Li-Po

[tommyb]

Im looking at changing all my batteries to Li-po, just curious as to whether I have to run a mosfet? Will the increased voltage errode the trigger contacts or anything?

Im not very good with electrics :D

Thanks,
Tom.

[magic_golem]

Re: Li-Po

Hi, well the voltage that a battery gives is proportional to the draw on it, ie you can get 100 volts out of a AA battery but only for a second then its dead :P.
but yeah it will wear out your contacts a bit faster than standard batteries although they wear out contacts too, much more so at high loads as the peak draw response on a lipo is far quicker than a standard battery, especially as its only powering a brushless motor ( ever noticed you rate of fire increase slightly the longer you hold the trigger down?).
A mosfet would sort the problem out as all the scorching damage to trigger contacts is done by arching (lightning) between the contacts when they are close to being open or closed (just before making 'true' contact when you pull the trigger and also just after you break the circuit when you take your finger off the trig).
Although a mosfet would probably break eventually too as nothing lasts forever but replacing one is as simple as changing a lightbulb, youd just need to cut the old one out and solder a new one in (dont have to take the mechbox out at all.
Your trigger response would be very fast though as i mentioned earlyr about the peak draw response being faster, the combination of a lipo and a mosfet means that your motor gets full load almost instantly, instead of the mechanical system taking a bit longer to get 'up to speed'.
perhaps you should brew some coffee and hit the net and do some research?
also dont forget that lipos need a different kind of charger too.

im thinking of modding up my mp7's to lipo/mosfets at some point too :P

anyways that was a bit of a rant but i hope i got the gist of the message over without sounding like a nerd :P

[tommyb]

Re: Li-Po

Yeh thats very helpful cheers! Im aware of the charging requirements of a Li-po, and how volatile they are lol.

Are mosfets relatively easy to install/setup? This is all to go into an ICS M4...

[Barny Hamon]

Re: Li-Po

Yeah they are, you can either get ones already soldered to the wires or you can solder the wires to it yourself.

[tommyb]

Re: Li-Po

Cool, where are they available from?

[tallbloke]

Re: Li-Po

especially as its only powering a brushless motor

what motor is that then - sorry I'm know PTW motors have brushes & I'm pretty much 100% that most airsoft motors also have brushes.

[magic_golem]

Re: Li-Po

oops sorry meant to say 'simple stepless motor' as in they are not stepper motors (the step the wrong way is done by the anitreversal latch :p).

But basically as they are simple, the more power you put in the fater they will turn (within limits though! as they are only small).

As for buying them you could just go to maplin they'll have them probably or an airsoft supply shop but you'll probably pay over the odd there as there seems to be some kind of special tax just for airsofters that makes things like switches,wires,etc cost more....

- the wiring is simple you can find guides online to follow.

[tommyb]

Re: Li-Po

Done some researching into this now. Basically found that a 7.2v 25c Lipo would be good for what I need it to do. They only draw as much current as the motor needs as well, so If my gun needed 20A of power to run, and the Lipo made 55A then it would only use 20A from the battery and 35A would go unused.

Compared to a 8.4v battery which makes for instance 16A the gun would run slow, thats why you get an increase in ROF when you use a lipo.

I think thats right anyway. Found a source for Mosfets ready made for $25 if thats good? Im not sure how much I should pay, this has 'active braking' or something?

[specialist]

Re: Li-Po

I beleieve that with a a Lipo battery you should be using an (audible) low voltage warning device because you can ruin a Lipo if it goes below a certain voltage.

Does anyone have a good Lipo and battery warning indicator setup on say, an M4?

[tommyb]

Re: Li-Po

You cant let them go below 3V...I have seen someone using a warning device at GZU in an MP5.

[Destroyer]

Re: Li-Po

im converting my aug to li poly. i have a voltage detector built into the side of the gun. cost 4 quid, has an LCD disply to tell me the voltage. and a buzzer if it drops close to "the point of no return."

