My local electronic supply shop cant supply me with a 13,600μF capacitor!
Is there any other way I can do this.
Ive been reading that maybe I can use a LM 555 Monostable Multivibrator or a 555 Pulse Generator Circuit?

 

My local electronic supply shop cant supply me with a 13,600μF capacitor!
Is there any other way I can do this.
Ive been reading that maybe I can use a LM 555 Monostable Multivibrator or a 555 Pulse Generator Circuit?

Yes, but it's a lot more complicated.
It will require one or two 555 circuits plus a few transistors, plus some resistors and capacitors.

Where are you located? You can order the caps from various suppliers as shown here.
But if you really want a 555 circuit we can generate one for you.

Below is the LTspice simulation of the circuit using capacitors.
The simulation shows that you can get a pulse at the relay coil that stays above 9V with a 11.2V input for over 100ms with a 10,000μF cap.

 

Thank you so much for the circuit, great help.
One more thing, reading the instructions for the BMS I found this:
Note: when switching inductive loads like a relay/contactor, make sure there is a protection against flyback of the coil. A simple example is the flyback diode parallel to the coil.

My question,
What type of diode and how do I place it into the circuit diagram that you sent me

Again thanks so much.

 

Here's an alternative circuit. More components, but eliminates the need for huge electrolytic caps.

 

What type of diode and how do I place it into the circuit diagram that you sent me

It's not really needed in that circuit since the coil current will be essentially zero when the relay switches to the alternate position.
But if it makes you feel better you can connect a 1N4148 or 1N400x diode (two total) across each coil (anode to ground).

 

What stops the Capacitors from recharging and sending another pulse?
I have constant power coming from the relay on the BMS when it gets turned on and depending on the situation it may be powered on fro days.

Ive included here a picture of what I think you say I build.
Is this correct?

 

What stops the Capacitors from recharging and sending another pulse?

It charges as it generates the pulse and stays charged as long as voltage is applied from the BMS relay.
It has to be discharged through the resistor (by the BMS relay changing states) before it can be charged and generate another pulse again.

Ive included here a picture of what I think you say I build.
Is this correct?

Looks okay to me.
(You should place dots where the resistors and diodes connect to BMS relay pin 2.)

 

You can do this simple excercise to see what capacitor you need - take a bench power supply and a 470uF capacitor add a series resistor of 1K between the +ve lead from the bench power supply to the +ve of the capacitor. So now you have a 470uF capacitor being charged with a bench power supply and a 1K resistor in series.

Take some wires from the capacitor and momentarily short these onto the relay terminals. Now you have a starting point for changing the state of the relay and the power supply needed for this by altering the bench power supply.

Use a micro like a pic and a 100uH inductor and FET to make a boost charger for the voltage required and use a H-Bridge to trigger the relay into the required state.

 

use a H-Bridge to trigger the relay into the required state

You don't need an H-bridge since the relay has two separate coils for set and reset.

 

Ok - then that makes it simpiler. Use 2 x PNP transistors or FET's to drive from the +ve of the cap into both the coils. Ground the common of the coils,

 

Gidday Forum,
Im needing to control a Latching relay that is operated by a pulse.

Im using it to disconnect power from my solar regulator to my LiFEPO4 battery when it reaches its full voltage, and is controlled by bi-stable relays on the BMS.

I need a circuit that is powered from the relays on the BMS to send a pulse to operate the Latching relay.
Im looking for something that will not consume much power and once the pulse is sent doesn't consume anything.
The BMS relays are 12V@ 2 amp

I want the pulse to happen when the relay comes on and only once and then reset when the power goes off so its ready to send a pulse again when the BMS relay is powered on again.

I will include pdf details about the Latching relay

Thank you in advance
Kryz

You need a pair of mono-stables (one shots), driving a MOSFET. Go to www. lInear.com and download LTC6993 datasheet along with TimerBlox free design software. All you need is to fill a questioner - grigger by leading or trailing edge, output active low or high, pulse duration. TimerBlox sw will produce a circuit with all component values. This IC is in tiny 6 pin SMT package and does timing functions without any caps-just by resistors. It also features extremely low consumption.
Also download the free LTSpice sw and then simulate the intended circuit. If you need assistance - contact me at <SNIP>

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