Will this Circuit Allow Correct Battery Charging?

Yeah, that looks pretty weird, but for other reasons.

There's not enough information here to say the it won't work but I will say that likely it will work.

If the UPS charge circuitry controls the charge by monitoring the battery charging current (many but not all do) then regardless of the voltage drop across any pair of diodes the correct amount of charge will be placed in the battery. If the UPS monitors the voltage across the battery at the UPS node then the battery may not become fully charged as fast as normal but it will eventually fully charge. In this case, one can likely identify the charge sense components from the charge providing components. Running the sense connection to the battery directly will likely fully restore charging time. Now most UPS driving circuitry are designed to produce full AC power with the battery at 75% output voltage. So in discharge the ammeter and diode drop will again not be significant.

I do see now a small typographical error that might be misunderstood. The leads of the ammeter only connect to the diodes of the bridge. The negative lead of the ammeter is not directly connected to the positive side of the battery. (I do believe that this typo was discussed in the earlier posting.)

As far as I can see the charging circuit is 2 times "forward voltage drop" from the batteries and no sign of ....Running the sense connection......which I agree would work wonderfully...sense wires are brilliant for correction of bad circuits like this one and would solve the problem for the question from which this is derived.

For me if the charger is looking at a battery with a volt drop in between in will not charge it correctly.

I mean why by a battery charger and fit 2 diodes at the output ?

I knew it, you do not even know what a Kirchoff loop for nodal analysis is.

Have you decided to make this some kind of personal vendetta?

(For anyone who missed it, my drawing was copied from a post in this thread).

Yes, you seem to be correct, not having received any GAs in 130+ posts. Is anyone surprised?

Short answer is no.

There is a longer answer but I haven't the time to type it, and I'm not sure that you would comprehend the answer..

I did answer your question in response #10.

Which after posting I decided there required a more considered response.

But like teaching pigs to sing and post turtles I will concede to the diminising returns for effort.

Another new (electronic?) component: an Ampere meter (gauge).

Did you notice that this circuit allows the A meter to move in the same direction while charging the batteries as well when unloading the batteries.

The diagram is not complete, that is why I can't say more if the circuit is bad.

What I see is a nice way to use a regular A meter instead of one with a center zero and a needle that moves in 2 directions.

An Ampere meter is a winding (magnet.) arrangement not another new component.

Rectifiers tend to pass current in one direction.

Did you notice that the circuit would work perfectly well by including 2 more diodes ?

{The diagram is not complete, that is why I can't say more if the circuit is bad.}

The circuit was the one supplied it is complete as supplied !

I am well aware that GAs are as much a popularity contest as anything else. The point I was responding to was portugalphilip's suggestion that JohnDG might never have voted him any GAs. So I took a look. Apparently portugalphilip was correct, not only about JohnDG, but also any other possible pair of votes. C'est la vie.

Taken out of context, yes this circuit is NOT ideal. However this circuit (and additional information you have not included) relates (as you know) to the following thread in answer to the question (simplified) "how do I connect an ammeter in series with a UPS battery so that it doesn't go backwards when the UPS charges the battery?"

http://cr4.globalspec.com/thread/56177

The answer (in the form of the picture), AND the additional information in posts further explaining "how to connect the original poster's existing ammeter to get it to work" circuit in the above link (again which you have not included) clearly indicate the advantages and disadvantages of the circuit. As for your comment that is a bad circuit, it is actually an acceptable circuit (again when taken in context). It may not be as fancy as a hall effect transducer (and associated electronics) but it is very simple and very cheap and will work for many applications (including the original poster's existing ammeter). The most accurate, expensive and complicated solution is sometimes (more often than not) the best (and you can take that from an actual Engineer!).

Personally I would have just placed a set of change over contacts to mechanically swap the ammeter polarity (hence avoiding some of the disadvantages created by the diodes, but creating additional disadvantages). Which is better, again it depends on the specific application as neither are ideal for all situations (the "perfect" circuit).

Do you just have a problem with the two diode voltage drops potentially interfering with the charging? Perhaps you should do what the rest of us do and reply to the specific question thread and post response (which you have already done) rather than starting a new thread, that or at least provide more information.

Surely there are diodes around with a very low voltage drop that would have little noticeable effect on the voltages.....years ago Germanium was the only answer, but today there are some better answers I feel....Schottky diodes?

See here:-

http://www.st.com/stonline/products/literature/ds/5511/stps120l15.pdf

Not completely charging a LA Battery will actually prolong its life and improve the efficiency......only charging to about 70% of the capacity is the "sweet spot" there!! You just need to increase the battery "size" by at least 30% to cover it....

I agree with you about a changeover relay, you win some and lose some.....swings and roundabouts!!

