Make Your Own High Capacity E-mag Battery for Less Than $45

[ArmyEngineer]

Hey guys,
I posted this over in my spot welder thread. I though this might be worth another separate post.

I needed a new battery pack for my E-mag, so I bought 16 Sanyo 1000mah cells for $28 from emallgroup.com (The pack only needs 14.) Well I was going to spot weld the pack myself, but the supplies are still in transit and I am impatient. So I called up my local BatteriesPlus store and asked what it would cost to have them assemble the battery pack. $16.

This pack uses the highest quality NiMH cells available. These are pretty much high capacity Sanyo Eneloop cells. If you need a battery pack custom built, call up your local BatteriesPlus and have them spot weld the pack for you!

http://www.batteriesplus.com/

Smeek found this link for high capacity Tenergy cells with pre attached tabs. It would be very easy to use these and cut out the batteriesplus spotweld fee. Clip the tabs back and solder them up - you've got a battery pack for under $20. I wish I had seent those a couple days ago. :)

http://www.all-battery.com/aaa1000mahtenergyhighcapacitynimhrechargeablebatteryflattop.aspx

[smeek]

Awesome idea, and I have a Batteries Plus less than a mile from my house. Thanks for sharing.

Of course I don't need a battery just yet, but this makes me wonder if someone could come up with a 5-6 cell Lithium Ion pack and a way to charge it. Wonder what the weight difference would be and if it's worth it.

[ArmyEngineer]

Awesome idea, and I have a Batteries Plus less than a mile from my house. Thanks for sharing.

Of course I don't need a battery just yet, but this makes me wonder if someone could come up with a 5-6 cell Lithium Ion pack and a way to charge it. Wonder what the weight difference would be and if it's worth it.

Hey smeek.
I considered the use of li-ion or li-po cells in my pack. It seems that the cells generally do have higher energy density, but I get the feeling that there is a lot of hype going around. The cells I found in AAA size would allow you to create an equivalent or slightly higher voltage pack with 4-5 cells as opposed to 14. That is a significant saving in weight. However, just from my skimming battery sites, I found that most of those cells had much lower capacities - between 300 and 500 mah. Considering the cells I purchased had a capacity of 1000mah, you would need 10 li ion cells to produce a slightly higher capacity pack.

The end result is that you spend about the same $$ on the packs, but your weight savings is only about 64 g. Thats a little more than 2 ounces. Now, if you went for a 4-5 cell pack, you could save close to 170 g which is about 6oz. But in that case, you would have about half of the play time. I'm not sure that would be worth having to go through the trouble and expense of finding a new charger capable of safely charging the li ion pack. If the li ion cells rupture, it could potentially be much worse than the NiMH. Then you also have to worry about the li-ion cells discharging below their minimum recoverable voltage. The NiMH cells are simply more durable.

Pros Li-ion
~4 Fewer batteries required
Longer play time since nominal voltage would be higher
Better for cold weather

Pros NiMH
More flexible/durable when it comes to charging
No need to keep the cells above a threshold voltage
easy to find an inexpensive charger of use the one you have
longer shelf life
No need to worry about supplying an overvoltage to the e-mag board

In the end, the high capacity NiMH cells won me over.

[vf-xx]

It's not my thing, but I have a buddy who's into RC planes. He uses a lot of Li-po flat cells in his stuff. They're all in the 1000 mAh ratings or higher.

The other thing you could look into are CR123A cells. They have some high capacitance too.

[smeek]

Thanks for the info AE.

I tend to agree it sounds like more hassle than it's worth in the end. Today was the first day I shot an emag since I test fired one at an AGD booth at World Cup way back when. Other than needing some oil and a bit of fine tuning I don't think there's anything I'm going to change on it outside of the stock trigger. I never thought the gun felt heavy at any point, it's already got a karta body and rail with an X valve not the old SS parts so it's light enough as it is.

Edit: Thanks to the craftiness of the folks at google this thread's well placed and on topic google ad pointed me to these. http://www.all-battery.com/aaa1000ma...ryflattop.aspx

[ArmyEngineer]

Thanks for the info AE.

I tend to agree it sounds like more hassle than it's worth in the end. Today was the first day I shot an emag since I test fired one at an AGD booth at World Cup way back when. Other than needing some oil and a bit of fine tuning I don't think there's anything I'm going to change on it outside of the stock trigger. I never thought the gun felt heavy at any point, it's already got a karta body and rail with an X valve not the old SS parts so it's light enough as it is.

