On Thu, 19 Aug 2010 16:30:10 -0400, mm
wrote:

On Thu, 19 Aug 2010 12:53:16 -0400, wrote:

On Thu, 19 Aug 2010 08:14:42 -0700 (PDT), "larry moe 'n curly"
wrote:



mm wrote:

Do all chargers except the very cheapest turn off when the battery is
charged, or are there still some big expensive ones that don't do
that, as for a golf cart? Or is the difference more subtle than that,
and important?

That is, the people with the golf-cart (see follow-up post on that
adjacent to this one) bought a new charger, mail order, from a site on
the web that is about golf carts only.

The thing costs 360 dollars!, not what I would call cheap. But on
its label it says, "Check the charger periodically to avoid damaging
batteries. Initial charging rate should be [I forget, 15 maybe] and at
the end the rate should be 2 amps." Does this imply they should turn
off the charger when it's charging at 2 amps? Or it will damage the
batteries? This is it:
http://www.buggiesunlimited.com/product.asp?sku=3618 It doesn't say
much but it calls it an automatic charger. Doesn't that mean it turns
off? But is that still not good enough and the fancier one below is
needed to keep the batteries from being damaged?

The more expensive charger in the catalog they sent is about $455, and
the first words in its description in the paper catalog are "Avoid
over-charging batteries". Does that mean this one has auto-turn-off
and the one for 360 doesn't? Or are they just not mentioning it for
the cheap one to get people to buy the expensive one? Here's the
expensive one:
http://www.buggiesunlimited.com/prod...HG%20EZ2%20002

Can you see all the components inside? If there's nothing there

I coudl have take it apart when I had it, but I didn't. Too late
now.

except a transformer, some diodes, an ammeter, and a circuit breaker
or two, it's a manual charger and can overcharge batteries and damage
them. OTOH the simplest automatic chargers for lead-acid batteries
have voltage limiters calibrated to about 2.3V per cell, meaning at
full charge they'll put out less than about 1/2 amp and can be left
connected for at least a couple of days after full charge. These
voltage limiters usually consist of a regulator chip controlling an
SCR (about 1/2" square plastic thing with 3 leads on it). Better
chargers will shut off completely at full charge but will restart when
the voltage drops to roughly 2.1V per cell. Old style chargers are
heavy because they have a big 60 Hz transformer, but newer designs use
a much smaller transformer that works at high frequency, and these
always have elaborate control circuitry to completely shut off the
current at full charge.

Thanks.

These are 36 Volt golf cart Chargers. The OP is correct that the more
expensive one, which is microprocessor controlled is what is commonly
called a "smart charger". It will charge the batteries faster, and
will not overcharge them if left connected for extended periods of
time.

With the price of golf cart batteries, buying the smart charger is
well worth the extra money.

Well, that's what I told her but I promised her a follow up email,
where I would have back tracked some if you hadn't confirmed this.

Thanks, and thanks all.
My cheapest battery charger is a variac (surplus - no cost) and a
bridge rectifier with a cheap voltmeter. If you need to limit the
current just hook a heater in series with the output or a 100 watt
bulb in series with the input