Need Advice on - Battery storage - Mosfets.

[RCW05]

Hi guys!
ok, im wanting to change my ICS M4A1 from fixed stock to a folding stock,
i have a large 8.4V Battery that goes into my fixed stock. My question is, as nooby as it is, is there any other place to store a large battery, as i dont fancy buying more batteries just yet. cheers!

Ok, next question and its another nooby one. I know a small amount of mosfets, but are they a must have like some players have told me? and how easier are they to fit etc.

Thanks alot!

Rich

[Bachelarius]

Re: Need Advice on - Battery storage - Mosfets.

With m4s there are 3 main places where you can store a battery:

1) stock - as yours is a solid stock, you have the luxury of using pretty much any size battery, up to about 3300mAh 9.6 I think? if you take the battery door off, you can use a 4300mAh, if you secure it in place with tape or your sling or similar. Other stocks usually take Crane Stock batteries (split in 3 segments), nun-chuck cells and the tiny buffer tube lipos.

2) handguard - this takes a mini nimh battery, up to 9.6v of some tiny mAh rating, I think in the range of 1000-1500, but don't quote me. Again, many lipos can fit and some nun-chuck cells can also fit nicely in this space. This does require your rifle's gearbox to be front-wired though.

3) External - the most convenient place to put it, allowing for the largest batteries, but also the most annoying, as it messes with your rifle's aesthetics. Can be mounted in a PEQ box (front wired), cheek-rest/stock pouch (rear wired) or in a battery-sling pouch (can be either front or rear wired, depending on where your sling attachment point is)

So if you want to change stocks, but have to keep the existing battery, your simplest option is external, tied to the new stock. You can cover it up with a pouch and style it by concealing it inside a dummy magazine, poking out of the pouch, if you want to completely hide it in a novel way. Else, rewire your gearbox to the front and pop it in a PEQ box attached to the RIS, if you have one. But that will cost as much as just buying a new cell, so I'd just do that tbh... And PEQ boxes do look a bit queer, but that's just my opinion.

With the mosfet... the reason why they are so good is because they are in essence a 'free' upgrade, with absolutely no drawbacks. What they do is instead of using the trigger switch as a physical switch, which literally takes all the power from the battery and feeds it into the motor, it uses it as a signal and passes the actual power through itself, the mosfet. This massively reduces the resistance which before was caused by the trigger circuit, thus slightly increasing the RoF and trigger response and also slightly lowers the average battery drain per shot. But the big bonus comes when you use higher voltage batteries. The higher the voltage of a cell, the higher the chance of sparks forming between the trigger contacts and thus corrodes them. Because the mosfet itself is solid state, it does not spark, thus does not wear out! So it protects your gearbox from higher voltages.

As far as fitting one goes, what it does involve is taking apart the gearbox and some soldering. A mosfet is like a spider which sits between the trigger, battery and motor, linking the 3 together. It can have anywhere between 3 and 6 wires and usually tells you what you need to do with them in the instructions. Generally it looks something like this (ignore the individual parts there, focus on the wires themselves, it's a diagram of a DIY fet design):



As you are sticking to 8.4v, it's not something you "NEED!!!!", it's just a nice to have, which deals with the inadequacies of the stock trigger contacts. Other common mods include replacing those god-awful tamiya/mini tamiya battery/rifle connectors everywhere you see them with something decent, like Deans or JST or Traxxas or whatever, more here. The tamiyas, like the stock trigger contacts wear out, only they happen to be even more flimsy and have a resistance which is pretty high as well.

Hope that all helps, Nikolay.

[RCW05]

Re: Need Advice on - Battery storage - Mosfets.

Wow thanks alot, that has to be the best reply i've had haha. Ok another noob question, but if i decided to get a smaller battery and fit it into the foregrip, would it last less time than my large battery? as i understand the mah matters or something. And if this is a case what if i got a small lipo to fit into the foregrip?

Very informative about the mosfet, thanks dude. Its something i'll definitely look into in the future, now knowing they arent imminently needed!

Thanks again

[Bachelarius]

Re: Need Advice on - Battery storage - Mosfets.

yeah, the mAh rating is pretty much the juice it has, i.e. the total capacity. Realistically speaking, it's worth having 2 minis with you to last the day. But again, consider changing connectors to something decent, as the more you plug/unplug them, the faster they wear out.