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Battery charging

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cwstrang
1st Mate

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USA
78 Posts

Initially Posted - 06/14/2010 : 07:49:16

Guys:
I spent Sunday afternoon on board working my steering conversion and while working had my Ipod plugged into my radio listening to my favorite tunes just loud enough not to annoy my neighbors. About 3 hours of playing I noticed the volume decreasing and the panel on the front of the radio was dim. Seems like two batteries should be able to play the radio for days, my question is how can I check the charging system as I have a small solar panel connected to the batteries. The boat is a 2004 and I am not sure if the batteries are original.

This too many large trees floating down the Columbia to venture out.

Edited by - on

JohnMD
Navigator

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USA
207 Posts

Response Posted - 06/14/2010 : 08:13:26

This is a great article.

http://www.solar-electric.com/deep_cycle_batteries/deep_cycle_battery_faq.htm

If your batteries are more than a couple of years old, IMHO, they're probably trash. Old batteries that haven't been taken care of will sometimes charge ok, but, they won't hold it very long. Do yourself a favor and get a battery maintainer (also called a smart charger). Keep your batteries charged all the time. A solar charger won't do that. (Tho they are helpful when you're out sailing). You can't let a battery sit around in a discharged state without damage occurring.

Edited by - on

OLarryR
Master Marine Consultant

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USA
3439 Posts

Response Posted - 06/14/2010 : 08:51:12

Sounds like you have a number of issues:

1) How to check out the battery voltage/charge ?
2) How old are the batteries ?
3) Size of the solar collector and how that factors in with what you can/cannot do ?

If you have a fishfinder, it is possible that it has a mode that indicates the battery voltage. If not, then you will need a voltmeter to check the battery voltage and that can give an idea as to the charge left. It will at least tell you if the batteries are dead. if the voltage has dropped to somethuing below 12 volts, then they are basically gone. A good battery should have voltage in the range of 12.8 - 13.3 volts. Once it drops below that, then it is not holding a full charge or is not fully charged. There is a chart with the various voltages that a number of us have restated in these postings but I don't have the time right now to give any more than the above. I'll leave it to others.

2) Well...obviously the older the battery, the more likely that it will not hold a charge and will need to be replaced. But I have flooded batteries charged only by a solar collector and were at least a year old when I purchased my boat back in 2005. These batteries are still holding their charge with a resting voltage of 13 - 13.2 and no issues starting the outboard. So...I guess the question is how old are your batteries and if they are the flooded type, have you been checking and refilling the water periodically.

3) The minimum solar panel for just trickle charging one battery is 5 watts. A 5 watt solar panel would not need a controller because it will not do much more than make up for the charge lost daily (summer and winter) and may not depending on it's efficiency and location even keep up with the trickle charging. For 2 batteries, then figure on at least 10 watts. If you have a 10 watt panel or not much more than that, then it will only trickle charge the batteries and not make up for any electrical loads like playing a radio or using the lights at night. What has worked for me and I would say it is the minimum one should have is a 20 watt panel with a solar controller for 2 batteries. That handles the trickle charging and just a bit more for say using the lights at night once a week. Any more use than that, then one would have to go for a larger solar panel. My controller also reads out battery voltage that is being charged, the stand alone battery voltage with no charging and the battery voltage when being charged by the outboard. Having a controller with readouts also helps to manage the electrical load/maintain fully charged batteries. You can tell from the battery voltage and also for the LEDs when the battery is fully charged. Without some way to gage some sense of this, you then do not have an idea if your panel is handling the load nor if your batteries have lost their capability to hold a charge.

Edited by - OLarryR on 06/14/2010 08:56:39

JohnMD
Navigator

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USA
207 Posts

Response Posted - 06/14/2010 : 09:50:18

I live in sunny north Texas. I bought a 15 watt solar panel and a controller thinking I could keep 1 battery charged by using just solar. NOT. My battery had absolutely no load on it, not even a volt meter and it died after just one year. If you think about it, you have times when it's cloudy for a few days if not weeks at a time. So what, your battery voltage goes down to 12 volts during that time. Bad, bad, bad for a battery. Even if it has enough voltage to start the engine (and charge the batteries back up), that process just kills the batteries. As I said, do yourself a favor and get a system that will KEEP your batteries charged.

