Battery Options

[kernow60]

Hi all
O.K. as some of you are aware it is my intention to buy and fit a mid drive kit to my Diamondback Sync 3.0 MTB, and I've been looking and researching my options kit wise, no problem.

However fitting a battery to my small 16" frame looks like it could be a big problem, being a 16" frame the triangle isn't very big especially with a sloping top tube I have done some measuring and the battery I had in mind which would have been ideal was a Samsung 36v ~ 14.5a/h which is 360L x 82W x 130/110h and there is just no-way it's going fit in there, also another similar Hailong 36v ~ 15a/h is slightly longer by 5mm but only 86mm-h and it's the same scenario.

So my options at the moment are looking like a rack with a battery attached, which I really don't want to do, I'm not keen on the frog type battery either and in any case not sure if I would have enough room for one as the wheels are 27.5" and even with a fair amount of seat tube protruding it's still pretty tight for space.
So I have seen somewhere some pic's of bottle batteries fixed to the top tube which is what I'm sort of favouring at the moment.

Any idea's, comments or advice most welcome please, thank you in advance.........................

 

[soundwave]

put it in a back pack

 

[trex]

this battery is made for a small triangle:

woosh sell a right side pull 11.6AH, so you don't need headroom to take it out:

http://wooshbikes.co.uk/?batteries

 

[kernow60]

OK thanks guys, never thought of the backpack option so I'll keep it in mind for the moment, would still prefer a more permanent fix to the bike to be honest.
And unfortunately the one that trex has so kindly laid out above is still far to big for my triangle.

 

[anotherkiwi]

Welcome to the small triangle club! A bespoke battery enclosure is the route I am taking.

 

[kernow60]

Welcome to the small triangle club! A bespoke battery enclosure is the route I am taking.

Hi
That sound interesting what do you have in mind.???

 

[anotherkiwi]

d8veh has a thread or two where he shows custom made battery boxes.

Measure up your triangle and make a mould to lay up a fibreglass box (I prefer fg/epoxy to polyester). If you are lucky maybe the guts of a HL battery fit inside your triangle it is just the case that is too big. Or have Insat make a custom battery to fit in your case (build the battery box first then ship it to them so that can custom build to fit).

 

[kernow60]

d8veh has a thread or two where he shows custom made battery boxes.

Measure up your triangle and make a mould to lay up a fibreglass box (I prefer fg/epoxy to polyester). If you are lucky maybe the guts of a HL battery fit inside your triangle it is just the case that is too big. Or have Insat make a custom battery to fit in your case (build the battery box first then ship it to them so that can custom build to fit).

Thanks, but to be honest I just want to keep it simple really, even in the end if I have to go for the rear rack mounted battery. I been thinking about it and figure if I can keep it as close as possible to the rear tyre and also as close as possible to the seat tube it should be o.k., well that's the theory anyhow.
I know I have seen pic's somewhere of a bottle type battery mounted on the top-side of the top tube, and my top tube is almost square, well sort of square with rounded corners so I can't see a problem with mounting it on there. I guess one could be zip tied on there to see what it's like, or something the equivalent weight like a s/s flask full of water maybe. ?

 

[anotherkiwi]

Just put a couple of rivnuts and mount it there if you are still able to swing your leg over the rear wheel to mount. Us older chaps like step through frames because, well... you know...

Had I been younger I would have mounted a HL type battery on the top of the frame and it would still be lower than a gents bike as you can see below. But I can squeeze 20 Ah of Lipo into the triangle in a custom made battery box.

 

[kernow60]

Actually I think I will position a tube or s/s flask with a bit of tape or zip ties just to see how it works out, I have a fair amount of room because the top tube as quite a slope to it down toward the seat tube so I could experiment with the position to find place for it. I will try it sometime this week and let you know.

 

[kernow60]

Just found this................

