High Capacity 6 V lantern battery pack

[HarryN]

Hi

My son, an up and coming 8 year old flashaholic, picked up a 6 Volt (edit) spotlight with a 4 inch reflector (end edit) as a present (for himself).

He soon realized that, despite it's size, it has limited power and battery life, and there appear to be no commercial, high powered, primary cell based, 6 V lantern battery alternatives on the market.

I would like to juice this thing up with a more powerful bulb and a pack made, NiMH pack with REAL power. It appears that I can get one made up from 4 x SAFT 15,000mah NiMH cells, that can pump multiple amps for an extended period of time. Here is the link to the cell which would be used:

http://www.saftbatteries.com/130-Catalogue/PDF/VH_F_15000.pdf

To get this custom configuration will cost around $ 120 - 130, each.

Does anyone else think this is interesting, or am I really out on a crazy path here ?

 

[Flash_Gordon]

Seems like it might be overkill. A standard alkaline lantern battery is 26,000 mAh capacity, although that rating is at a fairly low current draw. 15,000 will leave you with somewhere over half the runtime. You can put together an NiMh pack and charger in the 2 Ah range for less. You probably need two batteries so they can be rotated while one is charging.

Check with CPF supporter battery station .

Also, for $120-$130 you can buy some pretty nice rechargeable lanterns.

Mark

 

[HarryN]

Flash - the ratings of the commercial 6 Volt lantern battery capacity is based on less than 50ma discharge rates. If you pull anything close to 500ma, the capacity crashes to almost nothing.

The 15,000mah rating for these cells is really 15 amp hours, so a light that pulls 3 amps will run essentially for 5 hours. In a bit more real world example, a 1.5 amp lamp would run for 10 hours, compared to maybe 10 minutes with an off the shelf battery.

The application is a 6 volt spot light with a 4 inch reflector, sorry if I implied a lantern.

 

[paulr]

Spotlights are usually powered by internal SLA packs. You could use four NiMH D cells (11000 mAH) which are around $10 each from Amondotech to get somewhat higher energy density.

 

[BatteryCharger]

Also, for $120-$130 you can buy some pretty nice rechargeable lanterns.

Definately. I think the HF HID spotlight is around that much, which would totally put to shame any 6v lantern, and comes with a rechargeable battery. There are of course several other much longer run time/not as bright rechargeable lanterns as well.

As far as a cheap option for a rechargeable lantern battery, 4 NiMh D's would make the most sense, and would give you a run time MUCH longer than an alkaline battery. They even make 4D to lantern battery adapters.

 

[HarryN]

Thanks for the HID ideas. Just as a reminder, this is for an 8 year old, so a 35 watt HID that weighs in at 13 lbs is not appropriate, at least not yet. Yes, that is a lot of light. I cannot buy him a light that is brighter than mine.

Based on the mfgs specs, a 35 watt HF HID package has a nominal 20 watt-hour battery pack, so it would run for less than 30 minutes. The goal is actually "a little brighter" and " run a lot longer".

The 4 D cell NiMHs idea is not bad, and the adapter idea is interesting too, but of course, that is still wasting a lot of space in the light, and after all, I have to do something a little bit outrageous, or it won't be any fun.

As far as which brand - I am pretty gun shy of rechargeable cells, (due to a bad experience) so if I am going to get into these, brand name / experience / top of the line durability is a big deal for me. Saft and only a few others would be viable for me.

The 4 x F cell pack is a nominal 70 + watt - hours. That allows long run times with bulbs in the 5 - 10 watt range - plenty for his use. That would make this capable of a variety of "sleeper" upgrades over time - sort of like the silly things people do with M*g bodies. :laughing:

 

[Yooper]

Those cells are rated at 50 amps! Definitely overkill, unless you want to run a 250W bulb or something...

A Radio Shack XPR103 bulb would be a nice choice for this light. It's a nominal 3.6V bulb that takes to overdriving up to 6V nicely.

One nice thing about using something like D cells in a battery holder is they are easier to manage for charging and you don't need a specialized charger like you would with your custom pack. It's also easier to replace a single cell if one goes bad, and you can always throw in a set of alkalines in a pinch. If it was me I'd use 4 D cells from amondotech and be pretty happy with 11 ah for a lot less money.

 

[HarryN]

Thanks Yooper - I threw away my last consumer level charger, and currently am only using primary cells, so going into this "package" involves buying a quality charger for a variety of uses anyway. The charger will likely cost more than the battery pack based on what I am reading in the charger comparison thread.

