I’m Tweaking My Battery Banks and Need Advice

[reuabyor]

I am updating my battery system on the boat (1989 Catalina 30); I’ve included a crude diagram of it currently. I want to add an Isolator to the mix to keep my starting battery from draining accidentally and I want to add a Battery monitor. I am not sure where to wire each of these and how. I’ve read that if the alternator is jumpered to the starter, which I believe my M25XP is, then I need to disconnect that jumper and run the cable direct from the Alternator, but I don’t know.

I‘ve already bought a Renogy 500A Battery monitor that runs off a shunt and a FET 3 Bank Isolator. I just don’t know where to insert all of that, and I don’t know if I need to change the way my altenator and starter are wired.

Any help or advice would be great

 

[dlochner]

If you haven't yet visit MarineHowTo.com to read the excellent articles on batteries, charging, monitoring, and isolating among others you should before you go any further or spend any more money.

Factory wired alternators are typically tied to the starter. This is done for expediency during installation, lower cost of installation, and fewer warranty claims. It is not necessarily the best way for battery charging, especially if the house and start batteries are separate as they appear to be in your schematic. When alternator output is directed to the starter first the battery that was used to start the engine will be charged first and reach full capacity quickly as very little energy is used to start the motor, something around 1 ah or less. This often leads to under charging the house bank. See the article on MarineHowTo.com on ACRs, automatic charging relays.

The Renogy Isolator you have has a serious limitation in that it will induce a voltage drop when the batteries are being charged. This will lead to shorter battery life because the batteries will not be properly charged causing them to sulfate more quickly. A better way is to use a relay based isolator, like the Blue Sea ACR (Automatic Charging Relay). There will be no voltage loss across this relay. Blue Sea is an outstanding company to do business with, their products are top notch and they have lifetime no hassle warrantees.

Battery monitors also come in different flavors, some are better than others in accuracy and ease of use. Respected brands include Victron and Balmar. In terms of accuracy and ease of use, the Balmar SG 200 is far in the lead. Victron has a good reputation for accuracy, but it does require programming with an accurate measure of battery capacity and the Peukert number for the battery. If this information is entered inaccurately, the SOC will not be accurate.

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[JamesG161]

In addition to Dave's comments.

You are mixing battery types. AGM and Lead/Acid.

Jim...

 

[Maine Sail]

I am updating my battery system on the boat (1989 Catalina 30); I’ve included a crude diagram of it currently. I want to add an Isolator to the mix to keep my starting battery from draining accidentally and I want to add a Battery monitor. I am not sure where to wire each of these and how. I’ve read that if the alternator is jumpered to the starter, which I believe my M25XP is, then I need to disconnect that jumper and run the cable direct from the Alternator, but I don’t know.

I‘ve already bought a Renogy 500A Battery monitor that runs off a shunt and a FET 3 Bank Isolator. I just don’t know where to insert all of that, and I don’t know if I need to change the way my altenator and starter are wired.

Any help or advice would be great

May be better to ask quesgtions then gopurchase. I would not recommend the "R" brand to my worst enemy.That brand has the highest failure rate of any product we've seen in the marine industry in 30+ years...With two different chemistries aFET isolator may be the wrong choice..

 

[jviss]

A better way is to use a relay based isolator, like the Blue Sea ACR (Automatic Charging Relay)

Any even better way is an external regulator with remote sensing.

 

[reuabyor]

I’ve been researching this, posting questions and talking to experts from everywhere I could find for months. The products I’ve bought were very intentional based on what I’ve read. I was incorrect on the type of starting battery. It is also a flooded battery.

Having said that, I know there are widely based opinions on ACRs vs Isolator(s) and when and where to use them. A Renogy battery monitor may not be everyone’s choice but in the grand scheme Of things, the monitor doesn’t run the boat. I can switch that out if need be.

My choice to use two 6V in series, some may not like, but that’s the route I’ve decided on.

I’ve read a lot of stuff Maine Sail has written and I’m learning. Please bare with me as I fail and learn and tweak the install and products along the way.

 

[dlochner]

Having said that, I know there are widely based opinions on ACRs vs Isolator(s) and when and where to use them. A Renogy battery monitor may not be everyone’s choice but in the grand scheme Of things, the monitor doesn’t run the boat. I can switch that out if need be.

From my perspective the most important thing in a DC system is the battery monitor. Without it you do not have a good idea of what's going on with the charging, storing, and consumption of your battery's energy. Buy cheaper batteries, spare no expense on the monitoring system.

