engine?

So I do as per 2) above, but with the alternator belt still on. I start the engine with the No.1 battery cable removed from the battery and the switch set to No.1. Connect the + jump starter clamp to cable No.1. And negative to negative. Start the engine. The alternator will sense only the current demand towards recharging the jump starter. Probably pretty small. I then turn the switch to Battery No 2. The alternator should then start charging it. Or will the sudden demand for charge current cause damage to the alternator's internal solid state circuitry? Assuming not, I then disconnect the jump starter from the No.1 + cable and reconnect the cable to the battery.

 

[twodzusfittings]

If I start the engine with the switch in the "OFF" position

How are you starting your engine with NO battery power. Do you hand crank it. Is your engine from a British Austin 7?

 

[dlochner]

The jump pack will start to discharge into the good battery and the rate of discharge will depend on the state of charge (SOC) of the battery and its internal resistance. The bigger point is, the electrons are still in the circuit and available to start the battery. If there are 2 people on board, the time between the jump pack being connected and hitting the start button will very short, on the order seconds. Thus there should not be any issues. If you sail solo, then you might consider getting a remote starter switch. It is a simple switch that allows you to start the engine remotely by jumping the solenoid.

I don't think the alternator will be damaged by a load being suddenly placed on it. It will be damaged if the alternator is producing electricity and the load is suddenly cut off.

Given all this, your energies would be better directed to improving battery management so that you are never in the situation where there is inadequate power to start the engine. A key component is a battery monitoring system, both Victron and Balmar make them. Install one and learn how your batteries behave and what you can do to extend their lives.

 

[marcham]

I started my 3jh3e with a 10Ah motorcycle battery..... your lithium booster pack shouldn't have any issues.