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How to murder batteries in half a year

Maine Sail

Moderator
Feb 6, 1998
11,037
Canadian Sailcraft 36T Casco Bay, ME
The Boat:
She is a 2007 36 footer, and was purchased by her current owner in June of 2015 in Nova Scotia, and then sailed back to Maine. At commissioning in Nova Scotia the batteries were found to be "dead". The broker ordered and had installed two brand new Costco/Kirkland "Deep Cycle" Group 27 batteries rated at 115Ah each..

One of the murdered batteries during autopsy.
NOTE: Beware this identical battery may also be wearing an Interstate branded sticker at some Costco stores.


EDIT: As shown above I recently cut open one of these batteries and found they were not at all deep cycle but rather a very thin plate dual purpose bordering on starting batteries that had a "deep cycle" sticker applied to them. Buyer beware!

I was supposed to be on the delivery trip but could not make it due to a last minute schedule change having to do with the boat not actually being ready. I walked the owner through all the things that should be checked and that could go wrong and I loaned him numerous tools for the trip. They set off across the gulf of Maine in little to no wind but they did have brand new batteries.

Deep Cycle Stickers on El-Cheapo Batteries = RIP OFF

When buying batteries please try & stick with a brand name, unless you know EXACTLY what the product really is under the re-labelers sticker. Trojan, Deka/East Penn, US Battery, Dyno, Crown, Lifeline, Full River, Firefly, Odyssey, Northstar etc. are all reputable deep-cycling BRAND NAMES.

Sticker brands such as Kirkland, Power Star, All Rounder, Energy Master, Auto Craft, Powertron, Super Start, Maxx Marine, Cabella's, Duralast, Sportsman etc. etc. are all STICKER-BRANDS and you have little to no idea what you are really getting unless you do some extensive leg work.

I can say without a doubt, because I physically cut them open & measured the plate thickness, these batteries were not "deep cycle" and probably not even a true "dual purpose" battery, they were low budget automotive grade batteries wearing a "Deep-Cycle" sticker.

When companies slap a sticker on a battery mistakes get made and misleading marketing can rear its ugly head. Rather than go into what to look for in a deep cycle battery here, click below for more info:

What is a Deep Cycle Battery? (LINK)

Heat Murders Batteries:
When the boat got to Casco Bay I immediately went to work on her. The factory layout was horrible with both of the "new" batteries in the engine compartment. Heat murders batteries, and while this does not happen instantly heat and low SOC are not good for longevity. These batteries had already likely exceeded 125F on a few occasions. I actually measured the case temp of one of them at 117F when they came into the anchorage after a multi-hour motor in no wind. They also had to motor for approx 13 hours of the delivery trip due to zero wind. It was clear the upgrades would start with getting the batteries out of the engine space.

Seeing as budget was short but cruising plans were on the calendar, I set out to relocate the two new batteries & get them out of the engine bay. I also planned to wire the two new batteries as a hard-wired parallel house bank. I had a used but otherwise good condition group 31 battery that I gave to the owner as a "starting battery" and we left it in the engine bay for this season. In the image below there had been two group 27's and now there is just one group 31 acting as a starting battery. Still, this is a a very poor location for batteries.


Partial State of Charge (PSOC) Cyclic Use Murders Batteries:
The alternator can also be seen in the image below, as well as a number of safety flubs that needed correction, and is a bone stock Paris-Rhone automotive alternator. A shortcoming of this alternator is that it temp-compensates and reduces the absorption charging voltage as the alternator heats up. This type of temp protection for the alternator, is not at all healthy for deeply cycled batteries.

Because of the way this alternator self protects itself it leads to chronic under charging and an absorption voltage that is far to low and incredibly unhealthily for the batteries. On the list for this boat, to correct this short coming, is external regulation.

Because of the short engine run times on sail boats, and the insanely low voltages we were measuring at the batteries, these batteries were suffering from pretty harsh PSOC use.

