12V spike suppression

Thread Starter

tal mann

Joined Apr 23, 2015
16
I've got a 12V automotive electric battery master switch circuit and need a spike suppressor like this one (link to suppressor). I'd consider buying it except the postage and import duties are adding up, so I'd like to make one. It looks like a ceramic wire-wound resistor and possibly a diode under that heat shrink.
As I understand it, a TVS is often used to limit voltage spikes and I've read a resistor can protect the TVS from excessive voltage spikes. I've got a 1.5KE22CA TVS (spec attached) and wondering whether a 3.3 Ohm 10W resistor (eg this one) will do the job.
If this is correct, should I wire the TVS and resistor in parallel or series?Smtkvar (A).png1_5KE22CA TVS.png1094_3414362.jpg
 
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LowQCab

Joined Nov 6, 2012
2,650
A Big-Fat-Electrolytic-Capacitor is the only additional part You need.
The most economical way to do this is to purchase a
1-Farad-Capacitor that is intended for High-Power Car-Stereo-Systems.

Also, putting multiple TVS-Diodes,
one on each Large-Inductive-Load,
might be useful if You are having serious Spike issues.

Make sure that your "Battery-Disconnect-Relay" is
a "Continuous-Duty-Solenoid" rated for at least ~300-Amps.
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MisterBill2

Joined Jan 23, 2018
13,808
A series inductance can help a lot. Consider that a shunt suppression device is acting as a load for that spike. Now consider the internal effective series impedance of the alternator, which may deliver 12 volts at ten amps and only drop 0.1 volt. That is much less than one ohm. But the effective internal series impedance of the protector is several ohms.
But if you have a series inductance blocking the spikes, the impedance is greater as the effective frequency of the spike increases.
 

Thread Starter

tal mann

Joined Apr 23, 2015
16
I wondering if I may have got something wrong. When I considered the resistor, I was thinking about the surge protection for the conventional 'big red key' battery kill switch to deal with the residual current from the alternator. The circuit '1-1' circuit is closed when the switch is off.
071704_wiring_diagram_1.jpgI am now thinking the critical issue is that the surge protector should not be a ground path unless the voltage goes over the safe threshold, i.e the spike, so I'm thinking a zener diode may be a better option.
________
A Big-Fat-Electrolytic-Capacitor is the only additional part You need.
The most economical way to do this is to purchase a
1-Farad-Capacitor that is intended for High-Power Car-Stereo-Systems.

Also, putting multiple TVS-Diodes,
one on each Large-Inductive-Load,
might be useful if You are having serious Spike issues.

Make sure that your "Battery-Disconnect-Relay" is
a "Continuous-Duty-Solenoid" rated for at least ~300-Amps.
LowQCab: Ok. Thanks for the advice about a 1-Farad-Capacitor. I've got some reading to do. Not sure if the continuous duty requirements are anything like 300 amps: a starter for a small 4 cylinder, smallest alternator I can run, injection including fuel pump, a few gauges and brake and tail lights.


________
A series inductance can help a lot. Consider that a shunt suppression device is acting as a load for that spike. Now consider the internal effective series impedance of the alternator, which may deliver 12 volts at ten amps and only drop 0.1 volt. That is much less than one ohm. But the effective internal series impedance of the protector is several ohms.
But if you have a series inductance blocking the spikes, the impedance is greater as the effective frequency of the spike increases.
Ok Ok. Now let me get my head around this. I was thinking that in worse case I'd have to kill the engine at peak revs, eg crash, and throttles jammed open, when the alternator may be producing say 45 amps. Am I correct in my understanding that R = V/I means 0.30 ohms at 13.6 volts and 45 amps and a lower current might be approaching 3 ohms 12-14.4 volts at say 5-ish amps.
 

LowQCab

Joined Nov 6, 2012
2,650
If You had made it clear that You were setting up a Power-Kill-Switch on a Race-Car
you would have received more appropriate information.

Do You actually know that there is a problem with Electrical-Noise/Spikes ?,
or are You just worried about the possibility ?

If You use a Solenoid that is under-rated, You run the risk of welding the Contacts together.
A generic Starter-Solenoid is NOT rated for continuous-duty operation and
the Coil will overheat and eventually fail.
( Ask me how I know !!! )
Continuous-Duty-Solenoids cost ~3-times as much for several reasons.

The Alternator may be switched-off by a similar, or identical, Continuous-Duty-Solenoid
wired to break the Heavy-Output-Wire coming from the Alternator.
Any other Wiring to the Alternator may be left "as-is".

