smallest usable battery for Giant Twist?

[prState]

First I wanted to say, I was really happy to find this forum after owning my Giant since 2003 in the U.S. I've never met another owner of a Lite here. In fact, in 4 years I've only encountered two other electric bicycles while riding in Las Vegas.

I've followed "powerassist" Yahoo newsgroup for a couple years now, and I'm usually disapointed to find ex-giant owners mostly, or suede, which I'm not familiar with.

***

Anyway, I have perhaps an unusual question, as people are often trying to find long amp hours -- but what is the smallest usable battery pack-- sufficient for short 1 or 2 mile fast trips? Would I be able to run the panasonic motor off two 12 volt packs from portable power tools for instance as that was my idea?

thanks
cg

 

[flecc]

I've never tried this cg, but there's no reason why it shouldn't work, the type of battery doesn't normally matter. You often wont get pro rata range though. In other words, a 3 Ah pack will usually give a bit less than half the range of a 6 Ah pack. The reason is that is that the smaller the pack, the more chemically stressed it's electrolyte is for a given application, and a small loss of efficiency results.
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[prState]

Thank you, Flecc,

I was hoping that it might work! So, now to do some shopping.

 

[prState]

I had been looking around for a 24 volt battery, and found 12 volt, 19.2 volt for power tools, but today an ad in the paper from Pepboys (auto place) has a 24 volt cordless drill for $20 after rebate. (I don't know the conversion). Anyway, I suspect it's a nicad. For the charger, batteries, and drill (which I can actually use anyway) it's a pretty good deal for an experiment.

So, I read up on nicads, and apprarently you can pretty much run them dead, so I can do an actual range test on my Giant, not that it will be anything scientific. (nicads can take up to 800 charges?? I wasn't sure about that info)

Still have to get a new tire though (why does Giant have tires for "electric" bicycles anyway; I've never really known the answer to that).

 

[flecc]

Nicads can take up to 1000 charges if used in ideal ways. It's important to near fully discharge them each use to avoid memory effect, but that won't be a problem with that pack in that bike. Nicad discharge rate is the highest of all batteries and only limited by temperature, and they can be fully discharged to empty every time, it's indeed the best way to use them.

Let us know how you get on.

I think electric tyres is just a gimmick, though it's just possible that they are designed to resist the wear on the friction roller type of add on bike motor like the Zap unit. I doubt those maxxis tyres would be much good for that though.
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[prState]

I picked up the 24 volt drill, and charged up the battery. Pretty sure it's nicad, from the directions. (there's no info about it other than charging directions)

Right now, other than trying to figure out the best way to affix it temporarily to the terminal posts on the bike, I have to go get another tire. The discount store tire decided not to match up to the Giant wheel, so I couldn't replace it. The size seemed to match, but the tire sure didn't. So, um, I guess I got what I paid for. It also comes from the same country as anti-freeze in toothpaste and melamine in dog food.

Anyway, I'm wondering if there is already some sort of pre-made electrical fixtures that will attach to the posts in the battery compartment other than trying to clip something on or even heavy amounts of electrical tape? I have one connector that sort of fits, but not very well.

 

[JohnInStockie]

Hi prState

I am thinging of trying a mod similar to the Grandad mod on my Twist, but with the idea of some form of additional parrallel battery connection if thats possible. Hopefully I could just have an external power connector so that I either just use a small light battery, or use the main battery and another battery to increase range.

Im still in thought mode and I know I will need much more advice before I know whether or not my idea can work, but as a starting point I am thinking of attaching the relay that grandad used in his mod (or similar) to be able to attach different / extra / alternative power supply. See his link here, it might be useful to you.

John

 

[prState]

Well, I had Wright Brother like success, so far, i.e., I got about 20 feet with the motor going before it cut out.

I think I did pretty well with wire connection to battery, but not so good with wire connection to the two poles on the bike. Trying to go with temp connections without being able to solder is a problem. I've tried 3 different methods, the last being the best, since it actually worked for a bit.

The thing is, even when you're using a meter to test a connection, you must be right on top of those things; there's seems to be no side connection, else, all would be too easy I guess.

I'm wondering if maybe I should try to take part of the inside casing around those things off, but I'm not sure how much of the outside case I may need to remove.

Well, that's all for now. 'Till I work something out.

 

[flecc]

If it's any help prState, this is what is beneath the covers on your Twist Lite unit. The terminal block is screwed up into the platform, and the two wires enter the unit at the side. As you can see, there's plenty of length so you may be able to pull out the wires sideways on the left hand side and tap into them rather than fully strip all the cowlings to unbolt the terminal block:

 

[prState]

Excellent! Thanks!

 

[prState]

Well, I stopped fiddling with the terminals, removed the left side cover and spliced into the wires, so I was able to make a test this morning.

Results: about 1/2 mile on mostly level ground. Basically, it went very quickly through the normal cycle. Sometime shortly before the 1/2 mile mark it went into slow blink mode, and a minute after that about, it went to quick flashing mode, and then shut down almost immediately.

I really doubt the pack was drained in that amount of time, and tried a few times to run it again after a rest, but I really didn't let it rest more than two minutes, so maybe it had more to give, but for practical purposes it seemed shut down for any immediate use.

When the bike started out, there was no stutter or anything to indicate I wasn't using the normal Twist pack, however a pack that small is probably not too much value to anyone. Even though I don't have a super accurate weight, this power pack weighed just around 1 pound on a bathroom scale. I suspect, it has the bare minimum of nickel cadium AA batteries to make the 24 volt requirement.

I suppose, based on this info, I suspect, if you were going to go with a very small pack, I'd at least double the number of batteries.

 

[flecc]

That matches my experience prState, only pairs of AA batteries being in any way adequate. I tried them in fours, twos and singly as modules that I made up, and you can read about that here
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[prState]

Something I've been wondering about. Is there a reason one wouldn't want to use a number of battery holders (like this for instance) to make a pack?

I have a D cell holder similar to that. The little springs seem to have held up with the alkalines in it for two years now. I wouldn't use the connecting wires that come with it, because the gauge is too small, but it would be fairly easy to add 16 or 14ga directly to the clips and connect several together.

 

[flecc]

I've recommended against these in the past prState, since I've had experience of bad contact with them in the AA size with low current uses. The wire coils aren't very well made and the contact is sometimes just point contact only, not really good enough for high current drains in the order of 5 to 15 amps in an e-bike. They may work, but instinct says they aren't really up to it.
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[prState]

Okay, thanks. I have another non-solder idea that involves battery weight and using spring pressure at the top of a custom case. Perhaps the effort I put in on thinking of shortcuts, I should just work on soldering technique

 

[Miles]

I think the solderless method using silver paste might be worth investigating....
MEC :: Products

 

[prState]

That looks interesting, but I couldn't figure out exactly what was supposed to be in that photo. Is there a clear tube there?