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Power MOSFETs. Which can I substitute?

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bigal_scorpio

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Hi to all,

I am currently trying to repair a Li-Ion battery pack that has a damaged part.

The part is a FDS4435 Power Trench MOSFET. Is there a difference between this and say an IRFR5505 which is a HEXFET power MOSFET, well a difference that would matter?

I don't pretend to be an expert on FETs and frankly get bogged down in the technical specs which seem so complicated with them, so if anyone could confirm if this is ok I would be grateful.

Thanks.......Al
 
For DC MOSFET transistor applications, the important parameters to compare are the maximum voltage, maximum current, power, on-resistance, and gate-threshold voltage ratings.
 
Hi Carl and Ron,

Thanks for the advice. But the datasheets are really strange, they seem to have RDS(on) as 0.11r on one and on the other it is between 15Mr and 20Mr. Are there 2 different mandates for RDS?

Al
 
Thanks for the advice. But the datasheets are really strange, they seem to have RDS(on) as 0.11r on one and on the other it is between 15Mr and 20Mr. Are there 2 different mandates for RDS?
15M(m)r and 20M(m)r are 15 milliohms and 20 milliohms (.015 and .020 ohms). 0.11r ohms equals 110 milliohms.

For your info M stands for mega (one million) and m stands for milli (1/1000), so don't confuse M with m.
 
cheers Carl, just goes to show that I learn something every day - and forget 2! hehehe

Al
 
cheers Carl, just goes to show that I learn something every day - and forget 2! hehehe

Al

Hi Al,
There is a difference in the Gate threshold voltages between the original PMOS and the one you want to use as a replacement.

The original MOS has a Vgs threshold of only -1v to -2v, whereas the substitute has a Vgs threshold of -2v to -4v.

As the MOSFET is part of a Lithium Ion battery pack this doubling in Vgs could make a big difference in the performance/safety of the battery pack.

I would advise that you use only a FDS4435 as a replacement.

You may find this link useful.
https://www.electronics-lab.com/articles/Li_Ion_reconstruct/index.html
E.
OT: Hope you are feeling better.
 
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Hi bigal_scorpio,

if you use https://www.datasheetarchive.com you just type into the search line >Power P-channel MosFet<.

The search result will show some samples of P-channel power MosFet transistors along with a comparison table you might download.

There you'll certainly find a substitute for any transistor with P-channel characteristics.

Regards

Boncuk
 
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Hi to all,

Thanks Eric and Boncuk, I finally sourced the original part from Farnell, then spent another 3 hours looking through their awful website just to get to the minimum order limit.

It really is dismal to try and find things on there, I wish they would do a more friendy version.

No news on the date of op yet Eric but they did say it would most likely be after christmas, just wish I could get some glasses with a prismatic lens or something, mine are b**ger all use now as with my head down I'm just looking over the top of them.

Anyway as the mother wrote back to her soldier son (well my dad always quoted it!), pig dead son, soldier on. hehehe

Al
 
Hi Guys,

I know I moan about Farnell's web site but I have to hand it to them with speed!

Ordered at 6.30pm yesterday and parcel arrived at 9.30am today, now fitted and working well before lunchtime! cool eh

Al
 
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