Lithium Ion battery for the E/X-Mag?

[AGDRetro]

There's no doubt that battery technology has advanced from the time the E-Mag was initially introduced and I was wondering if there has been anybody that has looked into developing a Lithium Ion battery pack for the E-Mag.

You probably need to develop a new charger as well, but I think the increased shot count per charge and weight savings VS the stock NiMH might make this an appealing upgrade for E/X-Mag owners.

Thoughts AO?

[Levi]

There is probably a battery pack ready made for the RC Airplane and heli market that would be readily adaptable to the emag.

Plenty of charger options too. Would just take some research to find one that fits and at the right voltage. I believe the lithium cells come in at 3.7 Volts nominal. So you could expect to get packs in multiples of that voltage.

[Levi]

The lithium polymer cells are commonly used by the electric rc airplane and helis. These are popular because they lack the heavy protective casing around the cells. Since the E-Mag has a metal battery "case" anyway I see no reason that these batteries couldn't be used safely for this application.

If you go messing around with lithium batteries make sure you take some time to learn about their quirks and how to safely use them.

For instance, they like to catch fire if seriously abused. Also if they are over discharged there is a risk that they can catch fire when recharged. Or if they are charged with the wrong type of charger.

[BTAutoMag]

Someone get me some specs. I just happen to work for a conpany that makes lith car batteries. Ill talk to the engineer

[knownothingmags]

its hard to get the size right. 4 cell lipo is your go too.
3 cell would work i think at 11.1 v.
4 cell is 14.8 v
but with lip you need a cutoff installed so you dont balloon your packs and have it melt your gun when it goes bye bye.

ive been looking into getting packs that will fit but its really hard to get the size down.

the the MaH would be small. but that wont be an issue since the lipos would run you for days.

could get ahold or Orion, Maxxamps, Venom, etc, but they are big guys in the industry and an order would have to be for a 1000+ i think, if they could make 100+ for good price i may be able to buy em and resell to you guys.

issues:-
-size
-price
-cutoff for to save the battery.
-and hookup to the marker.
** question for the techs who know:
*_* can you opperate the emag off of 11.1 v? if so i will run testing.

[athomas]

Here is a copy of a battery pack explanation I did a while back.

A 4 cell pack would have a 14.8V nominal rating. 14.8V would cause a reduction in power by about 22%. That should still trip the sear, but it would cut into any buffer needed to maintain operational consistency in all instances. That means you better keep the mechanism clean. It would probably be better to add an extra cell.

Don't go exactly by the rating on the cells or packs. In reality, Lipo cells have a fully charged voltage value of 4.25V so most charger limit it to 4.2V. The minimum safe voltage is 3V so most use a cutoff of 3.3V. That gives a four cell pack a voltage range of 13.2V to 16.8V. The discharge line from 16.8V to 13.2V is fairly linear and results in the 14.8V nominal rating. The calculations show a 15V average but in reality its not perfectly linear so the real average is 14.8V.

NiMh cells have a fully charged voltage value of about 1.4V but it drops to 1.3V very quickly so the 1.3V value is used for the upper value when determining average operating outputs. The minimum voltage is 1.0V, but the drop from 1.1V to 1.0V occurs very quickly so the 1.1V value is used for the lower voltage. The resulting average is 1.2V which is the industry value used for packaging. A 14 cell pack rated at 16.8v actually ranges from 18.2V to 15.4V.

Checking the voltage values of the lowest value for each pack type, it shows a reduction in power by 27% for the LiPo compared to the NiMh pack. This is worst than the 22% calculated using nominal values. As the pack gets discharged, you might end up with firing issues using a 14.8V LiPo pack.

Therefore, I would recommend the 5 cell LiPo. The overall voltage will be a bit higher using the 5 cell LiPo pack. This will cause higher current draw which will heat the solenoid more. Its a 20% increase in power consumption when the battery is fully charged. I don't think the dwell of the solenoid will allow it to catastrophically overheat. If it proves to be a problem, put a 5Watt 0.5ohm resistor in series with the battery pack. That will bring the pack down to the same operating parameters as a NiMh pack.

LiPo packs and lithium chargers in general are easily configured to be safely charged these days. An off the shelf RC charger has the ability to properly balance a lithium based battery pack and the packs have charge/discharge regulators built in so that you can't charge or discharge them past their danger point.

[Levi]

*_* can you opperate the emag off of 11.1 v? if so i will run testing.

If a 3 cell is all that could be fit into the Emag battery pack a voltage "boost" circuit could be added provided there is a little room left over.

There is always another way to skin the cat... it just depends on how much work one wants to do.

I just did a google search for lipo cells and came up with a few promising links but don't have the time to investigate in depth right now.

Could someone post the internal dimensions of the Emag battery?

[rukh013]

They have the 22v cell's I've done some searching and will post up links when I get home tonight.
I have noticed that the inside if the battery packs could be milled to accept slightly larger cell's or a whole new pack and battery combo


Where's Luke at?

[athomas]

You could build a voltage booster but they generally don't handle high currents. Starting with a lower voltage would require a higher current to maintain the wattage plus a bit more to allow for losses in the conversion. If you are going to add circuitry, consider using a solenoid with a rating closer to that of the lithium pack you want to use.

[Levi]

You could build a voltage booster but they generally don't handle high currents. Starting with a lower voltage would require a higher current to maintain the wattage plus a bit more to allow for losses in the conversion. If you are going to add circuitry, consider using a solenoid with a rating closer to that of the lithium pack you want to use.

That's a very good point. Not to say that a suitable boost circuit couldn't be built... but by the time you build one that can supply enough current at the required voltage the bulk of it may large enough that you haven't gained anything.

So far my experience with voltage boosting power supply circuitry has been limited to excercises that are just for curiosity sake. In all of my real world designs I have had the luxury of plenty of voltage overhead and I'm always stepping it down.

I just wanted to throw some ideas out there to maybe get some wheels turning in someone's head.

Your idea to swap the solenoid out for a lower voltage unit is promising. You would need to take a look at the driver circutry on the board and make sure that it is able to supply the additional current that would come along with a lower voltage coil. I don't have an Emag, otherwise I'd start pulling up some datasheets and checking this out myself just out of curiosity.

I'm just shooting from the hip here but if necessary, I suppose one could build a solenoid driver circuit that would do the job, provided there is room inside the grip for another small add on board.

[oldironmudder]

How about going green?

Goal-Zero-solar-charger-backpack.png

[blackdeath1k]

How about going green?

[ATTACH=CONFIG]87873[/ATTACH]

Isn't that what us with mechanical guns are doing.

[oldironmudder]

Isn't that what us with mechanical guns are doing.

Thats green before it was being green. So...... pick a color then. Ive seen dirt range from red, blue, green to orange.

[rukh013]

They have the 22v cell's I've done some searching and will post up links when I get home tonight.
I have noticed that the inside if the battery packs could be milled to accept slightly larger cell's or a whole new pack and battery combo


Where's Luke at?

Battery
charger shield
low voltage alarm

[athomas]

I'm just shooting from the hip here but if necessary, I suppose one could build a solenoid driver circuit that would do the job, provided there is room inside the grip for another small add on board.

The driver on the board is more than capable of handling more current, so a lower voltage solenoid at the same wattage is just a drop in part without any additional circuitry.

And a LiPo battery pack is a plug-in pack that has its own built in circuitry for charge protection. A new battery case with LiPo would be the easiest thing to make and it would be smaller and lighter than the regular emag battery and pack.