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Help Safty Circuit Required

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Gregory

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I Have incounted a problem with a 240V AC invertor to 12 Volt DC.
The Battery was not responding to the 25Amp ( 14.5 Volts Dc) charge from the invertor.
This caused the battery to boil and the Invertor continually trying to charge the Battery at this Rate.
The wires wer very hot and discolored and this could have led to a fire.
Is there a circuit digram of a device that will shut down after a predetermined time if the charg continues at the 25 Amp rate.
Or can some one help me out with a suggestion of a circuit
There was not a short Circuit.
 
Hi,

There are unclear information in your post.

An inverter is something that convert low voltage into high voltage. A charger in your case is something that convert high voltage into low voltage suitable for charging battery. You need to tell us exactly.

Other questions like:

1. does the problem suddenly occurs(or does it work in the past) ?
2. is the charger a regulated charger(with active electronics components) with voltage and current control or just a simple one using transformer and bridge rectifier ?
3. is the battery in good condition ?

need answers too.
 
As elbc suggests, we need to know much more.

Note that if a conductor (wire, other) has overheated to the point of discoloration and the wire is outside of a protective (presumably metal) enclosure then it would seem that you need to take a close look at the overcurrent protection scheme. Often within equipment electrical enclosures there might be failure modes that would deliver currents capable of melting wires, etc. I think that the enclosure is or should be designed to account for this. Once conductors exit the enclosure then good practice and most often, rules and regulations require that some means be provided to keep the current in conductors to a safe value. Fuses, fusible links and circuit breakers are some ways to do this.

Note that sometimes overheating of conductors can occur because of loose connections at junctions or terminals. This can create the heat you describe without opening overcurrent protection.
 
Reply to question ( safty Circuit )

Thanking you for your Quick response.My mistake it is a battery charger.
It is used for charging the battery which runs lighting and other equipement.
The battery will not recover from being discharged but the charger tries to recover the battery.charging at 25Amps Max
This problem has not been encounted befor.
I tested the charger and it shuts down when the battery reaches full charge.
Ther charger is performing as it should.
The charger is regulated With voltage and current control( this is not a simple unit )
I see that the circuit was still completed but the battery demanded the full Current supply. and the unit has no way of sensing this problem as there is no continus current protection protection at 25 Amps
 
Maybe the battery has become sulfated, and is now unservicable. Often when storage batteries are deeply discharged or sit unused for long periods ( no charging or load ) they sulfate, resulting in a condition where they never reach a full voltage per cell. They act partially shorted, and can draw huge currents under charging, yet do not retain a charge.

Some chargers check the battery voltage to determine its state of charge, shutting off when the battery reaches the correct voltage. Some chargers are more sophisticated in sensing when a battery is full, pulsing the current, letting the battery rest, then check voltage. Others simply apply a fixed voltage, and when the battery reaches that voltage current drops off, by simple Ohms law.

Yours sounds like a fixed voltage charger, and if the battery never comes up to that voltage, it will continue to draw a large current from the charger.

I hope this battery is a "deep-cycle" type battery that is able to withstand being completely discharged. It sounds like yours is, but I am not sure. If it is not, it may be damaged.

Check the condition of the battery. Is there enough electrolyte in each cell, measure the cells with a hydrometer, check their voltage, etc. Depending on the battery type, this may or may not be possible.
 
Reply Help Safty Circuit Required

The battery was standing for a long time befor any use.
( ie 2 Months )
What you have written is correct Zevon8
The battery is a deep-cycle
The charger has a inbuilt cutout where by when it draws full current for 4 hours it shuts down but this did not happen.
I require a circuit to bild a backup device to be able to give me a more positave result if this fails again because the unit is used in my mobile home where I will lose every thing I own.[/b]
 
Cheapest and easiest could be a simple light timer. The type that you plug into an outlet, and set the time of day to turn on, then off. You plug what you want to control into the timer, in your case, the charger.
 
if the battery cannot be left on trickle,
then maybe an over-temperature trip could be used.

One that stays out, you wouldn't want it to keep
on trying every time it cooled.
 
zevon8 said:
Maybe the battery has become sulfated, and is now unservicable. Often when storage batteries are deeply discharged or sit unused for long periods ( no charging or load ) they sulfate, resulting in a condition where they never reach a full voltage per cell. They act partially shorted, and can draw huge currents under charging, yet do not retain a charge.

Actually sulfation is the opposite. It coats the plates and makes a high internal impedance. It messes with charge cycles because a 12v battery can be charged to 11v then put it on a charger and it reaches 14.6v just due to the voltage drop across the internal resistance, and the charger shuts off. Then you try to put a taillight on it and it drop to 10v.
 
Would a 2o AMP circuit breaker with a orderable and visual indicator (Led ) do the job .
Would the circuit breaker work when the charge rate got above 20 Amps to 25 amps .
Would the circuit breaker work instant.
Thanking you for your help.
 
Eh Gregory,
If your charger circuit is stuffed and it sounds like it. It would be wise to through it out and replace it. They can't be that expense and it does pay to be cautious. As you say it's for your motor home why not consider buying a few solar panels and putting them on the roof. You'll find they will be worth the investment long term.

Hope this helps Bryan :D
 
Gregory said:
Would the circuit breaker work when the charge rate got above 20 Amps to 25 amps .
Would the circuit breaker work instant.

Circuit breakers have a characteristic tripping curve, and may take anywhere between 0.4 seconds and 2 hours to trip, depending on the current and type of circuit breaker. You have to select your current rating accordingly. The current rating on the breaker is the maximum current at which it will NOT trip. Go higher than that, and then you need to refer to the tripping curve to see how long it will take to trip. Typical Type C MCB's (as used in most electrical switchboards) will trip instantly at 7.5 times the rated current (so 150A for a 20A breaker). Type B is 4.5 times, and Type D is 12.5 times (used for motor starting) - Type A is generally unavailable.

I have given a typical tripping curve below. Horizontal axis is percentage of rated current, vertical axis is tripping time (in seconds).
 

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