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Team Tornado Battery Test 2002: Conclusions
Comparing the heavier (6kg+) batteries first, it can be seen that the cheaper Lead Calcium types (Kiel, Dryfit and Portalac) do not perform spectacularly - they have a high internal resistance and deliver a poor capacity of only around 1.2Ah/kg (the Dryfit is particularly bad given how expensive it is!). Compare these to the Genesis and Odyssey 16Ah Lead Tin batteries - in all cases these have a lower internal resistance, and deliver a better capacity of about 1.4-1.5Ah/kg. The Odyssey in particular is worth noting - it delivers a final capacity of nearly 10Ah, pretty spectacular for a 16Ah SLA!
Comparing the remaining (lighter) batteries, the old style SBS15s perform pretty well, although these are no longer available and the ones tested here are the six remaining "good" ones from our original nine. The newer SBS15s are dissapointing, with similar efficiency to the cheap and cheerful (and small) lead calcium Diamec - newer type SBS's are not recommended for use in robots therefore. However, the best of the bunch is the Genesis 13Ah - it has similar efficiency and internal resistance to the 16Ah Hawkers, but is a fair bit lighter.
The low current tests show the difference between low current "backup" type batteries and the high current delivery Hawkers - the measured capacity and efficiency of the Portalac (and to some extent the old SBS15s) increases dramatically at low current, while the 16Ah Hawkers do not improve proportionally that much (although in all cases the measured capacity is greater, as would be expected).
It is worth noting that since these tests were performed, Hawker have again rearranged their battery lineup. The SBS15 and Genesis batteries in future will be aimed at low current and backup situations, and although currently they are all the same batteries internally, the internal construction is going to change. Hawker (and Hawker dealers) will only provide warranties on Odyssey batteries for high discharge cyclic applications, so if you are buying new Hawkers, you need to be buying Odysseys! The Odyssey range consists of the following: PC535 (14Ah), PC545 (13Ah), PC680 (16Ah), PC625 (17Ah), PC925 (26Ah), PC1200 (42Ah), and PC1700 (70Ah). The PC925 is probably the largest battery anyone would want to use in a heavyweight robot!
Remember also that the results should be scalable for different batteries within the same ranges as those tested - i.e. a 26Ah Odyssey is still going to be much better than a 26Ah Dryfit!
Team Tornado Battery Test: Recommendations

If cost is important, and you're not likely to draw a lot of current (e.g. you have a 2WD robot with a non-electric weapon), then lead calcium type batteries such as the Kiels, Steatites or Portalac should do the job. You won't have quite the best performance, but you'll save a lot of money. Alternatively, any of the Hawkers in good secondhand condition will be a good buy.

If you want the ultimate, then go for the Odyssey batteries from Hawker. You might consider the PC545 (13Ah) instead of the PC680 (16Ah), both perform very well and are available surprisingly cheaply from Knight Batteries.

If weight is important, then you need the Hawker Odyssey PC545 (13Ah). It's not worth wasting your time with 12Ah lead calcium batteries or the Hawker SBSs, unless you only have a 2WD machine with wheelchair motors.
See our Suggested Suppliers list for details of where you can buy the Hawker, Kiel and Steatite batteries.
Team Tornado Battery Test: Postscript
We have performed initial tests on Nicad "Battlepacks" (many thanks to John Reid from Terrorhurtz for lending them to us). The results show that when sufficient packs are combined in parallel (4 parallel packs), then the performance is equivalent to the same voltage series combination of Hawker Odyssey SLAs, but with a significant weight saving.
However, paralleling batteries is a dangerous thing to do if you are not extremely careful, and there are many pitfalls. See our Background Information page for details of the problems you could have. The cost of Nicads and the chargers you must have to charge them properly is a lot more than SLAs, and Nicads have a finite maximum output current, so if you peak current demands are very high, you will need even more packs in parallel. For all these reasons, we will continue to use Hawker Odysseys.
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