PSOC cycling use means that we never fully recharge the bank before discharging the bank again. When we PSOC cycle lead acid batteries they suffer two things. The first is a phenomenon called "capacity walk down" which begins as early as cycle #1. The walking down in capacity is caused by the number two item, which is sulfation. Essentiaally PSOC walk-down and sulfation means or necessitates that each day you actually need to run your engine a bit longer and longer to achieve the same usable capacity. So if you charged for 1 hour per day, at a steady 40A, and assumed you were getting 40Ah back in think again. The usable capacity will continue to walk down a bit with each PSOC cycle. The only way to slow the effects of PSOC cyclic use is with frequent full charges and equalizing the batteries regularly. For more info on PSOC cyclic use, and its effects, see the May 2015 article in Practical Sailor -
Fighting Sulfation In AGM's



Incorrect and Inaccurate Voltage Readings Can Murder Batteries:
The boats analog DC volt meter was horribly inaccurate and was not working correctly. The owner checked battery voltage using the volt meter but had no idea it that was inaccurate. On battery #1 the analog volt meter was reading +0.9V off , on the high side, and for bank #2 +0.8V high. This does the batteries no favors because at 12.1V the batteries were respectively at 11.2V and 11.3V which is essentially DEAD. Discharging the batteries to this level will rather drastically shorten their usable cycle life, especially starting type batteries masquerading as "deep cycle"...



Let's Just Try and Get You Through The Season:
The two new Costco batteries were moved to a cooler location below the starboard quarter-berth, where they should have been all along, the builder even had a shelf for them already built into the hull liner.. Unfortunately the platform molded into the hull liner prohibits flooded batteries being mounted in the proper orientation so the owners next bank will be AGM.. The Costco batteries were charged and equalized briefly during this conversion. The battery cabling was all well sized by the builder, at 2/0, so new jumpers were made of 2/0. The batteries were secured and wired in parallel for a house bank. At the same time an ACR was added to charge the starting battery. Some other wiring changes were also made to make it easier for the owner to operate.


Better SOC Monitoring:
The owner was not up to installing solar this year and the boat resides on a mooring, not having solar on a mooring is a terrible situation for batteries on a sailboat..

I explained to him that I was doubtful his Costco batteries would make it into season two, but he suggested season two would have more budget for things such as solar & newer and higher quality deep cycle batteries. The choice was made to install a Smartgauge this year so he could better track SOC and help try to keep his bank healthy enough to get through the season. The Smartgauge was already part of his long term plan so installing it for this season, considering the inaccuracy of the on-board volt meter, seemed like the best fit.

Time to Decommission:

When I went to decommission the boat the owner had been running the water pump to drain the tanks. We stopped and let the Smartgauge sit for about 1 hour and it stabilized at 38% but with the LED lights on, and the stereo, the SOC kept dropping until I disconnected the bank at 34%. The owner was lamenting that the SOC had been dropping more rapidly as the summer grew on but that he had "learned" how long he could run loads, not very long..

In total he and his family did approx 25 over-nights that resulted in deep-cycling the batteries to approx 50% SOC. There were also a fair number of very deep discharges, perhaps 8-10, before the Smartgauge was installed. There were also 5-6 days of racing with the fridge running and in these scenarios they usually sailed on and off the mooring with no charging.

After the Smartgauge was installed the owner tried very hard not to let it drop below 50% SOC but as the batteries grew tired, keeping them above 50% SOC became a losing proposition. Even with a ten hour motor one weekend, from Portland, ME to Isle Au Huat, ME, with zero wind, the batteries still never reached 100% SOC, due to sulfation.


The SOC in the fall when the batteries were removed:



Testing The Bank:

This scenario created a good opportunity for me to not only test the accuracy of the Smartgauge but to also test the batteries for their current state of health.

I photographed the Smartgauge at 34% SOC then removed the batteries and took them back to the shop for testing. The batteries were wired in parallel, just as they were on the vessel, and connected to one of the Ah capacity testers. Look close and you can clearly see the 5/15 date code stickers on the batteries. Brand new as of May 2015...



I did not recharge the batteries before discharging them to the industry standard of 10.5V under their rated 20 hour load. The batteries delivered a paltry 20.22Ah's before hitting 10.5V!! This is a 230Ah rated bank so at 34% SOC it should have delivered somewhere in the neighborhood of 78Ah +/- before hitting 10.5V. I knew the batteries were in bad shape when they could barely muster 20Ah's from a reported 34% SOC..


I then fully charged the batteries and floated them for two full days beyond the absorption charging and ran a full capacity test at the 20 hour "as new" rate. The battery case temps hit a low of 74F and a high of 78F, well within reasonable for this testing. This time they delivered a measly 52.94Ah. You read that correctly, they were delivering just 23% of their factory rated capacity in just 4.5 months. A dead battery, by industry standards, is anything less than 80% of its as new factory Ah rating!! 23% is really quite murdered...


