We’re struggling to find a Low Voltage Cut-Off (LVC) for our batteries, specifically for our lights. We need a LVC that will fit in a 3" tube, preferably with a height of no more than 1.5 inches. Can anyone help point us in the right direction? TIA!
Hi @LiveForLiving,
It’s hard to give much advice without more information about your system.
If you’re using an ArduSub flight controller board with power monitoring then you could potentially create a Lua script that disables the lights outputs when your desired voltage threshold is reached (perhaps with some leeway for sudden drops due to thruster engagement), and/or you could use a power level failsafe to disarm or return to the surface. In that case there would be no additional hardware required beyond what’s already in your vehicle.
Hi @LiveForLiving -
Maybe you’re looking for a simple circuit to make the battery not over-discharge when supplying your lights, so that no other control connections are required?
Something like this would work for 4S batteries, if wired correctly…
1 Like
Wow Thankyou - I’ve been looking for something like this for ages but couldnt find oen rated for 30A. Is this the same as used in the BR batteries?
Our actual batteries don’t have overdraw protection circuitry built in, and are instead reliant on appropriate management by monitoring through a power meter (and potentially measuring the temperature via the built in thermistor).
2 Likes
Hi @BillyBudd -
30A is not going to be enough to run an ROV! It would trip even at 50% gain…
1 Like
Thanks guys - it was more the balance function I was after as always wanted to build my own battery for the BlueROV but can never find anything that matches the requirements. As Tony advises 30A is nowhere near enough so presumably it has to be around 100-150A? I’ve never seen anything like this and wondered what you use at BR? No worries if its confidential but thought I’d ask anyway!
Hi @BillyBudd -
We don’t use protection with our batteries - a circuit to do so and allow 100-150 amps is not easily / cheaply feasible!
Also, if at low battery and needing to recover an ROV, it can be better to over-discharge and kill the battery, but still get the unit back vs. losing the whole thing!
1 Like
Sounds sensible and good to know that there is a reason I cant find a protection board for that current draw! Would the BMS board you provided a link be suitable if I built my own battery using a 4S array of 18650 LiPos though?
Hi @BillyBudd -
For les than 30A discharge, and following their wiring diagrams, yes that should be fine to make a pack with!
1 Like