Kiel 18AH versus Hawker SBS15

Batteries constitute one of the major expenses and most confusing items required for a robot. Few teams can afford brand new batteries, and thus are forced to look at secondhand and surplus items. When we were looking to buy our original batteries back in 2000, several types with approval for Robot Wars use were available on the surplus market - these were the Hawker SBS 15, Kiel 18AH, and various Yuasa backup batteries. (Note that for a long while the Kiels were not approved, but as of 13/8/01, thanks to Team Killer Carrot who brought one in for Derek Foxwell to test, they gained official approval.)

We instantly dismissed the Yuasa types as they were much lower capacity, and being fitted only with 1/4" blade terminals, were obviously not designed to deliver significant current. Thus we purchased and tested a number of both the Hawker SBS15's (from Display Electronics - now sold out) and Kiel 18AH (from Bull Electrical). Based on a basic bench test, here are our conclusions - note that we are only comparing the available surplus/secondhand batteries available back in 2000 here.

Supplier Type Rated Voltage Measured Voltage Rated Capacity Measured Capacity (2ohms to 10V) - Average - Worst Weight Dimensions (mm) Terminals Internal Resistance Maximum Current Date of Manufacture Mass Efficiency (average) Price Each Price for 4 Approved for Robot Wars?

Hawker SBS15 Display/Distel Gas Re-Combination 12V 6V-12V 14AH 11AH 5AH 4.7kg 200Lx77Wx137H M6x10mm studs 0.02ohms @100A 550A/10sec, 20deg 6/95-10/95 2.3AH/kg £33 + VAT + P&P £99 + VAT + P&P YES

Kiel 18AH Bull/WCN Standard Sealed 12V 12V 18AH 14AH 14AH 5.7kg 175Lx75Wx175H plates with M6 holes 0.02ohms @100A 200A so I'm told 8/97 2.5AH/kg £15 + VAT + P&P £39.95 + VAT + P&P YES as of 13/8/00

Why we don't recommend the Hawkers from Display
Being of limited means (like most teams) we looked for cheap batteries from the surplus electronics companies. We bought a total of 9 Hawkers from Display and 4 Kiels from Bull. Out of those, two of the Hawkers have proved way below acceptable capacity, and despite returning these the replacements were just as bad (i.e. out of 11 Hawkers we have had in our hands, 4 have been duff).
It's not that the batteries are poor quality - far from it, when brand new they are excellent, and if you can afford to buy them new then they are way better than the Kiels. However, the Hawker SBS15 batteries being sold by Display/Distel are 5 years old and therefore not "brand new" as they are being advertised. Display refused to honour an offer they made to us after we complained that the replacement batteries were duff. I quote an email from Dave Fisher of Display: "As far as your batteries are concerned we are willing to issue a returns number and refund your carriage costs". We wanted Display to replace the duff batteries, but after more than three months of emails and phone calls, we had to involve Trading Standards in order to get a refund. (Please read our diary for more details.)

Our (original) recommendations

Based on what we have gone through, we strongly recommend that you do not do business with Display Electronics (Distel). We are not the only team to have had problems - others have had trouble with the gearboxes from Display.

If you already have the Hawkers from Display, check their capacity.

If you want to buy the Hawkers, buy them brand new.

If you don't want to risk buying surplus batteries, check out Steatite, they sound promising and are very cheap too! (17Ah 12v for about £20 brand new)

If you want cheap and useable surplus batteries, buy the Kiels from Bull or WCN (where they are £14.95 each).