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Mine Exploration Forum

Author Advice needed on lamp improvements
Pete Monkhouse

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Location: Burton on Trent

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Advice needed on lamp improvements
Posted: 07/02/2019 13:08:40
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Hello all!
I have a batch of 12 home made LED lamps, with which I take gullible groups of friends caving and mining. Unfortunately they are getting a bit long in the tooth (both the lamps and the friends) and I feel the the time has come for some upgrading (the lamps).

They consist of a Q5 emitter on a star heatsink with a plastic push-on reflector mounted in a small diecast box. The driver is a linear 1,2 or 3 7135 chip job, the batteries are a parallel pair of protected 2.4Ah (I think) trustfire 18650 cells and the whole lot came from Deal Extreme.

They are all about 8 or 9 years old, and have had around 10-15 trips a year with no issues at all. However I'm not getting the run time I used to previously and subjectively they don't seem as bright. I'm setting up a test to log voltage and current over a discharge, but I feel I will probably need to replace some (or all) cells.

So - any recommendations for good capacity, protected, good value cells? And should I look at upgrading the LEDs also? I am guessing that a more modern LED will have a higher optical efficiency? I don't (ideally) want to change the box / switch / cable / star mount points / driver if I don't have to.

Any thoughts?

Many thanks, Pete
IP: 148.64.26.219 Edited: 07/02/2019 13:15:23 by Pete Monkhouse
royfellows

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Location: Great Wyrley near Walsall

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Advice needed on lamp improvements
Posted: 07/02/2019 16:45:07
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You came to the right shop.

XRE-Q5s are really obsolete now and looking at the drivers they should still be considered good.

I would move forward by replacing the emitters with Cree XPG-2s which my tests have confirmed best for lower currents. Forget the drums and flags re selling - this is real technology.

You may wish to change the reflectors if tarnished and in any event will need the small plastic adaptors as the XPG is a smaller footprint.
As the power packs are fixed and not replaceable batteries they cannot be fitted wrong way round, so any reverse polarity protection diode is not only unnecessary but taking power in waste. If is an ordinary small signal diode is stealing 0.7 volts from the Li Ion discharge range of 2.5v to 4.2v. If its a Schottky its still taking 0.33 volts. Remove and bridge with a soldered wire.

Main issue is the JunkFire, sorry TrustFire (Trust!!!) batteries. Replace with good quality Sanyo 3500 mAh cells. I would also ensure that they are protected by a management circuit.

All this kit can be obtained from the same reliable shop https://www.fasttech.com/ but expect weeks on the Li Ion cells as they have to come overland.

Another source of cells is Margaret who lives near me and I can thoroughly recommend, you will find her selling on eBay.
Its all genuine stuff.

For the benefit of any clever Dicks genuine cells can be confirmed on arrival as they will all be at the same 'factory voltage' within 0.01V, impossible to reproduce in fakes.

--

Looking forward to NAMHO 2019. www.cambrianmines.co.uk
IP: 92.23.160.152 Edited: 07/02/2019 16:55:09 by royfellows
royfellows

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Advice needed on lamp improvements
Posted: 07/02/2019 16:51:02
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Here she is:
https://www.ebay.co.uk/itm/2x-Sanyo-NCR18650GA-Li-Mn-3500mAh-INR-10-20A-3-7v-18650-battery-case-UK-genuine/182235740604?epid=2256157998&hash=item2a6e18b9bc:g:MIEAAOSwlzZbKTaR:rk:2:pf:1&frcectupt=true

--

Looking forward to NAMHO 2019. www.cambrianmines.co.uk
IP: 92.23.160.152
Pete Monkhouse

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Advice needed on lamp improvements
Posted: 07/02/2019 18:19:15
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Many thanks indeed Roy. XPG-2's ordered, but I couldn't find any suitable reflectors. Will try bonding the existing ones in place as a starting point.....

I knew you were going to say that about the trustfires! I'd love to fit some Sanyo or Panasonic but I don't think I can justify buying 24 of the things at £6 each. I'll test the condition of what I have and have a think.....

