Battery set ups

[Soundevice]

Hello!

I've been thinking of different ways to set up my batteries as I'd like to potentially rewire much of the boat and would like to have a solid plan before starting on that project. My main question is how y'all have your batteries set up to use between starting and house and also, especially, charging setup. I would like to use a solar trickle charger to keep the batteries topped off but from what I understand, would entail either leaving the switch set to 'both' when away or bypassing the switch and directly charging (with proper fuse) the batteries. My concern would be if I run the engine through say battery 1, that means only battery 1 is getting charge from the engine and then charging both batteries with the trickle would cause an uneven charge resulting in issues. Or would you run the engine with 'both' switched, risking the potential to run both batteries down if there was a charging malfunction.
My other thought would be to run 2 completely isolated systems- one for engine and one for house charged with the trickle. I currently have (2) one year old house type batteries of matching models in good condition and I feel like I would need to switch one to a higher cranking battery for the starter? There seems to be A LOT of contradictory info online and leads me to believe there are many ways to set these up!
Also, I'm really not using much house power at all as I have a bluetooth speaker (charged on shore) and solar string lights covering most (maybe all) my non engine running needs...
BH

[OverEasy]

Hi Soundevice

We use a system that lets us select one battery to charge and another to be used in our vessel.
It was adapted from a system we made and used for our RV Trailer for many years.

The post link is below:

https://macgregorsailors.com/forum/view ... EM#p349233

Post title:
Dual Battery Select Charge / Use Control Use System.

Hope this helps.

[OverEasy]

I can’t seem to type worth a darn….

Title is:
DUAL BATTERY SELECT CHARGE & USE CONTROL SWITCH SYSTEM

[Soundevice]

Thanks for the link, I did find your post after initially posting this. Your system looks great and I'll post my questions to that thread. After reading about your setup, I went to the boat last night to start picking through the, what looks like, multiple generations of work done. My plan is to clean up and simplify the system and get some type of solar trickle charge set up. I've ran a lot of house wiring but am pretty new to the nuances of 12V, especially the charging aspect. It's actually been a lot of fun to learn about and I appreciate your and other's expertise!

Ben H

[Be Free]

I have four 6V deep cycle batteries for house loads and a dedicated start battery.

Each pair of 6V batteries are wired in series to give me 12V and they are in turn connected to a off/1/both/2 battery switch. That way I can use them as two independent house banks or connect them in parallel to combine them for twice the AHs (the normal configuration).

The start battery is connected directly to the engine. No chance of blowing diodes by disconnecting the battery by turning off the battery switch while the engine is running. It also means I can tilt the engine up and down while it's on the trailer without having to climb into the boat to turn on the batteries.

The house bank(s) and the start battery are connected through an automatic charge relay. If either either the start battery or the house battery is being charged it will temporarily tie the house and start batteries together and then disconnect them when the charging source is removed. Right now that means that after I start the engine the alternator will charge both the start battery and the house bank(s) as long as the engine is running. As soon as I get around to putting the solar panels on the house bank it will be able to charge from the house side to the start battery as well.

Each of the three banks have their own independent charge source while connected to shore power. I disconnect the ACR while using the AC battery chargers. They are "smart" enough to be confused by the interconnected batteries. They would figure out what to do eventually, but I just hate to see them struggle.

I like to spend multiple days and nights "on the hook" when I'm sailing. I seldom do day trips and I have never spent the night in a marina so my set up is designed with that in mind. Your usage pattern will have a lot to do with how you set up your batteries and what type of batteries you use. The batteries will dictate a lot of your wiring decisions. Size your cables for the designed loads (plus a safety factor) and size your fuses to protect the wires.

[Tomfoolery]

I only have two marine ‘deep cycle’ 12V batteries. ‘Deep cycle’ because they’re sort of combo batts, not true deep cycle, like 6V golf cart of forklift batteries. A simple 1/2/both/off selector switch, but I only use one at a time, and alternate between boating sessions.

My charger has two outputs, so shore power charges both at once, as required.

If you wanted to keep them separate, use a charge relay and let the OB charge one of them with the relay passing charge current to the other. But that’s fancy - I like simple.

[Soundevice]

Very interesting and I am going to spend a bit of time checking out the 'automatic charge relay'. You both (Be Free and Tomfoolery) mention charging 2 separate batteries at once using the auto charge relay set up or a charger with 2 outputs. Do both of these separate the charge so if the batteries are at different charge levels, they will detect and slow/stop charging separately? From what I understand (barely!), a charger charging 2 batteries with different levels of drain will focus the power on the lower level battery and never fully charge the higher charged battery.

