Can replace Lthium with Nimh external battery pack?

Okay. I see most new external battery pack lights are using lithium ion battery packs. I have a number of perfectly good Nimh batteries. If the voltage is the same is there any reason I can't use those NiMh battery packs with a light that came with a lithium ion battery pack?

Cheers

On Mon, 21 Sep 2015 20:43:31 -0700 (PDT), Sir Ridesalot
wrote:

Okay. I see most new external battery pack lights are using
lithium ion battery packs. I have a number of perfectly good
Nimh batteries. If the voltage is the same is there any reason
I can't use those NiMh battery packs with a light that came
with a lithium ion battery pack?

Lithium Ion is a nominal 3.7 VDC per cell. NiMH is 1.35 VDC.
If the total voltage of the LiIon battery pack is something closely
divisible by 1.35 VDC, it might work. However, then you'll have to
deal with the battery charger circuitry, which is very different
between different battery chemistries. I don't think it's worth the
risk of frying the LED's.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tuesday, September 22, 2015 at 1:23:18 AM UTC-4, Jeff Liebermann wrote:
On Mon, 21 Sep 2015 20:43:31 -0700 (PDT), Sir Ridesalot
wrote:

Okay. I see most new external battery pack lights are using
lithium ion battery packs. I have a number of perfectly good
Nimh batteries. If the voltage is the same is there any reason
I can't use those NiMh battery packs with a light that came
with a lithium ion battery pack?

Lithium Ion is a nominal 3.7 VDC per cell. NiMH is 1.35 VDC.
If the total voltage of the LiIon battery pack is something closely
divisible by 1.35 VDC, it might work. However, then you'll have to
deal with the battery charger circuitry, which is very different
between different battery chemistries. I don't think it's worth the
risk of frying the LED's.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Thanks Jeff.

I have the NiMh charger too. If I did get the Lion powered light it'd come with Lion battery charger. thus there's no concern about using the wrong charger on the battery pack.

Cheers

On Mon, 21 Sep 2015 20:43:31 -0700 (PDT), Sir Ridesalot
wrote:

Okay. I see most new external battery pack lights are using lithium ion battery packs. I have a number of perfectly good Nimh batteries. If the voltage is the same is there any reason I can't use those NiMh battery packs with a light that came with a lithium ion battery pack?

Cheers

LED lights have a constant current regulator. As long as the input
voltage is close it will work OK. But don't mix chargers.

On Tuesday, September 22, 2015 at 2:48:49 AM UTC-4, somebody wrote:
On Mon, 21 Sep 2015 20:43:31 -0700 (PDT), Sir Ridesalot
wrote:

Okay. I see most new external battery pack lights are using lithium ion battery packs. I have a number of perfectly good Nimh batteries. If the voltage is the same is there any reason I can't use those NiMh battery packs with a light that came with a lithium ion battery pack?

Cheers

LED lights have a constant current regulator. As long as the input
voltage is close it will work OK. But don't mix chargers.

I don't know much about Lions and Nimh but from building radio-controlled boats i do know not to charge one with the other type of charger.

The thing is my Cygolite at the high setting of 250 lumens is pretty decent and I have extra battery packs for it. the new Cygolites i referenced are all Lion battery packs which I knew meant my existing batteries couldn't be charged with the new Lion charger but i was hoping to be able to use those Nimh battery packs as backups on my really long night rides that i frequently take.

I'm thinking that perhaps the 800 lumens Cygolite might meet my needs and it's about $150.00 less than the Cygolite 1300 or 1700 lumens ones.

Cheers

On Mon, 21 Sep 2015 23:24:25 -0700 (PDT), Sir Ridesalot
wrote:

On Tuesday, September 22, 2015 at 1:23:18 AM UTC-4, Jeff Liebermann wrote:
On Mon, 21 Sep 2015 20:43:31 -0700 (PDT), Sir Ridesalot
wrote:

Okay. I see most new external battery pack lights are using
lithium ion battery packs. I have a number of perfectly good
Nimh batteries. If the voltage is the same is there any reason
I can't use those NiMh battery packs with a light that came
with a lithium ion battery pack?

Lithium Ion is a nominal 3.7 VDC per cell. NiMH is 1.35 VDC.
If the total voltage of the LiIon battery pack is something closely
divisible by 1.35 VDC, it might work. However, then you'll have to
deal with the battery charger circuitry, which is very different
between different battery chemistries. I don't think it's worth the
risk of frying the LED's.

I have the NiMh charger too. If I did get the Lion powered
light it'd come with Lion battery charger. thus there's no
concern about using the wrong charger on the battery pack.

