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Rechargable battery problem

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gary350

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I have a 1.2 volt 1.3ah rechargeable battery. If I put the battery on charge I often realize a week later I forgot to turn it off. The battery has gotten so it needs to stay on the charger all the time to be charged. When I use the battery is seems like it has a full charge but it is dead in only a few minutes. If I remove the battery from the charger and do not use it, it will be dead on its own in a very short time. This is my 3rd new battery. I think maybe a week on the charger is screwing up the new battery? I can't remember how many times I forgot to turn off the battery and it charged for 1 or 2 weeks.

I never know how much power is left in the new battery so there is no way to know how long it needs to be charged?

Maybe a 1 hour time would work to turn the charger off when I forget to turn it off but is 1 hour the correct charge time?

And automatic circuit that keeps the battery from over charging would be best?

I am open for suggestions.
 
Without knowing the rating of the charger, type of battery, rough guess of what the battery is powering, hard....impossible to say much other than guessing you're charging a NiCad or NiMH battery wayyyy too fast/hard/long with whatever you're using to charge it.
 
Without knowing the rating of the charger, type of battery, rough guess of what the battery is powering, hard....impossible to say much other than guessing you're charging a NiCad or NiMH battery wayyyy too fast/hard/long with whatever you're using to charge it.


It is a nickel cadmium battery KR-1300SC 1.2v 1300mah = 1.3ah

It came with its own battery charger, input ac 110v-120v 60hz. output 1.25v 170 ma. Open circuit voltage is 3.35 volts.
 
That tells me it shouldn't be on charge for more than about ~10 hours on a totally dead battery.
After that you start roaching the battery.
Probably should change the title of the thread to "Rechargable Battery PEBKAC"
 
That tells me it shouldn't be on charge for more than about ~10 hours on a totally dead battery.
After that you start roaching the battery.
Probably should change the title of the thread to "Rechargable Battery PEBKAC"

The math tells me 1.3 amps / 170ma = 7.64 hours charge time. That is what I learned in college 40 years ago about lead acid batteries not sure that applies to new technology NiCad batteries?

Here is part of the dilemma. I use the battery on the weekend only, about 1 to 2 minutes each time, about 8 times total, on a model airplane glow plug. The glow plug pulls a lot of amps. I don't know the exact amps but what I do know is this, it take 8 D size Duracell alkaline batteries to make the glow plug glow and my VOM show I can get 8 amps from a new D battery. I have tested several alkaline batteries with 3 different meters and I still get 8 amp is the maximum I can get from a D battery. 8x8=64 amps total. 6 D batteries will sometimes work on the glow plug but it does not always last to be used 8 times. 6 D batteries = 48 amps. 4 new D batteries will not work on the glow plug = 32 amps. OK maybe there is something I don't know about batteries, maybe it has to do with the type of battery being used.

YES it would be nice if I knew how many amps it takes to make a glow plug work but I don't.

One thing interesting about batteries I have learned is the old alkaline batteries maximum current is 8 amps and the batteries run down slow. After pulling several heavy loads max amps drops to 7 then 6 then 5 etc until it is dead.

The new technology batteries are different, I can get 60 amps form a batteries and do that over and over several times and still get 60 amps each time on the work bench right to the end. Then without warning the batteries is suddenly dead.

My old batteries is shot, I am going to buy a new NiCad battery it is 1.43 volts and comes with its own charger. I don't want to over charge it but I don't know how to do that since I have no clue how much power remains in the battery after I use it several times. Maybe I should run the battery dead with a light bulb then recharge the battery with a timer.
 
[quote Maybe I should run the battery dead with a light bulb.quote]

Hi

Don't do that. That will really ruin the battery as a Nicad should not go below 1v per cell when fully discharged.

Regards,
tvtech
 
There are a ton of cheap little chargers out there for rechargeable batteries that don't work well. I used to have the same problem with my camera batteries. The safest way might be to plug it into a 10 hour timer, at least that would limit the overcharge. My new camera has a Lipo battery so it has a "real" charger. You might think about Lipo. The batteries and charger are more expensive, but D cells that are bad after a few months are to.

