Hi and alternative mosfet help

[spec]

Hy GWI,

Ok got it. I will do a circuit that will provide 60 Amps and leave you to sort the battery side of things. Apologies for the confusion- I have been distracted by the Brexit referendum and the resignation of the prime minister. That is my excuse anyway. Good job Ron is around.

spec

PS: can you confirm that your battery voltage is 3.7V.

 

[gentlywiringit*]

This one . Yep, best excuse for a distraction if ever I've heard one! Forgiven

 

[spec]

Hy again,

How do you feel about having four IPB80P03P4L-04 PMOSFETs?

Just one circuit and one switch though.

spec

 

[spec]

This one . Yep, best excuse for a distraction if ever I've heard one! Forgiven

Thanks

spec

 

[gentlywiringit*]

4 would fit in the enclosure I have (with a little modifying)

 

[spec]

4 would fit in the enclosure I have (with a little modifying)

Great. Can you describe the enclosure- picture? Is the enclosure made of metal. If so what metal? And how thick?

spec

 

[spec]

The IPB80P03P4L-04 is not too expensive: £1.17UK plus VAT https://www.mouser.co.uk/ProductDetail/Infineon-Technologies/IPB80P03P4L-04/?qs=wK%2boHS4yu562EimsoDeBJQ== For example.

spec

 

[gentlywiringit*]

I have this enclosure, it's an aluminium alloy.. could be 7075 2mm thick where the fet's will have to be placed

https://cpc.farnell.com/takachi/cdm8524bk/alu-enclosure-black-112x70x35mm/dp/EN83763

 

[chemelec]

Possibly you can use the Enclosure as a Heatsink.
However it may need Electrical Insulation.

 

[gentlywiringit*]

It will have the negative side of the circuit in contact with the enclosure, a factor I can't change. It would need insulating.

 

[spec]

I have this enclosure, it's an aluminium alloy.. could be 7075 2mm thick where the fet's will have to be placed

https://cpc.farnell.com/takachi/cdm8524bk/alu-enclosure-black-112x70x35mm/dp/EN83763

It will have the negative side of the circuit in contact with the enclosure, a factor I can't change. It would need insulating.

Thanks,

New circuit will be posted soon.

spec

 

[spec]

Would it be OK if the resistor is connected to the +3.7V battery terminal and the other end is switched by NMOSFETs- as Ron suggested.

spec

Like this:

 

[gentlywiringit*]

Heres some spec on the display I have, it goes on to say that its not compatible with n channel mosfet as it will complete the circuit. It has p channel unfortunately.

Battery VoltageDisplays battery power icon.
1 Battery: < 3.2v displays empty battery. 3.2v-4.2v in 0.1v increments.
2 Batteries: <6.4v displays empty battery. 6.4v-8.4v in 0.2v increments.ResistanceDisplays resistance to 2 decimal places. Example: 1.23Ω
Range: 0.00Ω - 9.90Ω. If over this range it will display 9.90ΩVoltage Under LoadDisplays the voltage to 2 decimal place. Example 1.23V.WattageDisplays wattage to 2 decimal places. Example 1.23W.
Wattage is calculated from resistance and voltage under load.AmperageDisplays amperage to 2 decimal places. Example 1.23A.
Amperage is calculated from the resistance and voltage under load.Reverse Polarity ProtectionAuto protection if the batteries are put in the wrong way around.

 

[spec]

I don't quite understand the data on the meter, but no worries I will stick with PMOFETS.

spec

 

[spec]

Here is the revised circuit- see if you can find the errors.

The schematic looks weird because it indicates the physical implementation, including star points and thick wires.

spec

ERRATA
(1) Change PMOSFET to part number, IPP80P03P4L (TO220 case version for availability, ease of connection, ease of mounting, better heat dissipation).
(2) C16 should read C1

DATA SHEETS
Issue 4 of 2016_06_25
(1) PMOSFET
https://www.mouser.com/ds/2/196/Infineon-I80P03P4L_04-DS-v01_01-en-785584.pdf
(2) Capacitor
https://product.tdk.com/info/en/documents/catalog/leadmlcc_conventional_fk_en.pdf
(3) Resistor
https://www.seielect.com/Catalog/SEI-RNF_RNMF.pdf
(4) Case
https://cpc.farnell.com/takachi/cdm8524bk/alu-enclosure-black-112x70x35mm/dp/EN83763