2 Solenoids set up this way will instantly kill all Electrical-Power in
the Car, when the Power is removed from their Coils.

You are very unlikely to have any serious Electrical-Noise/Spikes in a Race-Car
where the only Electrical-Loads are the Ignition-System,
an Electric-Fuel-Pump, and maybe some Running-Lights.

If You are running a Fuel-Injection-Computer, simply install a single 10,000uf Capacitor
on the Main-Power-Supply-Wire feeding the Computer to protect it.

The TVS-Diodes won't hurt anything,
but are probably over-kill, and unnecessary,
unless You have some really unusual equipment installed.

You can install one on every piece of equipment if You like.
The more Diodes You install, the more Current they will collectively handle.
You can do this with Capacitors as well,
but the Capacitors must be kept reasonably Cool for a long life-expectancy.
NO Electrolytic-Capacitors under the Hood !!!
If You use Capacitors,
it's a good idea to make sure their Voltage-Ratings are
~25-Volts or greater for the most reliable operation and life-expectancy.

Motors, like Electric-Fuel-Pumps, or Radiator-Fans,
may be quieted-down ( Electrically ) by using a stack of
Ceramic-Capacitors of various sizes ...... 1uf, 100nf, 10nf, 1000pf, etc, .
The Ceramic-Capacitors, if used,
need to be mounted as closely as possible to the 2 Motor-Terminals.

But You probably don't need any of this "Spike-Protection" at all.
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MisterBill2

Joined Jan 23, 2018
13,808
I evidently failed to be clear enough: The inductance for spike protection needs to be in series with the load that is being protected, close to the load, NOT at the battery. For the battery disconnect there is no need for surge protection, automotive batteries protect themselves.
Also, an "alternator Surge" happens when the load is suddenly removed. The scheme for reducing that is in the arrangement of the circuit, so that the alternator charging current flows more directly to the battery, and the current for everything else flows from the battery in a different wire, and the cranking current flows in wires only used for the cranking current.
In an actual race car, though, the alternator if it is even used, is not delivering much current, because alternator HP takes away from wheel HP.
And in any crash it is the battery that is the dangerous energy source. The engine kill switch stops the engine, the big red button disconnects from the battery. At least on circle-track race cars. And under crash conditions any spikes are not the concern.
(Probably not much of this applies to battery-powered race cars.)
 
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Thread Starter

tal mann

Joined Apr 23, 2015
16
Thanks for your replies. Sorry if I was unclear. In the original post, there's a master switch battery circuit diagram which shows a 'surge suppression unit'. The battery master switch is used to power on and off, and can be used as a kill switch. The main element of it is a TE V23132 high current relay which is commonly used in motorsport for this purpose.
Link to suppressor in the original post is for a "Battery Cut-Off Spike Suppressor Unit" which is shown in the diagram.
As far as I know, all similar cut off switches for motor racing use a spike protection and pretty well all of them are located at the cut off switch. In the past, I've used the big red key style switch which used a 3.3 ohm, 11W resistor. this resistor alone will not be sufficient.
I was under the impression the suppressor deals with any spikes when it is switched off.
I also understand that spikes will come other sources but it's these suppressors (links below) I'm trying to understand or deconstruct.

Example 1
Example 2
 
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LowQCab

Joined Nov 6, 2012
2,650
A TE-V23132 is a 50-Amp-Relay,
this may work with reasonable reliability for an Alternator-Disconnect,
but it will be just barely adequate in that role.

Putting this Relay between the Battery and the Starter will result in eventual failure.

The Spike-Suppressors are probably somewhat useful, and won't cause any problems,
but it's questionable as to whether or not You actually need them.
A ~10,000uf, 25-Volt Capacitor placed on the Power-Input of any,
possibly sensitive, Electronic-Equipment, will provide better protection.

This is what You need for a Battery-Disconnect-Solenoid ............
https://www.delcity.net/catalogdetails?item=8000370
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Solenoid .png
 

Thread Starter

tal mann

Joined Apr 23, 2015
16
A TE-V23132 is a 50-Amp-Relay,
TE specs say it's 130 Amps continuous and 300 amps current switching. I appreciate the advice and will look at that, but be that as it may, I'm still no closer to understanding what the suppressor units I link to does or its circuit.
Asking around, I'm wondering whether the suppressor is required to shut it down instantly. The suggestion is that the master relay may remain closed for a brief moment after the switch has been turned from "on" to "off" due to alternator load dump and, scratching our heads came up with this two diodes, one of which is a zener diode in this arrangement.
zener.png
 

LowQCab

Joined Nov 6, 2012
2,650
My bad .........
This is the Result I got when I did a search for TE-V23132 ........
https://www.te.com/usa-en/product-9-1415001-5.html
I should have read more carefully,
the page states twice "" >50-Amps ""
I didn't look further for a proper Spec-Sheet.
Sort of an odd way to describe a Relay with a much higher Current rating.