Also remember, the 15 or 20 or whatever watt output is when the sun is directly overhead and there are no clouds. What is that, about 2 or three hours a day???

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 06/14/2010 : 10:06:35

I'm not sure how helpful this is, but as an experiment this weekend, I ran my Waeco fridge all weekend to see how the batteries would fair. I have an 18 watt (I think?) solar panel connected to a charge controller, and no other charging available unless the engine's running (it wasn't). The Waeco has low voltage detection, so it'll shut itself off at some break point that I'm not sure of (it's in the manual, I just don't remember). I also have two virtually brand new batteries. By yesterday afternoon, my charge was down to 12.6 roughly, just enough to bump it up over the "green" light in my cheapo Walmart battery meter. That's not bad for a weekend of use, and admittedly it was just the fridge running, but it was a pretty constant load the whole weekend.

Judging from what you've said, your batteries are probably past their use-by date and should be replaced. I agree with your original assessment, they should be able to run your radio all weekend without a hiccup. For comparison, my Sony boombox ran most of the weekend on it's C batteries without a hiccup.

Edited by - on

cwstrang
1st Mate

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USA
78 Posts

Response Posted - 06/14/2010 : 10:29:53

Thanks for the input thus far, I didn't install the solar panel as it was on the boat when I bought it last May. I think I do have a manual on it and will check to see if it is a 5w or 10-15w panel. Our Oregon winters have many many days without sun.

Edited by - on

Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 06/14/2010 : 12:45:26

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by cwstrang
 ... Our Oregon winters have many many days without sun.
<hr height="1" noshade id="quote"></blockquote id="quote">
As do our springs.

I installed a digital voltmeter so we can check the batteries easily.

I have also seen inexpensive meters that plug right into a cigarette lighter of you have a 12V plug already in the boat.

Edited by - on

OLarryR
Master Marine Consultant

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3439 Posts

Response Posted - 06/14/2010 : 12:54:05

John,

You obviously have had a bad experience with a solar panel. I am not exactly sure why you only got one year out of the battery. Maybe you had more than your share of cloudy weather or perhaps you had an inefficient panel or maybe your battery had a bad cell.

There are different types of solar panels. The least expensive ones are generally a larger footprint for the watts they put out and if you were to block off just a small area of the panel with a finger, the panel puts out zippo. The same source you provided a link to - Northern Arizona Wind and Sun is where I obtained my Kyocera solar panel. It is just 14"x20" rigid panel rated at 20 watts and is made with multi-crystal cells vs mono cell structure. This panel even on sale is not cheap - It is selling right now on sale for $184.

For me this is a no brainer. My marina charges extra for electricity. Boats my size, it cost $20/mo for dockside electricity. I have never paid the monthly charge and I have never brought my 2 batteries home and I sail all year. I use my batteries occasionally for nav lights and all the time for the fishfinder. My outboard (12 AMP charger) is mostly used only to get in and out of the marina which is about 10 minutes max and only once in awhile will I run it for longer than that for the times I get stuck out with no wind. If I stay overnight at another marina, I will usually pay for the electricty during that stayover and I have a smart charger installed and it comes on automatically if I hook up to shore power - but during the past years, I have only used dockside electricity 1 or 2 times. That's it ! and my batteries right now are a minimum 5 1/2 years old.

So....something doesn't add up regarding your 1 year battery life. Given your experience and seem very set against solar power....I agree going with a Smart battery charger is the way to go.

