Help! Woosh bike battery, need help with mounting frog battery, somewhere somehow, safely

[Scruffydroid]

@Rileyy

Hey Riley, what was the end result here? Too many people come along for help, people give of their time, knowledge & experience and the OP's disappear like tumbleweeds into the desert...

 

[Woosh]

Riley gave up the kit and got a refund.

 

[Scruffydroid]

All's the pity. I hope that she gets a suitable bike to electrify, as opposed to a jump bike this time?

 

[Woosh]

there is a need for batteries that suit small frames.
The problem is small batteries usually have small capacity and not suitable for strong motors.

 

[FJC71]

there is a need for batteries that suit small frames.
The problem is small batteries usually have small capacity and not suitable for strong motors.

For small frames

There are a number of problems with the current offerings, the first is that most batteries on sale dont use the most energy dense cell options.

Most batteries are only offered in standard cases which usually dont fit and even if you can get one to fit it runs up against the first issue.

Kit suppliers are often too restrictive in battery choice or worse insist you take their offering. No matter how good the motor price or service etc you have to walk away.

For this type of project its better to separate the battery from the kit altogether, the battery s almost a separate project in itself. In my opinion you have to get creative and probably spend more money and most of all time to work out how it will all work.

As for this project the best solution might be a different bike but there would be no guarantee that another that fitted the poster would have been any better.

This project all hung on getting a rack to fit, that was a challenge it maybe could be done but it wouldn't be easy and likely too expensive for the budget anyway.

 

[Woosh]

There are a number of problems with the current offerings, the first is that most batteries on sale don't use the most energy dense cell options.

it's not true that most batteries on sale with kits don't use the most energy dense cells. Her kit can be bought with 17.5AH HL battery which costs £100 more than the same with 13AH battery.
The 17.5AH HL battery uses the Samsung INR18650-35E cells, same with the best out there in Bosch bikes.
If you are talking about small sized batteries: small battery means small volume, small volume means fewer cells, fewer cells means less maximum current draw.

Kit suppliers are often too restrictive in battery choice or worse insist you take their offering. No matter how good the motor price or service etc you have to walk away.

only partially true. Riley was offered the choice of buying her battery elsewhere but declined.
The fundamental problem with fitting a smallish battery like the small frog (223mm x 120mm x 134mm) is of fitting.
You need at least 120mm clearance between the saddle and the rear mudguard to fit the battery to the seat post below the saddle.
Riley's saddle has to be set so low that she could not even have that space on her bike.

 

[Nealh]

Not always Tony if one uses 20 or 25a rated cells, then one can have a 25 - 30 mile range light 2 parallel celled battery.

 

[Woosh]

I am scared of cells with high discharge rate. They may increase the fire risk.

 

[FJC71]

Woosh
it's not true that most batteries on sale with kits don't use the most energy dense cells. Her kit can be bought with 17.5AH HL battery which costs £100 more than the same with 13AH battery.

Oh I'm afraid that's not what I found when I was in the market. I was looking for a 48v battery in the smallest case available. There were numerous batteries available with lower densities, larger cases and less than optimal sizes. There were few sellers, for small case batteries around 14ah, they usually didnt have stock worst of all really difficult to get detail information. There was a bit more availability for 36v but still not great.

The 17.5AH HL battery uses the Samsung INR18650-35E cells

As said 36v had better availability but again most suppliers seem to focus on lower density cells and thats where the availability was. It might have improved a bit by now though,

After a while I gave up on down tube cases, mainly because of lack of information from suppliers more than the availability of better cells. Also even in the smallest cases the suspicion was that size of the packs overall were still larger than the equivalent Bosch (even using similar or sometimes better cells) but that info even if true was of no real practical use other than to say it was possible.

Woosh
The fundamental problem with fitting a smallish battery like the small frog (223mm x 120mm x 134mm) is of fitting.

The size did seem adequate for the use proposed. However it looked less than Ideal in terms of the configuration of the bracket. I did think if you could sort out a bracket the general shape might lend itself to being a handle bar mounted battery.

Woosh
You need at least 120mm clearance between the saddle and the rear mudguard to fit the battery to the seat post below the saddle.
Riley's saddle has to be set so low that she could not even have that space on her bike

I presume you mean below the saddle to the top of the mudguard wheel. The simple answer is dont try and put the battery under the saddle do something like this mount to the rear of the saddle.

This particular rack probably wouldnt work as the geometry is less than Ideal for a small frame and you have to imagine the bag as a battery but it illustrates what I mean. I would prefer a conventional rack. You might need geometry similar to the Topeak small frame beam rack to work as well.

 

[Woosh]

The size did seem adequate for the use proposed. However it looked less than Ideal in terms of the configuration of the bracket. I did think if you could sort out a bracket the general shape might lend itself to being a handle bar mounted battery.

The U-shape bracket can be rotated 90 degrees, so you can mount the small frog battery with the L side vertical or horizontal for smaller riders.
To mount the small frog to the seat tube, you fit a seat post clamp with rack mounts to the seat tube then bolt to the U-shape bracket to the rack mounts using 2 x M6 bolts.
It's quite easy to fit it under the saddle if it were not for Riley's small stature.

 

[JayDG]

Not sure If I spoke to You over the phone or in email I spoke to 2 different guys?
But I did send photos in the email multiple times and no one told me it's a bad idea, I didn't know. until I was told it could literally explode.
And how would I go with mounting the mount You've provided on that rack?
I think I'm going to go with solution that overlander suggested. This front rack doesn't look like I could mount anything on it, maybe with a bad but that's another cost.

When you try again.....my bike triangle was also too small, and I already had a seat-post rack like the one you found on Amazon.
So I drilled holes in it to mount the battery base (had to use some washers as spacers, to clear the end of the rack). And it works fine.

 

[Woosh]

Jay, Riley does not have the kit any more.
She sent it back for a refund.

 

[JayDG]

Jay, Riley does not have the kit any more.
She sent it back for a refund.

I saw. But in case she decides to try again to electrify a bike. Or anyone else who has a small triangled bike and the seat down low.