Learning by doing.
Two weeks ago I wrote an article titled “My Choice for Batteries”. Click link for article. It explains my though process when it came to deciding on a specific vendor and battery type for the battery pack I wanted to build and ultimately re-sell from my e bike shop in Carlisle, PA. As I said in my first article I ordered my supplies from ELifeBike.com in China. They have the most basic of web-sites and do not carry a wide range of products. The web-site also does not have the additional product information or instructions that people have come to expect from a web-site. They did have for download what I would call Identification Charts for showing which wires did what. A thorough search of the Internet proved their legitimacy and did not find any negative commits. They also had just what I needed for this order and with excellent prices on their products and shipping charges I decided to go for it.
Since this is my first battery pack build (outside of SLA batteries) I had decided on what ELifeBike calls a DIY Battery Pack for ebikes. I thought this would give me a good list of all the items I would need for building future battery packs. However, having purchased and built dozens of electronic kits over the years, what I got is not what I expected. More on that a bit later.
I placed my order on Saturday evening 8/18/12 and it arrived the following Friday on 8/24/12. This order also contained an e bike kit. Because of the HAZMAT RATING in shipping lithium batteries I was afraid the e bike kit would arrive much later but it didn’t. It all came well packaged in one big box. The packing slip matched the contents, matched my order and the pricing was exactly as promised. So far so good.
The battery portion of my order was called a 24V 10AH HEADWAY LiFePO4 Battery Pack DIY kit for ebike. It consisted of the following:
8 38120S 10ah Headway LiFePO4 batteries
1 charger: 120W 29.2V 2.5A
1 BMS: 12S 30A-60A
Since I plan to use these packs on bikes I sell or upgrade for my customers, appearance is second only to performance. Consequently the next most important step was finding a suitable container for the batteries and the BMS. If they fit this step was already done however, as I had purchased some heavy gauge zippered canvas bags about a year ago. These where old but never used first aid kits I picked up at a neighborhood flea market/yard sale for $1 apiece. The bags measured 8″ x 6.5″ x 4.5″ high. When I bought these I was sure they would hold up to 18 Li-Ion cells. Well they just might have but these Headway Batteries are LiFePO4 cells and they’re BIG. They measure 1.5″ x 5.8″ with the screws in place. My $1 bags where just big enough to hold my 8 (25.6v)
batteries which is what I needed this time around. Unfortunately they’ll never work for the 36v packs I wanted to build next. The bags zip open like a clam shell and have a large pouch across each side. Four batteries fit into each side with room in the middle for the BMS. However by the time I sandwiched the BMS between two pieces of Plexiglas and a layer of closed cell polyurethane then placed all the wires and a charging terminal inside things became a bit tighter than I wanted. (see photograph) The beauty of this arrangement is it opens like a book making service a snap. For someone like me that’s constantly tinkering, testing & trying to improve things this is great. But it’s also their downside. There is no need to open and close this case very often, and the ease of a zipper may be to great for my customers who want to start poking around in there. If I can come up with an attractive solution for storing or mounting the charger plug I might just zip tie the (2) zippers together along with some type of seal. When all was said and done it opened and closed they way it should and with the wrinkle black finish I applied to the top half of the bag it looks pretty good. Once I get a proper key switch and some black zip ties I’ll remove all the excess wire and tidy up the appearance a bit.
I still have quite a bit of road testing to do yet as I need to determine things like; time & distance, does the BMS shut down the power when it should, how warm does the BMS and batteries get on a hot day during hard use, how long does it take for a full charge, etc.
Now … going back to my un-met expectations lets examine ELifeBike’s DIY kit. From this order and other orders I have received from small companies in **China it appears as though the English word “complete” might translate into some thing more like “has all the major components” or “contains most of what you’ll need”. I expect something advertised as a kit to be just that. It would contain all the pieces & parts you’ll need INCLUDING DETAILED INSTRUCTIONS. All that you should need is solder, additional wire depending on the installation and some type of enclosure. You’ll also need a solder gun & a few hand tools. I would also recommend a multimeter. If the kit is complete and has clear instructions this is an option. My kit was far from complete. Since I have a complete shop stocked with parts and a lot of experience the missing pieces were not a big problem, but it still added to the time it took to build. The lack of instructions was however a problem. As I said earlier I had never built a power pack with this type of battery. It’s much more difficult than building a power pack with SLA batteries. This lack of instructions added many hours to the job.
