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REALLY Dead Battery ???

3K views 19 replies 12 participants last post by  sailingfool 
#1 ·
Our 28 footer has very simple electrics with a single group 27 deep cycle servicing house and our 15 HP outboard. It is on a mooring, usually with a 30 watt solar panel with PWM regulator, but since the battery voltage was 12.7 volts when we left the boat two weeks ago, i did not hook up the panel.

Going to the boat today, everything was dead. The voltmeter read 2.6 volts directly from the terminals. I know all breaker circuits were OFF at the panel. I have two devices that are not wired through the breaker panel: a bilge pump (maybe with a stuck switch??) and an incadescent bulkhead light ( that could have been left on).

So my question is: would a constant 2 week draw from a light or bilge pump reduce a group 27 deep cycle battery to 2.6 volts? Or could there be some other failure within the 9 year old battery itself causing this voltage reading?

In other words, does this battery just need a good slow recharge or is it toast?

Thanks
 
#3 · (Edited)
Yes, either of those could do it. Even a 12W lamp is 1A, and will flatten your battery in less than a week.

Edit : missed the bit about the battery being 9 years old. There are two scenarios :

1) Your battery suffered an internal failure and went flat on its own. You need a new one.

2) You flattened the battery by leaving something on, and now you need a new one.

Good news, your 9 year old battery was so sulphated that it had lost most of its capacity, so you didn't lose a battery. 20% of one at the most.
 
#4 ·
168 hr in a week... 1 amp bulb X 2 weeks = 336 ah = 3X to 6X the capacity of your battery.

You're lucky it had measurable voltage.

Normally, a good charge at 5 AMPS to full followed by an hr at TVG should have the battery back in service with just a few months of useful life lost.

But for a 9 yr old battery it probably didn't have a few months left.
 
#6 ·
It might be worth a little battery CPR. It's a bad discharge, but it is still just a discharge. Amazing what a deep cycle will survive. Many chargers will not even try to bring back a batt from that voltage. My best luck has come by starting with a really stupid shunt charger @ 1A. Smallest, dumbest charger there is. Leave it on until battery voltage reaches 12 or 13. Now hit it with a bigger charger -- 5 or even 10A. Drive it to 14.4v. Let it rest. Drive it again. If you have a smart charger or high-amp alternator, great. If not, just keep cycling it manually with a shunt charger. Then unhook it & let it rest. If it settles out around 12.2v, carry on as before. You've done some damage, but it's like hitting a '95 Civic with a shopping cart. Least of its problems.

A battery with internal damage will behave very erratically. You can't mistake collapsed plates.
 
#7 ·
Sounds like you may have left a light on, but even if everything is shut off, there remains a parasitic load from many electronic devices that can slowly drain a battery. You wouldn't expect parasitic load to kill off a healthy battery, but being 9 years old could mean it had very little of it's original amp hr capacity left. The 12.7 volts you saw does not indicate capacity.

As some have mentioned, you could try to recharge it. There are two risks. First, she takes a charge, but really has very little capacity and you find yourself without a battery, while sailing. Second, damaged batteries can be an explosion danger, particularly when charging.

As others mentioned, nine years is a very good useful life. You're replacing soon one way or the other.
 
#8 ·
You must have a horseshoe some where if that's the first time your battery has gone dead in 9 years. It happens to me a couple of times a year, usually because I leave the key on. I wouldn't worry about it, try to charge it back up. It might be worth checking the fluid levels too. If adding water and charging doesn't work, buy a new battery and hope you get another 9 years problem free.
 
#9 · (Edited)
Time for a new battery. Being in the field I test batteries daily for actual Ah capacity. I have two AGM's running on 20 hour discharge tests as I type this. 10.5V, while under discharge, is considered 0% SOC.. The resting recovery voltage, after a 20 hour discharge to 10.5V, is between 11.1V and 11.4V depending upon how long you let it sit at 0%, which you simply don't want to do for more than a few hours. Taking a batteyr to 10.5V then immediately recharign to 100% SOC won't damage it as much as taking the same battery to 50% SOC and not getting back to 100% SOC for a week or more. It is teh time at the low SOC that really causes the damage to the battery. Anytime you discharge to below 10.5V or 11.4V rested, both are 0% SOC, serious capacity degredation going to happen.

