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Author Topic:   Strange Deep Cycle Battery Failure

David Pendleton posted 10-20-2012 08:14 PM ET (US)
I pulled the batteries off the boat this weekend. The techs at the marina told me they were "dead" and would not start the engine. They are both NG-27 deep cycle batteries.
One of them was new; I bought it this spring. I haven't run the engine since mid-August.
When I checked the battery with a multi-meter, the voltage was 11.7-Volts. Hardly "dead" in my opinion. I put the battery on a charger at 2-Amperes for about 8 hours; when I took it off the voltage was about 12.8-Volts.
When I disconnected the charger, I immediately hooked up the multi-meter and watched for about five minutes. During this time the voltage steadily dropped back down to 11.7-Volts. It might have dropped lower if I'd waited longer, I don't know. This doesn't seem normal to me. The battery is still under warranty. Should I take it back or put it back on the charger for a couple more days?
tmann45 posted 10-20-2012 08:31 PM ET (US)
Sorry David, 11.7 volts is pretty much dead, not quite but close enough. And if the voltge dropped right back down to 11.7V after a charge, even a small one like you did, I would say that battery is fork tender. Take it back for a replacement.
Tom
L H G posted 10-20-2012 08:33 PM ET (US)
Dave - Sounds like a bad battery - maybe a bad cell. But for starting you should have one starting battery instead of a deep cycle, or a dual purpose battery. Deep cycles are not known for starting power, but preferred for house power or electric trolling motors.
bloller posted 10-20-2012 08:40 PM ET (US)
I have a group 27 deep cycle battery for starting. It has far more Cold Cranking Amps than my old group 24 starting battery.
David Pendleton posted 10-20-2012 08:56 PM ET (US)
Thanks all. This brings me to the second part of my quandary. The tech (a new one to my boat) also told me my batteries were too small and of the wrong type.
I bought my boat new in 1999, and it came with two NG-27 deep cycle batteries. I've never had a starting problem and I also run a lot of electronics and accessories without a problem.
The tech told me I need a marine starting battery (to start the engine) and a deep cycle engine to power things when the engine isn't running.
I guess that makes sense, but I've never run that configuration. My current batteries claim 675MCA (Marine Cranking Amps), shouldn't that be enough to not require a "starting" battery?
David Pendleton posted 10-20-2012 09:01 PM ET (US)
I should also point out, for those that don't already know, my Whaler is powered by a 5.7L Mercruiser V8, not an outboard...
outragesteve posted 10-21-2012 02:52 AM ET (US)
Dave: Using a volt meter to test a battery is not a good way to judge the condition of the battery. Using a load tester is the preferred method. When a good 12 volt battery is fully charged, using a volt meter as a "static" check should result in 13.0-13.4 volts. Again, this does not reflect the load ability of the battery. Good luck!
tmann45 posted 10-21-2012 07:58 AM ET (US)

quote:
My current batteries claim 675MCA (Marine Cranking Amps), shouldn't that be enough to not require a "starting" battery?

You should be able to find the required MCA or CCA for your engine. If it is less than 675 MCA then you are OK to use that deep cycle battery for starting. The main difference in starting and deep cycle batteries is starting batteries give you a lot of amps quickly, deep cycle give you the amps slowly over a long period of time. If you have a "Both" or "1+2" position on your battery switch, that position will double your MCA when starting.

