Is my calendar wrong?

If you go to Maplin you can buy a device which is only a bit bigger than a mobile phone, with two weedy cables terminating in small croc clips which they claim will deliver 200 amps to jump start a car.

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Surely, it *must* be April 1st?

Reply to
Roger Mills
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You'd think so, I did see that photonicinduction nutt^H^H^H^Hbloke using a similar device to start a 5 litre v8 merc with a flat battery, it didn't *seem* to be fake ...

Reply to
Andy Burns

But if the battery can deliver 3amps for an hour presumably it could deliver 200amps for about a minute? Enough to start a car?

But what do I know!

Reply to
Murmansk

With the diesel van, did he connect the positive lead of the charger to the negative lead of the battery?

Also, how much time really elapsed between connecting the charger, and starting the engine? When using battery-to-battery jump leads, it pays to leave the donor vehicle with the engine running at a fast tickover for a minute or so before attempting to start the recipient. That way, you give the flat battery a fast boost charge, so it's that battery that provides the high starting current, and not the jumper leads.

Reply to
Ian Jackson

I dunno ... but while we're talking about batteries, I know there a few here who've complained about how APC UPSes tend to cook their batteries, this is a classic we found last week, had to disassemble the UPS to get it out ...

Reply to
Andy Burns

there are lithoum ion batteries for model use that are rated to be falattened in 2 minuets

a 10Ah one - by no means large at 12v - would be enough to start a car - once!

Reply to
The Natural Philosopher

Hell of a device. Rather better car battery clips tho than the first one.

And not cheap either.

Reply to
Jacko

!

Does it not depend on who wrote the minuet and how fast it is played :)

Andrew

Reply to
Andrew Mawson

Unless your being scammed, your description of this device seems to preclude anything working at all. Brian

Reply to
Brian-Gaff

If you listen to the video, from the point in time in this link, you'll hear the description and results. The bloke comes across as a propah diamond geezah, that's his normal style, but he has plenty of other videos out there ...

Reply to
Andy Burns

I did mention this to a colleague of mine, a real electronics expert who also does a lot with cars (currently building his own fuel injection control system for an ancient Rover).

He has one of these things and he says they actually work. But get one of the bigger (400A) jobs if you want it to work on an old, sick diesel engine!

Reply to
Bob Eager

it's 36 watts for an hour in theory

200 amps at 12v 2,400 watts.

24,000/36 = 666

So make that 1/10th second.

Reply to
Dave Plowman (News)

Depends on how quickly the car normally starts. A petrol engine which has had an attempted start and failed with a flat battery may not be in a position to start instantly.

And I doubt there are many cars which takes as little as 200 amps on a very cold day. The batteries in both my cars are rated at 600 amps cold cranking.

Reply to
Dave Plowman (News)

If he wants any help with MegaSquirt on an RV8, let me know. ;-)

I can assure you 200 amps wouldn't start my SD1.

Reply to
Dave Plowman (News)

A 3Ah battery != a 200CCA battery.

But do they really NEED 600CCA? Or would they be quite happy with 200CCA, but a 200CCA-rated battery would only deliver 200A for about the first week after it'd been installed, before the inexorable decline reduced that to 199 - 198 - 197...etc. A 600CCA battery will still be delivering sufficient current to start a car even after years, right up until the point it's utterly fubar.

Reply to
Adrian

Thought I'd cancelled that post. ;-)

Should be 2400, so approx one minute. Which I still don't believe.

Reply to
Dave Plowman (News)

I dunno how much a lead acid deteriorates in use. I normally find they work ok until they die (unless there are other symptoms before)

Reply to
Dave Plowman (News)

Ah, but is that because there's sufficient over-specification that you don't notice the gradual deterioration until it's bad enough that you do...?

Reply to
Adrian

Check the charging voltage. Cyclic (initial charge) can be up to 14.5V. Once charged, if the UPS then continuously float charges it, charging voltage should drop to 13.65V.

UPSs often charge batteries really quickly so they are ready to be used again ASAP. Some seem to continually overcharge them though.

OTOH, if the battery has been changed before, it may well not be the correct battery for the UPS. It's not a deep cycle battery; it's cheap, commonly used in burglar alarms where it's float charged.

How many does the UPS hold, and what's the output rating of the UPS?

Reply to
Andrew Gabriel

Well, I have a posh electronic tester. Not quite sure exactly how it does things, but it gives you a readout of the actual battery capacity in amp.hours. It had clever crock clips to give an ultra low impedance connection, so I assume it applies an extremely heavy pulse load, and calculates things from that.

My Rover V-8 spins over a lot more slowly on a cold day, so I'm assuming the battery is delivering not far short of its peak then. Diesel versions of the same model double up on the battery.

Reply to
Dave Plowman (News)

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