What nominal voltage is the LiIon pack and what voltage does the light
expect? These should be the same, but with LiIon packs being "rated"
at anything between 3.6 to 4.2 VDC per cell, there may be some
variation. The light may also have a range of acceptable voltages as
controlled by a series current regulator. I would put the light on a
bench power supply and see what it can do over a range of applied
voltages. Then, the idea is to adjust the number of cells in the NiMH
pack, possibly adding a diode or two to make the voltages roughly
equal, to produce roughly the same voltage.

NiMH is a tolerable replacement for LiIon but only for fairly low
currents. If your light is in the mega-lumen class of photon torpedo
offensive bicycle weaponry, the NiMH battery pack may not be able to
deliver the current. So, I need an estimated current consumption
figure for the light in order to check if this is a problem.

Incidentally, I tend to go the other direction. Some of my older
NiCd/NiMH Makita power tools now have an internal LiIon batteries.
Running on LiIon power, they last longer, charge faster, and are MUCH
lighter. I'm waiting for some of my NiMH battery packs to die so I
can fill them with LiIon cells. I wouldn't dream of going the other
direction with these tools.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Mon, 21 Sep 2015 23:24:25 -0700 (PDT), Sir Ridesalot
wrote:

I have the NiMh charger too. If I did get the Lion powered
light it'd come with Lion battery charger. thus there's
no concern about using the wrong charger on the battery pack.

I guess this is for one of the Cygolite LiIon lights that you were
considering purchasing. (Sorry, I missed the previous thread on the
topic). Cygolite seems to standardize on a 7.6v DC LiIon battery pack
for the lights. No NiMH packs available.
http://www.shop.cygolite.com/category.sc?categoryId=24

7.6 VDC would be two 3.8 VDC LiIon cells. To produce that using NiMH
cells would requi
7.6 / 1.35 = 5.6 cells
which isn't going to work. The best I can do is 6 cells, for:
1.35 * 6 = 8.1 VDC
which requires a voltage drop of:
8.1 - 7.6 = 0.5 VDC
which can easily be accomplished with a single power diode in series
with the battery pack. I don't like the power loss in the diode, but
it should work. The diode should be built into a plug and jack power
adapter installed between the NiMH pack and the light. That way, you
can use the NiMH charger, without the diode getting in the way. That
will also allow you to use a LiIon pack, but simply removing the diode
adapter.

Permit me to offer an alternative approach. Instead of reverting to
NiMH cells, just find a cheaper LiIon battery pack. I suggest you
look at the various radio control batteries. What you want are the
biggest LiIon batteries possible in a 2S pack (possibly with the
balance charger connector). 2S packs sorted by price:
http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?cwhl=XX&idCategor y=86&v=&sortlist=P&LiPoConfig=2&CatSortOrder=desc
I can't calculate how many milliamp-hrs will be needed without knowing
which light you plan to use. After that, it's packaging (stuff it in
a water bottle) and adapters for the power connector.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tuesday, September 22, 2015 at 12:56:34 PM UTC-4, Jeff Liebermann wrote:
On Mon, 21 Sep 2015 23:24:25 -0700 (PDT), Sir Ridesalot
wrote:

I have the NiMh charger too. If I did get the Lion powered
light it'd come with Lion battery charger. thus there's
no concern about using the wrong charger on the battery pack.

I guess this is for one of the Cygolite LiIon lights that you were
considering purchasing. (Sorry, I missed the previous thread on the
topic). Cygolite seems to standardize on a 7.6v DC LiIon battery pack
for the lights. No NiMH packs available.
http://www.shop.cygolite.com/category.sc?categoryId=24

7.6 VDC would be two 3.8 VDC LiIon cells. To produce that using NiMH
cells would requi
7.6 / 1.35 = 5.6 cells
which isn't going to work. The best I can do is 6 cells, for:
1.35 * 6 = 8.1 VDC
which requires a voltage drop of:
8.1 - 7.6 = 0.5 VDC
which can easily be accomplished with a single power diode in series
with the battery pack. I don't like the power loss in the diode, but
it should work. The diode should be built into a plug and jack power
adapter installed between the NiMH pack and the light. That way, you
can use the NiMH charger, without the diode getting in the way. That
will also allow you to use a LiIon pack, but simply removing the diode
adapter.

