Capacitive Battery Charger & Capacitive Transformer

[citfta]

Don't do it!!

Please do not build this circuit! What most people don't seem to realize is that if the 100 uf cap should short out you will then have full line voltage on the bridge. If it is connected to the battery you will blow up the battery! If you were to touch the leads while it is not connected to the battery you will have the about 170 volts DC on those leads even if the cap is good. This is if you are using 120 VAC. With 250 VAC the voltage on those leads will be right around 300 volts DC. That kind of voltage will kill or seriously injure you. I have worked in electronics for over 50 years and I would never use that circuit for anything unless I wanted to kill something. Use a transformer. No matter how worthless you are as a person your life is still probably worth more than the cost of a transformer.

Hi
Couple of Qs:
1 My mains V is 250, can I build one or must I step down to 120/150- I have capacitors rated 450V AC and bridge rectifier to 1KV.?
2 My caps are only 11 MFD each - can I parallel some to increase the charging current?
Thanks!

Respectfully,
Carroll

[Allcanadian]

I think this circuit would be fine if there was a 100uF cap on each AC leg before the rectifiers. then I would use a 6$ component called a hall effect current sensor to monitor the DC current and if it exceeded a preset level an SSR would cut the AC input. A simple voltage divider feeding the same SSR could also offer overvoltage protection. In fact this would be magnitudes safer than most battery chargers over 10 years old. This is because most used a bimetallic dry contact switch for overcurrent protection and they are a piece of ****.

As well transformers are heavy, expensive are generally burst into flames when the archaic overcurrent protection fails ... Do not leave them unattended. A good switch mode battery charger is more efficient and much safer. Personally I will never buy a transformer based battery charger again because I have seen them fail... not pretty.

AC

[citfta]

Still too dangerous

Hi Allcanadian,

Your idea has some merit as far as protecting the battery from over current. However it does nothing to prevent someone from being electrocuted by the leads if they should come in contact with them while they are not connected to the battery. Even when connected to the battery either lead is still about 70 volts above ground after going through the full wave rectifier if the supply is 120 volts. 70 volts is enough to kill you if you happen to be well grounded.

When solid state TV''s first came out they decided the big heavy transformers were no longer needed as we didn't need the filament circuit anymore. They went to a circuit very similar to the one posted. They tied the negative side to the chassis which has always been used as the reference ground. TV techs found out real quick that the chassis was now hot in reference to real ground. You couldn't even use your scope to troubleshoot the circuits because almost all scopes have the reference lead tied to the chassis of the scope and since the chassis of the scope was tied to real ground this caused a big problem. If you attempted to connect the ground lead of your scope probe to the chassis of the TV you got a big bang and your scope lead turned to smoke. All the shops I know of had to buy isolation transformers to use with the newer TV's. The isolation transformer made them safe to work on without the danger of being electrocuted and allowed us to use our scopes for troubleshooting.

As far as the transformer goes there is no reason for a transformer to catch fire if the input fuse is properly sized to the transformer. I worked in industrial maintenance for 30 years and saw several transformers fail. They blew the breaker or fuse and that was the end of the problem. All transformers should have a simple inline fuse if they are too small to trip the breaker on the supply line when they fail.

Respectfully,
Carroll

[Allcanadian]

@citfta
I see your point however a voltage divider on the DC end controlling an SSR on the hot AC end should solve that problem.

My issue probably relates to everyone here and I got tired of inefficient heavy chargers with absolutely no flexibility. So I use a buck converter to drop the AC voltage to wherever I want it. Then I added a current sensor to set the current to wherever I want it.

Basically my charger can charge any battery at any voltage or current(within reason) and really isn't all that different than the one posted here other than the current and voltage monitoring. I simply set the voltage cutoff to wherever I want it then set the max allowable current draw and I'm done.

As well the problem with fuses are that the damn things are always blowing, how many times have you spent 10 or 20 minutes searching for that damn fuse you didn't buy spares for, lol, they are my nemisis.

Regards
AC

[ewizard]

Allcanadian, Would you be able to post a schematic of your setup with part numbers? I've got the Eagle research book too and thought about making his setup a number of times but I also didn't feel it was the safest setup the way it was presented. I like your concept.

