LiPo or not to LiPo. That is the question.

skyungjae

skyungjae

10 kW
Joined
Nov 30, 2012
Messages
832
Location
Southern California
Hi Everyone,

As the title states, I'm currently thinking about putting together a new pack for my e-bike. Back in January 2013, I've put together my 2005 Kona Stinky with a GNG motor (link to my build thread in the signature).

At the time I decided to get five 3s2p LiFePO4 Zippy packs to make a 50V 8.4Ah pack.

The pack worked fantastic at the stock GNG power levels of 1000W. Around mid-May 2013, I modified the controller to put out 35A (huge jump from the previous 22A). I still rode pretty conservatively and the battery pack ran fine until I started getting curious how long I could play in the 30A+ arena. So about last month (July), I started noticing the voltage sagging much more during use as well as the batteries having trouble squeezing into the box my friend had made for me.

Anyhow, these batteries are supposedly rated to 30C, and I was using them at around 4C. These Hobby King Zippy LiFe batteries seem to have an actual discharge rate similar to most LiFe cells around 2~3C. It's well known that HK LiFe batteries are highly overrated when it comes to their C rating. Some people that I have discussed this with feel that charging has led to the pre-mature puffing / battery degradation. However, my charge practices, especially over the past 5 months had remained the same. I've always checked the voltage of the individual cells per pack before and after charging and balance charge at around 1/2C (parallel charging five packs at 20A). The batteries have NEVER even gotten warm during charging. Though the pack is puffed (every cell), I can still get 6Ah out of it if I use it conservatively. At about 600 miles and less than 40 charge cycles, I was rather upset with this pack.

Skip to here if you don't want to read the background.

So, lately I've been thinking about putting together a new battery. I was just curious what y'all thought about using LiPos for commuting. I take the train and store my bike inside my office which is in a Federal building. Thoughts of the potential fire hazard made me think about getting a pre-made plug and play LiFePO4 pack. What's making me think about going with LiPo is the power to weight ratio as well as cell longevity. I wear my batteries in a backpack and run an umbilical out of it to the bike, so a 25lbs 15Ah pack doesn't sound like fun to carry around. With the 2C rating I'd probably kill it in a few months of fun riding on the hills behind my house. All the vendors I have spoken to regarding putting together a battery keep telling me a 30-40Ah pack would best suit my power needs in terms of extended charge cycle longevity, but I'm not going to wear 30lbs+ of battery on my back and carry whatever else I need to.

Does anyone else use public transportation and store their bikes w/ battery in their buildings with LiPo batteries? I wouldn't be charging at work, nor would I be leaving the bike w/ batteries there for any extended period of time. The likelihood of the batteries spontaneously combusting while sitting in my office or on the train are close to none. However, the stigma of LiPo fires has me concerned.

What do y'all think? I was thinking about getting four Turnigy nanotech 6S 8000mAh batteries to put together a 44.4V 16Ah pack as a suitable replacement for my Zippy LiFe pack. I do have 6S low voltage cell alarms, but I probably wouldn't need them for commuting since I only use about 2Ah (w/ pedaling) a day going to and from. My Cycle Analyst LVC is currently set at 44V, so it cuts power when the entire pack sags at 40.07V. I'd probably leave it there for the LiPo pack as well, but it shouldn't be an issue since I wouldn't be using up all the capacity in a work week.

These are the options I'm looking at right now:

1. Put together a Turnigy nanotech 44.4V 16Ah LiPo pack to replace my current LiFe pack.
2. De-tune my controller & get a 10-15Ah pre-made LiFe pack.
3. Keep my LiFe pack for commuting purposes, put together a Zippy Compact 44.4V 11.6Ah LiPo pack for fun time.
4. Open to suggestions.

Any thoughts and opinions would be helpful, but I'm hoping to hear from those who actually use LiPos that bring them on public transportation and store them indoors during the work day.
 
Definitely sounds to me like the bike wants a better C rate, but lipo in the office sounds like a good way to be jobless.

