I've learned a lot in the past week in researching batteries and packs from PHET due to several requests I've had from people who were interested. I thought I'd share the good and the bad about working with PHET and their LiFePO4 batteries.
First of all, I'll be upfront that we're going to be selling their ebike packs so the reader can know my biases - they're the most nicely designed and packaged LiFePO4 e-bike/pedelec packs I've come across (a few pictures on my website. No duct tape here - it is a professional design on a mounting rail in a pretty solid package that should withstand years of ebike use (with 3 yr warranty). I am using one daily on my CurrieUSPD 36/48V BMC setup, and am happy with it. Not only is the exterior design solid, but the electronics and protection devices appear to be top notch, both in terms of operational characteristics, and from an aesthetic perspective when I opened the pack up (pictures on the website soon of pack internals). Based on that, I decided to order more of them to sell to others here in the USA, since I want to make this kind of technology available to the people who don't want to fiddle with things, but just want a nice, lightweight pack that works and integrates with a bike well.
Given that I was already dealing with PHET, several people inquired about larger packs for scooters. I did some research into this, including getting several quotes from PHET on these packs.
The bottom line is, PHET packs for larger vehicle use are an expensive proposition. The reason is this: all PHET packs for EV use are designed around their prismatic 18650 cells (at least, that's the only thing they've recommended and said they will warrantee for EV). These cells are 3.2V 1.2AH, slightly larger than an AA battery. To build up larger packs, they place them into 3.2V strings, each with a voltage balancing board, and then for higher voltage, place these strings together using a battery management board. For my ebike pack which is 36V 7.5AH, they used 72 of those cells. This may have the advantage of better thermal transfer (higher surface to volume ratio), and more fault tolerance, since so many cells are connected in parallel. But, it has the disadvantage of high cost, particularly for high capacity systems. This is because PHET gives little price break even for 100's of cells*, and each pack requires multiple VBB and BMS boards, along with all the soldering and etc. The cells themselves are $5ea, so for a recent 51V/44AH pack I had spec'd out, the cells alone were ~$2,900 (576 cells * $5 each), and that's wholesale price with no markup. The VBB and BMS units, along with labor for pack assembly, adds another $1,200 (the only way to get the warrantee is to have PHET assemble the pack). And, PHET apparently has no means of economically shipping these in less than container load quantities, other than Fedex overnight (I have inquired several times, and they tell me they can't find an economy shipper who will take batteries!). So, after shipping, the cost of a 51V/44AH pack was going to be around $3,800 (again, wholesale without any markup for us).
Since the above prices are already so high, we can't really make any kind of reasonable margin on these for our efforts in getting quotes for people. So I decided to just share the information here for anyone who wants to contact PHET directly to have a custom pack built. Right now they don't differentiate between wholesale and retail buyers, which is another downside for us dealing with them (but could be good for the motivated buyer, who's willing to wire transfer money to them 1.5 months in advance of receiving the pack - no credit card or buyers protection option there!).
I'll also say that they don't seem quite ready for these kinds of small scale transactions yet. They don't have any kind of dealer support or differentiation between dealer and retail prices, they don't have any economical shipping set up, and on several occasions my inquiries have seemed to stymie them. Their USA division is Shoprider, and I think they haven't figured out whether to eventually start selling the batteries through that division, or what. When I inquired about the lack of wholesale/dealer pricing, they mentioned that this was still "in discussion" and that they were trying to figure out whether to make sales through Shoprider. The following story further adds to this point.
PHET also makes a line of e-bikes that we inquired about, and they told us to get in contact with Shoprider USA if we wanted to obtain them for selling in the USA market. When we did, Shoprider quoted us "wholesale" prices that were more than 2X the wholesale price on the bikes direct from Taiwan. The markup was far more than shipping and customs fees - plus we would have had to pay additional shipping from California to the East Coast. The quoted wholesale price was akin to typical retail prices for quality ebikes from reputable sellers here in the US. I found out the difference between the Shoprider/US price and the PHET/Taiwan price because someone from the Taiwan division sent me their prices, not knowing that I'd already been quoted a price by Shoprider USA. Needless to say, I wasn't pleased, especially given that this is for a low-power ebike (~250W) with only 5AH battery, brushed motor, and etc. Strangely, there is no mention of these bikes on any of their websites (Shoprider US or PHET) - but they do appear to be selling them in Europe - there was a recent review of them by Extraenergy.org. And, the retail price in Europe is not a lot higher than the "wholesale" prices quoted to us here. In any case, I don't think they've figured out how to deal with the US market yet for anything but their medical mobility devices, which they seem do be doing quite fine with.
Someone recently asked me where the motivation was for PHET to develop these LiFEPO4 cells in the first place, and I think it was because they wanted to have batteries that were a) significantly lighter than lead acid for their mobility devices, and b) extremely safe for medical compliance (no good having batteries that might explode or catch on fire in a nursing home!). I think they have realized that there is a big market now for these batteries aside from mobility devices, but haven't figured out a business model for how to scale that up and truly penetrate the market here in the US with them. Once their production capacity goes beyond their sales demand, they'll probably start thinking about that problem a lot more, and perhaps we'll see some changes in both the pricing and dealer support. But for those who are hoping for a short-term reduction in price, I'm not so sure. It seems that they have a lot of demand for now, even at present prices (it took them 1.5 months to get my first e-bike battery done).
In any case, I think that PHET makes top-quality batteries, and I'm excited about the e-bike packs. But I thought I'd put all this information out there for anyone interested in working with them to build custom packs, since it is not worth it for us to mess with that right now. I'm happy to give contact information, or you can find it on their website, and they'll usually come back with a quote within a few days.
I hope the info helps someone.
*I have asked PHET for a quote on a very large volume of cells to see if there is a price break.