Best batteries for the NXT

[bungeshea]

Hello
I am trying to find the best batteries to power my NXT. Currently I am using rechargeable alkaline batteries, but I read somewhere that because the alkaline rechargeable batteries are 1.2v and the recommended for NXT is 1.5v the motors will run more slowly. I was thinking of buying the LEGO rechargeable battery, but the battery and the charger have a combined cost of $150 AUD, and that doesn't include shipping! The 'LEGO MINDSTORMS NXT Power Programming: Robots in C' book mentioned that the LEGO rechargeable battery will have the same effect on your motors as alkaline rechargeable batteries. Can anyone give me some tips about which batteries would be better for my NXT?

[haydenstudios]

I like to use Energizer ultimate lithium for my NXT's:

They last about eight times longer, and are significantly lighter than regular alkaline batteries. Plus, using them alleviates my parents burden of having to purchase batteries every other time they visit the store! They're great, and I would recommend using them not only for your NXT, but for any other device that uses batteries quickly, like digital cameras.

[dimasterooo]

I was thinking of buying the LEGO rechargeable battery, but the battery and the charger have a combined cost of $150 AUD, and that doesn't include shipping!

Yeah the "new" one really is expensive. I got my "old" one from BrickLink (at BRICKSHOP holland) for about 70 euros, including the charger. So yeah I really like it, cuz I can just plug it in and keep going without having to buy new batteries all the time, but it's really about what you're looking for yourself.

[doc222]

This realy depends on use. E2 lithium's are very light half the weight of all other batteries plus they have about 1.7 volts(this is ok since the nxt can handle about 10.5 volts+-. THe bad is the cost alot and when done are in the trash. NXT up regular batteries, much cheeper, though they weigh 2x more. They put out the standard 1.5V, but end up in the trash as well.

Recharged types are the least expensive in the long run since they can be reused many times. they are heavy as well and only put out 1.2-1.3 +-V

Lego Lithium, same voltage as recharged but almost as light as the E2's Since these use on the inside of the case only 2 cells of 3.6V+- (standard fair for lithium) They could be the lighest of all but the platic case is an added weight. Last time I checked Lego was only a few grams more than E'2. But less power.

So what we have here is many choices but the real question is what are we doing? If say you must have light and power for reason, contest, the bot just can not carry the weight or you are tring to break a record.

Heavy batteries have a place too; when you need ballist to ballance a bot.

But for testing a bot or programming, or just fooling around the best choice is any recharged ones this way you can test and teat and program with out putting out alot of $.

I do not have the lego ones but I have 3 sets of recharged type. If I need E'2 I use them for the final run only agaian only IF it means a better time or the bot just can not handle the weight.

[jwiger]

doc222 is on the money. All types of batteries have advantages and disadvantages. Alkalines have have nominal voltage and a long shelf life as long as their still charged. The initial 1.5v can drop off quickly though and performance will be only slightly better than NiMH batteries. If you leave them in too long they will leak and ruin everything.

NiMH batteries as mentioned typically have a lower 1.2 volt charge, don't dump the amps as well as other batteries, and self discharge quickly if you are not using them often. But will easily recharge and will stay usable for years. Their capacity (mAh or Joules) is as good or better than Alkaline batteries, so they can do a lot of work if you don't have heavy loads on them.

Disposable lithiums have a slightly higher voltage (~1.6) which make for fast light machines, and they can dump a lot of amps fast (almost too fast) so they work great if you are using the motors hard. the rechargable lithium pack has similar benefits but the as you said the trade off is cost. I personaly don't care much for lithiums for regular use because they are "fragile". What I mean is they are sensitive to over charging and very sensitive to over discharging. If you run a lithium too low there is no saving it.

For mobile machines I like NiMH for regular use, they are cheap in the long run and very forgiving. They don't care if they are in the charger for 10 minutes or 10 days. Disposable lithiums are great when you need extra speed (or forgot to charge your NiMH batteries). Lithium batteries have a very long shelf life and self discharge very slowly so it's great to have some around.

I also like to use my dSolar a lot, it cost a lot up front but I don't need to go to the store to make it work! -I need to work out a way to plug stationary machines in to the wall. Does any one have a good solution for that?

[nxtreme]

I need to work out a way to plug stationary machines in to the wall. Does any one have a good solution for that?

If you're not afraid of a soldering iron, Philo has put together a really nice tutorial on creating a stationary power supply for the NXT. You do have to be careful you don't fry anything, but if it does work, it'll work well. http://philohome.com/nxtsupply/nxtsupply.htm

[mattallen37]

...I need to work out a way to plug stationary machines in to the wall. Does any one have a good solution for that?

Yup, Philo made a nice hack.

Edit: Oops, nxtreme beat me

Edit2: Xander uses the NXT battery pack jack as his external supply port for desk models. He seems to leave it plugged in, and it automatically charges when it needs to.

[muntoo]

I use 2500mA (1.2V?) Energizer Rechargeable batteries. I believe they're NiMH. They last a decent amount of time.

I'd try Rechargeable Li-Ion, if I were you.

[HaWe]

I need to work out a way to plug stationary machines in to the wall. Does any one have a good solution for that?

If you're not afraid of a soldering iron, Philo has put together a really nice tutorial on creating a stationary power supply for the NXT. You do have to be careful you don't fry anything, but if it does work, it'll work well. http://philohome.com/nxtsupply/nxtsupply.htm

what about buy an old Lego accu pack and plug in a charger? That's how I'm doing.

[nxtreme]

what about buy an old Lego accu pack and plug in a charger? That's how I'm doing.

Yes, if you have the money to spend, that's a great idea. I'd actually love to be able to buy a Lego LiPo cell and charger, but I don't want to spend ~$80 US just for an outlet powered NXT, especially since I already have three sets of rechargeable batteries for use with my NXT. Considering I could make something like what Philo made for about $10 US, I'll leave the LiPo cell on my "wishlist" for now . However, if you just don't want to risk your expensive NXT brick, it might be worth the money.