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Old 07-03-2020, 07:13 PM   #1
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12-Volt Battery(s) Usage-time help?

Here is the battery (two used in-line):


Fully-charged / After 10-minutes of use:
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Old 07-03-2020, 07:31 PM   #2
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Is there a question or point being.made here?
3.5AH is this for a flashlight?
Under 12V hardly full charged?
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Old 07-03-2020, 07:33 PM   #3
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what are you trying to run
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Old 07-03-2020, 08:05 PM   #4
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This batteries spec say it will put out 3.5 amps for 1 hour from a full charge. Most Lead acid batteries don't like to be drawn down past 50% so if you are wanting to protect longevity it is only good for 1.75 amps for 1 hour. Two in parallel would be double that. A full charge should show 12.7 volts on your meter under no load. 11.75 volts indicates a battery that is near 50% depleted already. If this as good as it get this battery is toast. I have no idea what your actual question is but hopefully this will help.
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Old 07-03-2020, 08:45 PM   #5
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Seeing a precipitous drop in terminal voltage can mean a lot of different things.

"Two used in-line" - series or parallel?

What's your load current? Even small batteries like these are spec'd at C/20, for a 3.5Ah battery that would be 175mA. C/5 (700mA) would be about the most you can realistically expect from these but with a pretty severe reduction in capacity.

What was used to charge them and what assurance do you have that they started out at 100%? Did this ever work before or is this a new issue? How old are these batteries?

Mark B.
Albuquerque, NM
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Old 07-04-2020, 07:00 PM   #6
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Quote:
Originally Posted by Reka View Post
what are you trying to run
The device:
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Old 07-04-2020, 07:02 PM   #7
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Is there a question or point being.made here?
3.5AH is this for a flashlight?
Under 12V hardly full charged?
I am wanting to know/learn if this an acceptable operation of these batteries?
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Old 07-04-2020, 07:07 PM   #8
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Originally Posted by Mark_K5LXP View Post
Seeing a precipitous drop in terminal voltage can mean a lot of different things.

"Two used in-line" - series or parallel?
>>>Powering 24-volts.

What's your load current? Even small batteries like these are spec'd at C/20, for a 3.5Ah battery that would be 175mA. C/5 (700mA) would be about the most you can realistically expect from these but with a pretty severe reduction in capacity.
>>>Does the inserted picture help answer this?

What was used to charge them and what assurance do you have that they started out at 100%? Did this ever work before or is this a new issue? How old are these batteries?
>>>I purchased these to replace old batteries.

Mark B.
Albuquerque, NM
>>>Helpful?<<<
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Old 07-05-2020, 01:36 PM   #9
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First observation is your "fully charged" voltage is actually near dead if that's open circuit voltage. So I'd be looking at your charger, charge connections and make sure it's actually completing. Then, verifying your batteries are actually full at that point. As an aside I'd check the date code on these to make sure they're not some stale/old stock that was sold as new.

Mark B.
Albuquerque, NM
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Old 07-05-2020, 04:05 PM   #10
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Originally Posted by Mark_K5LXP View Post
First observation is your "fully charged" voltage is actually near dead if that's open circuit voltage. So I'd be looking at your charger, charge connections and make sure it's actually completing. Then, verifying your batteries are actually full at that point. As an aside I'd check the date code on these to make sure they're not some stale/old stock that was sold as new.

Mark B.
Albuquerque, NM
Not something I considered. Off to acquire a replacement charger. Thanks!
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Old 07-06-2020, 04:09 PM   #11
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Not something I considered. Off to acquire a replacement charger. Thanks!
Ordered... Stay tuned!


https://www.searspartsdirect.com/pro...-240/id-300023
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Old 07-06-2020, 04:27 PM   #12
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Your device uses 24v @4.6a but those batteries are 2x 12v@3.5a or if in series to get the voltage needed for the device 24v@3.5a. So these batteries are not big enough to run this device for very long.
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Old 07-06-2020, 05:55 PM   #13
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Your device uses 24v @4.6a but those batteries are 2x 12v@3.5a or if in series to get the voltage needed for the device 24v@3.5a. So these batteries are not big enough to run this device for very long.
So... Are you stating although the total output of two batteries is 24-volts, that 3.5-amps remain the same?
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Old 07-07-2020, 07:13 AM   #14
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The Ah rating isn't a maximum current, it's just the capacity at a given discharge rate. Discharge it faster and you get less capacity depending on a few factors but if the capacity you get at that rate is sufficient for the application, then it will work just fine.

Most smaller gel cells like this are spec'd down to the 1 hour rate and will come in at nominally 1/2 the 20C capacity depending on what the voltage cutoff spec is. They are also spec'd well above the rated capacity for peak currents. So this little battery could source 40 or 50A (for some number of seconds) if you need it to. Something like the weed whacker here could be drawing 5 amps plus at 24V (~1/6 HP) which would bring the battery down in half an hour but that might be all the operating time you need out of it. Before the advent of low impedance and relatively inexpensive lithium batteries, lead acid and nicad/NiMH were the only games in town for power tools and they got thrashed mercilessly in that service. Abusing the batteries and shortening their lives was an acceptable tradeoff to the utility the tools provided. If one really wanted to, a retrofit lithium battery could be fabricated for this unit that would be double the capacity and half the weight. Most folks just buy a new tool with a new battery but I have a hard time throwing away working tools, so I keep cobbling together battery packs and running them as long as they'll go.

Mark B.
Albuquerque, NM
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