Batteries again

[Colin Blackburn]

In a recent post about my not-much-use Cateye SLA battery a couple of people suggested I build/buy
my own battery rather than shell out 20 quid for a replacement Cateye one. One suggestion was to use
NiCad or NiMH to replace the SLA. I'd like to keep the Cateye bottle-holder container for its
convenience and connectors. Is there a single battery that will fit into this case (I assume there
is a single SLA in there) or am I going to have to buy separate cells and connect them somehow? Any
pointers appreciated.

Colin

 

[Alex Graham]

> Is there a single battery that will fit into this case

Probably not

> (I assume there is a single SLA in there) or am I going to have to buy separate cells and connect
> them somehow? Any pointers appreciated.

Assuming you can get into the casing you can buy 'tagged' cells (they are the same dimensions as
normal cells but have a tag welded to the end, to which solder will adhere. So If you can solder
then its pretty easy to solder some cells together. You can buy up to about 7Ah cells (they are
quite big). Your SLA is probably 4Ah or so at 6V I would guess, or more like 2Ah at 12V.

To make a 6V pack I would be buying 4 or 5Ah C or D cells (they will be about 4 quid per cell)
and wiring them in series. This will be about the same capacity as your SLA, but about a fiver
more expensive and about half the weight. NiCad and NiMH arent rampantly different, but NiMH are
a bit more expensive and a bit better. See Myras articles on the pros and cons at
www.myra-simon.com I think.

The only thing you will need then is a charger. For my NiMH pack I built a MAX713 circuit (which
would fine for NiCad too) and its pretty good, as it charges in about 4 hours and terminates itself.

Hope this helps,

--
-Alex ----------------------+ Alex Graham | [email protected] | ----------------------+

 

[Colin Blackburn]

In article <[email protected]>, [email protected] says...

> Assuming you can get into the casing

I think I can, there look to be some screws buried deep inside some holes.

> you can buy 'tagged' cells (they are the same dimensions as normal cells but have a tag welded to
> the end, to which solder will adhere. So If you can solder then its pretty easy to solder some
> cells together. You can buy up to about 7Ah cells (they are quite big). Your SLA is probably 4Ah
> or so at 6V I would guess, or more like 2Ah at 12V.

I'm not too hot on soldering but I have an entire physics department at my disposal so I should be
able to put something together.

> To make a 6V pack I would be buying 4 or 5Ah C or D cells (they will be about 4 quid per cell)
> and wiring them in series. This will be about the same capacity as your SLA, but about a fiver
> more expensive and about half the weight. NiCad and NiMH arent rampantly different, but NiMH are
> a bit more expensive and a bit better. See Myras articles on the pros and cons at
> www.myra-simon.com I think.

Ta.

> The only thing you will need then is a charger. For my NiMH pack I built a MAX713 circuit
> (which would fine for NiCad too) and its pretty good, as it charges in about 4 hours and
> terminates itself.

Is there an off the shelf alternative? Maplins?

Colin

 

[Myra Vaninwegen]

Colin Blackburn <[email protected]> wrote
> In a recent post about my not-much-use Cateye SLA battery a couple of people suggested I build/buy
> my own battery rather than shell out 20 quid for a replacement Cateye one. One suggestion was to
> use NiCad or NiMH to replace the SLA. I'd like to keep the Cateye bottle-holder container for its
> convenience and connectors. Is there a single battery that will fit into this case (I assume there
> is a single SLA in there) or am I going to have to buy separate cells and connect them somehow?
> Any pointers appreciated.

There are instructions for a DIY water bottle battery here:

http://www.myra-simon.com/bike/bott-batt.html

We modified a power tool charger to make a smart charger for the battery:

http://www.myra-simon.com/bike/charger2.html

It was quite an old charger, and I don't know how easy it is to find a suitable power tool
charger nowadays.

-Myra

 

[Alex Graham]

Colin Blackburn wrote:

> Is there an off the shelf alternative? Maplins?

Thing is it needs to charge 5 series cells so probably not. You could charge them with a normal PSU,
but a constant current charger is much better. I used the PCB layout at

http://home.concepts-ict.nl/~delemarre/id54.htm

Which works very well. The components will cost around a fiver I think, add a aluminium box from
maplin and you have quite a nice charger. I could have bought one from lumicycle designed for a
battery like mine for 40 quid! Quel rip-off!

You could build a new bottle battery like:

http://alexpg.ath.cx:3353/lights/battery.php

--

-Alex

----------------------------------
[email protected]

http://alexpg.ath.cx:3353/cycling.php http://www.westerleycycling.org.uk
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[Tony Yates]

"Colin Blackburn" <[email protected]> wrote in message
news:MPG.18bc255e1a0cbaec989787@localhost...
> In a recent post about my not-much-use Cateye SLA battery a couple of people suggested I build/buy
> my own battery rather than shell out 20 quid for a replacement Cateye one. One suggestion was to
> use NiCad or NiMH to replace the SLA. I'd like to keep the Cateye bottle-holder container for its
> convenience and connectors. Is there a single battery that will fit into this case (I assume there
> is a single SLA in there) or am I going to have to buy separate cells and connect them somehow?
> Any pointers appreciated.
>

Funny but I've been looking into this quite a bit recently.