My choice to use two 6V in series, some may not like, but that’s the route I’ve decided on.

For many people this is the route to go in terms of cost, efficiency, and robustness. Having 4 GC batteries is even better. Every system has its limitations, there is no one right answer. I changed my batteries to FireFlys because the 4 GCs were no longer suitable for my intended use.

I’ve been researching this, posting questions and talking to experts from everywhere I could find for months. The products I’ve bought were very intentional based on what I’ve read.

On the internet, everybody is an expert or at least think they are. It is the wild west out there, be careful. I think you were given bad advice about the isolator. It may be appropriate for some charging systems. It is my understanding that emergency vehicles use them because their batteries are always fully charged in the station and out in the field the engines never stop running. The isolator essentially provides a float voltage which keeps the batteries charged while the engine is running, but does not really charge the batteries, only makes up for the current usage. This is not the scenario in sailboats. Our house batteries are often deeply discharged and need to be fully recharged via a good alternator or battery charger. The ACR does this quite elegantly and is affordable.

When designing your electrical system it is critically important to understand your needs and consumption. What's best for you , may be terrible for me.

 

[reuabyor]

The fact that I’ve probably been given bad advice is spot on, and even good advice I’m sure I misremembered.

I understand what you’re saying about the monitor. I am not against returning it and getting something else. What would you recommend?

The Isolator I got was the Victron Argofet 3 bank isolator because it doesn’t have voltage drop like others. My reasoning for going with an Isolator at all was because I was trying to make sure current didn't flow from my start battery to fill the house, and protect current from going back to the alternator. If an ACR is better for that then I’m all for it.

I have a M25-xp with a 51 amp alternator jumped to the starter. My plan is to run a cable directly from the alternator (I’ve been told that’ll save it if my kids turn the switch off while we are out) to the house bank with a fuse at the battery. For the starter, I Then I have to figure out which route to take with it on its way to the starting battery.

Please correct anything you see that I’m doing that’ll bite me in the rearend later.

 

[Maine Sail]

I’ve been researching this, posting questions and talking to experts from everywhere I could find for months. The products I’ve bought were very intentional based on what I’ve read. I was incorrect on the type of starting battery. It is also a flooded battery.

Having said that, I know there are widely based opinions on ACRs vs Isolator(s) and when and where to use them. A Renogy battery monitor may not be everyone’s choice but in the grand scheme Of things, the monitor doesn’t run the boat. I can switch that out if need be.

My choice to use two 6V in series, some may not like, but that’s the route I’ve decided on.

I’ve read a lot of stuff Maine Sail has written and I’m learning. Please bare with me as I fail and learn and tweak the install and products along the way.

The Only time we use an isolator diode= (NEVER) or FET= (for LiFePo4 installs). We use DC to DC then ACR's then FET isolators in that order depending upon chemistry.

Making Sense of ACR's

 

[dlochner]

I'm on my third Battery Monitor, started with the Balmar SmartGuage, worked well, but didn't tell me about the amps in/amps out. Added a Victron 704, great device told me amps in/out, watts, voltage, but the SOC function was a pain. This year I added a Balmar SG200 with the smart shunt and bluetooth dongle. What a nice system. Amps in/out, SOC, SOH (state of Health) Voltage, and it calculates the time required to be fully charged based on the current amp input. Just about everything you want to know. The original Smart Gauge is now used to monitor the start battery. The Victron has been passed on to a deserving soul.

I"m not familiar with the Victron Argo, so I can't comment specifically. Maine Sails article on the ACR explains the system much more clearly than I can. Essentially it only connects the two batteries when there is a charging voltage present, when a charge voltage isn't present on either side, then the relay opens and the batteries are disconnected.

You are correct if the alternator output by passes the switch then turning the switch off won't crash the alternator. There is a bit more to this than simply sticking another cable on the battery. Read the article on MarineHowTo on the 1-2-B battery switch and how to use it. Also read the articles on alternators to better understand your alternator and its strengths and limitations.

Keep learning. There is another website, BoatHowTo.com that offers a course on boat electrics, there is a fee for that course. (Been wondering about @mainesail's take on the website name. At I know he and Nigel are friends.)

https://boathowto.com

 

[jviss]

I had a bad experience with a battery monitor. I had a Victron BMV-600S. It was totally fooled by solar: as the sun went down and the current gradually diminished, it thought the batteries were nearing the end of their charge, and when it reached a certain point the Victron decided the bank was full, regardless of the actual state of charge (SOC).

