23 March, 2013

Airsoft Glock 18C NiMh to LiPo Conversion

This post is about my adventures in converting an AEP to LiPo power.

But first, some background...

Airsofters know that cold is not good for gas weapons. The extreme cold makes the gas less gassy and more liquidy and so the beebs fly with much less power, if at all. Of course there are 'winter' gasses and CO2, but they still seem to be very temperature sensitive and CO2 in warmer conditions can make for a dangerously 'hot' weapon and put your pistol under a lot of internal stress.

The last thing you want is to have the airsoft equivalent of brewers droop when you really want to rely on your side-arm. You take aim at the bayonet charge, fire! and the beeb rolls embarrassingly out of the barrel and lands on your boot.

With this problem in mind, cold weather airsofters might want to consider the benefits of an Airsoft Electric Pistol (AEP). The AEP is battery powered, so there are no cold gas issues. Pedants will point out that cold effects batteries too. This is actually true, but generally the negative effect of cold on a AEP is much less than the negative effect of cold on a gas pistol. However if it is *really* cold, and I mean frigid cold, then you can expect problems with any moving mechanical device regardless of the power source.

The choice of AEPs is fairly limited however. Compared to the vast range of gas pistols there are approximately 5% to 10% of the choice of those models as AEPs. Worst still, of that small range of AEP's the batteries they use tend to be the older Nickel Metal Hydride (NiMh) chemistry cells. Now I should declare a bias. I love Lithium Polymer (LiPo) batteries and I do not like NiMh batteries. LiPos are small, powerful, light and contrary to folk myth easy to maintain, charge and manage. The golden rule with LiPos is to use a good balance charger, and don't abuse them.

I couldn't find an AEP that I wanted that was also LiPo powered. I do however like Glocks and I do like Tokyo Marui. So I ordered a TM Glock 18C AEP which is... stuck in f**king Customs. On calling the courier Parcel Force (more like Parcel Farce) I was told to expect a FOUR WEEK delay. The douchebags!  So as an interim measure I bought a clone of the TM Glock 18C, the ASG/Cyma Glock 18C. I am told that it is a very close clone, and can share batteries.

I decided to convert it from running on NiMh cells to run on LiPo cells. I did not invent this process. I have seen other posts on this, but I have found them to be lacking in specific detail.

Here is a picture of the ASG Glock with the original NiMh cell in black with the tiny LiPo I shall replace it with in blue with the protruding wires.

Glock meets modern battery technology
The LiPo cell is absolutely tiny. Here is a closer picture compared to a stick of gum and a UK Pound coin for scale.

So cute, you want to give them pet names!
For those of you who like numbers here are the stats:

Fully charged: 7.29 volts, 500 mah
Discharge Capacity (C): 2 to 3C
Brand: Unbranded
Weight: 60 grammes 
Size: 91.1mm x 23.8mm x 12.0mm
Connector: Propriety
Cost: £9.95

Fully charged: 8.49 volts, 300 mah
Discharge Capacity (C): 35C to 70C(peak)
Brand: Turnigy, Nano-Tech
Weight: 16 grammes 
Size: 44.3mm x 16.9mm x 12.8mm
Connector: JST Balance Charge Connector (White), JST Power Connector (Red)
Cost: £6.95

The comparison looks like this. Although the LiPo carries 60% of the duration of the NiMh. It delivers more voltage, for only 25% of the weight and 50% of the size and it can deliver about TEN TIMES the current. DO NOT LICK A LIPO ACROSS THE TERMINALS. ;)

That means the pistol will have a much sharper (immediate) trigger response as you will see in the movie at the bottom of this post, as opposed to the sluggish NiMh trigger response.

So onward with the conversion...

Not wanting to pull the innards out of the pistol  I opted as others have done to convert the battery and leave the gun entirely as it came from the factory. This prevents invalidating warranty or messing with the out of the box perfectness that is Tokyo Marui. There is also an added bonus, that it can go back to NiMh power if you sell the gun to a NiMh Luddite. ;)

The main strategy for the conversion is to remove the proprietary connector and solder it to a female JST power connector which the new LiPo will directly plug into.

First the disassembly of the NiMh.

This photo shows from the top a NiMh in original condition. Below it a battery pack with the outer shrink wrap cut off, and below that the actual shrink wrap.
Cut off the outer heat shrink cover.
Sorry this next image is of very poor quality and I flipped the battery by 180 degrees...
Carefully pry off the propriety connector
I detached the proprietary connector taking care not to break the metal contacts which I will later solder onto.
The proprietary connector detached and unbroken
I then soldered the JST power connector, observing the correct polarity.
Soldering to the steel pins on the connector is NOT easy
Just a bit of soldering and this very simple project is finished...
A LiPo now connected to a proprietary connector.
I felt that the solder might be exposed to movement and therefore cracking, so I reinforced the solder joints with some two part epoxy resin.
The solder joints reinforced with two part epoxy

I deliberately kept the wires long. I like having enough wire to easily remove and connect the battery. It all fits snuggly...
Fits perfectly.
I would not be tempted to buy larger LiPo cells. These are large enough and don't need to be forced which would risk damaging the battery. I bought two LiPos with the intention to swap them at lunchtime should the pistol receive heavy use.

Wanna see the performance difference of two fully charged new batteries?

Impressive, huh? LiPos rule!

Tools and materials used (as requested by Bap1811)

  • Soldering Iron
  • Solder (containing flux)
  • Blade to cut the heat-shrink
  • Long nose pliers to carefully tease off the proprietary connector 
  • Turnigy Nano-Tech 300mah 7.4v 2S Lipo (from eBay)
  • JST Power connector, female (from ebay)

Update 4th April 2013:

I have now created a second project with a permanent connection.

You can read this second post by clicking here.