New batteries and charger

[Denise]

Hi All,
I am in the process of replacing my boat's old batteries with new ones and with replacing and upgrading the battery charging system. I've read quite a bit that's been both posted online on the subject and written in books, and can't help but feel confused. I realize that everyone tends to approach this in their own way, but I would really like the benefit of this forum's opinion on my current path.

First of all, I'm replacing two very tired 8D batteries that not only support the house load but also crank the engine, a Ford Lehman 120. The existing battery charger is probably original to this boat. It is controlled by the original battery switch that I have to turn off and on depending on the charging need. This, by the way, is why the batteries are all but dead. User error.

My biggest power drain is the newly installed Espar Airtronic heater, which refuses to work with the existing batteries. Probably my next big power drains are the electric macerating toilet and the refrigerator.

I'm using the existing battery boxes and installing 4 6V golf cart batteries for the house bank, and a type 31 cranking battery for the engine. I'm replacing the existing battery charger and adding an ACR combiner. Here's what is now installed before any changes (sure hope I understand these image tag):





My challenge is to dismantle the existing charger, install the new switch and wire everything appropriately, using as much of what is already there as I can. My plan is roughly laid out in this diagram.



I bought this charger, switch and ACR unit:







I've based this solution on my own (often imperfect) understanding of what I've read up on all of this. I'm not sure about wire size but think I should probably match the current wire size at the batteries all the way to the switch, the alternator and the ACR unit.

Would anyone be willing to offer opinions on my approach to this?

Thanks!

[Maine Sail]

Looks good though you can save some money on battery cables by jumping the neg from one 6V side to the other for "parallel" then going to the gnd buss. The shorter the runs for "parallel" the better. The alternator would be best served by going direct to the house bank, not the start, to prevent the potential for relay chatter. I would also include fuses at the batteries rated to protect the battery cable.

I also like to see a fuse in the ground side of the ACR, as recommended by Blue Sea. Also an on/off switch in the ground line of the ACR can be handy on that unit. The start bank will most always be at or near 100% SOC so no real need to send if charging volts if not necessary. I am assuming you will be doing everything off the house bank including starting and just leaving the 1/2/BOTH/OFF on the house bank..

All grounds, DC black or yellow, and AC green, should run back through the DC ground buss bar then ONE ground wire should run to your ship ground, often the engine block. You don't want to create two separate ground points on-board if you can avoid it.

[mitiempo]

Looks good with Maine's recommendations taken into account.

You show a battery monitor wired to the main switch. What is it?

[Denise]

Thank you Maine Sail,
I've revised the plan accordingly and included the new diagram. I've cleaned up the battery connections a bit. I'm assuming I can go to a buss bar from the house bank and take everything out from there. I'm trying to keep my battery connections as clean as possible. The black ground wires in the diagram will all be yellow in reality. There's nothing worse for me than the confusion of identifying DC ground wiring when there's lots of AC wiring aboard. But I'm just trying to work through this in my mind.

The fuses at the batteries are not in this diagram. I'm not sure how to lay those out. I've added a switch on the ACR ground but am not sure which side of the fuse it should be located on.



The battery monitor is truly optional for me. I don't have one now and haven't shopped for one yet, but I feel I could add one some time in the future. I think I'll need a shunt for it and I still haven't figured out what a shunt does.

I can't tell you how much I appreciate this help.

[mitiempo]

Looks better.

Fuses for the batteries should be in the positive cable and close to the batteries - within 7". A neat solution is the Blue Seas 5191 which mounts directly on the battery post. Pic below.

A shunt measures current flow. For a battery monitor it is in the negative cable, with two sense wires going from the shunt to the meter. Any monitor you buy will come with one.

[Denise]

Thank you mitiempo,
I like this terminal fuse block idea a lot. I'm looking at the info on it and it looks like only one ring terminal should be used per fuse. For the house bank I can run the parallel cable to the post and fuse the run to the buss bar. For the reserve battery, should I get a double block to fuse both the ACR and the battery switch runs? Will the terminal fuse suffice for fusing between the ACR and the battery? Should the battery switch be fused at the battery?

