Twin Engine Charging

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Nsail

Nsail

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Joined
Mar 2, 2012
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499
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USA
I'm having some electrical work done on my boat and am using a local, highly recommended marine electrician. He told me that my current charging system is not the most efficient as is, and is recommending that it be changed.

He says that the best way is to have one alternator charge the start batteries and the other alternator charge the house bank batteries. I have a generator in case I can't run one of the engines for whatever reason, so theoretically I should never be "stuck" (that is obviously if the generator is working OK).

I've searched on the forum already for this answer and found some information, including the current ProIsoCharge thread but it's still not totally clear to me if what he recommends is best, or if it's even a typical charging setup (assuming I don't use the ProIsoCharge or something similar).

And, I figured it would be better to start a new thread rather than muddying up the waters on the ProIsoThread.

Sorry if this seems to be a dumb question, but your thoughts on whether what he is recommending is the best system, a typical system, or something else, would be greatly appreciated.

Thanks!
 
Its hard to imagine a situation where what your highly respected advisor is recommending would be the best choice. You haven't told us enough about your installation to give you much advice but assuming you have a house battery bank that is larger than your starting bank the advice you are receiving is just plain silly. Even with similarly sized house and starting banks I could make a good case for having dual alternator charging capability on the house bank.

Tell us what your current charging arrangement is and what you have for battery banks and I'll be more specific.

And just in the interest of full disclosure, I can count on the fingers of one hand the people I have met personally whose advice I would trust in this matter. There are a host of charlatans masquerading as marine electricians, including some who post regularly on this forum. The only way you can protect yourself is to amass enough knowledge to make the decisions yourself, even if you ultimately hire someone to do the work.
 
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There are many ways to wire a boat. The more engines, alternators and battery banks and the possible combinations go through the roof.

Many boats are set up the way you are describing it. Some have a third alternator...one for each engine batt and one for the house bank (usually a super-sized alternator.)

There are many combinations of switches and solenoids that allow you to manually charge whatever bank you want, whenever you want...there are also systems that allow it to be done automatically.

There are arguments for where switches should be placed in case of fire and there's even decent discussions whether to switch in the hot leads versus the grounds.

Sorry but theres no one way, best way, etc...etc..

You have to have some idea of what you will live with and not, design a couple of "ideal" systems in your mind (or let a pro do it), pick one and then have it installed with the best materials and experience you can afford.
 
Thanks for your reply Bob. I was afraid someone would ask questions! Please understand that this part of boating is pretty new to me so please be gentle.

At any rate, the house bank is 1000 amp hours (10 batteries) and the 2 start batteries are 8D's. It's supposedly wired now as a smart system that automatically takes care of everything. But, the house batteries won't stay charged very long (or as long as they should) and they're supposedly good (a couple of years old).

He's explained to me (as I understand it, so please don't quote me) that because the batteries are different types and wired in such and such a configuration that the regulators are overcharging some of the batteries and undercharging others. He thinks that simplifying things would be better and that it's common to configure things this simpler way.

My uninformed mind tells me otherwise (I'm thinking ProIsoCharge).

Thoughts? (other than - you dumbass, you shouldn't even own that boat!)
 
Our boat is set up exactly the way you described. The port engine's alternator charges the port battery bank (house)' the starboard engine's alternator charges the starboard battery bank (start).

Placing the battery selector switch in All combines the output of both alternators to charge both battery banks simultaneously. One alternator is set up to spin faster than the other one which apparently prevents any conflict between the alternators. For a reason too lengthy to explain here we used to run the boat this way when we had two 8D batteries. After engine shutdown we would switch the selector to 2 to isolate the house and start batteries.

Now that the 8Ds have been replaced with banks of 6vdc golf cart batteries we no longer have any need to combine the outputs of both alternators so we simply leave the battery selector on 2 (house) all the time and each alternator charges only its associated battery.

It's been set up this way for 40 years now and is a nice, simple, reliable setup.
 
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Nsail said:
My uninformed mind tells me otherwise (I'm thinking ProIsoCharge).

Thoughts? (other than - you dumbass, you shouldn't even own that boat!)
Click to expand...

