Please comment on my DC wiring diagram

Stu Jackson · Jan 5, 2012

Looks fine. I'd run the combiner to the + posts of the battery banks, although you've simply tied them to the other ends of the same wires. If you haven't bought the combiner, most of us recommend an echo charger instead. Rather than the + to ground on the always on stuff, that ground should be from the individual components, not the bus bar. The combiner needs fuses, too.

mitiempo · Jan 5, 2012

I agree with Stu. A battery that is either used exclusively for starting or kept as an emergency battery as in your plan will be well cared for with an Echo Charge instead of a combiner. I would also wire it direct to the battery posts. I think the fuses in the wires to the house bank should be in each individual wire as they will be different sizes and you fuse for the wire.

Maine Sail · Jan 6, 2012

It looks good and I agree with the assessments of Stu & Mitiempo. Perhaps the most important is that the alt, solar and bank 1 feed can't share the same fuse unless those wires are all the same size..

Bill Roosa · Jan 6, 2012

I believe you do not need a combiner as you indicated you were going for a "primary/secondary" battery setup. Just leaving the 3-way on BOTH will allow both banks to charge. Then if you want to "save a bank for later/starting" just switch to the bank you wish to use. Using both banks will cause your average SOC to be higher so unless you think you are going to drain them both to the point where you will not be able to get the engine started you would want to leave the 3-way in the BOTH position.
You might want to consider placing the alternator + on the 3-way common (C) post as this will allow you to choose which bank(s) gets charged. Nice to have if you are trying to rapidly recharge a discharged bank and not drag down the other by connecting it.
Additionally, you do not have a fuse on the main cable to the main house buss. If it is short then you are ok. If it has to go to another compartment (battery to nav station??) then a fuse would be required. You may also be able to eliminate the fuses on the wires between the main house buss and the secondary panels. Kinda depends on the length of the wire and how comfortable you are with them NEVER shorting to ground or being overloaded. Shorting and overloading depends on the exact configuration of the wiring in the boat. A single large positive wire that never comes close to any other wire and will never see your brother-in-law drive a screw into it hinging up his favorite beer poster and can handle the full load applied would not need a fuse. Needless to say, we don’t know your brother-in-law. ;-)
You will need some sort of charge controller if your solar panels produce in amps more than 10% your combined banks AH ie 100 amp-hour banks need a controller if your solar panels produce more than 10 amps. Anything less is just a trickle charger and you can wire them directly (with a blocking diode of course) as shown.

Bill Roosa · Jan 6, 2012

AND
where is the shore power charger going. Recommend wiring it's 12 volt + leads to each battery bank positive IF the charger can isolate it own leads. otherwise it will act like a connection between the banks and totaly circumvent the 3-way switch. if it does not isolate its + leads then you are pretty much left with attaching them all to the 3-way common post and treating it like an alternator.

Stu Jackson · Jan 6, 2012

Bill Roosa said:
1. I believe you do not need a combiner as you indicated you were going for a "primary/secondary" battery setup. Just leaving the 3-way on BOTH will allow both banks to charge. Then if you want to "save a bank for later/starting" just switch to the bank you wish to use. Using both banks will cause your average SOC to be higher so unless you think you are going to drain them both to the point where you will not be able to get the engine started you would want to leave the 3-way in the BOTH position.

2. You might want to consider placing the alternator + on the 3-way common (C) post as this will allow you to choose which bank(s) gets charged. Nice to have if you are trying to rapidly recharge a discharged bank and not drag down the other by connecting it.

1. If your desire is to automatically charge your reserve bank, a combiner or preferably an echo charger is the way to go. The Both position should only be used if the echo charger fails for some reason. Never leave the switch on B unless charging is present.

2. NOPE. This defeats the whole purpose of having the alternator output go to the house bank. Discussed in detail here (which you have done well as Option 1): http://c34.org/bbs/index.php/topic,6604.0.html

Are you just being contrarian again, Bill?

Stu Jackson · Jan 7, 2012

Cool Beans said:
1. Fuse alternator and solar. . .okey-dokey. I'll probably run the solar and any other charge sources to the "always on busbar" and run the alternator to the "+" post. I haven't given much thought to an on-board charger yet. . .I guess I can hook one up and just not leave it on all the time. With the Echo Charger, I would only need to wire the house bank in, correct?

2. It's about sizing the primary wire to the switch and to the starter and the main fuse. The engine is an Atomic 4, and the Moyer Forums (and original wiring diagrams) have a #4 wire going from the battery to the switch to the starter, no fuses that I've seen. I'm going to use a Blue Sea Terminal Fuse Block on the battery post...

