EEVblog Electronics Community Forum
EEVblog => EEVblog Specific => Topic started by: Eviltech on March 29, 2013, 08:07:00 pm
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Hi guys! I have a motorcycle and i got sick of replacing lead-acid batteries damaged by mechanical shocks. I was thinking of replacing the original battery with a smaller more shock-proof battery to save myself the trouble i have to go trough every 2 months. I concidered the NiMH baterries and the LiIon batteries, but i think they are not a good idea for this pourpose. Entirely by chance i saw the LiFePO4 batteries and checked their charachteristics. As i can see they are pretty good for the job having in mind that i ca use only 4 of them to replicate the 12V Lead Acid battery. People also say that i can skip on the protection circuit when i use it on the bike. What do you think? Shold i use them? :-//
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I don't think they would be any more mechanically robust. It seems like you have some problem with how you're mounting it.
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I'd love to know what you're doing on your bike that's wrecking batteries... please tell me it's an off-road machine and that you're a trials rider!
I've not heard of mechanical failure being a major problem with lead-acid batteries, though I'm prepared to believe it could happen. If it's not a dumb question, how do you know the problem is mechanical and not some fault with the charging circuit that's ruining batteries?
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As far as i know, li-ion batteries are not more safer than lead-acid...not more shock-proof either(unless you're comparing to those old-style liquid type, they are not even really shake-proof)...
Anyway, lipo pack is actually pretty safe when mounted appropriately, given enough "padding" while keeping them in a good venting environment(if high temperature is expected).. They are massively being used in the RC field(remote control cars/airplane models)..you know lipo pack is safe enough as you know how that kind of environment is ;)
PS: actually, the working voltage of LiPo is 3.7~4.2v, LiFe is 3.3~3.6v, LiLo is 3.6~4.1v..
If li-ion is preferred, than I'd go for some >15A discharge lipo pack.. with 3 in series you get a perfect 11.1~12.6v working voltage :) There are many pre-packed lipo packs that come with balance port soldered already, so making the maintenance much easier :)
added:
Protection circuit is a Must-have for li-ion batteries......unless doing so intentionally for a specific purpose(like what Dave have done to those poor multimeters :-DD)..
For using in in a bike, at least you'd need over-discharge, short-circuit, and over-heat protection/indicator. There are many cheap little voltage indicators(light the LEDs according to the the input voltage) at ebay, just get one and hand solder it to the main output(run an extended wire to put the display on the front so you can watch the remaining capacity on the run)..it would be a nice add-in feature ;D
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And be carefull where/how to mount it... I'm sure you don't want to sit right atop of 15Ah 3-cell LiIon battery when it blows.
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How about using 6 ultracaps in series, as a replacement. All you need is a set of balancing regulators and a shunt regulator for the charging.
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Hi guys! I have a motorcycle and i got sick of replacing lead-acid batteries damaged by mechanical shocks
What the heck are you doing to them?? What size M/Cycle? Trail bike? Have you checked the Alternator?
Entirely by chance i saw the LiFePO4 batteries ..
What brand and capacity are you looking at? Thundersky?
.... i can use only 4 of them to replicate the 12V Lead Acid battery. People also say that i can skip on the protection circuit
when i use it on the bike
???? I'd vet your friends better :-) NEVER skip protection circuits on any Lithiums.
What do you think? Should i use them?
Very risky, unless you know how t handle them. EG They can NOT take any level of over-charge !! Period !! Those little crappy
over-charge circuits you see may be ok for appliances, but NOT for a M/Cycle with a hefty Alternator, which has questionable regulation.
You can NOT ignore cell balancing, especially on a M/Cycle. Then you have to guarantee they don't under-voltage.
You can reduce life expectancy from 500-1000+ cycles >> 5-10 in ONE bad charge cycle. I work with these things a LOT !
I'd search for EV M/Cycle clubs / Forums and find out what members are doing, and ask there.
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If you're smashing up lead acid batteries, any lithium battery won't stand a chance, your bike will go up in flames in no time. You need to figure out a better mounting instead of just constantly replacing the batteries.
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If you skip the protection circuit, you're basically installing a bomb onto your bike.
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I've nothing against safety, but do please take a minute to read up on LiFePO4 specifically - I gather it's much safer than other chemistries.
Here's one manufacturer's information, quite an eye opener if you're of the opinion that all lithium batteries are fires waiting to happen:
http://www.globelws.com/battery.html (http://www.globelws.com/battery.html)
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Ah, thanks for bringing up the chart.
Honestly i've never got a chance to play with this new type of li battery, so just learned something new now...
after digging around like wiki and some battery manufacturer sites for specs and availability, apart from the lower energy density(only near half of traditional lipo), the LiFePo4 type is indeed quite fabulous regarding safety..
While searching, found the following informative link(looks like this type of battery has been around for quite some time yet I really didn't know something about it.. :-[):
http://www.candlepowerforums.com/vb/showthread.php?312871-LiFePO4-abuse-tolerance-amp-overall-safety (http://www.candlepowerforums.com/vb/showthread.php?312871-LiFePO4-abuse-tolerance-amp-overall-safety)
"If you charge a "conventional" lithium-ion cell to the same storage energy as a cell with LiFePO4, you will find that it has similar safety characteristics."
PS: also found some interesting videos at youtube for some exclusive lithium battery testings..there are a series of videos for different types of batteries, all posted by the same guy...so pardon me just quote his channel link(just click the "load 10 more videos" a few times then all the battery testing videos will be there):
https://www.youtube.com/user/liveforphysics532 (https://www.youtube.com/user/liveforphysics532)
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Hi guys! I have a motorcycle and i got sick of replacing lead-acid batteries damaged by mechanical shocks. ...
How on earth did you damage it?
In 20 years in the business, I never saw a well serviced car/bike battery being damaged by a shock.
Not on the road/circuit, 4x4, jeeps, army, cross.
The only reason people ere change their battery for a more expensive one, is weight.
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Shorai batteries are Li-Fe batteries specifically designed for motorcycle lead-acid replacement.
http://www.shoraipower.com/ (http://www.shoraipower.com/)
But I advise a google search for Shorai fire, and make your own choice, there have been a couple of instances of them catching alight - granted, it's a very small percentage, but it's a risk you might have to evaluate.
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In 20 years in the business, I never saw a well serviced car/bike battery being damaged by a shock.
Not on the road/circuit, 4x4, jeeps, army, cross.
Same here, my off road machines are horribly abused. If I keep them properly charged during storage they last for years, and for many this includes heavy loads such as winches.
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Normally you need a good shock frame, rubber strip on the bottom, sides and such where the frame rubs. A strap on top holds it in and almost nothing will damage it without putting the rider in hospital. Even on a boat where the battery went swimming in salt water regularly, they survive for years. Only killer is running it and then parking for 6 months without charging, and not having the breather tube on, and letting the cells go dry.