Breakthrough in Rechargeable Batteries for Mindstorms

NiZn Batteries
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There has been a Breakthrough in Rechargeable Battery technology which is very applicable to powering you LEGO Mindstorms Robots. The new 1.6 Volt Nickle-Zinc (NiZn) have reached the market place. Unlike other rechargeable battery types, a set of six NiZn batteries gives an output of 9.6 volts, instead of 7.2 Volts. As a result, the NiZn batteries equate to a set of six Alkaline non-rechargeable batteries, in both power and performance.

1.6V NiZn Batteries

Nickel–zinc batteries have a charge/discharge curve similar to 1.2 V NiCd or NiMH cells, but with a higher 1.6 V nominal voltage. Nickel–zinc batteries perform very well in high-drain applications, and because of their higher energy-to-mass ratio and higher power-to-mass ratio (up to 75% lighter for the same power). NiZn are also lower in cost as compared to nickel-cadmium batteries, and are priced somewhat higher than NiCd types at this point in time.

NiZn Battery Discharge Curve

The NiZn will be used as a substitute for nickelcadmium as they are a far greener alternative to NiCd batteries. The European Parliament has supported bans on cadmium-based batteries. The batteries made of nickel–zinc offers a very good alternative.

Battery life:

Compared with cadmium hydroxide, the tendency of zinc hydroxide to dissolve into solution and not fully migrate back to the cathode during recharging has, in the past, presented challenges for the commercial viability of the NiZn battery.[1][3] The zinc’s reluctance to fully return to the solid electrode adversely manifests itself as shape change and dendrites (or “whiskers“), which may reduce the cell discharging performance or, eventually, short out the cell, resulting in a low cycle life.

Recent advances have enabled manufacturers to greatly reduce this problem. These advances include improvements in electrode separator materials, inclusion of zinc material stabilizers, and electrolyte improvements (i.e. by using phosphates). One manufacturer, (PowerGenix), which has developed 1.6V batteries, has claimed battery cycle life comparable to NiCd batteries.[7]

Battery cycle life is most commonly specified at a discharge depth of 80 percent of rated capacity and assuming a one-hour discharge current rate. If the discharge current rate is reduced, or if the depth of discharge is reduced, then the number of charge-discharge cycles for a battery increases. When comparing NiZn to other battery technologies, it is important to note that cycle life specifications may vary with other battery technologies, depending on the discharge rate and depth of discharge that were used.

Courtesy of Wikipedia®

 

 

NiZn Battery Charger

NiZn batteries are well suited for fast recharge cycling, as optimum charge or discharge rate equal to the capacity of a battery in one hour. Known charging regimes include a constant current to the cell at a voltage equal  voltage = 1.9 V. Maximum charge time is given variously as 2½ hours and 3 hours. Trickle charging is not recommended, as excess hydrogen will eventually vent, adversely affecting battery cycle life.

‘NICKLE ZINC BATTERIES’ REQUIRE A DEDICATED NiZn BATTERY CHARGER!

 

I found the cheapest source for NiZn batteries was through eBay. I was able to pickup 24x 2800mWh AA NiZn 1.6V Volt Rechargeable Batteries and a Battery Charger for US$65.00 from GreenForceStoreAU‘s eBay Store. Currently the NiZn batteries retail at between $2.50 and $3.50 each. This price will of coarse decrease as the uptake of these new batteries increase. Even at $2.50 each, they are less than 50% dearer than quality non-rechargeable Alkaline Batteries.

At this stage, I am converted and won’t be purchasing toxic NiMH cells anymore! The real test will be over the weekend of the 20-21 April 2013 when my Robots will be on display at the TAZ-Brick Collector Club‘s 2013 Brixhibition being held in Launceston, Tasmania.

 

WARNING: Using ‘NICKLE ZINC BATTERIES’ (NiZn) with LEGO Mindstorms

It has been brought to my attention, that when a set of six fully charged NiZn Batteries are inserted into the LEGO Mindstorms Brick can cause an over-voltage. The total output of the six may exceed 10 Volts which is harmful for your LEGO Mindstorms Brick. If you subject your Mindstorms Brick to over 10.5 Volts, you will certainly DAMAGE it!

Dummy Battery
Dummy AA Batteries

To get around this issue, you need to only install FIVE NiZn Batteries and a DUMMY BATTERY should be inserted in place of one of the NiZn Batteries as used with ‘Li-ion‘ and ‘LiFePO4‘ type AA batteries. with an out put exceeding 1.5 Volts.

Dummy Battery Using WireLink
or Dummy Battery Using A Heavy Wire Link

Using the Dummy Battery or Wire Link with your Mindstorms Brick, you then ensure the maximum supply to it will not exceed more than a 9.5 Volts using five fully charged 1.6 Volt NiZn Batteries.

 

UPDATE:

The TAZ-Brick Collector Club‘s 2013 Brixhibition Launceston was a great success. Exceeding all expectations!

We were ran off our feet with over 15,000 patrons through the doors. People queued for up-to forty-five minute in order to get through the door due impart to the venue size, but mostly due to our very underestimated visitor predictive calculations!

The Ni-Zn AA rechargeable Batteries excelled at powering my LEGO Mindstorms Robots. They out preformed similar rated Ni-MH (& Alkaline) batteries by a significant amount. My robots ran for longer and faster. The Ni-Zn’s were comparable to using my 9 Volt, 5 Amp Mains Powered Adapters to run the robots.

Unlike other battery types, the Ni-Zn Batteries don’t gradually taper-off at the end of their discharge cycle, but jump off the “Battery Cliff’. They give very little, if any warning that they have emptied their resources. One minute your Robot is flying around the room, blink and all has stopped ready for the next battery swap!

I have also ran the Ni-Zn in my Olympus Professional Camera Flash Units with amazing results. The flashes recharge time stood at around a Seconds. Yes, a second from start to finish…

(There will never be another Non-NiZn battery ending up inside any of my camera equipment again).

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