Rechargable Lantern Battery Flashlight Mod
I have several 6 volt lantern flashlights kicking around the shop. However, I never use them because I generally baulk at the $7 they want for a lantern battery that can't be recharged.
But the other day I noticed a 4Ah 6 volt recharable lead acid battery at Home Depot, these are made to be back-up power sources for emergency exit lights and they cost between ten and twenty bucks. But more importantly they are very close in size to the 6 volt lantern battery.
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To modify my flashlight I cut off the outer connector ring to prevent the possibility of the battery connectors shorting, then I soldered wires to the two connections and crimped quick disconnect lugs to the ends.
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I added a second pair of wires to the lugs and soldered those to an RCA connector that I press-fit into the back of the flashlight. This connector is for recharging the battery. I reassemble the flashlight with a piece of Styrofoam filler to keep the battery in place.
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A 6 volt lead acid battery will need a charger that delivers a bit more than 6 volts in order to take a charge. I searched my big basket of wall-warts and found one that would provide about 250 ma when connected to the battery and plugged in.
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Since this is a 4 Ah battery, 250 ma is just about the ideal 20 hour charging rate.
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My lead acid battery turned out to be about 1/4" taller that the 6 volt lantern battery and the flashlight head would not quiute screw all the way on. This was easily remedied by setting my heat gun at about 400 degrees and heating the polyethylene case until it softened and stretched, you have to heat and stretch the case beyond it's elastic point to retain the extra room for the battery.
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Now I have a fully rechargeable flashlight and the lead acid battery will pay for itself in just 2-3 cycles!
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Comments
Nice
Good idea, very ecological. Reminds me of something my dad used to do. He's a member of the local mountain rescue team, and they all used to use big lanterns like this one. Of course, in the days before LEDs were so far along, these were very heavy, and so the standard modification was to remove the battery, and install a cable that ran into the rucksack, where the weight could be carried mroe comfortably.
Beam Hack
Mind not power-related but a simple hack I did on some Ray-o-Vac lanterns found in clearance at a local Target store, which should work as well on other similar sized items.
Quite by chance I discovered the lightweight tins that Archer Farms hot chocolate mix is packaged in is the same diameter as the lantern's lens outer ring assembly. After removing the bottom of the container, the now-open cylinder slips on as a 'hood' and will assist in 'tightening up' the usually dispersed floodlight beam. Lining the interior of the cylinder with reflective Mylar film does dramatically improve the effect.
One other little trick, flatten out a clear two (2) liter soda bottle and use the lantern's outer lens ring as a template to cut a circle the same size as the factory produced lens. You now have a replaceable inexpensive protective cover that fits over the lantern's original lens, preventing those annoying scratches which can fog up such over time.
While you have that lens assembly apart, cut two silver dollar sized discs from any scrap Mylar on-hand, glue one disc, reflective side out, to each side of a same-size disc of lightweight cardstock then center the sandwiched disc between both lenses, affixing with a bit of two-sided tape works best.
Placing that little disc dead-center actually helps 'collect' a bit of 'waste' light, and in my experience, further tightens the beam.
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rechargable lead acid deep cycle batteries
I have taken a couple of conventional EFI Uninteruptible Power Supply units and hooked up large deep cycle lead acid batteries in parallel with the small batteries inside the units. Trouble was, ordinary "trolling motor" batteries have a float voltage of 13.2 volts. The sealed gell cell types float at 13.8 volts. The difference is significant, as the UPS units are designed to keep gell type batteries happy. The liquid-filled batteries eventually died of overcharging, even when kept full of liquid at the proper level. Unavoidable sulfation. I guess I could have put a resistor in the circuit to lower the charge voltage, but that would have confused the UPS, causing it to charge constantly.
Finally, I bit the bullet and coughed up $150 for an 80 amp hour Dekka battery designed for use with solar panels. It's been in service for 10 years now, and when the power in my very rural home quits on me, I can watch TV or use the computer for a dozen or more hours. Or, you could try to find some ancient Edison nicad batteries that were used in passenger trains to keep the lights on when they weren't moving. They are infinitely recyclable.
