It seems I have neglected the BMS side of documentation for our DIY portable power projects using lithium and lithium iron phosphate batteries.
The video is an extract of the full DIY solar generator video, released mid-february 2019. The rest is a discussion on wiring the BMS, and why to use one.
One of the biggest points of contention in the DIY portable power projects, is the use of a BMS for lithium or lithium iron phosphate batteries. Despite all that, the reasons to use a BMS are pretty obvious for those of us willing to do a little research.
There’s one thing I want to address with this BMS post, that’s bottom balancing. Bottom balancing is said to be an alternative to using a quality BMS. This isn’t actually true. The reason we use the BMS is for maintaining the balance between our cells. Moreover, we use a BMS for short circuit protection, high voltage or over voltage protection, and for low voltage and/or low voltage disconnect. None of these things are addressed by bottom balancing our cells. So even if we accept bottom balancing as an alternative to a BMS, we still need to address the other functionalities we lose by not implementing a BMS into our portable power builds.
Why so expensive?
By default we are usually pretty frugal people. We want to build things as cheaply as we can, but we can’t always see the benefits of spending the extra bucks for the security and redundancy we require. When looking at the DIY portable power section of this website, you’ll see projects using lithium or lithium iron phosphate batteries. For each of those projects I needed to research the best BMS to use. I ordered BMS boards matching project specs, only to find many of them were incorrectly labeled, simply not documented well, or even counterfeit. We can definitely find a BMS board for a few bucks on eBay. We may also find our “cheap” BMS board, doesn’t actually work. Unfortunately, that won’t be known until after a battery system failure! The time of a batteries failure is not the time when we’d want to find out if that cheap BMS, was working or not.
So, use a quality BMS to protect your battery investment, and your battery will reward you with thousands of recharge cycles, over many years.
BMS: Battery management
As with all my builds, the BMS is the heart of the storage system. In lithium based systems, the BMS takes care of:
- balancing the cells,
- provides short circuit protection,
- over voltaghe protection,
- under voltage protection
For the DIY Solar Generator, we are using the same BMS we used in the 10ah Headway LiFePO4 build, so we have more than a year of trouble free, rock solid experience with this board in the field, at the time of this article. We are also lucky to have a ham radio operator in the USA supporting this project. He has sourced the boards from the manufacturer, making it easier to optain the board for diy builders. This supports the project, but also provides a trouble free source for the boards at a reasonable price.
The board is available from ebay and delivered from the United States
Bestech BMS – Worldwide ebay listing