DIY bike lights / AA battery current



TimC said:
*AND*, most importantly, your battery will not last very long at all
if fully discharged. Lead Acid batteries, except for the marine deep
discharge variety thereof, take about 20 full discharges before going
kaput.

SLAs presumably can take the same number of deep discharges.
Lead Acid batteries (sealed or otherwise) come in varieties for standby use (e.g. UPS) and for deep cycle (e.g. electric vehicle, lighting). When discharged to 100% depth of discharge, the deep cycle variety will last 50% more cycles than the standby variety. Standby should last 200 full cycles, a deep cycle 300-350 cycles. Over discharge (i.e. taking out 120% of rated capacity) will shorten this. The deep cycle typically costs 20-50% more than the standby variety. In practice work on running the light to no more than 50% depth of discharge, to allow you margin as the battery ages (and reduces in capacity), and to extend the life out to 500 or so cycles. End of life is when the battery capacity is down to about 60% of new.

A 4AH 12V SLA (probably standby variety) weight 1.74kg and costs $35. The equivalent in NiMH (10 x 4.5AH C-size) is about $130, but about half the mass (1/3 for LiIon). My 10 cell 3.5AH drink bottle pack is about 0.8kg.

Spot the engineer :)
 
ghostgum wrote:

> Lead Acid batteries (sealed or otherwise) come in varieties for standby
> use (e.g. UPS) and for deep cycle (e.g. electric vehicle, lighting).


To ask a practical question, what is the smallest lead acid, deep
discharge battery available? 12v & 6V.

NOT SLA.
 
Terry Collins said:
ghostgum wrote:

> Lead Acid batteries (sealed or otherwise) come in varieties for standby
> use (e.g. UPS) and for deep cycle (e.g. electric vehicle, lighting).


To ask a practical question, what is the smallest lead acid, deep
discharge battery available? 12v & 6V.

NOT SLA.
SLA = Sealed Lead Acid (which really means Valve Regulated Lead Acid = VRLA). You can get SLA deep cycle batteries. Sailing boats typically use 80AH or larger ones of these.

A quick look through the data sheets on my disk showed that the smallest specifically deep cycle was 12V 7.2AH, 2.6kg. A bit heavy for a bike light battery.

The Panasonic data sheets list their smaller batteries as suitable for main (i.e. deep cycle) or standby use, but they look like they are really intended for standby use and will have a life of 200 cycles at 100% depth of discharge. or 420 cycles at 50% DoD, or 1200 cycles at 30% DoD.

Personally I'd prefer to spend the extra on NiMH and have a lighter battery for the 500 nightime rides.
 
ghostgum wrote:

> SLA = Sealed Lead Acid (which really means Valve Regulated Lead Acid =
> VRLA). You can get SLA deep cycle batteries. Sailing boats typically
> use 80AH or larger ones of these.


I know about SLA as we use 7.2AmpHr(~3kg) & 18AmpHr(6kg) on bikes here atm.
OTOH, i also know about 132AmpHr LADD and at 35kg, Ouch.

Just wanted to find out if there was anything in the very small DD capacity.


> but they look like they are really intended for standby use


That is the problem with SLA in my experience.

> Personally I'd prefer to spend the extra on NiMH and have a lighter
> battery for the 500 nightime rides.


That is a big extra in $$$. If it was just lighting and I was using it
every night, then I might consider it, but I've been bitten with
rechargeable before.


Thanks anyway.
 
On Wed, 26 Apr 2006 13:51:29 +1000, ghostgum wrote:

> A 4AH 12V SLA (probably standby variety) weight 1.74kg and costs $35.
> The equivalent in NiMH (10 x 4.5AH C-size) is about $130, but about
> half the mass (1/3 for LiIon). My 10 cell 3.5AH drink bottle pack is
> about 0.8kg.


You need to shop around more. I bought something like 20 cells for
something like $110 a year ago.

Tumtiddly um. It was in the gmail account, not the home one:

http://www.batterypower.com.au had 4500mAH subCs for $7.30 each in
September last year, less 20% if you bought 20. So about half the price
you're talking. My fuzziness was because I was buying some for me and some
for a mate.

--
Dave Hughes | [email protected]
A General Manager who was channeling Captain Bligh only without the
competent seamanship - Patrick R. Wade.
 