[mitiempo]

Yes, for the house bank I would fuse the positive cable to the bus.

For the start battery I would fuse the positive cable to the 1/2/c switch.

I would fuse the ACR separately.

You can remove the battery monitor from the 1/2/c switch as it wouldn't connect there.

[Maine Sail]

Batt charger should go to the POS buss bar, same as alt, and the ACR should be BETWEEN the house and reserve banks, you have it between the batt charger and start bank...

It is a good idea to fuse the charger at the POS buss as well as the alt.

Here's how I laid it out on my own boat.

Installed:


The three ANL fuses on the left are bussed together with a custom made copper buss bar. I really wish Blue Seas would make a ganged ANL fuse option!!!! I don't use or draw wiring diagrams when I work but I did draw one for a buddy which I will try and find..

[mitiempo]

Maine
The way I read it the ACR was between the start battery and the positive bus for the house bank but the way it is drawn is a bit confusing.

Another solution would be an Echocharge instead of the ACR. It is a bit more expensive by itself but the 3 fuses and the heavier cables the ACR uses wouldn't be necessary. All told probably a saving.

[Denise]

Maine Sail,
If I understand you on this, I shouldn't go to the positive house bank busbar with the ACR, but rather directly to the bank itself? I've made a few changes and hope I'm getting closer to where I need to be. I haven't changed the ACR yet because I wanted to make sure I understood you on that. I'm just laying this out in Visio and it's not as descriptive as perhaps it should be.

It's not that I'm trying to find the cheapest route. I'm trying to do this myself and understand it well at the same time. I have to draw it out in order to achieve this. The pictures you have help a lot. Thank you!

[Maine Sail]

Maine Sail,
If I understand you on this, I shouldn't go to the positive house bank busbar with the ACR, but rather directly to the bank itself?

Yes the shortest path will be the most efficient with less chance of voltage drop and it will limit the amount of connections.

It's not that I'm trying to find the cheapest route. I'm trying to do this myself and understand it well at the same time. I have to draw it out in order to achieve this. The pictures you have help a lot. Thank you!

One other consideration that I missed in the last photo is that you'll want to pull the ground off the batt banks on the opposite bank/side from the charge and load sources. This will force both banks to be treated 100% equally. Just move the ground from the right bank to the left bank then current flows across all batteries evenly.

[Denise]

Main Sail,

I've altered my diagram in order to rearrange the batteries according to how I think they will work best on the boat. I've also used clearer symbols for the busbars so this diagram is a bit different from the previous ones here, but hopefully only in the arrangement of where all the components are located and with your additional suggested changes.

The engine is located where the alternator is shown, and the starter and switch are located where the helm station is in relation to the engine on this boat. I'm hoping this will work. If so, I'll start ordering the remaining items I will need to put this together. Thank you again for your incredible guidance.

[Maine Sail]

My explanation clearly was not very good.

Notice how the current is now forced through the entire bank with ground and positive on opposite sides. This forces even discharges and charges of the entire bank.

[Denise]

Wow, I really got that one wrong! Your diagram completely clears things up for me and makes sense of the flow of current.

Thanks again. Time to measure and order the cabling and fuses I need.

[Pinching]

D:
My only suggestions may be redundant. I'd suggest a field disconnect switch on your battery switch if there is any chance the alternator output could be isolated from a battery

Not familiar with combiners -- will the alternator adequately sense the big battery? My alternator guy said that there was often some degree of internal regulation on Alts even with an external regulator

Best of luck. P

[mitiempo]

No reason for a field disconnect on the battery switch as the alternator output goes direct to the house bank.

The alternator isn't a problem. I am not sure if it is internally or externally regulated.

[Denise]

Hi and thanks,
The alternator is externally regulated. It's an 80's vintage Ford Lehman 120. I have a friend helping me and he thinks I should wire the starter directly to the cranking battery. I originally had it going to the battery switch. Is there any reason I can't do this?