I understand your recommendation about using an off brand / lower cost cell, but if you understood the history, you would see that while economy is nice / important, the decision to do this setup is not really an economically based one - it is just a crazy idea, which would need to have minimal risk.

I am actually a bit nervous about having a battery pack with that kind of discharge current in his light. He can open up the light, and might do something silly with a screwdriver. I guess I could glue it shut, and put a protected jack plug on it.

 

[Sway]

I've played around with plastic 6V lanterns a little, you are limited to around a 10W lamp because of the plastic reflector, lens and bulb holder.

Some can be a real PIT to mod because of the bulb contact/holder apparatus making it easier just to by-pass or remove those parts and solder direct to the + tip of the bulb and the - contact ring on the reflector with wires leading to the switch and pack. Count the number of turns it takes tighten the bezel down and wind your wires backwards and then screw the bezel on.

You can pack it full of AA or C cells in holders or a pack it just depends on the brightness and run time you want. 8 NiMH AA's will drive a 6 cell lamp pretty good or back off to 7 for longer bulb life. Add a DC power plug to the light somewhere and wire it to the cells and you can charge them in the light.

You can also tweak the focus using small shims or washers between the PR bulb flange and reflector to get some really nice throw out of the larger reflector.

Hope the ideas help


Later
Kelly

 

[k1_]

Guys, guys, guys. Am I to believe my eyes? Actual flashaholics suggesting that hotwiring the kid's spotlight is overkill? I'm going to pretend I didn't read that. HarryN, not only do I endorse your interest in more power capacity and more power output for your kid's spotlight, I salute you.

Now, you've brought up the power pack, and are clearly thinking about better runtime. There's been some hinting about higher-output bulbs, but no talk about reflectors and the whole flood vs. throw issue. And finally, what hotwire would be complete without one of winny's PIR sandwiches?

My advice: go for it.

k1

 

[HarryN]

Kelly - Thanks for the comment about using a plug vs the original spring contacts - I think that is a good point.

K1 - Thanks for the comment. I was going to start slow and build it up from there. Probably start with a standard PR base lamp or Carley lamps setup. I am still reading / learning about the whole bi-pin base arrangement. I am not particularly patient, and focusing a bi pin might be more than I can take.

I had thought about using a Lux V in it, but there is really no good way to get the heat out unless I start from scratch.

With a plastic reflector, there definitely are limits, and frankly, this thing has a rather un - impressive beam quality. I have purchased reflectors, etc from Carley before, but they do not have a 4 inch Al one that I have found. That will probably limit things for a while. 10 watts is probably a good limit for him anyway.

Maybe Carley's 3 inch reflector will have better performance than the existing 4 inch. Flood vs throw - we are not there yet for this light. Throw is probably higher on the list, since we already have floody lights.

I could fuse the battery pack to 3 - 4 amps, and fully wrap the pack to keep him from frying himself, at least until he is 10. :shrug:

 

[Ray_of_Light]

If you replace the 6 volt lantern battery with a SLA 6 V 4Ah, and the bulb with a HPR 5.5 V 1 A from Philips - you will have a nice rechargeable setup. The existing bulb holder and the reflector will not need replacement.

Anthony

 

[k1_]

Fusing the battery pack seems like a good security measure. At least he'd need to learn something about desoldering before he could cause more trouble.

As lamps go, I've heard good things about the WA 1111-U, especially if you're considering a possible hotwire. 465 bulb lumens at 6v, and possibly a few more when the pack is fully charged.

And then if you wanna go further, awr's hotrater.xls spreadsheet says 800-something bulb lumens at 7.2v. You'd definitely need a metal reflector for that.

k1

 

[Meduza]

You could maybe use the ROP Low bulb to mod it

11w @ 6v and a few hundred lumens, you could get away with that in a plastic reflector, you can maybe cut a little bigger hole to let some of the heat out and not damaging the reflector...

 

[HarryN]

Not sure if this is a good thing or not, but I noticed that with only minor changes, I could get a 4 wide x 2 high pack of D cells in this light.

Thanks to Evan1962 pointing out these

http://www.saftbatteries.com/130-Catalogue/PDF/VH_D_9500.pdf

8 of these in series puts the pack at a nominal (math error correction) 9.6 volts and 90 - 100 watt hours. I might have to think the bulb question through in some detail. A 10 watt bulb with a 15 hour life span would need to be replaced almost every charge cycle. :laughing: