Battery Mistake

Over a year ago I purchaed a marine battery and was using it last summer to power my CPAP machine on camping outings, etc. Over the summer I
typically was recharging it just by hooking it up while driving and had no problems. Over the winter I took it out of the car and kept it in the garage. In anticipation for a camping trip in a few weeks I went and bought a 1 amp battery charger to charge it back up to full power rather then just using the car as I did last summer. I must have been half asleep when I connected the charger but the next morning when I went to check on it, I realized that hooked it up backwards... Am I going to need to buy a new Marine Battery or are battery chargers today smart enough to not do anything when hooked up backwards? I didn't want to hook it up the correct way in fear of blowing the thing up or something, but I'm wondering what is my best course of action?
Sincerly,
Matt
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Battery chargers normally have protection against reverse connection, as otherwise it is the charger which is likely to go up in smoke. What is the battery voltage now?
--
Andrew Gabriel

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summer
bought
just
anything
best
A one amp charger? I doubt that will be enough to charge the battery to full power. I use 1-5 amp chargers to keep the charge in batteries.

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...
If the battery has been ruined, no harm will come from trying to charge it. It just won't work is all. The charger will sit there poking charge into it forever, but the battery will never be able to hold the charge. Depending on what is wrong with it, there may be no charge current, maximum (i.e., 1 Amp) current, or it will appear to be charged, the current will go down and the voltage will look normal, and it just won't last for the rated discharge (e.g., an 8 amp hour battery might go dead in only 1 hour with a 1 amp load, instead of lasting 8 hours).

The difference is how much time it takes to bring it to a full charge. If you have a 5 amp charger the initial charge will be at 5 amps, while with a 1 amp charger it will be at 1 amp. Obviously it will take more than 5 times as long for the 1 amp charger to put in enough charge to reduce the charge current to less than 1 amp, but in either case that will happen if all goes right.
Meaning that will happen if the battery can be fully charged, and if the size of the battery is such that at "full charge" the voltage the charger supplies will result in less than 1 amp of charge current. I'm not actually sure what that is for average sized car or marine batteries, but I would assume that for typical batteries in decent condition it would be less than 1 amp.
I used 1 Amp trickle chargers instead of battery heaters when I lived near Fairbanks. That had the added advantage of being quite sure the battery was always topped off.
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summer
bought
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anything
best
It will most likely recover. Get a bigger charger such as a 10 amp type.
Next time buy a Deep Discharge. It will have a longer life for your application.
http://www.batteryfaq.org
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If you blew anything up, it was probably the charger. What I'd do is to check the electrolyte level in the battery and top off with distilled water, then let the battery sit, not connected to anything, for 24 hours. Measure the battery voltage with a digital voltmeter. If it's around 12.60 volts, the battery is pretty close to fully charged; if it's less than that down to about 12.00 volts, the battery is discharged but may recover; if it's much less than 12.00 volts, the battery is probably bad.
If the voltage is 12.00 volts or above, hook up the charger (the right way) and plug the charger into the wall. Check the voltage at the battery terminals again. If it's gone up from your initial reading, the charger is at least trying to work, but if it hasn't changed or has gone down, the charger is probably bad. If you need a new charger, I would recommend a 6 to 10 amp "automatic" charger that shuts itself off when the battery is fully charged. Most cheap 1 amp chargers require a manual shutoff.
If your charger is working, let it charge the battery for 6 hours and then go listen to the battery. If you hear bubbling sounds, it's done charging, but if you hear nothing, keep charging. It may take as long as 3 days (72 hours) to charge it with a 1 amp charger if it was fully discharged. When you disconnect the charger, unplug it from the wall first and then disconnect it from the battery to avoid sparks.
After you charge it, you will probably want to test the battery. Figure out how much current your CPAP machine draws, and come up with an equivalent load: an 1156 car tail light bulb draws about 2 amps, most car headlight bulbs draw 4 to 5 amps, etc. Connect enough bulbs to the battery to draw the same amount of current as your CPAP machine. Let them burn for an hour, then disconnect the bulbs and measure the battery voltage. Hook the bulbs back up, let them burn for another hour, disconnect and measure again, etc. When the voltage gets down to 12.00 V, the battery is fully discharged. If the time it took to fully discharge is acceptable to you, then you're set (after you recharge the battery). If the time wasn't long enough, you need a new or bigger battery.
If you don't want to do all this, many auto parts stores will test batteries for free, but understand that they do this in hopes of selling you a new battery.
For lots more details, the already mentioned site http://www.batteryfaq.org / is recommended.
Matt Roberds
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snipped-for-privacy@worldnet.att.net wrote:

Not all of that is good advice, though I can see where you are coming from. Lets look at it though, one item at a time.
Do *not* add water until the battery has been recharged, unless it is actually below the low marker. If the battery actually is discharged, charging it is going to change the electrolyte level. Ideally water should not be added *except* when the battery is fully charged. And then, ideally, the battery should be subjected to a fairly good discharge and recharge cycle. (Actually it should be given a "boost" or "equalize" charge, but a couple of discharge and recharge cycles will have the same effect.)
There is no point in waiting 24 hours *before* charging. You want to wait 1 to 24 hours *after* charging, to see what the voltage is at that point. It should still be close to 12.6 volts. If it drops to 12.0 volts in 24 hours *without* a load connected, the battery may at or near the end of its useful life. (Or... it may have been seriously discharged, and need to be cycled a few times!)
The advice about voltage is half right. If the voltage is 12.60, it is fully charged, and if it is 12.00 it is probably just fine, and is about 25% charged. Voltages below 12 volts do *not* mean the battery is necessarily bad. The battery is considered "fully discharged" at anything below 10.5 volts. And certainly discharging lower than 10.5 volts (despite what several people have said in this thread) *will* shorten the useful life of the battery. Automotive type lead acid batteries are *not* designed for deep discharge cycles, and even the 10.5 volts that I'm specifying as "discharged" is lower than they are intended to go on a regular basis. The typical duty cycle should be no lower than about 20% charge, which is somewhere between 11.2 volts and 11.9 volts.
But lets face it, we've all left the car lights on now and then and ended up with a battery so dead that it wouldn't even keep the clock running! I guarantee that was a lot lower than 10 volts! Do that too many times, and yes the battery dies. Or do it to a four year old battery that is supposed to last 5 years, and it won't. But once, to a new battery, won't kill it on the spot.
Note that the 12.0 for "full discharge" figure relates to the ability of a battery to supply "cold cranking power", i.e., to supply cranking amperage while maintaining a voltage high enough for an ignition system to function. It has significance for engine starting applications, but otherwise it doesn't. The 10.5 volt value is the right figure for batteries where the discharge will be a relatively steady discharge current for a long period of time, as opposed to a very high current than cannot be maintained due to reasons other than charge state (such as heat generation).
The real question is whether the battery can be recharged to 12.6 volts and then maintain that voltage for a few hours without a load. However, fully charging a completely discharged battery is not necessarily as simple as connecting up a charger and waiting. There are "smart chargers" that can do it. Also a 1 or 2 amp charger will likely do it, though obviously very slowly. Anything faster will appear to have fully charged the battery, but actually will have charged only the electrolyte in close proximity to the plates, and as it sits it will "discharge" as the electrolyte equalizes through out each cell. It may take several attempts with a "fast" charger to actually fully recharge the battery.

That is good advice, except that is what should be done regardless of what the voltage is. And check the charger the easy way... scrape one clamp on the other and see if it sparks. :-)
If it sparks, the charger is almost (but not quite) certainly good. The chances it isn't aren't worth worrying about at that point.