I've just put together a pack using 6 approx £22 18650 NiMH cells, this provides 4.5Ah at a nominal
voltage of 7.2V (it's actually 8.4V when fully charged). For charging I bought a charger from CPC
(www.cpc.co.uk) for about £10, I like this charger as it is selectable for the number of cells in
the pack and also has a selectable current output of either 500mA or 1A, it also goes into trickle
charge at the end. It charged my battery in roughly 5 hours.

This battery weighs in at about 360g, I think the cateye SLA is nearer 1Kg.

I have used this battery straight into my lights, but ideally I'll be using a voltage regulator and
cutoff protection.

hope this helps. Tony www.therush.uk.com

 

[Alex Graham]

Tony Yates wrote:

> Funny but I've been looking into this quite a bit recently.
>
> I've just put together a pack using 6 approx £22 18650 NiMH cells, this provides 4.5Ah at a
> nominal voltage of 7.2V (it's actually 8.4V when fully charged). For charging I bought a charger
> from CPC (www.cpc.co.uk) for about £10, I like this charger as it is selectable for the number of
> cells in the pack and also has a selectable current output of either 500mA or 1A, it also goes
> into trickle charge at the end. It charged my battery in roughly 5 hours.

Yep! 18650s are brilliant arent they! For some reason CPC sell the cheaper than the C cells equiv,
still I'm not complaining!

I didnt know they sell the charger as well - that certainly makes it easier.

You dont need a voltage regulator as such - a fuse would do nicely. I think it would be sensible
too! I have blown the fuse a few times while measuring the voltage etc and was glad to have a blown
fuse and not a smoking battery!

--

-Alex

----------------------------------
[email protected]

http://alexpg.ath.cx:3353/cycling.php http://www.westerleycycling.org.uk
----------------------------------

 

[Tony Yates]

"Alex Graham" <[email protected]> wrote in message news:[email protected]...

>
> Yep! 18650s are brilliant arent they! For some reason CPC sell the cheaper than the C cells equiv,
> still I'm not complaining!
>
> I didnt know they sell the charger as well - that certainly makes it
easier.
>
> You dont need a voltage regulator as such - a fuse would do nicely. I think it would be sensible
> too! I have blown the fuse a few times while measuring the voltage etc and was glad to have a
> blown fuse and not a smoking battery!
>
> --
>
> -Alex

The charger is great IMO escpecially for r&d with differing numbers of cells and capacities.

Agreed on the fuse, I have one installed just forgot to mention it - doh! I'm thinking of using a
regulator to limit the voltage down from the 8.4V to
7.2V so that I'm not overvolting quite as much.

Actually, I think I'll be concentrating on the cut off circuit to protect the cells from
overdischarge.

FYI, I've found a source of Li-ion cells that are 3.6V and 10Ah, two of these babies will give me my
required voltage but with a whooping 10Ah, with a weight of just 760g.

regards, Tony

 

[Alex Graham]

Tony Yates wrote:

Blimey - are the expensive? and how are you going to charge them?

--

-Alex

----------------------------------
[email protected]

http://alexpg.ath.cx:3353/cycling.php http://www.westerleycycling.org.uk
----------------------------------

 

[Tony Yates]

"Alex Graham" <[email protected]> wrote in message news:[email protected]...
> Tony Yates wrote:
>
> Blimey - are the expensive? and how are you going to charge them?
>
> --
>
> -Alex

This is where it all gets a bit tricky, on the face of it if I buy in bulk (11+) then each cell is
approx £13.00, the killer is the p&p as they're coming from abroad.

As for charging, the supplier can build me one, or I can do my own.

regards, Tony

 

[Colin Blackburn]

In article <[email protected]>, mvi20 @cl.cam.ac.uk says...

> There are instructions for a DIY water bottle battery here:

Thanks to all again. I found your pages after Alex's post. I'll start getting the bits together.

Colin

 

[Stephen Pridgeo]

"Tony Yates" <[email protected]> wrote in message
news:<[email protected]>...
> "Alex Graham" <[email protected]> wrote in message news:[email protected]...
> > Tony Yates wrote:
> >
> > Blimey - are the expensive? and how are you going to charge them?
> >
> > --
> >
> > -Alex
>
> This is where it all gets a bit tricky, on the face of it if I buy in bulk (11+) then each cell is
> approx £13.00, the killer is the p&p as they're coming from abroad.
>
> As for charging, the supplier can build me one, or I can do my own.
>
> regards, Tony

Tony, very interesting, please keep us posted on how you get on if you do do this. I'd be
interested, and I'm sure many other people would be. TA SteveP