Thursday, November 1, 2018

Batteries or rechargeable cells?

The question is whether to use rechargeable battery banks or just plain batteries. I think I have the answer and it's a keeper.

Two weeks ago I went camping with the kids. It was hot and so I brought my 8 inch fan that runs from 6 D-cell batteries. I had not remembered when I change the batteries last so I brought an additional 10 cells with me. Then I misplaced them, borrowed some, then found them. All the while we were talking about running to Walmart and buying a fan and an extension cord.

Now that I'm home I'm looking at my options for the next camping trip. As I looked at different size fans with different recharge capacities I find myself looking at solar and larger batteries. But the question is what is the best solution for my needs. I need to run a descent fan in the tent to keep the kids cool and it needs to run for about 3-4 nights assuming the kids remember to turn it off.

So here I'm looking at some gear. 75000mAH battery for $299; 100W solar panel $200; fan $29. The 60W version of the solar panel is supposed to charge the battery in 10-12 hours. If wattage means anything is this faster. The fan is also rechargeable and has three power sources including a lighter socket which is essentially charging DC-DC; AC-DC would cost an extra 30% for the conversion. And optionally 8 D-cell batteries.

The fan also makes these claims:
Rechargeable Battery Life - up to 5 hours
Alkaline Battery Life - up to 56 hours on Low Speed and up to 37 hours on High Speed depending on brand of batteries selected

So then I started to do the math on my original FAN.

6 D-cells in series. Each D-cell is approx 13000mAh. In series that's 78000mAh. And costs about $10
Just the battery alone (assuming I plugged it in during the day) had the same capacity.

Anker battery 26500mAh

D-cells in series at 78000mAh
Let's not forget the time it takes to recharge the device and that LI batteries behave badly in hot and cold.


I would have to charge this device 30 times in order to get the price per charge to the same as equivalent D-cells. Assuming that the 7.5 pounds and the time to recharge mean nothing.



Solar panels come in many sizes and I have no idea what they mean except the higher the number the more they charge for them. The number clearly indicates how many devices can be charged in parallel or how fast a battery bank will charge.



The description for this fan makes it clear that Alkaline batteries are the way to go. 37 hours; means approx 4 days times the 30x of the bank means that you'd need 120 consecutive days as the duty cycle to break even. If recharging with the 100W solar panel and good sunlight every day then the additional extends another 12 cycles unless you drop the wattage to something that works with the duty cycle.

So, for as often as I go camping with the kids use batteries. As often as I hike on weekends use batteries. As often as there are hurricanes use batteries for the first month and if it looks like it's going to continue then get a solar panel and power bank. In the meantime I think two of these fans makes sense. And just maybe the solar panel.

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