Adding a second battery?

[Dan de Angeli]

I would like to add a second battery to my existing setup on my Yuba Mundo. Has anyone done this and what kind of toggle switch did you use? Here is the bike I am upgrading.

https://photos.app.goo.gl/m8jOb4HCoxK1HHVd2

 

[harryS]

A DPDT switch, something like this one with screw terminals if you cannot solder. This one handles 20A, which is more than what your motor will draw at running speeds.

I have carried multiple batteries, but I don't bother with switches. I use connectors. Hook up a fresh battery when the old one is run down. I can remove the batteries for charging and storage in a safe place when not riding. I don't have to carry them when not needed. XT60 and XT90 connectors are commonly used for this purpose, but connectors have to be soldered. These XT90's are an anti-spark model.

Why anti-spark? When a bike controller has been sitting for a while with no battery, it will have a large inrush of current when a battery is connected, enough to spark/pop. Annoying, and it degrades the contacts.

 

[Dan de Angeli]

Thanks HarryS!

I like the idea of being able to hook up a battery rather than having a switch. Soldering the wires to the XT90 is not a problem. Removal of both batteries is critical when winter comes and I have to bring them inside for recharging.

Did you get a premade battery or did you make your own?

 

[harryS]

My batteries are all purchased.

 

[WilliamT]

I added a second battery to get more range from my cargo bike. For me, I added a separate 350 watt front geared motor kit. The second battery sits behind the seat, in a bag, bolted to the rear deck. The bag is a perfect fit for the dolphin battery.

Sometimes I have to carry a 17 inch laptop, in addition my gym clothes, dress clothes, shoe trees, etc. The second kit really helps out a lot. 90% of the time, I only use the front motor and use the rear as an temp assist for steeper hills. This increases my range from 15-20 miles to 40 miles. I keep the front assist at 3/5 and the rear at 1/5. When the front batteries start to drain down to 40%, I increase the assist in the rear.

This lets me go safely for 2 day of commuting before charging. With a full load, I still average around 17-18 mph that those assist levels.

 

[Gionnirocket]

A DPDT switch, something like this one with screw terminals if you cannot solder. This one handles 20A, which is more than what your motor will draw at running speeds.

I have carried multiple batteries, but I don't bother with switches. I use connectors. Hook up a fresh battery when the old one is run down. I can remove the batteries for charging and storage in a safe place when not riding. I don't have to carry them when not needed. XT60 and XT90 connectors are commonly used for this purpose, but connectors have to be soldered. These XT90's are an anti-spark model.

Why anti-spark? When a bike controller has been sitting for a while with no battery, it will have a large inrush of current when a battery is connected, enough to spark/pop. Annoying, and it degrades the contacts.

Absolutely the wrong switch. In needs to be DC rated.

 

[6zfshdb]

I built an aluminum box to carry a spare battery on my rear rack.




I thought about adding a cut over switch but eventually realized it wasn't necessary. I stop occasionally to have a sip of water or a snack so why not just switch batteries when one gets low?

This isn't an option though if your batteries don't match or are hard wired to the bike.

 

[Gionnirocket]

I alternate between 2 batteries with my lawnmower and swap between them every time I empty the bag. That way I run the two down equally and I don't end up with one at 20% and the other at 50% when I'm done. Both can sit in the mower at the same time and it's just a matter of which one I push down hard enough to lock in.

 

[Gene02638]

Absolutely the wrong switch. In needs to be DC rated.

I added a second (dissimilar) battery to my old ebike. I used simple on/off switches (on each) to insure they were kept separate. It worked fine.

 

[Gionnirocket]

I added a second (dissimilar) battery to my old ebike. I used simple on/off switches (on each) to insure they were kept separate. It worked fine.

You may have gotten away with it... and it will work... Doesn't mean it is what you should do or advise others to.
2 separate switches isn't safe as one can be accidentally turned on when the other is already. A selector between the two is much better.
And if you mean not DC rated at proper voltage/amperage.. Again not what you should advise others to do. Though they can work, additional precautions are needed that not all will understand or remember. Same goes for dissimilar batteries.