I think I will plan to drop in the 48v set that I have so that I can get the bike up and going and gain the benefits you point out. I am sure that my for-real pack won't be lead-acid, though: there is not enough of a cost benefit if I don't build on the existing batteries, and the existing batteries are not technically sufficient. So I will ride around on 2/3rds power with some weak batteries for a while- better than nothing! I will ride lithium in the future. I need high power for my pack size, so it looks like I am going with either Lipo or a high-power 18650. Kyle, you mentioned some that were notable- any links? How do they compare in terms for $/wh?
Yep totally agree with you. Lithium for the win.
Originally Posted by nedfunnell
I have seen some 18650 cells priced at around $0.30-0.40/Wh in QTY of 1000 cells (~8kWh) shipped to the US. You still have to package them which can be done in multiple ways. This was through a company called Keeppower and direct from Asia. You can also look at supowerbattery111 on ebay they sell to a lot of guys on ES and will do some spot welding services for free.
Since you need high power I'll only list a few cells that I think would work off the top of my head.
Sony US18650VTC3 or VTC4 or VTC5
Samsung INR186500-20R or 25R
All those can peak somewhere between 15-20C and can do 8-10C cont at least
How well do cells like that stay in balance?
That's too general of a question. Depends on many many things (chemistry, how they are first balanced, c-rate duty cycle, temperature, cell quality, DOD, etc.).
Originally Posted by nedfunnell
I would go as far as saying that these cells would stay as balanced or better balanced than RC LiPo
Got it. I was wondering if I could reasonably stick with top balancing for these or is they necessitated a BMS more than lipo. (Some think everything needs a BMS, but that is for another time). Buying enough 18650s to make a sufficiently powerful pack puts me back in the Leaf-module budget range, though, so it's probably lipo after all. I hate to have to wait weeks and weeks to get them, though. At least I'll have my slow, heavy bike to keep my company while I wait.
Well, I have to report that I am doofus. The lead acids may be dead. I left them in the go-kart project over the winter. It was difficult to measure the voltage on the cells because I had everything buttoned up, so I just measured the voltage on their sister battery that was not installed- it was (and is) perfect, so I assumed they would be fine too. I had them isolated with a Hella switch, but I guess some power continued to flow through the precharge resistor... for months... because I started to remove them yesterday and found them all at 5.x volts. DAMN.
So now I've got no good immediate battery solution, unless these come back from the dead in a miraculous way. I put them all on charge immediately, and we'll see how they hold voltage, and if they can deliver any current. I doubt, though, that they are fit for duty.
HobbyKing is OOS on the 4s hardcase packs in both their US and international warehouses. Dang. Now I wish I had just jumped on those renault cells, I could have been riding by now.
Kyle, do you think those 16 EIG cells you have would get me through a riding season? 16s/18.5ah gives about a kwh. Could they handle the discharge?
I diagnosed the Longma hall-effect throttle as bad today. It was getting 5v and returning ~50-80mv regardless of throttle position. I pulled it off and diked out the 5v supply that went with it. In the process, a wire pulled out of its molex pin in the connector to the DC/DC. I took the pin out, recrimped it, soldered it, and did the same to the other pins on the connector. Be advised- "Green Galaxy" brand DC/DCs seems to be sketchy to me. This crimp job was bad (I should know, I spend two says dialing in a Schleuniger StripCrimp 200 last year) and if you peel the paper label off, there is chinese writing on the case with a different voltage range than the paper label states. It works, so maybe the innards were changed and the OEM label wasn't. I'll worry about that later.
So, I tried a 5k Radioshack pot as throttle. No dice, as the controller was programmed for 0-5v (I thought it gave two blinks, it was really three, which is 0-5v). I broke out my USB-to-serial cable which I had ordered just for such an occasion and subsequently had no luck getting it to play nice with Windows 7. I have a Windows XP desktop in my office, so I had to decided if I wanted to:
* Bring the PC to the moto
* Take the controller out of the moto and bring it to the PC
* Bring the moto to the PC
I chose the latter:
I had been programming off of my cordless drill battery and an SLA (~33v) and I couldn't figure out why I was getting no motor activity, no voltage drop, and no current flow even when I had the pot hooked up correctly, and the Alltrax showed a yellow LED indicating full power flowing. Well, I realized that 33v was not enough voltage to pull the 60v contactor. I added another SLA and got the satisfying click I needed, and wheelspin! Hooray! Throttle problems can now be fixed simply by installing a Magura. (Like I'm going to spend $90 on a Domino!)
In other good news, the place I got my batteries from (Chrome Battery) offered to warranty my dead SLAs! So I can ride on 48v after all- hooray! If you need SLAs, buy from them.
In the best news of all, I pitched my battery project to my local hackerspace for a 'makership' and won a 3 month membership! I'll have access to all of their tools, equipment, and knowledge. Sweet!
Pardon my verbosity, I have benefited from others' verbose forum posts in the past, and maybe this will help somebody else out later.
Now I just need to find some LITHIUM. Anybody got any leads? This project is going nowhere fast without some lithium!
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Do you have any local (or whatever you guys in the states call nearby) ev nuts (cars and bikes). Then one of the best options would be to call some scrapyards for Leafs Volts(europe the opel ampera) to find a battery pack.
I emailed a local wreckersyard here in the Netherlands, 2500 euro's + 60 euro's shipping for a complete Opel Ampera pack. 16 kwh of oem goodness with contactors and all, it would cost around 160 euro's/Kwh.
So if you find a few buddies who are willing to commit to buying parts of a car pack, this is one of the cheapest ways to go.
HECK YES! I found another source of Leaf cells in my price range. Among my many mottoes is a key one here: "Good things come to those who wait." Of course, there is also "Why the heck not?" to balance that one out, but the waiting seems to have paid off this time.