UPDATED 11/13/12: Changed the title from 5 Year to Year and added to the thread.
Behind the scenes I have been conducting my own little experiment on "inexpensive" batteries. Five years ago in June I purchased three new "deep cycle / trolling" batteries from Wal*Mart all the batteries were from the same date lot (F7) or June 2007.
They were installed in early June of 2007 and run for our normal seasons as follows:
6-2007 - 11-2007 + all winter on-board in Maine
5-2008 - 11-2008 + all winter on-board in Maine
4-2009 - 11-2009 + all winter on-board in Maine
5-2010 - 10 -2010 + all winter on-board in Maine
4-2011 - 11-2011 + all winter on-board in Maine
4-2012 - 11-2012 +.......
Total engine hours during the last six seasons has been 823.2 (we have engine driven refrigeration which probably added 200 or so hours of use)
The parameter for my observational study were simple. Try to treat the batteries as an average boater may do with the exception of a solar panel.
What does that mean?
On the "bad for the battery" side it meant:
*No equalization, ever, for the full six years (they have still never been equalized). Please note that I am a FIRM believer in periodic equalization charges for WET lead acid batteries!! This however is not what "the average boater" does so I specifically excluded it from my experiment.
*Batteries were "topped up" and left on-board, but 100% disconnected, during the winter and NOT left on a charger. They were topped up perhaps every four to five weeks at best, except for the winter of 2010. During the winter of 2010 they were left without charge for 5 months straight because I wanted to see what self discharge and the resting voltage would be come spring. (note that I placed this under "bad for the battery" because that is what most boaters believe, I do not believe this)
*Used only a simple Guest 6A battery charger for any "off season charging" (mostly for "on the hard" charging of the DC system when working on the boat and using DC loads like lights or stereo)
*Used a "DUMB REGULATED" alternator (14.4V set point and no float) for all charging other than solar. 823.2 hours of "dumb charging" over six seasons....
On the "good for the battery" side it meant:
*Normal watering and checking of electrolyte levels
*Never discharging the bank below 50% state of charge (though I did on a few occasions dip to 30% SOC). Average depth of discharge was 30% or drawn to 70% state of charge. We did this through conservation efforts such as LED lighting and 12V appliances vs. 110V.
*Always charging the batteries back to 100% after each use via solar (we are on a mooring)
*Keeping the terminals clean
*Used sufficiently sized wiring to prevent voltage drop in the alternator and solar charging system
* Monitored performance each year via specific gravity, load tests, capacitance, pulsed load testing as well as Ah capacity testing (last three seasons for Ah capacity).
So how have they done?
They have done VERY, VERY well and still test at better than new on CCA ratings as tested with the ARGUS AA500PWP pulsed load analyzer, a Midtronics EXP-1000HD capacitance tester. The Argus is a $750.00 tool and the Midtronics is nearly $2000.00. Suffice it to say the Midtronics is the industry "gold standard" for battery analyzers. I also use a good old fashioned carbon pile load test (500A carbon pile tester) at 50% of CCA (340A) for 15 seconds.
I also constructed an Ah capacity tester using a Victron BMV-602 battery monitor and a fixed load matched to the 20 hour Ah rating of the battery. This works fairly well and shows the batteries still at over 94% of capacity from new. I would need a fixed digital load control to get more accuracy but they cost thousands of dollars so some 12V bulbs act as my "load". While not 100% accurate it is about as accurate as you're going to get without spending thousands of dollars to test the 20 hour Ah capacity.
Ah Capacity Test:
The Victron BMV monitor has a programmable normally open relay built into it that will make & shut the test off at 10.5 volts, which is how a 20 hour Ah capacity test is done. Rigging this up required an additional "ice cube" double pole single throw relay and a 9V battery to power the coil. It was pretty easy to build and assemble if you're handy.