The Spike-Suppressors are for handling heavily-Inductive-Loads,
one of them is the Alternator its self.
If Power is abruptly removed from the Regulator which is controlling
the "Field-Winding" of the Alternator,
the resulting collapse of the powerful Magnetic-Field around the Field-Winding
will cause a serious Voltage-Spike at the Output-Stud of the Alternator.

With no Capacitance in the Wiring-System to absorb this Spike,
the Output Voltage of the Alternator may go as high
as ~40 to ~50-Volts for an extremely brief period.
This is enough to smoke any unprotected Electronic-Equipment.

Zener-Diodes, and/or, TVS-Diodes are often used to "clamp", or "short-out",
these Voltage-Spikes to a supposedly "safe" level,
usually reducing the Spike down to maybe ~16 to ~20-Volts.

If the Voltage-Regulator inside the Alternator remains powered by a large
collective Capacitance elsewhere in the Wiring-System, ( for a very short period of time ),
the Powerful-Magnetic-Field generated by the Field-Coil will
collapse much more slowly and smoothly, and therefore,
it will not create the usual severe Voltage-Spike at the Alternator's Output-Stud.

If a large Electrolytic-Capacitor is installed on the Power-Input-Wires of
a piece of Electronic-Equipment,
any Voltage-Spikes, that are generated anywhere in the Wiring-System,
will be reduced-down to almost zero when they hit the Capacitor.

Capacitors act like an extremely fast, but small, "Battery",
they can be Charged-up almost instantly,
and they also absorb Power while they are being Charged,
( that's why they can instantly "absorb" a short Voltage-Spike ),
but they don't have very much total Power-Capacity,
so they can only keep things Powered and running for
less than a maybe half a second or less,
( depending on their size,
and the total number of Capacitors that are installed in the Wiring-System ).

The amount of protection that You will get will depend upon the Specifications,
and the quantity of,
TVS-Diodes, and/or, Capacitors,
that are installed throughout the Electrical-System.

Most high-quality Automotive-Electronic-Equipment will come with built-in Spike-Protection,
so I tend to prefer using Capacitors to eliminate any Voltage-Spikes,
since they also reduce "Electrical-Noise" which can
affect the proper operation of some Electronic-Equipment.

TVS-Diodes, and Electrolytic-Capacitors,
can both be "remote-mounted",
but either will provide the greatest protection when connected,
as closely as is practical, to the device that needs protection.

This is a premium Electrolytic-Capacitor ..........
Roughly ~$6.oo each.
https://www.digikey.com/en/products/detail/würth-elektronik/860010483029/5728189
Heavier-Duty versions with Screw-Terminals are also available, but cost more.
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Capacitor 10Kuf .png
 

MisterBill2

Joined Jan 23, 2018
13,808
The two links pointed to products for sale with only a very general statement of the benefit.
Normally a correctly placed shunt type transient suppressor would be connected across the device it is intended to protect. Connecting at that point keeps it as far from the transient generating device as is possible, so that the current driving the transient voltage will encounter as much impedance as possible. So now the question is what devices are to be protected?? And just what sort of transients are being generated by whatever devices generate them.
 

Thread Starter

tal mann

Joined Apr 23, 2015
16
Ok thank you, LowQCab and MisterBill2 or explaining it clearly and for persisting. Will the capacitors may retain a charge long after power is removed from a circuit and is there a risk from this stored energy?
I suppose the best way forward is to get it up and running and see how it goes.
 

MisterBill2

Joined Jan 23, 2018
13,808
Consider that the system voltage will normally be around 13.5 volts during normal operation, there would be no recognized shock hazard from any stored charge. Then also, consider that the current drawn by connected devices will be at least a few milliamps, there will not be much charge left on the capacitors at all when the system is switched off.
Working with a 12 volt system that is energized does present the hazard of damaging currents in the event of an accidental shorted circuit.
The charge left from any transient voltage spike will not be a hazard because with higher value capacitors the leakage current increases rapidly as the rated working voltage is exceeded.
 
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