Battery options

[mikeracca]

Ok so I found my house batteries and I’m not exactly thrilled. First off they are in a really odd location inside the chart table… but that’s not what bothers me the most. I’m not a fan of 6v batteries and I have 2 wired in series to give me a 12v house system. In my experience 6v batteries are just not very durable or forgiving, and finding a charger now days that can charge a 6v can be difficult. I have a tender that can do the job, but that is reserved for my motorcycles.

So my question is, is there a 12v battery or 2 that can fit in the house battery box that I can wire up in parallel and ditch the 6v series mess all together. I do not object to carbon or lithium type batteries. Unfortunately all I have been able to come up with is group 24 and 27 style in lithium or carbon.

 

[Tom J]

You don't say what size the 6v batterie are. I have four 6v golf cart batteries wired in series/parallel to give me a 12v house bank. These 6v batteries are charged, of course, with a 12v charger (in my case, solar). The golf cart batteries are better for my purposes than the old 4d 12v batteries.

 

[mikeracca]

Yea, I think these are the old almost square 4D group batteries. I couldn’t get a good look at the label. I just recognized them as 6v with only 3 fluid caps. They look almost exactly like these.

 

[Davidasailor26]

6V batteries are generally considered the better option for deep cycle use. They’re well respected and most people that have the space for them prefer them over 12V. With regard to charging - you don’t need a special 6V charger. You just keep them in series to charge them in pairs as 12V, the same as you would for a single 12V battery.

Good info related to battery selection and how 6V batteries compare -

What is a Deep Cycle Battery? - Marine How To

Light Cycle vs. Deeper Cycle NOTE: This article deals with FLOODED marine batteries, not AGM or GEL batteries. The Problem: The problem, as I see it, is one of dishonest marketing where multiple battery types wear the same clothes (sticker) and will perform differently when

marinehowto.com

 

[BigEasy]

4D batteries are bemouths that weigh over 100 lbs and require lots of space. A 4D. AGM battery from west marine is approximately $800 and is rated for 200 amps. A comparable wet cell 4D is $500 and rated for 135 amps. With the 2 Trojan golf cart batteries that you have in series, you get a smaller package dimensionally, less weight, and 200 amps. I would use the same configuration as you have now. As Davidasailor mentioned, 2 six volts wired in series can be charged with a 12 volt charger. You have lots of projects to get your boat in shape. Your electrical system is already configured for efficiency; replace your batteries with new Trojans, clean all contacts, check your wiring and charging system & you’re good to go ( on to next project).

 

[Tally Ho]

I just switched my bank to 2) 6-volt GC batteries. Wired correctly, as noted by other posters, they charge like a 12-volt battery.



Greg

 

[Ward H]

Mike, sounds like you're remembering the 6V batteries of old. I remember some cars using 6v batteries when I worked at a gas station in my youth. Not quite the same battery as the GC2 many of us are using in our boats now.
No need to go to specialized battery chemistries. Your flooded lead acid batteries are the choice for many sailors. No need to get into specialized chemistries at this point.
As for the location, I believe that was a common place for battery placement on the earlier C30s.

 

[mikeracca]

I know they will charge like a typical 12v when wired in series, I am worried about them becoming unbalanced where I would have to charge them individually to prevent a false peak or overcharging of one of the batteries. I used to have a charger that would monitor a 6v bank, as a whole and individually, but I made the mistake of letting a “friend” borrow it and I have never seen either of them again. I also have not been able to find that type of charger again. It was for RVs but of course 10 or so years later all the RV shops now carry the smart chargers for LiPo and Carbon tech, and not much (at least near me) for smart 6v.

Yea I had fuzzy memory syndrome trying to remember the group size for the old 6v batteries. I later last night found 4D batteries and yes they were the huge semi truck size.

Due to the other many many projects I have, and the fact that I’m not planning AC or a refrigerator at this time, I will keep up with a factory setup. I am planning on replacing the lighting with LED. I have several fixtures I bought to put in Lilly but never got around to it… now they have a new home.

 

[jssailem]

Two 6V batteries (225 ampHr) like the Trojan's are a good solution to provide a single 12v battery source on a boat. If one fails you are out of business.

My observation is that potentially leaves you with a single resource for your on boat power. Then you look into a separate 12v battery to be the starter battery for the engine. Next up is the charging systems both engine alternator and shore power. If is a never ending circle.

Or
You can look at DYNO Batteries in Seattle. They have a 12V battery that is DeepCycle. Fits in a standard 12V battery space. Each battery 135 Amphr (2 batteries 270 Amp Hrs) capacity and costs about $150 - pick up at the factory. Dyno Battery - Premium Quality Battery Manufacturing - Made in the USA
I have three of them on my boat.

