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View Full Version : How much voltage for stacked fets?


miniz
2012.04.03, 07:41 PM
Hi guys,
I have a mr03 board in and AWD car and would really like to use a pair of lipo or life batts but what is the limit of voltage I can put through my board? I know they won't fit and i'll need to mod but what is 8.5-9v safe?

I have 2 x 3 stacks of 4562 fets

http://mini-zracer.com/forums/picture.php?albumid=145&pictureid=1341

http://mini-zracer.com/forums/picture.php?albumid=145&pictureid=1340

Cheers

Traveler
2012.04.03, 08:40 PM
I would keep it at no more than 7.4v

miniz
2012.04.04, 08:29 PM
Does that mean I can't put a pair of lipos in if they are freshly charged?
they would be around 8.4v full. I was hoping to drop in a pair of single cell lipos in series with a couple dummy cells.

Couldn't find much lipo related stuff unless it was to do with the brushless conversions which is a bit farther than i'm willing to go.

Traveler
2012.04.05, 05:43 AM
Not sure about Lipos. If you mean Lithium Ions which are usually 3.7v, so two in parallel would be 7.4v, which has been used safely on Mini-Z for years. You might be OK with a little more voltage, but I can't say for sure as even 7.4v is way above what the boards were designed to handle.

Have you checked out the tutorial on Atomicmods site on AWD AAA Lithium mod? HERE (http://www.atomicmods.com/Categories/Tutorial-1-28-Mini-Z-AWD-AAA-Lithium-Mod.aspx) is a link ;)

nicov
2012.04.05, 08:39 AM
don't worry about the FET , they can handle more than 10V.
You will need to check the other components on your electronic board by checking their datasheet - specially the voltage regulator, if any. if there isn't , next to check is the micro for Rx !

miniz
2012.04.05, 10:14 PM
Thanks guys.

Traveller, yeah I mean lithium polymer, same animal. I appreciate the links, great to know two fully charged lipo batts ain't gonna cook anything.

That atomic mod is brutal to look at, that's a one way approach I will be staying the hell away from as I want to run AA also.

Nicov - Do you mean some miniz boards can take 2s lipo and some can't or are Atomic and everyone else doing it wrong? Why must I check components if this is standard advised mod? Sorry if I am missing something obvious, please spell it out for me.

Just one thing that I couldn't finds on that atomic link. What do they or any lipo mini z user do for a cuttoff? Or is this a case of using a timer and doing a test first like planes?
Thanks again, I appreciate the experience here.

nicov
2012.04.06, 04:21 AM
Well, if people do use Li-ion, it seams no issue with this higher voltage.
Lipo is more sensitive about Cutoff, you could indeed time your runs to avoid undervoltages. LiFe is more safe IMHO.

miniz
2012.04.06, 02:20 PM
I would agree, hover finding AAA size life batts is an issue.

mleemor60
2012.04.06, 02:53 PM
Well, if people do use Li-ion, it seams no issue with this higher voltage.
Lipo is more sensitive about Cutoff, you could indeed time your runs to avoid undervoltages. LiFe is more safe IMHO.

And Kyosho makes a kit for it as well. Marketed through the 246 accessory line.

miniz
2012.04.06, 04:26 PM
I have seen the batts for the mr03 mod. I'm working with an awd so presumed it would not fit. They certainly don't look AAA, more oblong

These are all I have seen but the mah looks devastatingly low
http://www.*******o.uk/itm/4x-LiFePO4-AAA-rechargeable-battery-3-2V-w-dummy-cells-/251018932895?pt=US_Batteries&hash=item3a71e4f29f

oXYnary
2012.04.06, 07:13 PM
Those might work for the buggy as well..... Is the C rating high enough though?

I'm still worried about voltage regulation though as I keep hearing the asf digital servo boards have none.

Edit: This info is better in Mini-z science as I replied to another thread with some of the same questions you have.

BTW 10440 batteries are basically AAA size. I see some 500 ones in that from the same seller. You can get rare earth magnets to make the buttons longer if they wont fit the awd contacts.

miniz
2012.04.06, 08:43 PM
Exactly what I was thinking, ecig style battery contacts. I did wonder where best to put this, anyone is welcome to move this, I certainly missed the science sections so far

A timer will do but a cutt off alarm would be better. Thanks for the links and input guys, I have enough to get moving with stuff now, I was hoping someone could confirm or deny if those low mah life 10440 were pants or not.