Edited by - on

jbkayaker
Captain

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USA
299 Posts

Response Posted - 06/14/2010 : 18:53:52

Spend some time at this website and you can learn a lot about batteries.
http://www.batteryuniversity.com/

Edited by - on

DaveR
Master Marine Consultant

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USA
2015 Posts

Response Posted - 06/15/2010 : 06:55:58

Battery issues were really getting on my nerves a couple years ago so I took Larry's advice and visited [url="http://store.solar-electric.com/"]Northern Arizona Wind and Sun[/url], where I found a 45 watt solar panel on sale and also bought the same controller he has and haven't had a problem since. There's some cost to this but no matter what you're doing with this boat that's something you need. I did do one more thing. I switched my CD/Stereo so I could turn off the back light when I wasn't using it.

Edited by - on

OLarryR
Master Marine Consultant

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USA
3439 Posts

Response Posted - 06/15/2010 : 08:17:25

Dave - Every so often I consider getting a 30 watt. Recalling your 45 watt doesn't help the situation.

Interesting thing you mentioned about turning off the backlight. I have a mini-boombox. I think it uses 4 C cells (but I can also hook it up to my DC power with an adapter). I normally use rechargeables in the radio but they were always going dead so soon. What I found was that something is drawing electricity within it. What I do now is I remove one battery from the radio to break the circuit and then re-install it when I use the radio. Now I get much longer life out of the rechargeables.

Edited by - on

Voyager
Master Marine Consultant

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Response Posted - 06/16/2010 : 18:48:31

Battery life is all about your checklist:
1. Maintain your battery fluid level - ONLY USE DISTILLED WATER, NEVER TAP WATER TO TOP IT OFF
2. Know your battery's charge level. The chart for Group 24 wet cells is

Charge at 14.4V until 90% then revert to 13.6V

Once the charger has been off the battery for a while, the measured values should be:

12.6V - 100% of charge - 75 Amp-Hours remain
12.4V - 75% of charge - 56 Amp-Hours remain
12.2V - 50% of charge - 38 Amp-Hours remain
this is as low as you should let your battery go . . . .
12.0V - 25% of charge - 19 AH remain
you better recharge the battery quick!

3. The battery should not be left at 1/2 or lower charge without recharging.

I have two 20W solar panels and no shore power. Even at 1/2 power for 8 hours a day, they still deliver 1 Amp or 8 Amp-Hours combined on cloudy days.

If my battery is 1/2-way discharged, I need to replace 38 Amp Hours. At 1 Amp for 8 hours a day, I need about 5 days to fully recharge the battery.

4. Never let your battery remain discharged for any length of time, as the lead plates will get sulfated. This creates a coating that limits the charging ability of the lead plates. Once the battery plates become even partially sulfated, the effective amount of charge becomes limited.

For example, a 75 Amp-Hour battery can become capable of only 45-50 A-H, so the battery will only hold a charge for a short time.

You can estimate whether your battery has sulfated. Make sure your battery is fully charged at 12.6 volts, then take a 1 Amp load (like a fan or light) and let it run for 20 hours. If you battery has 75 Amp-Hours, the voltage after 20 hours should read about 12.4 volts after you let it settle for a while.

If it reads substantially less than that (like 12.2V) then your battery has seen better days.

At that point, it's time to recycle your battery!

Edited by - Voyager on 06/16/2010 18:57:07

Stinkpotter
Master Marine Consultant

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Djibouti
9075 Posts

Response Posted - 06/16/2010 : 21:14:41

...and if it's a standard wet-cell and loses electrolyte, either it's being charged with too much voltage, or some plates have become deformed such that there is arcing between them. Either generates hydrogen and oxygen gas (not just steam), which is not a good combination to accumulate in a closed compartment. If the electrolyte level drops below the tops of the plates in less than two years, distilled water is a temporary solution, but it's time for a new battery.

Edited by - on

Navy1
Navigator

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USA
126 Posts

Response Posted - 06/20/2010 : 07:23:04

Randy, Where can you get one of those battery meters you mentioned that you can plug into a cigarette lighter socket? Thanks - Roger

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 06/20/2010 : 08:54:04

Roger, I found mine in the car parts section of Walmart. About $15 I think.

