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Anything I need to know? I'm after a tiny battery pack to go under the stem for my lights. I can handle soldering, assembly and such, and I have a smart charger I'd use.
I see lots of cells for cheap on ebay.
1) Are they likely to be as dodgy as laptop batteries? Is there somewhere I can go to get reputable cells?
2) Do I need to ensure they are matched in some way?
3) Do I want Li-Po?
Buy cells with tabs, soldering to a Li-ion cell is quite tricky, you really need an capacitive discharge welder as you don't want to heat up the end of a Li-ion cell with a 100W iron long enough to get the solder to melt, as the cell will get very warm in the process...
Cheap ones on eBay are unlikely to have (working) protection circuits on them - which can potentially make them a little explodey if things go wrong (short circuit, thermal runaway) or just damage the batteries (over discharge).
Lots of good YouTube videos on protection circuits and the like.
There are tons of flat cells with wires already on. At those prices I could just take a punt I suppose.
I think Li-ion/Lipo is something I'd really not want to go near on a diy basis.
You can get something from MtbBatteries for not much that will have appropriate protection, the right ends on it etc. and not blow your house up making it.
You can buy the protection circuits for a few $..
I've soldered directly to flat-top laptop cells. It's a fairly ****ing awful idea to be fair but it was fine, and I'd prepared for it not being fine (I did some Science first and intentionally blew up some cells first so I knew what to expect if it went wrong, I'm very responsible)
I'd buy a pack personally, for this job, once you've dealt with durable strain-relieved cabling, waterproofing etc it's a fair old faff. Getting wiring that'll stand up to all this movement isn't so easy- Hope can't do it frinstance.
I guess another option might be an RC pack, if your charger will do that? You can get hard case packs in many sizes.
Tiny size is the key. I want 2000mAh or similar so I can strap it under my stem.
Did you see the product jimdubleyou posted on [url= http://singletrackmag.com/forum/topic/iphone-5-extra-battery-for-on-bike-charging#post-7750232 ]this thread[/url]:
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Might suit your needs without needing to go custom.
Wouldn't you be better off with a 2 cell 18650 case and some good protected cells? Can carry spares easy then just in case 2000mAh isn't quite enough 🙂
seriously not work fannying about for that requirement . plenty off the shelf items will do it.
building a big unit for a ne electric bike to fit an odd shape yes....
2000mah to fit under stem .... exists already - cheaply.
The point of having a small battery is to save weight and space when travelling (not riding) - carrying spares defeats that object!
Graham - nice product, might well use it for GPS duties, but not enough voltage for lights.
Having said that, it would work with my commuter light which is actually good for riding and compact but has a small battery...
what about just buying a decent brand mobile phone charger battery? I guess the only downside is you will have to press the button to activate it.
Or some kind of battery case or something made from nice waterproof DIY torch parts.
i have a 9000mah battery the size thats about 6cm by 8cm by 2cm and lives under my stem.
powers my etrex 30x all day and charges my phone / edge 500 when required.
i dont think ive emptied it yet even over a weeks touring - but i do charge from a cycle2charge/dyno hub during the day. i could get away with smaller but the 9000mah is what i have.
also not sure airport security would take a nice view on homebrew battery packs when traveling.
Sorry missed that it was for lights.
The 2-cell pack from Gloworm is pretty small, 3400mAh at 7.4v. 120 grams and waterproof. But it is £60 and you'd need a charger.
http://www.glowormlites.co.nz/product/gloworm-2-cell-high-capacity-3400mah-li-ion-battery/
I just bouht one of these from ebay:
http://www.ebay.co.uk/itm/221371634301?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
it hasn't arrived yet & delivery is fairly long, but when it turns up I'll be hecking it over & giving it a run time test.
Th bloke/company claim they use proper cells; they cell the same pack but with different batteries described for different prices.
They do smaller capacity ones:
and you can specify the connector type etc. if the picture doesn't show the one that you need.
I looked at making my own, but figured out I'd probably end up down A&E and with load of dead batteries sat in the garage. Buying batteries from a reputable UK supplier (like torchy the battery boy, o ebay) would have cost me more just for the batteries than the pack that I bought; I figured it was worth a punt.
If you're in no rush, I can update once it's here & I've tried it; assuming it fits my old Spokeshirts light, that is!!
Those look perfect, stumpy.. assuming they are decent. At those prices it's worth a gamble.
The wrapping of the batteries/lead doesn't look terribly weatherproof, but I figure I can sort that with some silicon sealant.
If I was night-riding a lot still, then I'd be tempted to go for a well known UK seller. But, my last night ride was, erm......a long time ago!
The battery for my Spokeshirts light has had it after 5.5 years or so. It used to do 3hrs on full power, but now struggles to do 2hrs on low power, so I figured a replacement was due. The light isn't exactly cutting edge but is fine for a helmet light & the battery I've ordered has got almost 30% more capacity than the original, so should be good for 4hrs or so, on max.
Well, it turned up today, molgrips....
I plugged it into the light and it worked fine with a nice,solid connector.
Currently on charge (in a biscuit tin).
It arrived at the front end of the estimate.
I think it will need some weatherproofing, as there is quite a gap around the heatshrink and the cord.
I'll take some pics at some point and post them up.
Ta. Do you have any way of measuring capacity?
When you say measuring capacity...erm....how would I do that?
It's taking a while to charge. Been on for almost 3 hours and not done.
I'll be doing a run time test at some point this week.
The original battery was 4400mAh and gave 3hrs on full supposedly, which although I never ran it out i could believe based on what the battery indicator was showing for a given run time.
This battery is 5600mAh so should do around 3hrs 50, so we'll see...
If you had the means, you'd know 🙂
I've got a Lupine charger that'll fully discharge then recharge a battery.. it tells you how much it's extracted then how much it's put back.
That'll be why Lupine stuff is so expensive! All that useful, real world functionality.... 😆
If you had the means, you'd know
Before Mountain Mayhem I used to fully charge all my Lupine batteries and then time their discharge running a light at full beam (with the light head cable tied to a fan, so it wouldn't over heat), and then marked it on the pack, so I'd know how long I had with each pack.
I've got a Lupine charger that'll fully discharge then recharge a battery.. it tells you how much it's extracted then how much it's put back.
The put back bit only works well on a good battery, once you have a duff cell it can put in say 5Ah but you only get back 2Ah before the voltage collapses and the protection circuit cuts out.
Out of interest; have you considered RC Hobby grade lipo cells? LOADS of variation available from (for example) hobbyking, for not a lot of money. No 'battery protection' included, but you could add a low voltage alarm pretty easily. Just a thought.