quote:
The tech told me I need a marine starting battery (to start the engine) and a deep cycle engine to power things when the engine isn't running.
Not necessarily so, and in my opinion a BCI Group 27 battery is not too small for your engine.
jimh posted 10-21-2012 08:59 AM ET (US)
If the battery terminal voltage rapidly decreased to 11.7-Volts after having been charged for eight hours to 12.8-Volts, there is something wrong. It is natural for the surface charge on the battery to dissipate when the charging current is removed, but typically a battery will rise to more like 13.2-Volts or higher, then decrease to about 12.7-Volts. A battery has six cells. The resting full charge potential for five cells would be roughly
2.1-Volts/1-cell x 5-cells = 10.5-volts
The voltage you observe is too high for a battery with a shorted cell. A terminal voltage of 11.7-Volts is more typical for a six-cell battery that is deeply discharged.
I recommend the following remedies:
--return the recently purchased battery for a replacement under the warranty
--check the electrical circuits on the boat for a possible parasitic discharge current
I believe the most likely cause of the low charge on both batteries is the presence of some parasitic discharge current in the boat wiring. A bad diode in the alternator can cause a discharge current. If the engine is operated on a regular basis, the alternator still provides charging current that may overcome the discharge when the engine is not running.
jimh posted 10-21-2012 09:06 AM ET (US)
Regarding batteries designated for engine cranking and ones designated for deep-cycle, the only real difference is the size of the battery for the amount of current it can produce. Cranking batteries, also called starting, lighting, and ignition batteries or SLI batteries typically use thin plates of lead to create more current capacity in a small space. Deep-cycle batteries use thicker lead plates and are typically larger in size for comparable current than an SLI battery.
As the name suggests, a deep-cycle battery is more tolerant of deep discharge and recharge cycles than an SLI battery, which is intended to be kept on a float charge most of the time the engine is running except for brief periods when furnishing engine starting current.
jimh posted 10-21-2012 03:07 PM ET (US)
The amount of stored electrical energy in a battery is described by the Ampere-hour capacity (A-h). I would expect that a 12-Volt battery of size GROUP 27 would probably have a capacity of 40-A-h. If we assume that David's battery was completely discharged, and that he charged it for 8-hours at a rate of 2-Amperes, the battery would only have received about 16-A-h of charge--and that is assuming 100-percent efficiency which is not likely. We are also assuming that the charger supplied 2-Amperes all the time. It is likely that did not happen, either. Some batteries when very deeply discharged seem to have a higher resistance than normal, and they may not accept charge the way a battery with only a partial discharge would. Considering all effects, it seems reasonable that David did not really restore the battery to full charge. At best, he only got the battery back to about 40-percent of full charge. At worst, much less.
Because David describes the battery as being a deep-cycle battery, the battery should be tolerant of a deep discharge. Before abandoning the battery as having failed, I would try re-charging the battery a second time. Put the 2-Ampere charger on it, and let it have a couple of days to charge.
The construction of the battery was not identified. I presume it is a flooded-cell battery. If so, check the water level in all cells.
David Pendleton posted 10-21-2012 04:05 PM ET (US)
According to the Clymer manual for my engine, the battery requirements are: 550 CCA/700 MCA/120 Ah.
My current batteries are marked 675 MCA, 182 reserve minutes and 105 Ah. They are "maintenace-free" flooded cell batteries.
Indeed, they are too small. I plan to return the battery still under warranty and replace it with a marine starting battery sized appropriately for my engine. The other (3 year-old) battery fared much better and is charging normally.
L H G posted 10-22-2012 01:03 AM ET (US)
You can readily buy Group 24 or 27 starting or dual purpose batteries with 900-1000 Marine Cranking Amps at most marine outlets, including Cabelas or Bass Pro. Mercury Optimax engines require similar sized batteries.
David Pendleton posted 10-22-2012 07:50 PM ET (US)