Again, I'll look up the auto charge relay as that sounds like what I would use to properly charge 2 different systems. Hopefully between the alternator and a solar trickle I can keep the batteries topped off and properly maintained. I'm possibly reaching out a bit prematurely as I plan to digest more of the info regarding charging these systems. My issue is I am using the boat now and while the batteries seem fine (resting charge for both stays at 12.8V), I don't want to screw anything up by running them incorrectly. I've been starting and running the engine on 'both' so that they drain and charge simultaneously but some on this forum say to not do exactly that! This is why I am looking for a set up to mimic until I can wrap my brain around the how and why and come up with my own customized solution...

Truly, thanks for the info guys!!

[Be Free]

First things first... Make sure the charger you put in your boat is designed for marine use. The clip-on automotive chargers are not designed to be used in an enclosed space and may present an explosion hazard. A good marine battery charger is probably

The second thing is to make sure that the charger is designed to charge the chemistry of your batteries. If you are using FLA (flooded lead acid) batteries (that's probably what is in your car) then you probably won't have any problem finding a charger. They are the most common.

The next one to look for is AGM (Absorbed Glass Mat). These are becoming more common. You might even have one in your car. They prefer a slightly different charge profile for maximum life so make sure your charger will handle them.

The other battery you may decide on is LiFePo (Lithium Iron Phosphate). These are often referred to as Lithium Ion but they are chemically different and do not entail the fire/explosion risk of early lithium ion batteries. They will need very specific charging and battery management.

Marine battery chargers are usually designed to charge multiple banks independently. I'm pretty sure I've seen them up to five banks.

Unless you get a very old charger it is going to charge each battery separately. One can be discharged and the other mostly charged and it will give each one what they need up to the capacity of the charger. If you get a reasonably modern charger it will switch some of the capacity to the more discharged battery after the other battery is charged.

[Be Free]

On to the ACR (automatic charge relay).

The ACR does the same thing (while you are charging) that the 1/2/both/off switch could do manually. Suppose you have a start battery and a house battery.

When you anchored last night you switched your battery selector switch to the house bank so you would not accidentally kill your start battery overnight. You've used some portion of the capacity of the house bank over night.

The next morning you switch the selector over to the start battery and crank up your engine. Then you switch the selector to all so that the engine can charge the start battery and the house battery at the same time. When you shut the engine off some time later the start battery is probably charged and the house battery is probably partially charged (depends on how much you used last night). You might switch back to start, you might leave them connected. It sort of depends on how dead your house bank was. If you have solar you'd leave them connected so the panels could finish charging the house bank and maybe put a little more into the start battery. We are now back to being anchored. If you remember to switch over to house only everything is cool. If you forget, you might kill your start battery tonight.

With the ACR in place it looks more like this. If you have a battery switch it is set to your house bank. The start battery is connected to the engine. The ACR is connected between the house and the start bank's positive terminals. While the engine is running it will be providing power to the start battery only. When the ACR sees that the start battery is being charged it will connect the start and the house banks together (just like "all" on the selector switch). The available charging capacity will be shared between the two banks in a ratio that is dependent on the internal resistance of each bank which is in turn related to the state of charge of the bank. Mostly that means that the battery that needs the most gets the most but both will get something. When the start battery does not need any more (which should happen fairly quickly) the house bank will get all of the charge (sort of). When the engine is turned off the ACR will see that there is no charge source in play and it will disconnect the banks. No chance of killing your start battery while the house bank is in use. If you have solar then the ACR it will be connected to the house bank only and the ACR will connect and share with the start battery as long as the panels are providing a charge source and as long it is needed.

Clear as mud yet???

[OverEasy]

Ya lost me at ‘On to the….’ ‍




No, ACTUALLY THAT IS A GREAT DESCRIPTION OF WHAT AN ACR IS SUPPOSED TO DO!!!
Especially the ‘sort of’ statements which is functionally as accurate as one can get!
Great write-up BeFree!

[Soundevice]

You pretty much nailed my situation in the paragraph describing using the switch and I am currently using the dual batteries as you wrote with the exception that I really don't use much house power at all. The marina where I'm moored has no electricity or water (its cheap though, how I like it!) so my plan is to eventually get a solar set up. The ACR sounds like exactly what I'll need to install and will, unfortunately, entail getting a starting battery. I've attached a couple pix to relay what I'm getting into. Your pix of the tidy bus bar of circuits (in other post) has definitely inspired me to go through and delete what I can and organize what stays, great job on that!! I also caught you have a degree(s) in electrical engineering so I won't be too hard on the previous owner of my boat!
I will reserve any other questions until I get further into this project and from the replies to your other post, I've gathered there are strong opinions regarding lithium type batteries. Its been a busy week but I'm looking forward to looking into the ACR and also an appropriate solar charging system.