One of the significant *advantages* of a 1 amp charger is that it does *not* shutoff! The problem is with the typical 6-10 amp chargers, because they can't regulate down to a trickle charge and therefore *must* be shut off. Ideally, you want one of each, because they serve very different purposes. The 6-10 charger can top off a partially discharged battery fast. If you have a "dead battery" that won't quite turn over an engine and need the fastest safe recharge, that's the right size (or maybe up to 15 amps, but not more). Also, for batteries kept on a "float charge", which might be exactly what a 1 amp charger does, they need to have an equalize charge applied about once a year to make sure the battery is "desulfated" completely. For that a voltage that is above the "gassing voltage" is needed.
But if you want to leave a battery sitting for weeks or months at a time, and want it ready to go... put a 1 amp charger on it. Likewise if you live where it is cold enough to require pre-heating the engine, a 1 amp trickle charger on the battery will keep it topped off and warm too. Ideally this will result in just about a 13.2 volt charge voltage. Higher will cause an overcharge, and lower won't keep that battery fully charged.
The other advantage of the 1 amp charger is as noted previously, it won't give a false indication of a fully charged battery, because the electrolyte will have time to migrate inside the cell.

I wouldn't put my ear close enough to a battery to listen for bubbling! But that *is* an accurate way to judge charging... assuming the charge rate isn't so high that it is overheating the electrolyte, which can happen.
If it isn't a clear plastic case that you can see through, bubbling just isn't of much interest. If you can see it, it has entertainment value, but not much else... :-)
It will bubble more when the applied voltage is above the "gassing" voltage, which is something over 14 volts. The charger won't provide that much voltage until the battery is very close to being fully charged.

Extremely *good* advice.
Particularly if the battery turns out to be in poor condition, it is possible that it has been sitting there bubbling hydrogen, and in a under the right circumstances it makes a wonderful bomb.

Again, 12.0 volts is *not* a discharged battery. However, it is a rough marker for where it should *not* be 24 hours after a full charge if there is no load on it.
The best way to load test a battery is at about 5% of the rated amp hour capacity. If you have a 100 amp-hour battery, put a 5 amp load on it, and discharge it down to 11.5 volts.

I didn't find that web page to be exceptionally good, simply because it deal *only* with engine starting battery applications. It certainly has a great deal of very good information though.
http://www.amplepower.com/primer/testbat / http://www.yuasabatteries.com/motor_battery.asp
Neither of those is any better or worse than the above URL, but it pretty much takes reading all of those and maybe two or three others to get a full picture of what is going on with lead acid cell batteries.
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Floyd L. Davidson <http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@barrow.com
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My advice comes from having been asked to work on a lot of batteries "cold" with no history on the battery and sometimes not even a complaint of it not working. Checking the electrolyte as a first step immediately shows if there is a possible leak in the case, if the battery has been maintained at all, if some creative person has put corn flakes in the cells, etc. Also, it's something you can usually do with no tools except maybe a screwdriver.

Surface charge. I said to wait 24 hours before measuring as that's the "no tools" way to get rid of the surface charge.

This is a better criteria for deep-cycle use instead of starting use. However, given the application, it might be smart to be somewhat conservative with the battery.

Not always. Some chargers won't apply voltage to the battery leads until they see some minimum voltage present on the leads. These won't spark when you scrape the clips together, even if the charger is perfectly fine.

If you sell batteries, this is indeed an advantage. A non-shutoff 1 amp charger is a great way to boil your battery dry if you're not careful.

At work I use an automatic 10 amp charger that is at least 10 years old. It starts out at a max 10 amp charge, and tapers down. When the battery voltage rises to a certain point, it will switch off the charge current. If you leave the battery connected, the current will switch off and on (as shown on the internal ammeter and verified by an external ammeter) so as not to overcharge the battery.
I agree that an inexpensive 6 to 10 amp charger will typically only drop to around 2 amps when the battery is fully charged, and that you can't leave the battery connected to such a charger for a long time once the current has dropped to that level.

I agree that putting a charger on an idle battery is a good idea. However, a cheap 1 amp non-shutoff charger is a bad idea. Using something like a Deltran "Battery Tender" or a Schumacher "Battery Companion" charger will work a lot better. If I had to maintain an idle battery with a 1 amp non-shutoff charger, I might try putting the charger on a lamp timer, to only turn it on for a few hours each day. This is not great, but it's better than letting it boil the battery 24/7.