A 20 hour Ah capacity is figured like this:
100Ah battery, divide by 20 = 5A
or
125 Ah battery, divide by 20 = 6.25A
or
70 Ah battery, divide by 20 = 3.5A
Based on the above calculation you would apply a 5A load to a fully charged 100Ah battery at 77F until it dropped to 10.5V. This is how I run my capacity tests. When the battery hits 10.5V the Victron relay makes and cuts the test off at 10.5V. I had to program the battery monitor to do this at 10.5V and also set the "break" voltage at 12V as it would not climb back up there and re-connect the "load". So battery hits 10.5V, relay makes and disconnects the load via the double pole double throw relay. The Victron relay keeps the load disconnected until the battery voltage climbs back to 12V. Once the load (light bulbs) were disconnected at 10.5V I then read the Ah screen to figure out how many Ah's the battery delivered over the test. Pretty simple though not "pin point" accurate.
It should be noted that a capacity test completely kills the battery and the battery must be charged back to 100% immediately after. This is NOT something you want to do on a regular basis. I do it because I am curious to see the differences between capacitance, CCA and load tests when compared to a "capacity" test. Who knew there were soo many methods for testing batteries??
As of two weeks ago this is what the three June of 2007 125Ah batteries delivered:
Battery #1 = 117.7Ah
Battery #2 = 118.3 Ah
Battery #3 = 117.9 Ah
All these batteries are at roughly 94% of their new rated 20 hour capacity. New batteries often perform above "spec" so they may be lower than "new" but I had not built this particular capacity tester 5 years ago so I was unable to draw an accurate baseline. My guess is that after being broken in I might have seen 130-133 Ah when new. Of course I can't really say and it likely could have been 125Ah just what they are rated for.... ??
The only slight problem is that it is very difficult to hold the amperage at exactly 6.25A so there is some load variation, which could in-theory, throw the Peukert factor off the 20 hour rate ever so slightly. The bottom line is that with a 6.25A load, cut off at 10.5V at 77F, this is a pain because you need a really warm room in your house for a few days, the batteries are still in exemplary shape for what I paid.
This entire bank cost me $209.64 or $69.88 each! If you're doing the math in your head that works out to a cost of 55¢ per Ah. Broken down by year the entire bank has cost just $34.94 a year when amortized over the six years of ownership. If they last seven years that will make them $29.94 per year. Of course I am in Maine so there was a 5% tax too.:cussing:
After doing some very extensive research I discovered that these batteries were actually built by US Battery then sold to Johnson Controls and then sold to Wal*Mart and labeled as a group 29 case size. There's ideally no such thing as a "group 29" battery so it's really a group 31 US Battery, 12v battery. Group 29 is a Wal*Mart / Sam's created designation which has gained acceptance as an industry designation.
The batteries are rated at 125 Ah for the 20 hour rate and are as heavy as any comparable group 31 deep cycle battery (within 1 pound of the Deka's sold by West Marine). US Battery actually builds some excellent quality batteries.
So what do I attribute this "good" performance of what most would call "junk" batteries?
#1 Topping the batteries back up to 100% after each use via solar - Numero uno most important aspect of battery life! Over the years I have found that batteries tend to like the partial/day charging regime, and low current charging, that solar can provide. This slow charge via low current can penetrate deep into the thicker battery plates and provide a true & full "deep charge". Even if we ever decide to keep our boat at a dock they will get charged only via solar and the boat will remain isolated from the dock unless I choose to install an isolation transformer to run some AC loads like our dockside fridge. I simply will not charge them at a dock with a "shore charger". (Not suggesting you do the same this is my personal preference for our home waters, which are cool, and see our battery compartment at under 70F all year). If I did not have solar I would charge "periodically" as opposed to constant, but again my personal preference...
#2 Not leaving them on a "constant" float charge as if I was tied to a dock - I see far to many glitches and failures of shore chargers to bother doing this if I already have solar, which is very stable and reliable. While there are exceptions to every rule I tend to see batteries that are constantly "plugged in" not make it much beyond the 4-5 year mark when using industry analyzers and the 80% rule for CA "capacity".
