With a decade of EU restrictions on Nickel Cadmium (NiCd) batteries and the superior abilities of Nickel Metal Hydride (NiMH), lighting battery packs have evolved!
DMS technologies’ marketing manager, David Claxton, explains. “When we started building battery packs over 25 years ago NiCd battery packs were one of our leading product lines. Today very few customers continue to use NiCd with the majority of our OEM users having moved to NiMH and, more recently, lithium chemistries.”
David points out that there are other benefits beyond the environmental and legislative. “The energy density of NiMH cells is higher resulting in smaller battery packs and ultimately smaller end products. This reduction in product size for the same capacity is enhanced by a lower cost per unit. NiMH even offers a better power to weigh ratio – completing the ultimate goal of smaller, lighter, cheaper!”
The 50% greater energy density in NiMH cells is demonstrated when comparing C size cells; NiMH offers 1.2V 4.5Ah as opposed to NiCd offering 1.2V 3Ah. DMS believes this offers two alternative benefits. They believe the most obvious is to continue with the same capacity and reduce the size of the battery pack and possibly the overall equipment. DMS also illustrate an important alternative and that is the benefits possible in using the same physical size batteries. This may not only be easier in legacy equipment but it also increases electrical performance. By replacing a 3Ah pack with a 4.5Ah and maintaining the same discharge profile the depth of discharge is reduced by a third, thereby extending the life of the pack – further reducing costs.
It is worth noting that another benefit with NiMH is that they don’t exhibit the memory effect characteristic. Memory effect was found in NiCd battery packs where they were repeatedly recharged after being only partially discharged. This meant that the battery packs only seemed to “remember” the smaller capacity being regularly used. To avoid this is was necessary to ensure NiCd battery packs were fully discharged before being fully recharged. This effect is not present in NiMH batteries and they can be cycled at any depth of discharge – lower depths of cycle will actually improve the overall life expectancy.
While memory effect does not occur with NiMH batteries, the charge regime is still very important. DMS technologies look at individual applications to match a suitable charger to ensure that the benefits available from NiMH are not diminished. Generally speaking the older NiCd chargers are not suitable for NiMH batteries and will either under or over charge them depending on the settings.
“Differing charging regimes do need to be taken into account when considering swapping chemistries” David Claxton points out. “The Sales team at DMS all come from engineering backgrounds and their aim is to partner customers to ensure transitions to new battery packs or technologies run as smoothly as possible. We can support altering charge profiles or providing new chargers – we aim to be more than just a battery supplier and offer real added value service.”
Concluding our discussions on battery packs, David Claxton went on to say “While NiMH manufacturing techniques and designs are continuing to evolve and ultimately further improve the technology, lithium is the latest buzz word in the industry. While the word lithium is a generic term covering a wide range of different lithium chemistries designed for different applications, some of the key benefits are the same. They have a very low self-discharge rate, usually offer further weight saving combined with higher energy density and a better cycle life.” David does point out “The disadvantage to lithium remains cost but depending on the application this is often a case of OPEX vs. CAPEX.”
DMS technologies have been building battery packs since 1986, they are based at a purpose build facility in Romsey Hampshire accommodating both long and short run production lines. They design, develop, manufacture and test specialist sophisticated battery packs and DC power systems for applications ranging from industrial to military to rail. These markets demand high quality and their ISO 9001:2008 accreditation supports their claims of high quality products coupled with excellent customer service.
The Sales team impresses with their philosophy of building relationships with customers, working with them to ensure the best solution is found combining technical and commercial demands. The team can be contacted regarding new products, replacing old technologies or alternative supply on existing battery requirements.
