C Rating of a LiPo Battery
In a previous article we talked about how the highest C rating has so many benefits that it makes it well worth it. However, because of all of these benefits, some LiPo manufactures use the C rating as not just a performance specification but more as a marketing tactic. This can make it very challenging for users such as us, to make a good selection for our true requirements. Some manufactures are recognizing this and try to provide the market with extra performance metrics that are not so vague. Also, the metrics provided by some manufactures are a lot more easily proved by consumers. Examples may include a simplified load test or using the internal resistance of the batteries cells.
What can you do about inaccurate C Ratings?
There are a few things that you would be able to do to help reduce chance getting stuck in these claims. The biggest and easiest method to avoiding these risks is to simply review the product reviews. Check what others are saying to see if the pack lives up to the standard you expect. Similarly, it is a good idea to check the forums to see what kind of reputation the LiPo manufacture has. Not only that but you may also run in to seeing what the popularity of the pack is. If many are using the LiPo and happy with it, chances are, it’s OK. Last item is to see if you can get any information as to the internal resistance of the pack. Using this data to compare against another pack, can tell you what performance to expect, Lower internal cell resistance will provide better performance. Check out this link to help determine the actual C rating of a LiPo.
Capacity of a LiPo Battery
There is no set standard to how a LiPo manufacture determines the capacity of a battery pack. Due to this, there is some variability in this performance specification. Some LiPo’s may not be able to deliver anywhere near their rated capacity. Now fortunately for us, the modeler, we can more easily prove and confirm these specifications just with the modern computer radio!
Capacity Varies Under Load
Yes, it’s true. Your 5000mAh battery may have just accepted 5000mAh that your charger put in to it. However, if you load the pack with a very light load you may get the full 5000mAh back out. Now if that load were to increase, you would get less total capacity out of the LiPo pack. This relationship is true based on how much load is placed on the pack up to a certain cutoff voltage.
This occurs as the minimum voltage of a LiPo battery comes in much quicker under significant load due to voltage drop. This is something to consider depending on the total amount of power that you RC vehicle will pull.
Soldered LiPo Battery Connectors
Many of the LiPo battery packs deliver some impressive numbers in terms of discharge current rates. Some of these rates easily exceed 100A continuous. However, In many cases you could see a high performing battery use such small wimpy connectors. Yep, it’s true. LiPo manufacture may choose to place small connectors on LiPo batteries for a few specific reasons. These reasons are primarily due to the market demand and cost. Some smaller connectors are more widely used. When a manufacture supplies a battery pack with a smaller more commonly used connector, less hobbyists would have to unsolder the connector only to replace with one of their own. The second primary reason manufactures may place smaller 60A connectors on a battery that can deliver well over 100A is purely due to cost. Smaller more popular connectors are inexpensive by nature. Reducing cost allows the manufacture to sell the battery more competitively and we in return get the pack for lesser overall cost.
In general, I replace the connectors on more than 75% of the LiPo battery packs I purchase. This is because primarily, I use an old connector that is rarely used these days. I also prefer a beefy connector for minimum voltage loss.
Wire Gauge used On the Battery
Very similarly as above with connectors, it may be possible that a manufacture chooses to use a gauge of wire that is smaller than what would be expected. However, the big difference here is that if you are going to be pushing packs extremely hard and want top performance – select a battery that has the wire gauge you are looking for. Otherwise what you may find yourself doing is re-soldering cables.
As for my setups. It’s rare that I run in to a situation where the wire on the battery pack is not large enough for my application. in general for most hobbyists out there, it really won’t make much of a difference at all. Wire gauge is a topic for the experienced hobbyists, otherwise run what you have.