An Idiot's Guide to Deep Cycle Batteries

[bobsadler]

i came across this article which i thought made very interesting - and illuminating - reading.

Sterling Power Products: What is the best battery to use for an auxiliary charging system?

since i have no particular expertise with batteries i'd be interested in hearing from other who do what they think of the author's claims

[btrayfors]

Bob,

I suppose you must do something in Lagos to pass the time. Plumbing the mysteries of storage batteries for marine applications isn't a bad thing, IMHO :-)

On a quick reading, I have the following observations.

1. I agree with the author's basic premise, that flooded lead-acid batteries are the price-point for many cruising sailors.

2. There's a lot of "swimming upstream" comments in his piece. Some are on the mark, while others miss it by far.

3. The author fails to differentiate clearly between the common flooded-battery types: automotive starting batteries, deep cycle batteries, and industrial or traction batteries.

4. The relative prices quoted don't hold up...at least not in the U.S. Example: there's no great difference between gelled and AGM batteries, while flooded batteries are generally -- but not always -- much less expensive.

5. Flooded deep-cycle batteries are of generally two types, differentiated most easily by their price. The 6-volt "golf-cart batteries" ... like the ubiquitous Trojan T-105 .... run about $100-120 each and tend to last for 3-6 years in cruising service. The much more expensive Rolls/Surette deep-cycle batteries last at least twice as long.

6. Traction batteries, AKA Industrial Batteries, generally don't come in sizes and shapes appropriate for smaller cruising sailboats. I suppose the Rolls/Surette line could be considered as "industrial" or "traction" batteries due to their extremely robust construction and long life.

6. If you want fast charging, you definitely do want to choose AGM batteries or some of the new formulations (Odyssy, Oasis, etc.). The author states the opposite.

7. I agree with the sentiments about the cycle performance of AGMs. They don't have a very long cycle life compared to quality flooded batteries, and you really need to treat them very, very well to get their "rated" life (and, especially, keep them fully charged).

No doubt others will have comments on the article.

Bill

[Pete7]

I happen to agree with Charles Sterlings philosophy. What's the point in most weekend and holiday sailors having very expensive batteries if they don't gain the extra battery life or performance?

For us its flooded lead acid, we don't have power or water on the dock so need to charge either via the engine or our honda genny. Since I want to do other things during holidays fast charging is important for us. So FLA and a high 14.8 charge voltage are our goals. AGM and gel are substaintially more expensive in the UK, indeed due to this few chandlers will stock them because yachties just won't buy them. If our batteries last 5 years thats fine by me. Some prices for comparison. Whilst a Gel may only be 50% more than a Trojan once it is multiplied by 3 or 4 house batteries it soon mounts up and huge amount over the leisure batteries the previous owner fitted before selling the boat to us. Perhaps not my first choice but they work well enough at the moment (3 years).

Powermax Leisure 110 amp £84 ($130)
Varta 90amp deep cycle at £134 ($220)
Trojan T105 is £162 ($265)
Trojan 27TMH is £200 ($327)
Lifeline 220amp 4C £290 ($475)
Sonnenschein 110 amp for £290 ($475).

I have been watching a couple of second hand Sterling alternator battery chargers on e bay recently; but they seem to sell for nearly new price so will probably buy one from the local chandler instead. We also have a digital 40 amp battery charger from Sterling which just works and does the business even if it means a monthly top up of the batteries.

Pete

[Pete7]

Originally Posted by btrayfors

3. The author fails to differentiate clearly between the common flooded-battery types: automotive starting batteries, deep cycle batteries, and industrial or traction batteries.

Bill, what do you see is the difference between "deep cycle batteries and industrial or traction batteries"?

Peter

[btrayfors]

Peter,

See my #5 and #6 above.

Lots of batteries are marketed as being "deep-cycle". They're not all the same by any means. There are big differences in: (a) price; (b) construction; (3) availability; and (4) useful life.

Again, for many cruising sailors, the price point is probably flooded, "deep-cycle" batteries like the Trojan T-105.

For those wanting/needed a longer-lived, more robust storage solution, the Rolls/Surette batteries can provide that....at a considerably higher cost.

A variety of "industrial/traction" battery solutions are possible for the sailor with plenty of room and who's willing to experiment a bit.

All of the above are flooded, lead acid batteries.

AGMs, gels, and some of the newer technologies (e.g., Odyssey, Oasis) add yet another whole dimension to the cruising sailor's dilemma, "What battery is best for me?"

Bill

[Pete7]

Originally Posted by btrayfors

Peter, See my #5 and #6 above.

Oops missed that, thanks.

Originally Posted by btrayfors

AGMs, gels, and some of the newer technologies (e.g., Odyssey, Oasis) add yet another whole dimension to the cruising sailor's dilemma, "What battery is best for me?" Bill

Oh absolutely, along with what size battery compartments the builder originally fitted. Yachties can drool all they like but unless you start re-engineering the whole boat your often limited on size and shape.

Pete

[Jim St.Pierre]

wow...VERY GOOD Bob.Thank You. I have read alot on the batteries and always came away confused...This pretty much sums it up. Thanks again....

[stevensc]

A message from Nigeria not promising millions, WOW!
A good discussion though
Steve

[btrayfors]

Steve,

Actually, during my last trip to Lagos I was with a high-level delegation which promised THEM millions (and received terrific treatment, food, and a beautiful traditional shirt from a Nigerian Chief)!

But...that was in a different life, before I took the Water Rat's advice and started full-time "messin' around in boats" :-)

Bill

[CharlieJ]

I have to disagree with most of Mr. Sterlings' pronouncements as they are just plain wrong.