Again, it's something you can do with the tools most people have.
Now, I did give voltage readings to two decimal places, which implies a digital multimeter, which seems to violate the "no tools" theme. However, I feel that if you're going to be fooling around with a battery, especially one that is powering medical equipment, a digital multimeter would be a smart item to have around.
Matt Roberds
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A charger like one of these are adequate for normal deep discharge use:
http://www.batterychargers.com/details.cfm?prodid=SE%2D520MA&catid 
http://www.batterychargers.com/details.cfm?prodid=SE%2D1275A&catid 
Similar house brand versions are available at WalMart.
For even better results get a three stage charger.
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snipped-for-privacy@worldnet.att.net wrote:

I'll repeat that then: *do not add water* before charging *unless* it is actually below the low water mark. What you recommended was to top it off, regardless, before charging. That is asking for a messy acid spill.

You didn't mention charging first and then waiting. You just said to wait 24 hours. There's no point...

The point is, the battery is *not* dead at 12.0 volts, which you said it was. 12.0 might still be the lowest voltage the OP would normally want to discharge to, but the battery is *not* dead at that voltage.

With a 1 Amp trickle charger it isn't going to boil your battery dry. A 6 or 10 Amp charger might, but a 1 Amp charger won't.

The point is that you are using a "smart charger", and I was *not* referring to that, but specifically to "a typical 6-10 amp charger", which won't do what your's does.

A 1 amp charger is a good idea. It isn't the "best" way, just the least expensive why to get good results. Of course one can spend a *lot* more money...

But despite the cost, the results aren't significantly better.
(Note that I'm talking about matching the size of the charger to the size of the battery. If the battery is, for example, a small motorcycle battery, that 1 Amp charger *will* cook it.)

Definitely agree on that. A good digital meter is relatively inexpensive and well worth owning.
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Matthew E wrote:

If anything "cooked" as a result of the backwards hookup, it was probably the charger. Many have answered you on that - and you are probably confused by all those answers.
I will address a different point: you can damage a battery by leaving it uncharged. Batteries in storage will sulfate, unless they are kept "up to snuff" by a periodic charge or by being stored on a float charger. If they sulfate enough, a hard crystaline coating can build up on the plates that charging, including "equilazation" charging, cannot remove. There is a permanent loss of capacity if that happens.
Ed
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Lead acid cells are also damaged by discharging to something less than about 20% of capacity. Hence while "cooked" might not be a good description, it is not correct to suggest that the battery would not be damaged. It certainly would be.
And if it is 3-4 years old already, it might well be damaged enough that its useful life is done.

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Floyd L. Davidson wrote:

You see a suggestion where none exists. But set that aside. I agree that hooking up a charger backwards might damage a battery.
You say certainly. Why are you *certain*? I can see cooking the charge controller circuitry (if there is any - this charger might be nothing more than a transformer and a diode for all we know) by a backwards hookup. But where is the low resistance, high (relatively) current path to discharge the battery in ~ 12 hours that you have in mind? I have a hard time imagining a circuit in his one amp charger that would draw much. If the thing has a V sampler across the battery, and it goes dead short, the battery will cook that short into nonexistance real quick. If you get a high resistance short of say 100 ohms, it'll draw 120 mA. 12 hours later, it has used 1.44 amp hours. Mind you, I'm not saying it could *never* happen, but you are *certain* that it would, so I'm puzzled.
In any event, we agree that a battery discharged too far damages it.

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Your right I am confused. I must apologize for not responding sooner to all the reply's. Thank you! After seeing the post regarding checking the fluid levels, etc. I realize that I forgot to mention that the battery is sealed. A Deep Cycle Marine Battery. I bought the 1 amp charger which has an automatic shutoff because it said it was made for deep cycle batteries. If i did fry the charger, which it sounds like might have happened then I will go and get a higher amperage one per the suggestions. I need to buy a multimeter so I can check the voltage level. The battery is going to be pretty critical for me in two weeks when we do go camping because I found that the rustic campground we are going to will not have power and I need a source for my CPAP, otherwise no one in the campground will be sleeping those nights! Me and my girlfriend are actually going to the Renewable Enery Fair in Custer, WI. I appreciate all the help you guys have given. I am actually planning on going back to college this fall after a Hiatus of 10+ years (I'm 28) out of school for electrical engineering, which was why I chose this forum to post to.
Thanks
Matthew

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An automatic shutoff on a 1 Amp charger is... sort of a waste if you are using a battery of any significant size. What's the rated capacity of your battery.

