Batteries - A Stupid Question

[jonelli]

I'm contemplating replacing the 3 year old batteries I have because I just don't trust they can start the motor every time.

BUT...Since it seems to be the norm to have two batteries, and always run the boat on one battery, and use the other for starting the engine, why don't people use two different batteries?

Deep Cycle/Dual Purpose batteries are not starting batteries. They only make two types, one for deep cycle discharge, and another for high current short term output. Why not have one deep cycle and one starting battery? They'll both still charge back up the same way, but one could deliver high current better for starting the engine.

I'm sure this has been discussed before, and I apologize if it is a dead horse.

 

[CharlzO]

Actually, what you describe is exactly how many boats are already set up. The difference though, is that instead of a single battery for each purpose, many will have a "bank" of batteries for the house side - the lights, electronics, etc. I can't speak to everyone, but I know that there are certain things in dealing with different types, and charging, and all that jazz, but the basics are just like you said.

 

[wufibugs]

Lotta folks will say that there's no longer much reason to have a dedicated starting battery especially if you have robust house bank.

 

[jonelli]

Maybe I'm just being paranoid. My boat came with a pair of Group 27 Interstate Deep Cycle/Marine batteries. I don't know if they are considered dual-purpose. My electrician friend says that there is no such thing. Just batteries that are either made as deep (big plates) and starting (thin plates), and marketing dictates if they call them "dual purpose".

Anyway, my batteries are from 2011, three years old. My experience is that if they are used regularly, three years is about when they start to fade away.

I don't know if I should consider replacing them right now, or just see how they fair for awhile. And when I do, would it be better to make one a starting battery instead? If I were to add another deep cycle to make a bank of 2 and still have 1 starting battery, where would you put a third battery? My 2 are under the seat, the nav table has drawers under it.

 

[dparilla]

Your deep cycle batteries are more than powerful enough to crank your motor. Keeping a starter bank separate from the house bank is a good idea, but you have tons of options on how to hook them up. A quick search of these forums will give to tons of opinions between a/b/off switches, echo chargers, charge relays etc. I highly recommend checking out the numerous post from Maine Sail on these exact issues.

 

[Anonymous 121765]

I got some advice years ago from a battery guy that said, it was better to have equal or same types of batteries for for charging & equalization. He said not all chargers work the same, especially the older analog types.

CR

 

[JK_Boston_Catalina310]

I just did two battery related projects over the last two years as part of my prep to go cruising. I think you will find that a really good balance of redundancy and capacity is to keep the 1/2/both/off switch you likely already have and make some changes to how the two banks are charged. Then you can go with a large primary bank (mine is 460 amp hours from 4 6-volt golf cart batteries) and a small reserve bank (I have a group 24 deep cycle).

Here are some links that might help you.

1st - Why you don't need much juice to start your battery https://www.youtube.com/watch?v=nrQXnqNOI9Q

2nd - Maine Sail's forum thread on the 1/2/both/off switch http://forums.sbo.sailboatowners.com/showthread.php?t=137615

3rd - Maine Sail's own website on making battery terminals http://www.pbase.com/mainecruising/battery_cables

4th - Maine Sail's own website again on fusing http://www.pbase.com/mainecruising/battery_fusing

5th - Blues sea systems info graphic on sizing wires, fuses, etc. (warning, larger pdf in link 30mb) http://assets.bluesea.com/files/resources/reference/20010.pdf

6th - Maine Sail's own website again on battery installation & orientation http://www.pbase.com/mainecruising/flooded_battery_orientation

7th - Maine Sail's forum thread on Battery Buyer = Good News (do you see a theme developing, they guy really puts out a ton of useful information. You should spend some time reading his stuff) http://forums.sbo.sailboatowners.com/showthread.php?t=132350

8th - Maine Sail's own website again on battery monitors http://www.pbase.com/mainecruising/battery_monitor

Lastly - my blog posts on how I integrated all of this info into my updated system. http://svsmitty.wordpress.com/2013/03/04/electrical-charging-system-upgrade-mostly-complete/ and http://svsmitty.wordpress.com/2014/04/28/battery-upgrade/

Good luck,

Jesse

 

[dparilla]

Nice Post Jesse. A great bunch of info should get anyone started!