Hmm. Maybe?

https://www.dynamiterc.com/Products/Default.aspx?ProdID=DYN1926
 
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When continuously over-charged, an old Ni-Cad battery cell develops spikes of conductive material inside that pierce the insulation which shorts and quickly discharges the cell. A modern Ni-MH cell does not develop those spikes but also should not be over-charged.

54 years ago I used a #6 dry cell (it was huge and heavy) to heat my glow plugs. Now my RC airplanes are electric and are powered by modern Li-Po batteries that also must never be over-charged.
You cannot use a Lithium battery because one cell is 3.2V to 4.2V. You need 1.2V to 1.5V for a glow plug.

Today people are running around "smoking" a vaporizer that has its glow plug heated with a lithium battery, not an old Ni-Cad.
 
The math tells me 1.3 amps / 170ma = 7.64 hours charge time. That is what I learned in college 40 years ago about lead acid batteries not sure that applies to new technology NiCad batteries?
Ahhh...an RC glow plug battery charger. I gotcha. I'm in that boat myself, 'cept I haven't burnt out a battery yet :) I've worn a few out over the years, frozen a few, ran over a few, but not burnt them out due to an overcharge.

Also true, that's what the math tells you, but I've always gone by the +25% "rule" and it's worked for me so far, since about '88 or so. Add that 25% and you get ~9.55 hours. 1-2 weeks...ooofff...not good.

The cheapo glow plug chargers aren't much more than a transformer, rectifier, a current limit resistor. Don't know exactly how they spec the one you've got, but let's assume it's 170mA short circuit and 3.35v open circuit.
In theory, that's a 19.7 ohm resistor in series with the output. At the start of the charge, you're getting the full 170mA, assuming the NiCad is still good, it'll come up to 1.2v fairly quickly. 3.35v - 1.2v = 2.15v. 2.15v / 19.7ohm = ~110mA charge rate. Later in the charge, the battery is actually at about 1.4v. 3.35v -1.4v = 1.95v. 1.95v / 19.7ohm = ~100mA charge rate.
When the battery is fully charged, it'll have a voltage across it of about 1.5v. 3.35v - 1.5v = 1.85v. 1.85v / 19.7ohm = ~93mA charge rate.
So, as you can see, even with a fully charged NiCad in there, the charger is still trying to push about ~93mA across it. That's less than C/10 for the battery, but still pretty far above the rate at which it can stand to be continuously on charge, and as noted in the technical desciption above, they'll start killing themselves.

Here is part of the dilemma. I use the battery on the weekend only, about 1 to 2 minutes each time, about 8 times total, on a model airplane glow plug.....(snip).....OK maybe there is something I don't know about batteries, maybe it has to do with the type of battery being used.
No, I think you got a pretty good handle on batteries, just maybe not so much the way they get charged up.

Batteries have 'internal resistance' which is what limits their ability to dump current. Alkaline batteries have a high internal resistance, meaning you can only get X amperage out of them. NiCads, NiMH batts, etc. have a very low internal resistance (good batts anyways) meaning you can really pull a lot of amps out of them. Connect a bunch of alkalines in parallel, you effectively lower the resistance and increase the amperage you can get from a bunch. So, you've got the right idea as far as alkalines go, just not so much the reasons why. (P.S. Lead Acid batteries act much the same as alkaline batteries as far as discharge voltage curves go)

Also, alkaline batteries have a very soft voltage drop off when they're getting discharged. NiCad, NiMH, have a very sharp dropoff. In other words, if you've got a light bulb hooked up to 2 batts, 1 alkaline, 1 NiCad and, all other things being equal, watch the lights as the battery goes flat, the alkaline light bulb will slowly dim out, whereas the NiCad will almost shut off like a switch was thrown.

The new technology batteries are different, I can get 60 amps form a batteries and do that over and over several times and still get 60 amps each time on the work bench right to the end. Then without warning the batteries is suddenly dead.
...which flows right along with the sharp voltage drop off of NiCads.