Thanks again, great information!

[Be Free]

Specifically for Soundevice (you may already know this but a good teaching moment for all) in no particular order....

When stacking connectors the smaller/lower amperage connectors should be on top.
Never use wing nuts on the battery terminals. I know they come that way but it is wrong. Proper nuts with a lock washer please.
You need to fuse your battery cables within 7" of the battery with the type wiring you have.
FLA batteries need to be in a proper box to contain spilled electrolyte. The lid also reduces the opportunity for shorting across the terminals.
Batteries need to be tied down with a proper strap.
Some of the crimps on your cables are marginal at best. This may be a source of corrosion or heat. Neither is good.
The connectors on the back of your battery switch need to be protected. They are all positive so they won't necessarily hurt anything if they short together but they should not be exposed.

The mass of wires coming out of the overhead are ugly but actually not too bad from a functional standpoint. Replacing the "suitcase" splice with a proper butt splice is the only thing I see. My boat had some exposed wiring in about the same spot when I bought it but I was able to run all of it in such a way that it no longer showed.

Since you say that you don't have much in the way of house loads the batteries you have may be sufficient for now. They are better start batteries than house batteries but they are rated at 65AH. That is not too bad for a dual use battery. You don't list your outboard but as long as it's not over 50HP or so one battery should have no problem starting it. If you are anchoring out you should probably only run off one of them so you can keep the second in reserve for starting the engine. Unfortunately that means you will only have 32.5AH available for house loads if don't want to abuse your batteries. If I were to design your batteries I'd put in some true deep cycle batteries for the house load and keep using the batteries you have as start batteries.

[Starscream]

My setup is similar to what has been described above:

Dual 12V AGM optima blue-top batteries, with selector switch. I think they're about 60Ah each.
Single-bank Minn Kota marine charger wired to one battery.
Solar charge controller wired to the same battery.
BLUE Seas dual-sensing ACR (automatic charging relay) connecting the two batteries, so that if a charging voltage is detected at either battery from the motor, solar, or charger, then it combines the batteries and allows the source to charge both batteries.

Wiring diagram us below, although I did make a couple of changes and should update the dwg. I honestly don't remember if my solar is in parallel or series right now, but it works perfectly.

Last Friday we were out on a boat trip, and had to watch the Habs eliminate the Golden Knights, so we ran the inverter for about three and a half hours to power the laptop, along with lights and water usage and cellphone charging for 5 people, battery #1 couldn't start the motor in the morning.




You can do a forum search for "solar acr" and find all the details.

Go Habs go.

[Soundevice]

Wow, excellent info and exactly what I was hoping for!
Thanks to BF for the personalized appraisal of the pix I sent. All items you mentioned are being addressed and I'll upload pix to show progress. I actually ordered Nigel Calders book so I can get more info on the basics and hopefully write a little more intelligently about my set up.

StarScream diagram is great as I plan to have a similar set up though I don't have access to shore power (at my moorage.) I note the fuses (90A) off the positive leads which I apparently don't have. I also noted that you have the ignition leading to the ACR?

It's been a busy, HOT week in Pittsburgh so I haven't braved going under to continue mapping the wiring but we are heading out today to look at more items. I will hopefully have a map shortly and will upload a pic if any interest. Again, I appreciate all the input and I have been pouring over any lit I can find on my crash course to getting the boat proper!!

[Starscream]

I used 90A breakers, not fuses as I incorrectly show on my diagram. They are required for the ACR. Sizing was per per ACR installation guidelines.

My boat doesn't have fusing at the battery terminals, so the motor wires (1-gauge) between the motor fuse and the battery bank are unprotected, as is the wire to the battery selector and the wire (10 gauge) to the main fuse panel.

The ACR has an ignition interlock that senses the start current before it rises dramatically, and un-links the batteries super-quickly when the ignition key is turned, so that only the battery(ies) selected at the switch are connected to the starter during cranking. Tbh I ran that wire to the pedestal but then never connected it. For my cranking amps it's not really required and I didn't wanna mess around with the motor wiring. Tbh#2 I also didn't install the ACR on/off switch, so it's always on, even in storage, but so little current is drawn that it doesn't draw down the batteries noticeably over a 7 month storage period.