The nomenclature for batteries is confusing and evolving. There are a lot of batteries similar to a CR123 available but the battery noted above is NOT rechargeable.
Here is some info copied from LightHound.com concerning small cylindrical lithium batteries:
The primary difference between the Protected and Unprotected batteries is that the protected batteries have a small circuit board, typically on the bottom of the battery, that stops the charging or discharge of the battery in certain circumstances. Some of the circumstances in which the circuit include: Over-Charge, Over-Discharge, Short-Circuit, and in some cases, overheating.
CR123a batteries, which power most Lithium-powered flashlights produce 3 volts of power per battery for most of their useful life. CR123a batteries have been in production for more than 20 years, and they are very safe and reliable. Unless the metal body of the battery is ruptured, or the battery is burned in a fire, these batteries are very unlikely to have any problems.
These batteries should NEVER be recharged, they will probably explode if you try to recharge them.
Due to the high cost of powering flashlights with CR123a batteries, the battery industry has developed a new class of batteries known variously as R123, R123a, RCR123, RCR123a, 16340, etc. batteries. Though these batteries are about the same size as the common CR123a batteries,
most of the rechargeable batteries produce 4.2 volts of output when fully charged, so they will instantly overpower and destroy flashlights and other devices that are designed for CR123a batteries.
The most common Li-Ion batteries on the market are the RCR123 PROTECTED 3.6 volt lithium batteries. These batteries have a very small circuit inside of them that shuts them off in the event that they are over-charged, over-discharged, overheated or short-circuited. These batteries are the best choice for most applications. These batteries require special chargers that are specifically designed to charge lithium rechargeable batteries. (Rechargeable 3.0 volt batteries are also available.)
Other Li-Ion rechargeable batteries available today include the CR-123 size 3.6 volt UNPROTECTED lithium batteries. They produce 4.2 volts of power when fully charged, then quickly fall to 3.6 volts output. They output 3.6 volts until they are mostly discharged, at which point the voltage falls rapidly.
If they are discharged below 3 volts, they will be ruined and no longer usable. The user must be very careful not to let this occur. These batteries should only be charged in a charger specifically designed for them, as those chargers have a circuit that stops charging the battery when they reach 4.2 volts.
Size Chart
This is a chart that illustrates the approximate sizes of the various rechargeable lithium batteries. The numerical designation of the battery gives an approximation of the size. For example, a 10280 battery is approximately 10mm in diameter and 28mm tall, the final 0 indicates that it is round. Please note that the sizes are approximate, and some batteries, especially protected batteries, may be too large to fit your particular application.
10280 battery - 10mm x 28mm (1/2 AAA size)
10440 battery - 10mm x 44mm (AAA size)
14250 battery - 14mm x 25mm (1/2 AA size)
14500 battery - 14mm x 50mm (AA size)
16340 battery - 16mm x 34mm (nominal CR123a size)
17335 battery - 17mm x 35mm (nominal CR123a size)
Size 16340 (CR123a) rechargeable Li-ion batteries are readily available in 3.0 volt and 3.7 volt, protected and unprotected, in the U.S. from online vendors. I don't know if any of these have magnetic + and - poles. Some U.S. based vendors will not ship outside the U.S.
16340 (CR123a)
3.7V rechargeable batteries are available at
http://www.lighthound.com/AW-IMR16340-5 ... _2626.html
http://www.orbtronic.com/two-protected- ... harger-kit
http://www.orbtronic.com/cr123a-soshine ... ctive-case
http://www.ebay.com/itm/4x-123A-CR-123A ... 20f068b6ca
16340 (CR123a)
3.0V rechargeable batteries are available at
http://www.amazon.com/UltraLast-CR123-R ... B00081I7EC
http://www.amazon.com/UltraFire-CR123a- ... roduct_top
http://www.all-battery.com/rcr123a30v90 ... ttery.aspx
Concerning the size 10440 rechargeable Li-ion batteries currently used in MagRacers:
These come in both protected and unprotected versions. They also come with a magnetic and non-magnetic + pole.
The longer protected version will fit in the battery compartment of the chassis if the the magnet in the end of the compartment is pushed toward the outside of the chassis just a little. Then the short or long version of battery will fit. The protected version is too long to fit in the transmitter controller.
The type with a magnetic + pole is needed for the chassis. It seems that the way to tell that the pole is magnetic is to note carefully the appearance of the pole. In the photo below, the battery at the bottom has a magnetic pole. The one at the top does not.
See also
viewtopic.php?f=10&t=241
TrustFire makes both protected and unprotected 10440 Li-ion batteries. It also makes batteries with and without magnetic poles. I don't believe that the color of the battery is relevant. I have not been able to find unprotected batteries with a magnetic pole for the chassis.
Protected batteries with magnetic poles can be found at
http://www.amazon.com/gp/product/B00KTT ... UTF8&psc=1
and
http://www.ebay.com/itm/4x-10440-600mAh ... 1354074862
In my opinion the current 10440 rechargeable battery provides plenty of run time, especially since it is so quick to change out.
The same battery could accommodate a narrower chassis if it were mounted diagonally or longitudinally in the chassis.