Edited by - on

islander
Master Marine Consultant

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USA
4018 Posts

Response Posted - 06/20/2010 : 10:05:59

An inexpensive plug in volt meter is the very least you should have. Without a volt meter you are just guessing as to how much charge you have or if your solar panel is doing anything at all to recharge the battery's. Yes small solar panels don't require a charge controller but without one you cant tell if the panel is working or not. I have a 10 watt panel with an inexpensive charge controller and the plug in volt meter. This is very low end set up but in combination with the outboard is serving my one 7yr old group 27/90amp battery just fine. Are all your battery connections clean ? Water level OK? This is a deep cycle battery and not a car starting battery I hope. Heres a link for the plug in volt meter I use. Very accurate and is made well.http://www.amazon.com/Vector-VEC008-Digital-Voltmeter-Volt/dp/B0002ISEQW

Edited by - on

TakeFive
Master Marine Consultant

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Response Posted - 06/20/2010 : 13:57:11

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by delliottg
 Roger, I found mine in the car parts section of Walmart. About $15 I think.
<hr height="1" noshade id="quote"></blockquote id="quote">
I just bought one yesterday at Walmart. I had to look around for quite awhile to find it. It was next to their battery display, tucked in with the battery cables. Also about $15.

FYI, this is the one. Obviously it's available at Amazon also:

http://www.amazon.com/Equus-3721-Battery-Charging-Monitor/dp/B000EVWDU0
<center>

</center>

NOTE: This picture is not fully accurate. The meter actually displays two decimal precision.

Edited by - TakeFive on 06/20/2010 20:10:47

TakeFive
Master Marine Consultant

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Response Posted - 06/20/2010 : 20:09:23

I tried out my new voltage meter this evening, and it was right at 13.6v while charging (my two-stage charger had been running for over 24 hours since our last sail), and after a few minutes settled down to 12.6v after I turned off the charger.

But as soon as I turned on the cabin light and/or the stereo, voltage dropped immediately to the 12.2v range. Aside from running a device of known wattage for a measured period of time and measuring the amp-hours (or watt-hours) to drain to the 50% point, are there any charts that show how the type 24 battery should perform under load? In other words, if you take a fully charged battery putting out 12.6 v across a virtully open circuit (only load is the volt meter itself) and connect a device that draws a certain number of amps, how much should a healthy battery's voltage drop while it is under load?

And one other question: I bought an 18w solar cell/controller off of the Woot website. I did it on a lark (thanks to a suggestion posted here), and have not used it yet. I realize that the controller is not the greatest one in the world (no numeric LCD display), but it's better than nothing. When I leave the dock my battery is always fully charged thanks to the 2-stage 120v charger. Is there a danger of my outboard's alternator overcharging the battery? If so, would running the alternator wires through the solar panel controller help prevent overcharging? (I realize that there is a possibility that the alternator could put out too many amps for the controller to handle, so I'd check that out carefully before trying this.) Any thoughts on this?

Edited by - TakeFive on 06/21/2010 04:55:41

OLarryR
Master Marine Consultant

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Response Posted - 06/21/2010 : 03:48:41

I don't know the answer to your question except that if you really want to know how well the battery can handle a load, bringing your battery into an auto store that gives free battery checks, their equipment is designed to simulate putting a substantial load on the battery and is setup to then indicate if the battery is satisfactory or is something less than that.