For flashlights, buy new nickel metal hydride (nmh) batteries that can take the abuse.
The Joule Thief ! Read up on
The Joule Thief !
Read up on a simple circuit called a joule thief that allows you to use batteries long after they're oficially dead !
Raising the dead with electricity ? - thought this might appeal .
You can use the small ferrite bead in a compact low energy lamp, and the transistors & caps in there too.
Swap your bulb for high brightnes LED's and you're good to go.
You could even have two modes built into one lamp.......time for another project I think.
BTW, lantern batteries are ideal sources for Zinc Plate, as the case is plastic. Just crack off the top in a vice, and remove the long cellsx4 cut base off and one cut up the side leaves you with a 4" square piece of zinc sheet.
it's a good way to reuse
it's a good way to reuse those clunky flashlights.
limitations on lead acid batteries
A coworker gave me a heads up on a behavior of lead acid batteries that is important to know. I understand it to mean that you don't want to deep discharge your battery.
This is from the wikipedia article about lead acid batteries:
Lead acid batteries designed for starting automotive engines are not designed for deep discharge. They have a large number of thin plates designed for maximum surface area, and therefore maximum current output, but which can easily be damaged by deep discharge. Repeated deep discharges will result in capacity loss and ultimately in premature failure, as the electrodes disintegrate due to mechanical stresses that arise from cycling. A common misconception is that starting batteries should always be kept on float charge. In reality, this practice will encourage corrosion in the electrodes and result in premature failure. Starting batteries should be kept open-circuit but charged regularly (at least once every two weeks) to prevent sulfation.
Not to worry
"Lead acid batteries designed for starting automotive engines" -- this battery is an SLA not a car battery. I wouldn't suggest too deep of a discharge, but it is not the same as a car battery where it cannot be dicharged much at all. gruber power services is cheaper than home depot FYI.
Gel-cells can be run down
Gel-cells can be run down pretty far - the important thing is not to leave them discharged. As soon as the light starts to dim, put it on the charger overnight. I also have a charging station with a 24 hour timer I can plug various chargers into so I don't forget and overcharge a battery.
A good hack. For those not so inclined you can go the lazy route
This is a excellent idea and I did some digging at my fav battery site and found this 6-Volt Lantern Battery that can do the same thing if you're lazy and willing to put up with a lower Ah rating.
Oh cool! Thanks for the link!
Oh cool! Thanks for the link!
Those lantern batteries if
Those lantern batteries if you crack them open contain a few dozen double A batteries that you can use in a pinch, price wise it ends up being cheaper than buying the same amount in traditional blister/cardboard packages.
I saw another mod using radio$hack double A battery holder packs daisy chained together and stuffed into the same housing with a power jack wired inline and ported through the back of the lantern to hook up to an external charger and the lantern light was swapped with an LED mod light.
The one I just cracked open
The one I just cracked open has 4 batteries that are "D" cell diameter but about half again as long.
It might be brand specific as
It might be brand specific as I remember seeing this bit of information on a eco science type show years before it was the in thing to be eco. That being said I'm not going to encourage you to buy other brands to try this out however it is good to know that its D cells now and I'm assuming that if all companies went to D cells it was probably cost related.
Ray-O-Vac poly case 6 volt lantern
I had a similar project,using an old poly cased 6 volt lantern battery flashlight-
But I salvaged a set of NI-mh batteries from a laptop battery and made a 9 volt pak for the brighter light.The bulb is a xenon 9 volt from a 6D type cop flashlight,and styrofoam is the cushioning.The NI-mh batteries obviously were not the problem the laptop was having ,because this flashlight has been working for five years now.I charge it for an hour with a 500ma wall rat before it goes dead.
Think of how many $6 lantern batteries I would have bought.And Landfilled.Yow! There should be a law against making anything but rechargeables.