SOC advice

I assume SOC is state of charge. Am I right? I am keeping track of the house batteries with a digital Volt/Amp meter wired directly to the battery bank. Please recommend a brand name meter/s and how to hook it or them up? Assume they will be digital since one needs two decimal
places for a good reading. Do you use a fuse inline? Does the length of wire run alter the read out? I probably would be satisfied to just monitor the house bank, hence one would do. I am going to change the charger out this winter so I can leave it on all the time.

Here's a link:

Wiring & Installing A Battery Monitor - SailboatOwners.com

FF has posted somewhere in the archives on buying the pieces for a lot less money.

OK, Xantrex linkpro or link light.

Battery Chargers | LinkPRO Battery Monitor | Xantrex

This unit counts amp hours in and amp hours out keeping track of your batteries state of charge.

I've used this exact product on several boats and think its a must have item for any boat.

My Victron is a great unit as well. Easy as heck to install and use!

Victron BMV 602 Two Bank Battery Monitor

How to article:

Installing A Battery Monitor Photo Gallery by Compass Marine at pbase.com

Tom-

Using the voltage reading of your battery bank will only be an approximate indicator of the state of charge. And you have to let the batteries rest with no charge or discharge for several hours before even attempting it. Even so I don't think you can get any closer than 20% this way.

But having said that, it is cheap. Google 12 dc meters. Don't assume that digital is more accurate than a good analogue Blue Seas 8-15 V meter for about $30. Wire to your battery terminals with at least 18 gauge wire and put a 5 amp fuse near the battery in the positive wire.

As others have said, a battery monitor that measures amps and volts and integrates amps over time to give amphours in and out is best for cruising boat.

But if you are a casual overnight cruiser then the DC meter will work ok.

David

Highly recommend the Victron monitor suggested at post #4...A simple volt meter is near-useless in comparison.

The Coot has a Victron BMV-501 battery monitor (square device to the right of the inverter multicontrol) for the single house bank.

http://www.victronenergy.com/upload/documents/Datasheet-UK-BMV501BattMonitor.pdf

Moonstruck:

Yes if there is a discharge current, the voltage reading will be lower than if the battery has been at rest for several hours thereby providing a conservative indication.

When I was cruising full time I didn't have a working battery monitor (and Xantrex couldn't help me get my new monitor working right!!) but with about 3 amps of discharge current I used 12.0 V as my 50% SOC indication instead of 12.1-12.2. It seemed to work out ok.

David

djmarchand said:

Moonstruck:

Yes if there is a discharge current, the voltage reading will be lower than if the battery has been at rest for several hours thereby providing a conservative indication.

When I was cruising full time I didn't have a working battery monitor (and Xantrex couldn't help me get my new monitor working right!!) but with about 3 amps of discharge current I used 12.0 V as my 50% SOC indication instead of 12.1-12.2. It seemed to work out ok.

David

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David, that has paralleled my experience. With any significant discharge current going out, my voltage meter will read about .2 volts lower.

Anybody who thinks they can use voltage as a substitute for a SOC meter is either kidding themselves or simply doesn't know any better. You can buy a Trimetric for well under $200 and they're dead simple to install so the real question is "why wouldn't you?"

bobofthenorth said:

Anybody who thinks they can use voltage as a substitute for a SOC meter is either kidding themselves or simply doesn't know any better. You can buy a Trimetric for well under $200 and they're dead simple to install so the real question is "why wouldn't you?"

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Didn't say I wouldn't. Just discussing the digital voltage read out. $200 is chump change. I have been checking out the various SOC meters. Because we have in the last year or so changed out cruising style, we are checking out a lot of things. Thanks for mentioning Trimetric.

Appreciate the discussion. Our boat sits at the dock much of the time. The only thing we have drawing current at the dock is a bilge pump and that is infrequently since the shafts don't drip after at the dock for a day or two. Rain water intrusion is minimal. Boat only cost us $25,000 and we did have work to bring it up to functional use, which is different than most of yours. Understand $200 might be chump change for a Sabre 42 owner but for us, considering our use and need for battery monitoring, or lack there of, I'll hard wire to a Harbor Freight $2.00 VOM before we got all out for a true SOC system. I could have been more specific and indicated I was looking for an inexpensive meter I could locate at the helm or such and hard wire. I'll check out the referenced volt meteres, $15 to $20 is our chump change reference. Thanks

If the boat sits at the dock most of the time then SOC is likely irrelevant to you anyway so your solution will probably serve you well. Just don't kid yourself when away from the dock that battery voltage will tell you much about SOC unless you're prepared to go to some extremes to take your readings.

