Battery Tester Question

Mike Finley

Okay, I'm an electrical moron when it comes to this stuff, I own 3 or 4 meters and don't know how to use any of the well.

I've got (2) 12 volt marine deep cycle batteries hooked together I believe in parallel (+ to +, - to -).

Fully charged what should they read, and what the hell am I reading? Volts? Amps, Watts, Ounces?

As they decharge and need to be rechared what will I see on the meter?

mdshunk

You'll read 14.3-14.7 volts when they're fully charged. Recharge them whenever you feel like it, or depending on what the lowest safe operating voltage of the connected equipment is.

ron schenker

ounces? too funny

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Teetorbilt

md's on the button! Check it at the terminal and not the connector.

Also check each cell with a hydrometer (the little floaty thingie with a tube and squeeze bulb that they sell at the auto parts store) if they are 'open cell' batteries. One bad cell will drag all of the rest down to it's level.

The other test is with a carbon pile, these are pretty pricey but the only way to check sealed batteries. It's a load test.

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Mike Finley

hmmm, I could have sworn I was reading 26.8. I figured (2) 12 volts = 24 so 26.8 is pretty close to 24. Not right though?

Hooked up the way I have them you still get the same volts?

Dustball

I thought it was ~14.5 volts when the alt is running and 12.7 volts fully charged when reading just the battery itself with no outside charger/alternator affecting the voltage.

Eric K

Im not 100% on this but I think you just raise the amperage or wattage?

darren

Hey there

If your reading 24 or so i would say they are hooked up in series.

MD how do you know it will read 14 and change, i was thinking it would read 12. Or in your experiece do batteries usually read higher then what there rated.

mdshunk

Just so we don't get series/parallel mixed up, I drew a picture. Red is the positive terminal, black is the negative terminal.

Mike Finley

I've got them hooked up red to red, black to black.

I just picked up a power inverter at Sears tonight, I'm going to try charging (3) 18 volt dewalt batteries off these 2 marine batteries with a 5 watt solar panel recharging the marine batteries.

Any chance of this working? I got a 750 watt inverter, I have no idea what I'm doing, but I'm going to start by trying to get a meter to read the correct voltage off those batteries.

mdshunk

Sounds like a plan, man.

So, I guess your flexible solar panels arrived? Cool.

Mike Finley

Actually not yet. Been almost 2 weeks I think, I called them today to find out where the hell it is, but only got voice mail. I'll try again tomorrow.

But from your reply it sounds like you think the math will work? I'm figuring something like 12 hours of sunlight a day, with probably 3-4 hours of charging going on a day max, with other some other days even less. You think the math works for a 5 watt solar panel to be able to cathc up and keep those two batteries topped off?

Magnettica

I gotta hand it to you.

That's one of the funniest schematics I've ever seen.

mdshunk

The goal was to make it so simple, even a monkey could figure it out. I was going to use a cave man, but aparently they're a little sensitive.

Teetorbilt

It will keep them topped off depending on the draw. If you are inputting 5A and drawing 7, it doesn't work. You also lose a lot of energy through conversion heat.

As I envision it, you plan to pump up a battery bank to power an inverter. Know what all of those cooling fins on an inverter are there for? Then you want to go back to DC to charge tool batteries. Know why they put all of those vents in a tool charger? You are losing every step of the way and I don't see it working.

Can it work? Ya! Just not very well, not worth the effort.

I would buy 24V panels, put the batteries in series and get an electronics genius to step it down and wire it into the charger circuitry = 0 loss.

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Sparky Joe

If you're doing all that work, why would you need to a 24v DC system?

RobertCDF

When I get around to hooking up my 12V system in my trailer I was just planing on pluging a trickle charger into one of the many outlets I have inside. Since I leave my trailer pluged in 24/7 it should keep the battery topped off just fine.

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Mike Finley

Originally I had planned on running shore power to the trailer when on the job site, but all I really needed it for is to charge cordless batteries.

(I'm not running a kitchen in there like some people. )

Since I still needed a self contained battery bank which would use a solar charging system for the alarm system, now I'm kind of getting greedy with it and wondering if I can use it also to charge my cordless batteries.

I don't mind buying one more solar panel to double it to 10 watts, but if it turns out I need like 10 more of them, then forget it.

All of this is now on hold anyways, the work bench I wanted to put in the front of the trailer to hold all this crap I found out today is out of stock at Sears and won't be in until next Wed.

Man I hate having to wait to see how this all works!

Teetorbilt

Sparky, higher DC voltages are more efficient than lower V's. It's also easier to step down than step up.

Robert, a simple 12V system works fine and has for years. Mike's talking conversions.

Mike, You originally admitted that you were over your head and you are. I have a 'go to' guy for this type of electronics and that's the way that you should go unless we have one lurking.

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You can't solve you're problems with the same level of thinking that created the problems.

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Mike Finley

Way over my head.

I'm committed to the trial and error method as you can tell, which can get pretty expensive!