Taking a battery down below 3V is grossly beyond 0% of capacity and permanent damage will occur. Yes there is more energy below 10.5V to be had, but not a lot, and it drops off rapidly below that point. Below 10.5V loaded, (unless short duration in-rush loads) permanent damage is occurring.. I have tested far too many batteries, known to be testing well before an over-discharge, to suggest not replacing them...

Most recently was a bank of very expensive batteries that had been testing at about 96% of rated capacity in February of 2016. The owners crappy Rule bilge switch stuck ON and murdered his bank. They sat at well below 6V for approx 3-4 days before he found the issue. I retested the batteries in late July and they delivered between 27% and 28% of rated capacity, and this was after going through a lengthy recovery process... In other words the batteries had become boat anchors.. You got 9 years, pony up the $80.00, move on and call it a day. :wink
 
#10 ·
Thank you all, I do intend to get a new battery, i recognize that 9 years is a very good service life. I was really more interested in the battery science, whether the 2.6 volt reading was accurate and whether that value clearly pointed to either VERY deep discharge, or an internal failure.

Now I gotta find a good quality 12 volt group 27 deep cycle in the Boston North area. Maine Sail's informative article on how many deep cycle batteries really aren't has me looking for either a Trojan or US Battery unit.
 
#11 · (Edited)
Thank you all, I do intend to get a new battery, i recognize that 9 years is a very good service life. I was really more interested in the battery science, whether the 2.6 volt reading was accurate and whether that value clearly pointed to either VERY deep discharge, or an internal failure.
Internal failures usually manifest as 1 cell internally shorting and the battery becoming a 10V battery as opposed to a 12V battery. On very rare occasions I have seen them turn into 8V batteries with two cells internally shorting/failing. A 2.6V reading would mean 5 cells have failed and that is quite unlikely.

Now I gotta find a good quality 12 volt group 27 deep cycle in the Boston North area. Maine Sail's informative article on how many deep cycle batteries really aren't has me looking for either a Trojan or US Battery unit.
If you have a bit of extra height then why not go for a 12V Golf Cart battery such as the Trojan T1275 or the US Battery US12V XC2. These batteries are in a BCI classification called a GC12 battery. Deka also makes a GC12 and some Sam's Club stores even stock a re-branded Deka GC12.

GC12 batteries are actually deep cycle 12V batteries unlike a pseudo deep cycle Group 24, 27 or 29/30/31.. A GC12 offers more Ah capacity, thicker plates, and significantly better cycle life performance.

Golf cart batteries come in 6V, 8V and 12V models and most folks only think of them in 6V... Just google GC12 battery if you want an actual deep cycle 12V battery..

If boat builders actually cared about you as a customer they would have been installing true cycling batteries years ago, instead of Group 24, 27, 31, 4D or 8D's.....:wink
 
#14 · (Edited)
Maine sail, can i infer from your comment that any GC12 battery will likely be a true deep cycle, where so many of the Group 24s and 27 s are not?
A GC12 (GC stands for Golf Car) battery shares the same physical plates, grid, seperators and electrolyte chemistry as a GC2 6V battery. The only difference is they place these cells into a 6 cell case (12V) as opposed to a 3 cell case (6V).

GC12 batteries are NOT the same as Group 24, 27, 29/30/31, 4D or 8D they are a real cycling battery designed from the ground up for cycling. They are not a re-stickered automotive grade battery with a "sticker" that just insinuates it is a cycling battery when it really is not... For example Trojan's GC12 / J150 / T1275 is rated for 1200 lab cycles to 50% DOD, Trojan's G24, 27 & 31 flooded 12V battery is rated at just HALF of that at 600 lab rated cycles to 50% DOD..



You DO NOT need to buy flooded 6V batteries to find actual deep cycle flooded 12V batteries but you do need to choose 12V batteries that were actually designed for cycling purposes, such as golf car (GC) batteries or sweeper/scrubber batteries. There are even larger 12V deep cycle batteries too such as the Trojan J185's as well but these are even taller than the GC12/J150/T1275's.