I personally would still go for the low drop Schottky diodes....they are available in quite large amp sizes....

Have a great day.

There is some diodes with very low forward volt drops.

If this type of circuit were to used I think maybe you could arrange the rectifier part from a FET (with associated circuitry.) and there is some FET's that have an on resistance of well less than 1 ohm.

From the original post of the advice given The Relay arrangement would be the best answer to the how do I connect a meter ? part but the question also asked what components would I connect ? so I gave my opinion that a hall effect device would be my choice.

Also I was surprised that someone would suggest such a poor circuit for a battery charging system. I mean are we not supposed to be engineers and realize the circuitry we employ.

It may not be as poor as you think, LA batteries are voltage driven charging, so as long as you don't "Overcharge", the charger remains fairly simple.

If the applied voltage was say 13.2 volts to a nominal 12 volt LA battery, no overcharging would take place......nor would the battery be completely full either, as I said before, only about 70% full.

But it would not gas (lose water), it would not heat up and would have a remarkably long life....as long as its not "over discharged" either, or its a leisure type where it does not matter if its deep discharged.....

{ It may not be as poor as you think }

I think it is really poor.

Yes overcharging a battery is really bad.

Yes batteries can even explode if gassing takes place.

Yes there are some batteries that don't care if they are deeply discharged.

But for me a battery charger is to charge batteries and not run circuitry between it and batteries.

I have no problem with this circuit if a second rectifier is fitted (or 2 shortable diodes.)

are fitted to the circuit to raise the battery reference by the same amount as the ammeter rectifier.

I do know why it was not included in the circuit in the first place and then I would have given it a good vote instead of question it.

Regards.

Philip.

As we have not been informed about the value of the UPS voltage, that is only speculation.....

As I said before, if the voltage is correctly set up, no other circuitry or components are needed to charge correctly and not overcharge.......its why I use LA in my caravan and no other....

Please help me out here - you seem to have come across a new electronic component. What is a Shortable Diode?

Regards.

John.

A diode with a relay across it !

A diode is a P-N Junction and a relay is a device for connecting and disconnecting conductors.

If you power the coil of the relay with a voltage current source you can make the relay "short" out (bypass.) the diode and when the coil voltage current is removed make operative (allow to be functional as a diode.) or the other way around as relays have NO and NC contacts which means they are Normally "Open" or Normally "Closed" which means that they are either conductors or non conductors when the coil is under normal conditions which is generally understood as No coil voltage to the relay.

Diodes have generally 2 pin outs and Relays generally have more than 2 pin outs.

Pin outs means the amount of electrical connections you can make with the device.

So a Shortable Diode is a diode that you can make like a piece of wire or use as a diode.

Cumprementos....Regards.

Philip.

There - I gave you a GA. Best laugh I've had for a while. Thanks.

Andy Germany

Who told that charging a battery to only 70% of its full capacity will increase its life time ?

If you read some in depth manuals on LA Batteries, you will find references to not gassing = longer life....any voltage over 13.2 volts (for a nominally 12 volt battery), WILL cause gassing.

Also (depending upon the type of L.A.B.) going below 12.6 volts for extended periods promotes sulfation, another killer of car type LABs...

Keeping a battery between those two values promotes longer life, which is why some cars have short lived batteries and others longer lives.....

I am actually testing this fact with a 120 A/H battery that I bought in 1999 for my caravan, its still going strong!!! And has only once had distilled water added.....about 3 years ago!!

I'll let you know when it "pops its clogs".....if I knew who the hell you were Mr (Mrs?) Troll.....

Well ,don't go above 13.2V and you still able to charge the battery fully.

But to charge the battery to only 70% of its full capacity promotes partial sulfation for the 30% of its capacity which left with no charge.

The problem is that my circuit was sketched out in response to a specific question, and is presented here out of context.

I'd be the last person to argue that it is a particularly "good" solution, but it is, I believe, the simplest answer to the original question.

As has been said before many times (elsewhere) "If I was going there ... I wouldn't start from here".

I'm done, and like Andy I'm out this singing lesson too

Not unless you have one of those new-fangled AC batteries... Er, uh, NO. Although it will likely cause it to blow up, which could be fun. Please provide video!

Yeah, I missed the + sign on the mysterious ups box. But not knowing any more than is presented, there is no way to answer if it will work or if it will smoke or do nothing or do something poorly.

This circuit will work. We need to consider the forward drop of two diodes. Hence the charging voltage to be adjusted accordingly. Also, when the UPS takes power from battery, we will loss power in two diodes. I dont think this is a good design. But it will work.