Permit me to offer an alternative approach. Instead of reverting to
NiMH cells, just find a cheaper LiIon battery pack. I suggest you
look at the various radio control batteries. What you want are the
biggest LiIon batteries possible in a 2S pack (possibly with the
balance charger connector). 2S packs sorted by price:
http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?cwhl=XX&idCategor y=86&v=&sortlist=P&LiPoConfig=2&CatSortOrder=desc
I can't calculate how many milliamp-hrs will be needed without knowing
which light you plan to use. After that, it's packaging (stuff it in
a water bottle) and adapters for the power connector.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Thanks Jeff. I guess I'll stick with Lion packs for whatever Cygolite i get. BTW, all my NiMh batteries for my RC boats are 7.2 volts according to the battery info on the battery.

cheers

On Tue, 22 Sep 2015 11:21:42 -0700 (PDT), Sir Ridesalot
wrote:

BTW, all my NiMh batteries for my RC boats are 7.2 volts
according to the battery info on the battery.

That would be 1.2 V per cell (for a 6 cell pack) instead of my 1.35 V
per cell. Googling around, that seems to be todays nominal NiMH
voltage. Looking at my discharge curve:
http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg
it could be 1.35 V if I use the unloaded voltage immediately after
charging, or down to 1.00 V if I use the voltage of an almost depleted
battery. At 50% of full charge, it's about 1.17 V, which is close
enough to call it 1.2 V. I guess I'll have to change my calculations
to 1.2 V to accommodate todays cells.

I think you made the right decision by NOT trying to change battery
chemistry for a rather expensive light. I would worry more about
warranty issues than performance or cost. If the manufacturer
suspected that you've been juggling battery packs and using
non-approved chemistries, they might void the warranty. However,
since you haven't bought the light yet, it would be interesting if you
asked the manufacturer what they think of substituting battery packs.
They may already have tried it.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tuesday, September 22, 2015 at 11:21:48 AM UTC-7, Sir Ridesalot wrote:
On Tuesday, September 22, 2015 at 12:56:34 PM UTC-4, Jeff Liebermann wrote:
On Mon, 21 Sep 2015 23:24:25 -0700 (PDT), Sir Ridesalot
wrote:

I have the NiMh charger too. If I did get the Lion powered
light it'd come with Lion battery charger. thus there's
no concern about using the wrong charger on the battery pack.

I guess this is for one of the Cygolite LiIon lights that you were
considering purchasing. (Sorry, I missed the previous thread on the
topic). Cygolite seems to standardize on a 7.6v DC LiIon battery pack
for the lights. No NiMH packs available.
http://www.shop.cygolite.com/category.sc?categoryId=24

7.6 VDC would be two 3.8 VDC LiIon cells. To produce that using NiMH
cells would requi
7.6 / 1.35 = 5.6 cells
which isn't going to work. The best I can do is 6 cells, for:
1.35 * 6 = 8.1 VDC
which requires a voltage drop of:
8.1 - 7.6 = 0.5 VDC
which can easily be accomplished with a single power diode in series
with the battery pack. I don't like the power loss in the diode, but
it should work. The diode should be built into a plug and jack power
adapter installed between the NiMH pack and the light. That way, you
can use the NiMH charger, without the diode getting in the way. That
will also allow you to use a LiIon pack, but simply removing the diode
adapter.

Permit me to offer an alternative approach. Instead of reverting to
NiMH cells, just find a cheaper LiIon battery pack. I suggest you
look at the various radio control batteries. What you want are the
biggest LiIon batteries possible in a 2S pack (possibly with the
balance charger connector). 2S packs sorted by price:
http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?cwhl=XX&idCategor y=86&v=&sortlist=P&LiPoConfig=2&CatSortOrder=desc
I can't calculate how many milliamp-hrs will be needed without knowing
which light you plan to use. After that, it's packaging (stuff it in
a water bottle) and adapters for the power connector.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Thanks Jeff. I guess I'll stick with Lion packs for whatever Cygolite i get. BTW, all my NiMh batteries for my RC boats are 7.2 volts according to the battery info on the battery.

cheers

LED's require about 1.5V per light. Since the Lion puts out over 3 volts the usual circuit is to use a low voltage controller driving a constant current source and powering the LED's two in a serial configuration.

The constant current source probably has a .6 volt or nearly that drop so in order to power the blinky you'll need a power source of about 3.6 volts or a little higher.

So you could drive it with three NiMH batteries in series and any number of those set ups in parallel to supply the expected lifespan before requiring a charge.

You can recharge them via a normal NiMH recharger by taking the cells out of the battery box and inserting them individually into the charger. There are high speed smart chargers all over the Internet including Amazon and Ebay.

Lights are not rocket science.