discharge circuit, dump circuit

[Mrusten]

hello

im looking for a circuit that can remove access power from a battery, but i can not find it anywhere.
im not that competent in designing circuits so i wil try in forum.

maybe someone have a circuit that i can use.

i did not ask about safety, i did not ask about other ways of doing this, i only ask for circuit and discussing about discharge circuit please respect that.


ok i have a few "requirements" for way of function
no programming
pwm based discharge
pwm 0-100% (not critical can be for example 10 - 90%)
pwm start voltage adjustable if batteryvoltage 5v over start voltage =100% pwm
pwm start voltage adjustable dc240v - dc265v (example start 265,05=1%pwm 270=100%pwm
pwm ramp up and down slowly
pwm is limited by a current shunt adjustable from 1A to 100A
pwm frequency not critical about 3khz


explaining of circuit work:
start voltage adjusted to 240vdc
current limit set to 10A

voltage increase to 240,1vdc
pwm start 2%

voltage increase to 241vdc
pwm adjust slowly to 20%

voltage increase to 242vdc
pwm try to adjust slowly to 40% but the current limit stop and hold the pwm at 30%

voltage increase to 243vdc
current limit still hold the pwm at 30%

voltage decrease to 240,5
pwm adjust slowly to 10%

voltage decrease to 240
pwm stop

 

[AnalogKid]

What is your application? A 265 Vdc, 10 A battery?

ak

 

[Mrusten]

What is your application? A 265 Vdc, 10 A battery?

ak

no the 10A limit was for an example to protect the connected load

battery is 90kwh

 

[Mrusten]

What is your application? A 265 Vdc, 10 A battery?

ak

application is to bleed off the extra power to use it for something useful

 

[Mrusten]

here is a drawing to show what i was thinking,
offcorse it do not work bechause i do not have the knowlege to make it correct but the design or how to do should be possible this way.
240v is stepped down to 0v and 245v wil then be 5v, potentiometer is there to adjust the 0v from 240 to 265v and the 5v wil be 5v higher as in the first example.

0-5v is amplified by opamp, zener is there to pull down the voltage if the 0-5v should be higher than 5v.
0-5v pwm circuit 0v=0%duty 5v=100%duty.
pwm output have a pull down resistor to shut the SCR off when pulse is low.

shunt feedback the current via transistor and pull down the 0-5v if current is over setpoint by the potentiometer close to the shunt

then finally the battery and load is connected to the SCR input and output.

SCR is a NKT110-16A

 

[dr pepper]

I'm not sure I get it, however I dont think driving a thyristor gate with pwm will work as a thyristor on dc once switched on will remain on, a mosfet might be a better approach here.

 

[Nigel Goodwin]

I'm not sure I get it, however I dont think driving a thyristor gate with pwm will work as a thyristor on dc once switched on will remain on, a mosfet might be a better approach here.

It can be, and is done (an example is fork lift trucks), but NOT just with a single plain thyristor.

However, I don't get it either?, and as with many of these vague threads it's hard to know what he wants, what he expects, and what he's trying to do?.

In the theme of 'vagueness' the standard method is to dump any excess energy (from the source NOT the batteries) on to storage heaters.

 

[Mrusten]

It can be, and is done (an example is fork lift trucks), but NOT just with a single plain thyristor.

However, I don't get it either?, and as with many of these vague threads it's hard to know what he wants, what he expects, and what he's trying to do?.

In the theme of 'vagueness' the standard method is to dump any excess energy (from the source NOT the batteries) on to storage heaters.

the source is connected to the batteries and the normal loads are drawn from the batteries as well.
so for example solar is chargeing the batteries by 6kw
the normal loads are 3kw drawn from the battery.
then the battery wil be charged by 3kw and the battery voltage wil rise until charger shut off.

i want to use the free solar power for something useful and if the load monitor the battery voltage it wil adjust it self to the extra avalible power all the time.

as in my explaining, rise of battery voltage over set point = increase the load

i live in a cold area, i wil use heating elements in water storage tank to heat water with the free extra power

 

[Mrusten]

I'm not sure I get it, however I dont think driving a thyristor gate with pwm will work as a thyristor on dc once switched on will remain on, a mosfet might be a better approach here.

i have a large igbt somwhere also witch can be used

 

[Nigel Goodwin]

As it's solar, why such a high battery voltage? - much more common (and sensible) to use a much lower voltage, and all the control systems you need are freely available.