 

[Chief RA]

Jesse, are you counting amp hrs of all 4 ea. 6 volt batteries for the total? If so, you can't do that if 2 ea. comprise a 12 volt battery series leg. 460 total would be 230 amp hrs per 6 volt battery. Chief

 

[CharlzO]

the 460 sounds about right, for 4 GC batteries wired as a 12v bank. My GC2s are rated at I think, 225 per battery, so two of them in series is a 12v, 225 bank, so doubling that would put about 450 in my case. I know there are some out there a little stronger, so that 460 would be accurate depending on the battery.

 

[Chief RA]

CharlzO: No problem then, I was just trying to clarify as I know many of us are aware that some total all the amp hrs for a real grand total! Thanks, Chief

 

[JK_Boston_Catalina310]

Jesse, are you counting amp hrs of all 4 ea. 6 volt batteries for the total? If so, you can't do that if 2 ea. comprise a 12 volt battery series leg. 460 total would be 230 amp hrs per 6 volt battery. Chief

Each 6 volt is rated at 230 amp hrs. I have them set up so that there are two series in parallel. So two 6 volts rated at 230 amp hrs connected in series to make one 12 volt rated at 230 amp hours paralled to an identical series for a 12 volt bank at 460 amp hours. Similar to the attached diagram.

 

[Chief RA]

Sorry Jesse, just trying to help! You got her right. Chief

 

[Maine Sail]

#1 There are three types of "marine" 12V batteries. Starting (thin plates), dual purpose (slightly thicker plates) and "deep cycle" (thicker plates). The only ones to use on a small cruising boat are the deep cycle version..

#2 the deep cycle 12V batteries are only "deep cycle" when compared to their sister batteries, starting and dual purpose, in Group 24, 27 & 31 12V batteries.

#3 A 12V G24, 27 or 31 deep cycle is NOT a True deep cycle battery like a 6V GC2, L16 etc. is. They are only "deep cycle" when compared to batteries in their family..

#4 There is less than ZERO need to use a "starting battery" on an M25... If your engine starts poorly on a deep cycle either the battery is toast, starter bad or the system wiring is extremely small or has high resistance corrosion.. Even a G24 deep cycle has 3X what you need in terms of CA..

 

[weinie]

#4 There is less than ZERO need to use a "starting battery" on an M25... If your engine starts poorly on a deep cycle either the battery is toast, starter bad or the system wiring is extremely small or has high resistance corrosion.. Even a G24 deep cycle has 3X what you need in terms of CA..

I know I'm taking a risk here by going against MS's wisdom , but:

I use 2 deep cycle group 24 batteries in parallel providing almost 200AH for both house and starting on switch position number 1.
I also use a starting battery on switch position number 2 whose sole purpose is as a reserve battery to start the engine if the "main" bank is dead. It gets topped off with a yandina combiner. It was one of the original boat batteries before I upgraded to the deep cycles and it was in excellent condition, so why toss it?

 

[Scott B]

#3 A 12V G24, 27 or 31 deep cycle is NOT a True deep cycle battery like a 6V GC2, L16 etc. is. They are only "deep cycle" when compared to batteries in their family..

Ok, 'splain that one......

 

[Maine Sail]

Ok, 'splain that one......

Most all 12V batteries, in the G24, 27 & 31 are deep cycle "imposters" including Trojan 12V G-24, G-27 & G-31... Some brands will give more "cycles" than others in these group sizes but none compete directly with a GC2 in terms of cycle life..

You are not just buying Ah capacity you are buying cycle life. There are 12V golf cart batteries such as the Trojan T1275, and they do have the same cycle life as a 6V, but they are also taller, like the 6V, and a built to use the same plates as a GC2 battery. G-24, 27 & 31 batteries simply do not have the plate thickness a GC2 battery does.....