My old batteries is shot, I am going to buy a new NiCad battery it is 1.43 volts and comes with its own charger. I don't want to over charge it but I don't know how to do that since I have no clue how much power remains in the battery after I use it several times. Maybe I should run the battery dead with a light bulb then recharge the battery with a timer.
I've been doing good with the old school wall wart battery chargers on my glow plug lighters, but then again haven't left them on for days on end. There are 'smart chargers' out there for the glow plug lighters. They're a bit spendy, but how much more than a new set of plug lighters? I dunno...
 
Gary 350

Nickel cadmium batteries like to have a heavy load put on them. Good ones can take a 10 times capacity load (10C) but for only approximately 6 minutes before they are completely discarded. Therefore, your 1.3 Amp/Hr. battery will produce 13 amps for only 5-6 theoretical minutes. This is not counting loss in wiring etc. Note: A 14 gauge would be necessary to carry this high a load. To carry 64 amps would require car booster size wires. I suspect that your 8 Alkaline batteries, wired in parallel, are only putting out approximately 2 amps each when connected to the glow plug.

Suggestion: Try adding a DC 20 amp meter between your battery and the glow plug. When the glow plug is glowing the right color, note the number of Amps the meter is showing. I would guess that you will see about 5 to 6 amps flowing. To make it easier on the battery try using a 5 amp/hr D sized Nickle Cadmium (Ni-CD ) battery. These are readily available on Ebay for about $5 apiece.

Charging: Ni-CD like to be charged at the Capacity divided by 10 rate for 12 to 14 hours (C/10). Good sealed Ni-CD batteries have a built in self production system where when fully charged they will absorb the excess charge and dissipate the excess as heat. Above the C/10 rate Ni-CD batteries will decompose the water in the battery when they have reached full charge, they are in effect being cooked. The excess gasses will be vented (hydrogen and oxygen) and the life of the battery will be shortened. Prolonged cooking above the C/10 rate will dry out the battery and it will not function as a rechargeable electrochemical system.

To prevent cooking the battery recharge it at a rate that is below the C/10 rate. I recharge my Ni-CD batteries at the C/20 to C/30 rate. So even when I forget to take them off of charge and they have been charging for a week or more, no real damage is done to the sealed battery because of the built in self protection system.

Life: Most modern sealed Ni-CD batteries last between 3 to 7 years whether they are discharged (used) or just left on the shelf. Good Ni-CD batteries can be recharged between 300 to 1000 times under ideal conditions (not too heavy a discharge load, recharged at the C/10 rate, keep at room temperatures especially during recharging and discharging, and the cutoff voltage is keep above 1.0 volt. However, even if your Ni-CD batteries only give you 200 cycles they are a great deal. The cost is only 2.5 cents per charge/discharge cycle.

To prolong the life of your Ni-CD batteries, I suggest a recharger that will cut down the rate of recharge when the battery is fully charged to what is called a trickle rate. The trickle rate will not harm the battery and will ensure that you have a fully charged battery whenever you need to use it.
 
It is a nickel cadmium battery KR-1300SC 1.2v 1300mah = 1.3ah

It came with its own battery charger, input ac 110v-120v 60hz. output 1.25v 170 ma. Open circuit voltage is 3.35 volts.

I would put a 10 or 15 Ohm Resistor, between your charger and the battery to Lower the charge current.
This should Stop it from Over Chaging your battery.
 
I might consider a better charger: https://www.batteryspace.com/singlecellchargerseriesfornimhnicdbatteries.aspx

You also might want to read info at www.batteryuniversity.com

At a minimum, if you have a timer, use it.

NiCd's like to be discharged at least periodically. They also like to develop dendrites or shunts. If you catch the battery early, the shunts can be removed. I take a big cap (220 to 1000 uf) and charge it to about 30V. Then discharge it into the battery. Then I measure the battery voltage, I keep repeating until there is no improvement and then recharge.
 
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