Downtube battery on a step-through frame - is it safe?

[tpw]

Bought this frame to build a new bike, but now it's here I've started to worry about whether it's a good idea to mount the battery on the downtube?

A step through frame is already less structurally sound than a diamond frame, and electric bikes with step through frames always seem to have the battery on a rack at the back. I guess this could be because it could get in the way when mounting the bike or something..

Has anyone done this and had it go ok? I found this thread, don't know whether he went through with it in the end

 

[Benjahmin]

If you want/need a step through frame, why would you clog it up with a frame mounted battery? My wifes step through has a water bottle mounted on the saddle down tube, it is always getting kicked as she steps through. A battery would be far more of a restriction. I'm not sure there would be a problem with rivnuts ( the frames thicker anyway) but your size 10's could be a big issue.

 

[Fordulike]

Don't worry about the structural integrity of a step through frame. They've been designed to cope with the loads they endure. It's probably got a water bottle mount anyway, so designed to carry a full water bottle there.

The only thing I would be concerned about, is accidentally side kicking the battery when mounting the bike. With a triangle frame, this isn't an issue.

 

[sjpt]

Quite a few step through electrics have the battery on the seat tube: for example the Cube Touring has it in front semi builtin. https://www.cycle-revolution.net/22000/products/2019-cube-touring-hybrid-one-400-step-through-electric-bike-in-black.aspx A lot of more basic older ones had extended seat stays with the battery behind the seat tube,

 

[tpw]

If you want/need a step through frame, why would you clog it up with a frame mounted battery? My wifes step through has a water bottle mounted on the saddle down tube, it is always getting kicked as she steps through. A battery would be far more of a restriction. I'm not sure there would be a problem with rivnuts ( the frames thicker anyway) but your size 10's could be a big issue.

I was using a step through because I wanted to have a rack with quote a tall bag on the bag, so I wouldn't be able to swing my leg over, or have anywhere else to put the battery. If the battery is mounted fairly high up it shouldn't be too much in the way (and I only have size 8's anyway!), but it will definitely be easier than leaning the bike over and trying to thread my foot over a top tube.

Don't worry about the structural integrity of a step through frame. They've been designed to cope with the loads they endure. It's probably got a water bottle mount anyway, so designed to carry a full water bottle there.

The only thing I would be concerned about, is accidentally side kicking the battery when mounting the bike. With a triangle frame, this isn't an issue.

I though the same thing, although even a fairly light battery is 3x the weight of a large water bottle.. The frame I linked has the bottle mounts quite high up anyway, so it should be fairly out of the way.

Quite a few step through electrics have the battery on the seat tube

I did have a look, but it would be too short for my battery.

 

[vfr400]

I think it would help if you show us the actual frame.

The higher you mount the battery, the worse the bike's handling, especially when you aren't on it. The lower the battery, the more likely you are to kick it.

 

[tpw]

I did link it in the original post, but I tried to be all clever and hid it in the word ‘this’, so you may not have noticed it! (It’s here https://www.bike-discount.de/en/buy/cube-elly-cruise-easy-entry-frame-pistachio-n-blue-840128)

I have a hailong case, so it’s sort of long and thin. So even if it is mounted ‘high’ on the downtube, a lot of the weight will be low down, and it will still be a lot lower than a rack mount battery

I’m really not too bothered about kicking it, just about safety and whether the frame can take the weight. It’s basically the only option if I want a big bag on the rear rack anyway

 

[vfr400]

The Hailong battery mount has the problem that the fixings are at the top end, so they never line up with normal bottle fixings; however, it's very convenient for your frame with the high bottle fixings, but it means that you'll get a lot of leverage when you kick the battery, which will rip out the 5mm screws. If you don't have the included potted controller in the battery receiver, you should install an additional 5mm rivnut lower down and drill the battery mount through the aluminium plate to hold the lower end of the battery mount.

 

[Nealh]

Your bike frame is strong as it has a mini gusset forming the triangle at the bottom of the frame.

 

[anotherkiwi]

The kick marks on my bike are all on the seat tube, not the down tube. You should be fine but you could chuck a couple of wheels on, mount the battery and test.