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Wiring Diagram Needed-1 Engine, 2 Switches, 3 Batteries

27K views 19 replies 7 participants last post by  Compujedi 
#1 ·
I'm trying to figure out how to wire my batteries and switches. I purchased my sailboat used and I don't believe it's wired properly so I want to start from scratch. I have the following:

1 Diesel engine (thus 1 alternator)
2 Perko switches (Off, 1, All, 2)
3 batteries (8D AGMs)
1 ProMariner 1240i Plus 3-bank battery charger

This is what I see the batteries "task" as:

#1 Starting
#2 Electronics, lights, etc.
#3 Refrigerator, 2500W inverter

Any help would be MUCH appreciated.

Thanks...
 
#2 · (Edited)
Just curious, why do you need three battery banks. You'd be much better off with just two. If you're planning on using an 8D for a starting bank, you're not thinking too clearly. You don't need an 8D to start most small sailboat diesels. You'd be far better off getting a group 31 for the starting battery and using the three 8Ds as a single house bank.

OF course, a lot of this depends on what kind of boat and engine you have. It would probably be wise to give all the relevant information when asking questions in the future. I'd also recommend you read the POST in my signature to help you get the most out of your time on sailnet.

There are a couple really good reasons for not splitting the housebank into multiple banks as you're suggesting. First, is the Peukert factor. If you have two single 8Ds as a battery bank, you're going to get less usable hours from them than if you have the exact same loads on a single bank of two 8Ds. This is because the load is higher relative to the bank size when the batteries is split into two separate banks.

This is the same reason a battery has a 5 hour and a 20 hour amp-hour rating, and the 20 hour rating is always significantly higher than the 5 hour rating. The second is that the batteries are going to be harder to maintain if they're in separate banks.

Second, if they're in the same bank, they'll get roughly equal usage and undergo equal charge/discharge cycles. If they're in three separate banks, they'll each have different use and charge/discharge cycles...

As for charging... what I'd recommend is connecting all the charging sources-alternator, ProMariner, etc-to the house bank and then connecting a BlueSea ACR, or DuoCharge or EchoCharger to keep the starting bank topped off. There's really no reason to charge the starting bank separately.

I'd point out that the ProMariner 1240i is really quite undersized to handle THREE 8D batteries, which will create a battery bank of 600 amp-hours or so. Generally, the charger should be sized at least at 20-25% of the bank size. This is more so the case if you're using AGM batteries, which have a very high current acceptance rate during the bulk charging phase and could easily draw enough to shorten the life of your alternator, and possibly the ProMariner, depending on the charger design. A bank of THREE 8D AGM batteries may have an acceptance rate of over 200 amps during bulk charging if you've got the capacity to supply that much current.

However, without more specific information, such as what alternator you have, whether it is internally or externally regulated, what engine you have, etc., it is hard to say more.
 
#3 ·
I would also combine the batteries into one 600ah bank--not only is it more efficient, but the batteries will last longer. You can do that with the switches you have now, which will also let you isolate any battery if it fails.

There is a school of thought which says you should also have a separate starting battery, but I've been using one bank for over 15 years, and never had a problem starting the engine, even after one battery had a shorted cell. However, I have alternative sources of charging, like solar and wind. A honda generator would also serve as a backup.
 
#4 ·
Thanks for the replies. Let me see if I can answer all the questions.

The boat it is a 1983 Vagabond 42. The engine is a Yanmar 75 hp 4JH-DTE from around 1985ish. I have no idea about the alternator as I don't have pictures and I'm not at the boat at the moment. Looking at the Operations Manual for the engine shows it as a 12V 55 amp alternator (how regulated unknown). All the equipment mentioned above (except the ProMariner) came as is with the boat and is how I 'think' it is currently wired as the wiring is a mess and I haven't started taking things apart...yet. The ProMariner replaced the original 3-bank 30amp charger that was in the boat. True the 8D is overkill for a starting battery but it was in the boat when I got it so it will stay until it dies (it's about 5 years old) and then I'll replace it with a smaller starting battery.

Two of the batteries (#1-starter and #2-electronics/lights) are located next to the engine (under the steps about in the center of the boat). The #3 battery is located about 2/3 forward underneath a port settee and runs only the refrigerator and the 2500W inverter (both which are right beside the battery)...as far as I can tell.

I'm open for some good options on how to cheaply simplify this configuration. I definitely want the #1 starter battery to remain the main starter battery but be able to select the others if it dies. A wiring diagram showing alternator, ProMariner Charger (using 2- or 3-bank depending on your design), 2 Perko switches, 3 batteries, and possible BlueSea ACR if added, would be worth a thousand words :) Thanks again.
 
#5 · (Edited)
Ok... what I would recommend is taking two of the 8Ds and forming a two-battery house bank with them. If you can fit them both under the Port Settee, that would make wiring a bit simpler. Leave the Starting 8D as the start bank.

To get maximum flexibility, I would recommend getting the additional hardware:


Then wire up the batteries as follows:



What this allows you to do is pretty neat. It allows you to isolate any one of the three 8D batteries and use it either for the starting bank as well as the house bank.

Normal Operation:

  • Leave Perko #1 in the BOTH position
  • Perko #2 in the #1 position
  • Put the DCP in the ON position.

What this does is isolates the starting system to the starting battery (#3) and the house system to the house batteries (#1 & #2).

Dead House Battery

  • Turn the Perko #1 switch to 1 or 2 to isolate the dead or damaged house battery.
  • Perko #2 in the #1 position
  • Put the DCP in the ON position.

