Wiring plan critique

[JTPearson]

Mainesail, many thanks for your posts and advice. Absolutely invaluable! Could you take a look at my wiring which I completed Saturday and let me know if you see anything wrong? The Victron battery monitor is a 602 model.
Also I noticed a 10 gauge wire run from the engine ground to the battery. I believe this was done originally from the factory. Isn't it redunant?
Is it okay to run the battery charger to the #2 (reserve) battery since I have a Blue Seas ACR installed?

Again many, many thanks!! You really should write a book!

 

[sailor2002]

Your plan for wiring appears sound. I see you wish to charge from the battery charger to battery # 2 (assume that may be a house battery) Battery one or two can be selected for house or start battery. Care must be taken not to switch the battery switch while the engine is running. The ACR will connect the two batteries when the voltage reaches the specified volts. check that this works for you and that it opens at the voltage you want. remember the amps cross over from one battery to another. this load changes based on the voltage difference. it can be up to 100 amps at times. enjoy.

 

[Maine Sail]

Your plan for wiring appears sound. I see you wish to charge from the battery charger to battery # 2 (assume that may be a house battery) Battery one or two can be selected for house or start battery. Care must be taken not to switch the battery switch while the engine is running. The ACR will connect the two batteries when the voltage reaches the specified volts. check that this works for you and that it opens at the voltage you want. remember the amps cross over from one battery to another. this load changes based on the voltage difference. it can be up to 100 amps at times. enjoy.

His alternator is routed directly to the house bank. He can move the battery switch with no effect to the alternator as it will always see the "load"..

 

[sd1953]

The schematic shows a 10 ga. wire from the battery to the boat ground as well as a 1/0 wire to the shunt and then on to the ground. Would this configuration allow for a loop current to exist? Why have the two paths to ground? Is there an advantage I am unaware of to the two path configuration?

 

[JTPearson]

That is my question! The 10 gauge wire was original from the factory (at least that is what the Catalina manual shows). I think it is redunant as the 1/0 cable performs the same function.

 

[Stu Jackson]

Nice diagram. How big is your alternator? How big is your house bank? The AO wire, 8 ga. seems small. If you have any possibility of installing a larger alternator in the future, increase the wire size now, save effort then.

Show fusues. Consider an on/off switch in the AO wire to be able to easily disconnect the alternator when working around the engine (or just remove the fuse).

 

[Maine Sail]

Here's what I notice.....

#1 The 10GA wire is not necessary as the 1/0 engine neg cable takes care of that.

#2 8GA is awfully small for a machine sensed alt especially if you ever up-size. A neg cable the same size as the + should route directly to the 1/0 engine neg cable and be "stacked" directly onto that lug or a bus bar should be used. Case grounds are horribly unreliable in the marine environment. A clean dedicated neg wire and connection is critical to performance.

#3 The battery charger neg wire MUST go to the LOAD side of the battery monitor shunt (which it technically does). NOTHING should be on the battery side of the shunt but the house battery neg terminal. I only mention this because it is easy to mess up.

#4 If bank #1 is HOUSE then both the alt and the battery charger + should be fed there. I am assuming from the shunt wiring that bank #1 is HOUSE and bank #2 is START/RESERVE. If so the battery charger and alternator positives should both be led to the house bank.

#5 You need over current protection within 7" of the positive house bank battery post. You would be best served to also have the "start" or "reserve" battery fuse protected.

#6 There needs to be a fuse within 7" of the "C" post for the DC panel feed wire.

#7 The ACR needs to be fused within 7" of the battery terminals unless 1/0 wire is used and the ACR is on the load side of the battery OCP.

#8 No wire gauge is shown for the ACR?

#9 The alternator needs OCP within 7" of the battery.

#10 An alternator service disconnect switch or thermal breaker should be considered in the engine bay to isolate the alt when working on the engine.

#11 The battery charger needs OCP within 7" of the battery

 

[JTPearson]

Stu, thanks for your input and questions! Orignial Motorola alernator, 51 amp.
All cables are fuses with MRBF. The 8 gauge is fused with a 70 amp AGC fuse.