 

[BigEasy]

You can look at DYNO Batteries in Seattle. They have a 12V battery that is DeepCycle. Fits in a standard 12V battery space. Each battery 135 Amphr (2 batteries 270 Amp Hrs) capacity and costs about $150 - pick up at the factory.
I have three of them on my boat.

John,
That’s a good value. I recently replaced my house bank with 3 AGMs (Duracell group 31 from Sam’s). They are only rated at 105 amps each and cost was significantly more than your Dynos. My previous Duracell’s lasted 7-8 years, not too bad considering that I completely drained them 3 or 4 times.

 

[Don S/V ILLusion]

I’m not a fan of 6v batteries and I have 2 wired in series to give me a 12v house system. In my experience 6v batteries are just not very durable or forgiving, and finding a charger now days that can charge a 6v can be difficult. I have a tender that can do the job, but that is reserved for my motorcycles.

actually, most 6V batteries are more “durable” and you don’t need (or want) a 6V charger.
A charger can’t differentiate how many cells it’s charging so connecting two 6V batteries in series is no different than charging one 12V battery. And deep cycle 6V batteries are better suited to deep cycle demands. Not to mention easier to manage.

 

[jeepbluetj]

I'd say two GC-2 6v batteries are by far the best FLA house bank you can have in a C-30. IIRC for 12v batteries G-24s fit under the chart table but G-27s do not. That'll greatly limit AH capacities of anything you'd switch out with. I had a 2 GC-2s from Costco on my C-30 and they lasted 7 years+ (Dunno how much longer, sold the boat). Ran a fridge all the time. 160W of solar when off the dock. Drained to nothing a few times when shore power failed and the solar was off.

I did add a small AGM under the starboard settee as a start battery. Never used it once.

Charge it with 12v. Don't worry about balance, they'll balance fine on float. Two FLA 6v's are six individual battery cells. One 12v FLA is six individual battery cells. Don't let em get dry.

And, they're awfully cheap. ~$200 for a new pair. Think about what these things are designed to do: propel little cars full of drunk golfers for ~4 miles each round. 3 or so rounds every day. GC-2's are designed to be rather abused and still function well.

 

[mikeracca]

actually, most 6V batteries are more “durable” and you don’t need (or want) a 6V charger.
A charger can’t differentiate how many cells it’s charging so connecting two 6V batteries in series is no different than charging one 12V battery. And deep cycle 6V batteries are better suited to deep cycle demands. Not to mention easier to manage.

This is exactly the issue I’m trying to avoid. If one battery get out of balance with the other over charging or false peaking can occur. This will damage one or both of the batteries. My old smart charger would prevent this by using a sense wire between the batteries and if it detected one getting more of a charge than the other it would stop charging one to let the other catch up. This is very similar to how LiPo batteries are charged to keep everything happy.

Even batteries made in the same month could have been made several batches apart and thus be slightly different, and this is what causes the imbalance. Sorry, but I have been working on cars, trucks,rvs, motorcycles and boats for 30 years and have seen many of these issues I’m trying to avoid pop up from time to time. Granted these issues don’t pop up every time, but Mike’s Luck is really good friends with Murphy, so I’m trying to prevent issues while I can.

 

[Ward H]

Mike, sounds like you know what you are getting into with regards to battery banks. Great!
For an alternate battery location, take a look under the starboard settee. @jeepbluetj mentioned he fit a starting bank battery in there. On the MkIIs the battery box is located there. Holds two group 24 or 27s. Can actually hold two group 31s if you cut out part of the divider.
Maybe you can relocate your batteries into that location.

My starting/reserve bank of one group 31 battery is located on the port side under the aft corner of the settee.

 

[mikeracca]

My current setup is 2 6v house batteries in the chart table, and a starting battery right next to the engine in the next compartment over. I’m not yet sure if my alternator on the engine is set to charge the house bank, I am still in the clean up the huge mess phase to have explored the wiring options as of yet.

 

[Stu Jackson]

This is exactly the issue I’m trying to avoid. If one battery get out of balance with the other over charging or false peaking can occur. This will damage one or both of the batteries.

I believe you are making a mountain out of a molehill & coming up with a 1962 issue in 2022. If you replace your 2 6V with 2 12V, what's the difference? About your "balancing act?"
Look, let's let reality bite: Hundreds of thousands of recreational boaters have either 2 or 4 or more 6V batteries to create 12V banks, or multiple 12V batteries. I've owned my boat for almost 25 years and had smaller boats for 15 years before this one.
You are describing a potential issue that simply does not exist.