For example in the Deka / Sea Volt / West Marine line you have starting, dual purpose and deep cycle G-24, 27 & 31 12V batteries which all share the same case. However they are only really deep cycle when compared to the starting or dual purpose batteries which share the identical case. They are not "deep cycle" when compared to the GC2 or other true deep cycle batteries..

Here's the data across the Deka / East Penn / West Marine line up:

Flooded Batteries - Group 24, 27, 31 & 6V GC2

12V Starting - Cycles to 50% = Not Rated
12V Dual Purpose - Cycles to 50% = 200
12V Deep Cycle - Cycles to 50% = 350
6V Golf Cart - Cycle to 50% = 700-1000


*Note: The above are LAB RATED cycles. Expect at least 50% less in the real world..


As you can see the 12V "deep cycle" battery is only a "deep cycle" when compared to the starting or dual purpose batteries it shares a case with. If you absolutely must buy a 12V G-24, 27 or 31 buy the deep cycle version. In many cases this is all that will fit. It is easy to see that these are NOT deep cycle when compared to a purpose built deep cycle battery.

The only ones that have lab rated cycles the same or close, to their own brands 6V batteries, are Lifeline and the US Battery DCXC 12V series (at least those are the claims). I know of no other brand that will rate their G-24, G-27 or G-31 at even half the cycles of their GC2 6V batteries. The Deka / East Penn / WM product is less than half...

Do yourself a favor and read this article:

What is a "Deep Cycle" Battery?

 

[jonelli]

Back when I originally posted this I thought I would leave everything as-is and see how it all goes before doing any big changes. Since then I have determined that my two G27 Dual Purpose batteries are indeed shot even though they test fine on a load tester. I've done a few overnight sails and couldn't get the house battery to stay above 11 volts for more than a an hour or two of less than 5 amps use.

I called Interstate just to get their advice for replacments, and as Main Sail described, the dual-purpose batteries are sort-of deep cycle wannabe's designed to give you some deep cycle-ability but also some extra cranking amps. The technician on the phone even said if it were him, he'd use only true deep-cycle batts along with a starter battery.

So, I'm about to replace my two main G27 batteries with just plain old deep-cycle ones. If Mainsail is correct, I shouldn't have any issues. but I really am curious about Weinie's setup. Where did you put the third battery?

Also, what size alternators come with our boats? I have an 87 MkII and I assume I have a stock alternator. Is it able to put out enough current to charge 3 big batteries? Or would I need to upgrade it?

 

[wufibugs]

I went with Maine's double boat switch setup and feel it gives maximum flexibility particularly since my budget condemns me to a charging system that has not been optimized. I'm still limping along with the Hitachi 35 alternator and it's dumber than dumb regulation. I can probably afford a 65 or 80 amp alternator but that will apparently do little without better regulation and charging management.

 

[jonelli]

Sorry to drag this battery discussion out. I was getting confused with these "Dual Purpose" Marine/Starting batteries.
A friend told me that there only two types, starting and deep cycle. That dual purpose, or DeepCycle/Starting batteries are marketing propaganda.
Wanting to understand, I did a lot of online research and made some phone calls to manufacturers. So, as Maine Sail said, the only battery to care about is the true Deep-Cycle. Anything else is not rated to cycle.

I found this on Sterline-Power's site and it is pretty much verbatim what my electrician friend told me... Take it FWIW...

The brutal truth about marine leisure batteries
http://sterling-power.eu/support-faq-2.htm

There is no such thing as a marine battery. If you see a marine label on a battery it is simply words and may as well say Mickey Mouse.

For cost and performance open lead acid batteries are king. All other batteries are a derivative of this, with variations to suit different markets, where there are specific problems implementing the standard lead acid battery. E.g. Gel, is a standard lead acid battery except that the acid has been transformed into gel. But by solidifying the electrolyte, you introduce many problems not associated with free flowing water based batteries.