The good news is that 52.94Ah, in total capacity, compared against 20.22Ah, from the 34% Smartgauge measurement point, we were within 4% accuracy of the batteries actual physical capacity. This 4%, for a battery that has been pretty murdered, is an exceptional feat for the Smartgauge. I know of no other battery monitor in existence that could have predicted this massive decline off the abyss as accurately as the Smartgauge did.

If this had been a traditional Ah counter the bank capacity would still have been programmed for 230Ah's with an actual capacity of just 53Ah's... Think about that for a moment...

Never satisfied with "good enough" I decided to do a full equalization of 8 hours at 15.5V. The batteries were charged until current declined to well under 1A at 14.6V then the voltage was brought up to 15.5V and held there for 8 hours. I then re-tested the batteries for capacity at the 20 hour as new rate. This time they delivered 56.41Ah, an improvement of 3.47Ah. I repeated the test a second time with an additional 2 hours of equalization and netted within .4Ah. This was the most we were ever going to see out of these murdered batteries.

I also split the batteries and ran individual capacity tests. I wanted to see if one battery was the culprit or was it both of them more equally? Battery #1 tested at 28.04Ah and battery #2 tested at 28.32Ah. Both batteries were within 0.28Ah of each other, so they died pretty evenly, but they still died a pretty quick death.

This test ensured we did not have one really bad battery and one marginally good one propping the other up.

The good news? The equalization process brought the Smartgauges 34% SOC reading, and accuracy, down into the 2% range, in the real world and in an abusive environment. This is really quite remarkable.



Specific Gravity is not a good tool to determine State of Health or Ah Capacity:

To many I know this will sound like blasphemy, but save your clothes from acid burns...... How on Earth can I say that? Well for starters each of the 12 cells measured as near identical as you can get. The batteries were not out of balance in any abnormal manner. They also hit a specific gravity of 1.280 when fully charged. Yes they were "fully charged" but instead of 230Ah's they could only deliver 53-56 Ah's. Specific Gravity can tell you SOC, like the Smartgauge, but not SOH / state of health. A good specific gravity reading tells you nothing about the batteries actual capacity just its SOC, which the Smartgauge can do externally with no acid burns..

Here we have a bank delivering at best 24.5% of its advertised capacity (230Ah rated delivering 56.41Ah after EQ) in somewhere around 35-40 cycles most likely due to sulfation, being the wrong battery type for the application, a dumb alternator regulator, never getting fully recharged after each use and possibly some effects from heat.. Yes these batteries also had a few super deep cycles but any deep cycle battery should handle the occasional dip to 20% SOC with ease, if otherwise properly charged and properly selected for deep cycle use..

Lessons Learned:

*All lead acid batteries need to get back to 100% SOC as often as possible. A stock alternator on a mooring sailed boat is simply inadequate for optimal cycle life. For mooring sailed boats and battery longevity a small solar array can do wonders.

*Cheap Group 24, 27 & 31 flooded batteries are not deep-cycle just because the sticker says so. I have a good hunch these are actually starting batteries not even dual purpose, but they wear a "deep cycle" sticker.

*Due to the liner pan and clearance, the batteries were mounted in an improper orientation for the cells/plates on a sail boat. The vessel design precludes proper orientation of a sufficiently sized flooded house bank without doing some serious $$$ modification.

*The label on these batteries is likely a complete and utter hip shoot. I find it hard to believe that these batteries could have ever delivered 115Ah even when just barely broken in. They faded so fast in Ah capacity that I've only seen this once before, and they were starting batteries that had been mislabeled by a regional distributor.

*These batteries weigh considerably less than a Trojan group 27 so they are likely closer to a starting battery than a dual purpose.

*Unless you are getting 14.4V(bare min for flooded batteries), at the battery end of the charging circuit, but preferably 14.6V to 14.8V, you will wind up chronically under charging and will kill your batteries earlier due to sulfation. The absorption stage of charging is the healthy part where the lead sulfate is reconverted. If you never attain an absorption voltage, due to voltage drop and an unsuitable alternator design for a cycling bank, then the batteries will die sooner than later. In this case murdered in one short 4 month season.

*Sulfation murders batteries quickly, if you allow it to. Batteries need to get back to 100% SOC as soon after a discharge as possible. This simply does not happen on most sailboats with alternator only charging.