Edit: Thanks to the craftiness of the folks at google this thread's well placed and on topic google ad pointed me to these. http://www.all-battery.com/aaa1000ma...ryflattop.aspx

That is an EXCELLENT price. Purchasing the cells with tabs makes it 100% do it yourself. Those tabs are solderable, and you may not even need any extra wire. With about 20 minutes and $20, you would have a very nice high capacity E-mag battery. I'm going to stick that link in the first post.

One note, based on the reviews on Amazon for Tenergy cells, you might want to buy a few extra just in case there is a dud or two. Be sure to charge and check the voltage on the cells before you assemble the pack!

[DoubleDutch]

Just came across this thread, I was looking because I recently picked up my first E-Mag :)

I have not played yet with it, and with all the talk about the capacities, I was wondering how many people have actually run out of power in "real world" use. According to the E-Mag manual, the original 650 mAh battery should be good for 20,000 shots. Can someone confirm that? That is a lot of paint to shoot during a regular day! Would a half-capacity battery be enough, and be lighter?

Secondly, when making a battery pack yourself, using say Li-Ion cylindrical batteries at 3.7 volts, how do you get exactly to 16.8 volts, to match the original battery? Do you go 4 or 5 cells? Looking at the Li-Ion batteries in the referenced website, it seems like you could have a 2000 mAh battery pack if you wanted to!

[ArmyEngineer]

Just came across this thread, I was looking because I recently picked up my first E-Mag :)

I have not played yet with it, and with all the talk about the capacities, I was wondering how many people have actually run out of power in "real world" use. According to the E-Mag manual, the original 650 mAh battery should be good for 20,000 shots. Can someone confirm that? That is a lot of paint to shoot during a regular day! Would a half-capacity battery be enough, and be lighter?

Secondly, when making a battery pack yourself, using say Li-Ion cylindrical batteries at 3.7 volts, how do you get exactly to 16.8 volts, to match the original battery? Do you go 4 or 5 cells? Looking at the Li-Ion batteries in the referenced website, it seems like you could have a 2000 mAh battery pack if you wanted to!

Hey man! I can't really speak to the real world play time. (I haven't had a chance to play with mine yet. I'm going to try to go tonight.) The voltage on the battery is not as crucial as you might think. Fresh off the charger, even the stock battery will hit around 19 volts. I would try not to go much higher than that though. Most Li-ion cells charge up to around 4.2 volts nominally. So you would probably be wise to stick with four of them. But really it depends on what you buy. You could build a very high capacity battery with the li-ions, but the AAA size cells offer similar capacities. I personally don't think it is worth the trouble, risk, or expense.

[athomas]

You only need to be close to the voltage. Its not a precise device. Delivering the required current is more crucial than the voltage.

I bought a box of 20 - 1000mA batteries for mine a couple of years ago. They were about $.50 each on sale. I soldered them up myself. They work great. I had to be very precise in my soldering because they were standard cells and any extra length would have created a tight fit. The ones with the tabs are a bit shorter so you should be ok.

When I used to use my emag in tournaments as my main gun, I never had to worry about the battery dieing, even with the old 650mA pack. I used to shoot 5000 or 6000 rounds in an outing, plus dry firing. I'd say the 20000 round estimate is probably accurate for a new battery pack. I suspect the 1000mA packs would get close to 30000 rounds per charge. Even a weaker 1000mA pack would probably get you close to 20000 shots.

[DoubleDutch]

Hey this whole DIY battery building business, is it under the assumption that you are starting from a dead battery, whose top you are reusing? Or is the top a generic part you can buy online too? I just picked up another set of lowers, and it didn't come with a battery, so I do not have a top to build my own battery under. How would I go about building one from scratch? Is it possible?

Oh and I blame AO for that latest set. I was perfectly happy playing with just a Classic from '92 to '02. I came back last year, and now I have added an RT Pro, a pneumag, an E-Mag, and this latest set of lowers.

[ArmyEngineer]

Hey this whole DIY battery building business, is it under the assumption that you are starting from a dead battery, whose top you are reusing? Or is the top a generic part you can buy online too? I just picked up another set of lowers, and it didn't come with a battery, so I do not have a top to build my own battery under. How would I go about building one from scratch? Is it possible?

Building from scratch would be doable, but you would likely be better off buying one from KC.

This thread assumes you have a top from an old battery, and ideally the fuse. If you really want to build a battery from scratch, I can take some measurements of a top for you. You would probably be better off buying one in the long run.

[DoubleDutch]

Ok thanks. I think I will just buy one in that case.