“Most expensive is best” This is so not even close to being true. In fact I would say the reverse is true in the marine leisure market. When reading all the sales literature regarding Gel/AGM, please note that none of their curves and claims refer to standard lead acid batteries. (They know better). They never claim they have better performance than standard open lead acid, this is just an assumption on your side. They claim weird things including longer shelf life and that you can turn them upside down and have your dinner under them. Who cares? I want fast charging, long life, plus good value for money from my batteries. I don't want to sit and watch them on a shelf for a year and have my dinner under one.

If a statement says that this is the best battery. The question is, best at what aspect?

If the term 'maintenance free', is on a battery, then treat this with caution. There is no such thing as maintenance-free, all batteries are basically the same. A Gel, sealed lead acid and AGM are all only maintenance-free because of the reduced charging performance curves; and not because there is something special about the battery. If you charge a normal lead acid battery to the Gel or AGM curves, then they would not require maintenance either. Remember 'maintenance free' is a handicap to fast charging not an advantage. This feature, which on the surface looks good, is, in most cases the worst feature that you could possibly buy; as this feature dramatically limits the maximum charging characteristics of the battery.

Fast charging costs water, i.e. if you want to charge you batteries fast, don't touch a Sealed/Gel/AGM etc with a barge pole. Fast charging will result in a certain % water loss from the battery. If the battery is sealed the water loss cannot be replaced. REMEMBER FAST CHARGING AND SEALED/MAINTAINCE-FREE ARE A CONTRADICTION OF TERMS. You may not like this, but tough, it's the way it is.

Watch the term leisure / deep cycle as it simply does not exist. The standard, so called, leisure batteries, are simply starter batteries with extra support for the active lead material. This may increase the life by 5 – 10 %, but does not turn a starter battery into a deep cycle battery. True traction (deep cycle) are not available at a sensible price and are uneconomical to use for standard leisure use. However, if you plan to live onboard or travel the world then do look at 6 V or 2 V traction and build your battery bank up from those batteries, but expect to pay about 3 – 6 times the price of so called standard leisure batteries. On a daily use cycle, the standard so called leisure battery (which is a starter battery) will last you as little as 6 – 8 months whereas traction would last 15 years. But on a leisure rating (2 weekends per month and about 4 weeks’ holiday) then you would get about 5 – 7 years out of a standard leisure. That's if you charge it right using advanced regulators and constant current battery chargers).

Battery sales companies quote battery cycles such as 6000 cycles for the battery. This looks good on the surface, however it will be 6000 cycles at say 10% discharge. This is a meaningless figure. All batteries have a manufacturers' graph, which odds are, you will not see in full; as the embarrassing section tends to end up on the advertising company’s editing floor. The graph will have % discharge on one side and cycles on the other. This graph is sometimes shown on glossy battery information, but is normally censored at about 30 – 40% discharge, where the figures can still show 4000 cycles. What they fail to show is the 100% discharge cycle (which they of course say you should never go to and I am not for one moment suggesting you should). This, at the end of the day is the only ultimate datum point. Whichever battery performs the best at 100% discharge, will perform best at 50% etc. The interesting fact is that they are all about the same, that is, because they are all basically the same battery. A Gel and conventional starter battery go down the same production line until one has a gel substance put in it and the other liquid. The shock with this figure is that for Gel, Sealed, or leisure, etc, the constant figure is about 30 – 60 cycles, whereas true traction with thicker plates is over 300+. (However, don't expect to see this graph on glossy literature, as they are way too frightened of this graph and will not release it). It is however available from correctly specked commercial batteries.

So which is the best battery for standard domestic leisure use?

The job I am referring to is for auxiliary charging systems on boats, camper vans or vehicles. I am not getting into what each and every battery type is best at, or for; as each type has a market, it just maybe not this market.

To pick the best battery for your job, then at least understand how they work. Forget the actual chemical formula and all the fancy terms around. The bottom line is that lead acid batteries have been around since the 1st World War and the basic principles have changed very little since. The only thing we all agree on is that they are not environmentally friendly, but are cheap to make and will remain king until such time as someone comes up with a solution which can compete. Which by the way to date they simply have not. How do I know this? Well it’s very simple, if they had, the lead acid battery would be out the door so fast its toes would not touch the ground.

So how do they work?

