When switching from 1 to 1+2 is not a make before break. Switching to 1+2 makes a connection to 2nd battery…no connections are broken. Only when you switch to 2 from 1+2 or back to 1 from 1+2 is any connection broken…most importantly only one connection is broken so alternator is not ever disconnected. If you want to be pedantic, switching from 1 to 2 through 1+2 is a make (1 connected then 2 is connected when 1+2 is selected) before break (1 is disconnected when 2 is selected).
I avoid all that crap by connecting my alternator output directly to the positive terminal of one of my battery banks. An ACR charges the other bank. Both bank positives terminals get connected to switch 1 and 2 respectively. The switch is now solely a bank selection switch and not a bank selection/charging direction switch. There no chance of blowing anything in the alternator this way as the alternator always sees a load.
I believe this problem would be solved by using a battery charging system with an Automatic Charging Relay. Those switches are simple OFF....ON....BOTH BAT. The operator doesnt do anything. Just be sure to run the boat with the switch in the ON position. Blue Seas has system like this and it works like a champ.
Hi Jeff, great explanation, thanks. Given what you said, should you connect the motor to the start battery directly and then run a lead from the start battery positive to the common terminal on the on/off/combined switch? If so should or could you also put a simple on/off switch between motor and battery to allow isolation if needed? Thanks
Some switches have an alternator field switch ie the two smaller terminals, no field no problem.on the switch turns off the aI use a capacitor 1/2 or one farad connected to the alternator and ground. The older refrigerator system required always to be connected to a battery. The capacitor allowed the battery to be disconnected with the refrigerator running powered by a battery charger. The capacitor absorbed the voltage spike, back efm from dc coils, and reduced the voltage pulses from pumps and auto pilot surges
Excellent video, explained a lot but I still have a question: Is a battery selector switch’s purpose ONLY to select from what battery bank to draw power from (starter, house or both) when you need power, OR does it also determine what bank to charge to when motoring (starter, house or both) from the alternator?
Hi Pete, great question, in 99% of stock (i.e. typical installations) your battery source selector is for simultaneously running loads and deciding which batteries (1, 2, or both) get a charge.
Hey Jeff, I have a quick question is there a battery selector switch for a 24 volt system? I I burned up a couple wires last weekend trying to run my new to me trolling motor. I have two house batteries and one starter. The two wires coming from the selector switch to the two house batteries melted all of the coatings off of them. I just connected one of them and it seem to work OK. I do not have the trolling motor going through the selector switch just to the battery with a resetting breaker. I unplug the trolling motor upfront until I’m in the water.
I will be rewiring my boat this fall as looking at the contacts are end have corrosion build up.Now the question I will be installing a victron battery isolator from the alternator to house and starter battery bypassing the battery switch. In doing so I am thinking of having 2 battery switches 1 for house other for starter both would be on/off only. The other question is having 2 banks (6 volt agm x2 per bank ) for house batteries would it be a good idea to have a battery montor for each bank even they would act as one. I’m thinking that in doing this I would be able to see the condition of each bank. Thanks
I'd like to ask a ?. my name is Derek and the ? is I just ordered a blue sea mini add a battery kit. but I didn't realize when I ordered it that it said 65 amp. I had already ordered 60 amp breaker switches. can i still use them for my install or will they keep tripping when I turn the switch on. I only have two fish finders and led deck lights and led compartment lights on a bass tracker. my trolling motor is on a separate set of batteries. thank u
not in the old days.. that was one way we could tell if an alternator.. or in most cases then a generator was working.. un plug your battery and if the vehicle kept running everything was ok.. if not your alt/gen was bad.. Todays "modern" and "improved" systems you can't do squat or tell squat with out some sort of toy that tells you what to do..
So, never connect lithium batteries to an alternator? Wenn fully charged the bms will disconnect. And isn't it the same story with solar? You also should not disconnect a panel while it delivers power? I am a bit confused. Last year I changed to lithium batteries. So far my alternator (in honda bf15) still works..Am I just lucky?
No, you're not lucky. The BMS will disconnect the charging current from the alternator to your lithiums. However, obviously, there's some internal circuitry inside the BMS that prevents your alternator from seeing an open circuit so no blown alternator.
Some BMS do not communicate with the alternator, and if the BMS decides the battery is at risk of overcharging, your alternator will be suddenly disconnected from the Lithium battery and your alternator might be damaged in the instant disconnect.
Why does the alternator have to be switched via the battery main switch. Have a permanent connection fused from the alternator to the batteries, maybe via isolation diodes and then have only the starter motor switched?
In 2022 this system is archaic ! Cant they invent a better one ? Eg If I’m at the helm I would never leave it to go below and switch over before starting the engine often in an emergency Am I right or wrong ??
Surprised that someone doesn’t make an over-voltage device to absorb the sudden voltage spike on a disconnect, and cut the power to the field coil. It’d only need to absorb the max amperage of the alternator for a few seconds. A high wattage resistor could easily “sink” that much power.
