Using a different charger

[ChrisGreaves]

See also my topic Chargers vs Adapters
I have been given a battery charger "Big Device" suitable for a car (as in "Jump Starting")

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The model number is 011-1911-0 and I cannot find a manual (discontinued line at Canadian Tyre) nor a picture of the charger for the Big Device. I suspect the donation came about because the previous owner has lost the little charger.

I own a box of about a dozen chargers from various computing devices, most of which bear labels similar to this:-

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I'm not too worried about the Big Device (although it could drive a reading lamp and an immersion heater next time our power "goes out") nor one of over a dozen computer device chargers that I haven't used in perhaps ten years.

But I would hate to destroy a piece of equipment for the sake of trying to resolve my ignorance.

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The user manual says "Adapter 15v DC @ 800 ma", so I warily suppose that an exact match should work well without damaging either the charger or the Big Device.
Question 1: Am I correct in the above assumption?

The closest match I possess is "9V at 300 ma"
Question 2: A lower voltage from one of my chargers means that it will take longer to charge the big device. I think of voltage as "pressure". Am I correct?
Question 2: A higher amperage (e.g. 2000 mA > 300 mA) means "more energy per unit time", so that might burn out the charging chunk of the Big Device. Am I correct?

In short if I ***had*** to use the 9v @ 300 mA I would give it a try. I don't care that it takes three or more days to charge up the Big Device. Our last power outage of more than 2 hours was 4 years ago.

So much for the theory.

I see that Canadian Tyre has the adapter (011-1599) for $20 plus shipping, plus tax on top of that, so I won't be offended if a response says "Chris, order the adapter when the pension comes in, and get on with your life, such as it is!".

But still and all I am curious about what leeway there is in these adapters that breed within the carton year by year.

Thanks, Chris

[Leif]

Roughly speaking:

You should ALWAYS match the manufacturer's recommendation unless you have good knowledge of the product and and understanding of what you are doing.

Charger Voltage: I would guess that the internal battery would be a nominal 12V, possibly charging up to 13.5V. This means that anything under 15V may be a waste of time, and anything over 15V risks burning out the internal electronics. (I would guess that there is minimal internal regulation as it adds cost and inefficiency.)

Charger Current: It may be that the internal regulation would handle more than the 800mA stated, but I wouldn't want to risk it.

Big Battery Capacity: Stated capacity is 12Ah, which means that you could (should) get 12A out of it for 1 hour. This, of course, depends on the condition of the battery.
"1200 PEAK AMPS" means that you can draw 1200A out of it short term. Possibly for just a few seconds.
"600A CRANK ASSIST AMPS" means that you should be able to draw 600A out for long enough to start an average car, maybe 5-10 seconds.
(I would like to think there would be an in-built thermal trip for protection from extended use.)

1200A out of a good condition 12Ah battery would last a maximum of 12/1200 hours, or around 36 seconds. If you can find a 12V element for your immersion heater, rated at say 1KW, you may - if you are lucky - get it warming your water for about 8.6 minutes from a full charge.

Depeneding on previous usage, there is also the possiblity that the battery is knackered, either from normal use or being left uncharged. If you have access to a voltmeter and can measure the output volts at anything less than 11V, I wouldn't waste your money or time.

[ChrisGreaves]

You should ALWAYS match the manufacturer's recommendation unless you have good knowledge of the product and and understanding of what you are doing.

Thanks Leif; you have "pushed me over the edge" into NOT trying to mix-and-match.

A new adapter/charger is $20.
A new car battery charger is $90
I do not own a car.

I suspect that my collection of chargers - about a dozen - are good for only one thing: To set up a small electro-plating business here in Bonavista!
Thanks again, Chris