Wow. Batteries have improved

[Sideband]

I was very generously given an old Dive-Rite 50W halogen light which has a battery box instead of a canister type tube. I was considering making a canister battery housing for it so I was checking out both SLA batteries for use now and C/D cell rechargeables to make a battery pack for the canister. The SLA batteries were about what I expected in terms of size and capacity. I was shocked though when I saw NiMH D cells with 1.2V 9Ah ratings. Zounds! 10 of those would make a great sized battery pack and even a 50W lamp would get enough burn time for 2 decent dives and still not be totally zapped. A 10W lamp could last a weekend of night dives.
For fun I like to design and build different robot platforms and thought those 6V 7Ah SLAs were a great find. A bit heavy, but they have lots of juice and can power the larger motors I tend to use. I never would have thought they had packed that in C and D cells because back in my day a 900mA NiCad was a good batery or so I thought and which I also thought was recently. These aren't cheap though so the SLA may win out yet.

Joe

 

[Brandon]

You shouldn't need 10 of the cells... these NiMH batteries are trickery. When you charge them, they'll peak around 1.6v a cell, so with 10, you'll start at 16 volts, and be down to 12-13 after the first 15-30 minutes. It should stay in between 10-12 volts for another hour or so.

Total burn time should be close to 1.5-2 hours.

One concern is that 16 volts will be more than your light bulb can handle. The 50w bulb should have been designed for 12v, and while it might handle 16, it might not do it reliably.

A voltage regulating circuit would solve this problem though.

I'm sure you're familiar with P=VI. Your 12v head at 50w will draw 4.16 amps of juice, making those 9k or 10k mah batteries a necessity if you want to use it for more than one dive.

Just some ideas. Designed plenty of electric power systems for R/C aircraft. =)

-Brandon.