Denise

[mitiempo]

Denise
You want to go direct to one bank or the other from the alternator, not the switch. Which ever battery you choose the ACR will take care of the other. By avoiding the switch you eliminate all possibility of human error.

[Denise]

Yes, the alternator wire is going to run directly to the house bank. It's the engine's starter wiring that is confusing me. Right now it's going directly to the battery bank. I thought it was supposed to go to the switch. But I guess that was my misunderstanding.

Denise

[mitiempo]

Sorry.
If you wire the starter direct to the cranking battery you will be eliminating any way of isolating power to the starter. It should go to the switch. Then when the switch is off it means off. Also that gives you the option of starting from the house bank. I would always start from the house bank and keep the start battery for emergency. That way the switch is turned to #1 (house) when you come aboard and off when you leave - nothing is simpler.

[Denise]

Ok, I think that's something I can explain to my helping friend so that he can see why it's the better way. Thank you for clearing that up.

Denise

[Maine Sail]

Ok, I think that's something I can explain to my helping friend so that he can see why it's the better way. Thank you for clearing that up.

Denise

Wiring direct to the battery is not advised as it can be a safety issue. What if the stater motor were to fail and you had no way to isolate it? You could essentially burn down the boat if you had no fuse.

Also by wiring direct you lose ALL redundancy. If your start battery croaks, your stuck up a creek and have no way to start the motor. If you wire it to the C post of the 1/2/ALL/OFF switch you still have another bank to use at the flip of a switch and either bank can be used to start the motor or support house loads.... The redundancy of a 1/2/ALL/OFF switch, when wired appropriately, makes it a really useful device. Even if the combiner were to fail you can still charge both banks by using the BOTH setting when the motor is running.

[Capn_Tom]

Maine Sail,

Can you provide more detail on your custom copper bus bridging the ANL fuses? It certainly cleans up the installation compared to runnning individual wires from each fuse block to the positive bus.

[Maine Sail]

Just ordered some copper bar stock 3/4" wide X 3/16" thick from McMaster Carr item #8964K241. I then lined it up and drilled it in my drill press. I then coated it with NoOxiD terminal grease to prevent corrosion. Really wish Blue Seas would just make these in a tin plated version.

[Denise]

Maine Sail,

I have another concern regarding the wire size from my Iota DLS 45 charger to the batteries. I had originally planned on 10AWG but now that I have it here I'm feeling really skeptical about the appropriateness of it. The distance between the charger and the batteries is 9 feet. What would you recommend for wire size in this situation? I'm thinking more like 6AWG.

Thanks,
Denise

[Skipper599]

Don't want to sound over critical here but it was the pic of the batt terminals and cables with rusty fasteners and dry terminals that got me to wondering ... Why don't people coat terminals and connections with petroleum jelly? It used to be the standard thing to do.

[Denise]

I agree the current situation is pretty disgusting and it's about time I address it. Frankly it has scared me ever since I bought the boat. I was afraid to deal with it up to now. I'm never going to let this happen to my new batteries. I'm learning a lot through this process. Thanks for your comment.

[mitiempo]

Denise
With 45 amps at 18 ft both ways and 3% voltage drop I make it 6awg.

[Denise]

Thank you! I'm going to make that change then.

Do you know if it's necessary to connect the Iota charger chassis bonding lug to the boat's bonding system?

Denise

[mitiempo]

Denise
I would connect the chassis ground to the boat's negative bus, which is connected to the ground point on the engine. I am not a fan of complete bonding ( through hulls, etc).

[Denise]

mitiempo:
That would mean connecting both the charger negative wire and the chassis ground to the negative busbar, right? I wasn't sure about that. I guess I could put in a small negative busbar at the charger location and run one wire to ground from there. Does that sound workable?

Thanks,
Denise

[mitiempo]

Yes that will work if the distance to the negative bus is a ways away.