 

[kernow60]

OK I still haven't experimented with a weighted tube of some sort on the top tube, but to be honest looking at the pics I posted above a couple of weeks or so ago I can't really see a problem with it, and am more or less happy to go with it.
O.K. so now having come to terms with the initial outlay of purchasing my Diamondback MTB, I will shortly be buying my mid-position motor and battery, which is going to be almost twice the price of the bike, but still just under a grand which was my target figure in the first place.
One other thing I would like please are some opinions before I make my battery purchase, other than the obvious, what is the difference between the the 36v & the 48v batteries, are there any advantages/disadvantages in going for the higher voltage one, would a 48v battery give more range for example?, are they legal?

Thanks in advance guys for your expert knowledge & opinions.

 

[Alan Quay]

OK I still haven't experimented with a weighted tube of some sort on the top tube, but to be honest looking at the pics I posted above a couple of weeks or so ago I can't really see a problem with it, and am more or less happy to go with it.
O.K. so now having come to terms with the initial outlay of purchasing my Diamondback MTB, I will shortly be buying my mid-position motor and battery, which is going to be almost twice the price of the bike, but still just under a grand which was my target figure in the first place.
One other thing I would like please are some opinions before I make my battery purchase, other than the obvious, what is the difference between the the 36v & the 48v batteries, are there any advantages/disadvantages in going for the higher voltage one, would a 48v battery give more range for example?, are they legal?

Thanks in advance guys for your expert knowledge & opinions.

Nothing illegal about 48v, but most of the industry has settled for 36v.

For a given weight (i.e. same number of cells) the amount of energy stored is the same, no matter what the voltage. The stored energy is measured as Watt-Hours, (Wh) which is V x Ah.

If a system is designed to operate at 36v and you run it at 48v it will go quicker, but with less range (again, assuming same number of cells).

I think 36v is your best option.

Sent from my HTC One_M8 using Tapatalk

 

[kernow60]

Hi Alan
Many thanks for that, 36v it will be.

 

[D8ve]

The voltage has a few effects.
When you are designing a motor for a given power you could use lighter/ thinner wires. But that is cutting edge design shaving grass etc. We just buy an off the shelf motor.
For a given motor that is not electronically restricted it will run faster at a higher voltage, and waste more energy turning at low speed.
But the hub drive rotation speed is controlled so not much effect here unless your legs can do 300 rpm.
In saftey terms The expected danger is higher from over 40 volt systems.
But getting a personal dangerous shock from any sub 60 volt system is difficult. The text book example is a wet tramp trying to sleep between two sheets of wriggly tin. It contacted an electric fence and he received a fatal shock.
So a minute increase in danger with higher voltage.
Most bike batteries if shorted will produce ridiculous current and easily start fires or wield wires. A lower voltage battery here is likely to have greater current potential. ( my batt is rated as 160 amps continuous )
So a small amount of increased risk but not significant.
So get the battery for your motor. As 36 volt is common then I suggest they will be bulk manufactured and hence lowest cost in general.

 

[kernow60]

Thanks D8ve
Actually I have noticed the higher voltage (48v) batteries on sale seem to be listed with lower a/h than some of the 36v alternatives.
I have seen advertised a 36v 14.5a/h bottle battery which will probably suit my needs, with Panasonic cells, are these as good as the Samsung cell models.
I assume with the name Panasonic you can't go far wrong.

 

[D8ve]

Thanks D8ve
Actually I have noticed the higher voltage (48v) batteries on sale seem to be listed with lower a/h than some of the 36v alternatives.
I have seen advertised a 36v 14.5a/h bottle battery which will probably suit my needs, with Panasonic cells, are these as good as the Samsung cell models.
I assume with the name Panasonic you can't go far wrong.

That's what Alan Q was saying the total power in a battery is Volts times Amps. So 36*16= 48*12 are the same weight.
I cannot advise on the current battery market but I loved my Panasonic system so I suspect your right

 

[anotherkiwi]

LG, Panasonic and Samsung brands are the most common. There is some Sony around but very rare. Any of the above are fine, if they are real and not counterfeit...

Tesla has a partnership with Panasonic.

 

[kernow60]

O.K. guys thanks again for your input, I shall go with a 36v 14.5 a/h, which hopefully, with care, should give me a reasonable range.