*Heat kills batteries. While the effects of heat are not instantly murdering batteries lead sulfate hardens and becomes un-reconvertable faster in warmer temps than it does when batteries are kept cooler. Deep cycling and heat do not play well together.

*If you are on a mooring solar or wind charging is going to be pretty critical.

*If you want to know your SOC the Smartgauge actually works and is very simple for the average boater to understand.

*Inaccurate voltage readings can actually lead to a worsening of the battery condition. Analog volt meters can be horribly inaccurate in the marine environment so please compare these readings to a meter with known good accuracy.

*Specific gravity readings tell you nothing about state of health or Ah capacity only SOC. The specific gravity readings on these batteries showed them in good balance and showed them attaining a full charge yet that full charge lacked any real stored capacity...

On The Horizon For This Vessel:

-External regulation
-Alternator & volt sensing direct feed to house bank
-New batteries - most likely Firefly Carbon Foam AGM
-Solar
-More wiring modifications
-Moving the start battery out of the engine bay

EDIT: We finally cut these batteries open and discovered they were essentially starting batteries with a deep cycle sticker. The plates were no thicker than a standard starting battery. Please be careful buying your batteries and do try to treat them better than our customer did.
 
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Sep 6, 2010
1,298
Jeanneau 349 port washington, ny
I love my smart gauge. Glad to know it's accurate! Thanks to MS for recommending some time ago.
 
Jan 22, 2008
1,465
Hunter 34 Alameda CA
Thanks Mainsail. This was very enlightening. I am really glad I installed my Smart Gauge as well last year. Between that and following your advice on large gauge wire between the alternator and the house bank I have immensely improved my charging during motoring even with the puny 35 amp Hitachi alternator. More improvements to follow.
 
Aug 13, 2012
514
Catalina 270 Ottawa
A great article!

I have a question, though. The SmartGauge was installed to monitor the SoC. The cost is around $350. Wouldn't a solar panel and a charge controller be a better investment?

You can get a rollable solar panel (20 W) and a charge controller (with some battery monitoring) for a similar price (a bit more, probably closer to $400). This would not require any difficult installation (you can put the panel over the bimini, dodger or lay it down on the cabin top) and the charge controller could be selected so that it would work with whatever solar charging was planned for the next year.

Such set-up would not provide enough charging for the long term, but it would help bringing the batteries closer to the full charge. The solar panel would have to be replaced once the proper solar charging is installed, but the controller could easily be reused.

I am getting about 0.75 - 1 A from a 21 W panel. But most of our sailboats are idle for most of the time. This particular one was used around 25 times in about 100 days (this means that for the remaining 75 days it was sitting idle and could have had its batteries charged at about 5-10 Ah per day.

Would this save these batteries? If they were dead (or almost) after the first trip (delivery), then certainly not. But if they were reasonably OK after that cooking, this could have prolonged their lives.

does this make sense?
 

Maine Sail

Moderator
Feb 6, 1998
11,037
Canadian Sailcraft 36T Casco Bay, ME
A great article!

I have a question, though. The SmartGauge was installed to monitor the SoC. The cost is around $350. Wouldn't a solar panel and a charge controller be a better investment?
Smart Gauge is $299.00 and he already had an inoperable voltmeter and the Smart Gauge was part of the long term plan.


You can get a rollable solar panel (20 W) and a charge controller (with some battery monitoring) for a similar price (a bit more, probably closer to $400).
The owner did not want to waste money on a temporary solution that would just need to be upgraded in the future.


This would not require any difficult installation (you can put the panel over the bimini, dodger or lay it down on the cabin top) and the charge controller could be selected so that it would work with whatever solar charging was planned for the next year.
That's just the problem. This is a difficult installation because the boat is primarily a race boat that is also cruised. It has neither a bimini nor a dodger. The solution I am working on will be a fully custom back stay mount for a 60+ watt panel. It will certainly help with mooring recharge but is still a bit on the sub-optimal side. This is why sulfation resistant Carbon Foam AGM's will be installed as well as an upgraded alternator. As it is now his existing alternator can barely get them back above 65-70% SOC in a reasonable time frame.

Such set-up would not provide enough charging for the long term, but it would help bringing the batteries closer to the full charge. The solar panel would have to be replaced once the proper solar charging is installed, but the controller could easily be reused.
Any solar could have helped but the owner under stood the batteries were essentially disposable and he was not concerned with trying to lengthen their life beyond getting through this year.. The Smart Gauge represented zero wasted money because it will work well with all the planned future upgrades.