Thanks for pointing out he had some larger ones but
I hear of longer run times with lipo setups but don't understand where that comes from if the lipos have less mah rating than the high capacity AAA.

I have some high drain lipos coming to test that are only 360 mah so will see how that goes before having to buy yet another charger for 3.2v life batts.

oXYnary
2012.04.06, 09:33 PM
Exactly what I was thinking, ecig style battery contacts. I did wonder where best to put this, anyone is welcome to move this, I certainly missed the science sections so far

A timer will do but a cutt off alarm would be better. Thanks for the links and input guys, I have enough to get moving with stuff now, I was hoping someone could confirm or deny if those low mah life 10440 were pants or not.

Thanks for pointing out he had some larger ones but
I hear of longer run times with lipo setups but don't understand where that comes from if the lipos have less mah rating than the high capacity AAA.

I have some high drain lipos coming to test that are only 360 mah so will see how that goes before having to buy yet another charger for 3.2v life batts.


Your current charger doesn't have a lion mode? Should be the same cutoff.

The Lipo runtime might be partially because the car is much lighter and a motor needs less amperage at higher voltage or something to that effect.

FWIW Someone thought the C rating discharge on those 500 cells was only .3. I thought I found a spec sheet that had 3c (1.5Amps) listed. Who knows. Too bad A123 doesn't make AAA cells...

targetingxmod
2012.04.07, 06:33 AM
The 7.4v on li-po is a little agressive for the miniz boards! it will work 50/50 safe on AM boards. It was tested several times and works, but in the long run, servo goes dead. It can take 2 years to make in dead...

And the li-fe ones are 6,6v that are specially made for miniz's ASF! and can be done for am boards to, It's a safe voltage since if you use alkaline baterys 4x1,5=6 volts.

Look at my projects with li-fe baterys :)

http://i206.photobucket.com/albums/bb18/fronterasportforum/Carson%20X3200%20-%20Xmod%20Evo%20Truck/155_18102010665.jpg
-Z-mod truck ASF 2.4ghz with 12 "4562" fets
http://i206.photobucket.com/albums/bb18/fronterasportforum/Carson%20X3200%20-%20Xmod%20Evo%20Truck/197_040120111077.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Carson%20X3200%20-%20Xmod%20Evo%20Truck/220_220920111972.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Carson%20X3200%20-%20Xmod%20Evo%20Truck/221_220920111973.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Carson%20X3200%20-%20Xmod%20Evo%20Truck/222_220920111974.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Carson%20X3200%20-%20Xmod%20Evo%20Truck/209_060120111092.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Carson%20X3200%20-%20Xmod%20Evo%20Truck/210_060120111093.jpg

Videos with ASF boards:
http://www.youtube.com/watch?v=IYSKjDonU-g
http://www.youtube.com/watch?v=2dB1LwhNsx8
http://www.youtube.com/watch?v=a2IQgymtjrg

Videos without ASF board:
http://www.youtube.com/watch?v=xOueA0gobcQ
http://www.youtube.com/watch?v=BGt8hjmrzh0
http://www.youtube.com/watch?v=thXyXrSCwrI

targetingxmod
2012.04.07, 06:40 AM
On my gen1 Z-mod ASF 2.4ghz board!

http://i206.photobucket.com/albums/bb18/fronterasportforum/Gen1%20X-mod%20Nissan%20GTR/63_17122010894.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Gen1%20X-mod%20Nissan%20GTR/64_17122010895.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Gen1%20X-mod%20Nissan%20GTR/59_17122010889.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Gen1%20X-mod%20Nissan%20GTR/60_17122010890.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Gen1%20X-mod%20Nissan%20GTR/129_250320111406.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Gen1%20X-mod%20Nissan%20GTR/137_161120112144.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Gen1%20X-mod%20Nissan%20GTR/135_161120112142.jpg

