DC Battery Rig

[mtompson]

Originally Posted by Hyprdrv

I saw issues with the house bank (3) being used as a starter battery. There was enough voltage drop when cranking for the Electronics to blink off and on. Not good for that stuff. Moved the motor to a dedicated battery and the issues went away.

Steve in Solomons MD

Makes sense, how are you charging the dedicated battery in that setup?

[wellin]

Yes Steve, the house batts should be deep cycle and not really good for high amp starting loads. They are made to release energy slowly over time. Starting batts are made to go 500 or 1,000 amps for a few seconds.
I use the 1,2,all switch to select from two starting batts so i have a back up. I start the engine on batt 2, then shut down and start on batt 1. BEFORE i untie. They are wired with seperate chargers from shore power and fed through an isolator from the engine alternator.

Sent from my SCH-I415 using Cruisers Sailing Forum mobile app

[mtompson]

Still open to these great observations & comments, but for now I'm just posting this little update to identify the fuses. ( inc a new one off the switch common )

I'd love to see other circuit diagrams that illustrate some of the points made.

thanks everyone.

[cal40john]

Have you seen this post by Mainesail?

1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com

[Maine Sail]

mtompson,

Your wiring looks good and I only have a few observations.

1- You show switches on Echo, Solar, Alt etc.. These are not a bad idea but that is a lot of switches to remember after servicing the engine etc.. Also be sure your solar regulator is okay with switching on the load side not the panel side. Some manufacturers prefer load and some prefer panel side. Perhaps easier when working on the system to just pull the bank fuse.

2- The MRBF dual post I would switch to the house batt and run the alt to one post and the loads to the other. Use the in-line Echo fuse on the start battery.

3- You don't specify wire gauges, bank size or fuse sizes. That info should ideally be there so we can comment on the suitability, sizing ampacity etc ..

4- You don't show a shunt which would indicate lack of a battery monitor or ammeter. If you do have one be sure to wire it in there properly. Perhaps 7 out of 10 I see installed by pro's and DIY's are wired incorrectly (shunt wiring) and 9.5 out of 10 are programmed incorrectly. When set up correctly, wired correctly and used correctly they are great tools. When set up and installed poorly, they can be misleading.

5- The wire from your house bank positive all the way to the starter should all be the SAME SIZE and this is already protected by the battery bank MRBF fuse. There is no need for additional fusing between the battery and the starter as it is already covered.. Where you step down for house loads, after the "C" post, then you will need a different sized fuse, if not using the same gauge wire to the DC panel. Every fuse adds voltage drop so I would suggest removing the buss bar fuse going to the #1 position and the ANL after the "C" post to the starter.



Some thoughts:

There are many ways to wire your sailboats batteries and I am often taken out of context when it comes to wiring battery systems..

As a marine electrician I see it all and wire it every way from Sunday. I often treat sailboats differently than trawlers and trawlers differently from large inboard sport fishing boats and large sport fishing boats differently from outboard powered boats. Each type of boat has its own unique set of uses and issues to deal with.

In an ideal world every boat would have full redundancy so either bank could be used for either purpose, if needed. I always try to design systems with what you might call a "spare tire".....

* If you have a suitable & healthy house bank, usually 200Ah+, and suitable and healthy wiring, then using it for starting is an easy solution if you already have a 1/2/BOTH switch installed on-board. It avoids the needless switching back and forth so many folks believe they need to do between a "house" and "start" bank..

Any healthy bank of house batteries, with good wiring and connections, should EASILY start a small sailboat motor without dropping electronics all the way down to 50% SOC. Starting these motors for a 200+ Ah bank is like Lance Armstrong getting up out of a chair, not much effort at all.

* It is a complete fallacy that you need "starting batteries" to start a sailboat aux diesel engine. Any suitable deep cycle house bank will do this with ease and will usually out last a cheap thin plate starting battery.

* If you decide to use the house bank as an everything bank the start battery can't be ignored and should be checked from time to time. Every now and then start on that battery to check it or run the inverter from it to give it a good work out.

* If your house bank is dropping out electronics, while starting, at 50% SOC, it is: A) Not a healthy bank B) Not suitably sized to do both deep cycle and starting C) You have wiring and voltage drop issues in the system compounded onto battery voltage sag..

You have two choices in this situation, either address the issues & short comings or re-wire for dedicated start battery. Simple stuff.

* There are millions of 1/2/BOTH switches out there and as of a few months ago, other than the ON/OFF, the 1/2/BOTH was still Blue Sea's #1 selling battery switch and it was pretty close numbers wise to the ON/OFF.... The vast majority of boat builders still use these switches. It can be an excellent switch, and there are many good ways to use it, if you want to. This LINK takes a deep look into the 1/2/BOTH Switch...

* One of my favorite switch configurations, if starting from scratch, is three properly wired ON/OFF switches.. One for HOUSE one for START and one for emergency cross connect. With this set up each bank can be 100% isolated and the other bank used in an emergency. Unfortunately many boats are not well suited to retrofit this three switch method, especially with the number of battery switches out there mounted in custom panels.

* An option that takes from that idea (three on/off's) is keeping the existing 1/2/BOTH and using it in conjunction with an additional ON/OFF. The ON/OFF serves as a dedicated starting battery switch and the #1 position serves as HOUSE. The other positions are there for complete system redundancy & isolation.

For sailboats that already have a 1/2/BOTH installed it can make life a lot easier to just use it as an ON/OFF and let an Echo or combiner do the rest, if your bank and wiring are up to the task.

