Saturday, October 20, 2018

LiPo batteries for Nerf Modulus ECS-10 blaster

I have an ECS-10 in my basement, but it's for an Xmas present.  So I don't want to unpack and measure it (yet).

Note: this information applies, in a limited way, to the Stryfe.  The Modulus ECS-10 has additional extra space under the battery tray; the Stryfe (apparently) does not.   Stryfe owners have the option to buy an extended (deeper) battery cover - Modulus owners do not.

Also note this assumes you remove the stock ECS battery tray completely.

See this video for a good look at ECS-10 disassembly and internals.  Also see this video for how to wire a plug.

If you don't understand the battery specs below, see this video.

Voltage: 7.4V (2S) for stock motors; 11.1V (3S) for some upgraded motors.  If in doubt, go 2S.

Current:  Higher C rate is better.  But unless you are truly hardcore, anything over 25C is likely fine.

I have to mention many people get C discharge rate wrong.  The discharge rate is the number times the capacity of the battery.  That is "20C" on a 1500 mAh cell is 20 * 1500 mAh = 30A.  20C is not 20A!

This means that batteries with bigger capacities will tend to have lower C rates, but can still deliver high currents.

Capacity:  Well, bigger is better, duh.  Price is proportional, of course.  No one knows how many shots/mAh you can expect.

Size:  The ECS-10 takes four AA batteries in a tray which is clearly a simple boxSuch a holder is typically 109 x 31 x 15mm minimum

Length is fixed by the blaster.  Say, 110mm limit.

Width: Batteries are max 14.5mm in diameter (call it 15) plus three 1mm walls, so call it 33mm
Maybe another 1-2mm by shaving the edges of the blaster, so 35 max?.

Depth is uncertain, 15mm for a battery, 1mm wall, plus another couple in the blaster.  Say, 18mm? 

Tons of room for plugs and wiring around that area, no need to add any space for those.

Add a little margin, we have 109mm x 33mm x 16mm(-ish).  I've seen someone fit a 34mm wide pack in without difficulty, but their blaster had shaved edges around the battery tray location.  35 miiiight just fit.

Plug:  As you install your own plug into the Modulus, it's dealers choice.  Make sure the balancing plug is compatible with your charger!

Some prefer XT60 or T-plug over JST, arguing the JST is not rated for the current.  However, the limit is really the temperature rating of the connector, which is 85*C and well beyond most hobby applications.

My experience with the WLToys L959 buggy indicates that JSTs do fine and do not get even barely warm, so I'm confident JST is OK.  If concerned, go with T-plug / Deans plug (50A) or XT60 (60A).

Wire:  All cells will come with appropriate wire.  The wires are very short and therefore very low resistance, and highly unlikely to heat up on anything other than a dead short.  Experience with JST-equipped 1500 mAh packs in L959 bear this out.

For the same reasons, I do not believe that upgraded wire in the Nerf is required regardless of what you do, but I've not tested it personally.

The following batteries have been reported to fit the Modulus ECS-10:

Turnigy 1000 mAh 2S 30C (73 x 34 x 15, 30A peak) [Ref, Link (Hobbyking)]
Turnigy nano-tech 1800 2S 25C (103 x 35 x 13, 45A peak) [Ref, Link (Hobbyking)]
Turnigy Graphene 950 mAh 2S 65C (72 x 26 x 15, 58A peak) [Ref, Ref 2, Link (Hobbyking), Link (Amazon)]
Turnigy 800 mAh 2S 20C (55 x 30 x 18, 16A peak)

Also several Zippy Compact cells, but I don't have model numbers.

Turnigy Graphene 1300 mAh 3S 45C (75 x 36 x 27, 58A peak) [Ref, Link (Hobbyking)]  <- May be too deep, YMMV.

This would make the peak size about 108 x 34 (or 35) x 18mm.   (I'm leaving out the 3S cell, above, as I don't believe a 27mm deep cell will fit a Modulus.)

For cheaper options, look at NFStrike or Banggood.  Note Banggood can have problems shipping due to upgraded regulations on shipping lithium batteries.

I wanted my packs to do double duty in my L959 and L969 RC vehicles.  Maximum dimensions for the RCs is 84 x 35 x 18mm.  I prefer T plug (a.k.a. Deans plug) because my chargers and L969 are T-plug. 

So my packs have to be 84 x 34 x 18mm, max.

HobbyKing has a selector that will let you search their lipo cells by size - go hereHere are my results using the dimensions above.

My first choices (not yet actually verified to fit my ECS-10s):

Zop 1500 mAh from Banggood.  (Perfect, but they can't currently ship to Canada.)
Turnigy nano-tech 1300 mAh 2S 20C from HobbyKing.

1400 mAh from NFStrike, which is half the cost of the Turnigy.
Other 1400 mAh from NFStrike.

1300 mAh seems to be the limit for brand-name packs.  The Zop and NFStrike cells ratings are probably exaggerated, but probably not enough so I'd notice.

I will likely buy the Turnigy nano-tech 1300 mAh 2S 20C from HobbyKing.  Mostly because it is 34mm and most likely to fit the ECS-10.  Other packs are 35mm and I just don't know if it will fit.


-  NFStrike usually has a 10% off coupon.

-  Hobbyking has $50 free ship to Canada, but only from USA warehouse (not Global Warehouse).  That can save you $20-$30 overall, and may make a more expensive battery cheaper than a less expensive battery.