targetingxmod
2012.04.07, 06:47 AM
On my Evo car Z-Mod ASF 2.4ghz board

http://i206.photobucket.com/albums/bb18/fronterasportforum/Grey%20X-Mod%20Evo%20Nissan%20Skyline%20GTR/99_270120111206.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Grey%20X-Mod%20Evo%20Nissan%20Skyline%20GTR/105_090220111289.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Grey%20X-Mod%20Evo%20Nissan%20Skyline%20GTR/109_160320111336.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Grey%20X-Mod%20Evo%20Nissan%20Skyline%20GTR/125_280720111797.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Grey%20X-Mod%20Evo%20Nissan%20Skyline%20GTR/127_290720111800.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Grey%20X-Mod%20Evo%20Nissan%20Skyline%20GTR/133_160920111941.jpg
http://i206.photobucket.com/albums/bb18/fronterasportforum/Grey%20X-Mod%20Evo%20Nissan%20Skyline%20GTR/128_290720111799.jpg

Video on my home track:
http://www.youtube.com/watch?v=WrOtmsz64lM&feature=related

oXYnary
2012.04.07, 06:39 PM
And the li-fe ones are 6,6v that are specially made for miniz's ASF! and can be done for am boards to

So 6.6 is safe? Even with stock fets (non mod motor)? Ok, the issues is finding 2 Life AAA batteries (+2 Dummy cells). We want to be able to switch back and fourth and on the buggy at least the batteries are offset. So far I cant find high discharge rate ones.

It's a safe voltage since if you use alkaline baterys 4x1,5=6 volts.


Yes, but that nominal voltage on the life. They peak higher ~7.2volts!!!!!

cowboysir
2012.04.07, 07:02 PM
a couple things:

alkaline cells are not really 1.5volt...without load they register 1.5volt but when under load they are a 1.2volt cell just like any aaa. The discharge for alkaline sucks so considering them in the same comparison as other cells is a bit unrealistic.

li-Fe cells kind of have the same disposition...while unloaded they can peak at 7.2 volts (as a pack of 2) when they are under load they run at 6.6 volt.

I'm not really a big fan of modding mini-z's in this fashion but to each his own...I'd wager that you'd have better lap times with 4.8 volts and an appropriate setup than you would with higher voltages on a track.

targetingxmod
2012.04.08, 07:19 AM
Check this video:
http://www.youtube.com/watch?v=g0mRYOK_qYg

The li-fe baterys can be installed on the mini'z without altering nothing. You can back swithc to AAA just by removing 2 screws! They are made for the same size to be aprropiate for miniz.

As for altering miniz's it's like everything on li-fe! someone like stock, others like aftermakert "mamal" projects, or just like country girls vrs hardcore beachs! (lol) :)

Xmods are better for li-fe power, because of the less rolling chassis and heavier pounds they got!
Miniz's are very agile and do not need to much power to make the same thing. But a good Z-mod with ceramic bearings/CF shaft/li-fe power and Atomic Stock motor is very very very very good compared to a miniz! And with the right GPM stuff, otherwise it will be very sloppy!:) (the less not good part is the pot, but with miniz pcb the pot is awesome, it does not suffer any of the problems they got with toy grade pcb xmod have)

But after all miniz are race machine from the ground! Z-Mods you have to build to your own, or it will be the "toy" family 1/28 bug! lol
a couple things:

alkaline cells are not really 1.5volt...without load they register 1.5volt but when under load they are a 1.2volt cell just like any aaa. The discharge for alkaline sucks so considering them in the same comparison as other cells is a bit unrealistic.

li-Fe cells kind of have the same disposition...while unloaded they can peak at 7.2 volts (as a pack of 2) when they are under load they run at 6.6 volt.

I'm not really a big fan of modding mini-z's in this fashion but to each his own...I'd wager that you'd have better lap times with 4.8 volts and an appropriate setup than you would with higher voltages on a track.

targetingxmod
2012.04.08, 07:30 AM
The only thing fets do, is to permit more amps to be drawn from the baterys! Not voltage!
Stock can handle 6.6v or 7.4v.

Less resistence fets (better fets) will permit hot motors, because they offer less resistence to the amps pass, and will permit more power to pass!

Voltage is another thing! Comprende?

I never heard of li-fe baterys in AAA size or AA size! Just longer ones that are 1658 size or something (imcompatible size).
Meanwhile there are some AAA li-ion or AA li-on 7.2v, not li-fe 6.6v.

This miniz's li-fe ones (r246) or (eagle racing) are avaiable at a good hobby store! They are standart! No big deals on that!

