12v Charger For GPZ

[Norvic]

Fred, I am not a very good tutor, in fact I`m a total failure, the GPZ battery is 72 watt/hrs CAPACITY, if it is say fully discharged and takes say 4 hours to recharge, divide the 72 watt/hrs by that 4 hours. That gives us the figure of 18 watts POWER, divide that again by your charge battery voltage 12 volts that gives us 1.5 amps CURRENT(FLOW). How did you get 10 amps? remember amperage is a measure of flow not capacity. The amount of power required to recharge a 72 watt/hr capacity battery is 72 watts in a hour, if it takes 4 hours to recharge it the equation above tells us you need a flow rate of 1.5 amps at 12 volts. Plus because of inefficiencies such as some power being converted to heat as noted, add a wee bit more.

 

Rechargers for batteries should be never placed on in or near a flammable surface, OZ has a few burnt out detecting vehicles in remote locations, testament to this.

 

 Wow you have a tank with a 155amp alternator. The trailer with a deep cycle battery is certainly the way to go.

 

Now for the Quiz...................

[AUddicted]

After getting a new power cord from ML for my 12V charger, I decided to give it a try. Everything worked properly, one problem. I put the charger on the soft surface of the seat cushion and that didn't allow the charger to have any ventilation. The first light on the top left was flashing red, but the battery was fully charged and the battery and charger were both very warm. Second attempt, I put it on a hard surface and no problems.

                                                                    Norm

I experienced the same thing. Works fine on the hard rubber floormat.

[Reno Chris]

Norvic - Batteries are rated in amp - hours at a certain fixed voltage. if the capacity is 72 watt hours, the capacity is 72 watt hours. How long it may take to discharge or recharge is a whole other thing. 72 watt hours divided by 12 volts is 6 amps. So 6 amps at 12 volts will give you 72 watts. If you put that amount of voltage and amperage into a battery for one hour, that is 72 watt-hours. If you had 6 amps going in at a time (at 12V) , it would charge in one hour. If you put in 12 V at a flow rate of 1.5 amps, then it will take 4 hours to charge. If you bleed that out of or into the battery over 2 hours or 4 hours or 10 hours, its still 72 watt - hours - just the amperage changes.

When you have a big charging source like a 155 amp generator, the battery charger wont allow you to put all of that amperage into the battery at once - the charge would be so fast it would badly damage the battery after only one use. So you have a charger that will allow you to put in maybe 30 amps into your car battery (or something in that ballpark). That way, if you wanted to add 10 amp-hours to your car battery charging at 30 amps and 12V, it would take 20 minutes or 1/3rd of an hour. For the much smaller battery of your GPZ, the charger allows you only to put in a charge at a rate of around 1.5 amps - that allows that you can charge the GPZ battery over 4 hours, giving a total of 72 watt hours at 12V.

[fredmason]

No Noric, I am likely the source of the confusion-just ask my wife or loving offspring...

however, in the beginning,  I did ask if my assumptions and math were correct...

You and Chris are excellent tutors...I thank all who have endeavored to enlighten me.

fred

[Norvic]

Chris, Yes batteries are rated in amp/hrs. Sorry mate we will have to agree to disagree, volts X amps = watts which is a measure of power, you cannot divide watt/hrs by volts to give amps. Watt/hrs is a measure of capacity. Give you a clue to what I`m on about have a look at the output in amps and volts marked on the 240/110 volt charger that comes with the GPZ.

[Reno Chris]

Sorry mate - I did my years of physics and engineering classes at the local university and even got my degree. Worked as an Engineer for nearly 3 decades and doing simple algebra with units and numbers was a big part of my job.

Perhaps we just have a confusion of terms.

If you divide watt-hours by volts you get amp-hours. Amp-hours are a real unit just like watt-hours.

A watt hour is a wattage power rate put out for one hour. An Amp-hour is an amperage rate put out for  one hour.

Amp-hours x volts = watt-hours, so a battery rated at so many amp-hours at a certain voltage can also be said to hold a capacity of so many watt-hours based on the amp hours rating times the rated voltage. It all does work out.

Times can be variable and still give the same watt-hours.

1.5 amps x 12V x 4 hours = 6 amps x 12V x 1 hour = 12 amps x 12V x 30 minutes = 72 watt hours. All of these power outputs are the same.

A 12V battery rated at 6 amp-hours is a 72 watt-hour battery.

For more info see: http://en.wikipedia.org/wiki/Watt

Especially the last entry on the confusion of watts, watts per hour and watt-hours.

[Norvic]

I won`t give my credentials, but assure you it is my trade and advanced trade qualifications, which I practised for many years, 20 years manufacturing portable low voltage refrigeration for mobile and solar applications, a very profitable endeavour long before the big manufacturers seen that market. 

There is plenty of confusion in this area. I suspect the 10 amp figure Fred deduced was from dividing the GPZs battery capacity(72 watt/hr) by its voltage 7.2 volts. My explanation of this matter comparing it to water, pressure, volume etc is a time proven way of explaining these matters in a manner that I believe applied in Freds case. All what you say is correct and all what I say is correct. In this case the GPZ battery requires approx. 4 hours of charging which gave my figure of 1.5 amps, the actual 110/240 volt charger max output is 1.67 amps. No confusion here, only in getting my message across. Batteries capacity of GPZ battery is in Watt/hrs which is what I was on about.

I don`t doubt your qualifications.

However I have the runs on the board for using the physics of eleketricity in a practical manner. I always kept the smoke in well nearly always

[Steve Herschbach]

I graduated from a high school in Alaska so I am staying out of this one! I do know a GPZ runs dead in a day and charges fully before morning.

[Norvic]

On you Steve your the wise one and I`ll follow your wisdom.

[Sourdough Scott]

I have two PHD's. A Portola High Diploma, and a Post Hole Digger. I've worked on a few bikes. Hoping to get my Professor of Harley Davidson soon. Lol