You're no dumbass - you wouldn't be asking the questions if you were.

I posted this link on the other thread. I think its a good primer to start to understand some of the issues around charging and different battery technologies. Your start batteries are important - without them you don't go anywhere. But they don't need much recharging. Assuming normal starts they get drawn down a very small amount (given that they are 8Ds they get drawn down a VERY small fraction of their total capacity) and then they need to be topped up again. Your house bank on the other hand is relatively large and it could easily be down to 70% or even lower by the time you start recharging it. To me that means that using one engine to charge one bank is just silly.

I'm also a big fan of K.I.S.S. I haven't bothered looking up the ProIsoCharge gizmo you referenced because I don't think any of that nonsense is needed by the average boater. Further I think that adding automatic gadgets just compounds the problems that you will eventually have to troubleshoot when you should be sitting on the aft deck drinking wine and watching the sun go down.

I don't know what you currently have for alternators but I'm assuming identical small frame automotive type alternators, somewhere between 80 and 120 amp nominal output each. If you asked me how to wire your boat economically and simply I would tell you to tie the output of the two alternators together with an external regulator like the Balmar 614 and use a Xantrex Echo Charger to charge the start batteries. If you do that right your shorepower will also keep the start batteries topped up while charging your house bank. More importantly it will direct the combined output of both alternators to refill your house bank much more rapidly than a single alternator ever could.

There's one basic caveat that applies. Hopefully you will figure this out from the reading assignment :D but just in case: each bank needs to consist of identical batteries of identical age. No problem having different batteries in the individual banks but within the banks they all gotta be equal.
 
While reading this thread I looked over the wiring diagram of my boat which I made after doing some electrical work a couple of years ago.
Engine 1 alternator sends charge to post 1 on the battery selector switch which is connected to my 5 battery house bank.
Engine 2 alternator sends charge to post 2 on the battery selector switch which is connected to my single 105 AH battery start battery.
When running the boat I select BOTH on the battery selector switch so both banks charge, unless I know the house bank is low due to being at anchor overnight, in which case after I start the engines I switch to position 1 on the battery selector switch so both engine alternators charge the house bank. At least I think this is what happens.

This is the ultimate in KISS. I have to remember to monitor my battery voltage and make sure I switch to the house bank when at anchor.

I do have a third isolated bank used only for generator starting.

Comments are welcome.
 

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bobofthenorth said:
You're no dumbass - you wouldn't be asking the questions if you were.



I'm also a big fan of K.I.S.S. I haven't bothered looking up the ProIsoCharge gizmo you referenced because I don't think any of that nonsense is needed by the average boater. Further I think that adding automatic gadgets just compounds the problems that you will eventually have to troubleshoot when you should be sitting on the aft deck drinking wine and watching the sun go down.

I don't know what you currently have for alternators but I'm assuming identical small frame automotive type alternators, somewhere between 80 and 120 amp nominal output each. If you asked me how to wire your boat economically and simply I would tell you to tie the output of the two alternators together with an external regulator like the Balmar 614 and use a Xantrex Echo Charger to charge the start batteries. If you do that right your shorepower will also keep the start batteries topped up while charging your house bank. More importantly it will direct the combined output of both alternators to refill your house bank much more rapidly than a single alternator ever could.

There's one basic caveat that applies. Hopefully you will figure this out from the reading assignment :D but just in case: each bank needs to consist of identical batteries of identical age. No problem having different batteries in the individual banks but within the banks they all gotta be equal.
Click to expand...

OK, on one hand you dismiss the need for a gizmo and complication, then you recommend a solution that requires at least two gizmos instead. So really you are just pitching your particular pet gizmos and complications, not that that's a bad thing.....
 
caltexflanc said:
So really you are just pitching your particular pet gizmos and complications.....
Click to expand...
:D:D
That's funny, it's hard to get away from the little boxes. I sent an email to my electrician this morning after reading this thread. I'm wiring from scratch so I will be reading this thread to see what ideas pop up and what makes since. Paul
 
bobofthenorth said:
............. The only way you can protect yourself is to amass enough knowledge to make the decisions yourself, even if you ultimately hire someone to do the work.
Click to expand...