I doubt you would have hurt the charger. It has current limiting, which would pretty much have prevented any damage.
Given the use you have indicated, you *don't* want a high amperage charger. Though a 2 Amp might be better, if this battery is roughly equivalent to a typical car battery.

Keep in mind that only a digital meter is accurate enough.

Great... but tell us how you make out with this battery! We'll be mildly interested if you get a PhD in two years... but we're all just sitting on the edge of our chairs waiting to know if you battery is okay, of your charger is okay, or just what! ;-)
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The charger does actually do 2 amps as well, so I will try that. Off on another tangent, If I get a digital multilmeter I'd like to get something of quality and that will be useful going into school, but at the same time I don't want to buy something that will be overshadowed by the equipment that I will probably be using in the school lab this fall. Any suggestions? My girlfriend will be down this weekend, so I'm not sure how much of a chance I'll get to work on it ;)

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The problem is that it will not charge at 2 amps as the battery becomes charged. It may take hundreds of hours to get a full charge and an equalization charge will be impossible.
Personally, unless it is for a home hobby, I would not invest a lot in a multimeter. Doubtful that it will be of any use for school.

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Fairly good digital voltmeters aren't terribly expensive. Fluke is pretty much the standard, though other companies make good ones too.
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You can get a pretty good charger at WalMart. Be sure to get one with a Deep Discharge setting. Something in the 10 to 12 ampere range will be adequate. It will aid in keeping the battery from sulfating. As I said if you get a new battery, get a deep discharge. It is built for deeper discharges than the Marine type and usually has more capacity for the size. A Marine battery should not be discharged below 50% state of charge whereas a Deep Discharge is designed for as low as 20% at lower currents.
Look for the Ampere Hour rating.
Other considerations are weight and how you are going to store it. Does it need to be a sealed battery or are caps ok? For my RV I use two 6 volt golf cart batteries in series to obtain up to 220 ampere hours of use. But they are heavy. Advantage of batteries with cells is that you can check their state of charge with a hydrometer. Testing with a volt meter needs to be done with a very accurate volt meter and having removed any surface charge. To removed the surface charge you must let it set for several hours after charging or apply a load for a few minutes.

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Does it say "sealed - maintenance free" on it somewhere? It is indeed easy to get such a battery, but it is also easy to get a battery that is sold as "low maintenance" and has non-obvious caps to remove to check the electrolyte levels. Don't tear up the top of the battery looking for a cap to pry off, but take a look at it.

You might talk to the solar and wind energy people about batteries. I hear they use one or two of them and they will probably have some good advice. You might also want to read http://www.tinaja.com/glib/energfun.pdf before you go.

[in a later post]

If cost is no object, buy a Fluke meter, probably a 170 series. It has a lifetime warranty and you'll probably lose it (or someone will steal it) before you break it. The middle option is a Fluke 12, which doesn't have a lifetime warranty or current-measuring ranges, but is also pretty bulletproof. The inexpensive option would be one of the imported meters. I have had reasonable luck with Metex and A.W. Sperry meters. Of the two, I like the Metex a little better because it uses fuses that are easier to get ahold of. I think the batteryfaq website has some specifications you should look for when you're shopping for a meter to test batteries with.
As to what you will have at school, it's a toss-up. From what I have seen, you will either have nice high-end meters, or really cheap and nasty disposable meters, with no in-betweens.
If the only thing you'll have to measure is your marine battery, you might consider buying an inexpensive panel meter and permanently attaching it to the battery - that way you can check the battery anytime. Something like http://www.allelectronics.com/cgi-bin/category.cgi?category85&item=PM-21&type=store with a 9-volt battery to power the panel meter will cost you maybe $15 all told. You might put a switch or a pushbutton in the wire to the 9 V battery so the meter doesn't run all the time.
Matt Roberds
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