Trying to get the most out of a charger.

I need a DC power supply, bigger than what I've got. Any reason why I can't connect two automobile battery chargers in parallel to suply the same vehicle?
Let's say one puts out 13.8 volts and the other 14.2. Is the first one really going to be a load on the second?
What happens if they are both connected to a discharged lead acid battery that's now putting out 4 or 8 volts**? Won't that lower the voltage of the 14.2 charger to where it's not backcharging the 13.8 charger? And won't the battery charge at rate of the sum of the two chargers, 2 (or 10) amps and 10 amps?
**Or if they are both connected to motor scooter whose starter motor is engaged.
A separate question: The charger I'm using now has 2 amp and 10 amp settings. It was on 2 amps, to charge a sealed burglar alarm style lead acid gel battery, used in place of a motorcycle battery in a motorscooter I'm working on. When I pressed the starter button to electrically crank the engine, the ammeter on the charger went immediately all the way to the right, 10 amps or more. But it was not enough to crank the engine. It made an effort, a little noise, and stopped immediately.
Given the way chargers are usually wire, will setting the charger on 10 amps provide more starting power than setting it on 2 amps? I would have assumed the answer was yes, but the ammeter went to 10 amps even in the 2 amp setting.
And before anyone brings it up, I've been testing the kick starter too, and the ignition and fuel systems. I'm making mulitples tests, in order to test all the systems. Before I recommend spending money on a battery and a couple other parts.
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wrote:

I've used two battery chargers at the same time on cars many times. Never had a problem. Of course I'm talking about two small chargers. Like a 6 AMP and a 10 AMP. I would not connect two 30 or 50 Amp chargers together. I'm just charging at a rate of 16 AMPS, which charges the battery faster than the individual chargers. Since you can buy a 30 or 50 A charger, 16 A is still minimal compared to the bigger chargers.
Just sharing my experience, not guaranteeing you can do it safely. But like i said, I've never had any problems doing it.
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On Fri, 13 Nov 2015 03:41:20 -0600, snipped-for-privacy@unlisted.moc wrote:

Good enough. Thanks. (Though I've written down your email address and my estate will be suing you if this proves fatal.)
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wrote:

It wont be fatal for you, it's only 12volts. But it could damage a charger or battery, although I have never had that happen. My chargers are old, so they dont have all the circuitry that some new ones have. It's just a transformer, some diodes, and a reset to shut it down in the event of a direct short. Very simple, and I have fixed several of them over the years. Usually it's a bad diode or two, or that reset device fails. I did have one burn the transformer out, after it got rained on. I learned that the hard way! I always cover them now if they are in use outdoors.
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Somewhere I've got an ancient charger that the Halfords store used to sell - the metal case is the only original part.
The rectifier was replaced with one from a motorcycle and the transformer with one from a Philips black & white portable. The cheap & nasty plastic moving iron current meter was replaced by an Admiralty bulkhead mounting instrument.
A resistor was added before the rectifier to limit the current because a TV PSU transformer doesn't have a charger transformer impedance characteristic. A couple of big film capacitors were added to make the rectifier voltage doubling (for some strange reason it actually gets up to about 42V with no load!). Which works rather well for saving sulphated batteries. Later I added a big fat electrolytic for zapping whiskered nickel cells.
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One of the UK hobby magazines published a project for a super-duper battery charger involving 3x LV lighting transformers, all assembled in a cheap steel tool case.
Can't remember which one or how long ago.
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On 11/12/2015 11:48 PM, Micky wrote:

The open circuit voltage of a charger means next to nothing.
The only problem I can see is that most chargers today are automatic and need to sense battery voltage before they turn on.
If the battery voltage is too low, the charger will not even turn on so a non-automatic charger would need to be used to get the current flowing.
If the battery is /extremely/ low I've seen situations at work where we'd have to put the battery on a variable charger and crank the voltage quite high in order to get the charging process started...then after a very short time switch the battery over to a conventional charge.
(As you probably know by now I was in the industrial battery business)
At any rate I don't recommend putting two chargers in parallel but on the other hand I don't see that it would hurt anything just as long as you disconnected one once the battery got close to 80% charged.
NOTE: To avoid a spark and explosion do not disconnect while under power
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On Friday, November 13, 2015 at 7:50:38 AM UTC-5, philo wrote:

And or go into maintenance mode, etc. In short it's probably not a problem with non-smart chargers, but might be with ones that are.
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Not even an override switch? That seems like a bad idea.
For example, the battery I started with, which I have only for testing things, had a voltage of 0.1 or 0.2 volts, but I can usually charge it to 11 volts or more. Actually I'm not sure the battery will help here since it's sooo bad. But I'm stuck in the mold of my car, where the oldest crummiest battery I ever had would still, when jumped from another car, take a charge in about 5 minutes and spit it back to the starter motor when the jumper cables were too thin to directly start the car.
Somewhere I think I have an old motorcycle battery I also saved for testing, but I haven't found it.

Yes. I'm sure you know what you're talking about.

Okay. Once the scooter starts running, it has its own alternator/rectifier.
I'm told on a scooter forum that there are scooters that run on AC current mostly and that they will start without a battery, but that those that are DC won't. (or perhaps it's enough if they have a charger connected.)
For the AC current scooters, seems to me, they should make AC batteries. Isn't AC Delco a big maker of AC batteries?

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On 11/13/2015 07:54 AM, Micky wrote:

If the battery was brought down to a very low voltage but charged within a few days, it should recover (if it was OK to begin with)
However if a battery is left to sit "dead" for a very long time...once stage 3 sulfation (permanent crystallization) has set in...there is zero chance of it being recovered.

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Micky wrote:

Just amazing!!!!
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Way back when some power stations in the UK produced DC mains - some people charged their car battery by putting it in series with an electric fire.
These days; you need a pretty hefty bridge rectifier.
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On Friday, November 13, 2015 at 1:00:52 PM UTC-6, Ian Field wrote:

What is an "electric fire" a radiant electric heater?
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Yes, that's how they're referred to in the UK.
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On Sat, 14 Nov 2015 00:57:51 -0800 (PST), Uncle Monster

I don't know either, but one time I walked by, just a block or so outside of the Wall St. area, the location of Edison's original power station. Which was DC of course. Read about the competition between Edison and Westinghouse, and about electric chair, etc.

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On Thu, 12 Nov 2015 22:57:06 -0800 (PST), Uncle Monster

I'm in a townhouse and park in a lot. Almost all the houses are right next to their parking place, but mine is about 40 feet away. That's good because my house is at the end and tucked away and a lot of people, even those who live here, don't even realize I'm here.
But too much trouble to roll the scooter and all the tools and the radio etc. out there.
Thanks

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