Right in time for the start of the outdoor season Team Nosram’s Alexander Hagberg did a comprehensive TC Stock 13.5T asphalt outdoor test with his XRAY X4 in Lisbon/Portugal and shares his findings with you below and in his YT video

„Making the correct battery choice can be difficult, but I will give you some suggestions which can help you to choose better.

First, which batteries do NOSRAM offer for TC outdoor spec racing? Here they are:
• All the batteries are the same length, the industry standard of 139mm.
• The difference comes with the height and weight of the batteries.
• The 6100 pack (#999655) has a height of 22.5mm, and a weight of 273g.
• The 7400 pack (#999652) has a height of 25.1mm, and a weight of 302g.
• The 8100 pack (#999656) has a height of 25.1mm, which is the same as the 7400, but with a weight of 327g.
• The 9400 pack (#999654) has a height of 25.1mm, which is the same as the 7400 and 8100, but with a weight of 335g.

I would say that the rule of thumb here is that the thinner the battery, the higher the IR numbers will become. IR refers to internal resistance, and you want this number to be as low as possible. A lower IR number is
important to achieve the best possible punch, and least possible drop off during a run.

The benefit of a lighter and thinner pack, however, is of course, a lower CG (center of gravity) in the car, which
will make the car more reactive, more responsive, and will overheat the tires less than a bigger battery.

So – this is the tricky part. How do you make the trade-off between the best possible handling from
the chassis vs. the best possible punch and least drop off from the battery?

I would say that for lower grip tracks, the benefits of a lighter pack, in terms of handling, will often outweigh the increased punch benefit from a bigger pack. I experienced this at my home track last weekend where I went quite significantly faster over a 5-minute run with the 7400 pack, vs. the 8100 and 9400 packs. I preferred the 7400 pack, and here’s why. There’s this one corner at the bottom left part of the track which is a fast left-right transition. The car would always get a bit loose there with the 8100 or 9400 packs, whereas with the 7400 it was a lot more stable, and I was able to stay on the throttle longer through that section, which helped to lower the lap times.

However, if you race on open tracks with good grip, especially if you’re racing at a high level at international events, such as ETS or a European Championships, for example, the situation is often a little different.
You may be fighting with drivers for the win, separated only by tenths of a second after the 5-minute run. This is where the drop off from the battery becomes particularly critical. If you’re able to maintain more punch than your competitors in the last two minutes of the run, it can often help you win valuable time.

So, my initial suggestion, for lower grip tracks, especially if it has quick left-right transitions, you may prefer the 7400 battery.

For tracks with good traction, and with high competition levels, the 8100 or 9400 may be preferable.

How do you make the choice between the 8100 and 9400 though? Some of the NOSRAM team drivers are using this method for their racing program:
• 8100 packs are used for seeding rounds where you need to set 3 fast consecutive laps, and the overall finishing time of the run isn’t important.
• 9400 packs for qualifying and final rounds where the last two minutes of the run are critical.
This is one way of approaching it, and I have to say, it’s a very good approach which I will apply myself to whenever I compete in spec classes in the future.

The 6100 pack is generally used for indoor racing, and is typically too small, and not strong enough for outdoor racing, unless if you’re racing on a very small outdoor track where outright power isn’t as important.

I hope that this information was clear and will be useful for you when choosing your NOSRAM battery packs.“