@@PacificYachtSystems like this? www.st.com/resource/en/application_note/dm00024664-schottky-diode-avalanche-performance-in-automotive-applications-stmicroelectronics.pdf
The alternator dies because the high amperage output is suddenly interrupted, causing a voltage spike, which destroys the alternator’s diodes, and may cause internal short circuits.
@@borysnijinski331 not terribly technical. It’s the same principle as the ignition coil in a make and break engine. Current through a conductor produces a magnetic field around the conductor. Cut the current suddenly, and the field collapses, inducing voltage in the conductor. In an ignition coil, 50,000 volts is normal. In an alternator, I don’t know, but I’d hazard a guess at several thousand volts. This can be easily demonstrated by energizing an electromagnet with a battery, then disconnecting it. When the connection is broken, a spark will be produced.
I like your videos but you tend to exaggerate and make a lot of things sound much worse than they really are! You said that if you were to turn your battery switch off for even a millisecond it would blow your alternator, That is total BS! I know for a fact that if you were to rotate your switch past the off position it is not guaranteed you will blow your alternator, What you should have said is it is not recommended and you could end up hurting the alternator! I have done it at least a dozen times after having my alternator rebuild in 2001! My boat is a 1987 so I had the starter and alternator rebuilt in 2001 solely due to age, Here we are in 2023 and that alternator is still on my engine! You really make boating sound like it is all work and nothing but problems! I am from New Jersey and my boat has been docked in salt water from May through September ever since I bought it in 1995, My boat gets used once in a while after work during the week as well as every weekend! Boating is very enjoyable as well as relaxing, Most of the problems with boating is almost always caused by the current or former owner!
When switching from 1 to 1+2 is not a make before break. Switching to 1+2 makes a connection to 2nd battery…no connections are broken. Only when you switch to 2 from 1+2 or back to 1 from 1+2 is any connection broken…most importantly only one connection is broken so alternator is not ever disconnected. If you want to be pedantic, switching from 1 to 2 through 1+2 is a make (1 connected then 2 is connected when 1+2 is selected) before break (1 is disconnected when 2 is selected).
Thanks for sharing.
I think he knows this. He is talking about being for sure of a faulty or just plain crappy switch… in those cases you could be wrong.
I avoid all that crap by connecting my alternator output directly to the positive terminal of one of my battery banks. An ACR charges the other bank. Both bank positives terminals get connected to switch 1 and 2 respectively. The switch is now solely a bank selection switch and not a bank selection/charging direction switch. There no chance of blowing anything in the alternator this way as the alternator always sees a load.
Well done, we have the same setup on our sailboat too.
Can I add a isolator from starting battery to house battery so that the later gets charged when former gets fully charged?
@@jeffzhang394 An ACR (Automatic Charging Relay) will do this job for you.
I believe this problem would be solved by using a battery charging system with an Automatic Charging Relay. Those switches are simple OFF....ON....BOTH BAT.
The operator doesnt do anything. Just be sure to run the boat with the switch in the ON position. Blue Seas has system like this and it works like a champ.
Hi Jeff, great explanation, thanks. Given what you said, should you connect the motor to the start battery directly and then run a lead from the start battery positive to the common terminal on the on/off/combined switch? If so should or could you also put a simple on/off switch between motor and battery to allow isolation if needed?
Thanks
Great question and thank you for clarifying!
Any time!
Some switches have an alternator field switch ie the two smaller terminals, no field no problem.on the switch turns off the aI use a capacitor 1/2 or one farad connected to the alternator and ground. The older refrigerator system required always to be connected to a battery. The capacitor allowed the battery to be disconnected with the refrigerator running powered by a battery charger. The capacitor absorbed the voltage spike, back efm from dc coils, and reduced the voltage pulses from pumps and auto pilot surges
Edit after no problem. I use a capacitor…..
Thanks for sharing Joe, well explained.
Excellent video, explained a lot but I still have a question: Is a battery selector switch’s purpose ONLY to select from what battery bank to draw power from (starter, house or both) when you need power, OR does it also determine what bank to charge to when motoring (starter, house or both) from the alternator?
Hi Pete, great question, in 99% of stock (i.e. typical installations) your battery source selector is for simultaneously running loads and deciding which batteries (1, 2, or both) get a charge.
Hey Jeff, I have a quick question is there a battery selector switch for a 24 volt system? I I burned up a couple wires last weekend trying to run my new to me trolling motor. I have two house batteries and one starter. The two wires coming from the selector switch to the two house batteries melted all of the coatings off of them. I just connected one of them and it seem to work OK. I do not have the trolling motor going through the selector switch just to the battery with a resetting breaker. I unplug the trolling motor upfront until I’m in the water.
Great to know
Thanks Javier.
I will be rewiring my boat this fall as looking at the contacts are end have corrosion build up.Now the question I will be installing a victron battery isolator from the alternator to house and starter battery bypassing the battery switch. In doing so I am thinking of having 2 battery switches 1 for house other for starter both would be on/off only. The other question is having 2 banks (6 volt agm x2 per bank ) for house batteries would it be a good idea to have a battery montor for each bank even they would act as one. I’m thinking that in doing this I would be able to see the condition of each bank. Thanks
Blue Sea makes a battery switch with “AFD” that allows you to switch while running without damage to alternator.
