Thanks guys. I’ve returned the Isolator and ordered the Blue Seas ACR with a switch. We hope to step the mast next week, that’s another story for another day, and get the power working as best we can. One thing I know about boat projects is, unless you have unlimited money, things have to be done in stages. And this is stage one for the power side of the boat. After this, we want to add a couple more batteries and solar.
I’m Tweaking My Battery Banks and Need Advice
- Thread starter reuabyor
- Start date
We learn much more from our mistakes and correcting them than doing something right the first time.
In my basement there is a small marine supply shop filled with "good ideas."
I imagine that if we all put together our supply of things that we bought and then couldn't use we could build a couple of nice boats.In my basement there is a small marine supply shop filled with "good ideas."
So….I got the ACR and On/Off/Combine switch in yesterday. So I don’t try to reinvent the wheel, based on my original diagram, where would you guys insert them and what do I need to remove from service?
Also, I’m reading and watching the links Stu Jackson and Maine Sails recommended, I’m just trying to cover my bases.
Also, I’m reading and watching the links Stu Jackson and Maine Sails recommended, I’m just trying to cover my bases.
There should be a wiring diagram with the ACR. It goes between the Positive on the house battery and positive on the start/reserve battery. Fuse both ends within 7 inches of the terminal.
Where it gets tricky is the battery terminal.The max number of connections on the terminal is 4 and they should all be fused. Take a look at the MRBF fuses and terminals at Blue Sea Systems.
I keep running into details I need help with, and clarification on. I’m installing the ACR and Switch from Blue Seas.
Because of limited space I can’t install the MRBF terminal blocks from Blue Seas (too tall) so I’m installing a Surface Mount Fuse Block instead. My question is: Based on my 1000 CCA stater battery and 51 Amp alternator, what fuse(s) do I use? I’ve read 125 -150% of alternator rating — which means roughy 90-100 amp fuse, but that sounds awfully low.
Also, what about fuses on the House Bank side? I have two 6V 230 AH batteries connected in series.
Because of limited space I can’t install the MRBF terminal blocks from Blue Seas (too tall) so I’m installing a Surface Mount Fuse Block instead. My question is: Based on my 1000 CCA stater battery and 51 Amp alternator, what fuse(s) do I use? I’ve read 125 -150% of alternator rating — which means roughy 90-100 amp fuse, but that sounds awfully low.
Also, what about fuses on the House Bank side? I have two 6V 230 AH batteries connected in series.
Incorrect info for the question.
You size the wire for the load and the distance.
Then you size the fuses for the wire size.
In ES101, I included this link:
Wire Sizing Tables from West Marine (unfortunately they removed the handy charts! around 2016) Marine Wire Size and Ampacity | West Marine
www.bluesea.com also has good material on this and fusing, but it's a PDF download and doesn't link. Here's the link to the page, scroll down for the PDF download of the Protect Your Boat With The Correct Size Wire And Fuse - Wire Size Chart: https://www.bluesea.com/support/reference
Download the PDF and use it.
What @Stu Jackson said. Also you probably want the single feed version one the MRBF holder.
The existing cables should be labeled with their size.
And yes, doing things correctly is sometimes a real PITA, however, in the end there is a sense of satisfaction that the work was done correctly and not just slapped together.
The existing cables should be labeled with their size.
And yes, doing things correctly is sometimes a real PITA, however, in the end there is a sense of satisfaction that the work was done correctly and not just slapped together.
Here’s the latest diagram. These are the pieces I have, and hopefully you guys can look at it and help me make sure it’s all connected correctly.
The surface mount fuse block has 1 in and three out. I’m thinking of using it because I don’t have the height in the battery compartment for mrbf fuses directly on the battery.
The surface mount fuse block has 1 in and three out. I’m thinking of using it because I don’t have the height in the battery compartment for mrbf fuses directly on the battery.
Attachments
I like the surface mount MRBF and I am using it in my own installation. But, I don't quite understand your intended installation with it. Keep in mind that you want a fuse within 7 inches of the battery terminal and the fuse needs to be sized for the battery cable that is attached to the battery post. I suppose that if you mount the devise within 7 inches of the battery, and you connect a short cable between the batt terminal and a fused post on the surface mount with the correct fuse on the run from the surface mount to the selector switch, that might be ok. I don't like it, though. It just seems awkward and possibly not acceptable. Edit - the fused posts aren't intended to stack 2 cables on opposite sides of the fuse. I think you would have to run the batt cable to the un-fused post and then a fused cable to the selector switch. Like I said before ... awkward!
In that situation, I would prefer to use a surface mount AMG/MEGA holder and the appropriate fuse for the battery cable on the run from the batt terminal to the selector. The Blue Sea model is 7721 as I am looking at one on my desk right now.
What is that Off/On/C switch? It has 4 posts like a DCP switch. If you are using a DCP in conjunction with the 1/2/B switch I don't see how you can isolate the house bank if you need to. As I said before, just throw out the 1/2/B switch and use the DCP switch correctly with 2 on-off switches for isolation. The mini switches are not expensive, they take little room and you should hide them in an enclosed area. The mini switches will be suitable at 300 amp capacity.
Last edited:
Rod, I have heard you and others say [that diode based battery isolators are a terrible idea] before but have never seen why. In one of your articles in Marine How To, you discuss the voltage drop but mention that it can be overcome by having the battery sense wires on the house bank. In my current system, I have a 120A combiner and both the + & + sense wires are on the house battery and the external regulator holds the battery voltage right where I want it.
I am in the planning stage of an LFP house bank and will retain my AGM start battery. The external regulated alternator with go to the combiner and the regulator will monitor the AGM start battery which will never be disconnected by a BMS which will protect the alternator diodes.