I am getting about 0.75 - 1 A from a 21 W panel. But most of our sailboats are idle for most of the time. This particular one was used around 25 times in about 100 days (this means that for the remaining 75 days it was sitting idle and could have had its batteries charged at about 5-10 Ah per day.
The 25 times number was "overnights that required a deep discharge". The boat was used much more than that and was also raced 1-2 days per week as well as cruised almost every weekend. Total deep cycling events were probably in the 30-35 range including the delivery, and shallow cycling was another 20 perhaps. The biggest issue was the alt not able to get the banks much above 65-70% SOC in the short duration runs due to voltage drop and internal temp compensation of the factory system. A 20W panel could have helped but not done much on a 230Ah bank (if it ever was) at 65% SOC between Sunday night and Wednesday.

Would this save these batteries? If they were dead (or almost) after the first trip (delivery), then certainly not. But if they were reasonably OK after that cooking, this could have prolonged their lives.

does this make sense?
Solar will always help but this owner decided to plunk his money on knowing his SOC this season so as not to get caught dead. He and his wife use and like their DC refrigeration. Next season will be solar, alternator and new batteries but it will not be inexpensive due to the full custom fabrication of a back stay mount for a 60+ watt panel. This is really the only option that will work for him and his use of the boat as a racer first then cruiser......
 
Sep 2, 2011
1,041
Hunter 27 Cherubini Alum Creek State Park
image.jpg image.jpg The marina I'm in is owned by our state park system, and electrical service is not allow at the docks.
So, I installed a 140w solar panel w/ MPPT controller, and 4 6v golf car batteries. I sacrificed most of the port rear quarter berth for the 2 HD battery boxes.

I didn't hook up the alternator to the system, as I installed an ACR to let the solar system charge the starting battery, as well. The motor is basically only used to get in and out of the marina. Occasionally, I'll run the 2 miles up and down the lake to exercise the engine. I typically sail 3-4 days a week, no overnights, and rarely use the reefer or cabin lights. May or may not be typical of other sailors.

When I arrive at the boat, the controller is always showing the batteries are on float at 13.5v when I get to the point that I'm cruising on this boat, I'll add 1 more 140w panel. I'm on the hard now for the winter, and wonder if I need to occasionally discharge down to 50% SOC to keep them in good condition?
 

Maine Sail

Moderator
Feb 6, 1998
11,037
Canadian Sailcraft 36T Casco Bay, ME
Heat "murders" batteries.. but I think its more similar to how a wife murders her husband by feeding him a steady diet of bacon and hot dogs.
You are 100% correct heat it is not a sudden death but leaving any deep cycle battery in a hot engine bay is simply a really dumb idea.. With hot batteries the chemical reactions happen faster and a battery left at anything but 100% SOC will have the sulfate harden and "clump" and become non-reconvertable, at a significantly faster rate. Permanent sulfation damage happens MUCH faster in hot batteries than it does in cool batteries.

My hot battery story.. My boat lives in Lake Havasu Arizona and this is one of the hottest places on the planet in the summer. I have been here in June when it got up to 124F!!! I was here this June for a week and had several days that got up to 117F.
A truly HORRIBLE location for any battery.

My old Mac 26S lives here full time and sits all summer with two golf cart batteries trickle charged up by a 10 watt solar panel/ PWM controller (which has a simple temperature compensated charging algorithm - the temp sensor is in the controller so not exactly accurate).
The key here is that your charger reduces charge voltage based on ambient temp if it did not they would really get stomped on. Sure it would be better if it did this based on battery temp, not ambient temp, but at 117F we are splitting hairs and walking up hill on ice either way.

The golf cart batteries I just replaced lasted five, maybe six years and four of those were full time in Lake Havasu.
The problem with this is always the definition of "lasted". For most boat owners they would continue using the batteries in this article into next year, incorrectly assuming they are still good because they "charge" and "hold and charge" and can show a "healthy SG" reading. Assuming they are good, based on the usual suspects, would be incorrect, as has been shown.....

For example those batteries have been off charge now for three days and are still at 12.985V as of about 3 minutes ago, yet they are only capable of delivering 24.5% of their stated capacity under a controlled industry standard 20 hour Ah capacity test. They are dead and no splitting of hairs changes that but you could still try and define them as "lasted".......

