Leave an unplugged battery charger connected to lead-acid battery?

The battery chargers I've used, the DC output goes through diodes. So, discharge isn't an issue.

I checked two chargers. The manual charger had no drain at all. The automatic drained 7ma. It would take a week to draw off 1 amp-hour.

"Stormin Mormon" wrote in news:gukmr0 $goc$ snipped-for-privacy@news.motzarella.org:

From what I recall from long ago, all diodes have a leakage current rating. Whether it's significant in this case I don't know.

FAIK, the old Si/Ge diodes may be obsolete in today's electronics.

On 5/15/2009 3:19 PM Red Green spake thus:

They all have a leakage current rating; the leakage is very, very small.

Si/Ge? You mean one or the other; modern diodes are all silicon, except for a few small-signal ones (1N34, etc.). Not used in battery chargers, that's for sure.

And of course before that there were selenium and copper-oxide rectifiers, both long obsolete.

mr0

The reverse leakage should be so small as to be insignificant compared to the battery self-discharge.

Batteries need to be monitored by voltage, not guessing. Your battery charger may or may not work or even charge properly to 100%.

I'm sure (well, pretty sure), as others have pointed out, that any draw from leaving it connected to your battery would be insignificant. But since I'm too lazy to actually check it I disconnect the charger from the battery when done. Hell, I might foget about it for weeks or more.

As ransley stated you really need to know your charge voltage and charge rate and duration to properly care for your batteries. This info is usually available from the manufacturer. Some "Smart Chargers" are probably pretty safe to use in general but some other "Automatic" chargers may ruin your batteries in a fairly short time.

Years ago I got a "great" charger, only to find out many years later it was never calibrated to charge 100% or went out of calibration, My batteries never lasted or turned over the car when -20f. One day after learning about what 100% charge is I luckily inside found a screw that adjusted the voltage up. I think most new units are computer chip and probably unadjustable. Not having a battery maintainer has ruined many batteries for me.

Hi, If you have a smart charger with electronic brain, it is OK to leave it on all the time.

Hi. Of course battery internal resistance is a durrent path for discharge.

That would be my suggestion too. Just buy a new smart charger. In the grand scheme of things, especially when you're talking about boats, they don't cost that much. Also, if proper charging gets you some extra battery life, it could pay for itself,

Shottky are becoming more common due to their lower voltage drop (forward). Half a standard silicon diode drop. (like germanium)

A good 3 stage marine charger (particularly the "mountable" type) should be safe to leave connected, either plugged in or not. Some (mainly older units) have "relay" isolation - physically disconnected when not charging. (or not powered on)

No, series resistance cannot cause battery discharge.

NO

EJ > I posted a question in the newsgroup "rec.boats" about recharging a

The self-discharge rate of the battery will be magnitudes greater than any discharge back through the rectifiers of the charger.

Very surprising that your charger doesn't switch to trickle charge mode once the battery is charged. Even the cheapest chargers nowadays do that, i.e. "

Not series resistance, the internal resistance of the battery. The lower the internal resistance, the higher the self discharge (but the higher the maximum current as well). Short out an Alkaline AA cell and nothing much happens because of the high internal resistance. Short out a NiCad or NiMH AA cell, or a car battery, and the result is much different.

Here's the rectifiers I like:

"

Don't alkalines have lower internal resistance and lower self-discharge than carbon-zinc cells?

In my experience, a new nicad may still have a good charge after a month on the shelf. There may come a point when it will discharge itself in a week. I don't think its internal resistance is any lower at that point.