If your EUC battery gets just a little wet and still works, why replace it?

[RagingGrandpa]

This is why! 
 

A local friend got caught in a rainstorm, while riding his Gotway RS. 
He tried using a trash bag to cover his EUC, and kept riding. 
Later he noticed that his bag was catching spray from the EUC, and funneling the water into the shell
He took the EUC home and opened it, and found splashes of water near the battery packs. 
To be cautious, he un-wrapped the heat shrink covers from the packs, and inspected for water evidence inside. 
Inside one pack, he found some wet surfaces, but no significant volume of water.

Smartly, he replaced that battery pack with a new one.

And he gave the damp pack to me, for teardown, inspection, and disposal  

While there was no obvious damage visible with the cells and BMS still assembled, 
hiding from view, the PCB and 4 cells had begun substantially corroding. 

The worst of the corrosion was underneath the cell wrap insulator disc, which is quite impossible to see until removing the weld strips.

A replacement pack is expensive, but if you know water got in, ask yourself: how much would it cost to replace the contents of just one room destroyed by smoke damage? Almost always the answer is: many times the cost of one pack. 

Hopefully this reminder will help keep cheap bastards like me in the right mindset, when facing the inevitable "water got in" topics of PMD repair. 

Edited December 11, 2023 by RagingGrandpa
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[Rawnei]

Good catch, the image links doesn't seem to be working for me.

[Rawnei]

Seems you fixed the images!

Do how does the moisture get through the wrapping?

[Funky]

But how does the water get into sealed pack?  Condensation? 

I have been riding VERY. VERY hard rainstorms many times over 3 years. In fall almost every second day in some kind of rain. Also winter riding wheel well gets packed full of snow and at room temp it slowly melts away over 4-6hrs every day, 2 times per day (Workplace/Home).

By your logic i would need to replace my battery pack on weekly bases.  If that's the case, ill take one big fire in maybe 1-2 years then - Cheaper.. As in my little room i only got bed and one closet, PC desk. And right next to my bed i have my D.I.Y "Hot-Box" fireproof storage.

Edited December 11, 2023 by Funky

[Rawnei]

4 minutes ago, Funky said:

But how does the water get into sealed pack?  Condensation? 

I have been riding VERY. VERY hard rainstorm many times over 3 years. In fall almost every second day in some kind of rain. Also winter riding wheel well get packed full of snow and at room temp it slowly melts away over 4-6hrs every day, 2 times per day (Workplace/Home).

By your logic i would need to replace my battery pack on weekly bases.  If that's the case, ill take one big fire in maybe 1-2 years then - Cheaper.. As in my little room i only got bed and one closet, PC desk. And right next to my bed i have my D.I.Y "Hot-Box" fireproof storage.

Just some rain and a rainstorm is two quite different things plus the RS19 isn't very water resistant overall.

Buy I also wonder how the water gets into the actual pack, poor silicone seal? Water somehow trickling in via the cable?

[Funky]

Just now, Rawnei said:

Just some rain and a rainstorm is two quite different things plus the RS19 isn't very water resistant overall.

Buy I also wonder how the water gets into the actual pack, poor silicone seal? Water somehow trickling in via the cable?

I'm talking about those rains, where you need to ride only 1-3 minutes and you have MOIST undies..

Still RS pack should be wrapped/sealed..?

[RagingGrandpa]

17 minutes ago, Rawnei said:

Do how does the moisture get through the wrapping?

In most EUC's, the packs are mounted against hard plastic panels using foam tape. Vibration causes fretting against the hard plastic, and wears through the pack's thin heatshrink cover... a very common occurrence, from my experience servicing high-mileage EUC's.

I think less than a teaspoon of water wicked its way into this pack... but it was enough to cause damage.

 

7 minutes ago, Funky said:

I'm talking about those rains, where you need to ride only 1-3 minutes

I agree. When in doubt, open the EUC side-cover and check for droplets. Usually there are none, after brief rains.

(This RS was ridden for an hour in rain, with a false sense of security because of the shower-cap bag.) 
 

Edited December 11, 2023 by RagingGrandpa

[Rawnei]

3 minutes ago, RagingGrandpa said:

(This RS was ridden for an hour in rain, with a false sense of security because of the shower-cap bag.) 

My guess is that a lot of people who use a rain cap that their primary concern is to protect the motherboard and don't even think about possible water intrusion in the packs.

[Funky]

9 minutes ago, RagingGrandpa said:

I agree. When in doubt, open the EUC side-cover and check for droplets. Usually there are none, after brief rains.

(This RS was ridden for an hour in rain, with a false sense of security because of the shower-cap bag.) 