That's like telling someone he needs a medical degree before having surgery.

Tjere's no way a layman can amass enough knowledge about everything in life he or she needs to make decisions on.

The best you can do, marine electric or anything else is to find someone who is highly respected in the field, and has many satisfied customers. Talk to a couple others if you wish. Decide which one to trust with your boat.

There is no one best way to wire a boat, there are too many variables. Post your question on a web forum and you'll get ten different recommendations. Now what? Who do you believe?

BTW: Telling your highly respeced local marine electrician that you want it done the way strangers on a boating forum say it should be done instead of the way he recommends it is not a great idea.
 
Nsail said:
I'm having some electrical work done on my boat and am using a local, highly recommended marine electrician. He told me that my current charging system is not the most efficient as is they never are if you ask an "expert", and is recommending that it be changed. Thanks!
Click to expand...


I'll come at this a different way, why do anything? You have not indicated any problems with the existing setup. (hopefully it will remain that way after the electrical guy is finished).

One piece of previous advice for sure is spot on - your house batteries should be matched for type, age and brand.
 
Nsail said:
I'm having some electrical work done on my boat and am using a local, highly recommended marine electrician. He told me that my current charging system is not the most efficient as is, and is recommending that it be changed.

He says that the best way is to have one alternator charge the start batteries and the other alternator charge the house bank batteries. I have a generator in case I can't run one of the engines for whatever reason, so theoretically I should never be "stuck" (that is obviously if the generator is working OK).

I've searched on the forum already for this answer and found some information, including the current ProIsoCharge thread but it's still not totally clear to me if what he recommends is best, or if it's even a typical charging setup (assuming I don't use the ProIsoCharge or something similar).

And, I figured it would be better to start a new thread rather than muddying up the waters on the ProIsoThread.

Sorry if this seems to be a dumb question, but your thoughts on whether what he is recommending is the best system, a typical system, or something else, would be greatly appreciated.

Thanks!
Click to expand...

I reconfigured our system very much like what your electrician recommended, but swapped the original 55 amp alternator on one engine to a 150 amp unit with an external smart regulator to service the golfcart house bank. The original 55 amp alternator on the second engine is dedicated to the two paralleled group 27 start batteries (which I can separate to start individual engines via an interconnet switch). A Blue Sea device sends charge current to the genset battery after the start batteries are topped off.

I originally used the Blue Sea device to send charge current from the 55 amp alternator to the house bank after the start batteries were topped off, but discovered that the higher voltage signal from the "stupid" regulator would "take charge/overpower" the smart regulator and shut down the 150 amp alternator (and the tach on that engine).

There are no switch manipulations required to keep everything charged. The original 55 amp alternator that was removed serves as a spare.
 
Nsail said:
He says that the best way is to have one alternator charge the start batteries and the other alternator charge the house bank batteries. I have a generator in case I can't run one of the engines for whatever reason, so theoretically I should never be "stuck" (that is obviously if the generator is working OK)
Click to expand...

Interestingly enough, this is exactly what I do, and I have a single engine. I have two identical alternators on the main engine; one charges the house bank and one charges the start bank. There is a combiner switch that will allow the two banks to be combined in the case of a failure of either alternator or in case the start bank becomes discharged (which should never be possible, because it has no loads).

As Marin points out, this is a dead-simple and dead-reliable system. No isolation devices, no 1-2-Both switches, no messing around.

In your particular situation, I would be considering upgrading the alternator that charges the house bank to a high-amperage unit and associated regulator. I used Ample Power and have been very happy with their products and service, but Balmar is good too.

Scott Welch
Island Eagle
 
Nsail said:
Thanks for your reply Bob. I was afraid someone would ask questions! Please understand that this part of boating is pretty new to me so please be gentle.

At any rate, the house bank is 1000 amp hours (10 batteries) and the 2 start batteries are 8D's. It's supposedly wired now as a smart system that automatically takes care of everything. But, the house batteries won't stay charged very long (or as long as they should) and they're supposedly good (a couple of years old).

