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  • Battery Water Exposure

    I have a bottle battery. Notice on front says limit water exposure. Does that mean do not use in the rain? It rains a bit in Texas.

  • #2
    It is water resistant, but not so water resistant that it doesn't merit a warning about water exposure. Most of the time if there is a water related issue on a support ticket it's from exposing to seawater, exposing to water with a lot of road salt, or exposing repeatedly to rainfall on a regular basis like storing the bike outside in Portland or some other very rainy city.

    If these issues do come up the most vulnerable points are where the battery makes contact with the cradle and where the charge port is. A lot of this can be protected by using dielectric grease as described on the hardcase documentation (I prefer Permatex 22058 Dielectric grease, several others would work but you need to make sure to get actual dielectric grease and not something like the battery terminal grease they sell at auto parts stores)

    Hardcase documentation

    As to the battery itself if you find yourself in a sudden rainstorm it might make sense to take a grocery bag and put it over top of the bottle battery. There is extra stuff you could do if you want to to make super sure that it is fully waterproofed like opening up the case itself and covering with 3M potting compound, or even just slathering a light coating of dielectric grease on anything electrical (circuit boards, wiring, the spot welds on the battery etc.) course if you ever need to open it back up and do any sort of maintenance on it that would be more difficult if it has grease and it would be impossible if it has potting compound.

    So it's one of those things where it could be good or bad and you need to take that into consideration before doing internal modification, but in any case it's always a good idea to grease the discharge contacts and charge port. This will prevent oxidation, rust, possible shorts etc. it is a good idea to periodically check these contacts as well. They should look nice and shiny and not caked with any crud or crystallized salt, and the contacts should be making good contact with the cradle and if they are not making good contact you should adjust them in such a way so that they are.

    To put this into perspective there's a big difference between the kind of person that
    • occasionally uses his ebike in rain and snow but takes a few precautionary steps
    • rides his ebike through rain and salty winter roads all the time but takes no precautionary steps
    • rides his ebike through deep tidal pools at the beach

    It's the difference between having your battery work for years, having your battery work for one year, or having your battery work for one day.

    The biggest issue is always going to be salt, contaminants, ocean water. This changes the resistance when saltwater is sitting on an electrical contact, and the electricity is going to take the path of least resistance. If enough salt is present that means it will short out because it will take that low resistance path from negative to positive.

    The grease helps prevent this from happening, as well as preventing long-term corrosion that might turn electrical contacts into a high resistance connection. In a high resistance connection where you want the discharge contacts to be discharging, it's going to get hot and potentially melt the connectors because the electricity is bottlenecking at that point, which you wouldn't want either. Typically this is what regular water does over time if it's allowed to sit on unprotected electrical contacts.

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