Backup power

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While trying to come up with something more to worry about, I thought of my backup battery. I have a 12 v deep discharge lead acid battery with a Battery Tender wall wart charger. I check the battery water level monthly (usually) and keep an eye on the charger indicator light. I see no problems but wonder if there was an easy way to be sure the battery will be charged when the power goes out and I need it for a light and, if summer, a fan. Just trust the charger to detect a problem and warn me by changing the light color or blinking? An easy test of some sort, other than turning the light and fan on for a half day or so every few months? I suspect I'll just have to take my chances.
TIA
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On 11/26/2014 9:30 AM, KenK wrote:

My experience, is that a Harbor Freight float charger will "boil" the battery dry, and kill it. I'd suggest to put your float charger on a lamp timer, and only run the charger an hour or so a day. Or once a week for a couple hours.
You can get a hydrometer, from the auto parts store, if you want some thing else to check.
The real life action test is the only way to know. I'd also use a volt meter, and do some research online. A lead acid battery won't recover from a total discharge, there is some voltage not to go below that point.
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I have a solar charger going set at 13.8 volts with temperature monitoring. I checked the cells, and still see correct levels. It's been going for two years. It's probably best to discharge at intervals to equalize the cells.
The hf float charger does deliver too much current as you say.
Greg
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On 11/26/2014 08:30 AM, KenK wrote:

1) You should not be charging a "wet" type lead acid battery in-doors, the hydrogen emission is explosive. The type of battery you should be using in your house would be VLRA. (Valve regulated lead acid.)
2) Since most people ignore my first point when I warn them, the type of charger you use /can/ make a difference. Ideally you'd want to employ hysteresis-loop charing techniques. This type of charger only charges between preset voltage ranges and minimizes water consumption and maximizes battery life. You are unlikely to find such a charger in the "consumer" market...so the next best thing is a "float" charger which will retain a constant voltage just below the battery's gassing point. What you do not want is a "trickle" charger. That type simply puts out an /unregulated/ small amount of current.
3) There are testers that can check a battery's internal resistance without actually putting a load on it. They are fairly reliable but the only sure way is to actually load it down. A reasonable test would be to simply place a heavier than usual load on it for a relatively short period of time and check the voltage drop. If the battery can stay above 11 volts under a heavy load it's probably fine.
Additionally: If you do insist on using a "wet" type battery my advice would be to /not/ keep it on charge. Unless there is a load on it, it may only require a "top off" every three months or so. The charging area should be well vented.
My credentials:
I worked for Enersys as a Senior Service Engineer & retired after 38 years. Many a time have I seen exploded batteries and I did so myself exactly once.
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On 11/26/2014 10:00 AM, philo wrote:

The one exploded battery I've known in person was an old farmer trying to start a Gehl Skid Steer. He had the battery on 12 volt boost. He went to adjust the battery clamps with the charger still on / plugged in. I was on the other side of the machine, but I remember his words "get some water for my eyes".
The Op's float charger won't make enough hydrogen to do that.
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KenK wrote:

Hi, First if the battery is indoor, do you have good ventilation for it? I'd buy or build solar panel based smart charger.
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good point about indoors vs outdoors. I had a battery explode INSIDE my car's engine compartment. I stupidly left the contacts loose and enough gas enough spark and the battery became non-existant with acid washing the interior of the engine compartment!
Why not on a really small trickle charge say 100mA, or 10mA, or 1mA, or whatever it takes to sustain the voltage? ignoring temperature.
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On 11/26/2014 10:19 AM, RobertMacy wrote:

The problem with a trickle charger is that it simply puts out a small but unregulated amount of current. In the probable event that it's output would be slightly higher than the battery's idle discharge rate, the voltage could go above the battery gassing point. Not only will this use up water, it will be putting out hydrogen.
Plus, if the battery was discharged, a trickle charger would take "forever" to recharge the battery.
Most chargers are regulated to prevent excess gassing and some are even adjustable.
Except for all the batteries that I have in UPS's I never keep any of my extra batteries on charge. They are kept in a cool location and some are only "topped off" twice a year.
I have a couple of rarely used 6V gel cells that are over 20 years old. One is low capacity but usable but the other still has decent capacity.
Had the batteries been kept on float charge they would not have lasted more than 4 or 5 years.
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know in advance the battery will go bad over time, most lead acid cells only last 4 or 5 years, even marine batteries
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On 11/26/2014 09:30 AM, KenK wrote:

> http://www.iotaengineering.com/pplib/spec2.pdf
And add the IQ4 smart-charge module.
Connect an el-cheapo multimeter (Hazard Fraught or the like) across the terminals (permanently) but turn it on only to check the voltage from time to time.
Perce
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Percival P. Cassidy wrote:

Hi, EVen bad battery gives good voltage reading. When Load is applied nothing!
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On 11/26/2014 2:31 PM, Tony Hwang wrote:

I can't think of anything (worth the cost) that's easier to do or more accurate. Does the battery do what you want when you ask it to do that? Test doesn't get more relevant than that.
Never ask a question if the answer won't change the future. In this case, if you run some "test", what are you gonna do with the answer?
If the light doesn't work, you have a clear definitive answer and you know exactly what to do...go buy a new battery.
I suspect I'll

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On Wednesday, November 26, 2014 10:00:42 PM UTC-5, mike wrote:

Yes that's the best test. But the only way he'll know that is to put his load on it and see if it lasts the expected number of hours. I guess doing that once a year isn't a bad idea. But if you do it regularly, every cycle takes more life out of the battery. A battery tester can test it with a short duration load.

