I have a trip coming up where I will be spending several weeks at sea and am looking to take my Trident
We do have a generator on board but rather than having to fire that up for a few hours just to charge up the Trident after use I am thinking about getting a way of using the standard 12V (Deep Cycle Gel Cell standard boat) “house” batteries (yes I know you can get inverters for 12VDC to 230VAC but then throttling this back down to 12VDC for charging seams wasteful – we don’t do this for any other electrical gear [laptops and alike which just have a DC to DC adapter eg this or underwater lighting] )
Given the Charger supplied with the Trident is a Shenzhen Modiary 12.6V 4A output I am assuming that inside the Trident is a Battery Management System (BMS) chip/card for charging the (I assume) 3S Li-ion batteries inside the unit.
I have measured the Voltage on a charged Trident’s tether connection 3 pins (looking from the rear) (and also on the charger) it looks like the 6 O’clock pin is the neutral and the 10 O’clock pin is the positive (from the charger) and I (assume) the 2 O’clock pin is the feed of voltage back up the tether (12.31VDC measured on the ROV).
Given this (I assume) the Shenzhen Modiary 12.6V 4A (approx. 50W) Charger is “semi” smart doing something like a programmed auto 4 stages (Ip-Im-Um-cutoff) charging process
Stage 1 Slow start, precharge function for deeply discharged packs (pre-charge small current)
Stage 2 Bulk charge stage. 3.3 amps is applied to the battery until the voltage rises to 12.6 volts (will give bulk current charging (up to 50W))
Stage 3 Constant voltage state until the charge current falls to 400mA
Stage 4 The charger turns off
Given this with a fairly standard LiPO charger that accepts a DC input like this (or generic) set up in the Lithium Battery mode (ie no balance cable to the charger and assuming the balancing is done onboard the ROV by the assumed BMS on the unit) for 3S and 4A (not sure of batteries for 1C charging but assuming from the charger 4A) and then cobble together a way to pin this into the Trident
Am I crazy or is this in the ball park for an off grid charging system