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Question regarding AC wall chargers and what they have printed on them

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randaza1

New Member
Hello all, I hope I am in the right area....
I have jump starter (under the name Peak Performance 600 Peak Amp Jump Starter) this if it needs clarifiying is for jumpstarting car batteries when needed.

Anyways, like most, I have lost the charger - I think!!!
I contacted Peak, they advised me that what I am looking for is the following printed on the charger:

WHAT I NEED - misplaced or lost:
120VAC / 12VDC
300mA


WHAT I HAVE - located in a bin with a few other chargers:
120VAC / 12VDC
500mA

So my question is this....Since i have a 500mA and not the 300mA, can I safely use the charger with the 500mA?

I also understand that it is a must to be sure that the tip is polarized as inner is negative and the outer is positive...thats is how the recepticle receiver is designed...

Appreciate your help in advance..

Tony
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Yes Tony. Think of it like this, Your car battery can supply say 400 Amps at 12 V for some time. Now you connect a 20 W headlamp. The power source will deliver what the headlamp requires.

Fusing/protection is another matter, but usually the fusing would be in the device itself. Laptops use a more sophisticated supply where the limiting is also in the supply.

You understand the requirements. Don't forget that the outer barrel and inner hole should be the same too.
 
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ChrisP58

Well-Known Member
Most Helpful Member
Possibly, but probably not. It may also depend on what type of supplies the two are.

You can't fully charge a 12Volt battery with 12 volts, unless you add extra circuitry to boost the voltage. The original charger was probably an unregulated transformer-rectifier supply, with a open circuit voltage higher than 12.

If the new supply is a regulated switch mode type, then it won't have the voltage headroom needed to take the battery up to the 13.8 V needed for a full charge.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Chris has an interesting point. They may have used a unregulated charger where the output would be >12 V. This is probably used to charge a SLA (Sealed Lead Acid) battery.

Chargers can be regulated an unregulated.

They are pulling your leg when they say 600 Amps.
 

JMW

Member
Don't see a problem other than verifying the plug is the same size and polarity. Do you know how to read the polarity from the label? I would guess it will take a fair amount of time to charge this thing at 300 MA even 1/2 amp, your looking at several hours. Watch these chargers though, SLA batteries don't like to be overcharged.
 

randaza1

New Member
Thank you....I am confused on the point your trying to make with the example of the 400 amps at 12 v .... etc... Sorry :confused:
 

randaza1

New Member
ooooook i think :confused: i am really sorry guys...electrical just confuses the heck out of me...dont get me wrong...i love playing with circuit boards, solder and LEDs hooked up to "dance" to music...but when it comes to the stuff that can really make a small issue a bigger one, thats where I need the pretty much lay it on the line type answers... again...sorry :(
 

randaza1

New Member
Don't see a problem other than verifying the plug is the same size and polarity. Do you know how to read the polarity from the label? I would guess it will take a fair amount of time to charge this thing at 300 MA even 1/2 amp, your looking at several hours. Watch these chargers though, SLA batteries don't like to be overcharged.

I think JMW, I am understanding....if i may digress: so your saying that the 500mA charger that I found (this was not the original charger that came with the jumper), is OK to use in place of the 300 mA charger (the original charger) which i lost/misplaced.

and in answering a couple other ?'s that came up:
- I have no clue if the charger is regulated or unregulated :(
- Yeppers, I know how to read the schematic for polarization, but very much appreciate that you took the time to ask / remind me to check that.
-Am i correct on this: if the original plug had 300mA listed on itself, I can go HIGHER, in this case use the 500mA; but cannot use a charger that has a LOWER mA listed on it..
 

MikeMl

Well-Known Member
Most Helpful Member
...
-Am i correct on this: if the original plug had 300mA listed on itself, I can go HIGHER, in this case use the 500mA; but cannot use a charger that has a LOWER mA listed on it..

All other things being equal, yes you could. It would take longer to charge-up a discharged battery, however. Once a SLA battery reaches full-charge, it only takes a few tens of mA to replace the charge lost due to self-discharge.

I charge SLA batteries all the time with a lab power supply. It has dual meters, voltage and current. If you set the supply to 14.2Vdc (the recommended charge voltage for 12V SLAs) depending on state of discharge and battery capacity, the initial charging current could be several A. As the battery charges, the voltage remains at 14.2V, but the charging current tapers to less than 50mA. If then you set the power supply voltage to 13.8V, and come back a few hours later to check the current, it will be 20 to 30mA in cool temperatures, and as much as 100mA at high temperatures.

To charge a badly discharged 50Ah battery, you must put in ~20% more than that, so it would 70 hours at 1A, 7 hours at 10A, or 140 hours at 500mA.

Your jump starter rarely gets discharged to less than 90% of its capacity, so recharge time is much shorter.

A word of warning. If you let a SLA battery sit around for more than a few months without being on a float charger, you might as well dump it. At 100degF, a lead-acid battery looses 10% of its charge per month. If you let a battery sit around with less than 90% of its full charge for more than a month or two, it sulphates, and looses capacity. That capacity loss is permanent, and cannot be recovered (regardless of what the Pulse Charger snake-oil salesmen pitch). The only way to prevent this is to keep the battery on a float charging regimen.
 
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