* The only switch I really don't really care for all that much, for deep cycling applications, is the Dual Circuit Plus. I am not a huge fan due to the lack of redundancy and the only safety measure being to combine a potentially bad bank with a good one, unless you physically get in there and disconnect stuff...

The DCP is a simple and easy switch, and this is a great feature, but not one that offers a lot of back up, isolation or redundancy measures.

[mtompson]

I have, thanks cal40john, I'm a big fan of his logic. I'm not closed minded to other ideas, but I understand his ideas come from a vast amount of experience. ( and an amazing website! Compass Marine "How To" Articles Photo Gallery by Compass Marine at pbase.com) )

[mtompson]

Thanks for your comments Maine Sail

I'll have a go, but if you have any diagrams of the:

6- One of my favorite switch configurations, if starting from scratch

you mention, I'd love to see one.

[mtompson]

I'll have a go at a new diagram, I'm going to leave; batt, wire & fuse values until a little later as I'm still working on bank sizing.

[Maine Sail]

Originally Posted by mtompson

Thanks for your comments Maine Sail

I'll have a go, but if you have any diagrams of the:

6- One of my favorite switch configurations, if starting from scratch

you mention, I'd love to see one.

Three ON/OFF's

Normal Everyday Use:


Start Bank Failure & Start Isolation / House Takes All Loads:


House Bank Failure & House Isolation / Start Takes All Loads:

[smac999]

I really don't like the above set up. as far as I'm concerned it's a safty hazard because you can start the engine with the engine switch off. and you can have power on the house loads with the house switch off. a hazard for people working on the boat.

yes it's nice to be able to isolate. but I'll take safty over function. the middle switch should be on the battery side of the other switches. when the engine switch is off. the engine should be dead. and when the house switch is off. the house should be dead.

[Stu Jackson]

There are many, many different ways to draw a wiring diagram, but these work functionally, so check against yours:

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

[cal40john]

Originally Posted by smac999

I really don't like the above set up. as far as I'm concerned it's a safty hazard because you can start the engine with the engine switch off. and you can have power on the house loads with the house switch off. a hazard for people working on the boat.

yes it's nice to be able to isolate. but I'll take safty over function. the middle switch should be on the battery side of the other switches. when the engine switch is off. the engine should be dead. and when the house switch is off. the house should be dead.

Then there's no point to the middle emergency cross connect. If a bank is shorted or very dead, connecting a good battery to it isn't going to do anything but make that battery unusable.

[Maine Sail]

Originally Posted by smac999

I really don't like the above set up. as far as I'm concerned it's a safty hazard because you can start the engine with the engine switch off. and you can have power on the house loads with the house switch off. a hazard for people working on the boat.

yes it's nice to be able to isolate. but I'll take safty over function. the middle switch should be on the battery side of the other switches. when the engine switch is off. the engine should be dead. and when the house switch is off. the house should be dead.

Look at the labels on the switches..... The middle switch is for EMERGENCIES only...

It can even be a key type or lockable switch. The whole idea is to create a system that does not leave you dead in the water or combining a failed bank with a good one. Putting the emergency switch on the batt side of the ON/OFF's does nothing but get you paralleling of two banks. It offers zero safety isolation of a failed or bad bank.

Putting the emergency switch on the loads side gives you paralleling, isolation and bank redundancy and does not force you to combine a failed or shorted bank with a good one, in a emergency...

[mtompson]

Originally Posted by Maine Sail

mtompson,

Your wiring looks good and I only have a few observations.

1- You show switches on Echo, Solar, Alt etc.. These are not a bad idea but that is a lot of switches to remember after servicing the engine etc.. Also be sure your solar regulator is okay with switching on the load side not the panel side. Some manufacturers prefer load and some prefer panel side. Perhaps easier when working on the system to just pull the bank fuse.

2- The MRBF dual post I would switch to the house batt and run the alt to one post and the loads to the other. Use the in-line Echo fuse on the start battery.

3- You don't specify wire gauges, bank size or fuse sizes. That info should ideally be there so we can comment on the suitability, sizing ampacity etc ..

4- You don't show a shunt which would indicate lack of a battery monitor or ammeter. If you do have one be sure to wire it in there properly. Perhaps 7 out of 10 I see installed by pro's and DIY's are wired incorrectly (shunt wiring) and 9.5 out of 10 are programmed incorrectly. When set up correctly, wired correctly and used correctly they are great tools. When set up and installed poorly, they can be misleading.

5- The wire from your house bank positive all the way to the starter should all be the SAME SIZE and this is already protected by the battery bank MRBF fuse. There is no need for additional fusing between the battery and the starter as it is already covered.. Where you step down for house loads, after the "C" post, then you will need a different sized fuse, if not using the same gauge wire to the DC panel. Every fuse adds voltage drop so I would suggest removing the buss bar fuse going to the #1 position and the ANL after the "C" post to the starter.

Ok, here is a stab at those points. I kept an MRBF dual post on the Aux batt instead of "Use the in-line Echo fuse" just to be neat. Do I need a fuse on the House side of the Echo?
I've just marked the wire sizes on the run from house to starter motor, just to show they stay the same so only need the MRBF on the batt.
Anyway we have dropped a couple of fuses so far, so thats good...
Hows the Batt monitor wiring?

many thanks...

[mtompson]

Thanks for posting the 'Three ON/OFF's' diagrams, once I've had a good look, I'll try and rig one of my diagrams the same.