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[How to] Convert Volts to Amps
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me50 Offline

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Post: #11
RE: Convert Volts to Amps
I meant 18 volt battery I'm not going to worry about it anymore though thanks everyone for your help
10-29-2014 05:53 PM
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surferdude2 Offline

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Post: #12
RE: Convert Volts to Amps
me50, Perhaps tell what you are thinking of doing with that power tool battery and we may be able to give you some help. Nobody can tell you what amperage will flow without knowing the amount of resistance in the connected circuit. Keep in mind that if you connect a load that has a much lower resistance than the internal battery resistance, you will see the voltage of the battery drop to a much lower level.

Obviously with no circuit connected you have zero current flowing so you could say that 15 volts equals zero amps unless you connect a load to it.

When you connect a load, the amps will be determined by how much resistance the load has to current flow.

When you finally get some amps flowing through a resistance, you will have transferred power from the battery to the load and it can be measured in watts. Watts is a measure of power.

I doubt the manufacturer will tell you much about the amperehour capacity of that battery since you are using it outside of its intended purpose. You would have to take your own measurements with an ammeter in series with the connected load in order to determine the actual amperage that is flowing.

The power tool battery is designed for a definite purpose and using it elsewise is likely to be disappointing.
10-29-2014 06:10 PM
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me50 Offline

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Post: #13
RE: Convert Volts to Amps
It is being used as intended. I just wanted to see if it had the same amps as the tool it replaced because it was old and is used as a backup
10-29-2014 06:26 PM
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surferdude2 Offline

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Post: #14
RE: Convert Volts to Amps
In that case it should work but if it's old it may not be able to live up to its reputation. My experience with those batteries is that never die completely but just get to where the useful duty cycles is much shorter and recharging is needed more often.
10-29-2014 07:32 PM
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retired_guy Offline

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Post: #15
RE: Convert Volts to Amps
(10-29-2014 03:04 PM)justMongo Wrote:  Wattage is the rate of energy consumption. 1 Watt = 1 Joule/second
Voltage is the electomotive potential. (Think of it like a force)
Amperes is the rate of flow of electrical charge. 1 Ampere = 1 Coulomb/second ( 1 Coulomb = 6.241E18 electrons)

You can have a 12 Volt battery; and open circuit, it flows zero Amperes. Loaded it will flow current (Amperes) depending upon the load.

Two formulas are handy:

Watts = Volts x Amperes (this works for DC, for AC, the cosine between the Voltage and Current must be factored in -- that cosine is called power factor.

And, Volts = Amperes x Resistance (Resistance in measured in Ohms, and is related to the load. -- Again for AC, Reactance must be considered.)

As for the question in the Original Post, it makes no sense it the form the question is cast.

(10-29-2014 04:07 PM)justMongo Wrote:  
(10-29-2014 03:09 PM)me50 Wrote:  I have a power tool that has a 15 volt battery and I want to know how many amps that is

We are all likely familiar with 1.5 Volt Batteries in various sizes. AAA, AA, C and D. Each is bigger physically. If you short circuit any one of these batteries, they can all provide lots of current flow (Amperes.) The larger size will do so longer.

The 15 Volt Power tool battery can supply Amperes depending on tool load. The measure of battery capacity is usually the only other thing we can talk about. Capacity is measured in Ampere-Hours. Let's say it's a fully charged 30 A-Hr battery. In theory, it can supply 1 Amp for 30 hours; or 2 Amps for 15 hours; or 3 Amps for 10 hours... and so on.

So, while we really cannot talk about Amps for a 15 Volt Battery, we can talk about Ampere-Hours. I bet that battery says what A-Hr capacity it has right on it.

Yup. Like I said: Depends on how big your cupcake is.
10-29-2014 07:42 PM
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justMongo Offline

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Post: #16
RE: Convert Volts to Amps
I've gone to Li-ION batteries for my power tools. They are lighter; and like to be kept charged.
NiMH and NiCd are heavier and should be stored discharged. NiCd has "memory effect" -- sort of like R_G -- operates at diminished capacity![Image: jump.gif]

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10-29-2014 08:16 PM
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me50 Offline

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Post: #17
RE: Convert Volts to Amps
(10-29-2014 07:32 PM)surferdude2 Wrote:  In that case it should work but if it's old it may not be able to live up to its reputation. My experience with those batteries is that never die completely but just get to where the useful duty cycles is much shorter and recharging is needed more often.

The older tool is the one that doesn't last as long on the battery and that is why a new one has been bought and that one (a LI-ION) is being used first. While it is charging (it only takes an hour to charge, even for the first use) then I use the older one (not sure what kind of battery it has but it isn't important enough for me to check it out because I have a new one and a back up.

What I was trying to determine is if the first one has the same amps as the older one. It isn't all that important though; it was just something I was curious about.

Thanks for all the responses.
10-29-2014 08:37 PM
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justMongo Offline

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Post: #18
RE: Convert Volts to Amps
(10-29-2014 08:37 PM)me50 Wrote:  The older tool is the one that doesn't last as long on the battery and that is why a new one has been bought and that one (a LI-ION) is being used first. While it is charging (it only takes an hour to charge, even for the first use) then I use the older one (not sure what kind of battery it has but it isn't important enough for me to check it out because I have a new one and a back up.

What I was trying to determine is if the first one has the same amps as the older one. It isn't all that important though; it was just something I was curious about.

Thanks for all the responses.
Make sure the charger is correct for the battery chemistry.
I have some power tool chargers that work for Li-Ion, NiCd and NMHD.
Li-Ion are 3.6 Volts per cell (5 cells for 18 Volts) NiCd and NMHD are 1.2 Volts per cell. Some chargers work only for a specific battery chemistry.

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10-29-2014 08:57 PM
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me50 Offline

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Post: #19
RE: Convert Volts to Amps
the charger came with the power tool
10-30-2014 02:53 AM
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