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Oct 25, 2013 20:01:31 GMT
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Hello all, I've been thinking, I don't have a proper battery charger, but I do have a 0-15V 0-5A DC voltage supply. If I were to set this to 14.2V (just like an alternator) and leave the battery connected for say, 5-10 hours, would this safely and effectively charge the battery? It seems to me that this would simulate charging it in a car, which seems perfectly fine to me. But since there are all sorts of chargers available and since they aren't just 14.2V sources (I guess?) what is the difference? Why won't it or will it work? Will the amperage be regulated automatically by some sort of electrical wizardry? Thanks in advance  |
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Oct 25, 2013 20:25:08 GMT
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A regulated power supply like you describe is actually a great battery charger. Like you say, limit the voltage at 14.2v and leave it until the current drops to about 0.5A, and the battery is charged.
Some chargers drop the voltage to about 13.8 after the main "bulk" charge is complete, but most of them are a lot more dumb than the setup you propose.
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omega
Posted a lot
Posts: 1,060
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Oct 25, 2013 20:25:35 GMT
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just go down to aldi spend 13 pounds and buy a charger that you can leave connected all the time.
job done.
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Oct 25, 2013 20:35:16 GMT
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Dunno, but I do know Aldi and Lidl both have half decent smart chargers for less than £15 just now...
I guess it would work like an old fashioned charger where you have to switch off when the battery is full or boil it dry, where as modern smart chargers have the electrical wizardry to switch to a "maintenance" mode at this point, as well as "pulse" for flat batteries to break down sulphate. The Aldi/Lidl ones aren't hugely powerful, but ridiculously cheap for what they are. I had one fail once and the warranty was cast iron too.
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Oct 25, 2013 21:31:34 GMT
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Five amps is way to high to be charging a car battery overnight, I know most chargers use up to 2 amps for a quick charge. If you were to regulate it to around 500 Milliamps, it would be safe to leave on overnight. It's just the same as a car Trickle charger without any of the protection circuits. My 'quick' charger puts in 20+ amps, (the alternator will kick out a lot more than that, think in the region of 40amp+). 2 amps is a slow trickle charge, if you take the capacity of an average battery of say 70 amp hour and from flat you charge it at 2 amps thats going to take 35 hours to get to fully charged. I know thats not a realistic really real world calculation taking other factors into account but it illustrates the point. |
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Last Edit: Oct 25, 2013 21:31:59 GMT by dodgerover
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As above, you only need to limit the current if you aren't limiting the voltage properly. You won't damage a battery by leaving it at 14.2V overnight - it'll simply stop drawing current when it's charged.
Those calculations of "charge time" are actually relatively accurate - I charge a lot of batteries at work (we repair boost packs for buses/coaches) and rather than use the internal 2A charger, I have a 30A lab power supply that I use to get the batteries charged up in 3 hours instead of two days.
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Ive been using one of the aldi chargers for a couple of years now, worth their money any day as long as you can leave your battery overnight, they are automatic and have a built in voltmeter
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Oct 26, 2013 10:02:32 GMT
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Something I will mirror from above - the majority of cars are happy driving for extremely long periods on motorways, with no ill effects (I exclude poorly, dying cars, lol) The alternator on my Rover chucks out over 90A, and that's been running for over 6hours at a time. No fancy electronics, just the plain voltage regulator. Your benchtop power supply sounds like an ideal charger - set the voltage to 14v, and let it do it's job overnight |
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You're like a crazy backyard genius! |
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Oct 26, 2013 19:50:22 GMT
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Thanks gents, I had a feeling it would work but it's always very nice to have someone back you up on stuff like this. The reason I won't buy a cheap charger is I already have this power supply laying around, the Aldi/Lidl here doesn't carry a cheap charger with more than 1A charge rate and I think that if it has worked like this in every car for the last 60 (?) years, why not on my desk? But I guess it will work |
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pavel
Part of things
Posts: 211
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Oct 27, 2013 16:32:25 GMT
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Regulated power supplies are excellent chargers. We used them to charge all of our racing batteries. Used to just set to 13.8-14v and forget about it. If the battery is completely discharged, the PS will auto-regulate the voltage to limit current to 5A or whatever yours is, so it's safe as anything.
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