On Wed, 26 Apr 2006 18:55:58 +1000, Terry Collins wrote:

> That is a big extra in $$$. If it was just lighting and I was using it
> every night, then I might consider it, but I've been bitten with
> rechargeable before.


If you've got the charger (and I've already mentioned the cheap but
effective one from http://www.oatleyelectronics.com ), and you get cells
from places such as batteryspace.com.au, then you could get a 4.5Ah 12V
system complete for under $100. Yes, it's about double the cost of
equivalent in SLA (7Ah cell + charger), but it'll probably last longer,
and be lighter. I know my twin 7.2V sticks are quite manageable, and power
my HID for a good 4 hours.

For sub 2 hour rides I can use my AA packs. They should go close to 2
hours, definitely 1.5.

--
Dave Hughes | [email protected]
Random miscellany, as opposed to that other kind of miscellany - Patrick
Shaughnessy
 
Random Data said:
On Wed, 26 Apr 2006 13:51:29 +1000, ghostgum wrote:

> A 4AH 12V SLA (probably standby variety) weight 1.74kg and costs $35.
> The equivalent in NiMH (10 x 4.5AH C-size) is about $130, but about
> half the mass (1/3 for LiIon). My 10 cell 3.5AH drink bottle pack is
> about 0.8kg.


You need to shop around more. I bought something like 20 cells for
something like $110 a year ago.

Tumtiddly um. It was in the gmail account, not the home one:

http://www.batterypower.com.au had 4500mAH subCs for $7.30 each in
September last year, less 20% if you bought 20. So about half the price
you're talking. My fuzziness was because I was buying some for me and some
for a mate.

--
Dave Hughes | [email protected]
A General Manager who was channeling Captain Bligh only without the
competent seamanship - Patrick R. Wade.
For lithium battery packs (and nimh) try www.siomar.com (in Perth). I got 2 7.4v 4.4AH batteries for $88 a couple of years ago. So I guess one 14V 4.4AH would be a little cheaper than that. I do remember at the time that that was cheaper than I could buy the equivalent nimh cells (and then I'd have to put them together).
 
slaw wrote:
> Random Data Wrote:
>
>>On Wed, 26 Apr 2006 13:51:29 +1000, ghostgum wrote:
>>
>>
>>>A 4AH 12V SLA (probably standby variety) weight 1.74kg and costs $35.
>>>The equivalent in NiMH (10 x 4.5AH C-size) is about $130, but about
>>>half the mass (1/3 for LiIon). My 10 cell 3.5AH drink bottle pack is
>>>about 0.8kg.

>>
>>You need to shop around more. I bought something like 20 cells for
>>something like $110 a year ago.
>>
>>Tumtiddly um. It was in the gmail account, not the home one:
>>
>>http://www.batterypower.com.au had 4500mAH subCs for $7.30 each in
>>September last year, less 20% if you bought 20. So about half the price
>>you're talking. My fuzziness was because I was buying some for me and
>>some
>>for a mate.
>>
>>--
>>Dave Hughes | [email protected]
>>A General Manager who was channeling Captain Bligh only without the
>>competent seamanship - Patrick R. Wade.

>
> For lithium battery packs (and nimh) try 'www.siomar.com'
> (http://www.siomar.com) (in Perth). I got 2 7.4v 4.4AH batteries for
> $88 a couple of years ago. So I guess one 14V 4.4AH would be a little
> cheaper than that. I do remember at the time that that was cheaper than
> I could buy the equivalent nimh cells (and then I'd have to put them
> together).
>
>


I emailed those guys a few months ago and they never got back to me so I
figured they weren't serious.

Friday
 
Friday said:
slaw wrote:

>
> For lithium battery packs (and nimh) try 'www.siomar.com'
> (http://www.siomar.com) (in Perth). I got 2 7.4v 4.4AH batteries for
> $88 a couple of years ago. So I guess one 14V 4.4AH would be a little
> cheaper than that. I do remember at the time that that was cheaper than
> I could buy the equivalent nimh cells (and then I'd have to put them
> together).
>
>


I emailed those guys a few months ago and they never got back to me so I
figured they weren't serious.

Friday
Best to get on the phone to them these days. Last time I spoke to them they were moving.