When i do tires changes - i normally check for water ingress signs. Haven't seen any. Only some sand/dust.. +I also use that backpack cover over wheel while riding in rain. Heck i even use it in snow storms.. As snow can be rushed in true speaker grills.

I should probably tape the speaker grills shut. Then only place water could maybe get past is the power button itself. As for alarms.. I can hear the very quiet EUC world beeps with helmet on. Meaning i would 100% hear loud beeps/voice alarm anyways with taped speaker holes.

Edited December 11, 2023 by Funky

[Funky]

13 minutes ago, RagingGrandpa said:

In most EUC's, the packs are mounted against hard plastic panels using foam tape. Vibration causes fretting against the hard plastic, and wears through the pack's thin heatshrink cover... an extremely common occurrence, from my experience servicing high-mileage EUC's.

Manufacturers should start 2/3 layer wrapping them then. Or users could simply add some layers of duct tape at backside of packs.. (Before the pack "wears" true.)

Edited December 11, 2023 by Funky

[RagingGrandpa]

14 minutes ago, Rawnei said:

a lot of people who use a rain cap that their primary concern is to protect the motherboard

Bear in mind, this was an unlucky situation with the garbage bag folded in a way that trapped a pocket of water inside... 

Rain caps are good, just take care how you position them. 
 

6 minutes ago, Funky said:

Manufacturers should start 2/3 layer wrapping

Modern EUC's improve this in various ways, compared to the old MSupers:

• Inmotion: Encapsulating ("potting") the entire pack.
• Veteran/Leaperkim: mounting and gluing sealing walls to the rigid housing of the EUC shell, trapping the pack inside. (Not relying on shrinkwrap.)
• GW/Begod and Kingsong: rigid battery cases with sealed endcaps. Some caps seal well, others not so well...
   

Edited December 11, 2023 by RagingGrandpa

[Funky]

9 minutes ago, RagingGrandpa said:

 

• GW/Begod and Kingsong: rigid battery cases with sealed endcaps. Some caps seal well, others not so well...
   

Yee S22 is a joke.. Not even wrapped packs. (At least at start they where not. Don't know if they ever fixed that dumb mistake.)

[null]

Thank you for bringing this up. 
People forget there is about as much water spraying under the EUC as there can fall rain from the top.

1 hour ago, Rawnei said:

My guess is that a lot of people who use a rain cap that their primary concern is to protect the motherboard and don't even think about possible water intrusion in the packs.

Indeed. If I had to choose I'd much rather take a cutout from a dead motherboard than a battery fire. By far.

I got a Commander pro recently (a bargain) but the battery weather sealing really bugs me: the packs are fastened to the outer metal shell with plastic casings. As water can spray up to (and rain down to) the joints, the EUC fire safety depends largely on that joint keeping water out. As nobody have opened these packs, we dont know if they are properly sealed. What I -do- know is that @EMA got a BMS alarm beeping after riding in heavy rain, which is not a good indicator.

I'm thinking of sealing the joints with generous amounts of silicone (If nobody see an objection) maybe leaving out a part at the bottom as an exit.

Edited December 11, 2023 by null

[Rawnei]

7 hours ago, Funky said:

Yee S22 is a joke.. Not even wrapped packs. (At least at start they where not. Don't know if they ever fixed that dumb mistake.)

Sure, they're not, but they have very good exterior protection with thick rubber gaskets, I have ridden in the worst condition and this is my second winter riding the S22 as a dedicated winter wheel, no moisture gets inside and so far I haven't heard of a single case of it happening unless someone actually dropped the wheel in a river.

[Funky]

5 hours ago, Rawnei said:

Sure, they're not, but they have very good exterior protection with thick rubber gaskets, I have ridden in the worst condition and this is my second winter riding the S22 as a dedicated winter wheel, no moisture gets inside and so far I haven't heard of a single case of it happening unless someone actually dropped the wheel in a river.

Still.. It would have been WAY WAY WAY WAY WAY WAY WAY WAY WAY WAY.... better, if it had them wrapped also. And everyone in world would agree on that.

Rubber gaskets. If i had that wheel - i would silicone VERY thickly all around the gasket and would add another layer of silicone at both ends. So battery would be siliconed shut. Heck i would even put it in very thick plastic bag, before siliconing it shut. D.I.Y wrap it. 

Would also throw some moisture absorbing baggies in there.. (Just in case.)  

Edited December 12, 2023 by Funky

[alcatraz]

I have zero proof but isn't there a chance that such corrosion happens simply from the cells heating and cooling? The packs may be sealed but even the slightest moisture can condensate. Heating and cooling also acts as a slow air pump slowly moving air(+moisture) in and out of the pack.