Fighterpilot said:

I'll check out the referenced volt meteres, $15 to $20 is our chump change reference. Thanks

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Sorry, Fighter Pilot, that was not intended specifically for you. As you know $200 can go pretty fast on a boat. I also did not mean that I would not consider fairly carefully any addition to the boat that requires cutting holes. That being said, I think the best value for the money is the Victron monitor. It seems the simplest by far to install, and I like the simple way to move between functions. Now, I have to decide if the one or two bank model is needed. The two bank model is $40 more, but I can't see a real need to monitor a starting battery. Maybe I should. Maybe not. At any rate a SOC meter will probably be added when the 3 stage voltage regulator is installed.

When I said that we had changed our cruising style, I was referring to the fact that we have decided we like anchoring as much as possible. We upgraded our dinghy, so now Lou's feet don't get wet. We can also now transport 4 adults. That makes anchoring a much easier proposition. We like cruising with just the two of us, but we also like to share the boat with friends and family----especially the grand children. As they start into the college age we will see less and less of them.

On another note, I was checking into satellite TV, but when we moved the boat to South Florida we found so many digital broadcast channels that we don't think we need satellite. Now, I just have to learn to speak Spanish to be able to watch all those channels.

A question for you tech savvy guys. My set up is two 80 alternators. I just had them checked out at the alternator shop. They say they are really good. The current setup is one on the port engine is dedicated to the house battery bank. The starboard engine alternator is dedicated to the starting and bow thruster. The banks are completely isolated unless a battery switch is turned to parallel them. I like keeping the starting bank isolated to keep from house use discharging it.

The bow thruster is hardly ever used. The starting bank recharges quickly, and the volt meter drops to float. Is there any way to add the starboard alternator to the house bank for charging only? With a total of 160 amps max on tap, it would be a shame to buy another alternator, unless they can't be tied together for charging only.

Moonstruck said:

A question for you tech savvy guys. My set up is two 80 alternators. I just had them checked out at the alternator shop. They say they are really good.

Click to expand...

Don, why do anything to a perfectly fine and standard setup? Mine is identical, except for larger alternators. I have separate BMKs (Magnum shunts OMG!) for both house and start batteries to give me something to watch. In a pinch I assume you can always run your genset to charge the lazy/low bank.

sunchaser said:

In a pinch I assume you can always run your genset to charge the lazy/low bank.

Click to expand...

Thanks. You are correct, and that is what I have been doing. I have a 12KW NL generator and a 60 amp Charles battery charger. I just thought that I was wasting a lot of alternator potential. The icemaker and fridge both run through the inverter, so the port alternator could use a little extra help to cut down on generator time which is usually about 3 hours per day at anchor.

Don: Call Ample Power in Seattle. They have many alternator/voltage regulator combinations available.

Dual Alternator Controller

Greetings,
Mr. Moonstruck. Seems you have two starboard engines. Hey....is this one of those four engine set-ups I've heard about? No worries, I think I know what you mean. As far as "wasting" alternator power I think the alternator only produces the amount of power called for so if you battery is fully charged, it produces zero. Leave it like it is until such time you get a larger alternator for the house bank or talk to Larry M's contact.

Mr. RT. good catch. I have given up my study to my son who is a writer for a couple of weeks, so holding the computer in my lap. Difficult to type, and difficult to read. Edits have been made. Probably alternator potential would be a better word.

Larry's suggestion is a good one, and very much worth looking into. I have checked out the link, and it is interesting.

I love spending time with my son, but it will be good to get my study with a desk back.

Greetings,
Mr. Moonstruck. Ah, what parents won't do for their children.....Get one of these...
Amazon.com: Three Cheers Zebra Lap Desk: Home & Kitchen
Aw rats. Edited your post huh? NOW it's going to make ME look dense. I assure you I need NO help in THAT department!....Um, er...no wait.... Thanks....
(Folks, post #16 used to read, and I paraphrase...."starboard engine charges house......starboard engine charges start and bow thruster" Just so ya know.)

Don: it is perfectly possible to direct the charge from both of your alternators to the House bank and then 'trickle charge' your Start/Thruster battery from the House bank. Many newer boats are set up this way and I changed my traditional like-yours set-up years ago to this model. This is the configuration recommended by PassageMaker's technical guy, among others. It makes a lot of sense: why have a perfectly good alternator sit there idle when it has completed its Start bank re-charge a few minutes after leaving the marina? And why upgrade one alternator to a large-case high-output 160A model (likely requiring new engine-mount brackets, cable upgrades, regulator upgrade, etc) when you have the capacity already installed?

Both Ample and Balmar make charging products to achieve what you are contemplating...& maybe others too that I don't know about. In the case of Balmar (the gear I am familiar with) you need their 'smart' regulators ( a good idea anyway to optimally charge your batteries and extend battery life); a CenterFielder to combine the charging output of both alternators and send the full charge to the House bank; and a DuoCharger to trickle-charge the Start bank from the House supply. Apart from rapidly re-charging your House bank and doing so optimally, the Balmar gear can be configured for different battery technologies. For example, you might like to use Trojan 6V golf cart batteries for your House bank (relatively inexpensive; easy to move around; truly deep-cycle and Optima spiral-wound AGM batteries for your Start bank (optimized for short high-discharge tasks like the bow thruster and starting; not as voltage-sensitive as many AGMs). The Balmar gear will apply specific charging profiles to the different battery types, allowing both to be re-charged optimally and freeing you up to chose the battery type to suit the application.