quote:
If you have a "Both" or "1+2" position on your battery switch, that position will double your MCA when starting.
I do, and I always leave it on the "Both" setting, unless I am sleeping on the boat, where I put it on "2."
I'm curious though, on my boat the batteries are wired in parallel. The EXIDE web site states that when wired in parallel, the Voltage remains at 12, and the Ah rating for the batteries is summed. It does not mention MCA. Is this really the case?
If so, I was starting with more than 1300 MCA, which might explain why I've never had a problem...
tmann45 posted 10-22-2012 09:24 PM ET (US)
Since I am the one who said that, you know my answer, YES.
I also agree with your practice of two deep cycle batteries run in parallel except when there is a possibility of running them both down and not being able to start in the morning.
I ran my dual starting batteries the same way and was thinking about switching to deep cycle when they need replacing, plenty of cranking power and better for durability and deep discharge. Then Sears had a sale on their AGM (Odyssey) batteries and I installed an automatic charge relay instead.
K Albus posted 10-23-2012 08:45 AM ET (US)
With a 1-2-Both switch, you should only use "Both" when the batteries are weak and you need to combine them in order to get enough juice to start your boat. Otherwise, you should have the switch on 1 or 2.
If you intend to continue boating in remote areas such as Isle Royale, you should seriously consider adding a Blue Sea Systems ACR ( http://bluesea.com/category/1/productline/overview/329 ) or a BEP VSR ( http://www.bepmarine.com/home-mainmenu-8/product-277/ 716-v-140a-dvsr-single-engine-two-battery-banks ) to your system. These products will allow you to isolate your engine loads and your house loads on separate batteries. That way, you don't need to worry about running down your starting battery by playing the stereo or leaving the running lights on all night. These products keep both batteries charged, and let you combine the batteries for emergency starting. Search the archives here for more information about either product.
K Albus posted 10-23-2012 09:08 AM ET (US)
By the way, I added the Blue Sea Systems Add-A-Battery kit (with ACR) to my Dauntless 180 before the 2010 Isle Royale trip. My new boat has a BEP VSR cluster on it. Of the two, the Blue Sea Systems product is the easier to use on an everyday basis, while the BEP system has a little more flexibility.
The battery switch on the Blue Sea Systems system has three positions: Off, On, and Emergency Combine. When using the boat under normal circumstances, the switch is set to On. In this position, one battery is used solely for starting the motor, and the other battery is used for all of your house loads. When storing the boat, move the switch to Off. If you ever have a situation where your starting battery is too weak to start the motor, move the switch to Emergency Combine to use both batteries at the same time. The ACR lets the system charge both batteries while the boat is running, without moving the battery switch. (It is my understanding that in a typical system with only a 1-2-Both switch, the alternator will charge battery 1 if the switch is set to 1, and will charge battery 2 if the switch is set to 2, but will not properly charge both batteries if the switch is set to Both. See: http://www.boattest.com/Resources/view_news.aspx?NewsID=3084 ) The ACR also provides the added benefit of isolating your electronics from the starting circuit when you are starting the boat. This provides a level of added protection to your electronics.
The BEP VSR cluster systems consists of three separate switches: one for the starting circuit, one for the house circuit, and one emergency combine switch. The BEP system separates the house loads on to one battery and the starting load on to the other battery. The VSR charges both batteries when the boat is running, without the need for moving any of the battery switches. For normal use of the boat, both the starting battery and house battery switches are turned on. If the starting battery gets run down, the emergency combine switch can be turned on to use both batteries to start the motor.
The Blue Sea Systems system, you only have one switch to flip on and off when you use the boat. With the BEP system, you have two switches that typically must be switched on and off under normal use.
tmann45 posted 10-23-2012 11:51 AM ET (US)
From Kevin's link to BoatTest.com
quote:
If the switch is in the “BOTH” position and one battery is nearly at a full charge and one is flat, the alternator will “read” the higher of the two, and the flat battery will never be charged.
This is a completely false statement. An alternator cannot "read" an individual battery in a two battery paralleled system.
When you connect two batteries with different charge states they immediately start to equalize, the higher charge state one charges the lower charge state one. Depending on the size of the wires connecting them (battery cable) it won't take long (seconds? or milliseconds?) for them to be at the same voltage and that is what the alternator will see. They might be at different charge states but the voltage will be the same and that is the only thing the alternator sees ("reads").