Still working on that reading thing I see...

how is it anyone could make a determination, of the quality of the circuit, [which could be adjusted to compensate for the drop, for all we know] when the charger itself is a black box, with no specifications whatsoever.

you have also managed to run off what little support you had on the other thread...

Good job on extending the life of a thread started by a guest, who probably didn't come back & read any of the 75+ replies to his query

The ammeter will indicate the amount of charge or discharge but not indicate which. You really need an ammeter that reads both + and - and get rid of the full wave bridge.

Hi portugalphilip,

The UPS typically will have a modified sine wave output containing significant harmonic content. The ammeter will display something but not RMS. Alternating current is routed to the battery causing heating, but no charging.

Regards,

Luther M

Keep up, Luther !

The ammeter & diodes are between the UPS electronics and the UPS battery. There is NO AC PRESENT in the circuit shown! You may be getting confused by the AC symbols on the bridge.

(This is what happens when someone takes a post (in this case, a posted circuit) from another thread and starts discussing it out of context ).

You only say it is a UPS Battery charger it may provide a pulsed DC charging current which might be what the guest is talking about but yes...an AC Battery...that would definitely be a "New Component"......I must get down the patent office soon. !!

You may get a good answer soon :)

short answer: YES as long as polarity of source is maintained as shown.

Maybe I'm missing something here, but the circuit will not work because the ammeter is connected as a load and the battery is not. The battery will see an alternating current. The battery should be wired to the output of the bridge at the nodes of the ammeter. The ammeter should then be in series with one of the battery leads. No?

P.S. - Most UPS that I'm familiar with are AC.

It depends at which point in the circuit you are working with......all UPS batteries are DC (we have yet to invent an AC battery....) Understood????

Abuse/Attack:

This post was deleted because it was an attack on another user. Please review the CR4 Site FAQ.

Nothing clever in this circuit,two diodes of the four diodes of this bridge rectifier have no use, wasting money. This circuit is just equivalent to single diode connected in series with a meter.

What is clever you talking about ?

DUUUUHHHHH!

Think about charge and discharge.

Think about CURRENT direction.

Then you will see that the meter (not being a center zero, or digital) can show both charge and discharge on the meter needle, without wrecking it!!!

GA from me.

Yusef1, we don't always see "eye 2 eye", but I must compliment you on your post, simple but stunningly correct!!!

Many thanks.

I am sure that John DG will also be a (little) bit grateful too!!

The circuit will work.

The bridge rectifier only provides steering charge and discharge current. Schotky diodes may not be necessary as the DC/AC UPS inverter may operate with 11VDC.

The UPS does not source AC.

The ammeter will indicate both charge and discharge currents. No need for center scale zero and such indication. Every UPS I've ever seen has LED indicators for like "Standby" or "On/On-Line" mode.

Are we clear yet?

You guys have beat this one to death. More like to a pulp.

Remains a mystery as to why inductance and "Q" was brought in. Think by the OP.

The battery will supply DC current into the UPS , and the battery will be charged by a battery charger.

No it will not it is a battery charger with the charger looking at a volt drop between it and its intended target.

Please read the title of the question and then any replies.

Is there any way I could tap the heat out of this discussion to run a Rankine cycle? Might be able to generate some electricity for this wheatstone bridge circuit battery charger.

Just remove the bridge rectifier form the circuit and keep the meter , will be the same.

Not if its an older "needle" type meter with zero on the LH side.......think!!!

If you had a clue what you are talking about you would have posted with your "real" CR4 name, instead of jest guest!

I am talking about a meter with needle in the middle so you will be able to know if the current charging or discharging.

WOW! What a post! I'll be sure to mind my p's and q's next time I have a query.

My simple answer is NO. It will NOT permit the UPS to "see" the battery voltage correctly.

My reasoning is that the breakover voltage of the diodes will introduce a 1.4 volts overcharge (if it's a standard silicone rectifier) AND an under-discharge cutoff with the same error.

The ammeter WILL function but only if charging or discharging and the readings will be the same polarity whether discharging or charging.

If I wanted to monitor the current to or from the battery, I would use a center zero 12 vdc ammeter (suggested in previous post). Though the coil resistance of the mechanical ammeter WILL introduce a slight voltage drop, I don't believe it would be significant enough to interfere with the ups voltage sense circuitry.

I purchased a DC clamp on ammeter that'd work great but at 300 bucks, well...

Yes you are correct.

In reply to : My simple answer is NO. It will NOT permit the UPS to "see" the battery voltage correctly.....That is the whole point of my post.......The circuit is junk...why destroy you batteries just to see a reading on a cruddy ammeter...do it correctly and do as you do and buy a hall effect meter and bingo you have your readings and a useful tool also instead of an inaccurate meter / bad batteries and a possible loss of the functionality of your system.