Golf cart batteries

[foggysail]

I mentioned that my old heavy batteries were into their seventh year, to me they lasted that length of time. They provided the service I needed for that time. Therefore in my application, they lived nearly a seven year life.

Now of course, battery status is correctly determined by measuring its specific gravity, corrected for temperature and its state of charge can then be determined by comparing the specific gravity to a charge chart. Those old batteries of mine probably had a capacity of well over 200 ampere hours when new. That degraded over time, much so as a cell in each battery became sulfated preventing it from accepting a full charge.

The old batteries are history, long live the new batteries! As long as they provide my needed service, that will determine their life span.

Foggy

[btrayfors]

Originally Posted by foggysail

I mentioned that my old heavy batteries were into their seventh year, to me they lasted that length of time. They provided the service I needed for that time. Therefore in my application, they lived nearly a seven year life.

Now of course, battery status is correctly determined by measuring its specific gravity, corrected for temperature and its state of charge can then be determined by comparing the specific gravity to a charge chart. Those old batteries of mine probably had a capacity of well over 200 ampere hours when new. That degraded over time, much so as a cell in each battery became sulfated preventing it from accepting a full charge.

The old batteries are history, long live the new batteries! As long as they provide my needed service, that will determine their life span.

Foggy

Foggy,

Good luck with your new batteries.

Yes, the specific gravity measurements will tell you the state-of-charge (not "status") of your batteries. They will not tell you anything much about battery capacity, though. Residual battery capacity can best be determined by sophisticated devices which measure internal battery resistance & conductance -- and which cost a bundle of $$$ -- or by a 20-hour test in which a resistive load equal to 1/20 the rated AH capacity of the batteries is conducted, with measurements throughout.

You're correct in thinking that sulfation over time will greatly reduce battery capacity. This is the primary mechanism. But, there are others as well, including physical damage, stratification, contamination, etc.

Best way to ensure a long life for your new batteries is to keep them fully charged as much as possible, use absorption voltages of at least 14.4VDC, and relatively high float voltages, e.g., 13.8VDC. That, with periodic usage (exercising) and infrequent equalization (15.5-16.5VDC for a few hours) will keep 'em going for years.

Bill

[foggysail]

Bill--

I am hoping to get at least 7 years from these new batteries. The others died because my charger took days to replenish their charge. It also could not do equalization as my Xantrex can. I am not a big supporter of Xantrex, they will provide nothing in the way of detailed information on their products if repairs are required. But that is another matter.

A good 3 stage charger with equilization is essential for extended battery life.

Foggy

[cuthbert]

Originally Posted by Don Lucas

The resting voltage thing just seems worthless overall. I need to believe the SOC while using my systems and before leaving the boat.

My 1 year old 460 AH batteries can start at 12.5 resting voltage and low 90% SOC of charge on my monitor and after 45 AH out at 5-6 amps and with the monitor now saying 80-85% SOC, the voltage with be reading 12V. And it reads the same on the panel volt meter and with a hand held.

PS - I acturally have my monitor programed for a 400 AH bank instead of the 460 AH

I agree with your first point, you can find many examples on the internet of graphs showing battery performance under load both charging and discharging.

Your batteries are spot on, 10% useage under load =12V. Here is a link of an interesting article.
http://www.scubaengineer.com/documen...ing_graphs.pdf

The monitor is probably working from variance of 460Ah vs 400Ah.

[btrayfors]

Yes, Foggy, I agree with that!

As you might know, I have been conducting battery tests for almost five years now, after having used marine batteries rather badly for over 30 years!

Because of circumstances (having to leave my boat for upwards of 5 months in the tropics, with a not very reliable "caretaker"), I have managed to kill several banks of Trojan T-105s.....four or six at a time! Very expensive lessons. For a while, I found myself replacing them every year or two.

After "retirement" from overseas govt. work, I found more time to learn about and experiment with batteries....flooded, gels, and AGMs.

Then, beginning 5 years ago I conducted with two colleagues some controlled tests on batteries over a period of 18 months, using some pretty sophisticated test and measurement gear. I also read everything I could find and, wherever possible, tested it against my years of (good and bad) experience plus experiments.

One thing I found was that manufacturers tend to be very conservative about their charging recommendations, probably because of liability concerns but also because I've been told by a couple of reliable sources that these recommendations are often developed by the marketing folks and not by the chemical engineers who design the batteries.

I found that the almost ubiquitous 13.2VDC recommendation for floating flooded batteries is low....much too low. I now float my T-105s (total of 10 of them) at 13.8. On my boat, I also have an automated regime to bounce the six house batteries up to 14.8V every other day for about 30 minutes.

Since starting this over 18 months ago, I've noted a remarkable improvement in the measured capacity of my 6-year old house battery bank (six T-105s). They test like new these days. I've only equalized them twice in the past 6 years. See graph (note that the two new T-105s for the windlass battery are maintained by an Iota DLS-55/IQ4 charger, floating at 13.6VDC and with no equalization).



