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Safe range of Volts used for charging


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Topic: Safe range of Volts used for charging

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

Safe range of Volts used for charging

I was wondering what is consided a safe range to charge a visor with. I have the talesafe charger but it does not last long enough. I travel about 50% of the time for my job and sometimes I am gone for a week. I was looking to make a custom battery holder to charge on the road with. The only problem is I dont know what range is consided safe for charging purposes. I was thinking of something with between 6 and 8 batteries so that I dont have to keep changing them out all the time.

Any suggestions?

09-05-2001 03:19 AM

potter
Member

Registered: Feb 2000
Location: SW Virginia
Posts: 290

You want 2.0 Amps at 4.75 to 6.2 Volts DC (ideally 5.9 Volts).

09-05-2001 02:15 PM

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

Ok I know how to regulate the volts, but how do I make sure I only have two amps?

I have an idea in mind, just have to see what the local radio shack has to offer and how best to go about making it. I will give an update later

09-05-2001 06:36 PM

nysebull
Member

Registered: Oct 2000
Location:
Posts: 93

Are you in a car?

If you are traveling in a car, we have a car charger that might help you out.

__________________
Mike

09-05-2001 06:52 PM

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

I wish it was that easy as to take a car. I will be traveling with a backpack and that is about it

09-05-2001 11:28 PM

gadgetguru
Member

Registered: Oct 2000
Location: Arlington, TX
Posts: 334

Brian812,

I have what you are looking for.
I live in Arlington, too! If you want
to meet somewhere on Friday or
Saturday, e-mail me. I am having
surgery (out patient) today. I
can sell you a battery pack charger
for $12 if we meet somewhere, or
$15.50 if you want me to ship it to
you. Let me know!

__________________
Rick

www.visorsolutions.com

09-06-2001 08:03 AM

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

gadgetguru

can you please explain in more detail about it

09-06-2001 01:00 PM

potter
Member

Registered: Feb 2000
Location: SW Virginia
Posts: 290

quote:
Originally posted by Brian812
Ok I know how to regulate the volts, but how do I make sure I only have two amps?

It is not a matter of regulating the amps, but of making sure you can provide at least two amps. (Actually if you do not have a springboard that uses the charging power then only 1.5-amps. The specification is 1.5-amps for the Prism and .5-amps are for a springboard.) You can think about it this way: V = I R, voltage equals current times resistance. The Visor is the resistance. It's value will vary as the Visor's power requirements vary, but will never be a value such that it will draw more than 2-amps (unless something is wrong with the Visor or it's springboard). If the Visor is drawing it's maximum power, then at 6-volts, 2-amps it has a functional resistance of 3-ohms. Lets say you have a power supply that delivers 6-volts at up to 1-amp. If one attaches 3-ohm resistance to a 6-volt, 1-amp power supply, something has got to give. Typical things that may happen, in no particular order:

The voltage drops off such that it is only providing 3-volts (this causes the charging circuit in the Prism to become confused).
Something in the power supply over heats, and burns out (hopefully a fuse) possibly with smoke and fire.
A voltage regulator realizes that the voltage is dropping off, and in defense turns the power supply off.

If you are building your own power supply, it might be a good idea to put in a 2 to 2.5-amp fuse. This just in case something does go wrong with the Visor or springboard that causes it to draw more than 2-amps the fuse will burn out instead of the power supply or the Visor. This is also a good idea in case the power supply connector gets shorted out on something.

09-06-2001 02:48 PM

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

Follow up

Here is what I did. Got a car charger for it then added some pieces. Went to Radio Shack and got the 8AA battery holder as well as some of those 9V connectors. Went to Auto Zone and got a cigarette plug. Then I wired the plug to the 9V connector, so one end of the 9V connector fits on the batter plug and the other is terminated in the cigarette adaptor. Now all I have to do when I travel is use the auto adaptor in the car and then plug in into the battery pack when I need it.

09-13-2001 04:47 AM

gadgetguru
Member

Registered: Oct 2000
Location: Arlington, TX
Posts: 334

I sure hope the cig plug is fused! You are supplying 2x the voltage
suggested for charging the battery in the Prism! You have the capacity
(w/o a fuse in the cig plug) to supply 20 amps to the Prism! If you
smell something funny, IT'S YOUR PRISM! Once you let the smoke out,
it no longer works.

For what you are trying to do, you need a voltage reducer. Your
concoction may work for a while, it may work forever. I would never
subject my Prism to a 12v input with the capability of supplying 20A
of current. You can get a cigarrette lighter adaptor at Wal-Mart for
$15 that converts to 12,9,7.5,6,4.5, and 3v with multiple sizes of
connectors. Then for $13.50 including shipping, you can get my
adaptor to plug into the bottom of the Prism. This will let you
charge in the car or in a hotel room while on a trip.

Please see my web site. Click on "Charge" below.

__________________
Rick

www.visorsolutions.com

09-14-2001 04:46 AM

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

gadgetguru

Is the sig plug fused - Yes
Voltage reducer - Yep got that and I can set it at all the listed you have in your post. Currently set at 6V
Can I produce 20amps? - nope regulated to 3000MA

Got mine at Radio Shack and also got an extension with it. That way I dont have wire getting in my way. I took a little time and ran it behind the dash and only have about 6 inches taht you can see.

09-14-2001 05:11 AM

gadgetguru
Member

Registered: Oct 2000
Location: Arlington, TX
Posts: 334

WHEW! I thought for sure someone with no electronic knowledge
told you to plug into a 12v source. The reason I said 20A is because
most cars' cig sockets are fused at 15 to 20A. Glad you know what
you're doing! Enjoy your new toy!

__________________
Rick

www.visorsolutions.com

09-14-2001 06:12 AM

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

NEW TOY

Yes the new toy is fun - only problem is memory is starting to get low so one of the next projects is the 16MB upgrade

09-19-2001 03:41 AM

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