Basically the same as the first setup, but only using one of the two house batteries as the house bank, isolating the other.

Dead House Battery Bank

If both house batteries are dead and you need to start the engine and run the house loads off the starting battery, do the following:

  • Turn the Perko #1 Switch to OFF. This takes the dead house bank off-line.
  • Put DCP in ON position
  • Put the Perko #2 switch in the #1 position and start the engine with Battery #3.
  • Once the engine is running, then turn the DCP switch to the "BOTH" position to run the house loads off of Battery #3.

This allows you to start the engine without any house loads on the starting battery and then add the house loads to the electrical system once the engine is running. The starting bank will charge via the DCP.

If the house bank is dead due to just overuse, rather than damaged batteries, you can then turn Perko #1 to the Both position to get the batteries to charge. Once Batteries #1/#2 have charged a while, you should be able to turn the DCP back to the "ON" position. The starting battery will continue to charge via the ACR.

Dead Start Battery

If the start battery #3 is completely dead or damaged, you can start the boat still by doing the following:

  • Leave DCP in OFF position
  • Turn Perko #1 to 1, 2 or both, depending on the state of charge and condition of batteries #1 and #2.
  • Turn Perko #2 to the 2 position, which will connect the house bank to the starter motor.
  • Start engine
  • Turn DCP to ON position to connect HOUSE BANK to House Loads
  • Turn Perko #2 back to position 1, if the starting bank is just dead, but not damaged.

This allows you to start the boat using the House Bank, either #1, #2 or both #1 & #2, then run the house loads on it once the engine has started. If the starting battery is just dead from overuse, it will start to charge via the ACR. If it is damaged, you will want to disconnect the #3 battery before starting the engine.

All charging sources go to the house bank normally, but can be put on the starting bank in the case of a dead house bank by turning the DCP to BOTH. While this setup is a bit complicated, it does give you complete redundancy and the ability to isolate any of the three batteries, use any of the three batteries for house or starting loads, and keep all the batteries charged. The TWO RED LINES WITH ARROWHEADS are the common lines coming off the Perko switches.
 
#7 · (Edited by Moderator)
I have a set up that is similar to what sailingdog drew, but is less complicated. I have all of my charging sources going to my house bank of 2 group 31 batteries. I have a group 24 starting battery. My house bank batteries are connected via a 1, both, 2 off switch that goes to a positive bus. I have a Blue Sea ACR that connects the positive house bus to the start battery positive bus. I have just added an on/off switch to bypass the ACR (had a learning experience this past weekend that required jumper cables).

This allows me to parallel the house batteries during normal operation and isolate one of them if needed. It also allows me to easily disconnect them while doing electrical work. The ACR will connect the house and start banks to charge the start bank when the house bank is above a certain voltage that I cannot remember. If your start bank is to drawn down to start the motor and your house bank is below that certain voltage the on/off switch will allow you to manually parallel the house and start banks.

The draw back to this system is if the start battery is bad I cannot use the house bank to start the motor without first disconnecting the start battery. This is a rare situation and, in my opinion, not worth adding a second 1, both, 2, off switch to allow for total redundancy.

The ACR/combiner switch package costs around $125.
 
#8 ·
I see a fun winter project ahead of me. I'm tempted to yank all the existing wiring out and start from scratch which will probably be the smart and easiest thing to do. Some of the battery terminals have far too many wires attached to them.

For sailingdog - THIS IS GREAT and just want I was after. There isn't a bus bar on the boat so you can imagine the 'stuff' that is connected directly to the batteries. Right now I don't think there is a fuse in the entire boat either. I'll have to figure out what size fuzes to install. I definitely appreciate the time you've spent on this.

For Stu Jackson - Thanks for the links. Both helped understand matters a little clearer.

For nickmerc - An on/off switch was difinitely on my mind for awhile. I think eBay is about to be my friend on finding an ACR/combiner switch and other goodies.

For donradclife - I like the idea of these NOT very cheap batteries lasting longer. The price tag on them says $325 which was 5 years ago. Why the prices have gone up $100 or more is beyond me. Solar and/or wind are definitely on the horizon I think.

Thanks again for the assistance and ideas!!!
 
#10 ·
That wire definitely will be the expensive part no doubt. I've already got the DCP and ACR. My last question (ok for the moment). My batteries (3 8D AGMs) are each 245 AH (1725 MCA and 1350 CCA). The alternator is 80 amps (went to the boat to check) and battery charger is 40 amps max. With the diagram from sailingdog (I've decided on basically his configuration), what size fuses and what ampherage bus bars should I use? Wire gauges will have to wait until I see how long each run is. Again, I appreciate all the help.
 
#11 ·
In general, the fuses are sized to protect the wiring. Unless you know the distance run and the gauge, you won't really have a good idea of what size fuse to use. As for the bus bars, that is pretty much determined by the size of the DC circuit breaker panel you're using.
 
#13 ·
Yup...without knowing the run length and rough amperage load, there's no way to determine what size wire is being used or what the fuse size should be... need to get more info first. :D
 
#14 ·
i picked up the boatowners illustrated electrical handbook last week. I'm about halfway through and its helped a lot. isbn 978-0-07-144644-0

i also picked up a good quality clamp ammeter. so now i can check to see if something is working without pulling it off and dragging it to the electrical place.

the PO of my boat had her wired for 16 batteries in 4 seperate banks with redundant everything... so i have a lot of learnin to do.
 
#15 ·
Just how big a boat are we talking about? 16 batteries in FOUR HOUSE BANKS is really stupid and requires a really big boat.
 
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