I went to a house a few years ago, the address was 'Mill Close' (bit of a giveaway) and it was the left hand one of a semi-detached pair. The original stream that fed the old mill on the site was actually dead on the centre line of the two houses, so they got together and installed a small water turbine - this provided 2KW of power, permanently, the stream came from underground and never dries up.

Despite the fact I was actually delivering and installing a washing machine, I spend a fair bit of time talking to the owner - they shared the output of the turbine, 1KW each, no batteries involved, and if the house requirement was under 1KW the excess power was simply sent to storage heaters upstairs (much like you're planning doing it with water). As far as I'm aware, everything used was freely available, and it's operation was totally transparent.

 

[Mrusten]

As it's solar, why such a high battery voltage? - much more common (and sensible) to use a much lower voltage, and all the control systems you need are freely available.

I went to a house a few years ago, the address was 'Mill Close' (bit of a giveaway) and it was the left hand one of a semi-detached pair. The original stream that fed the old mill on the site was actually dead on the centre line of the two houses, so they got together and installed a small water turbine - this provided 2KW of power, permanently, the stream came from underground and never dries up.

Despite the fact I was actually delivering and installing a washing machine, I spend a fair bit of time talking to the owner - they shared the output of the turbine, 1KW each, no batteries involved, and if the house requirement was under 1KW the excess power was simply sent to storage heaters upstairs (much like you're planning doing it with water). As far as I'm aware, everything used was freely available, and it's operation was totally transparent.

the high voltage is bechause the inverter is a UPS, 25kw and to save on losses thats how its made.
i already have the charge controllers to go with it, x2 for solar and x3 for wind

but yes its kind of the same goal as with the mill

my ups is custom made to priority to work from batteries if power is avalible there, if battery is low the ups wil use the city grid, switching is done without flickering in lamps

 

[schmitt trigger]

What I understand from the OP, and please correct me if I am wrong:

• The OP has a solar array connected to an UPS.
• The UPS sometimes does not draw the full power being generated by the array, I suspect in very sunny days.
• The OP wishes to use this wasted power in something useful.

As Nigel mentions, electric water heaters are by far the easiest way to use that free energy. And fortunately, water can store lots of energy per unit volume. And it is cheap.

 

[Mrusten]

What I understand from the OP, and please correct me if I am wrong:

• The OP has a solar array connected to an UPS.
• The UPS sometimes does not draw the full power being generated by the array, I suspect in very sunny days.
• The OP wishes to use this wasted power in something useful.

As Nigel mentions, electric water heaters are by far the easiest way to use that free energy. And fortunately, water can store lots of energy per unit volume. And it is cheap.

thats the case yes

 

[dr pepper]

Nige, yes I maintain Flt's amongst other things, they did use thyristors, switch off was done with capacitor discharge, lansing bagnall were well up on this.
For the past 15 to 20 years mobile plant have gone to ac motors with an inverter instead of dc brushed ones, maintenance is a lot easier.

 

[Mrusten]

Nige, yes I maintain Flt's amongst other things, they did use thyristors, switch off was done with capacitor discharge, lansing bagnall were well up on this.
For the past 15 to 20 years mobile plant have gone to ac motors with an inverter instead of dc brushed ones, maintenance is a lot easier.

could you draw to show how the discharge capacitor was connected together withsouronding circuit?

 

[Nigel Goodwin]

could you draw to show how the discharge capacitor was connected together withsouronding circuit?

Try googling it, or even searching on these forums (as it's been posted here before), but essentially you use a second (smaller) thyristor to switch a capacitor across the main thyristor, this momentarily stops current flowing through the thyristor (by shorting it out) causing it to turn OFF.

 

[dr pepper]

Heres an explanation.

SCR Turn OFF Methods: Natural, Forced Commutation

Different SCR Turn OFF Methods like Natural, Forced Commutation are explained. In Forced, Class A, B, C, D, E. Dynamic turn OFF Characteristics.

www.electronicshub.org