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Another battery switching question

Old 11-27-2017, 06:54 PM
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Default Another battery switching question

Original post was lost due to timeout. This one will be shorter.


Fighting with battery charging issues and load.


2000 Grady-White with twin outboards and two battery banks/two battery 1-2-both switches. I'm replacing original charger and adding a battery monitor.


Modern method is one 1-2 on-off switch to two starting batteries and ACR to a house bank. I can do this but with a lot of expense and headache. Would make firing this things up easier though.


I read here that two engines charging a single battery is an issue. Why? The factory installation switches allow me to do this. What's wrong with keeping the two original 1-2-both switches and charging either bank with either, or both, engines?


Chris
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Old 11-28-2017, 12:52 AM
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Hello, in theory there is nothing wrong with the setup you have, as long as you are on top of your switching strategy, there always exists the possibility of running batteries down when they are used for house and start. Several options exist, one is to use one battery for starting both engines and use the other motor for charging the battery for house loads, not ideal, you would still need an emergency crossover. Another simpler method is to buy a BEP marine cluster with built in charging relay, takes the headache out of charging and it separates the house and start groups, also comes with emergency crossover, neat and small solution, probably easier and cheaper than separate ACR and all associated wiring, this is based on the assumption that your outboards have no auxilliary charging capability. Hope this helps.
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Old 11-28-2017, 04:34 AM
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Originally Posted by chris.817 View Post
I read here that two engines charging a single battery is an issue. Why?
Why are false or inaccurate statements posted? That's life....
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Old 11-28-2017, 03:34 PM
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I'm not sure what your question is. you're trying to add a house bank? and battery monitor?

leave the two 1,2,all switches. so each one feeds one engine. with the ability to run each engine off each battery. then always run each engine off it's own battery unless there is an issue. (ie port engine swtich set to battery 1 and stb engine switch set to battery 2) assuming they are wired right.

then add house bank and new on / off swtich. move all non engine loads to new swtich / battery. add 2 acrs'. one between each engine battery and house battery.

if you only want to stay with 2 banks and 2 swtiches then you'll need 2 battery monitors. as you're be able to draw off either one.
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Old 11-28-2017, 07:35 PM
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Originally Posted by smac999 View Post
I'm not sure what your question is. you're trying to add a house bank? and battery monitor?

leave the two 1,2,all switches. so each one feeds one engine. with the ability to run each engine off each battery. then always run each engine off it's own battery unless there is an issue. (ie port engine swtich set to battery 1 and stb engine switch set to battery 2) assuming they are wired right.

then add house bank and new on / off swtich. move all non engine loads to new swtich / battery. add 2 acrs'. one between each engine battery and house battery
.

if you only want to stay with 2 banks and 2 swtiches then you'll need 2 battery monitors. as you're be able to draw off either one.
This is the cheapest way to do it Add a switch, 2 ACRs and some minimal wiring. I would change one thing in smac's advice and that would be to use a 1/2/all/off switch on the house bank and run a lead back to the cranking batteries to crank the engine(s) with the house bank in an emergency. .

I think part of the belief that two alternators charging a single battery could be a problem is the theoretical possibility that one of the alternator/regulators is more sensitive and that would cause one alternator to take the big part of the load while the other alternator loafs along doing little. I have never seen that be a problem in the real world.
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Old 11-29-2017, 06:04 AM
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Whether the charging outputs of two separate outboard engines can be connected in parallel without harm depends on the design of the charging outputs.

I can tell you from (expensive) first-hand experience that connecting two outboard engine charging units in parallel to charge a common battery will result in damage, however I will qualify that as occurring with a particular brand and particular model. I did not experiment further with this because the cost of repairs was too high and my curiosity was not sufficiently great to fund further experimentation. I have not tried operating every possible brand and model of outboard engine with two engines having their charging outputs wired in parallel, and I don't think too many other participants here have, either.

What I observed was that the stator coil of one engine failed when operating in parallel. I don't have a good theory for the cause, but after paying for two repairs of failed stator coils, I stopped. The two engines have since been running for more than a decade, happy to charge their own isolated battery, and no failure of the charging system. Again, if you want more conclusive results, feel free to fund your own experiments.

You should feel completely free to accept advice from the internet that no harm will occur and connect the outputs of your two separate engines together. But, if you do, please let us know the outcome after operating the engines with their charging outputs in parallel for extended periods of time.

Last edited by jhebert; 11-29-2017 at 06:10 AM.
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Old 11-29-2017, 06:29 AM
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Originally Posted by jhebert View Post
Whether the charging outputs of two separate outboard engines can be connected in parallel without harm depends.....
sage advice.

FWIW, this is from a Yamaha technical guide:

Name:  battery_wiring.png
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but I understand there are "off-brand" motors available
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Old 11-29-2017, 07:02 PM
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I'm not an expert but a small outboard stator or alternator will try to supply as much current as possible to achieve a voltage. Ignoring any other loads, the battery itself will accept a certain amount of current during charging. Adding another battery to the circuit increases substantially the load on the stator or alternator, if only one engine is operating. And if one battery is faulty, you have just created a circuit to discharge the good battery, engine off. No bueno.