 

[Tom J]

My current setup is 2 6v house batteries in the chart table, and a starting battery right next to the engine in the next compartment over. I’m not yet sure if my alternator on the engine is set to charge the house bank, I am still in the clean up the huge mess phase to have explored the wiring options as of yet.

Sounds like a good setup to start with.

 

[mikeracca]

I believe you are making a mountain out of a molehill & coming up with a 1962 issue in 2022. If you replace your 2 6V with 2 12V, what's the difference? About your "balancing act?"
Look, let's let reality bite: Hundreds of thousands of recreational boaters have either 2 or 4 or more 6V batteries to create 12V banks, or multiple 12V batteries. I've owned my boat for almost 25 years and had smaller boats for 15 years before this one.
You are describing a potential issue that simply does not exist.

Charging 2 12v in parallel is not going to result in an unbalance like a series charge can. And if I had a 24v system I would be just as worried about the unbalance in 12v batteries. The easy part of 12v is the multitude of different chargers that are available for them as compared to 6v if I did need to charge them individually.

Batteries in parallel will level each other out naturally so the unbalance effect doesn’t occur as easily.

 

[jeepbluetj]

Rod would link his own site: Batteries Archives - Marine How To

As far as balance is concerned, lets look at what a lead acid battery actually is:

So the top diagram is 1 12v battery.
The middle diagram is 2 6v batteries in series.
And the bottom is 2 12v in parallel.

The top two are exactly the same. Just cells in different boxes instead of the same box.
The paralleled bank, in my humble opinion, is more prone to an imbalance. Lets say in any case you end up with a shorted cell. The top two are low-voltage and poor performing banks. The paralleled arrangement will end up discharging the "good" battery constantly into the "bad" which will eventually make it go bad too. (Hence why most boats have a start battery to get out of dodge in that situation)

A underperforming cell is the same. In a paralleled arrangement it will discharge the other battery. In a series arrangement you've just got a weak battery.

But, as usual, Stu's right. Balance isn't a problem in the real world. If somehow you had a series bank where one battery was at 50% SOC and the other one was at 100% SOC, it'd be corrected to 100/100 with a long enough float. Equalize at the 12v level solves all kinds of issues too.

The real reason for GC-2s is bang for the buck. There is no cheaper way to plop in > 200AH of capacity that will easily last over 5 years if even moderately taken care of.

 

[Stu Jackson]

Charging 2 12v in parallel is not going to result in an unbalance like a series charge can.
....
Batteries in parallel will level each other out naturally so the unbalance effect doesn’t occur as easily.

Mike, WADR, this is simply not true. Balancing ANY group of cells, whether in series or parallel "could" potentially create an imbalance if the charging sources themselves were unbalanced.
An example of ways to best balance charging source connections to battery banks:

http://c34.org/wiki/images/4/44/Sma...ultiple_batteries_to_form_one_larger_bank.pdf

The reality is that if the connecting wires are properly sized for the load it is rare in recreational boats of our typical size (22 to 40+ feet) that the difference is even measurable between one end and the other. Batteries in any given bank are simply not that far apart to make much of a difference.

And given the fact that wiring recommendations like this link have proliferated in trusted publications pre-internet and are now so widely available on the 'net, it would be hard to find a troglodyte who has knuckles dragging so low he couldn't figure it out.

Mike, perhaps you could explain to us the difference between a box with 6 2V cells in it compared to 2 boxes of 3 2V cells wired together. [I wrote this before jeepbluej wrote his post#19.] What might have been true in days of yore is not true now. I believe the reality of what is commercially available for recreational boat use means that there simply isn't. Gazillions of boaters have proven that since recreational boating became a popular hobby/sport and that equipment for energy storage and charging has been around long enough now for the bad apples to have already fallen from the tree.

I think a greater dangers are from folks who:

--- still use more expensive $$$ AGMs when their drawbacks have been clearly documented
--- still use 4 or 8D batteries when they believe they are invincible and don't figure their backs could ever fail
--- still don't understand boat elekricity ("I don't know much about electrical on boats...") - none of us was born an electrician, we all learned; and if you are the artistic type who doesn't "do" math, then find someone reputable to do it for you and help explain it to you (not you, Mike you get it)
--- still ask about basic wiring diagrams (30 years ago, pre-internet, I could understand, now, sorry, no apologies accepted, it's all out there and there simply aren't that many different ways to do it; and we've also seen a significant drop-off in folks asking "Please critique my wiring diagram."! )
--- still think combining a good bank with a bad one will help them start their engines

The good news is that we're still here to help all of them.