Despite exceptions to the rule, the "rule" is often not defined, or varies from one boat owner to another. I have one customer who's rule is "If I can't make a call on my VHF I need new batteries" he gets 7 years out of his bank that would have failed any sort of capacity testing at year three of four. He has a pull start out board and a small ferroresonant shore charger so starting heavy loads is not in his particular capacity "rule".
#3 Keeping them topped up with water - This is one of those areas some folks just choose to ignore. It is easy, unless access constrained, and usually takes less than five minutes and under $1.00 of distilled water. I also check the specific gravity with a sight refractometer yearly. Testing for SG can be a PITA but it can tell you when a battery cell or cells is starting to to get out of balance and go bad. It could then be removed or equalized bad returned to service and not cause harm the remaining batteries.
#4 Storing them in a COLD climate - Cold drastically reduces the effects of sulfation and the chemical process slows way down. During the winter of 2010, during this "personal observation", I actually let the batteries sit from November 2 to April 10, on-board in cold Maine, with NO occasional charge as I usually did every four-five weeks or so. In early April the bank still measured 12.61V.. Full on these batteries is 12.73V -12.74V (resting OCV). If it had been 80F this bank would have been dead and likely ruined. Thanks to the cold winter temps here in Maine their life was prolonged, not shortened, despite not being charged for five straight months.
I DO NOT recommend this however! I am sure I had some stratification going on, where the acid sinks to the bottom of the case and the water migrates to the top, which can be bad for the batteries, but these "cheap" batteries, "junky" as some might say, survived the winter of 2010 and are still performing WAY better than I thought they would.
#5 Shallow cycling - Our average depth of discharge is about 30% of capacity but we still do have times where we let it go to 50% or 70% depth of discharge. The vast majority of cycles however never went much below 70% state of charge. Shallow discharges lead to longer bank life and more "cycles". When I ran our calculations we only needed two batteries but I added a third to keep the depth of discharge as shallow as possible.
I do believe cold storage and solar greatly aid the longevity of a battery bank and that "dumb regulators" really don't harm them any, after all how many cars, trucks and buses are there running 14.4V all day long. Also as "sailors" you would need to run the engine for a long time to get to a properly programmed "float charge" voltage. Most sailors don't want to run the engine that much so most smart regulators are in bulk or absorption voltage the majority of the time. If there is one thing you can do to keep them lasting it is not to draw them too deeply and to always charge them to full as often as possible to keep sulfation at bay. Shallow discharges can really help your batteries over the long haul.
These are the three batteries as tested in 2011 for CCA performance. The batteries are slightly off each other at; 801 CCA, 813 CCA and 790 CCA and some if this is simply due to the % accuracy of the meter when you get into an area like a 10 CCA differences. Some is likely due to the fact that these batteries have never been equalized. It should be noted that the factory CCA rating of these batteries is 675 Cold Cranking Amps. They have always performed well above that.
This was a capacitance test performed between one of my batteries and a brand new "off the shelf" battery at Wal*Mart done in 2010. It's hard to tell the difference. This test was set for MCA or Marine Cranking Amps which is based on 32F... They have always performed well above the MCA rating too as many batteries do.
Disclaimer: This is NOT a recommendation to run out and buy cheap Wal*Mart batteries, in fact I would NOT buy the current version of our battery which is NOT THE SAME. This is just an observational report, an (n.3), in the whole scheme of things measuring all aspects of the batteries over their life..
In fact, at this point in time, I would actually advise against buying the current Wal*Mart deep cycle marine batteries as the rating on them is ridiculously incorrect. They are not the same battery I got six years ago and they changed last summer. I don't suspect the new Marine Maax 29 is the quality of the one made by US Battery for Wal*Mart.
The new deep cycle batteries at Wal*Mart are rated at 125Ah with a 1A draw. This is nonsense in terms of an "accepted" Ah capacity rating. By industry Ah capacity testing standards for deep cycle batteries a 125Ah battery should support a 6.25A load for 20 hours before dropping to 10.5V.