Let’s understand the basics. They are all lead acid, but fall into 2 basic groups. A starter battery and a traction battery (fork lift truck, true deep cycle).

Type 1 (starter batteries). A battery is simply a bucket of energy. If you wish to get the energy out fast, to start an engine (cold cranking rating) then you need a large surface area (large plate size). The only way to get a large surface area into the bucket, is to make the plates thin, so they can squeeze into the bucket (this is your starter battery; it needs the cold cranking kick in order to start the car, so its plates are thin to achieve this). This theory is pushed even further with batteries which increase this surface area more, to make what are known as high torque batteries. These deliver even higher cold cranking, by putting the plates in a 'swiss roll' configuration, in order to make them thinner and increase the surface area. This is good for cold cranking, but has a fatal flaw when it comes to fast charging. (The problem is, it works too well when charging and destroys itself).

Type 2 (traction or fork lift truck batteries). These batteries are not interested in the cold cranking kick, which is required for a starter battery, but are still interested in the power in the bucket. So they can reduce their surface area of the plates. The good thing about being able to reduce the surface area is that you can make the plates much thicker. The end result is you still get the same power from the bucket it is simply delivered at a slower rate.

So, for deep cycle and long life, the traction batteries are by far and away the best. But their price tends to kill them. However, if you are doing a long journey around the world, or going away from the UK for 2 years plus, then investing in 2 volt or 6 volt traction batteries is a must, regardless of the cost. They will pay for themselves many times over. For general leisure use they are the best, but a bit of a waste of money, unless you intend keeping the boat for 15 years to get the use out of them.

So what's the end result of these two battery types?

A battery is made up of lead plates, with a lead paste on the plates. Every time the battery is used, then so many bits per sq inch fall off the plates, if you have a large surface area then a large number of bits will fall off. Then to make matters worse your paste is thin so you cannot afford to lose the paste. However, if you have a small surface area and thicker plates the same is true, but the plates are thicker and as such, you can afford to lose a small amount of paste. In a nutshell, that is it, or be it in very simplistic terms, those are the differences between traction batteries and starter batteries.

As you can see from the above 2 battery types, the plate configuration cannot be blended. If for starting, you have a large surface area of thin plates, for traction you have a small surface area of thicker plates. One is black and one is white, there is no grey area. So, if you are purchasing a battery and it has a cold cranking rating and the salesman says it is a deep cycle battery, but will also start your engine; then it is in fact a starter battery (end of story).

What we want now is the best for general leisure

Having understood the 2 basic types then you need to ask yourself: what do you want from the battery?

Most people want

to charge their batteries as fast as possible in order to reduce their engine hours
to pay as little as possible for the above
to get about 5 – 7 years use as a leisure battery (2 weekends per month and about 4 weeks’ holiday per year).
If you are using your boat for leisure only, then stick to low cost lead acid so called leisure. If you want to turn your boat upside down for 5 seconds then the Lead Acid range with sealed removable caps would be a good choice.

If you want to turn you boat upside down for an hour or two then a Sealed Lead Acid would be worth looking at. However don't expect to charge them as fast.

Having had my so-called opinion published in a UK. boating magazine (boy, do Gel battery suppliers love me. I was taken off their Christmas card list), a Dutch magazine ran with it and the response was very good. The UK magazine did not follow up the article, however the Dutch magazine called ‘Zeilen' did. (The editor is Ruud Kattenberg.) They took the article and not only published it, but ran with it a lot of questions to their readers on their web page. They received over 500 responses and were able to confirm all my findings and published the results. (Not that I need any confirmation as we do this for a living, but it's always nice to have an independent source for folk who doubt you). Is this not what magazines are all about, trying to help the people who buy them and have a bit of a dialogue going?

Conclusion

The best battery to use for fast charging using advanced charging systems

For general leisure use: use low cost Lead Acid which can be topped up with water. So called leisure batteries
For long term cruising then use 6 volt traction
Avoid Gel / AGM for 3 reasons

very expensive
their fast charger rate causes them to gas
poor cycling numbers.