DIY battery for Tonaro

[Geebee]

I am going to make a spare battery for my new Tonaro and I would like opinions on the following options.

12s LiPo is it safe? I already have the batteries for this, the extra power is of no interest but the higher cadence would be nice.

10s LiPo closest to the right voltage but Low voltage cutoff will be to low for safety.

9s LiPo would allow the in built low voltage cutoff to work and any loss of power would be irrelevant.

Cheers.

 

[Deleted member 4366]

I am going to make a spare battery for my new Tonaro and I would like opinions on the following options.

12s LiPo is it safe? I already have the batteries for this, the extra power is of no interest but the higher cadence would be nice.

10s LiPo closest to the right voltage but Low voltage cutoff will be to low for safety.

9s LiPo would allow the in built low voltage cutoff to work and any loss of power would be irrelevant.

Cheers.

Lipos are safe as long as you take proper precautions:

You mustn't overcharge them
You mustn't over-discharge them below the safe limit and then try and charge them normally.
Installation-wise, there must be absolutely no chance of wires rubbing through or pulling off to cause a short circuit -balance wires as well as power wires.
Your connections must be idiot-proof as far as connecting the wrong way round or getting mixed up any other way.
When you solder on connectors, it has to be guaranteed that the two wires/ connectors can't accidentally touch, which means soldering one wire then insulating it before you start on the next one.
You need a voltmeter or other device to make sure that you don't over-discharge.

12S would give you a useful gain in power and cadence. Your controller should handle it OK without modification, but don't connect in parallel with the standard battery. You could also solder the shunt a bit to increase the current up to about 18 amps for a further power increase.

 

[morphix]

I considered Lipos myself as a low cost and lower weight option than Li-Ion.. I like the idea of it, but I don't trust myself with the extra responsibilities of building them right and checking them etc.. I'm a bit nervous about batteries that need special handling..I had a battery cell blow up in my face while overcharging many many years ago and nearly lost my eyesight! It wasn't a Lipo or anything so don't let that put anyone off..it was purely down to my own stupidity.. but for me I just prefer the simpler option of a single battery and simple charger, even if there is a trade-off with extra weight and paying a bit more.

 

[NRG]

To underline the points Dave's made, the energy in these batteries is frightening. Be extremely careful and use the correct shrouded connectors for connecting up. Make it fool proof as stated.

Before I knew better I had this little mishap, used the wrong exposed connectors and just a brief glancing brush of one connector against another caused this:

Yes it hurt.

 

[Deleted member 4366]

Good photo NRG. It explains the problem really well.

We all learn by our mistakes. I was soldering the battery leads to a T connector (Deans), and I thought that I could slide up and shrink the heat-shrink sleeve afterwards. When I tried to solder the second wire, my iron just touched the other one and the tip was instantly vapourised, and I found later out that it had also vapourised one of the inter-cell connections, so I had to dismantle the pack to repair it.

 

[Geebee]

I am familiar with the care and feeding of LiPo's, any high current source needs respect.
I am starting to lean toward the 9s setup due to the voltage cut off protection.
Which ever way I go it will be used by removing the original pack and plug in to the original connector as it stops any chance of the batteries connecting to each other.

 

[hech]

I know there aren't many hills in Australia and you seem apparently uncorrupted as yet by power lust, but the Tonaro responds very well indeed to 12s lipo and it will zip you up AYERS ROCK in the blink of a wombats eyelid! The battery compartment will take 4 6s bricks at a squeeze but best fit a wattmeter if no LVC. (9s prob ok if lvc>32v.)