If you have the height you will always be best served to buy quality cycling batteries and not flooded 12V G 24, 27, 29/30/31, 4D or 8D's..

I posed this question to one of the senior battery engineers at one of the USA's larges battery manufacturers who makes all types of batteries.

Question asked by Marine How To.com:

"If the GC2, GC-12 or L16's were cycled using the same cycle life testing as the 12V Group 24, 27, 31 etc. what would that outcome, in cycle life, actually look like? Is it fair to suggest a GC2, GC12 or L16 battery has double to triple the lab cycle life, to 50% DOD, than the 12V 24, 27 & 31 "deep cycles" do?"

Senior Battery Engineer - Major US Battery Manufacturer:
"Yes, for packs of equivalent energy content (voltage * capacity) the Golf Car types and L16's are 2-3 times better than the DC automotive sizes (24, 27 and 31)."

Straight from the source, golf cart batteries are 2-3X better than 12V Group 24, 27 & 31 etc.. Flooded 12V Group 24, 27 & 31 batteries are simply "deep cycle" imposters.
 
#15 ·
I totally agree with Maine Sail about the golf cart batteries versus the typical marine/RV batteries. If you have the space (height in particular) and willing to pay the higher price, go for it. If not, get the best marine/RV "deep cycle" you can find and afford. Probably OK for your application.
 
#16 ·
IF... you have (or can create) enough height in your battery storage area, please go to a good quality 6 volt Golf Cart design.

We had to replace our 9 year old Trojan T-145+ pair of "house bank" batteries this summer and put in two more of the same model.
These are in a space that the factory installed two group 24 batteries when the boat was built in '88.

(I do have a separate emergency 12 volt AGM battery just for such an "emergency", and it did indeed start up the engine the morning after spending a night aboard this spring.)

I subscribe to the theory that "real" deep cycle batteries are not expensive over the longer period of time that they last, and likely are less $ per year than the cheap ones.

Loren
 
#17 ·
There are constructional and performance differences between industrial Deep Cycle batts (like the L-16) and your intermediate Group 27 types, but that doesn't mean the latter are garbage. They offer a compact, liftable, affordable power source adequate for many boater's needs. There are thousands of them on bass boats, recreational sailboats, signage & remote sensing installations, and powering modest shoreside loads. They've been around for a long time, and their performance curves are well understood.

I have ~2600 lbs of flooded lead-antimony forklift batteries in my basement. These are designed for repeated deep discharges over an 8hr shift, followed by rapid, full, high-amperage recharging. I also have ~8000lbs of flooded lead-calcium telecom batteries on the porch, awaiting the recyclers. Those were designed to live on float, discharge hard and steadily during (rare) power failures, then recharge slowly at their leisure. They are part of a bank first installed in 1990, and I just managed to kill them off this year, having treated them the second half of their life in ways they were never meant to be treated.

These are both true deep-cycle batteries, with plates up to 1/4" thick and plenty of reserve capacity. Yet they are very different from each other in a number of ways. I can probably ride the forklift batts harder for a given capacity, maybe even milking more Ah/pound and Ah/dollar out of them across their total lifespan -- but I don't expect them to last 26 years, either. Two 'industrial' batteries, but intended for very different industries. And they make L-16s look like Group 24s. Does that mean L-16 are garbage? Nope -- best batteries for floor polishers. T-105s are an excellent choice for golf carts.

There are deeper-cycling batteries than Group 27s out there, yes. Some of them may even fit your boat and budget. But look at it this way: your last battery fulfilled your needs for 9 uncomplaining years, at a reasonable cost in dollars, charging rate, weight, and space consumption. I'd say it was a pretty good match, and therefore not any sort of imposter. It is what it is; it did what you needed. :)
 
#18 · (Edited)
"GC12 batteries are actually deep cycle 12V batteries unlike a pseudo deep cycle Group 24, 27 or 29/30/31.. A GC12 offers more Ah capacity, thicker plates, and significantly better cycle life performance."

