FABULOUS - You can't beat nature. We'll not be aiming to replicate this 100%, but doing an interpretation based on likely evolution with a lot of artistic licence thrown in. As you will see from the sequence below, there is quite a lot of engineering to make a decent frame to work from. We do encourage robot enthusiasts to build their own robot (DIY) and for that reason we explain how it is done. You should though be aware that you will need a workbench, vice, pillar drill, welding equipment, grinders, files and more. If you cannot weld, that is the first hurdle - or ask us to make one for you. It may work out a lot cheaper than equipping a workshop - it is though a lot of fun making a robot yourself - and you will need some handyman skills, even if we make the big steel parts for you.

CHRISTMAS GIANT ROBOT ANT PROJECT - POWERING UP

What is the run time of our robot? How long is a piece of string.

The answer to that question depends on the energy storage technology used. In the old days it was lead-acid batteries or nothing. Then along came fuel cells, but so far that is just an expensive pipe dream that we would like to see mature. Today there are dozens of battery formats. We need to differentiate between primary and secondary cells.

A primary cell is a battery that is designed to be used once and discarded, and not recharged with electricity and reused like a secondary cell (rechargeable battery). In general, the electrochemical reaction occurring in the cell is not reversible, rendering the cell un-rechargeable, so single use.

A rechargeable battery, storage battery, secondary cell, or accumulator, is a type of electrical battery which can be charged, discharged to drive a traction motor, and recharged many times. Primary cells are not generally used in vehicles, except for toy cars and robots, etc, because of the high cost.

Secondary cells are more practical and can provide significant storage capacity. Capacity versus mass is the challenge in the modern world, especially for electric cars that need a lot of energy for a sensible range.

TAIL SUSPENSION - The battery power pack is located in the tail of the DinoBot. In order to protect the development gel cells (and any other energy storage medium) the tail bearing is rubber bushed and the whole tail assembly, including protective bodywork, is further cushioned with a nylon-bushed coil over shock-absorber suspension strut. As you can see from the photograph this unit is adjustable for ride height and ride hardness.

SECONDARY CELLS

In the quest for more storage, Lead-Acid gave way to Nickel Cadmium (NiCd) and NiCds gave way to Nickel Metal Hydride (NiMH). Then Lithium Ion (Li-ion) came along and gave way to Lithium Polymer (LiPo) actually lithium-ion polymer. Of this latest chemistry there are constant improvements all of which is good news for roboteers.

CHOOSING A FORMAT

Choosing a format is all down to your budget and the purpose of your robot. For development purposes we would suggest using lead acid gel cells, then a move to LiPos. One recent development that has caught our eye is the new lithium cells from Steatite that currently provide a 1.2kWh auxiliary pack weighing 16 kilograms.

In 2014 partners OXIS developed their largest Lithium Sulfur cell achieving in excess of 300Wh/kg. This out performs Lithium ion technology that has dominated the performance battery market for many years. In addition OXIS achieved an increase in cell capacity to 25Ah a cell – a world first. Working from this (twelve-fold) achievement OXIS predicted they would achieve a cell capacity of 33Ah by mid-2015.

The OXIS scientific team expects to achieve a goal of an energy density in excess of 400Wh/kg by the end of 2016 and in excess of 500Wh/kg by the end of 2018. Working from that achieved, we might see a 3.0kW/hr pack for our giant robot ant weighing just 10kg (22lbs), or even a 42kW/hr pack for our Eco car, weighing 140kg (306lbs). Wow!

Steatite Batteries
Ravensbank Business Park, Acanthus Road
Redditch, Worcestershire, B98 9EX.

Tel: 01527 512400

Web: http://www.steatite.co.uk/

Web: http://www.steatite-batteries.co.uk/
Email: sales@steatite-batteries.co.uk

LITHIUM POLYMER BATTERIES - SPECS: Weight: 340g (12 ounces), Capacity: 9800mAh, Type: DC 12980, Size: 135x68x24 (mm). Built-in ON/OFF switch to save power usage. Input voltage: 12.6V. Output voltage: 10.8~12.6 DC. Product life: Circulation charge and discharge ≥500 times. Constant draw per battery is only 2 amps. 

R/C POWER - Various Chinese makers produce these high performance LiPo packs putting out 8.8wh. They weigh 41 grams each. 244 of these weigh 10kg and give us a 2.15kW/hr pack for £1,460 - available off the shelf with a delivery time of under 21 days. Direct from the makers, the price will of course drop. For a car such as our Ecostar DC50, a 21kW/hr pack would only weigh 100kg (220lbs) and cost £14,600 (without bulk discounts).

The SI base unit for electric current is the ampere. 1 ampere is equal to 1000 milliamps, or 1 amp. Thus a milliampere hour (mAh) is 1000th of an ampere hour (Ah). An ampere hour (abbreviated Ah, or sometimes amp hour) is the amount of energy charge in a battery that will allow one ampere of current to flow for one hour.

LEAD ACID (AGM) BATTERY - We will also be testing these YTX9-BS Powerline lead-acid 12 volt units. They measure: Length 150 mm x Width 86 mm x Height 107 mm and have a capacity of 9 Ah with a CCA of 180 amps. Absorbent Glass Mat, or AGM technology became popular in the early 1980s as a sealed lead acid battery for military aircraft, vehicles and UPS to reduce weight and improve reliability. The acid is absorbed by a very fine fiberglass mat, making the battery spill-proof. This enables shipment without hazardous material restrictions. The plates can be made flat to resemble a standard flooded lead acid pack in a rectangular case; they can also be wound into a cylindrical cell. NASCAR and other auto racing leagues choose AGM products because they are vibration resistant. AGM is the preferred battery for upscale motorcycles. Being sealed, AGM reduces acid spilling in an accident, lowers the weight for the same performance and allows installation at odd angles. Because of good performance at cold temperatures, AGM batteries are also used for marine, motor home and robotic applications. 