Presumably he'd replace the battery if it's no longer adequate.

Only if the light doesn't work after X hours. A mostly bad battery could still light up the light for a brief test and he wouldn't know if it was capable of going the normal length of time in an outage.
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On 11/27/2014 12:42 PM, trader_4 wrote:

I can't say you're wrong...just that you're overthinking it. We don't know the whole story, and you can come up with a counterexample to prove any definitive statement wrong.
I believe there are battery testers that can tell you a lot about the condition of a battery, but are they "worth the cost" in this situation.
Applying some logic...
What is "no longer adequate"? What's the calamity that ensues if the light lasts x-1 hours? x-2 hours? x-3 hours? At what point does the cost of some possible future calamity exceed the current cost of a new battery?
If it's a life-support situation, you replace the battery on a schedule and have an additional battery on standby.
If you used the system frequently, you wouldn't need to test it. In particular, a yearly test suggests that it's more than a year between power outages.
What's the cost, in additional battery degradation due to discharge, of 20 partial discharges over the next 20 years? You don't need to run it flat to learn that it's degrading. Measure the voltage, under load, after an hour and graph the number.
And the system test is of the whole system including source, load, wiring, switches, etc.
I have a UPS on my computer. The battery is not new. Runs for about 5 minutes.
Power outages around here are of two types. Virtually all last less than a second. The rest last for hours.
Replacing the battery with one that runs 10x as long would be of zero benefit.
My first line of defense in a power outage is the nap. Nothing fixes a power outage faster than a long nap.
Second line is two dozen harbor freight free flashlights.
Next is the 12V battery-in-a-box car starting gizmo. Then the car battery. Then the 500W generator. Then, if it's cold and I need to keep the pipes from freezing, I need to run the furnace off the 2KW generator. Then, if I need to power my neighbor's freezers to keep his food from spoiling, I run the 6KW generator.
Can't remember the last time I needed more than the nap and one flashlight. My only excuse is that I acquired all this stuff over 40 years at pennies on the dollar.
Managing expectations is far easier than obsessing over attempting to maintain your full existence during a power outage.
Harbor Freight will sell you a generator for $67 after 25% coupon that will provide REAL backup power if ever needed. And that's probably in line with what you'd pay for a new battery.
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On 11/27/2014 6:43 PM, mike wrote:

Ah, bother. Just got off the phone. My train of thought is off in space. I'll write later.
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On Thursday, November 27, 2014 6:43:40 PM UTC-5, mike wrote:

All I can do is give options that answer the question. IDK what the value is to the OP of being able to test his battery. It's up to him to figure that out and how much a battery tester would cost and how a battery tester fits his requirements versus the putting it through a full cycle test periodically method. There are also options from buying a new battery tester to buying a used one on Ebay. Presumably, the OP, if interested, can research that and figure it out. Someone even pointed out that some multimeters have a battery load test function. I've never seen one, but if they do, then maybe he doesn't have a multimeter, could use one for other purposes too, and that option would work for him.
As to overthinking it, IDK exactly what you mean. You suggested that the best way to test it is to actually make it do what you expect it to do, periodically. All I did was point out that to do that, you'd have to put it through a typical full usage cycle, or at least close to it, and that each time you do that, it lessens the life of the battery. I also said if you do that once a year or so, and that's adequate, it should be fine.

We don't know because that was never given. What the parameters are and how you can test to those parameters are two different things.

And I'm the one that's overthinking things?

That's what a battery tester will do in seconds. Maybe he wants to buy one of those instead? Anything wrong with that?

The rest of the system can be checked with high accuracy in just a few seconds, by turning it on. That isn't the case with a battery, unless you have a load tester.

Irrelevant because your requirements and priorities <> OP or others.

And I thought the question was about how to test a battery.....
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On Wed, 26 Nov 2014 10:12:49 -0500, Stormin Mormon

So how WERE his eyes?

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On 11/26/2014 6:53 PM, micky wrote:

Quite endangered. We went into the house, he rinsed with water, and a pinch of baking soda. Refused medical care, ambulance, etc.
No lasting damage to my knowledge.
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You need to use a meter with a *battery voltage* setting for each voltage battery. They have a built-in load. (They also have voltage settings for use when not measuring batteries.) .
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micky wrote:

Hi, That is battery checker they use at the garage. El Cheapo multimeter is just a meter.
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