With this setup what is the problem with the diode combiner that make it a (NEVER). What am I missing?
On my setup, I have two independent 1/2/both switches that are used to shut off the output of the batteries, one to the start and the other to the house circuits. Both of these switches are connected to each other on the "2" terminal which allows me to connect them together for emergency starting.
There is no shutoff switch on the alternator connection with just three wires, alternator to battery combiner and one to each battery and the combiner separates the two banks when the alternator has no output.
Last edited:
Scott — you are right about the fuse block being awkward. I’ve been trying to figure that one out myself.
You can see why I haven’t drawn lines to connect the diagram. It didn’t make sense. I’m trying to figure out which parts of my existing system to leave and which ones to remove. The 1/2/B is already there, connected to the panel.
You can see why I haven’t drawn lines to connect the diagram. It didn’t make sense. I’m trying to figure out which parts of my existing system to leave and which ones to remove. The 1/2/B is already there, connected to the panel.
I'm sorry ... I am confused by the discrepancy in your posts. Earlier, you showed a picture of the MRFB surface mount independent source (Model 5194), which has 3 terminals. Your diagram above appears to show the MRBF COMMON source surface mount, which has 4 terminals (Model 5196). The one you showed earlier with a picture should be fine, but it isn't really what you need. I think you only need a single fuse block, which can be of the following 3:
Model 5001 or 7721 MEGA/AMG (up to 300 A)
Model 5503 ANL (35 to 750A)
Model 5502 or 5502100 Class T (225 to 400 A)
I would use the MEGA/AMG because they are less expensive and should be suitable.
The other point of confusion is your diagram that shows a new switch with 4 posts. That can only be a Dual Circuit switch or Dual Circuit Plus (DCP) . Earlier, you said you bought a 1/2/C switch. That is identical to the switch that you have (1/2/B - they are the same thing). These switches have just 3 posts. So the picture diagram didn't match your earlier post. You can use the 2 switches to achieve independent Start & House batteries with isolation. One switch will be your start switch, the other will be the house switch. A combination of the 2 switches gives you the ability to serve both loads with just one battery bank.
Assuming that you will use a pair of 1/2/C switches, the attached is how you can run your cables. You will need a fuse block for both the Start and the House Battery. You can use the Independent Source surface mount block that you showed in the picture in post #27 for both battery sources if you can fit it in a location that is 7 inches from both positive batt terminals. Otherwise, you can get a pair of fuse blocks that you can mount as needed.
Assuming that you want independent House panel and start sources, you can wire the cables as shown. Your normal use would be Position 1 for House Panel and Position 2 for Start. If you want the House Batt source to provide for both the House panel and start loads, then put both switches in Position 1. If you want the Start Batt source to provide for both the loads, then put both switches in Position 2.
There is no need to ever use the Combined (1+2) position, particularly if you are using ACR to charge all batteries. I only know how to post a photo, so here is a photo of a sketch I made. Obviously, it doesn't show all components and not all of the NEG connections. (oops - I incorrectly portrayed which NEG terminal on the house bank to connect to ground. The NEG from the top battery should be connected to the ground for a balanced bank load.) - new (I corrected the diagram).
Assuming that you want independent House panel and start sources, you can wire the cables as shown. Your normal use would be Position 1 for House Panel and Position 2 for Start. If you want the House Batt source to provide for both the House panel and start loads, then put both switches in Position 1. If you want the Start Batt source to provide for both the loads, then put both switches in Position 2.
There is no need to ever use the Combined (1+2) position, particularly if you are using ACR to charge all batteries. I only know how to post a photo, so here is a photo of a sketch I made. Obviously, it doesn't show all components and not all of the NEG connections. (oops - I incorrectly portrayed which NEG terminal on the house bank to connect to ground. The NEG from the top battery should be connected to the ground for a balanced bank load.) - new (I corrected the diagram).
Attachments
Last edited:
Yeah, this thread is hard to follow because I’ve returned and bought new stuff as I’ve learned. When I bought the ACR, it came with the On/Off/combine switch. The 1/2/b is currently part of the breaker panel.
I actually have these as well and I realize these are a better option and similar to the 7721.
I’ll try and clear some confusion next time I post.
I actually have these as well and I realize these are a better option and similar to the 7721.
I’ll try and clear some confusion next time I post.
Attachments
That fuse block will be fine ... are you sure about the selector switch that came with the ACR? I've only seen packaging for ACR and switch together with the DCP switch - and that is consistent with your diagram that shows 4 posts. I think I'm getting confused by the terminology you are using. I guess "ON/OFF/C" is referencing the DCP switch? In that case, you can throw my diagram above out the window. I'll go back to my earlier comment - Use the DCP switch and get 2 mini on/off switches and throw out the original 1/2/B switch. Otherwise, you can't isolate battery banks and use them independently with combined loads (emergency condition) if you are inserting DCP without 2 on/off switches. Sorry for the confusion. If you have DCP, call it DCP not ON/OFF/C (I was looking at different switches and got messed up )
The photo below is how you use DCP and provide isolation if you ever need to combine the loads. You can hide the 2 on/off switches and leave them permanently "ON". You only need to turn one or the other off for an emergency isolation situation.
)The photo below is how you use DCP and provide isolation if you ever need to combine the loads. You can hide the 2 on/off switches and leave them permanently "ON". You only need to turn one or the other off for an emergency isolation situation.
Attachments
Last edited:
Thank you for your patience with my ignorance. I saw the sketch. I’ll pour over it when I get home tonight.
Yes. it is a DCP. Boat electrical (electrical in general) is a new language for me and I’m slowly figuring it out.