Charging sealed lead acid battery

[dmonarch]

I am making an electret this weekend. I have a hv unit which runs of a 12v sealed lead acid battery. I have yet to charge it since purchasing however have only used it a couple of times to run the hv unit.
I dont want the battery to run out during the process so my question is, is it possible to charge these batteries at the same time while using them. Will this effect the hv generator. As well what is a good charger for such a battery, something cheap would be excellent.
Cheers

[nvisser]

I have seen on home alarm systems how they do it
A 18v ac transformer , full bridge rectifier, 4700uf 25v capacitor, 7815 regulator. The 15v dc goes through 2 diodes to drop it to 13.6v and then to a 10 ohm 5w resistor to the battery. The battery supplies the load through a 3amp diode 1n5406

[Inquorate]

Battery charging

I bought one of those multi step down transformers for a wall plug; 300ma at 3, 6, 9 and 12v..

Couple of dollars at cheap 2 dollar or bargain store, connected in series it will add it's amperage to the batterie's current.

But if you're using ignition coil for hv, you'll want to put a big cap in parallel across the output.

[ren]

I am making an electret this weekend. I have a hv unit which runs of a 12v sealed lead acid battery. I have yet to charge it since purchasing however have only used it a couple of times to run the hv unit.
I dont want the battery to run out during the process so my question is, is it possible to charge these batteries at the same time while using them. Will this effect the hv generator. As well what is a good charger for such a battery, something cheap would be excellent.
Cheers

Hi dmonarch,

Please give us some more specs of your HV unit. To answer your question better some info on amp draw would be great. You could also get an idea of how long your battery would last if we knew its rated capacity and the draw of the transformer. You dont want to charge the battery while drawing from it, this will only cause you dramas in the long run. You could get a DC benchtop power supply to replace the battery and then you dont need to worry about it going flat. You need to be careful however if you are using it to run HV. A good stepdown transformer to the voltage and current levels you require could be a simple fix.

As far as chargers go, we could also give you a better idea if you gave us your location, unless you are happy to buy over the net, then there is no problem. Look for something that automatically switches to trickle charge, and has all the safety features. I got my 12v 1amp charger for under $40. It works well.

Regards

[dmonarch]

Now why didnt i think of that

Gee im slow. I havnt used the hv unit for a while and since then purchased a nice benchtop power supply. What a wally. Thanks for reminding me. That will solve the problem flat out.
Excellent

[Inquorate]

Nice to have you back Dmonarch

Hope the Electret videos I made can help you with your project.

good luck

[dmonarch]

Nice Work

Did you actually complete an electret and test. I cant find any video of this. Also did you find it necessary to have the rosin. I have carnuaba and bees wax. I am not looking to make anything permanent as yet so dosnt need to be utterly strong just needs to good enough to maintain the polarization
Cheers

[Inquorate]

Electret

http://www.energeticforum.com/renewable-energy/4483-electret-experiments.html

The last one shows the most promise, just waiting a little bit longer to see if there's a charge on it.

[dmonarch]

Made Electret

Well just making my electret now. Hopefully it will go ok and will get back to you on results. I have predominantly used the canuaba wax vs the bees wax. The canuaba came in crumbs while the bees wax in blocks i just couldnt chop it. Dang I just realised i could have used a hack saw blade just bought, oh well next time

[dmonarch]

Harder than it looks

Wow its more difficult to make an electret than it seems. Getting the mixture right would seem to be the most important aspect. The first electret i made cracked. It was predominantly carnuaba wax. The stuff is too brittle which is why assume you add bees wax to hold it all together. As well the addition of rossin would provide something for the wax to hold on to like sand in cement i guess. The second electret i made i totally stuffed up. Wax went everywhere, luckily caught by a box that happened to be under the table i was working on. Seemis am going to have to put a little more thought into this. What i might do is simply play around with mixtures before i even try and turn it into an electret. Just make up a bunch of testers to see which has the best properties

[Inquorate]

Learning experiences

I really recommend watching my mistakes!

It will be less likely to crack if the temp is reduced gradually over about 4 hours.

It is really hard, but no harder than baking the first cake if only we had better instructions..

Best wishes

[Inquorate]

Ps re the mix

Without rosin, I found 85 parts carnauba wax, 10 parts beeswax and 5 parts tealight (petroleum?) wax cracked less.

The carnauba shrinks a lot, and needs a little bit of something with a lot of give mixed in.