Home Made NiMH Packs?

Gurrie said:

I have noticed that during the course of my research into all things
"home made bike light" related, that many of you have also done diy
NiMH packs.

I have 5 Jaycar sub-C NiMH solder-tabbed cells soldered
together if anyone wants to buy them. The cells are
unused other than being soldered together. I might part
with the stuffed Nightstick they were going to replace
too (alu, useful for a batt. case).
Anyone want to make any offer?

hippy

Anything special involved in soldering batteries as opposed to "normal"
soldering?

Craig

"hippy" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Gurrie said:

I have noticed that during the course of my research into all things
"home made bike light" related, that many of you have also done diy
NiMH packs.

I have 5 Jaycar sub-C NiMH solder-tabbed cells soldered
together if anyone wants to buy them. The cells are
unused other than being soldered together. I might part
with the stuffed Nightstick they were going to replace
too (alu, useful for a batt. case).
Anyone want to make any offer?

hippy

I use 5 4500mAh C cells in plastic holders (one holds four, the other holds
two but is soldered to only use one cell). They are taped back to back & all
in a cut down drink bottle. Runs for over four hours with a 5W vistalite
globe, two hours with a 15W globe.

"Gurrie" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Guys,

I have noticed that during the course of my research into all things
"home made bike light" related, that many of you have also done diy
NiMH packs.

I found posts by Gags and Marty to name just two.

Anyone got an links, pics, tips & hints etc to share?

I was considering usign one of the plastic holders from jaycar etc, but
I'd rather use 4/3A size cells to get the longer run time. I may
consider making a second AA size pack using 2300mAH cells or similar.

Also the charger MW7168 that seems to be a popular choice. Is this a
smart charger? Does it run off mains or 12v? Can a power supply be
added (if 12V)?

Any help is apprecited.

Thx.

Craig

I use sets of 6 x 2700mAh subC cells from JayCar to power a cheap Cygolight
6v halogen system (2 x 6w globes). This is 'over-volted' (7.2v), so you get
a brighter, whiter light with a reduction in bulb life (but not too
signficant). In theory this gives about 19w hours of power, so 1.5 hrs when
running both bulbs; 3hrs for one bulb. I usually run one bulb only, and
keep the other as a spare.

Soldering together the batteries ensures that nothing is going to shake
loose. Tin each solder tab before ''sweating" the joint together. A
haemostat (the thing doctors use in surgery to clamp veins) makes an
excellent clamp when doing this. Wrap the whole pack in duct tape. To
carry the battery pack, rip the old SLA cell out of the bottle pack, line
the inside with a neoprene foam stubbie cooler. Throw away the dumb charger
too.

For about $50, you can get a reasonably smart charger from a model toy shop.
You want one with a temperature sensor to detect the charge peak. However,
I haven't found an inexpensive one that runs off a 240v AC power supply -
they all seem to use 12v DC, but any old car battery will do (steal the one
out of your wife's Barina). Don't use a 12v battery charger as the power
supply - it pulses. Also, make sure you get the polarity right when
connecting the power source to the charger (fries the charger in a
microsecond) - a cigarette lighter plug is therefore preferable to gator
clips.

This gratuitous advice is given without warranty.

Neil

"Gurrie" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Anything special involved in soldering batteries as opposed to "normal"
soldering?

Craig

When soldering batteries I will generally use heatsinks on the tabs close to
the batteries and I make sure that I do the joins pretty quickly so that not
too much heat is transferred to the batteries. I have also soldered some
4/3A batteries that didn't have tabs and I basically used a pretty hot iron
and tried to keep the actual contact time with the ends of the batteries
down to a minimum (I used wire between each battery).

Hope this helps,

Gags

Gurrie said:

Anything special involved in soldering batteries as opposed to "normal"
soldering?

Craig

Yes.
Make sure you give them a run with some fine sandpaper before you
solder. I assume you're using solder with flux in it. Some brands solder
easy and some are difficult. Give a bit of a sanding to be on the safe
side. I soldered mine in a flat row of five next to another row of five,
but I reckon five is difficult to get straight. There are other
arrangements that are probably better. 2-3-3-2 ?

Marty (oops.. I meant Oscar.. Shhh..)

Quoted message said:

"hippy" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Gurrie said:

I have noticed that during the course of my research into all things
"home made bike light" related, that many of you have also done diy
NiMH packs.

I have 5 Jaycar sub-C NiMH solder-tabbed cells soldered
together if anyone wants to buy them. The cells are
unused other than being soldered together. I might part
with the stuffed Nightstick they were going to replace
too (alu, useful for a batt. case).
Anyone want to make any offer?

hippy

Gurrie said:

Anyone got an links, pics, tips & hints etc to share?

hired-goons.net has a bunch of stuff, but I don't think there are any
photos of my current batteries.

Quoted message said:

I'd rather use 4/3A size cells to get the longer run time.

Definitely. You can get over 4Ah from 4/3A, which is lots of burn. I'm
running a pack of 10 cells. I made 5 sets of end-to-end cells, then
arrange these in a 3+2 stack. The whole thing ends up being a bit
longer than a glasses case, but a similar size, and velcros under the
top tube.

Quoted message said:

Also the charger MW7168 that seems to be a popular choice. Is
this a smart charger? Does it run off mains or 12v?