quote:
With a 1-2-Both switch, you should only use "Both" when the batteries are weak and you need to combine them in order to get enough juice to start your boat. Otherwise, you should have the switch on 1 or 2.
Maybe for most people this is a more foolproof way to operate your electrical system, but if you are diligent and want to get the most of your batteries, it is better to run with the switch in the Both position and switch to one battery when not charging for safety. Pretty much what David was doing. And you should only use Both when both batteries are weak, if one is dead and the other fully charged do not use both, use only the one that is fully charged to start the engine, otherwise the dead battery will suck juice out of the fully charged one and give you less starting power.
I don't know if the information is still on the website, but it is from an electrical engineer concerning boat electrical systems. See: http://www.yandina.com/
K Albus posted 10-23-2012 12:12 PM ET (US)

quote:
it is better to run with the switch in the Both position and switch to one battery when not charging for safety. Pretty much what David was doing. And you should only use Both when both batteries are weak, if one is dead and the other fully charged do not use both, use only the one that is fully charged to start the engine, otherwise the dead battery will suck juice out of the fully charged one and give you less starting power.
Adding an ACR or a VSR lets you avoid all of this switching of the batteries.
jimh posted 10-23-2012 12:52 PM ET (US)
I made a conservative estimate of the Ampere-hour rating of David's battery as 40. David later informed that the battery was 105-Ampere-hour capacity. To review the charging situation, we see that a 2-Ampere charge would have to be applied for at least 53-hours to restore full charge to a battery of that capacity that was fully discharged. If I factor in the other allowances I mentioned (for lower current delivery from the charger and less than 100-percent efficiency in producing a stored charge), I would expect that perhaps 100-hours of charging might be needed. Since David reported initially he only charged the battery for 8-hours, the amount of restored charge may have been correspondingly low, and perhaps only 10-percent of full charge was restored.
It seems best to not let any lead-acid battery--of any type construction--sit in a deeply discharged state for very long, and in general it seems like a good practice to avoid, if possible, pulling a lead-acid battery to a deeply discharged state at any time.
Flooded cell lead-acid batteries will have a slightly higher self-discharge current than other types if those other types happen to use pure lead for the plates. But usually the self-discharge current is not so high that it will fully discharge a battery in a matter of a few months. I would not let a battery sit for a year without any charge and expect it to be in perfect condition, but the typical six-month winter storage period for boaters in the Northern USA can usually be managed by almost any lead-acid battery. The self-discharge rate decreases with temperature, so if stored in a cold environment, the self-discharge rate is lowered. Six-months of no charging during a hot summer may be harder on a battery. The self-discharge rate is higher and there may be evaporation of the electrolyte in a flooded-cell battery.
tmann45 posted 10-23-2012 12:54 PM ET (US)

quote:
Adding an ACR or a VSR lets you avoid all of this switching of the batteries.
Yes, and the ACR or VSR does what I am saying is the best way to use a two battery setup, connect batteries in parallel (switch in Both position) when running or charging, and switch to one battery when not charging. Not everybody wants to spend the $90 for a ACR or up to $300 for VSR system plus the battery cables and installation charges, some will just turn the battery switch.
tmann45 posted 10-23-2012 01:04 PM ET (US)

quote:
I would expect that a 12-Volt battery of size GROUP 27 would probably have a capacity of 40-A-h.
Generally Group 27 deep cycle batteries are rated at about 100 amp hours.
David Pendleton posted 10-23-2012 03:46 PM ET (US)
My boat has a Perko Medium Duty Battery switch installed, so I sent an email to Perko asking for clarification about the switch positions and charging behavior. Here is the reply:

quote:
Hello,
In the ALL position the switch will charge both batteries at the same time. Electricity always follows the path of least resistance so if one bank is fully charged, the energy will naturally flow into the second one. (provided the battery is receptive)
The switch is designed so that you can use position ONE for cranking your engine. While en-route to your destination switch it to the ALL position to charge both batteries. When you anchor up turn your engine off and go to position TWO for radio, lights and appliances. You would repeat the process on the way back ensuring you always have a cranking battery charged.
Regards,
Manny
ericflys posted 10-23-2012 11:48 PM ET (US)
It's a time proven method, but for those looking for something simpler, with nothing to forget, the BlueSea or BEP are a good option. I wouldn't go with anything but the BEP or BlueSea dual battery option on a single engine Whaler except perhaps the 15 or smaller unless on a very tight budget, and if that's the case, maybe Whalers are not the best choice of boat for you...
jimh posted 10-24-2012 09:50 AM ET (US)