"Lasted 5-6 years" & industry standardized capacity testing are two entirely different things and we are essentially talking apples to garbanzo beans. One method shoots from the hip, with no reliable or quantifiable measures, and the other uses the testing the battery industry sets forth as the only accurate measure of Ah capacity as related to state of health.

I would surmise (hip shoot ;)based on experience testing many, many hundreds of batteries for true capacity), at those temps, and by year two, your GC-2's would not have passed a 20 hour test. Would they still work and "last"? Sure, to most boaters they would certainly assume they are safe to use and might even think they are in good health. For very light loading they can certainly be used for discharging when below their 80% of as new capacity defined as dead, failure point. The problem is that once we dip below 80% of the as new rating the risk of catastrophic failure goes up rather dramatically.


The locals say that car batteries here last maybe 3 or 4 years. I think the heat we have here (day after day during the summer) is considerably worse than what the boat in the original post saw. What I gather is that you get at least half - maybe 3/4 of normal battery life (for lead acid) - if you maintain the water. .
For every 15F rise in temperature above 77F battery life is cut in half. (Source Battery Council International)

"Rolls Battery - Hot Operating Temperatures
In hot ambient operating temperatures, cells temperatures exceeding 110ºF (43ºC) should be avoided. A battery on charge will experience approximately a 20ºF (10ºC) rise in cell temperature in an ambient range of 95ºF (35ºC). Charging should be more closely monitored in temperatures >95ºF. Charging currents should be reduced or charging should be stopped until the battery is allowed to cool, if 110ºF (43ºC)
is exceed as very serious damage can occur at temperatures of 125ºF (52ºC).

Also.. look at where car batteries are located.. right by the HOT engine.. I would guess that maybe the heat had something to do with the short battery life in the boat mentioned but more likely the guy just tortured and neglected the batteries.
And this has become a real problem in the automotive market. In the last 17 +/- years under hood temps have increased by approximately 30F due to how "packed in" everything is. Many manufacturers have now moved the batteries out of the engine bay as a result. If we want to use "anecdotal" evidence my mother-in-law lives in Florida (Vero Beach). She drives the same brand car as my wife and her factory battery lasts 2 - 2.5 years. My wife has never once replaced a factory installed battery in any of her cars. The first Pilot we sold had 191K on it with the original battery, the second was sold with 201K and original battery, and her current Honda/Acura vehicle has 221K with the original factory battery all confirmed with battery date codes matched to model year of manufacture. My wife never sits in traffic, it does not exist where we live, and we live in Maine with cool temps, below 77F, most of the year. As a result replacing car batteries is not something we really worry about like her mother does in hot sunny Florida. We are coming up on 8 years and 221K on the current battery and CCA testing shows it still very, very strong.

Heat really does murder all the alkaline battered in the house however. House gets left with no AC during the summer and every battery in the house - new or used - is dead when we come back to the house.
Heat is not good for any battery including LiFePO4... If you have an opportunity to get a battery out of a hot location, as we did, do it... Did heat murder these batteries? No, not at all, but it was likely a partial contributor especially if they were deep discharged while at high temps..

The biggest killer of these batteries, in order, IMHO:

Sulfation was the killer - How?

Cheap pieces of shite - These are not anywhere close to a deep-cycle battery
Not getting back to 100%/PSOC Cycling
Capacity walk down
Inadequate alternator/voltage drop
A few super deep discharges
Heat
 
Feb 14, 2014
4,032
Hunter 430 Saba Waveland, MS
Nice post!
My 2W solar panel, OEM, is dead. It is connected to my starter battery as shown.
I need a new panel and a replacement is rated 7Watts (cough cough) with no voltage regulator.

Some panels show a voltage regulator and a few "helpers" say that an unregulated panel will kill my starter battery.

I say no.
What is your opinion?
Jim...
 

Attachments

Jun 1, 2007
3,319
Macgregor 26S Hobie TI, Capri Coronado 15 Denver, Colorado
The owner was lamenting that the SOC had been dropping more rapidly as the summer grew on. In total he and his family did approx 25 over-nights that resulted in "deep cycling" the batteries plus a few very deep discharges before the Smart Gauge was installed and 5-6 days racing with the fridge running
I dont know exactly what amp hours a fridge uses but have heard its anywhere from 35 to nearly 100 amp hours per day. If you only have a total of 230 amp hours capacity and dont have a good way to keep track of use (ie, a very inaccurate volt meter only), I would think the heavy cycling of the fridge was much more likely to be the culprit for the dead batteries - but its all guessing. Accidentally leave the fridge on once of twice when you leave the boat for a week - bad for the batteries.
 

