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Currently I am using six rechargeable batteries for my Lego Mindstorms EV3.

A few seconds after I start a motor the EV3 gives a notification that that the battery is low.

I know that good batteries are alkaline ones. However, personally I want to avoid using them because I will need to throw them away after use.

  • We need more details - what motor are you running, which rechargeable batteries are you using? I have been running an EV3 on rechargeables (Duracell) for a while and get at least 2+ hours out of them - continuously powering 2 medium motors. So what you describe is not normal for standard Lego motors. – Phil B. Jun 27 '15 at 0:40
  • "Best" is a subjective term that we try to avoid. See bricks.stackexchange.com/help/dont-ask. It would be better if your reworded your question as something like "What are the differences between using Alkaline and NiMH batteries with the EV3? (And are there other types of batteries that work with the EV3?)" – David Lechner Jun 27 '15 at 1:14
  • @DavidLechner sorry for that. I edited the question. – Thomas Vos Jun 27 '15 at 6:09
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NiMH batteries only provide 1.2V per cell whereas Alkaline batteries provide 1.5V (nominal values). This means that new/fully charged batteries will provide a total of 9V for Alkaline and 7.2V for NiMH. The EV3 is programmed to show low battery somewhere around 6.2V and turn itself off around 5.5V. There is no option a available to tell the EV3 the difference between these two types of batteries. The EV3 was designed for Alkaline batteries. You won't get good performance from NiMH with the EV3.

LEGO also makes a rechargeable Li-ion battery pack. Being designed for the EV3, this battery is properly sized for comparable performance to Alkaline batteries. Be aware though, that this battery pack makes the EV3 one LEGO beam width taller, which could require some models to need to be adjusted to accommodate the extra size. Also, when you remove the batteries from the EV3, you will notice a small black circle in the battery compartment. This is actually a button that lets the EV3 know that the battery pack is installed rather than regular Alkaline batteries. This lets it adjust the battery gauge and low battery alarm for the slightly different voltages of the rechargeable battery pack.

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    The difference between alkaline and NiMH is not so clear: Good NiMH have a discharge curve flatter than alkaline so they may actually last longer (even if initial performance is lower than alkaline). See philohome.com/batteries/bat.htm. – Philo Jun 27 '15 at 5:35
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Another possible choice of batteries are lithium-metal batteries like Energizer Lithium Ultimate batteries. The performance to price ratio is better than premium alkaline batteries but worse than discount alkaline batteries (which often perform quite as good as the premium brands). I use them mainly because I can't be bothered by replacing batteries too often. Also their voltage level stays nearly constant until their charge is depleted, which is definitely not the case for alkaline batteries. For alkaline batteries the EV3 starts complaining while there is quite a bit of charge in the batteries left.

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