You can see that the house batteries were losing capacity over time until I bumped up the absorption and float voltages. Thereafter, they regained a lot of capacity.

Bottom line: keep 'em charged, exercise them often, watch the electrolyte level (I use WaterMiser caps on all my T-105s), equalize them once in a while, and be happy :-)

Bill

[btrayfors]

Originally Posted by cuthbert

I agree with your first point, you can find many examples on the internet of graphs showing battery performance under load both charging and discharging.

Your batteries are spot on, 10% useage under load =12V. Here is a link of an interesting article.
http://www.scubaengineer.com/documen...ing_graphs.pdf

The monitor is probably working from variance of 460Ah vs 400Ah.

With respect, I think you're misreading the information in the referenced article.

The OP said he has a 460AH house battery bank, and sees 12.0 volts after taking only 45AH (about 1/10 of capacity) out. That represents a 6AH load over about 9 hours.

Here is graph #2 from the article:



Six amp-hours represents a C/76 discharge rate. If you interpolate between the C/100 and the C/20 curves at the right hand side of the graph, you'll see that a C/76 discharge rate beginning with a fully charged battery would result in voltages above 12.5VDC until the battery was 40% to 50% depleted. But the OP only used 10% of his house battery bank capacity (45AH), so should be seeing voltages at 12.5 or above.

I repeat, based on years of testing and personal experience on my boat, if you're really seeing only 12.0 volts after using 10% of your battery banks' capacity, then you have a problem....either the batteries weren't fully charged to begin with or their capacity has been greatly diminished since new. Or both. Or the battery monitor is misleading you into thinking the batteries are more fully charged than they really are.

Bill

[cuthbert]

Two things,

1) The article I referenced was an example of measuring batteries under load, using only a voltmeter. Rather than "resting", using a battery monitor to track charge/discharge voltages and extrapolating from known initial battery capacity in amp hours.

2) The starting point mentioned was that the batteries had a resting voltage of 12.5V and then after 10% capacity useage under load, they read 12V.


You are probably correct in your summation "the batteries were not fully charged to begin with"

[sailorboy1]

well I'm not the OP and am not really sure I what to keep being told what an idiot I am, but what I said was in various items and for which I will expand and let you all go at it (had a thread last year asking this but it became an expert battle and never go answered):

that at a 90% SOC displayed on my monitor (which I sync's when the acceptance was less than 2 amps so believe they were charged) that with a 6 amp load the voltage would go down to 12 volts overnight with a total amp-hour out of around 60-85

a couple of weeks ago I recorded the resting voltage for a few days and it varied around 12.58 to 12.4 with SOC between 99 and 92%

my batteries have never been less than at 75% charge since I got them last year per the monitor and rarely less than 85%

I don't really understand why the voltage goes down so much during normal use (with my radio, nav and instruments, frig, autopilot running) I use about 7 amps

my SOC and my amp/hrs out on the monitor track each other, just that the voltage is lower during use than I expect

so I wonder if the batteries have anywhere near the capacity they are suppose to have

I wonder if it has anything to do with that they have never been discharged down and then recharged (but they have been below 11.9 volts while under the house loads)

if I leave the boat with the SOC around 90% and the voltage reading 12.2 or less volts or so and come back in a couple of days the voltage will be 12.4+ (confirmed by direct measurement)

what I keep questioning is the 0.1 volt drop of the battery under a 6 amp load people mention, because that isn't what I see; unless my batteries have a problem

so I'm still trying to decide if reading my voltage while the batteries are in use has much meaning, or whether it is telling me my batteries don't have rated capacity (from the start), and that resting voltage verse charge seems useless once starting up the systems except for knowing where I started

[cuthbert]

Don,

Can you throw out a few more numbers to resolve this.

1) What is your AC (shore power) charger voltage measured output when initially charging and when fully charged when measured at the same point, with the same meters as the resting/load values.
2) What are the same numbers measured at the same points when the engine is running at something above idle.
3) Do you have anything else connected that can be affecting the measurements such as
a) A solar panel providing a small current into the batteries (and hence a voltage that may be affecting charging devices or
b) A small load that is affecting the "resting" voltage value. Typically the FM Stereo and possibly the VHF radio may be taking a very very small current via a direct connection all the time to maintain presets.

[sailorboy1]

I never have my boat connected to shore power. The only charging is via the engine. When I run the engine at medium load with the baterries at 85% SOC of charge I will put in about 50-60 amps into the batteries. As the SOC gets to around 95% the amps in will drop to 25-30 amps and once at around 97% or so start dropping more. A few weeks ago I ran the engine until the amps in were less than 2 and synd the monitor. When I came back to the boat I measured the batteries voltage directly and compared it to the monitor and the panel voltmeter and at 97% SOC the voltage was 12.5+V and all reading pretty much agreed. The next morning after about 50 amp-hr out and the SOC still in the 90% voltage was in low 12s and during day while sailing goes lower.

the water level in the batteries is correct

Near as I can tell the batteries charge correctly based on acceptance compared to the amps out and SOC.

