Load tester for Piranna Li batteries

[sunnyboy]

Has anyone seen or heard of such a device? I think my battery is losing it's 'punch', and wonder if there's a way to test it's overall capacity, much the way we used to be able to test the SLA batteries in Gavin scooters.

I envision two ideal devices: 1. Something from Dive-Xtras that would log to a computer. Even more ideal, not too expensive.

Ideal device 2: An arduino-based DIY solution that can handle the high current / higher voltage of modern PPV Li batteries and also logs to a computer.

 

[Jack Hammer]

A watts up meter can give you pretty basic info. A data logger, like the Eagle Tree, will give you more details and graphs but costs quite a bit more.

Also, in case you haven't already, make sure nothing is caught up around your prop shaft. That little extra drag makes a big difference in performance.

 

[_Ralph]

You can get the data cable and pull off the data from the last xyz samples of the system. Also used for customizing functions like 'gearing'


_R

 

[tbone1004]

build one the same way we built the old ones and optimize for the voltage/draw of the internal motor.
put a watts up or an eagle tree monitor on there, and it will tell you everything you need to know

 

[sunnyboy]

Related question: anyone have an idea how long a Piranna 1 battery lasts? Sure, it was cold today, but I'm the same diver in the same gear as always, and it's now 'downshifting' at 30 min and dying at 50. I used to be able to do this entire dive (over 60 min) and not have it die.

 

[tbone1004]

@sunnyboy quoted max is 50 min at max throttle, on the website... Age kills cells, storing at full charge kills cells, discharging below 20% kills cells *20% likely when the downshift occurs*, probably have a couple bad cells in the back

Piranha P1 Dive Scooter.. – Dive Xtras

 

[sunnyboy]

I've never run max throttle. Mine's on factory default settings, so it starts at '3' and stays there. As for discharge, the P1 circuits manage discharge so you never kill the pack. LIkewise I'm using their charger so it's not overcharged. Basically, this has been well kept and cared for since bought.

I talked to Dive Xtras yesterday and it's simply my battery is getting older. I'm liking the new power tool battery mainly because you can just swap out a poorly performing battery anytime.

 

[sunnyboy]

I plugged in my P1 programmer today to view the data logs. It turns out my P1 was set to 'Cuda defaults', meaning the cut-off voltage was 35V instead of 30V. Big difference!

I also downloaded the last dive log and can see battery performance was not that bad; basically a linear decline from 40V to 35V in about 50min. With proper settings I should be able to go longer without any other change.

 

[tbone1004]

it's not overcharging, it's storing at full charge. I.e. never charge your dpv after you finish the dive. Charge it the night before you dive it.
over-discharging is still possible with the electronics depending on what the cutoff threshold is. Anything less than 20% damages cycle life, and I can guarantee you it discharges under 20%. Probably downshifts at or around 20%

I would still research cutoff voltages for whatever voltage that pack is and find out what 20% equates to. Have it hard cut-off at that point if you want to maximize battery longevity