Battery powered Lumotec front light

[Socks]

I acquired an old bottle dynamo and front / rear lights, don't plan to use the dynamo however I have seen a suggestion that a battery (output 7.5 volts or thereabouts) works with the front light.  It is a B & M Lumotec IQ cyo plus.  Older version, without the little reflector underneath the lense.

Has anyone tried this?  And for you electrickery types, what sort of Amp hour battery would give a long run time between re-charges?

[BFC]

The basic design of LED lighting is DC at the LED components.
The dynamo input to it is AC.
Basic designs will use a rectifier of some sort to convert the AC into DC - these loose some energy as heat and could be overstressed (die) if running from a DC source at/above their rated current, before E-bikes very few considered running dynamo lights from DC so the design and testing probably didn't include your scenario.
Identifying the circuit area where the light is running on DC would be the optimum point to inject energy from a battery, avoiding risk of diode failure (fire?).

[aidan.f]

How about I tidy my workbench and you take a ride over with it? I may even  have a suitable spare battery pack

[Polar Bear]

I have a Cyo knocking about somewhere which I used with 6 rechargeable AA cells in a battery caddy.  A friend soldered on one of those battery terminal clips for 9v batteries.  It was possible to connect a rear light too using the tails from the Cyo.

The light was bright and didn't appear to have any problems running from batteries.  I used it as a second light in very dark areas and a standby light just in case the dynamo setup failed.  The Son dynamo and associated wiring etc. never let me down.

[Kim]

If you check the manual, you'll see that non-premium Cyos are specified to run from 7.2V DC, with an absolute maximum rating of 7.5V (and a specific polarity).  In testing, I found that the apparent brightness drops off rapidly with voltage, so you really want to stay as close to that 7.5V as possible, as long as you don't exceed it.  I powered the one on barakta's trike using a regulator designed for Power-over-Ethernet applications, which can accept the 52V from the nominally 48V traction battery and outputs a rock-solid 7.5V for the lighting.

Meanwhile, the Cyo Premium manual fails to specify a DC voltage, and suggests that you invest in the e-Bike version, which accepts a wide range of voltages (presumably without brightness issues).  It then goes on to warn you about polarity, suggesting that DC operation is still possible.

In my previous post, I measured the steady-state current of barakta's trike lighting system (ie. one original 60lux Cyo and two Spanninga Pixeos, running at 7.5V) at 300mA, which should suffice to calculate run time.

[sojournermike]

I have a IQ-XE that I run off a 2 series Li-Ion pack, so 8.4 down to c.5.5v. It’s species down to 6v, but seems OK in practice. On a 4 cell 2S2P 6800mah pack it last a long time - certainly over 6 hours, which is reasonable given its 7watt rating.

Sorry,know it’s not much use for a Cyp, but it’s another datapoint for others interested.