We were ever so close to building a pure electric Le Mans 24-hour race car last year, but sadly the financial side of the deal fell through. This would have needed something like 12 battery packs, each with around 10,000 18650 cells. I was greatly looking forward to the selecting and testing phase, and had plans for some of the 'not quite good enough' cells as you can imagine!
IP: 148.64.26.219
royfellows

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Advice needed on lamp improvements
Posted: 07/02/2019 19:28:20
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Pete Monkhouse wrote:

I'll test the condition of what I have and have a think.....


Would you like me to read your tea leaves?
Laugh

--

Looking forward to NAMHO 2019. www.cambrianmines.co.uk
IP: 92.23.160.152
royfellows

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Advice needed on lamp improvements
Posted: 07/02/2019 19:31:27
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Bit more
I dont know how your cells are housed but if you are using 18650 battery holders (held by springs) beware of fitting unprotected OEM cells with a management circuit. A sharp jolt could cause a disconnect which would cause turn off and need reconnecting to a charger to come back on line.
Not as issue with protected cells in holders.

--

Looking forward to NAMHO 2019. www.cambrianmines.co.uk
IP: 92.23.160.152
Pete Monkhouse

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Advice needed on lamp improvements
Posted: 08/02/2019 09:21:23
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Soldered onto each end of the (protected) cell pair. Wrapped in self amalgamating tape, then insulating tape. Bargain basement but they’ve lasted 8 years Smile IP: 31.100.174.104
royfellows

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Advice needed on lamp improvements
Posted: 08/02/2019 11:11:14
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If the cells are in pairs there is a Hammond box that just takes them and allows for a PSB and cable gland, but need sealing in as box isn't waterproof.
Use the black nylon glands with cable support, tension on the cable with metal glands causes failures.
Issue with wrapping cells is poor protection against rock contact and tendency for water to ingress where the cable enters. As per the old style Stenlight batteries.

--

Looking forward to NAMHO 2019. www.cambrianmines.co.uk
IP: 92.23.160.152 Edited: 08/02/2019 11:11:36 by royfellows
Pete Monkhouse

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Advice needed on lamp improvements
Posted: 10/02/2019 10:40:16
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Hi Roy (and others!)

Have you built any lamps with boost/buck regulators? I'm looking at the LTC3454 although I suspect there are many alternatives. It would seem to offer both a good efficiency boost and better utilisation of the cells capacity than linear drivers.

Regards, Pete
IP: 90.243.182.23
royfellows

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Advice needed on lamp improvements
Posted: 11/02/2019 13:52:29
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Pete Monkhouse wrote:

Hi Roy (and others!)

I'm looking at the LTC3454 although I suspect there are many alternatives.

Regards, Pete


I have not worked with one of these but ponder on the output of 5.15v - 1 amp?
The advantage of the boost is that your lamp will hold full power throughout the battery discharge range, which some may not want.
Farnell are no longer stocking them.

Thing is that looking at the XPG 2 data sheet we get just over 3V Vf at a 1 amp drive current, so you are gaining little by complicating the electronics. Also, on the lower end of the discharge range using 7135s your lamp will into a 'slow death' which many will consider desirable.

Linear drivers typically have same current in as out so excess voltage is burned off as heat. However, chips like 7135s are reliable and work well where the voltage overhead is low, typically parallel or single Li Ions operating on the range of 2.5 - 4.2V. They are also readily available already mounted in torch drivers got cheap from HK

Higher voltages driving series wired LEDs work better with switchers, and best in my experience where the Vf or the LED array is matched to voltage in.

I have not worked with boost drivers but have 'played' with them.

Building your own driver PCB from scratch is bit more than throwing a lot of components together on a breadboard as you will need to get a PCB made up, although there are firms that handle small quantities, you find them on the web.

Above is my opinion, some may disagree.

--

Looking forward to NAMHO 2019. www.cambrianmines.co.uk
IP: 92.23.160.152
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