I suspect the marketing department, in charge of stickers, really messed this one up. On further investigation I found that it's impossible to get any information from the Wal*Mart or Johnson Controls on these new style Wal*Mart deep cycle batteries. In short "nobody knows nothin"..... Heck it took me two weeks to figure out US Battery had actually manufactured our batteries and they were the only ones who knew the Peukert Exponent number for them. JCI & Wal*Mart had no clue..
If going "off shore" or doing extended cruising I would chose a more premium battery and add a bigger alternator with external voltage regulator. For the 7+/- months of cruising we do, in Northern New England, and we do use the boat a LOT, I sail it at least 5-6 days per week this type of set up can work and is a very inexpensive way to get 12V power on-board.
If you want a reasonably priced good quality battery Wal*Mart's sister company, Sam's Club, has taken on the Deka/East Penn line in many areas. They are sold under the Duracell brand. I have called East Penn and confirmed the only difference between these batteries and the SAME batteries sold at West Marine, for more than double the price, is the "sticker".
See this post for more info: Battery Buyers = Good News (LINK)
EDIT 11/13/2012
Our boat is still in the water but the other day while there I took some "end of season" measurements, on our bank of batteries. They are just completing their 6th season.
This is the bank of three Wal*Mart group 31 batteries purchased/installed in the spring of 2007.
Unfortunately all I had with me was my Midtronics analyzer and not the Argus analyzer which is what I have been using as my baseline. Still, it was a cold morning and the batteries themselves were at 32F. I wanted to see how they tested under these conditions for capacitance as well as voltage dip during starting...
This first photo shows the resting voltage , though not technically "resting" as they were still connected to the system. The batteries had been disconnected from the solar panel for about two weeks. Our system has a 0.1A +/- parasitic load and the open circuit voltage at the end of two weeks was still at 12.69V.. Normal full charge resting voltages for these batteries has been 12.72 - 12.73V
The analyzer also shows the measured cold cranking capacity or "CCA". Each of the three batteries is rated at 675 CCA so all three in parallel should be at 2025CCA. At 32F they put up 2071 CCA which is still 46CCA better than their "as new" rating.
The display also shows the actual battery case temperature. I had left my battery box open so they were not kept as warm as normal, by the bilge temps..
I did not have the time to break them apart and test them individually. That is the best test. I will do a lot more testing including a 20 hour Ah capacity load test when the boat gets home.
Season six went from April 16th 2012 to (still in the water)
Battery Performance:
This next shot shows how the battery bank and system wiring performed under starting conditions. These numbers are the "averages" during starting.
The first line is the average voltage during starting. Anything over 10.5 volts is considered good. The bank has a slight dip to the high 11's but recovered enough to still maintain an average voltage during starting of 12.04V at 32F...
The second line is the average amps during the starting duration. With the engine cold she draws more in-rush and overall current during starting than when she is 70F like during the summer sailing season. The peak in-rush current was about 640A and the average was 286A.
The third line shows the time it took for our motor to start from the first click of the starter until the starter became "unloaded".. The entire duration of time it takes for our 44HP Westerbeke engine to fire is just 746mS / 0.746 seconds or roughly 3/4 of a second to fire....
The last line is the average starting circuit resistance. It shows 15.1mΩ/milliohm or 0.0151Ω / Ohms of resistance in the circuit. This is an excellent number meaning our cables and connections are in very, very good shape and properly sized.
The next photo shows what the starting current looks like graphed out remember this represents 0.75 seconds of time:
The last photo shows how the battery bank supported voltage during the starting event. This is exceptional performance for six year old deep cycle batteries that have been in a deep cycling application. What makes this even more impressive is what temperature the batteries were, 32F....
For a $210.00 bank of Wal*Mart batteries, that have never been equalized, and have been stored on the boat every "harsh winter" winter, and even went one entire winter without being "topped off" at all, I'd say were are getting stellar performance.....
The only changes made to the system this year were upgrading to a 140A alternator & serpentine belt kit, but they are still charged via a "dumb regulator" not a "smart" one. I also changed the solar panel from an 80W to a 140W panel. The Genasun MPPT solar controller is still the same.