The other problem I see with this arrangement is how will you know if you have a failing charging device or circuitry on one motor?

Don't design around all equipment being operational. Design around equipment failures.
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Old 11-29-2017, 08:20 PM
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Originally Posted by pooleman View Post
I'm not an expert but a small outboard stator or alternator will try to supply as much current as possible to achieve a voltage. Ignoring any other loads, the battery itself will accept a certain amount of current during charging. Adding another battery to the circuit increases substantially the load on the stator or alternator, if only one engine is operating. ...
You are off on the wrong track. We are not worried about ONE engine charging TWO batteries. We are worried about TWO engines charging ONE battery.
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Last edited by jhebert; 11-30-2017 at 11:17 AM.
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Old 11-30-2017, 01:36 PM
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Sorry folks. I originally wrote a very detailed explanation of the problem, project, etc.


The current situation is that I have two battery banks. One is a single battery and one is dual batteries. Each of my switches connect to one engine (Yamaha OX66's). I normally operate with the stbd engine feeding bank 1 and the port engine feeding bank 2. This is how they are physically laid out on the boat (one bank on each side of the transom). The "house" load is connected to the stbd switch. Obviously I can switch either engine to either bank, or both, with the two switches.


My 110vac built in battery charger has failed and I have bought a new one. While I'm in there I want to install a battery monitor. As SMAC999 stated, and I didn't realize this before, the shunt for the monitor will only allow current to be monitored by one bank. I can measure voltage on two banks.


The ultimate question was whether to leave things as they are or move to either a forth battery (one battery per engine, plus the two for the "house") and use an on-off switch and ACRs, or charge one starting battery from both engines and use an ACR to charge the existing house bank.


Seems like since all of this equipment is in working order other than the charger, I should leave it alone. As far as charging one battery with both engines, in the current setup, it's just a momentary switch between 1-2-both.


One on-off would be cool but I don't guess it's worth the expense.


Thanks for all of the input.


Chris
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Old 11-30-2017, 06:29 PM
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if all of youse house loads are off a single bank. you can just monitor the one bank. commonly on 2 engine, 2 bank boats. the house loads get split to both banks. so some draw is on each. to even out the engine charging. in that case you'd need to monitor both

if the loads come off the 1-2-all swtich. then you can drain either one. by your chosing. and you'd need 2 monitors. (or make sure the swtich is always draining off the bigger one)

if all your loads are off the bigger bank. direct from the bank, not from the engine swtich. (then should have own house switch). then you could leave it as is. and monitor the bigger bank only. or change things so you end up with that.

if all your loads are on one bank. and you are draining one bank. the 2nd alternator on the small bank is really doing nothing. and having both engines charge either bank (ACR ect) would allow the bigger bank to charge faster from both engines. and is totally fine.
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Old 11-30-2017, 07:16 PM
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Dang you SMAC999. Now you have me thinking again...


Here's what happened. I spent a couple hours messing with my electronics at the dock and drained my house battery bank. Two Group 24 batteries. This should not have happened which leads to the fact that my battery charger is not working and maybe my battery bank is in need of service. All three batteries are about a year old. And leads me to want to monitor my batteries.


The entire house load is currently on a 40A breaker attached to one switch. I can choose to pick bank 1-2-both. One engine is attached to one switch, the other to the second. I normally charge the small bank from one engine and the larger bank from one engine. In my mind, I am charging the house off one engine and the smaller starting battery off one engine. If I drain my house I still have a fresh starting battery. If all is working and one engine (35A alternator) is keeping up with the house load while everything is running all is good.


You bring up the point of charging the larger bank with both engines (70A total). That would be ideal and leave the starting battery un-touched and tons of capacity for the larger house bank. That brings me back to the original question...


Assume I leave the dock with both banks fully charged. Both engines started and running. I can, today, put both switches in the "1" position and both will charge the larger house bank and the "2" battery is out of the loop and ready for starting duty if required. BUT, now I'm charging one battery with two engines. An issue according to some here. Yet specifically built that way by Grady-White.


So back to the original question: Is it safe to charge a 170AH bank from two engines directly connected (through switches) or not? Is it a question for Yamaha? I suppose it would be simple to leave things the way I'm doing it and add one ACR from the starting battery to the house battery and combine the charging power of both engine to the house bank without both alternators directly attached to one battery. Is that a happy medium?


I'm happy to completely re-do this setup. It's really not that much money, I love this type of work, and am perfectly capable of doing it. But... shopping for all new electronics at the same time so the less costly path at this point would be good too.


Chris
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Old 12-06-2017, 04:51 AM
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Select your setup here at the Blue Sea site and review your options:

https://www.bluesea.com/resources/17...l_Applications

BTW, I highly recommend a system that allows you to just turn the battery switch On and doesn't require any other action from you unless there is a problem.

Good luck

Last edited by fly186; 12-06-2017 at 05:51 AM.
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