Four of these batteries weigh 10.4 kilograms, or 22.92 pounds. That's quite a lot of weight to justify on this robot, but they are very economical @ under £60.00 delivered - a no brainer for development purposes. Tayna Ltd., Central Warehouse, High Street, Abergele, LL22 7AR, United Kingdom. Phone: 01745 823399  Fax: 01745 832527

LITHIUM ION MOTORCYCLE BATTERY - Again and to compare, consider these Shido and JMT 12 volt units. They measure: Length 114mm x Width 71mm x Height 106mm and use the latest LiFePO4 technology. These units do not have much in the way of active lithium, but are more a large plastic container designed to mimic the original motorcycle battery - meaning that the quoted weight of 0.4kg is confusing to those estimating performance from mass. 

Here is a way to get a perspective on the energy density of lithium batteries. A typical lithium-ion battery can store 150 watt-hours of electricity in 1 kilogram of battery. A NiMH (nickel-metal hydride) battery pack can store perhaps 100 watt-hours per kilogram (although 60 to 70 watt-hours might be more typical). A lead-acid battery can store only 25 watt-hours per kilogram. Using lead-acid technology, it takes 6 kilograms to store the same amount of energy that a 1 kilogram lithium-ion battery can handle. [These are averages]

A BIT ABOUT Li-Po BATTERY BANK CONFIGURATION

If you're new to lithium polymer/LiPo/LiPoly batteries, there are some terms you will should know before making any choices.

When you look at a LiPo battery data sheet or casing info, you will see it has a lot of specifications. These are important apart from being your guarantee of performance from the manufacturer. Batteries are made up of cells whose voltage is determined by cell chemistry and whose capacity is determined by energy density and the physical size of the cell.

Cell arrangement - The cell arrangement is described using the format xSyP (where x and y are integers and S stands for series and P stands for parallel). This tells you how the cells in the battery are wired up.  Series connections adds the voltage of the cells together, and parallel connection adds the capacity of the cells, so a combination of cells in series and parallel results in a battery - and this is how you can make a pack to suit your application.

Capacity - Usually measured in mAh (milliamp hours), this is determined by the cell arrangement (parallel) and tells you how long you can expect the battery to last on a charge. 10,000mAh as shown on the battery in the picture below is equal to 10.0Ah (amp hours), a format you may be more familiar with on larger batteries, like the SLA (sealed lead acid) one in your car, which is probably around 50Ah. A capacity of 10,000mAh means that the battery can discharge at 10.0 amps for one hour (hence "amp hours"), 20 amps for 30 minutes or 5 amps for 2 hours, before it runs out of "energy." 

Voltage - The voltage of a battery is also determined by the cell arrangement (series), and there are a few common voltage measurements worth noting:

1. Charged - the voltage of a fully-charged LiPo cell is 4.20V, charging above this will damage the cell.

2. Nominal - this can be considered a sort of "half-charged" voltage, as it is 3.70V, in between charged and discharged. Nominal voltage is what manufacturers use when describing the voltage of their batteries.

3. Discharged - the voltage of a discharged LiPo cell is 3.00V, and discharging below this will damage the cell irreparably.

Where the battery shown above has a 6S arrangement, it is marked with its nominal voltage of 22.2 (3.70V x 6 cells). A fully charged 6S pack is 25.2 volts and a fully discharged 6S pack is 18 volts.

NEW TECHNOLOGY STORAGE MEDIUM - PERFORMANCE

According Cella one gram of their material produces up to 1 litre of hydrogen gas. This gives the method a high specific energy, making it ideal for mobile applications where weight is crucial, provided that the logistics of replenishment can be solved economically, where at the moment a fuel cartridge might function as a primary, rather than a secondary cell.

The cellular material can be packaged in combination with a fuel cell, to offer three times the specific energy of a lithium-ion battery. You could look at it that the system is comparable to 700 atmospheres of compressed hydrogen but without the safety concerns or cost of infrastructure, save that replenishment is more akin to a primary cell situation - and for this reason, may only be useful for a high speed runs - for record setting purposes.

This is the nano-fiber material that the whole system is based on. Apparently the fibers are 30 times thinner than a human hair. They may be rolled into pellets, which can then be transferred using ordinary vacuum pumps. A development of this technology could be the energy cartridges of the future for transport applications

LINKS & REFERENCE

Steatite UK Ltd/
Steatite batteries UK

http://lynchmotors.co.uk/

http://lynchmotors.co.uk/

This website is Copyright © 2024 Bluebird Marine Systems Limited.   The names Bluebird™, Bluefish™, Miss Ocean™, SeaNet™, SeaVax™ are trademarks. All other trademarks are hereby acknowledged. The design of the Robot Ant on this page is design copyright © December 15 2015, all rights reserved - Jameson Hunter Ltd. IMPORTANT NOTE:  Under no circumstances may our products, or those of Jameson Hunter Ltd, be used by any military or law enforcement organization, for any warlike, combat, or peacekeeping crowd control purposes. Anyone purchasing one of these units will be required to sign a binding undertaking (Deed) to that effect. Any unit found to have been purchased by proxy, will be confiscated, along with civil remedy in respect of breach of contract, that all parties in the chain will be vicariously liable for - to include damages for vehicles developed from our designs without our consent - and possible fraud issue from the deception. In addition to copyright theft, the law of passing-off applies.