The best monitor is your brain and experience with the bank. When you're charging and you see the current diminish to 2% of your bank capacity, they're fully charged. By experience you will learn how far that will take you, and when you have to charge again. (That's what I'm doing now.). The next battery monitor I expect to acquire will be the BMS for my anticipated LiFePo4 bank.

Monitors work for some, not for everyone.

 

[sesmith]

If you want to stay with Victron, I would have gone with their cyrix combiner instead.

https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-ct-120A-230A-EN.pdf

I would also swap the Renogy monitor for something else. I've been happy with my Victron Smart Shunt, but it does take some tweaking, especially if you have solar in the mix. I've read good things about the Balmar monitor here, and it might be a better choice.

 

[reuabyor]

Thank you all for the information. I will tweak as I can and update. This project is my latest. Most of the time we’ve been fixing the rotten core under the mast, painting the bottom and reglassing the rudder — for the most part. Just put the boat back in the water a couple Of weeks ago.

We are on a lake in SC and Our family fortunately loves sailing. We are anxious to get back at it.

 

[dlochner]

Thank you all for the information. I will tweak as I can and update. This project is my latest. Most of the time we’ve been fixing the rotten core under the mast, painting the bottom and reglassing the rudder — for the most part. Just put the boat back in the water a couple Of weeks ago.

We are on a lake in SC and Our family fortunately loves sailing. We are anxious to get back at it.

Looking good!

Knowing that your sailing will be on an inland lake makes a world of difference in the equipment and design as your needs will be different than someone who is coastal cruising and spending days anchored out or sailing. Temper all your decisions with that thought. And enjoy sailing.

 

[reuabyor]

Yep. We camp a lot out at islands on the lake but not for more than 3 days at a time.

thank you

 

[Stu Jackson]

I have a M25-xp with a 51 amp alternator jumped to the starter. My plan is to run a cable directly from the alternator (I’ve been told that’ll save it if my kids turn the switch off while we are out) to the house bank with a fuse at the battery. For the starter, I Then I have to figure out which route to take with it on its way to the starting battery.

I’ve been researching this, posting questions and talking to experts from everywhere I could find for months.

For me, there are two what I would consider trusted sources of boat electrical systems information on the internet: Maine Sail's and this Electrical System s 101` which I have built over the years with lots of links to not only Maine Sail's website, but to his other contributions on this forum and our C34 forum:
Electrical Systems 101 Electrical Systems 101

You are essentially trying to reinvent the wheel. We can help.

In answer to your alternator wired to starter question, Maine Sail covered that on his website on alternator wiring, and there's these on mine:

OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

1-2-B Considerations (New 2020 - Rod finally got around to diagramming what I had done in the above link in 2009 )
1/2/BOTH Switch Considerations

Noodle around on ES 101 and you'll find lots of his material, too, including ACRs and battery wiring options.

 

[reuabyor]

The sad part is I wasn’t trying to reinvent the wheel, I apparently am just an idiot. I have read a lot of your information on other forums and maine sails as well, it just never clicked until today. I think having three teenagers is starting to affect me.

 

[sesmith]

Teenagers...wire them in parallel and direct the output to a couple of splitting mauls. If it was only that easy...

 

[Bob J.]

I'm on my third Battery Monitor, started with the Balmar SmartGuage, worked well, but didn't tell me about the amps in/amps out. Added a Victron 704, great device told me amps in/out, watts, voltage, but the SOC function was a pain.

I've got a couple of Victron 702's. I gave up on the SOC function. I've played with charged current, tail current, charged detection time to no avail. Once I'm in the water 99% of the charging takes place with solar so I pay attention to AH consumed & compared it to AH produced by the solar controller over the course of a day. May not be perfect but many times the Victron goes to 100% SOC & the solar controller tells me I still have a bit more to go.

 

[Scott T-Bird]

The sad part is I wasn’t trying to reinvent the wheel, I apparently am just an idiot. I have read a lot of your information on other forums and maine sails as well, it just never clicked until today. I think having three teenagers is starting to affect me.

I think we all have made false starts on our boat systems ... I know I have. Just the fact that you are aware that improvements can be made and you are advancing the ball means that you have advanced far past the "idiot" stage. Don't sweat the mis-steps! Keep your eye on the ball! In baseball, you get 3 strikes, 3 outs and at least 9 innings! A 66% success rate is brilliance and will win the World Series!