We have a custom built ROV powered by two 22.2V batteries(28Ah). These are neither daisy-chained nor parallel-wired, simply split up to supply different things. We have one PSM connected to the navigator, but want to add another to be able to measure both batteries. Can we use a serial-port on the Navigator?
I tried finding topics on this, but could find any. I truly don´t believe that no-one else has connected two PSMs earlier???
The setup is based on BR-products.
Original electronics enclosure (Raspberry Pi4 & Navigator)
6xT500 thrusters
2x22.2V batteries
5xBasic ESC
1xESC 500
4 daisy-chained lumen subsea lights
We’re also having a slight issue with flickering lights. They tend to dim a bit when multiple thrusters are active, even on 50% gain and reduced PWM values(1840ms). We haven’t checked for shorted stators, as all of the thrusters are new. Could this be an overload issue? I tried finding some live numbers in the MAVlink inspector, but didn’t really find what I was looking for.
Hi @Erlingns95 -
The PSM does not use a serial port! The signals are analog voltages that are read by the ADC on the Navigator. It may technically be possible to setup a second PSM input using the ADC breakouts available on the Navigator, but would likely require customization of the ArduSub firmware (or the use of a Lua script!)
If your two batteries are not connected at all, you won’t be able to take measurements from the PSM, as they will not share a ground reference witht he Navigator.
Your flickering lights could be related to electrical noise, particularly due to you running two separate batteries. Is the ground terminal of both batteries linked together? If not, doing so may help, but ideally you would charge the batteries equally and run in parallel if possible…
Parallel wiring is probably the better solution, we’ve just been too ‘scared’ to try. Is there anywhere we can find a guide on how to do it with the BR batteries? I’m noticing some brands describe the process and the importance of each step a bit different.
Can we use the splitter cable meant for the blueboat?
Also, do do you know where I could read a live current pull(ardusub)?
Hi @Erlingns95 -
Connecting batteries in parallel is simple! The only thing to watch out for, as the BlueBoat documentation notes, is ensuring the batteries are within 0.1V of each other before connecting in parallel, so large currents don’t flow between them.
The BlueBoat cable is likely too large to go through WetLink Penetrators… But a bunch of our standard ROV power cables could do the trick?
I’m not 100% sure what you mean by “live current pull” - you can display the amps being consumed by the vehicle in QGroundControl and Cockpit by showing the relevant parameter - this information is already present in both software alongside the battery voltage. You can configure Cockpit’s very generic indicator to display current like this:
In QgroundControl, unlock the center bottom black telmetry bar, and edit or add a value, selecting Battery from the first down, and current from the next.
Don´t worry about my “current pull”, found what I was looking for in the MAVlink inspector:P
Out of curiosity, I don´t suppose you have a charger meant for two parallel-wired 6S batteries (22.2V 12S)? Using this setup would require us to charge them separately, am I right?
We would also like to use the standard ROV power cables, but I´m afraid we don’t have enough blank penetrators availible.
Hi @Erlingns95
The H6 charger can be used to charge two 6S batteries in parallel, however the balance connectors of both batteries must be connected in parallel to the charger as well. If this isn’t possible, they must be charged individually (also with balance connection made.)
Doesn’t really make sense to me. Is it still able to ‘supervise’ each and every individual cell if you parallel-wire them? Or are you kind of fooling the H6 to let you charge without 12 separate cell counts?
Hi @Erlingns95 -
It is important in any battery system that ALL cells are equalized. Thus, when charging in parallel the balance connectors are also connected in parallel, and the charger is balancing all cells to be at the same voltage. Two cells wires in parallel have the same voltage after all - and if they didn’t initially, they will equalize themselves very quickly - hence the requirement that the batteries are charged to within ~0.1V of each other before connecting.