1. You have three things going to the + on your house bank. You could do what you suggest in #2, but putting one fuse on the + post seems to defeat your wiring diagram with the individual fuses, which should be sized for individual wire sizes for your alternator, solar and always on things. So, what I suggest is what is called a PDP or Positive Distribution Post. This is either a Blue Sea Power Post or a bus bar, to which these three things connect with their individual fuses. If you use a Power Post Plus it has smaller screws for your always on loads and stereo memory switch and bilge pump, just like a bus bar would. Then you run one single wire from the PDP to the house bank + post. The advantage is that you don't end up stacking more than one wire on house bank + post. I've found it much easier. That's what Brian and MS already said in Replies #3 & #4. Maine Sail has shown pictures of this concept in many of his wiring articles - check out the Musing with Maine Sail stuff in Forums, Featured Contributors. Like this one: http://forums.catalina.sailboatowners.com/showthread.php?t=129595 We have also recommended an on/off switch on the wire from the alternator to the house bank. This makes it easier to work on your alternator, since it'd be "live" when directly connected. Or, take the fuse out when you work on the alternator. That's mentioned in the Sailnet discussion, see below.

2. Maine Sail has discussed fusing the starter feed many times. To size that wire you need to know the amperage draw for your starter. Try this or other Maine Sail articles, I know he did one specifically for starters. http://forums.catalina.sailboatowners.com/showthread.php?t=130775

That said, I have #4 wire from my house bank to the switch to the starter on our diesel M25 and it's been working fine for 25 years. Once the engine starts, the DC loads that could could run on a boat can be added up, and even if you ran almost everything on the boat at the same time (and you wouldn't run your bilge pump, shower sump pump, and macerator pump all at the same time, would you?) it'll be well less than the 30A that a #4 wire could handle (given the wire lengths for a 33 foot boat). You can find fuse sizes on the link I gave you in my last post, the last post there with the detailed wiring diagram. I think the 2/0 wiring as shown is way overkill. That diagram came from a Sailnet discussion which MS also participated in, and in that topic there is a link to that Sailnet discussion. I know you mentioned about it being discussed before, so perhaps you could read that and see if you have any more specific questions. The larger the wire, the larger the fuse. That's discussed in that link, too. Sorry to send you link-to-link-to-link, but it's only three clicks away, and pretty much all there to answer your questions. Maine Sail also comments on a single OCPD to a PDP in that Sailnet discussion. There's also this from MS's: http://forums.catalina.sailboatowners.com/showthread.php?t=130545 It includes this lin: http://forums.catalina.sailboatowners.com/showthread.php?t=130245

You're heading in the right direction. I'd bet that if you updated and posted your wiring diagram based on the answers to your questions, you would get some more specific responses.

mitiempo · Jan 7, 2012

I wouldn't use a wire smaller than 1 awg for a starting circuit on any engine. Most often I use 1/0 or 2/0. For fusing use an ANL fuse rated for the ampacity of the wire. 1 awg wire has an ampacity of 208 in engine spaces. A 200 amp ANL will be slightly smaller than the wire capacity and will not blow during starting. A 200 amp ANL will withstand 320 amps for 500 seconds.

Maine Sail · Jan 7, 2012

mitiempo said:
I wouldn't use a wire smaller than 1 awg for a starting circuit on any engine. Most often I use 1/0 or 2/0. For fusing use an ANL fuse rated for the ampacity of the wire. 1 awg wire has an ampacity of 208 in engine spaces. A 200 amp ANL will be slightly smaller than the wire capacity and will not blow during starting. A 200 amp ANL will withstand 320 amps for 500 seconds.

I would agree. Anything smaller both limits your fusing potential for max ampacity and can be a strain on starter motors. 2Ga on short runs can be ok but 4GA is very small for an engine starting circuit even on a gas engine. If it ALWAYS starts right up then your safe but if you ever need to crank it multiple times, or for longer than a few seconds, it can get the wire quite hot especially if a little corrosion has set in. That being said there are plenty of older boats out there with 4Ga wire that have worked fine. I do drop a lot of starters off to be re-built on boats with small starter wires though and it seems to be a "consistent" trend compared to boats with larger ga starting circuit wires. I generally use 1/0 or 2/0 because it allows for proper fusing of starting circuits without needing to use the 150% rule...

Stu Jackson · Jan 7, 2012

Yup, discussed in the links I provided.

To add: I have doubled the negative wiring with (2) parallel #4s, so only the positive wire from house bank and reserve bank to the switch and on to the starter is #4 (only). Starter works rapidly every time.

mitiempo · Jan 7, 2012

Stu

Doubling the negative gains nothing if the positive is still a single 4 awg wire.

Stu Jackson · Jan 23, 2012

mitiempo said:
Stu

Doubling the negative gains nothing if the positive is still a single 4 awg wire.

Right, 'cept the AO is #2.