I've turned off everything on the boat and turned off the inverter when leaving the boat (the inverter selector switch determines the batteries that get charged). There is a small milli-amp solar panel that will supply the start battery and it seems to work because I can read the voltage difference if I isolate the circuits (I thugh once maybe power was discharging though the panel but it doesn't appear to be)

[btrayfors]

Don,

You're not an idiot and I hope you didn't take that from anything I said.

You have a problem. The voltages you're seeing with a minimim load are too low. Period.

If, indeed, the alternator is the only source of charging for these batteries, then it can be said with some confidence that they are almost NEVER FULLY CHARGED. Forget what the monitor says.

To fully charge flooded batteries takes hours....many hours. Much too long for engine charging unless you're powering somewhere or really like to run your engine for hours on a regular basis. I doubt you do, 'cuz then you'd really be an idiot :-)

You need some additional source of charging to keep those batteries up. Plug into a shore-powered charger or, if that's not possible or convenient, then the only other possibilities are solar panels or a wind generator.

Solar panels are MUCH to be preferred. They're bulletproof and last for 20 years or more, and require no maintenance. Prices have come down recently, and decent controllers can be had for not much money.

Wind generators are much more troublesome, being mechanical with moving parts.

Unfortunately, my friend, if you're on the hook and/or not connected to dock power on a regular basis, you're going to have batteries which are chronically undercharged unless you have solar or wind. No way around that.

And, unfortunately, batteries which are chronically undercharged are going to sulfate quickly, losing capacity almost as you watch them.

One final thought....measure the voltage at the alternator when the batteries are accepting only a few amps...say, less than 10. It could well be that your alternator voltage is too low -- in addition to other things I've mentioned. You should be seeing at least 14.4VDC during most of the charging cycle. Some older alternators with internal regulators are set for 13.8VDC or so....much too low.

FWIW,

Bill

[sailorboy1]

Originally Posted by btrayfors

If, indeed, the alternator is the only source of charging for these batteries, then it can be said with some confidence that they are almost NEVER FULLY CHARGED. Forget what the monitor says.

Even if at least once a month I do in fact motor for hours? (see my thread about a light wind sail). And even if the sometimes I've motored long enough for the batteries to only be accepting less than 2% of rated capacity (was less than 1% a few weeks ago)?

And if they only ever get to to say 95% SOC should that really make that big a difference on a boat only being used on weekends to effect the capacity as much as it seems to?

You know all I want is to keep the beer cold!!! I can live with only getting 4 years out of the batteries because I know I'm not operating them ideally.

[cuthbert]

Understood.

Well to recap, the numbers you are getting are about spot on. 12.5V resting down to 12 under load after approx 10% of theoretical means your batteries are OK.... for now, but a year of not being fully charged may have taken a toll and the best way to find out is to tax them a bit more over a longer duration and see if the discharge rate is linear.

But first charge them up.

Although using alternator to charge the battery is perfectly acceptable for millions of cars and gives typically 4 years of battery life, cars get used a lot more than boats and the batteries are discharging constantly even under no load (1-3% a month) you may wish to find a way to get the batteries to a higher % charge and keep it there for longer to get the optimum life from them and get you closer to the theoretical 50% of 460Ah that you could use regularly.


The rest of it is laborious details, but you should into getting a small generator to emulate the shore power and use that before you leave the boat to get it up to 100%. Depending on the regulator that is being used with the alternator when you are reading just 2A running the engine they may well have been some way to go to a full charge (the battery monitor seems to concur). If you don't mind a little noise and unreliability Harbor Freight have a noisy little 900W AC source for $150 and you could bring the batteries back up, but the ideal is a small Honda or Yamaha (much quieter) or go solar.

I would put the solar that you have on the house bank and let the starter sit and just get a charge off the alternator when you run the engine. How big is the present panel? and does it have a regulator (or built in diodes) because otherwise it will discharge when dark.

[sailorboy1]

Originally Posted by btrayfors

One final thought....measure the voltage at the alternator when the batteries are accepting only a few amps...say, less than 10. It could well be that your alternator voltage is too low -- in addition to other things I've mentioned. You should be seeing at least 14.4VDC during most of the charging cycle. Some older alternators with internal regulators are set for 13.8VDC or so....much too low.

FWIW,

Bill

I have a 100 amp balmar alternator with an external regulator. I've never changed the regulator settings but when I did a quick read though of the manual once I think all I can change is the type of battery. I'll look at it again but I think the only way I'm going to get higher voltage is by going to the dock for the day (that will cost a 1/5 of the price of the batteries) or by getting a Honda generator to run my charger (that will cost over twice the cost of the batteries)

[DotDun]

Originally Posted by FlyingCloud1937

As a Trojan dealer, my costs are 110.00 USD for T-105's , so mark-up may play a roll.

Gee.

Lloyd

Southwest Florida retail for T-105's is $86 at a Golf Cart store.