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Old 11-10-07, 12:08 PM   #1
BikeToWork
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11.1 V Li-Ion vs 13.2 V NiMh

I have an older NiteRider Blowtorch 10W HID light and the battery is in the process of dying now after approximately 300 charge/discharge cycles. I'm looking at battery replacement options and am agonizing over whether to go with the BatterySpace 11.1 V lithium-ion battery and charger

http://www.batteryspace.com/index.as...OD&ProdID=2814

or the standard 13.2 V Niterider NiMh battery

The tech I spoke with at Batteryspace recommends the 11.1 volt water bottle battery. He explained that the higher voltage li-ion batteries run a risk of burning out the ballast on the 10W HID light. That seems strange since they offer other li-ion batteries with regulator switches that can be set to 12 or 13.2 volts, the standard voltage for this light. Does anyone on this forum have experience with 11.1 Li-ion battery on NiteRider Blowtorch? Is it dimmer than with 13.2 V NiMh? How is the runtime? How many charge/recharge cycles is the battery good for?

The weight savings is minimal (6 oz) and the Li-ion battery will end up costing about $50 more because I would need to buy the charger and change connectors. I already have the microbrote niterider charger, which seems to be a vast improvement over their older models. I really like li-ion batteries and want to get away from the (ripoff) proprietary hardware where I can. Also, 300 charges from the last battery seems rather unimpressive. Any advice on this would be much appreciated.
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Old 11-11-07, 09:14 AM   #2
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The problem with the higher voltage (4s) lithium packs is that their peak voltage is roughly 16.8 volts compared to 12.6 for the lower voltage (3s) packs. After a short use those values go down to 14.8 and 11.1 but its that brief time at 16.8 that's a problem.

I've used a Li-ion 3s battery with my HID which was originally purchased with a NiMH battery. It might be slightly dimmer with the lower voltage, but I haven't been able to notice. I'm going to try building up a LiFEPO4 4s Li-ion battery which due to the lower voltages (3.6 vs 4.2 peak) should work with the HID as it gives voltages very similar to the NiMH battery.

Keep in mind that any battery life indicator will be slightly confused by the switch in battery chemistry.

Run times should increase along with any increase in capacity as you'd expect. Li-ion will weigh probably about 1/2 as much as NiMH for equal capacity.

Lastly I wouldn't expect to get more cycle life out of the normal (4.2v) Li-ion. If anything, probably less.

-Joel
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Old 11-11-07, 10:36 PM   #3
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Go for a 12v LiFePO4 pack from batteryspace. Peak voltage: 14.4, nominal voltage 13v.

The best part of LiFeP04 is the following:

1. Unaffected by temperature.
2. Will not ignite like Lithium Polymer
3. Rated to 2000+ cycles
4. Similar power density to Lithium Polymer packs

Only downside is you need the matching charger.
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Old 11-12-07, 11:16 AM   #4
BikeToWork
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K6-III, thanks for the tip. I am a displaced Minnesotan myself and bike all winter here in the DC area, which sometimes means temps in the teens. I was wondering about the cold issue because I also go camping in subzero conditions and unless I keep my camera's Li-ion battery warm, it will not work and is only good for a couple of shots once I take it out of my warm pocket and put it in the frigid camera. Are the "universal connectors" from batteryspace any good? I currently have the pre 2002 NiteRider pop plug connectors, not sure if they are compatible with the "universal" ones.
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Old 11-12-07, 12:57 PM   #5
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I went to the batterypace website and just realized that the LiFePo4 batteries have considerably less amp hours than the 11.1 v 9.6 ah water bottle battery I was thinking of. That would mean less runtime than the nimh battery, which is kind of a showstopper...Does anyone have experience with Li-ion bicycle light batteries in cold weather?
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Old 11-12-07, 02:21 PM   #6
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The main advantage of LiFePO4 over NiMH as far as bike lights go is that they require fewer cells for the same voltage. So using "standard" LiFePO4 over "standard" NiMH cells you can get a smaller and lighter battery (with less run time). Also, until you can buy low self discharge (LSD) NiMH packs, LiFePO4 (and other Li-ions), won't lose their charge so fast by just sitting around.

LiFePO4's advantage over normal LI-ion is that they're less likely to blow up.

Everything's a tradeoff.

-Joel
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Old 11-12-07, 02:52 PM   #7
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What about the cold weather factor? Is a standard 11.1 v 9.6 ah Li-ion battery going to be like my camera battery and crap out when subjected to sub freezing temperatures?
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Old 11-12-07, 05:00 PM   #8
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A standard LiPo will be affected by cold weather or warm weather. The LiFePO4 will offer give the same performance regardless of temperature.

The 9.6Ah pack you're looking at weighs in at 22oz and costs $180.

The 12v LiFePO4 packs cost $50 for a 2.7Ah pack that weighs 5.2 oz. Thus, with 3 packs in parallel, you're looking at 8.1Ah at 15.6oz, all for less money.

Given your investment in a large battery, you may want to get a nicer charger as well, as compared to the charger on BatterySpace. (The $30 charger limits you to 1.5A charge, would take 5 hours to charge your 8Ah pack) This charger lets you charge at 4A, so only 2 hour charge: http://www.fmadirect.com/products.htm?cat=45&nid=4
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Old 11-13-07, 11:57 AM   #9
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Actually, the battery I ordered is $156, which includes the charger and comes in a water bottle. The tech person at batteryspace.com says these cells are rated down to -20 C (-5 F), so that should be fine for DC. The coldest I ever ride in here is around 10 degrees F. Your points about the LiPo are all valid but I figure this battery will give me monster runtime when compared to the standard 4.0 ah NiMH battery that came with the light and should (hopefully) be a major upgrade over the NiteRider battery.

btw: While my regular light is in disrepair, I picked up a Viewpoint "Flare 5" led light, which runs off of 4 AAA batteries. I am amazed by how many lumens I got for $12! The thing is almost bright enough to see where I'm going and definitely bright enough to be seen by cars.
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