You could have nothing ever happen, but if it did..... I'm surprised you could get the old battery in the door.
 
dogman said:
Definitely sounds to me like the bike wants a better C rate, but lipo in the office sounds like a good way to be jobless.

You could have nothing ever happen, but if it did..... I'm surprised you could get the old battery in the door.
Click to expand...

Surprisingly, I've never had to show them to the Federal Protective Services. It's been a while since they've made employees run everything through the x-ray machines. :lol:
 
Skip to section koala bear if you don't want my inexperienced with lipo opinion.

Have you considered a 52v20ah a123 pack from em3ev?

If battery placement is the primary issue, it's time to consider a different bike where you can place the batteries on the bike, lots of people like batteries in the triangle on uprights. I think the idea of having lipo cells in a backpack is one of the worst I've heard in a while. You fall off the bike, the cells light on fire, you are disabled (knocked out or intensely injured) and on fire, game over. If you are going to say that the cells are in a case that is hard enough not to break when your fall and land on it, than if you should end up landing on them, you could be facing a serious back injury instead. Either way, ditch the backpack concept, it's a bad one. If you absolutely must wear this back pack concept, I suggest you get motocross armor that has back protection.

I might not be a credible source for opinion on battery chemistry safety with ones such as lipo, I've never used lipo before, nor have I ever been in your situation, but I wouldn't ever ever put myself in the situation you imagine. I don't ever plan to use lipo, the risk isn't worth it to me. The bump in energy density is paltry. There are a123 cells that you can use that aren't 20ah, they are cylinders, but you wouldn't be locked into that heavier 20lb pack. You could go with a lower voltage pack and probably still achieve what you need with different gearing. Maybe, I don't know.

koala bear

Putting your "Skip to here if you don't want to read the background." would make more sense at the beginning of the string of paragraphs. Instead of using the word here, use a unique phrase (like I did, koala bear), or just a bunch of **** in bold or whatever.
 
I've been using 15-20c rc lipo for 2.5 years now and wouldn't use anything else. I wouldn't waste my money on nanotech though unless you plan on drawing a few hundred amps from it.
 
Thanks for the input bowlofsalad.

I actually thought about the 50v20Ah pack from em3ev, and you're not the first to suggest a pack from them. It would undoubtedly end up in my pack though if I went that route though. :lol:

I currently use my CamelBak M.U.L.E. as a dedicated battery backpack and place that inside my larger tactical pack when I go places other than the trail.

I have put much thought regarding battery placement. Had I been building a bike specifically for commuting, I would've placed the batteries within the frame or a tail tray. However, I've grown up mountain biking, and I'm used to carrying all my gear in backpacks. I've also worn backpacks when riding motorcycles, and I've taken a spill on the highway wearing a very large tactical pack. Regardless of battery location, I'd likely be wearing a pack anyway. :wink:

I actually got the backpack idea from these fellows here:
http://www.ego-kits.com/battery/

A handful of other companies use battery backpacks as well (holybike.fr; corbinfiber; etc), but they're likely not using LiPo chemistry. The whole fire issue is why I went LiFe in the first place.

Since other freeride/DH riders on endless-sphere have done the LiPo backpack, it's become an option I'm willing to consider.

I may just get a 48v 10-15Ah LiFe battery (something that'll fit in my CamelBak) and reverse my controller mod bringing it back to 22A peak.



Thanks for the response wesnewell.

I had considered the nanotechs due to their advertised longer life cycle. Is there another comparable battery you'd recommend?

I know I can't have it all and there's no one-size fits all option here, so I thank you all for your input so far.
 
Interesting, I figured on metal detectors. Then the wiring makes them look, and you know what a large lipo pack looks like.

I see no problem with having some lipo laying around, it's recharging them, or whacking them, that starts a fire. I've had plugs undo, letting one pack over discharge. But that's easy to avoid with permanent parallel connections.

So if getting in the door is no problem, just carry enough so you don't have to charge at work, and you are good enough IMO. Maybe have some kind of fire resistant place to set them. Maybe a small metal file cabinet or large lipo bag.

Don't go carrying in a pack you know has physical damage, or has been overdischarged or overcharged. Or have something that could short, which would be nearly as big a problem with any chemistry of battery. Again, easy fix, don't have black and red touching each other and chafing the insulation.
 