He's explained to me (as I understand it, so please don't quote me) that because the batteries are different types and wired in such and such a configuration that the regulators are overcharging some of the batteries and undercharging others. He thinks that simplifying things would be better and that it's common to configure things this simpler way.

My uninformed mind tells me otherwise (I'm thinking ProIsoCharge).

Thoughts? (other than - you dumbass, you shouldn't even own that boat!)
Click to expand...

If you think buying such and such device will solve your problem, dismiss the electrician and buy the device. Other than that, you haven't provided sufficient information (" because the batteries are different types and wired in such and such a configuration that the regulators are overcharging some of the batteries and undercharging others.") for anyone on a web forum to suggest any better setup. How did things get wired this way? Factory, previous owner, or you?

From the information you've provided, I think having the electrician wire it as he suggests is the best option. If you have more information you've neglected to post, that could change things.
 
By the way, I have, not counting the Whaler, 15 batteries on my boat, the smallest being a group 31 AGM to start the generator. Four L16 Trojans for the inverter, two 8D for the thruster and a couple small 24 volt loads, 8 D-Sized 8 volt batteries, 4 chargers (including the inverter), two alternators plus the feed off the generator. We lived full time on moorings and at anchor for months at a time and almost 20,000 miles of cruising with all this. My batteries get hammered and last as long as anyone's, if not longer, in terms of cycles and total draw downs. But what do I know?
 
Last edited by a moderator:
caltexflanc said:
By the way, I have, not counting the Whaler, 15 batteries on my boat, the smallest being a group 31 AGM to start the generator. Four L16 Trojans for the inverter, two 8D for the thruster and a couple small 24 volt loads, 8 D-Sized 8 volt batteries, 4 chargers (including the inverter), two alternators plus the feed off the generator.
Click to expand...

George:
I recall reading an article in the Juneau paper about a power outage at Angoon, on Admiralty Island, last summer. The paper said that a Trawler Cruiser pulled up to the pier and powered the hospital until the power could be restored. Was that you? :hide: :D
 
Nsail said:
........... But, the house batteries won't stay charged very long (or as long as they should) and they're supposedly good (a couple of years old)...........
Click to expand...

If the house batteries won't stay charged very long, I would be looking for something that's drawing a current continuously. A light left on, a florescent light left on but with a burned out tube, a partial short from a positive wire to water in the bilge, a defective piece of electronics or defective appliance, etc.

Turn off everything, then disconnect the negative lead from the house bank and insert an ammeter into the circuit (your electrician will know how to do this.) There should be no current draw other than the very minor current from a radio memory circuit and perhaps 1/4 amp for a CO monitor. Newer CO monitors draw much less standby current so if you have an older one, you might consider replacing it.

If you find a current draw, turn off circuit breakers one by one until you find which circuit the draw is on, then check everything that circuit powers until you find the culprit. Then, of course, repair or replace it.
 
Nsail said:
But, the house batteries won't stay charged very long (or as long as they should) and they're supposedly good (a couple of years old).
QUOTE]


  • How long?
  • Do you have a Link or other device to monitor the house bank SOC?
  • It is not uncommon to have the house bank only last overnight with normal TV, appliances and lights - before going down 30 to 50% and need to fire up the genset or run the boat.
  • A setup like your electrician recommneded is how my boat is set up too, but the house bank gets recharged before the next evening of downtime - not a big deal to do it
Click to expand...
 
I'm going with external regulators and a Balmar Centerfielder to control the two alternators and then a Duo Charge or Echo Charge for charging both house bank and start batteries. Used the Echo Charge on our sailboat for years and it worked out great, no manual selector switch to worry about.

For more than two banks, add more Echo Chargers.

Bob
 
One more comment and I'll go away. Chances are the house bank is much bigger than the start bank and requires more charging. So why put that load on just one alternator if you have two of them?

What happens if you lose an engine or alternator or decide to run (God forbid) on just one engine? You're back to flipping switches, if you remember how to set them.

Bob
 
I should have said that the house bank drops to 12.4 v within an hour. And. I've been told that I should start charging them at this level.

I've done a lot of checking and making sure things are turned off, etc. , but didn't find anything. The electrician has also.