After I test this kit a bit more I’ll provide some feedback on how well everything works. I’ll also include a complete list of the parts you’ll need to build a LiFePO4 battery pack. My next purchase will be a couple of e bike kits with battery packs from E-BikeKit.com & I’m anxious to see how they perform next to LiFePO4 batteries. In the mean time let me tell you what I know for sure about DIY battery packs.
DO NOT BUY a LiFePO4 DIY KIT if your only reason is to save a few bucks. You won’t & you very well could spend more. Hook up a wire wrong or accidentally create a momentary short and POOF, … there goes your BMS. Purchase a good quality complete battery pack instead. Do your homework though. The Internet is flooded with cheap battery packs. One that I personally recommend is E-BikeKit.com. They have recently added ALLCELL Technologies lithium-ion (Li-Ion) Battery Packs with a proprietary PCM. (see below or click link for more information) to their line-up of already great e bike kits and e bike accessories. I’ll have more on this in future articles as my next purchase will include these batteries from E-BikeKit.com. Near the end of this article I’ve included a short listing of vendors selling finished battery packs I know to be trust worthy.
Regardless of where you purchase your batteries you have to know what you need, what you’re getting and where to go if you have a problem. I have visited dozens of sites with exaggerated claims and vague details. They deceptively sell LiFePO4 cells and finished battery packs using another type of lithium cell on the same page.
IF …… However, your purpose is to learn by Doing, DO NOT DO IT WITH A CHEAP KIT FROM CHINA! Even if supplying your own connectors, wire and materials for building the BMS enclosure doesn’t seem like a big deal to you, working without instructions or at least a wiring diagram will be. I’ll say it again, Hook up just one wire wrong, even for a second and you will fry your BMS. It’ a proven fact that Learning by Doing is the best way to absorb information. But it doesn’t have to be painful or expensive. Instead, purchase a quality kit from a place like Headway Headquarters, LLC. If it where not for their excellent web-site with instructions and pictures I would have had an even bigger problem than I did. Jim and Patricia where also very prompt in responding to my request in the beginning of this process when I was still deciding on a vendor. Although the batteries are the same their kits are much better. For starters, Their kits are complete. In comparing their parts list to the parts list I made of what I WAS MISSING, the two lists are nearly the same. In addition their BMS board appears to be superior to the BMS board I received. It carries a higher rating and looks to be better built. Also their battery charger comes with a proper looking 3 pin xlr connector and the kit has the matching end. Mine came with what looked like an oversized RCA connector and no matching end.
Supplier List for assembled LiFePO4 battery packs with BMS. Please note that E-BikeKit uses Li-ion batteries:
- E-BikeKit.com uses Li-Ion battery packs made in the USA by ALLCELL TECHNOLOGY. It has a higher energy density (smaller lighter) than LiFePO4 but has had safety concerns in the past related to heat issues. ALLCELL claims to have solved that issue by using their proprietary Phase Change Material to absorb and dissipate the heat.
- Battery Space
- The Grin Cyclery
- Ping Battery (Direct from China. Quality can be hit or miss)
**China: There are a lot of high quality parts and equipment coming from China. China is the leading producer of e bikes, e bike kits and batteries. Many of the e bikes and e bike components you purchase from the USA, Canada, Australia and Europe are completely or in part manufactured in China. The problem with these products is a serious lack of regulations, enforcement of those regulations when they are in place and very little if any consumer protection. When a tiny start-up company begins operations and starts selling it’s products overseas it simply doesn’t have to worry about the consequences of selling poorly built and falsely advertised products. Consequently the temptation to cut corners in order to raise profitability is huge. When it comes to buying products from China it is much safer to purchase those products from a trusted source with a proven track record or better yet your local e bike shop. In addition, for small orders, when you add in the cost of the freight to the product it is most likely not much cheaper anyway. That’s my opinion.
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