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.
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.
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.
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.
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.
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.
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.
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.) .
He DID say "battery tender". If it IS a "battery tender" he's OK. If it's a Harbor Fright charger all bets are off. One thing he could do is take the battery to a battery shop and have them test it with a "mid-tronics" type battery analyzer. Noit a load tester, not a voltmeter, - only a "mid-tronics" tester. It will "give the battery it's physical".
I'm talking about a multimeter the size of other multimeters with settings for ohms, DC milliamps up to 10 amps, DC voltage, AC voltage and also battery voltage.
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 know a few people who use IOTA chargers in combination with their IQ4 battery maintainers with positive results. (sorry... could not resist, its' futile.)
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.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.