More testing to come over the winter.....
Behind the scenes I have been conducting my own little experiment on "inexpensive" batteries. Five years ago in June I purchased three new "deep cycle / trolling" batteries from Wal*Mart all the batteries were from the same date lot (F7) or June 2007.
They were installed in early June of 2007 and run for our normal seasons as follows:
6-2007 - 11-2007 + all winter on-board in Maine
5-2008 - 11-2008 + all winter on-board in Maine
4-2009 - 11-2009 + all winter on-board in Maine
5-2010 - 10 -2010 + all winter on-board in Maine
4-2011 - 11-2011 + all winter on-board in Maine
4-2012 - 11-2012 +.......
Total engine hours during the last six seasons has been 823.2 (we have engine driven refrigeration which probably added 200 or so hours of use)
The parameter for my observational study were simple. Try to treat the batteries as an average boater may do with the exception of a solar panel.
What does that mean?
On the "bad for the battery" side it meant:
*No equalization, ever, for the full six years (they have still never been equalized). Please note that I am a FIRM believer in periodic equalization charges for WET lead acid batteries!! This however is not what "the average boater" does so I specifically excluded it from my experiment.
*Batteries were "topped up" and left on-board, but 100% disconnected, during the winter and NOT left on a charger. They were topped up perhaps every four to five weeks at best, except for the winter of 2010. During the winter of 2010 they were left without charge for 5 months straight because I wanted to see what self discharge and the resting voltage would be come spring. (note that I placed this under "bad for the battery" because that is what most boaters believe, I do not believe this)
*Used only a simple Guest 6A battery charger for any "off season charging" (mostly for "on the hard" charging of the DC system when working on the boat and using DC loads like lights or stereo)
*Used a "DUMB REGULATED" alternator (14.4V set point and no float) for all charging other than solar. 823.2 hours of "dumb charging" over six seasons....
On the "good for the battery" side it meant:
*Normal watering and checking of electrolyte levels
*Never discharging the bank below 50% state of charge (though I did on a few occasions dip to 30% SOC). Average depth of discharge was 30% or drawn to 70% state of charge. We did this through conservation efforts such as LED lighting and 12V appliances vs. 110V.
*Always charging the batteries back to 100% after each use via solar (we are on a mooring)
*Keeping the terminals clean
*Used sufficiently sized wiring to prevent voltage drop in the alternator and solar charging system
* Monitored performance each year via specific gravity, load tests, capacitance, pulsed load testing as well as Ah capacity testing (last three seasons for Ah capacity).
So how have they done?
They have done VERY, VERY well and still test at better than new on CCA ratings as tested with the ARGUS AA500PWP pulsed load analyzer, a Midtronics EXP-1000HD capacitance tester. The Argus is a $750.00 tool and the Midtronics is nearly $2000.00. Suffice it to say the Midtronics is the industry "gold standard" for battery analyzers. I also use a good old fashioned carbon pile load test (500A carbon pile tester) at 50% of CCA (340A) for 15 seconds.
I also constructed an Ah capacity tester using a Victron BMV-602 battery monitor and a fixed load matched to the 20 hour Ah rating of the battery. This works fairly well and shows the batteries still at over 94% of capacity from new. I would need a fixed digital load control to get more accuracy but they cost thousands of dollars so some 12V bulbs act as my "load". While not 100% accurate it is about as accurate as you're going to get without spending thousands of dollars to test the 20 hour Ah capacity.
Ah Capacity Test:
The Victron BMV monitor has a programmable normally open relay built into it that will make & shut the test off at 10.5 volts, which is how a 20 hour Ah capacity test is done. Rigging this up required an additional "ice cube" double pole single throw relay and a 9V battery to power the coil. It was pretty easy to build and assemble if you're handy.