Maine Sail

Moderator
Feb 6, 1998
11,037
Canadian Sailcraft 36T Casco Bay, ME
Nice post!
My 2W solar panel, OEM, is dead. It is connected to my starter battery as shown.
I need a new panel and a replacement is rated 7Watts (cough cough) with no voltage regulator.

Some panels show a voltage regulator and a few "helpers" say that an unregulated panel will kill my starter battery.

I say no.
What is your opinion?
Jim...
How about actual data? How about numerous customers who've destroyed batteries using unregulated solar? How about an 11W solar panel pushing a bank of 220Ah Lifeline AGM batteries to over 15.5V.... A start battery is almost always full so a 7W panel would have the capability to overcharge a typical starting battery if left unattended.

Do I Need a Solar Controller?
https://marinehowto.com/do-i-need-a-solar-controller/



.
 
May 27, 2015
35
Beneteau Oceanis 41 Havre de Grace MD
Maine Sail,
Slightly off topic question. I have a new boat with 4 new AGM batteries. 1 Start, 2 House, 1 Bow Thruster. The boat is going on the hard for the winter in Havre De Grace MD. The boat will not be hooked to power while out of the water. I was planning to pull them and keep them in my heated shop on a battery tender. Is pulling the batteries a good idea / necessary??
 
Feb 14, 2014
4,032
Hunter 430 Saba Waveland, MS
How about actual data? How about numerous customers who've destroyed batteries using unregulated solar? How about an 11W solar panel pushing a bank of 220Ah Lifeline AGM batteries to over 15.5V.... A start battery is almost always full so a 7W panel would have the capability to overcharge a typical starting battery if left unattended.

If I understand, then you recommend a voltage regulator on the solar panel. My main bilge, windlass and winch is connected to this starter battery. I wanted to get the new panel to maintain starter batt (wet cell) "topped off". Summer time my dehumidifier puts condensate to main bilge and without charge to start batt, as currently wired. I will examine the specs on the prospect to see the max voltage. Have no "actual data" since the panel was dead when I bought the boat.
 
May 17, 2004
1,946
Beneteau Oceanis 37 LE Havre de Grace
Maine Sail,
Slightly off topic question. I have a new boat with 4 new AGM batteries. 1 Start, 2 House, 1 Bow Thruster. The boat is going on the hard for the winter in Havre De Grace MD. The boat will not be hooked to power while out of the water. I was planning to pull them and keep them in my heated shop on a battery tender. Is pulling the batteries a good idea / necessary??
We have the same setup in the same location. Last year (our first with this boat), I made the mistake of not disconnecting the house batteries for the first few weeks of winter. Came back to nearly dead batteries. Turns out that the panel itself draws a significant amount over a matter of weeks. After that I disconnected the positive cable from the house bank, and just came back every few months after to run the charger for a few hours. There was no significant drain from the engine or thruster batteries. My understanding is that the self discharge rate of AGMs is pretty good to begin with, and even better in cold than warm. Of course I defer to Maine Sail if he replies with anything different.
 
Aug 16, 2009
995
Hunter 1986 H31 California Yacht Marina, Chula Vista, CA
If you have a switched fuse at the battery box, disconnecting the cable itself can be avoided. Or if you think the panel is the only culprit you could install a battery shut-off switch in the main line to the DC panel
 
Feb 10, 2004
2,982
Hunter 40.5 East Greenwich, RI
I have a pair of series connected 6V GC batteries. I just open the jumper between each set of batteries, and pull one cable off my starting battery. Be sure that the tops of the batteries are clean and dry. Spilled electrolyte on the surface can cause leakage between the terminals.
 
May 27, 2015
35
Beneteau Oceanis 41 Havre de Grace MD
Thanks for the input all.
I spent yesterday going over the boats electrical system. As far as the batteries are concerned I was wrong about the total number of batteries. There are 2 start, 3 house, and 2 thruster / windless batteries. So it looks like what you guys are saying is after fully charging turn the red battery and black ground switches to off and disconnect the cables from all the batteries and I should be good to go?