[Keith]

Re: Li-Po

i have a few questions that are related to this thread so may be of use here.

i have a crane stock atm and the batterys knackered, so insted of replacing with a nmh im thinking of stepping in the lipo direction.
will putting a lipo down the stock tube be risky?

i know you dont need as higher voltage Li-Po battery, to get the equivelent NMh rate of fire.
if i wanted say, a 10.8V NMh ROF, then what voltage li-po am i looking for (around 7.2 or 8.4).

my mate runs an 11V lipo in his PTW. his internalls are hellical gears etc.. do i need reinforced bushings etc (i have replaced for metal ones already), or different motor (i have eg1000)

i know, and youve mentioned that the voltage cannot go below 3v or so.. roughly how many bbs worth can you fire untill the average battery drops to this (in other words, am i going to need more than one battery for a days skirmish - i fire about 300-400 rounds a day, and almost always on semi-auto [pulls more current than auto]).

this is what its going in, and as you can appreciate, i dont want to messs it up.


thanks.
keith

[Skippy]

Re: Li-Po

Keith,

I was also very cautious about moving into lipos but have found they are fine and easy to get along with.

I run both 11.1V and 7.2V, the 11.1V 1200ma is a three piece type and it fits easily within a crane stock (even the ACM ones with the smaller comartments).

If you use semi the 11.1 gives a nice crisp trigger response (especially when used with a AB FET).

I would recommend having two of these for a days gaming based on your estimated usage.

As for running them right down, I have noticed that as soon as the ROF starts dropping (or response if on semi) then its time to change it out.

I dont recommend this but I have run mine to 0% once before and it didnt blow up, it took 3 charges before it would take 100% again though.

One of the audiable voltage detectors sounds sensible though.

Hope that helps

TC

[ADsE6]

Re: Li-Po

Putting a lipo down a stock tube shouldnt be any more risky than any other battery. Modifying it to fit the stock tube would be risky unless u can find one to suit the size of ur stock tube.

I would say the equivalent rof to a 9.6vNIMH would be a 7.2v lipo, 10.8NIMH or higher would be an 11.1v lipo.

Lipos tend to run more consistantly during its discharge and provide more shots per mah than NIMH batteries.

If buying a lipo u want a lipo which can provide no lower than 20C preferably 25C

Another advantage is size of the batteries, as u can pick up a 2100mah lipo which is smaller in dims to a 9.6v 1400mah by alot.

Equipment needed will be:

Lipo charger - capable of 2/3 cells for 7.2 or 11.1v lipos
Balancer - keeps charging safe and balanced
Low voltage indicator/buzzer, especially if ur just using singles as u wont notice the rof drop. (ROF Drop is easily noticable when ur batteries reaching its point of no return)

My recommendations:

Use 7.2v lipos on ur current setup, if u do want more rof, i would change ur motor. But with a 7.2v meeting a 9.6v rof, and personally i find the trigger response to be alot better in comparison to a 9.6v also.

Two batts would be sensible, always good to have a backup, although i would say one would get u through the day.

with Higher voltages, i.e. 11.1v i would recommend a mosfet, or a spare set of trigger contacts. other internals should be fine, but like running any higher voltage batteries wear will be increased due to increasing the number of cycles of the gearbox.

Nice gun btw

[tallbloke]

Re: Li-Po

i have a crane stock atm and the batterys knackered, so insted of replacing with a nmh im thinking of stepping in the lipo direction.
will putting a lipo down the stock tube be risky?

Nope I run 3 of my PTWs like that - just be careful no to damage the cells & wiring when inserting & removing the battery

i know you dont need as higher voltage Li-Po battery, to get the equivelent NMh rate of fire.
if i wanted say, a 10.8V NMh ROF, then what voltage li-po am i looking for (around 7.2 or 8.4).

Lipos are 3.7v per cell so: 7.4v, or 11.1v are your airsoft sizes really. a 7.2v should do you fine IMO.

my mate runs an 11V lipo in his PTW. his internalls are hellical gears etc.. do i need reinforced bushings etc (i have replaced for metal ones already), or different motor (i have eg1000)

Standard PTW Gears are superior in many ways to a normal AEG gearbox. Also the Max PTW are designed to happily take a M150 spring all day long on a 12v battery. I would upgrade your bushings, make sure you have some very good strong gears etc espically if your going to use a 11.1v battery pack.

i know, and youve mentioned that the voltage cannot go below 3v or so.. roughly how many bbs worth can you fire untill the average battery drops to this (in other words, am i going to need more than one battery for a days skirmish - i fire about 300-400 rounds a day, and almost always on semi-auto [pulls more current than auto]).

Get 2 batteries - the ones I use in my PTW are 11.1v 1200mah jobbies running the PTW at 425fps (single shot before you moan) I can run through about 420rnds happily before I need to change the battery - although I do religiously change the battery at the "lunchtime break" sometime after 420rnds sometimes before just to be safe.