A 20 hour Ah capacity is figured like this:
100Ah battery, divide by 20 = 5A
or
125 Ah battery, divide by 20 = 6.25A
or
70 Ah battery, divide by 20 = 3.5A
Based on the above calculation you would apply a 5A load to a fully charged 100Ah battery at 77F until it dropped to 10.5V. This is how I run my capacity tests. When the battery hits 10.5V the Victron relay makes and cuts the test off at 10.5V. I had to program the battery monitor to do this at 10.5V and also set the "break" voltage at 12V as it would not climb back up there and re-connect the "load". So battery hits 10.5V, relay makes and disconnects the load via the double pole double throw relay. The Victron relay keeps the load disconnected until the battery voltage climbs back to 12V. Once the load (light bulbs) were disconnected at 10.5V I then read the Ah screen to figure out how many Ah's the battery delivered over the test. Pretty simple though not "pin point" accurate.
It should be noted that a capacity test completely kills the battery and the battery must be charged back to 100% immediately after. This is NOT something you want to do on a regular basis. I do it because I am curious to see the differences between capacitance, CCA and load tests when compared to a "capacity" test. Who knew there were soo many methods for testing batteries??
As of two weeks ago this is what the three June of 2007 125Ah batteries delivered:
Battery #1 = 117.7Ah
Battery #2 = 118.3 Ah
Battery #3 = 117.9 Ah
All these batteries are at roughly 94% of their new rated 20 hour capacity. New batteries often perform above "spec" so they may be lower than "new" but I had not built this particular capacity tester 5 years ago so I was unable to draw an accurate baseline. My guess is that after being broken in I might have seen 130-133 Ah when new. Of course I can't really say and it likely could have been 125Ah just what they are rated for.... ??
The only slight problem is that it is very difficult to hold the amperage at exactly 6.25A so there is some load variation, which could in-theory, throw the Peukert factor off the 20 hour rate ever so slightly. The bottom line is that with a 6.25A load, cut off at 10.5V at 77F, this is a pain because you need a really warm room in your house for a few days, the batteries are still in exemplary shape for what I paid.
This entire bank cost me $209.64 or $69.88 each! If you're doing the math in your head that works out to a cost of 55¢ per Ah. Broken down by year the entire bank has cost just $34.94 a year when amortized over the six years of ownership. If they last seven years that will make them $29.94 per year. Of course I am in Maine so there was a 5% tax too.:cussing:
After doing some very extensive research I discovered that these batteries were actually built by US Battery then sold to Johnson Controls and then sold to Wal*Mart and labeled as a group 29 case size. There's ideally no such thing as a "group 29" battery so it's really a group 31 US Battery, 12v battery. Group 29 is a Wal*Mart / Sam's created designation which has gained acceptance as an industry designation.
The batteries are rated at 125 Ah for the 20 hour rate and are as heavy as any comparable group 31 deep cycle battery (within 1 pound of the Deka's sold by West Marine). US Battery actually builds some excellent quality batteries.
So what do I attribute this "good" performance of what most would call "junk" batteries?
#1 Topping the batteries back up to 100% after each use via solar - Numero uno most important aspect of battery life! Over the years I have found that batteries tend to like the partial/day charging regime, and low current charging, that solar can provide. This slow charge via low current can penetrate deep into the thicker battery plates and provide a true & full "deep charge". Even if we ever decide to keep our boat at a dock they will get charged only via solar and the boat will remain isolated from the dock unless I choose to install an isolation transformer to run some AC loads like our dockside fridge. I simply will not charge them at a dock with a "shore charger". (Not suggesting you do the same this is my personal preference for our home waters, which are cool, and see our battery compartment at under 70F all year). If I did not have solar I would charge "periodically" as opposed to constant, but again my personal preference...
#2 Not leaving them on a "constant" float charge as if I was tied to a dock - I see far to many glitches and failures of shore chargers to bother doing this if I already have solar, which is very stable and reliable. While there are exceptions to every rule I tend to see batteries that are constantly "plugged in" not make it much beyond the 4-5 year mark when using industry analyzers and the 80% rule for CA "capacity".
