def215 wrote:im just curious to how the performance of the NI-MH's are like on your Dayglow Avenger MkII amberwolf. how are they treating you?
It's ok; better than SLA for sure. Only catch is charging them requires either:
--A NiMH specific charger that is capable of monitoring it's temperature/voltage/whatever, so it doesn't overcharge and damage it, especially to prevent it overheating.
--You paying close attention to it while charging so you don't overcharge/overheat it
--Always only charging at very low currents (like 100mA or so) for a long time
--Using a thermal cutoff like Knuckles, preferably several of them in series, scattered throughout the pack. (there's always a sensor in the middle or so for chargers that monitor that, but if it breaks or comes loose it doesn't help!)
Or some combination of the above.
So...it works for me so far, but I am always a little worried about it when I have to charge it faster (at about 900mA, fastest I can with the Sorensons) due to needing it quicker than just overnight. Usually I use much less power, and can let it charge about 150mA or less, and it'll be about perfect by the time I have to leave the next day, if I do. (if i don't, I just unplug it).
As an example of use, today I ended up making two back-to-back 6-mile trips, and was about 13-14MPH anytime I could stay at one speed, with lots of traffic control stops (a few dozen). One trip was loaded up heavy, about 40+ pounds of stuff for the 3 miles back. The outbound was empty (just me and bike) as was the second trip both ways. Took about 3.4Ah out of the pack to do the whole 12 miles (bringing it up to 120 miles total on the motor/pack since I got them). Forgot to write down the Wh.
The only big problem I have with it is the sag--it was already used when I got the pack, so it's not as healthy as a new one, but the sag is pretty bad (a few volts) during draws of 2C, about 16A, which is what it takes during heavy acceleration on the "low" setting of the Fusin. It still accelerates well enough, since it's a geared hub, but using it on a non-geared would probably not be as forgiving due to higher current draw likely needed.
NiCd is similar in properties to NiMH, and probably easier to get a pack (ebikes.ca has them). Never used them myself.
But if you want a lightweight pack that can take high current draws, Lithium of one flavor or another is the only good option I'm aware of. Just expensive. Still working on getting mine built up.
SLA will take the high draws with little sag, depending on the size of battery vs draw, but they're really heavy and suffer horribly from Peukert.
id like to try and get a pack for my bike because im not ready to go lithium yet, for financial reasons and for the fact i tend to be neglectful(i forgot i left a soldering iron in the wall overnight the other day. imagine if that was a lithium battery, that situation couldve turned out bad
Well, Nickel isn't a forgiving chemistry either. If you have a good BMS and a good charger, Lithium wouldn't be a problem, but then the same is true of Nickel. The real problem is that most of the chargers are really cheap, and don't have proper safety features or they are made so poorly that the features can't work or just plain break.
If you really want a chemistry you can just leave charging, Lead is probably the only one that doesn't just die from it, simply because once the charger reaches the max voltage, the charging current is very low, if any.
(same could be true of Lithium, but I think most chargers are setup expecting a BMS to shunt for a while to balance, and that will still eventually overcharge the pack).
ive ran across a thread knuckles made about building a NI-MH pack out of 10000mah tenergy and powerizer cells and said he had good results out of them. id like to try and do that but everyone doesnt even look at them and say just to go lithium.
I personally don't think Tenergy is worth the powder to blow them up based on all the overhyping I've read of them over the years, vs what their cells will actually do.
Sanforce supposedly is pretty good from what I have read around; I have one of their 24V 13Ah packs, which before it was accidentally overcharged/overheated by it's previous owner due to a thermistor failure, was apparently a very good pack. Now it has bad sag at only 7A or so, but that could happen to any NiMH that's been overheated.
I forget what Giant used to use in their packs; but that's what is on the bike right now--a Giant D-type 36V 9Ah pack.