When we use the standing voltage it is only to get a sense of battery performance and as you know...not with a load on it. But based on what is normally considered acceptable for standing voltage..at 12.6 Volts, Voyager's chart he provided would indicate the battery is at 100% capacity. There are a number of charts put out by different sources and they all mirror similar to what Voyager provided...but again it is only a guide and not measuring with a load on the battery. Even so...a 12 volt battery that is in good shape will measure standing voltage 12.6 volts or above. But many 12 volt batteries at 100% capacity will have standing voltages of 12.9 to 13.2 volts or perhaps .1 or .2 higher than that. It varies with each battery and type. But at 12.6 volts, while it indicates battery has sufficient capacity...since anything below that is indicating the battery is losing it's charge, I would think that the condition of your battery is that it's starting to lose it's charge. Also, when you indicate standing voltage, I forget just how long one should wait before taking that reading. For example, if you take the standing voltage an hour after charging the battery versus taking the voltage reading the next day after it has been recharged, you may find the standing voltage has dropped a bit. I would go by the standing voltage that you get the next day and not relatively soon after having it was recharged. If you get 12.6 volts the day following the recharge, then I would say your battery is okay for now. But if you measure something less than 12.6 volts the following day...then your battery is weak. Going by Voyager's chart, 12.6 volts or above it's 100% capacity but a really good battery would be well above 12.6 volts. If after a day, you drop down just .2 volts, then you have lost at least 25% capacity which is significant. I guess the point I'm trying to make is that you took the standing reading shortly after a recharge. That is similar to when my solar panel stops charging and perhaps an hour later my standing battery voltage reads about 13.2 volts on a flooded battery but the next day before the solar panel kicks in, it reads a standing voltage of 12.9 volts --- Still 100% capacity. But your 12.6 volts is likely a bit lower if you were to take the standing voltage the next day and that is the reading I would go by....otherwise...bring your battery into an auto store to really find out the story.

Edited by - OLarryR on 06/21/2010 03:54:26

John Russell
Master Marine Consultant

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Response Posted - 06/21/2010 : 05:00:12

If you were to leave the solenoid switch for the propane stove on for an entire week, you could sufficiently drain your battery so that it won't even pretend to crank the motor, or turn on the radio, or lights, or..... Ooops.

Edited by - on

Voyager
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Response Posted - 06/21/2010 : 19:25:31

Rick, you brought up several good points that Larry answered reasonably.

Let me address two however:
1. "as soon as I turned on the cabin light and/or the stereo, voltage dropped immediately to the 12.2v range."

This voltage drop is due to the "internal resistance" or R(i) of the battery. The usable "terminal voltage" from a battery is a combination of the unloaded or open circuit voltage minus the voltage drop caused by R(i) x the current draw.

Assuming your one cabin light uses 12 Watts, that would take about 1A. Your radio probably idles (on but not cranked) around 1-2 Amps. Let's assume a total of 2 Amps.

Doing the math using Ohm's Law: Voltage = Current x Resistance. In this case (really Kirchoff's Law):

V(open circuit) - V (voltage drop) = Terminal voltage or
12.6 - R(i) x 2A = 12.2, so R(i) = 0.2 Ohms.

If this is true, your short circuit current (don't try this at home kids) is probably around 60A. If you took 1/2 that amount of current (30A) to start your engine, you'd have 6V terminal voltage for the starter, which is lower than usual. I estimate my starting voltage to be about 9-10 Volts at 30A, so my internal resistance is about 0.1 Ohm.

On this basis, I'd suspect your battery is weak. The internal resistance is a good indicator.

2. Solar regulator - You could over-voltage your battery using a 20W solar cell without a regulator in the circuit. Typically these simple regulators measure the voltage of your battery, and when it gets up to about 13.4-13.6V, it cuts the circuit - it basically disconnects the solar panel - thus "regulating" the charging circuit. It's a simple one-step charger. These regulators are typically capable of handling 6-8 Amps.

Your plug-in charger is probably at least a two-stage charger which charges at a higher voltage when the battery is low, then as the charging current reduces as the battery reaches toward full charge, it cuts back the charging voltage to around 13.4V.

Your engine's alternator should have its own built-in regulator which should prevent over-charging or over-voltage, unless it was damaged (as mine was). If the alternator regulator fails as mine did, it supplied the battery with upwards of 15.5 or more volts. This will tend to boil off the acid, and you will smell the odor of rotten eggs in the battery compartment. If the alternator is OK, it too will have at least a two-stage regulator, if not a three stage.

If you decided to use the solar panel regulator, there are two problems with that. If your alternator puts out more than 6-8 Amps (mine can generate 12A), you will overwhelm the regulator. As well, an alternator regulator works entirely differently than a solar panel regulator. To regulate, the solar panel regulator simply disconnects the solar panel from the battery. That's no problem for a solar panel.