So 6.6 is safe? Even with stock fets (non mod motor)? Ok, the issues is finding 2 Life AAA batteries (+2 Dummy cells). We want to be able to switch back and fourth and on the buggy at least the batteries are offset. So far I cant find high discharge rate ones.



Yes, but that nominal voltage on the life. They peak higher ~7.2volts!!!!!

cowboysir
2012.04.08, 02:19 PM
Check this video:
http://www.youtube.com/watch?v=g0mRYOK_qYg

The li-fe baterys can be installed on the mini'z without altering nothing. You can back swithc to AAA just by removing 2 screws! They are made for the same size to be aprropiate for miniz.

As for altering miniz's it's like everything on li-fe! someone like stock, others like aftermakert "mamal" projects, or just like country girls vrs hardcore beachs! (lol) :)

Xmods are better for li-fe power, because of the less rolling chassis and heavier pounds they got!
Miniz's are very agile and do not need to much power to make the same thing. But a good Z-mod with ceramic bearings/CF shaft/li-fe power and Atomic Stock motor is very very very very good compared to a miniz! And with the right GPM stuff, otherwise it will be very sloppy!:) (the less not good part is the pot, but with miniz pcb the pot is awesome, it does not suffer any of the problems they got with toy grade pcb xmod have)

But after all miniz are race machine from the ground! Z-Mods you have to build to your own, or it will be the "toy" family 1/28 bug! lol

Since we are after all in a mini-z forum section I felt it was necessary to chime in on the merits of adding voltage to an MR03.

X mods are by nature a moddable platform and with more weight comes more voltage and the increased ability to crash your alloy brick into stuff (not knocking it at all...been there and done it all as well).

my two favorite scratch xmod/li-po builds...one with a fet upgrade for more amp draw (nelly turbo) and one mamba powered 1/24th GTO.

http://i13.photobucket.com/albums/a258/CowboySiR/enzoroller001.jpg
http://i13.photobucket.com/albums/a258/CowboySiR/enzoproject001.jpg
http://i13.photobucket.com/albums/a258/CowboySiR/mambagoat3001.jpg
http://i13.photobucket.com/albums/a258/CowboySiR/mambagoat2005.jpg

Since we are discussing MR03's though i think the reality that oXYnary needs to know is:

4.8 volts+good setup+right tires=the best handling 1/28th racer around.;)

miniz
2012.04.08, 06:23 PM
Oxynary - you are correct, my lipo chager does not do life and the only life charger I have is a trust 3v one which is useless for the 3.3v batts.

everyone else, wow, those are some serious looking mods. So if it's bad in the long term to put a pair of 3.7v standard lipos in the mr03 board my only other questions are do these special mini z life batts need another special charger and will the fit into my awd chassis/mr03 combo?

Thanks again for the links, very inspiring pics and that underground track is simply gorgeous.

oXYnary
2012.04.08, 11:11 PM
I never heard of li-fe baterys in AAA size or AA size! Just longer ones that are 1658 size or something (imcompatible size).
Meanwhile there are some AAA li-ion or AA li-on 7.2v, not li-fe 6.6v.

This miniz's li-fe ones (r246) or (eagle racing) are avaiable at a good hobby store! They are standart! No big deals on that!

I think this was missed, but the r246 does not fit in the buggy. The buggy has offset battery slots.

I did find some LiFePO4 10440 (sames size as AAA minus button). However, I don't know the C rating. Usually very low.

miniz
2012.04.09, 09:23 AM
I have the awd non dws so I guess that's the same as the buggy.

nicov
2012.04.10, 11:37 AM
I did find some LiFePO4 10440 (sames size as AAA minus button). However, I don't know the C rating. Usually very low.

A quick WWW search returns a Capacity of 200mAh for these LiFePO4 10440 (AAA size).
The good thing is that you get 3.3V per cell, so you can mount them 2x2 in parallel , you end up with 400mAh total. Half of our NiMH today..
[edit] it seems there is also 500mAh of these cells ! But the quality of these cells is reported as quite poor - not the quality of A123 for instance.

oXYnary
2012.04.10, 05:43 PM
also 500mAh of these cells ! But the quality of these cells is reported as quite poor - not the quality of A123 for instance.

Yea, per seems like for now, motors are the only upgrades we can do.