Take a look at this link to Balmar's diagram on how it is done: http://www.balmar.net/PDF/Centerfielder%20Manual.pdf

Greetings,
Mr. Aquabelle. EXCELLENT reference! Thanks

Don, if you desire to do something, you may find it more advantageous and easier to install a larger alternator for your house bank, for about the same $$ as installing "charging products." Plus you'll then have a spare alternator!

To build a little on Aquabelle's excellent explanation, there is a Xantrex product called an Echo Charger which will accomplish the same thing as the Balmar Duocharge and you don't actually need to use the Centrefielder. Its about a year since I did the research but as I recall all the Centrefielder really does is protect the alternators from a field voltage in the event one of the engines is shut down. You can accomplish the same thing by using a NO oil pressure switch in series with each alternator field and control both fields in parallel off a Balmar 614. Which is in fact how I wired Gray Hawk last winter. The Centrefielder appeared to me to be a solution in search of a problem that didn't really exist for most applications BICBW.

For the engineers in the room its not a very professional drawing but its what I have. (on edit: apparently I can't attach a PDF so we'll try this again)

(further edit) - the Xantrex Echo charger is independant of the non-need for the Centrefielder. I don't think I made that clear - you could use a Duocharge to accomplish the "trickle" charge and still wouldn't need the Centrefielder.

What a great resource this forum is. You guys are awesome. Thanks all.

SCAN , Scan , Scan is the watchword .

The hassle is most folks dont .

The true chump change solution is a low voltage alarm.

IT will monitor the batt voltage and scream at you when the V reaches your preset.

What ME worry?


LowBat 12v Low Voltage Monitor and Alarm LOWBAT-XL Length: 2 7/8
Width: 1 1/2
Height: 1
Weight: .3
Shipping Weight (lb.): 1
Warranty: 1 Year

$39.00
Part # LOWBAT-XL

Samlex 12v/24v 6.6 Amp Low Voltage Start Solsum Controller Solsum6.6f Length: 5.7
Width: 3.9
Height: 1.2
Weight: .4
Shipping Weight (lb.): 1
Max Current, During Bulk Charge: 6.6
DC Output Voltage: 12/24

$34.00
Part # Solsum6.6f

Bob's solution (at post #26) is very creative and certainly lower-cost, involving only one quality regulator and no Centerfielder (the Xantrex EchoCharge is around the same cost as Balmar's Digital DuoCharger, but only passes 15A (vs DDC 30A); and cannot be set up for different battery technologies, meaning whatever charge profile is applied to the House bank is imposed on the Start bank too. I think the DDC is the better kit for that purpose.)

The upside of the (higher cost) 2-regulator + CenterFielder solution is that you get two features not noted in my original post,viz: battery & alternator temperature monitoring.A battery's (or battery bank's) acceptance charge is highly temperature-sensitive and this also varies with the battery technology. So a regulator that can be set for a specific battery type (flooded, gel, etc) and which comes with a battery temperature sensing thermocouple, allows the charging rate to be automatically regulated and optimized over seasons and even during the course of a cruising day, as temps change. This is all about re-charging as quickly as possble consistent with long battery life, so this is a really valuable feature & makes a big difference to re-charge times in my experience.

Alternator temperature sensing is a real favourite of mine: the Balmar gear adjusts the output down of an alternator that is running a bit hot until it has cooled somewhat and then brings it back up to full output when its temperature has stabilized. The % of field adjusted and the temperature set-points are user-programmable. You might be surprised, when you contact an alternator manufacturer and ask them what maximum temperature they are happy for their alternators to operate at for extended periods, at the answers you will get: marine environments are very different to automotive and often with our installations, air flow & cooling of the alternator is nothing like it is on a truck.

The bottom line: different solutions with different costs and levels of sophistication are available, but the practice of directing all twin-engine alternator charge to the House bank in the first instance is a great idea if you want to minimize genset use. In my own case, 4-5 days out on the hook with lots of AC gear& a 3000W inverter (sat TV, dishwasher, electric oven, laptop charging, teenagers & other hi-demand consumers) involves no genset use or solar panel at all, just a move of a couple of hours/day between anchorages.

Aquabelle and Bobofthenorth,

Thanks much, that is what I will look into. With the SOC meter, I have learned that I have been erring very much on the conservative side. I have found that I can run the fridge, all lighting, pumps, TV, DVD player, and the icemaker 12 hours without recharging. I had been shutting down the icemaker at anchor. It is a power hog, and we could probably go 24 hours without it.

I will probably change to a larger alternator or add a Balmar echo charger to the starting bank to save ginny time for recharging. This has been a learning experience. Thanks to all for the input. It is really appreciated.