dammit wrote:
I'm wondering if anyone can help with this question.
I have a 530 watt torqeedo battery and I bought the USB adaptor to allow me to charge usb devices.
I noticed you can't just plug in a USB and have it work, unless the remote trottle is connected. Also then it starts searching for GPS, potentially draining the battery further.
I'm going camping and need to conserve the Torqeedo battery as much as possible for emergency use on the water but was tempted to use it to charge go pros, iphone and power banks. I haven't figured out how to translate the 530 watts to mah to understand how much it drains to charge each device. I just turned it on at home to see what a full iphone charge does to the battery %. Update: it took 11% of my 530 watt battery to charge an iphone to 100% from flat, seems like it's not a good option to charge any devices using it unless you are really desperate.
If anyone can shed any light into whether I'd be better stocking up on more powerbanks, I have a bunch of 10,000 MAH ones, to keep the Torqeedo fully charged for its intended use (motor) or if it is hardly going to have an impact on that giant battery charging the odd iphone here and there, it would be great to know!
The Torqeedo batteries are not rated in Watts, but rather in Watt-hours (Wh). So, your 530 Watt-hour battery is capable of supplying 530 Watts of power for one hour.
Other batteries may be rated in Amp-hours (A⋅h) or Milliamp-hours (mAh).
For example, a 10,000 mAh battery can supply 10,000 milliamps (mA) at its rated voltage for one hour. Since 1,000 mA =1 Amp (A), this battery can also be rated as a 10 Amp-hour battery.
Amps or milliamps is a measurement of electrical
current whereas Wattage is a measurement of
power. To measure power (P) in Watts, you need both the battery's maximum rated current (I) and voltage (V). Watts = Current x Volts (P=IE).
So, a 10,000 mAh (10 Amp-hour) battery delivering 5 Volts could be rated as a 50 Watt-hour battery. (50 Watts = 10 Amps x 5 Volts)
The formula to convert Amp-hours to Watt-hours is:
(Ah)*(V) = (Wh)The formula to convert Milliamp-hours to Watt-hours is:
(mAh)*(V)/1000 = (Wh)We can also convert Watt-hours to Amp-hours (or Milliamp-hours) if we know the battery's rated voltage. The Torqeedo batteries are rated for 29.6 V, so the 530 Watt Torqeedo battery could also be rated for 18 Amp-hours (rounded) or 18,000 Milliamp-hours.
The formula to convert Watt-hours to Amp-hours is:
(Wh)/(V) =(Ah)The formula to convert Watt-hours to Milliamp-hours is:
(Wh)*1000/(V) =(mAh)The problem with comparing batteries using only Amp-hours or Milliamp-hours is that you can only directly compare such batteries of
equal voltage, otherwise you will not get an accurate indication of the actual power a battery can produce. For example, if you compared the Torqeedo's 29.6 Volt battery using its 18,000 Milliamp-hour rating to a 5 Volt battery rated as 18,000 Milliamp-hour you might think they're the same, but the Torqeedo battery is a 530 Watt-hour battery whereas the 5 Volt battery is only a 90 Watt-hour battery. So never compare batteries of different voltages using only Amp-hour or Milliamp-hour ratings.
It's hard to estimate how much power is required to charge a smartphone because each uses different capacity batteries and you also have to calculate for charging inefficiencies such as heat loss. But a rough guesstimate would be around 5000 mAh at 5 Volts. So, a 5000 mAh smartphone power bank might be able to charge your smartphone once and a 10,000 mAh might be able to charge it twice. A 5,000 mAh power bank at 5 volts would be equivalent to a 25 Watt-hour battery.
To calculate how many smartphone charges the Torqeedo's 530 Wh battery could supply would be difficult because of the circuitry in both its USB converter and the Torqeedo's Battery Management System (BMS) which is not going to allow the battery to be fully depleted. But I would guess you could get 10 - 20 smartphone charges out of it, again depending upon the size and capacity of your smartphone's battery. Personally, I would not use it for charging smartphones on an extended outing and would conserve its power for the motor.
I hope this helps answer some of your questions.