Quoting from the referenced article: "So in my simple mind the AGM is about 3 times more expensive than the standard one. And the Gel, about 5 times more. So the question is; if these batteries are 3 – 5 times more expensive than the standard one, what do they do that is 3 – 5 times better? Do they last 3 – 5 times longer? (I think not, more like the reverse). Do they charge 3 – 5 times faster to reduce your engine running hours? (Only in their dreams.)"

He got the expense part correct; however he completely missed the boat on the ability to accept a higher charge rate. Trojan, the manufacture of the very popular T-105's, used to have a charge rate of 0.25C (C is the amp-hr capacity of the battery; thus a 100 amp-hr battery could accept a charge rate of 25 amps.) If you review their latest recommendations Trojan Battery Company, you will find that they now recommend a charge rate of 0.1 to 0.13C. AGM batteries can be charged with a rate greater than 1.0C; e.g., Figure 7 on Page 14 of the Odyssey Battery Technical Manual Odyssey battery files shows the results of charging their AGM batteries with a charge rate of 3.1C.

"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."

He makes light of the two major advantages of AGM batteries; their low self discharge rate (leading to longer shelf life) and the ability to mount them in other than right side up. (I won't comment on the author's dining location.)

A low self discharge rate is a huge advantage in many marine, and other, applications. And the ability to mount the AGM in any position except upside down makes some installations not only easier, but in many cases, possible. Because of their construction, I am very reluctant to install flooded batteries in a living space as they gas on every proper charge cycle. I do not have this reservation with AGMs as the normal gassing is recombined and is never released outside of the battery during a normal charging cycle.

"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.(Emphasis added.)"

This statement is just plain wrong! As shown above, AGMs can be charged at rates greater than 1.0C; flooded batteries at <0.15C.

"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..."

Every reputable battery manufacturer that I know of publishes all of this information on their websites.

I am not going to continue unraveling this white paper. Suffice it to say that Sterling and their US partner, Professional Mariner, make excellent products for the marine and other industries. I can only assume that this white paper was written many years ago before the advances in AGM battery design and manufacture occurred. Advances in battery chemistry are advancing at an unprecedented rate, spurred on by the hybrid/electric vehicle development cycle.

I just attended a seminar on advanced battery developments at the International Boat Builders' Exposition (IBEX 2009). The seminar presenter stated that the thin plate pure lead (TPPL) battery was the most significant change he has seen in over 20 years in the marine industry.

Flooded batteries certainly have their place...I install many systems with this technology. AGMs are simply one more tool in the electrical designers tool box.

Finally, there are very few absolutes in the marine industry. There are; however, many, many shades of gray.

[Fishman_Tx]

Ok, that being said, what is the opinion on Optima AGM deep cycle (say D31M) vs Gel cells for house batteries with a moderate load? I have little experience with the Optima for this yet except we use them for a building backup generator as start batteries, and they've lasted 3 years before being manditorily replaced, at which time I bought the cores back and have put them on the boat. But boat's on the hard so haven't used them yet. They replaced the standard 1100 (crank)amp truck batteries (flooded) of which at least one would short out every year. Trickle charge was at 13.5vdc. Also, need to replace the charger as the meter has give out..
SC34M as start batts...

[Fishman_Tx]

Isn't the AGM different from the a-typical "gel cell" ? I mean they are both VRLA, but the construction is different (absorbent glass mat vs. gelled lead-acid/lead-calcium). Is there any real difference in performance?

[speciald@ocens.]

Don't waste the money on gel or AGM batteries if you are a weekend sailor. The little bit of maintenance does not justify the price. They will not last any longer than good deep cycle batteries. I just replaced 5 8D Agm batteries after 5 years of heavy use - about 3k installed.

[Fishman_Tx]

This won't be a weekend gig. The boat is under refit for liveaboard and Carribean/GOM cruising.

[CharlieJ]

Fishman-I will obliquely answer your questions and interject some of my own preferences and opinions.

Yes, there is a huge difference between gel batteries and AGMs. I personally feel that gels are too temperamental for marine use but ok for Naval vessels. In the evolutionary process from flooded lead acid (FLA) through gel (VRLA-gel) to AGMs (VRLA-AGM) and finally thin plate pure lead AGMs (TPPL) it is my opinion that the gels with their high cost and temperment were surpassed by the AGM technology. While the original, German built, Sonnenheim gel batteries were spectacular performers in the 90's, the subsequent buy out induced quality problems that they never overcame. I will leave it up to you to research the battery manufactures' websites on the details.

Optima makes excellent starting batteries. Their C20 (20 hr rate) rates are just not high enough for serious consideration as a house bank on any vessel over about 20'.

As I said in my original response; FLA batteries still have their place. Remember that the battery bank is just part of the very major DC supply/storage/usage system and you must use a system view in order to meet your design criteria.

AGMs are expensive. Consider the following design scenarios:

• Do you have a space limitation and the need for a large battery bank? I have TPPL batteries that will provide a nominal 2 x 8D capacity in the footprint of a single 8D.
• Do you have to put the battery bank in the lazarette because of space limitations? AGMs may be the answer because it is difficult to properly water the FLA batteries and keep the battery tops clean.
• Do you have a well ventilated engine room with a flat, 4' x 4' area for a battery bank? 6 VDC FLAs are probably the best answer if you are willing to do the prescribed maintenance on them.
• Do you have a power hungry bow thruster that needs its on battery bank? AGMs are the logical answer because they will be installed in an interior space. Some TPPL AGMs are unique in that they have a chamber built into the top of the battery that will capture any escaping gas should the cell relief valves lift. Aquarium tubing carries the vented gas to where it will do no harm.
• Are you a weekend boater with moderate electrical needs that can be served by a 300 A-hr bank? FLAs are probably your best bet.

What's the best battery? Depends.