At any rate, after reading all the responses, it seems what he is proposing is fine, and I'll just go with that.

Thanks everybody!
 
Nsail said:
I should have said that the house bank drops to 12.4 v within an hour. And. I've been told that I should start charging them at this level.Thanks everybody!
Click to expand...

How you charge your batteries will not change your at rest voltage reading. There are several types and brands of BMKs that read SOC, voltage, amps being used, amps remaining etc.
 
IslandEagle said:
Interestingly enough, this is exactly what I do, and I have a single engine. I have two identical alternators on the main engine; one charges the house bank and one charges the start bank. There is a combiner switch that will allow the two banks to be combined in the case of a failure of either alternator or in case the start bank becomes discharged (which should never be possible, because it has no loads).

As Marin points out, this is a dead-simple and dead-reliable system. No isolation devices, no 1-2-Both switches, no messing around.

In your particular situation, I would be considering upgrading the alternator that charges the house bank to a high-amperage unit and associated regulator. I used Ample Power and have been very happy with their products and service, but Balmar is good too.

Scott Welch
Island Eagle
Click to expand...

Sounds like my system, except I use two diesels to power the two alternators. I'll be installing the 120A Balmar alternator and MC-614 external regulator to finish off the system someday soon.

My alternators are wired directly to their respective battery bank. I placed the load selector switches outside of the ER to be able to access them in the event of a fire. (Note that they do NOT control or affect battery charging.) It also saved a significant wire run to the former aft salon cabinet switch location, placing the switches very close to the batteries. I haven't needed to move change switch positions since I modified the system a couple of years ago. The schematic below shows an override switch on the combiner that I will install next week. I have found that there are times (like when on shore power at my home slip) that it's not necessary to combine the banks. This switch will give me that option.

Here's my current schematic which was designed with the help of our boat works foreman who said he wished all boats were wired like this. All I can say is that it works for me.

img_141903_0_9250b89f1844e0efcc02ff6fd679e82f.jpg
 
factory charging system on 1988 501

I am new to forum and am buying 1988 501 docked in Lauderdale. We survey /seatrial soon. I noted on inspection of boat that there are two Guest battery switches in engine room. They are both numbered 1,2 all. Both switches were set to "all". No time to run down wires or read manuals ,but it bothed me as from past and current expierience, if each main engine has its own battery(bank) ,it should be charged by that engine and "all" used as jumper in case of failure(alternator or battery). I know that two alternators charging the same battery will cause regulators to bump heads and could blow diodes. How is the system from the factory? Does each engine have its own bank? Shouldn't each switch be on its own bank,eg starboard on#1 and port on#2? Gary
 
cambria lady said:
I am new to forum and am buying 1988 501 docked in Lauderdale. We survey /seatrial soon. I noted on inspection of boat that there are two Guest battery switches in engine room. They are both numbered 1,2 all. Both switches were set to "all". No time to run down wires or read manuals ,but it bothed me as from past and current expierience, if each main engine has its own battery(bank) ,it should be charged by that engine and "all" used as jumper in case of failure(alternator or battery). I know that two alternators charging the same battery will cause regulators to bump heads and could blow diodes. How is the system from the factory? Does each engine have its own bank? Shouldn't each switch be on its own bank,eg starboard on#1 and port on#2? Gary
Click to expand...

There's no reliable way to tell you how the switches should be set with the information you provided. Even if someone knew the factory wiring, there's a very good chance it has been changed since your boat was built.

If you're having trouble figuring it out, I suggest finding a local marine electrician and having him/her examine the boat's wiring and suggest how the switches should be set or possible improvements so you wouldn't have to be bothered with flipping switches all the time.
 
" But, the house batteries won't stay charged very long (or as long as they should) and they're supposedly good (a couple of years old)."


Nsail, do you equalize charge your batteries? I am a believe that the practice is good for battery health. It may help with your discharge issue. Are your specific gravities at the high end of 1.280+ after a charge?

I spent six year as a navy electrician on a submarine. The military had a regular practice of equalizing batteries and monitoring for performance.

I've read all the don't equalize responses so there is no need to re-hash that.:whistling:
Dave
 
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