Big kudos to Jon/Logic - I fried my Genesis, a cautionary tale

[stuartv]

Short version:

I fried my Genesis 2.1 using an aftermarket charger. I shipped the tube and warp core to Jon at Logic. He received it yesterday and it is repaired - for a reasonable price - and on its way back to me today.

Long version:

I got a Satiator 75V battery charger from Grin Technologies. I like it because it is "smart" and programmable. I have different profiles setup for charging the scooter while stored versus just before a dive.

The standard charger from Logic charges the Genesis at a max of 4 amps of current. I thought I would be clever and create a charging profile in the Satiator to charge the scooter at 5A, in case I was really in a hurry. I did that and tested it and found that 5A would trip the internal safeties and stop charging. But, feeding it 4.9A worked. Little did I know....

That was all when I had basically just gotten my Genesis. Once I was done messing around with that stuff, it was mostly just sitting, as I don't get to dive with a scooter all that often. I used the iPhone BMS app to check the battery charge level periodically and noticed that it seemed to be running down and need a top-up charge more often that I was expecting, but I didn't really have a base of experience to judge it, so I just put it on charge about once a month and didn't worry about it.

About a month ago, I went on a dive boat and took my Genesis. I again thought I was being smart and did not put the charging connector cover on when I loaded the scooter on the boat. I keep it clipped to the bolt snap on the tow cord, so I figured I would just put the cover on right before I splashed. The boat was small and seas were choppy. We got sprayed a lot on the way out. At one point on the ride out, for some reason I don't remember, I touched the charging pins. They were wet and my fingers were wet. I got a serious zap. I didn't know any better and just thought "well, don't do that again."

Of course, I forgot to install the charging cover before I splashed. But, as the crew was handing me the scooter down from the boat, I did remember. So, I put it on right there floating on the surface. The charging pins were exposed to seawater for maybe 30 seconds. As I put the cover on, I noticed that there were a lot of bubbles coming from the pins. Not bubbles from a leak. Bubbles like you see from electrolysis. Okay. Well, glad I remembered to put the cover on right at the start! The scooter worked fine all day. I removed the cover again after we were back at the dock and then rinsed the scooter really well at home before putting it back in the garage.

Cue a month later and I go to charge it before leaving last week on a trip. It wouldn't charge. One of the charging pins was actually burned down to so thin that it was no longer making contact inside the charger cable.

I shipped the tube with warp core to Jon and got the verdict yesterday.

Apparently, when I put it on the charger at 4.9A (for only 5 - 10 minutes), the isolation diode got hot enough to melt the solder around it, which flowed together and created a short. Jon removed the diode and said it still tested fine.

That short (apparently) caused the charging relays to be powered up all the time, which is why the scooter was discharging in storage so rapidly. And also why I got zapped by the pins when I touched them with my wet finger, and why there were so many bubbles coming from the pins when I put it in seawater with the cover off. There's not supposed to be high voltage to whatever pin I touched except when the charger is connected.

The repair was to replace the charging connector on the nose, unshort the shorted solder, replace the diode (just to be sure), an hour of labor, and shipping to get it back to me. The cost of my "cleverness" was very reasonable, and I cannot say enough good things about Jon getting it turned around in 1 day!

So, learn from my mistake, please. Use the charger that came with the Genesis. Or at least don't charge it at more than 4A, and make sure you are using a good quality charger (which, in my case, I am).

And be glad you have a Genesis (if you do). I cannot imagine getting a repair like this done by any other manufacturer in remotely this short a time period. And probably not nearly as cheaply, either. I shipped it from FL last Tuesday. 4 business days to get there. 1 day turnaround. You really can NOT ask for better than that!

 

[BoltSnap]

Great to see you back on SB after such long absence even if you are making such terrible mistakes

 

[Jona Silverstein]

So uh maybe heed @Jon Nellis recommended limits and use the recommended charger...

 

[Rick Brant]

I'm glad you posted this. When I read about some of your DPV "experiments" my first thought was that this is how liveaboard fires start, somebody with minimal experience trying to outsmart a system using Chinese technology. Hopefully your post will dis-inspire someone.

 

[Whitrzac]

I'm calling BS on the charge rate difference. 0.9a difference is not going to melt solder or overheat anything. If it was it would fail frequently from just the differences in charger outputs and inrush currents.

Saltwater messed it up, no questions asked.

 

[stuartv]

I'm calling BS on the charge rate difference. 0.9a difference is not going to melt solder or overheat anything. If it was it would fail frequently from just the differences in charger outputs and inrush currents.

Saltwater messed it up, no questions asked.

I can only relay what Jon said. Well, and that it sounded reasonable to me. Which was, before he actually received my scooter to examine:

There should not be voltage on that pin (#2) when not charging. It is air gapped with a relay. Your picture says there is voltage and current available at the #2 pin, which mean one or both of your charge relays are stuck closed and/or the isolation diode is blown.

So, I don't think it was the saltwater, per se. That is just what burnt the pin after the isolation diode was shorted.

After he received it, he said this:

The diode blocking voltage from back powering the charge relays was shorted. I cut off the conformal coating and removed it. Testing the diode after removal showed it still works, so the solder under the surface had to have created the short. It gets fairly hot when charging and charging at a higher current increases power relative to I^2. The conformal coating traps the heat as well, so charging at 5 amps is the most likely culprit causing the solder to melt and flow.

I think your comment about differences in charger outputs and inrush currents relates to this as well. I.e. the charger Jon supplies is specifically designed to not have a damaging inrush spike. And it limits charging current to just over 4A (according to monitoring of the BMS from the app). Other chargers are very much not recommended. Ones that are used probably don't usually run at over 4A, so even if you're using one you're probably not in damage of heat damage. But, if you're not using a "good" one, you could be rolling the dice on having inrush spikes damage the charging relays.

And, lastly, I emailed Grin (maker of the Satiator charger) and they said this:

I can speak to the actual inrush current that is present with the Satiator itself turns on. Unless the satiator has a blown output stage mosfets, then the inrush current is in fact almost nothing since the output of the satiator has a mosfet in series specifically to prevent any current flow into the output caps on first connection.

Grin's response made me feel good in two ways. One, that they understood the issue and seem to have designed specifically to prevent any problems from an inrush spike, and, two, that they received my email about my problem and responded quickly with a response that actually SOUNDS knowledgeable and accurate. Not just some front-line tech saying "oh, our charger wouldn't do that."

Believe it or don't. But, I am satisfied with the conclusion that my charger, at 5 amps, is what fried the isolation diode and, as long as I use the factory charger, I shouldn't have any more problems. If I use the Satiator charger and limit it to 4A, I also probably wouldn't have a problem.