The US Battery XC2s have the same cycling specifications for groups 24, 27, 31, or GC12. Take a look at the spec sheets. They are all rated for 1150 cycles to 50%. The GC12 is bigger, that's all. Maybe the GC12 has heftier construction, but the deep cycling behaviour of the smaller groups seems to be perfectly acceptable.

If the OP really wants a group 27, a US Battery 27DC XC2 is a genuine deep cycle that will slot straight in.

If the old battery lasted 9 years, doesn't it suggest that the size and construction were sufficient?
 
#19 · (Edited)
I like Fred W. of USB, he is a really bright battery engineer who knows his stuff.. However, the data they claim is not entirely accurate nor is it entirely honest in regards to the 24, 27 or 31..

Think about it, USB is suggesting/claiming/marketing that their G 24, 27 & 31 "deep cycle" battery is TWICE AS GOOD as a Trojan and THREE TIMES AS GOOD as a Deka/ East Penn. This is on par, technology advancement wise, to the Carbon Foam Firefly in terms of performance gains. Independent test data does not back these claims up. I put the USB 24, 27 & 31 right up there with Trojan, which are slightly better than Deka. When you push Fred on this issue he will fully admit it that the data for the automotive sizes is not really what they claim or suggest it is in the "marketing" speak...

The 12V Group 24, 27 & 31 are certainly comparable to the Trojan Group 24 (SCS150), G27 (SCS200) and G31 (SCS225) but Trojan is actually more honest in their lab data claims. Lab data is actually meaningless in the real world too but can give decent guidance within a brand, for durability and cycle life guidance, if that manufacturer is not BSing..

In my experience Crown, US Battery and Trojan make some of the best 12V automotive type batteries but they are not going to cycle comparably to a GC or industrial type battery. FWIW these three are the ONLY automotive style "deep cycle" batteries I have tested that have ever met their Ah ratings and even then it is quite rare.

I have not tested a single flooded Group 24, 27 or 31, from any other manufacturer, that could deliver its rated Ah capacity when new (7-12 cycles), broken-in 15-60 cycles) or slightly used (1 seasons use). I have tested GC2 batteries and GC12 batteries from almost all makers and seen them hit Ah ratings much more reliably.

I was recently talking with the lead engineer for a large US manufacturer who is working on a new battery monitor. His exact words were;

"I've yet to test any 24, 27 or 31 battery that has delivered it's Ah rating. This is a real stumbling block we are trying to over come in the learning algorithm. We are being forced to do this to avoid the inaccuracies of unquantified owner programmed ampere hour data."

If a Group 24, 27 or 31 is all you can fit you really can't go wrong with US Battery Trojan or Crown. If you can fit a taller battery, go with a battery designed from the ground up for cycling purposes. It will cost less over the long haul.

For a good read look up Trojans responses to USB's rather inflated marketing claims...:laugh

Both Trojan and East Penn are quite a bit more honest in their lab cycle claims than USB (USB still builds a good battery). All battery makers are a bit sleazy, as is the BCI, who has whole heatedly resisted any sort of PSOC ratings, fair cycle-life ratings or honest labeling practices in regards to cycling batteries. It's no wonder because the BCI is driven by the battery industry. Sadly the EU has eclipsed the US in more equitable battery testing data. Until the industry becomes honest about their ratings we have to learn to wade through the bovine dung.

The fact that a battery lasted "9 years" is actually rather meaningless unless we know what its Ah capacity was along the way. I can point to many auto type batteries that have lasted 10+ years, if I completely ignore actual end of life Ah capacity. With light loads, shore power most of the time and pretty much constant float life even an automotive type battery can easily last 9 years. By industry standards it has likely been dead for a while but under light loads they can certainly last beyond the 80% end of life industry recommendation. Problem is that once below about 80% of "Ah rating" I start to get more messages and texts like this one I got a few weeks ago..



Everything is a compromise and fitment is one of those compromises because builders have forced us, through molded trays etc., to use batteries that are not well suited for the usage we are often doing. Tied dockside most of the time, these batteries do okay. Put your boat on a mooring, like most of the North East and the Maritimes, and these batteries simply don't match the performance a GC 6V or 12V or industrial type battery in terms of longevity.
 
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