I would absolutely not use LiPo if I worked and had to store the battery indoors. Since you work for the government it is highly probable that your Union Steward could not help you for a LiPo fire in the office. It's just not worth it.
otherDoc
 
Thanks guys. I'm starting to think that I should put together two separate packs. One for commuting purposes and one for fun time. :lol:
 
Likely the best approach. Continuing that theme, two bikes. One a sedate commuter that runs on weak lifepo4, the other a fun hot rod that needs lipo.
 
dogman said:
Likely the best approach. Continuing that theme, two bikes. One a sedate commuter that runs on weak lifepo4, the other a fun hot rod that needs lipo.
Click to expand...

That's going to be a while. My wife was pretty upset with the addition of another bike. She's an accountant and doesn't see the point in owning more than a single bike whereas I view different bikes much like the different clubs in a set of golf clubs. :lol: I'm going to try and sneak in a 3rd bike i'm building piece by piece by next Spring. :twisted:
 
Not the only wife to never understand the Bike + one equation. I'm pretty lucky, I have about 6 bikes, but the wife has 4 of her own.

I tend to think of bikes as falling into two different budgets. One is transportation budget, the others are entertainment or sports recreation budget. Transportation budget ebikes pay for themselves fast. The rest are indeed like boats, holes in the water you pour money into. Somehow, the bucks always flow into the fun bike hole.

But on the bright side, you didn't take up hot air ballooning, or any other flight hobby. That's really lighting up $100 bills every weekend.
 
I just made sure to make the wife's bike first before building my second bike. It also helps that she doesn't drive at all and has had more bikes than me.

She only complains about me working on bikes since we live in a small apartment. I'm fortunate that she's cool with owning a few bikes. I'm planning on culling the collection myself. I too want different bikes for different situations (like clubs), so my more general purpose bikes are being sold off and I will end up with 1 DH bike and 1 cargo bike.

BTW, her bike is LiPo powered, but with Method's protection kit and only I am allowed to charge it :mrgreen:
 
Thanks for all the input fellas. My current plan is to keep on using my HobbyKing LiFe set up until I can free up some funds to find an adequate replacement. I'll more than likely go with some sort of Li-Ion pre-made battery with plug n play charging for commuting purposes and build a LiPo pack for fun time further down the road.
 
speedmd said:
At the time I decided to get five 3s2p LiFePO4 Zippy packs to make a 50V 8.4Ah pack.
Click to expand...

Hi Skyungjae

Were you using a bms with the zippy lifepo4 bricks. I am looking at these for a customer now and they do look attractive compared to the little flash light cell packs.
Click to expand...

I was using them without a BMS. This battery set up was fantastic for 1000W.
 
speedmd said:
I though the lifepo4 needed a BMS or they would go south in a hurry. With BMS they have very good durability. Not sure what to do. Lipo too risky for the customer (and me also) but I do like the power it puts out. Amazing stuff. Hopefully something better/ safer comes out soon.
Click to expand...

If you treat these batteries like LiPos you should be fine. I have my Cycle Analyst LVC set up at 44V, so when it sags to about 41V (40.8 more specifically), it cuts the power. You can also use cell alarms, but it's not really necessary.

My only beef with these batteries is that the discharge rate is highly inflated. It's really more around 3C (like most LiFe) than the advertised 30C.
 
I used lipo on the train plenty of times, And also use them in a backpack, with 1.4kw of stored energy on my back, i never had an issue.
I always treat my lipos like a new born baby, very fragile, its like your dealing with small grenades

As bowlofsalad said, if you crashed, and the lipos blew, your most likely dead, but in saying this, if any lithium chemistry got punctured in the backpack, its gonna get real nast real quick

Iv also ridden with lipo bricks in my jacket pockets, 20s 8ah, that was freaky.


Iv never had a lipo fire, I always use chargers that cut off, i always monitor cell voltages,
Had plenty of controllers, motors, chargers blow, never the cells randomly blowing, but you do hear about it happing...
 
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