Battery tender question

[latexeses]

I have several 12-13 volt power supplies and was wondering how many volts does maintanance need.

I have one power supply that is 12 volt dc at 350mA and one power supply that is 13.5 volt dc at 1 amp.

I don't need to have a charger, just something that I can use to "rack" the batteries that are not being used and keep a charge. I have some old irrigation clock switches that I can use to switch the maintainer to a different battery every week or so.

Any thoughts?

Thanks,

Rodger

[tw1980]

Most of the battery tenders now are micro processor controlled.I would think that that would be the way to go.But if you want to use the equipment you have off the top of my head I would say,your 350 ma charger about 10 - 15 min a day should do the trick on a motorcycle battery with no leakage.

Terry

[Larrym]

Near Death?

A perfect Fully charged wet cell should read 12.8 volts after resting 24 hours.

If you are going to connect the batts to a power supply then the output of that power supply should be 12.8 VDC or higher. If the supply you are using actually reads 12.0 volts then the batteries will discharge to that point:12 volts. Then the power supply will "maintain" that state of charge, hopefully.

Problem is that a perfectly discharged wet cell battery reads 11.8 volts when it is officially dead. The "12 volt" power supply will keep your battery at just .2 volts from that "dead" state. That's not ideal for a lot of reasons.

Not contradicting Terry on this one. The practice of switching the supply on and off for a short period every day will work.

But the voltage needs to be higher than just 12.0 VDC. Is that what the power supply says it will do or what you have measured it doing?

[latexeses]

I have not yet tested the output of the power supply. That is just the stated voltage and amp output.

I was just trying to determine which voltage and rate of charge would be adaquate without putting the battery on "slow cook".

[Larrym]

Manual Maintainence

A perfectly good/fully charged battery will rise to 14.4 volts when being "charged" by a battery charger or when it is connected to a running engine/charging system. That's the voltage to shoot for.

The 13.5 volt power supply will bring the battery up to .9 volts below that. Not a bad thing at all.

To determine how long to turn the timers on I would connect the power supply, turn it on, then measure the voltage at the battery. When the voltage reaches 13.5 shut the power supply off. That's the best that the power supply will do. Measure the amount of time it took for the battery to reach this voltage once and adjust the timers accordingly.

This will prevent the battery from being constantly "cooked" and still make up for the charge lost due to that "internal discharge" which happens over time. The timer setting will vary for different batteries (size/manufacturer).

I'd suggest rechecking the set up after a week and seeing if the timer needed re-adjustment.

[tw1980]

Sorry I didn't read your post careful enough I was under the impression that the power supplies you have are battery maintainer/chargers.Larry's right you need to test and measure like he said.Once you get the charge duration correct you should be ok.I think probably start with your 13.5 v 1 amp supply.Also check the power supply at the end of the charge cycle and make sure it's not getting to hot.

Terry

[latexeses]

I have a couple different chargers. One that will hammer a dead battery with about 8-9 amps and slow down to about 2 as it reaches full charge. I have another charger that charges at a steady 2 amps.

My plan was to build a rack that I could put any of the various batteries I have, boat, honda, XS etc and run a charge through them once a week or so with out wearing them out by "hard charging" them.

I think anything I hook up and run will get warm. I guess I need to find out what the power supply is putting out after it heats up.

I thought the trickle/maintainer chargers had an output in the miliampere range?

[Larrym]

Lead into Gold?

The battery "maintainers" for motorcycle batteries do put out less than one amp. The bigger the battery>more amps needed to keep it at that "Float Voltage". Like Terry said, the maintainers usually have some microprocessor inside which controls it like this:

"Put out the full amperage and voltage until the battery reaches "Float Voltage" and then reduce the amount of current until the voltage begins to fall. Then the maintainer stays at that voltage/amperage setting."

Check this out:

http://en.wikipedia.org/wiki/Float_voltage

Looks like your 13.5 volt supply is a good match for what you are trying to accomplish. (You lucky Dawg!)

Putting it on the timer system and "pulsing" it daily to 13.5 Volts with the timer set to shut it off is a good manual way of doing the "automatic" version.

I've got boat batteries, the bike battery, and the vehicle I drive has a starting battery plus a "house" battery. I can appreciate the efforts needed to keep from having to buy new batteries every year. Mine are heavy and in all the awkward places for lifting in and out. Lead/acid. Emphasis on the lead.