NOTES
Issue 15 of 2016_06_25
(1) Four parallel PMOSFETs are used to share the current and hence power. This also has the benefit of reducing the effective resistance of the circuit.
(2) SW1 turns the current on
(3) R3 is your Kanthal thermal resistor load
(4) The circle with the V in it is your voltmeter
(5) The circle with the A in it is your ammeter. You can can connect the ammeter below R3 if required.
(7) It is essential with this type of high current circuit to use heavy conductors and substantial terminals to minimize the voltage drops. All wires should be kept as short as possible.
(7) It is essential that the wires connecting from the top star point to the PMOSFET sources are the same wire and the same length.
(8) It is important that the wires connecting the drains of the PMOSFETs to the mid star point are the same wire type and the same length.
(9) The 22R resistors connected to the gates of the PMOSFETs are gate stoppers to prevent the PMOSFETs from oscillating at between 2MHz and 10MHz (MOSFETs have a high frequency response, high parasitic capacitance, and large power gain). The 22 Ohm resistors should be connected directly to the gate terminal of the PMOSFETs.
(10) The capacitor is just to decouple the supply line and reduce the chance of the MOSFETs oscillating.
(10) Initial calculations indicate that the PMOSFETs will not require a heat sink provided that the PMOSFETs are mounted in freely circulating air. But as you have an aluminum box it would be wise to mount the PMOSFETs in thermal contact with the box, but electrically insulated.
(11) Heavy traces on the schematic indicate correspondingly heavy wire- the heavier the better within reason.
(12) Three star points are shown on the schematic, upper, mid, and lower. Star points are a physical low resistance point to ensure that the voltage drops resulting from conductor (wire) resistance and the current flowing do not adversely affect the functioning of the circuit. In the case of this circuit the conductor voltage drops can be an advantage by improving current sharing between the four PMOSFETs. This is also aided because copper wire has a positive temperature/resistance coefficient (resistance increases with temperature) as does the PMOSFET RDss (resistance between drain and source when the PMOSFET is turned on).
(13) When you build a circuit it is best to provide maximum accessibility. For this reason it is an advantage to build the circuit on the underside of the case lid with all external wires entering the lid through holes in the lid. This may seem odd to you, but it is the best way. As I have said many times before, there is a saying in engineering that any component, never mind how simple, will fail if it is inaccessible.
(14) The star after each component name have no significance.
(15) R after a resistor value indicates Ohms ie 470R = 470 Ohms. 4R7 would indicate 4.7 Ohms. 4K7 would indicate 4.7K Ohms = 47000 Ohms. Similarly 4M7= 4.7 Megga Ohms = 4700000 Ohms. Finally 0R22 would indicate 0.22 Ohms or 220 mili Ohms.

PARTS LIST AND SOURCES
Issue 8 of 2016_06_25
(1) 4 off: PMOSFET, Infinion, IPP80P03P4L (TO220 case version recommended)
**broken link removed**
(2) 1 off: Capacitor, TDK, 22uF ceramic, X7R dielectric, 25V, 10%
**broken link removed**
(3) 1 off: Resistor, Stackpole, 470R, metal film, 250mW, 1% , axial, through hole
**broken link removed**
(4) 4 off: Resistor Stackpole, 22R metal film, 250mW, 1%, axial, through hole
**broken link removed**
(5) 4 off, Avid, Mica Pad thermal electrical insulating
https://www.digikey.co.uk/product-detail/en/aavid-thermalloy/56-77-11G/56-77-11G-ND/1625385

 

[chemelec]

What is the 80mR?

Is it a Separate Resistor?
Or does it represent the Internal resistance of the Mosfets when turned on?

 

[ronsimpson]

What is the 80mR?

It is the load he want to put 2oo watts into.

 

[chemelec]

Considering the Amperage, You also need to consider Wire Resistances, "From and To the Load Resistor", as well as the "Resistance from the Load Resistor to the Battery".
For the 50+ Amps and a Low Resistance, it will need to be BIG Wire
And Common Point Connections from the Mosfets to the Battery and the Mosfets to the Load Resistor are Essential.
Or the current won't be Even between the 4 Mosfets.

Additionally if the Gate Voltage goes below -3.3 Volts, the Internal Resistance of the Mosfets will RISE considerably.
Might be a good idea to use a Separate Battery for the Turn on Voltage.

 

[ronsimpson]

You can get much better N-MOSFETs.
But you want it to be a P-MOSFET.
SO:
The BS250 is P. Very small but will drive the next FET.
Now you can choose a lower resistance N-FET.

 

[gentlywiringit*]

I have 12g or 14g silicone wire for the heavy load, itll be around 100mm long.


spec if there are no errors, you've told me the mosfet's, would you have the part numbers for the other components?