 

[JTPearson]

MS, not really sure what you mean when you say, "A neg cable the same size as the + should route directly to the 1/0 engine neg cable and be "stacked" directly onto that lug or a bus bar should be used. "

I am running a 1/0 cable from the Shunt to the engine ground. If the 10 gauge is not needed why stack it? Unless you are talking about the alternator.

 

[Maine Sail]

MS, not really sure what you mean when you say, "A neg cable the same size as the + should route directly to the 1/0 engine neg cable and be "stacked" directly onto that lug or a bus bar should be used. "

I am running a 1/0 cable from the Shunt to the engine ground. If the 10 gauge is not needed why stack it? Unless you are talking about the alternator.

I am talking about the case grounded alternator. Case grounds on boats SUCK. They force your alternator current to push through multiple poorly conductive metals, rust, paint and other high resistance bits and pieces. Taking a neg cable, the same size as positive, and running it directly to that 1/0 engine neg/ground wire can make a HUGE difference in alternator performance.

I often install a neg bus bar for the starter, alt and engine wiring to tie into and feed directly back to the battery bank or load side of a shunt.. I also prefer the engine neg cable (the 1/0 for you) to be bolted directly onto the ear of the starter motor, with the paint cleaned to bare aluminum.. This provides the least voltage drop to the starter and avoids the crappy "case ground" issues.

In this pic the neg bus bar is mounted directly to the engine bed. One wire comes from the alt and the other directly from the mounting ear of the starter. The other large wire is direct back to the battery bank. On this motor the alt B+ is just picking up the starter cable via the + jumper wire.

 

[marchem]

I am talking about the case grounded alternator. Case grounds on boats SUCK. They force your alternator current to push through multiple poorly conductive metals, rust, paint and other high resistance bits and pieces. Taking a neg cable, the same size as positive, and running it directly to that 1/0 engine neg/ground wire can make a HUGE difference in alternator performance.

I often install a neg bus bar for the starter, alt and engine wiring to tie into and feed directly back to the battery bank or load side of a shunt.. I also prefer the engine neg cable (the 1/0 for you) to be bolted directly onto the ear of the starter motor, with the paint cleaned to bare aluminum.. This provides the least voltage drop to the starter and avoids the crappy "case ground" issues.

MS, do I understand that the two options you recommend are 1) a negative busbar with cables to battery, alternator, and starter; and 2) the negative cable from the battery connected to the starter, and a jumper from there to the alternator? Are there good connection points on most alternators and starters?

I'm putting together a wiring plan to post here for comments and keep finding great ideas from you and others.

 

[Maine Sail]

MS, do I understand that the two options you recommend are 1) a negative busbar with cables to battery, alternator, and starter; and 2) the negative cable from the battery connected to the starter, and a jumper from there to the alternator? Are there good connection points on most alternators and starters?

I'm putting together a wiring plan to post here for comments and keep finding great ideas from you and others.

On the starters I clean the mounting ear to bare metal (aluminum usually) then stack a HIGH QUALITY HEAVY DUTY sealed & tinned battery lug under the starter mounting bolt. This gives a direct path for the starter motor back to the battery bank. If I am not using a bus bar I will also stack the alt wire there as well. This may require a longer starter mounting bolt.

For case grounded alternators there is always a spot for a neg cable but be sure it is clean metal. On isolated ground alts use the Neg stud.

 

[marchem]

On the starters I clean the mounting ear to bare metal (aluminum usually) then stack a HIGH QUALITY HEAVY DUTY sealed & tinned battery lug under the starter mounting bolt. This gives a direct path for the starter motor back to the battery bank. If I am not using a bus bar I will also stack the alt wire there as well. This may require a longer starter mounting bolt.

For case grounded alternators there is always a spot for a neg cable but be sure it is clean metal. On isolated ground alts use the Neg stud.

Thanks. That makes perfect sense. I'm trying to decide how elaborate to get on our Catalina 27. Almost anything would be better than the current wiring, but deciding when a busbar (or an alternator disconnect) is needed is tough, especially since space and access in the engine compartment is minimal.