# Adjust voltage drop using on board voltage step-up

I am transmitting power over tether (12 AWG 50ft wire). Voltage is 12v and expected current draw would be around 20A which would result in about 3 volts drop. I am thinking of using automatic step-up module like this one https://www.amazon.com/Cllena-Automatic-Converter-Regulator-Waterproof/dp/B08KZRZNCQ/ref=sr_1_7?crid=3L4YEPKWXZV0N&keywords=25A%2Bstep%2Bup&qid=1675682321&sprefix=25a%2Bstep%2Bup%2B%2Caps%2C101&sr=8-7&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc&th=1 on board the ROV to step-up voltage to 12V. My question is that I am not sure if this plan will work since I feel that some power calculations are not adding up and wanted to see opinions about this idea.
The other more affordable solution I have is to transmit with 48V and step-down to 12V (much cheaper than using thicker wires). my math tells me this plan is more practical but since we already have the step-up module I wanted to see if I can use it instead of buying a 48v-12v one.

Just set it up without ROV connected and test supply at vehicle end, what is tether length? 260mts is ok without drop, we are testing ours soon over 1600 mts to see what we get .

Hi @hesham0120,

Your numbers seem to match those from our calculator, so if you have a 12V 20A supply, and you’re expecting 20A@8.9V to be sufficient as the input to your boost converter then it should be ok.

If you’re expecting your ROV load to be 20A@12V then you need to factor in the efficiency of the converter, which is not specified at the link you’ve provided (it just says “up to 95%”). Lower efficiency means you require more current as input to get the same power output, and higher current increases the voltage drop through the cable.

Higher tether voltage reduces tether inefficiencies, but may have additional conversion inefficiencies, so there’s a tradeoff involved. You’ll also want to consider things like

• cost (of the tether and converter(s))
• tether flexibility and drag
• safety (there are additional safety concerns as the voltage increases, especially if your vehicle is co-operating with humans submerged in salty water)