[Allcanadian]

Hello ewizard

I will have to get back to you on that one, I generally build things as needed to solve whatever the problem of the moment may be and seldom document anything. I will have to trace the circuit and build a diagram.

AC

[bikesandcars]

I made one of these capacitive chargers and it seems to charge 12V batteries very well and from the couple batteries I tried seems to de-sulfate them pretty well.

I tried a 25uF run cap for charging large battires (50AH car batteries) and that seems to work well. It yields a .91 amp charge. I have not "boiled" a battery using this amperage

Is over-charging particuarly dangerous with this type of charger?

For motorcycle batteries a 5uF cap worked better, the 25uF cap was creating a bit of "bubbling" in the 15AH battery. a 5uF cap charges at about 0.19 amps.

I have a couple questions though... using the 25uF and 5uF capacitor does not seem particularly deadly. I measured DC voltage across the leads and it was 110VDC for both (not 170 or higher).

I am considering adding resistors across the capacitors to keep them discharged once disconnecting. thoughts?

The only thing I haven't figured out (not being an EE) is how to make a voltage regulating circuit to control charging (for example, turn off at 14.4 and turn on at 12.6).

[shylo]

Welcome

Hi bsk, do you have any spec's I'd like to give it a try.
shylo

[bikesandcars]

Fig 1 from VIDBID above was what I did.

I guess it can "kill" you from what people said, but I haven't been shocked yet and I'm very careful. Later on I cut the aluminum down and mounted the bridge diode to it for a heat sink. nothing gets remotely hot charging at .9 amp.

The purpose is to de-sulfate batteries, and that needs to be done slowly for best results (from what I gather).

370V 25uF run capacitor from ebay (from air conditioning equipment)
1000V 200amp bridge diode from ebay

16 gauge wire.

I'm going to make a nicer one with a volt/amp meter, timer, and maybe even 2 caps (one for car, one for motorcycle batteries). Also going to add resistors on top of the caps to keep them discharged. I don't know what the above stuff was to make it safe, someone maybe can elaborate.

I'd like to design a circuit that turns the charger off over 14.4 volts with a reset switch, but don't know how. That way if you turn it on without being connected it will not zap you and it won't boil the batteries.

[Berg]

Regarding Microwave Oven Caps

Also going to add resistors on top of the caps to keep them discharged.

I believe most microwave oven caps have a built in resistor.

[DavidEAQ]

Capacitor function.

Hi, I want to know what is the functionality of the capacitor C1 in this circuit.
I learned that a capacitor in AC is like a short circuit, but it depends of its farads.
I've got this circuit with a 80mF capacitor and before of connecting it, I tried to simulated it(with PSIM) to understand what the capacitor does, but I found that it does not anything. The capacitor is too big and it's like a short circuit, but I can't be sure 'cause as I mentioned before, I don't understand its fuctionality.

[Duncan]

A MythBuster's Glass Shattering Montage - YouTube

which Is In this article written about the same system

Capacitive Battery Charger - John Saves Energy

I concur fully .. but then I found a battery freezing once on the 3BGS system .. scary. Or at least a little odd I certainly knew something bloody funny was happening.
The effect is called by some "sympathetic resonance) .. in other situations "cognitive resonance" it is not an effect of the sine wave and harmonics but rather the linear wave .. (you know that one that doesn't exist.) and overtones. Neither is this the action of a fundemaental rather more like this I suspect

Marcus Reid Crystal Converter Battery - Casimir Effect - Part 1 - YouTube

[ewizard]

I believe most microwave oven caps have a built in resistor.

You DON'T want to assume that as these things can be lethal. Most of the ones I have do NOT have a built in resistor.

[totoalas]

Hi
Check out Electronicsnmore YT 5 -10 amp Capacitive dc charger for 110 v v ac only
for 220 v hope somebody can alter this design
thanks

[vidbid]

Capacitive Charger Experiment

[VIDEO]https://www.youtube.com/watch?v=FSDmzDuJ7HI[/VIDEO]

https://www.youtube.com/watch?v=FSDmzDuJ7HI

Experiments with capacitive reactance as a means of producing a simple constant dc current source from AC mains input. Usefull as a backup pack charger.

Variable Voltage Battery Charger - DIY Electric Car Forums

Be careful with this type of circuit.