esr750 said:
My personal experience is that nickel (either one) chemistry isn't worth the cost and trouble. For practical e-bikes it's either lightweight or low AH using good old cheap SLA.
I've had a much difference experience with my NiMH pack. Over 3 years old and close to 500 charge cycles, still going strong. Light weight, no worries for recharge since I have two smart chargers for each pack. Low heat from both since I use large guage wire to try and minimize resistance. The last time I did a full 1C test on them, they still out perform brand new SLA of the same capacity, which surprised me.
Nickel stuff drains by itself just sitting, damages easily when recharged hot or overcharged/discharged, saves little weight compared to SLA and IMO is simply not worth the trouble or money for e-bike applications.
Not sure which pack you were using, but I've had mine sit up for over a month sometimes (winter mainly) and they are still strong when the weather finally warms up and I take them for a test drive.
High power lightweight lithium is the future chemistry but for now it's expensive and/or complicated DIY project.
I agree, but let's not throw away chemistry that is well proven and cheaper than the current lithium out there. We at least they use to be cheaper, seems prices for the NiMH are going way up lately
6 miles? Keep bike speed under 15 MPH and with a little pedaling you should be able to do that on 4-5 AH using 15A controller. My Panasonic (very efficient) regularly covers 8-10 miles level @ 15mph pedal assisting 230lb rider on barely 3AH battery capacity.
Yeah, 6 miles, some cheap SLA will be no problem. It's when you try to break the 20 mile 20 mph barrier it starts to get heavy and expensive.
At least with SLA it's easy to charge and a person can more easily keep hot batteries ready to go at home and at work, in the car or points inbetween. So cheap by AH comparison too. just keep 'em small packs or it will suck to ride and overload the chassis...
I'll have to disagree from personal experience. I have bikes that use both chemistry and SLA die quickly in the heat (brand new SLA mind you), unlike my NiMH (3 years old) counterparts. I've also found that mixing SLA with NiMH in the series results in the battery power not lasting as long. I figure it's because the SLA resistance increases quicker than the NiMH, they don't make a good combination.
As far as charging, both can take opportunity charges without any problems from my personal experience. Both can be charged while hot, the only difference is that a NiMH gets hot when approaching a full charge state. My SLA pick up some heat from a deep discharge state as well when going straight to full charge. Our sense of hot varies from person to person, I have to use a thermometer to set me straight. Often what feels like a NiMH pack that is burning is really only 110 degrees F or so. It's helped me to understand better what "hot" really is. I don't worry so much about my NiMH packs going nuclear. I figure it's already been 3 years and I would swear sometimes those packs were hot enough to fry an egg on, but they keep going strong. Mind you, they sit in the back of a bike pack with no ventilation what so ever. Great for the cool weather, murder in the hot weather. Which is why I suspect my SLA don't last long in the hot weather. The NiMH don't seem to care
Well anyway, what I was trying to say is I'm a big fan of NiMH because it's been good to me for many years without any problems. I've used SLA (AGM) much longer and they are what they are. Cheap and useful, but they do have their limits and I just don't want to haul around 50+ lbs of batteries for my bike. :wink:
But for the record, my NiMH packs are going on 19,000 miles right now. Well worth the $500 investment I made years ago.