Some questions about SLA batteries

[Zooty]

Hi all, i posted a Bedini/JT/Tesla switch hybrid circuit on the SEC/JT/Variants thread. I am using this circuit to charge a 7AH SLA battery. The battery is new and has never been charged on a conventional charger. I ran it down to 12v then charged it up. The voltage settled to 13.01 after a few hours disconnected. I have been running it down at 250ma and so far it has been going for 17 hours and the voltage is reading 12.03. Should i take it lower than 12v? The circuit i use draws 125ma@24v to charge it. I didn't measure the time taken to charge it the first time but i'm pretty sure it was nowhere near 17 hours. If i run the battery down below 12v, will it damage it? The C20 rating is 350ma. Should this battery last for more than 20 hours at 250ma? Sorry if i am asking too many questions, some information would be much appreciated. Thanks.

[sucahyo]

Hi all, i posted a Bedini/JT/Tesla switch hybrid circuit on the SEC/JT/Variants thread. I am using this circuit to charge a 7AH SLA battery. The battery is new and has never been charged on a conventional charger. I ran it down to 12v then charged it up. The voltage settled to 13.01 after a few hours disconnected. I have been running it down at 250ma and so far it has been going for 17 hours and the voltage is reading 12.03. Should i take it lower than 12v? The circuit i use draws 125ma@24v to charge it. I didn't measure the time taken to charge it the first time but i'm pretty sure it was nowhere near 17 hours. If i run the battery down below 12v, will it damage it? The C20 rating is 350ma. Should this battery last for more than 20 hours at 250ma? Sorry if i am asking too many questions, some information would be much appreciated. Thanks.

Some believe new battery is safe to be discharge to 11.45V. The charging seems low. How much current actually used to charge the battery? Put amp meter in series with charged battery. Aim for 350mA.

[Farmhand]

Hi Zooty and sucahyo,

Sounds like the circuit you use is good, I probably wouldn't run the battery down below 12 volts myself, I charge those batteries on less current than that and more sometimes, i'm not too fussy, but to get cop measurements or good estimate's I wouldn't use too much more than the C20 rate like sucahyo says.

In my experience the batteries won't give out thier rated capacity unless you drain them down till you get it. So I think you got a reasonable amount out considering it appears you charged with the same current as you drained and charging was shorter.

I am interested to hear if you can do it over again.

Regards

[Zooty]

Some believe new battery is safe to be discharge to 11.45V. The charging seems low. How much current actually used to charge the battery? Put amp meter in series with charged battery. Aim for 350mA.

The analog ammeter meter shows 125ma@24v in series with the battery. The voltage across the recovery diode measures 0.6v above the charging battery with a DVM but my scope shows a 2.5v peek to peek square wave.

*EDIT*

I just adjusted the sensitivity of my scope and looked at what is happening across the charge battery terminals. There is a triangle wave that is expanding and contracting at around 7hz with huge random spikes bouncing off the top and bottom of the scope. There is also a sine wave in the 100mhz range ?? The scope goes up to 10mhz and i counted around 10 peeks. May just be my scope is rubbish at that frequency but i have never seen that across a battery before.

[sucahyo]

The analog ammeter meter shows 125ma@24v in series with the battery. The voltage across the recovery diode measures 0.6v above the charging battery with a DVM but my scope shows a 2.5v peek to peek square wave.

I see, that is decent then. I thought that is consumption current .

11.45V is the safer limit. There other who suggest bellow 11V.

Make sure you charge SLA by alternating radiant and conventional, otherwise your SLA may show normal voltage but have no charge. Voltage drop very high with load.

[Farmhand]

Make sure you charge SLA by alternating radiant and conventional, otherwise your SLA may show normal voltage but have no charge. Voltage drop very high with load.

Yes I agree. If your radiant charger can be adjusted to provide the maximum current that you want to charge with you should get much faster charge times than a conventional charger because the radiant energy will cause current you can't measure, and that should give pretty close to "1 to 1 in out" or even more in overall efficiency when you measure what you get back out of the battery if the battery is good and conditioned. Well thats my opinion. I base my opinion on the fact that I could light 6 led's in series with almost pure radiant energy 6.5 volts while not being able to measure any current.

Cheers

[Zooty]

I see, that is decent then. I thought that is consumption current .

Yes, that is the total circuit consumption. One side of the ammeter is connected to the source positive and the other side is connected to the positive of the charge battery. I also put a 200v 330uf cap in between the recovery diode and the positive of the charge battery, it shot up to 250v so i think the flyback is pretty high. The battery has been charging for 12 hours now and its at 13.03 and climbing. Considering it took 17 hours to run down at the same wattage, this is looking surprisingly good. The next load test will tell the story.



*EDIT*

Make sure you charge SLA by alternating radiant and conventional, otherwise your SLA may show normal voltage but have no charge. Voltage drop very high with load.

In this circuit, when the transistor switches on, a conventional current is forced through the charge battery from the source otherwise the coil would not energize. Immediately after on the OFF, the radiant hits the battery. The diode on the source is there to force the radiant through the charge batt only. Without it, the current usage is a bit higher and the charging is slower.

[citfta]

Thanks for the circuit

Hi Zooty.

Thanks for that circuit. It looks like the Ossie Callahan version of a Bedini solid state charger with an additional diode on the charge side. I haven't tried it like that. If it makes the current draw go down and the charging go up then you are really close to a winner or maybe already there. I had good luck with the original Ossie circuit. I think one of the things that make it a good charger is during the on time of the transistor you are charging with regular current so the battery is getting charged with both kinds of energy. I kept swapping the batteries around for over a week looking for a net gain in all the batteries. I did not get a gain but I only lost a few hundredths of a volt in over a week of swapping batteries so you may see a gain with what you have. Another thing you can do is replace the 1k resistor with a 100 ohm one and put a 1k or 5k pot in series to the base and then you can adjust for even better output. After you have determined the best total resistance to the base you can then replace the pot with fixed value resistors to keep the circuit stable. Pots have a tendency to get flaky if they are not adjusted regularly. Thanks again for sharing an interesting circuit.

Carroll

[Zooty]

Well it's not OU by a long stretch. It managed 90% .. back to the drawing board.

[SeaMonkey]

Some believe new battery is safe to be discharge to 11.45V. The charging seems low. How much current actually used to charge the battery? Put amp meter in series with charged battery. Aim for 350mA.

To get the longest life from a battery it
must be properly cared for.

Attachments provide details.

[sucahyo]

The battery has been charging for 12 hours now and its at 13.03 and climbing.

I think 12 hours of charging with 250mA is slow. Do the battery get warm?

This circuit is similar to Inquorate Tesla Switch - Joule thief. I also try this once but I don't continue because the battery get warm.

In this circuit, when the transistor switches on, a conventional current is forced through the charge battery from the source otherwise the coil would not energize. Immediately after on the OFF, the radiant hits the battery. The diode on the source is there to force the radiant through the charge batt only. Without it, the current usage is a bit higher and the charging is slower.

That is interesting and weird .

To get the longest life from a battery it
must be properly cared for.

Attachments provide details.

Thanks for the link. Bedini also mention same thing about lead acid battery should be stored in fully charge condition.

While completely discharge a battery is not recommended, I found that dead shorting a broken SLA can allow it to store more charge.

[Zooty]

I will keep exploring this setup until i am completely satisfied that there is nothing special there.