The MW7168 is a smart charger, and seems to do a decent job. I've been
using one for a few years now. It runs off 12V, but if you've got
access to old computers, AT power supplies are perfect. The yellow wire
is 12v, the red is 5V and the black is ground (normally) . Put an old
20W 12V halogen across the red and black wires to provide some load on
the 5V line - not all PSUs need that, but it's not hard. Also provides
a nice "the power's on" light.

Dave

Random Data said:

Gurrie said:

Anyone got an links, pics, tips & hints etc to share?

hired-goons.net has a bunch of stuff, but I don't think there are any
photos of my current batteries.

Quoted message said:

I'd rather use 4/3A size cells to get the longer run time.

Definitely. You can get over 4Ah from 4/3A, which is lots of burn. I'm
running a pack of 10 cells. I made 5 sets of end-to-end cells, then
arrange these in a 3+2 stack. The whole thing ends up being a bit
longer than a glasses case, but a similar size, and velcros under the
top tube.

Quoted message said:

Also the charger MW7168 that seems to be a popular choice. Is
this a smart charger? Does it run off mains or 12v?

The MW7168 is a smart charger, and seems to do a decent job. I've been
using one for a few years now. It runs off 12V, but if you've got
access to old computers, AT power supplies are perfect. The yellow wire
is 12v, the red is 5V and the black is ground (normally) . Put an old
20W 12V halogen across the red and black wires to provide some load on
the 5V line - not all PSUs need that, but it's not hard. Also provides
a nice "the power's on" light.

Dave

The MW7168 is what I use an I'd recommend it.

Random Data said:

Gurrie said:

Anyone got an links, pics, tips & hints etc to share?

hired-goons.net has a bunch of stuff, but I don't think there are any
photos of my current batteries.

Quoted message said:

I'd rather use 4/3A size cells to get the longer run time.

Definitely. You can get over 4Ah from 4/3A, which is lots of burn. I'm
running a pack of 10 cells. I made 5 sets of end-to-end cells, then
arrange these in a 3+2 stack. The whole thing ends up being a bit
longer than a glasses case, but a similar size, and velcros under the
top tube.

Quoted message said:

Also the charger MW7168 that seems to be a popular choice. Is
this a smart charger? Does it run off mains or 12v?

The MW7168 is a smart charger, and seems to do a decent job. I've been
using one for a few years now. It runs off 12V, but if you've got
access to old computers, AT power supplies are perfect. The yellow wire
is 12v, the red is 5V and the black is ground (normally) . Put an old
20W 12V halogen across the red and black wires to provide some load on
the 5V line - not all PSUs need that, but it's not hard. Also provides
a nice "the power's on" light.

Dave

The MW7168 is what I use an I'd recommend it.

Excellent. Thanks guys for all the good tips.

One further question that springs to mind is "matched cells". What is all
that about?

Do I have to ensure that all the cells are within so much tolerance of each
other or something to maximise the performance of the pack?

Thanks again,

Craig

"Oscar" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Random Data said:

Gurrie said:

Anyone got an links, pics, tips & hints etc to share?

hired-goons.net has a bunch of stuff, but I don't think there are any
photos of my current batteries.

Quoted message said:

I'd rather use 4/3A size cells to get the longer run time.

Definitely. You can get over 4Ah from 4/3A, which is lots of burn. I'm
running a pack of 10 cells. I made 5 sets of end-to-end cells, then
arrange these in a 3+2 stack. The whole thing ends up being a bit
longer than a glasses case, but a similar size, and velcros under the
top tube.

Quoted message said:

Also the charger MW7168 that seems to be a popular choice. Is
this a smart charger? Does it run off mains or 12v?

The MW7168 is a smart charger, and seems to do a decent job. I've been
using one for a few years now. It runs off 12V, but if you've got
access to old computers, AT power supplies are perfect. The yellow wire
is 12v, the red is 5V and the black is ground (normally) . Put an old
20W 12V halogen across the red and black wires to provide some load on
the 5V line - not all PSUs need that, but it's not hard. Also provides
a nice "the power's on" light.

Dave

The MW7168 is what I use an I'd recommend it.

Gurrie said:

One further question that springs to mind is "matched
cells". What is all that about?

Matching cells simply ensures that all the cells within a pack are the same capacity. The main place this is important is those little toy RC cars, where the packs can be flattened in less than ten minutes. If one cell is lower in capacity than the others, then it will go flat first. The other cells still force current through the flat cell, and it ends up reverse charged. This destroys the reversed cell in very short order.

This isn't such an issue with bike lights, as the loads are usually much more moderate, and we usually turn the light off before the battery is completely flat anyway.

Regards,

Suzy

Thanks for that.

Craig

"suzyj" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Gurrie said:

One further question that springs to mind is "matched
cells". What is all that about?

Matching cells simply ensures that all the cells within a pack are the
same capacity. The main place this is important is those little toy RC
cars, where the packs can be flattened in less than ten minutes. If one
cell is lower in capacity than the others, then it will go flat first.
The other cells still force current through the flat cell, and it ends
up reverse charged. This destroys the reversed cell in very short
order.

This isn't such an issue with bike lights, as the loads are usually
much more moderate, and we usually turn the light off before the
battery is completely flat anyway.

Regards,

Suzy

--
suzyj