I find it interesting that you found it around the positive poles alone. This indicates to me that the cells were ridden hot. Why? Because the positive pole has the least amount of cooling and thus would get hotter than the rest of the cell. Maybe that's why the moisture converged on that location with the greatest temperature delta.

I saw corrosion on my V8 pack but none of it was near the positive poles. It was all on the outer casing (negative). Like it had been stored in a humid environment for a long time.

[alcatraz]

Question: Can corrosion lead to catastrophic failures?

I'm thinking eventually yes, but not from the corrosion alone. But from the cell slowly self discharging past 2.5v and still being ridden. 

Meaning, if your cells are balanced, the corrosion shouldn't be a fire hazard. This is just a hypothesis.

Once the corrosion has started it's only a matter of time before the cell will start to accelerate its self discharge so it's a compromised pack for sure. But a fire hazard before voltages become severely unbalanced? I doubt it.

[RagingGrandpa]

7 hours ago, alcatraz said:

isn't there a chance that such corrosion happens simply from the cells heating and cooling?
The packs may be sealed but even the slightest moisture can condensate.

the moisture converged on that location with the greatest temperature delta.

Surface condensation only occurs when an object is cooler than the surrounding air. Not warmer. 

I think it's quite unlikely in an EUC's use case, that the pack is cooler than the dew point. 

Charging it releases heat; discharging it releases heat; and EUC's are stored indoors, so never very cold to begin with. 

If you don't have condensation forming on the exposed aluminum of your rim and motor, you can be confident it's not happening in the pack. 

Mod edit: further discussion of condensation has been split to a separate topic: https://forum.electricunicycle.org/topic/34865-can-water-condense-inside-an-euc-and-damage-it-split/

 

7 hours ago, alcatraz said:

interesting that you found (corrosion) around the positive poles alone

There was a trace of surface rust a few cell bottoms also...

The cell-top features include small cavities under the wrap and around the pressure relief, and these nooks and crannies retain water and resist evaporation more than exposed spots. 
 

7 hours ago, alcatraz said:

This indicates to me that the cells were ridden hot.

Well, not hotter than the 70°C alarm temperature (the alarm was never heard, during riding). 

This was a Michigan-climate EUC: summer temperatures do reach 100°F, but typical riding is 40°F-80°F ambient. Not desert conditions. 
 

7 hours ago, alcatraz said:

Question: Can corrosion lead to catastrophic failures?

Absolutely!

It is the only explanation for the numerous reports of submerged EUC's that caught fire during storage afterwards.

On 12/8/2020 at 1:13 PM, EUC Custom Power-Pads said:

16X battery after it had been in the river for a day. The battery went up in flames a few days later.

 

Edited December 12, 2023 by RagingGrandpa

[alcatraz]

Thanks! You make the forum a really intresting place, sir!

It would be really interesting to do a submerge test and monitor the voltages over the next few days while keeping the cells wet (heatshrink unopened). Another test with a corroded submerged pack that later has been dried would be super interesting.

The greatest temp delta would mean the pump effect is greater there. Like you said, water evaporates where it's hot and condensates where it's cold. The hotter it gets in one spot, the more condensation will be created at the cold spots. That's what I'm thinking. Is it crazy?

Sealed packs can corrode so something is going on apart from submersion. Moisture is passing through the seal or there's moisture already in there. 

Edited December 13, 2023 by alcatraz

[RagingGrandpa]

12 hours ago, alcatraz said:

Sealed packs can corrode

The cells contain a liquid electrolyte... which becomes extremely corrosive (HF) when exposed to atmosphere. 

Quote

https://www.sciencedirect.com/science/article/pii/S1388248121001727
The state-of-the-art electrolyte has been LiPF₆ salt in organic carbonate solvents. LiPF₆ has been chosen due to its high conductivity in solution and good safety properties. It is also extremely sensitive to moisture, which produces HF.

So if cells leak due to manufacturing defects (of the cell-top crimp seal), or due to a burst pressure relief (over-temperature), you'll have acid vapors (HF) eating more things in your pack. 

 

(To be clear: the pack I tore down had visible water droplets inside... water started my problem, not electrolyte.)

[alcatraz]

Ok so when the external corrosion releases the electrolyte, then it's all downhill from there. 

Is that perhaps what happened around the pos poles?

It makes sense now that no cell should be mounted upside down. I bet those positive poles were all the second layer of cells with water running down the cells above. 

Imagine if the positive ends could be galvanised or stainless so that the much larger casing could act as the sacrificial element and keep corrosion away the positive pole for longer.