Despite exceptions to the rule, the "rule" is often not defined, or varies from one boat owner to another. I have one customer who's rule is "If I can't make a call on my VHF I need new batteries" he gets 7 years out of his bank that would have failed any sort of capacity testing at year three of four. He has a pull start out board and a small ferroresonant shore charger so starting heavy loads is not in his particular capacity "rule".
#3 Keeping them topped up with water - This is one of those areas some folks just choose to ignore. It is easy, unless access constrained, and usually takes less than five minutes and under $1.00 of distilled water. I also check the specific gravity with a sight refractometer yearly. Testing for SG can be a PITA but it can tell you when a battery cell or cells is starting to to get out of balance and go bad. It could then be removed or equalized bad returned to service and not cause harm the remaining batteries.
#4 Storing them in a COLD climate - Cold drastically reduces the effects of sulfation and the chemical process slows way down. During the winter of 2010, during this "personal observation", I actually let the batteries sit from November 2 to April 10, on-board in cold Maine, with NO occasional charge as I usually did every four-five weeks or so. In early April the bank still measured 12.61V.. Full on these batteries is 12.73V -12.74V (resting OCV). If it had been 80F this bank would have been dead and likely ruined. Thanks to the cold winter temps here in Maine their life was prolonged, not shortened, despite not being charged for five straight months.
I DO NOT recommend this however! I am sure I had some stratification going on, where the acid sinks to the bottom of the case and the water migrates to the top, which can be bad for the batteries, but these "cheap" batteries, "junky" as some might say, survived the winter of 2010 and are still performing WAY better than I thought they would.
#5 Shallow cycling - Our average depth of discharge is about 30% of capacity but we still do have times where we let it go to 50% or 70% depth of discharge. The vast majority of cycles however never went much below 70% state of charge. Shallow discharges lead to longer bank life and more "cycles". When I ran our calculations we only needed two batteries but I added a third to keep the depth of discharge as shallow as possible.
I do believe cold storage and solar greatly aid the longevity of a battery bank and that "dumb regulators" really don't harm them any, after all how many cars, trucks and buses are there running 14.4V all day long. Also as "sailors" you would need to run the engine for a long time to get to a properly programmed "float charge" voltage. Most sailors don't want to run the engine that much so most smart regulators are in bulk or absorption voltage the majority of the time. If there is one thing you can do to keep them lasting it is not to draw them too deeply and to always charge them to full as often as possible to keep sulfation at bay. Shallow discharges can really help your batteries over the long haul.
These are the three batteries as tested in 2011 for CCA performance. The batteries are slightly off each other at; 801 CCA, 813 CCA and 790 CCA and some if this is simply due to the % accuracy of the meter when you get into an area like a 10 CCA differences. Some is likely due to the fact that these batteries have never been equalized. It should be noted that the factory CCA rating of these batteries is 675 Cold Cranking Amps. They have always performed well above that.
This was a capacitance test performed between one of my batteries and a brand new "off the shelf" battery at Wal*Mart done in 2010. It's hard to tell the difference. This test was set for MCA or Marine Cranking Amps which is based on 32F... They have always performed well above the MCA rating too as many batteries do.
Disclaimer: This is NOT a recommendation to run out and buy cheap Wal*Mart batteries, in fact I would NOT buy the current version of our battery which is NOT THE SAME. This is just an observational report, an (n.3), in the whole scheme of things measuring all aspects of the batteries over their life..
In fact, at this point in time, I would actually advise against buying the current Wal*Mart deep cycle marine batteries as the rating on them is ridiculously incorrect. They are not the same battery I got six years ago and they changed last summer. I don't suspect the new Marine Maax 29 is the quality of the one made by US Battery for Wal*Mart.
The new deep cycle batteries at Wal*Mart are rated at 125Ah with a 1A draw.
This is nonsense in terms of an "accepted" Ah capacity rating. By industry Ah capacity testing standards for deep cycle batteries a 125Ah battery should support a 6.25A load for 20 hours before dropping to 10.5V. I suspect the marketing department, in charge of stickers, really messed this one up. On further investigation I found that it's impossible to get any information from the Wal*Mart or Johnson Controls on these new style Wal*Mart deep cycle batteries.
