I received this question from via facebook. I thought I’d go ahead and use it to make a point. We’ll keep the person anonymous, for the sake of objectivity.
Before we begin, Power Queen is the LiFePO4 battery recommended for those not wanting to or perhaps can’t DIY their LiFePO4 battery and BMS themselves. If fact, at these budget-friendly prices, one would be hard pressed to find valid reasons not to try the Power Queen LiFePO4 option.
Power Queen LiFePO4 batteries.
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Julian the company Bioenno power put out a few battery as stated from there website and I am wondering what the benefits and drawbacks of this would be. Some models of batteries including the 12A, 15A, and 20A. 30 Amp and 40 Amp PCM/BMS boards have been installed.
Claims the battery constant maximum discharge is 20, 30 and 40amps
And peak discharge is 40, 60 and 80 amps.
Would this be of any benefit to build a battery like this?
Almost every lithium iron phosphate or lithium ion battery sold commercially, has a BMS integrated. The exception to this rule is Hobby type batteries. Some batteries omit the BMS protection because they’re generally being charged through a balance charger. The end-user also uses an alarm to let them know the battery voltage has reached a critical level. These batteries are usually cheaper, but as mentioned, don’t offer any protections for the end-user. The BMS featured in other packs, isn’t a special feature, it’s simply a way of protecting the cells. The BMS is used for:
- Balancing the cells
- Low voltage protection
- Over-voltage protection
- Overcurrent protection
- Short circuit protection
A quality BMS will have all of these listed features, while lesser spec units, will have only a few of them.
Understanding maximum current discharge rate.
We can see from the specs of these batteries, that the cells used to make up the Bioenno packs, may not be the highest quality. For example, if we look at my 10 amp hour DIY project, that battery has a continuous output current of 50 amps. To achieve this 50 amps current draw, we make up the pack using cells which can output 100A continuously, and provide 150A pulse discharge for a very short time. I designed the pack to limit the maximum current draw from the pack to half of its continuous current draw capability. This is done for the longevity of the pack. The BMS also needs to handle the desired current discharge rate. This is why we put a 60 amp capable BMS in the high current capable DIY projects. It is the BMS (if using one) which limits or allows the current from our battery.
Commercial manufacturers are often concerned about their bottom line. In order to make up a battery pack, they make up packs using very low spec cells, and very low spec BMS. It’s important to understand not all manufacturers are doing this, but there’s an art or “interesting trick” to doing it from a commercial perspective.
Low spec cells can be combined in parallel, to achieve the desired maximum current draw of the pack. For example, in that 10 amp hour pack, Headway 38120 cells in 4S configuration are used. If we stayed with the same cells, but put an additional set in parallel, we would have 200-amp continuous current draw capabilities. Add another set in parallel, and we would have 300 amp continuous current draw capabilities, and so on. On my Channel, we always design and build these batteries, so that they’re never pushed to their limits. A company working for profit will use lower spec cells to make up the battery packs, giving you the illusion of a high-quality cell inside. If they also use a substandard BMS, the capabilities of that pack will be artificially limited, for the sake of making profit. This is one of the only ways Western companies, can compete with their Chinese counterparts. Moreover, if they built their packs according to the specs on my channel, the commercial price for those packs would be unacceptable. However, the prices are coming down!
Hopefully you didn’t miss the point here. It’s also possible for you to do a DIY project with less than the highest spec cells. All of my DIY projects are designed so that you can substitute what I’ve chosen, with the most cost-effective, or highest quality, cell available to you. Essentially we use exactly the same tricks to reduce the cost of our packs, as companies like Bioenno do, to increase their profit margin. Does that make sense?
There are other companies which use quality cells to build their packs. Those companies will proudly tell you which cells are used to make up their packs, in the packs documentation. Dakota Lithium is one of those companies, but there are many others. Go check out the specifications for their battery packs. I don’t mean to battery packs already integrated in to a Pelican case type enclosure. Just the raw packs. Compare the specifications of those Dakota lithium packs with the packs of Bioenno. Then compare the specs of those packs versus the DIY packs you’ve seen on my channel.
Regarding the advantages and disadvantages of commercial packs. First of all it’s important to remember, “companies work for profit”. There’s absolutely nothing wrong with that as long as they give you a product you’re happy with, and a product which allows them to make profit. Their job is not to give you the best battery money can buy. Their job is to make you think you’ve gotten the best battery, with at least amount of money. With all that said, the benefit or advantages of commercial batteries is having them in a self-contained enclosure. All the hard work is done for you, so there’s no soldering or anything like that. All you need to do is integrate your new battery, with your power distribution system. That’s the part of your system that will supply power to your radio. Some operators simply connect a radio directly to the battery. That’s a personal choice.
One of the main disadvantages of commercial batteries is not being able to open them up for troubleshooting or repair. As amateur radio operators we are naturally a curious bunch. Nobody wants to throw away something which has a minor fault. Instead we want to look under the hood, see if we can repair it, extending its service life a little longer.
Regarding the DIY battery projects on the channel. All of the Headway based battery projects on my channel, exceed the specifications of Bioenno batteries. My 10A pack can discharge at 50 amps “continuously”. Once you get past the “peak discharge” marketing, to make you think you’re getting more, you can start to understand the benefit of choosing your own components, and building your own packs.
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