Quite useful, but rarely wired.
I'd like to ask a ?. my name is Derek and the ? is I just ordered a blue sea mini add a battery kit. but I didn't realize when I ordered it that it said 65 amp. I had already ordered 60 amp breaker switches. can i still use them for my install or will they keep tripping when I turn the switch on. I only have two fish finders and led deck lights and led compartment lights on a bass tracker. my trolling motor is on a separate set of batteries. thank u
Why not just direct connect the alternator output to the house bank and not through the switch
Yep, that's one way to avoid interrupting the alternator circuit while the engine is running. Did this exact setup on my boat.
not in the old days.. that was one way we could tell if an alternator.. or in most cases then a generator was working.. un plug your battery and if the vehicle kept running everything was ok.. if not your alt/gen was bad.. Todays "modern" and "improved" systems you can't do squat or tell squat with out some sort of toy that tells you what to do..
Thanks for sharing, definitely learnt something.
@@PacificYachtSystems Well, it is only useful if you work on old engines with generators.. And I thank you for sharing!
So, never connect lithium batteries to an alternator? Wenn fully charged the bms will disconnect. And isn't it the same story with solar? You also should not disconnect a panel while it delivers power?
I am a bit confused. Last year I changed to lithium batteries. So far my alternator (in honda bf15) still works..Am I just lucky?
No, you're not lucky. The BMS will disconnect the charging current from the alternator to your lithiums. However, obviously, there's some internal circuitry inside the BMS that prevents your alternator from seeing an open circuit so no blown alternator.
Some BMS do not communicate with the alternator, and if the BMS decides the battery is at risk of overcharging, your alternator will be suddenly disconnected from the Lithium battery and your alternator might be damaged in the instant disconnect.
What if the alternator is wired to the house bank direct (fused) and a combiner is used to keep the start battery happy?
Good suggestion, my alternator is setup exactly like that.
Will connecting to the starting battery directly and add an isolator to house work better?
Why does the alternator have to be switched via the battery main switch. Have a permanent connection fused from the alternator to the batteries, maybe via isolation diodes and then have only the starter motor switched?
Good point, we are constantly modifying alternator and starter circuits for this very reason.
In 2022 this system is archaic !
Cant they invent a better one ?
Eg If I’m at the helm I would never leave it to go below and switch over before starting the engine often in an emergency
Am I right or wrong ??
Surprised that someone doesn’t make an over-voltage device to absorb the sudden voltage spike on a disconnect, and cut the power to the field coil. It’d only need to absorb the max amperage of the alternator for a few seconds. A high wattage resistor could easily “sink” that much power.
Exactly, Balmar sells a Schottky (sp?) Diode as protective unit. Anyone can share any insight on the device.
@@PacificYachtSystems like this? www.st.com/resource/en/application_note/dm00024664-schottky-diode-avalanche-performance-in-automotive-applications-stmicroelectronics.pdf
Jeff, Does a $35.00 Balmar Alternator Spike Protector keep your alternator safe from these possible unintended battery disconnections?
Yep, it does work.
Should my boat isolator turn off my running engine?
Boat isolator is on the output of the alternator. Battery isolator should not cause your engine to stop working.
Great content
Thanks for the feedback,
You have never explained why the alternator will die if battery is disconnected. You have stated many times that alternator will die, but never why.
The alternator dies because the high amperage output is suddenly interrupted, causing a voltage spike, which destroys the alternator’s diodes, and may cause internal short circuits.
@@robertschulke1596 I know that (30 yrs as EI&C Design Engineer)…but most do not know. Suggesting Jeff explain the why.
@@borysnijinski331 not terribly technical. It’s the same principle as the ignition coil in a make and break engine. Current through a conductor produces a magnetic field around the conductor. Cut the current suddenly, and the field collapses, inducing voltage in the conductor. In an ignition coil, 50,000 volts is normal. In an alternator, I don’t know, but I’d hazard a guess at several thousand volts. This can be easily demonstrated by energizing an electromagnet with a battery, then disconnecting it. When the connection is broken, a spark will be produced.
Thanks for the suggesting Borys, will bring it up in a future video.
My switch got out in the off position while running down the lake, and now boat won’t start. Any suggestions ??
I like your videos but you tend to exaggerate and make a lot of things sound much worse than they really are! You said that if you were to turn your battery switch off for even a millisecond it would blow your alternator, That is total BS! I know for a fact that if you were to rotate your switch past the off position it is not guaranteed you will blow your alternator, What you should have said is it is not recommended and you could end up hurting the alternator! I have done it at least a dozen times after having my alternator rebuild in 2001! My boat is a 1987 so I had the starter and alternator rebuilt in 2001 solely due to age, Here we are in 2023 and that alternator is still on my engine! You really make boating sound like it is all work and nothing but problems! I am from New Jersey and my boat has been docked in salt water from May through September ever since I bought it in 1995, My boat gets used once in a while after work during the week as well as every weekend! Boating is very enjoyable as well as relaxing, Most of the problems with boating is almost always caused by the current or former owner!