quote:
Generally Group 27 deep cycle batteries are rated at about 100 amp hours.
The Ampere-hour rating depends on the discharge current. It seems that a discharge of 20-Amperes is typical for a rating, but you should check the specifications carefully. If the Ampere-hour is calculated at a lower discharge rate, the Ampere-hour number will be inflated.
A good method to estimate is by weight. I have some stationary power batteries that are rated at 75-A-h at a 20-Ampere discharge. They are so heavy you can barely lift one by yourself, yet they are only rated as 75-A-h.
INTERSTATE has a marine deep-cycle battery in size Group-27. They don't give it an A-h rating, but they say at a discharge of 5-Ampere it will run 19-hours. That is a rating of 95-A-h, but at a very low discharge current. The same battery at a discharge of 15-Ampere is only rated for 5.5-hours, or 82-A-h. I suspect that if rated at 20-Amperes the A-h rating would drop to more like 70.
tmann45 posted 10-24-2012 04:42 PM ET (US)
Jim, if you need a lighter, higher amp hour rated battery, try the Trojan 27TMX12V: http://www.trojanbattery.com/Products/27TMX12V.aspx
Only 55 lbs and 105 amp hours at the standard 20-hour rate (not 20-amp rate, a 25-amp rate will give you Reserve Capacity).
jimh posted 10-25-2012 09:07 AM ET (US)
I don't need a battery, but the one cited from TROJAN is quite nice; it happens to fit the generalization of Group 27 size batteries having a rating of 100-A-h at the 20-Ampere discharge rate. But I suspect that is one expensive battery.
The stationary power battery I mentioned is about the same size. It weighs about 85-lbs, has a 75-A-h rating, and also specifies the discharge voltage as 1.75-Volt-per-cell and the temperature of 77-degrees. The discharge voltage and temperature are other factors that affect the Ampere-hour rating. Ampere-hour is a parameter that can be hard to compare if all the parameters are not the same.
In any, case, to get back to David's situation, as I said, already, twice, his recharging of the battery was not sufficient to get it back to full charge, which was the point I was trying to make.
Deeply-discharged batteries can act strangely. I have seen some that will not accept a charge initially. If you leave them on charge they may come back to life and begin to accept charge. But your results may vary. That's why I recommend that deeply discharging a battery and leaving it sitting in a discharged state for a long time should be avoided.
Contrary to some advice given here, it is difficult to find a deep-cycle battery with a marine cranking current rating of 1,000-Amperes. Returning to the INTERSTATE brand as an example, they have an SLI battery with 1,000-MCA rating, but their deep-cycle battery is only rated at 500-MCA. Compare at
http://www.interstatebatteries.com/cs_estore/Content. aspx?dsNav=Ntk~SearchGroup|MarineDeepCycle|3|
The INTERSTATE 24M cranking battery is about the only one I know that delivers 1,000-MCA in that size.
6992WHALER posted 10-25-2012 09:58 AM ET (US)
I replaced both my starting group 27 batteries with these diehard group 24 batteries this spring. More power less weight. So far they have worked great.

http://www.sears.com/diehard-marine-starting-price-with-exchange/ p-02827415000P?prdNo=3&blockNo=3&blockType=G3
David Pendleton posted 11-01-2012 11:51 PM ET (US)
I' happy to report that after several days on the trickle-charger, both batteries are behaving normally. I'm checking them twice a day (they're in the garage, and I have the MM next to them).
I may still replace (the older) one with a starting battery, but I think more research is in order...

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