In short "nobody knows nothin"..... Heck it took me two weeks to figure out US Battery had actually manufactured our batteries and they were the only ones who knew the Peukert Exponent number for them. JCI & Wal*Mart had no clue..If going "off shore" or doing extended cruising I would chose a more premium battery and add a bigger alternator with external voltage regulator. For the 7+/- months of cruising we do, in Northern New England, and we do use the boat a LOT, I sail it at least 5-6 days per week this type of set up can work and is a very inexpensive way to get 12V power on-board.
If you want a reasonably priced good quality battery Wal*Mart's sister company, Sam's Club, has taken on the Deka/East Penn line in many areas. They are sold under the Duracell brand. I have called East Penn and confirmed the only difference between these batteries and the SAME batteries sold at West Marine, for more than double the price, is the "sticker".
See this post for more info: Battery Buyers = Good News (LINK)
EDIT 11/13/2012
Our boat is still in the water but the other day while there I took some "end of season" measurements, on our bank of batteries. They are just completing their 6th season.
This is the bank of three Wal*Mart group 31 batteries purchased/installed in the spring of 2007.
Unfortunately all I had with me was my Midtronics analyzer and not the Argus analyzer which is what I have been using as my baseline. Still, it was a cold morning and the batteries themselves were at 32F. I wanted to see how they tested under these conditions for capacitance as well as voltage dip during starting...
This first photo shows the resting voltage , though not technically "resting" as they were still connected to the system. The batteries had been disconnected from the solar panel for about two weeks. Our system has a 0.1A +/- parasitic load and the open circuit voltage at the end of two weeks was still at 12.69V.. Normal full charge resting voltages for these batteries has been 12.72 - 12.73V
The analyzer also shows the measured cold cranking capacity or "CCA". Each of the three batteries is rated at 675 CCA so all three in parallel should be at 2025CCA. At 32F they put up 2071 CCA which is still 46CCA better than their "as new" rating.
The display also shows the actual battery case temperature. I had left my battery box open so they were not kept as warm as normal, by the bilge temps..
I did not have the time to break them apart and test them individually. That is the best test. I will do a lot more testing including a 20 hour Ah capacity load test when the boat gets home.
Season six went from April 16th 2012 to (still in the water)
Battery Performance:
This next shot shows how the battery bank and system wiring performed under starting conditions. These numbers are the "averages" during starting.
The first line is the average voltage during starting. Anything over 10.5 volts is considered good. The bank has a slight dip to the high 11's but recovered enough to still maintain an average voltage during starting of 12.04V at 32F...
The second line is the average amps during the starting duration. With the engine cold she draws more in-rush and overall current during starting than when she is 70F like during the summer sailing season. The peak in-rush current was about 640A and the average was 286A.
The third line shows the time it took for our motor to start from the first click of the starter until the starter became "unloaded".. The entire duration of time it takes for our 44HP Westerbeke engine to fire is just 746mS / 0.746 seconds or roughly 3/4 of a second to fire....
The last line is the average starting circuit resistance. It shows 15.1mΩ/milliohm or 0.0151Ω / Ohms of resistance in the circuit. This is an excellent number meaning our cables and connections are in very, very good shape and properly sized.
The next photo shows what the starting current looks like graphed out remember this represents 0.75 seconds of time:
The last photo shows how the battery bank supported voltage during the starting event. This is exceptional performance for six year old deep cycle batteries that have been in a deep cycling application. What makes this even more impressive is what temperature the batteries were, 32F....
For a $210.00 bank of Wal*Mart batteries, that have never been equalized, and have been stored on the boat every "harsh winter" winter, and even went one entire winter without being "topped off" at all, I'd say were are getting stellar performance.....
The only changes made to the system this year were upgrading to a 140A alternator & serpentine belt kit, but they are still charged via a "dumb regulator" not a "smart" one. I also changed the solar panel from an 80W to a 140W panel. The Genasun MPPT solar controller is still the same.
More testing to come over the winter.....