If, on the other hand, you disconnected an alternator suddenly from the battery (as the solar regulator would do), the surge produced by the alternator would instantly burn out the engine's regulator circuit and rectifying diodes, so you would end up doing a lot of damage to the alternator, regulator, or both.

Edited by - Voyager on 06/21/2010 19:35:52

TakeFive
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Response Posted - 06/21/2010 : 19:50:51

Bruce,

Thanks for the detailed response. I'm an R&D engineer, and I'm still up enough on my freshman Physics to understand everything you said.

The idea about the solar panel regulator was just sort of a "what if" thing, not to be taken seriously. But overwhelming the regulator was exactly what I thought might happen. I haven't checked the specs recently, but I think my 2000 Honda electric start version has a 9 or 12 amp alternator.

The maintentance-free battery in the boat came with it when I bought it in March, and the battery is less than a year old. The previous owner showed me a receipt for it from WM. He made a big deal about how he kept it on a trickle charger all winter, so it would be very disappointing if it is weak after such a short time. I have two type 24 batteries on trickle in the basement, both 10 years old, and both are still very serviceable on my power boat. But of course you never really drain down power boat batteries because the motor is running all the time.

Unfortunately the previous owner couldn't seem to do anything right with this boat (aside from sell it to me

), so I would not be surprised if he boiled off some of the acid. FYI, I have never had any H2S odors in my boat, so I doubt I'm boiling anything off. And I would smell it, since I have no ventilation when the boat is closed up. (For now, I'm using a small dehumidifier to knock down the moisture.)

Next time I go to the boat I'm going to turn off the charger for 24 hours and see where the voltage lands. After that I'll probably run several cabin lights of known wattage for a period of time to see how much capacity is in there. Then I'll consider trading in if I have to.

Edited by - on

TakeFive
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Response Posted - 06/22/2010 : 19:09:55

I went down to the boat today and disconnected the negative terminal. Then I noticed that the battery box was cracked, so I pulled it completely out and brought it home. I was wrong - it is not maintenance free, so I popped the caps off the cells. There appears to be plenty of electrolyte. I did not have a hygrometer to test it, but I will stick a volt meter on it tomorrow to see how it reads.

One thing I noticed was a whole bunch of baking soda in the bottom of the battery box. What's with that? Is there some trick I don't know about? I guess it neutralizes any acid that splashes out the vents so that it's less corrosive if it comes in contact with something? I also saw a little on top of the battery which I was not crazy about because of the possibility of dissolving in stray acid and washing back into the cells to contaminate them. My first fear was that it might be peroxide, but it became pretty clear it was baking soda from the "fizzies" it made when in contact with the acid.

Edited by - TakeFive on 06/23/2010 05:55:16

JohnMD
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207 Posts

Response Posted - 06/23/2010 : 06:49:20

When I was a kid, people would put baking soda in a flooded battery thinking it would clean the sulfation off the plates and restore or extent the life of a battery. It was supposed to milk a few more months out of a dead battery. (The answer is no, and unicorns don't exist either).

Edited by - on

TakeFive
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Response Posted - 06/23/2010 : 07:16:58

After sitting overnight in the garage, voltage tested at 12.7. So while it's not over 13v like some of you say, it is above the 12.6 spec. Now that I have it in a more accessible place, I'll run some carefully timed load tests with an ammeter in line to see if it meets its capacity spec.

Edited by - on

Voyager
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Response Posted - 06/23/2010 : 14:31:43

If the battery settled back to 12.7 after 12 hours off the charger, that means it's fully charged, holding a charge and reading to spec. That is a good initial sign.

Your next steps would be to set up a 5 amp load and let it run for 4 hours (20AH). Then, disconnect the load, and let the battery rest for about an hour, then measure the open circuit voltage. If it reads between 12.45 to 12.5V, the battery is still very good.

If it's down to around 12.2V and stays there, then its possible the battery will still work for the season, but its days are numbered.

If instead the voltage sits below 12V, time for another battery.

Edited by - Voyager on 06/23/2010 14:33:10

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.