I need a Lithium Battery Charger

[chinaguy]

Dear All,

I ordered 5 sets of Lego Mindstorms 9797 that came with Lithium Battery Pack and I didn't notice that the AC Charger was not included. It will take several weeks for them to be delivered to me here in Shanghai. Can anybody tell me what AC charger I can use until the ones from LEGO Land arrive.

What Voltage and Ampage so I can buy or build one!

[mattallen37]

9-12v ac 7va.

[chinaguy]

Hi Mat,

Can you check the 7va, should that read 7ma?

[mattallen37]

No, it is AC, not DC. It is 7va. If you charged the battery at 7 ma, that would take about 215 hours to charge (actually more, because of the circuits involved)

I just realized though, that you might have the newer one; the very light colored one. That one requires 10v DC (possibly regulated), and I am not sure about the current.

[chinaguy]

Hi Mat,

Yes the battery pack is almost white in colour and it does have 10V DC stamped on. So anybody else have information on the charger?

[mattallen37]

Okay, sorry for the confusion.

Perhaps you could rig up a 10v DC regulated power supply for it. Make sure to provide enough current to keep it at 10v though (500ma-1A I am guessing).

[mattallen37]

Okay, I think I found the answer. According to a picture, I think it is 10vDC 7va. Based on this, I think it is 10vDC 700ma. I am not sure if it is regulated or not.

[nxtreme]

Be sure to stay away from cheap power supplies. They will be rated at 10V, but will put out 15-18V. Get something of at least decent quality. Switching power supplies are best, but can be hard to find at times. If you're up to a little hacking, a computer PSU works quite well. They usually have several voltage levels available, 3.3V, 5V and 12V (along with negative values of those voltages). The 12V rail would work just fine, just run it through two or three diodes to drop the voltage a bit. However, that might be a bit extreme , especially if you should be able to find a good 10V power supply for fairly cheap.