DIY Dual Battery


Well-Known Member
The beauty to me of open source components is that they can adapt easily to whatever suits my needs. Usually I ride this bike with the 48v/10ah but a friend and I have a ride planned tomorrow that he has done before and said it took him 6.5hrs to complete. Every year around my bday time I like to do an epic adventure to say I did and this is the 2018 edition.

He is younger and more fit but we are old friends and we ride whenever we can together. I actually think he likes riding with me better these days because I can keep up and we get to spend more time chatting. Anyway it is going to be a long day in the saddle on dirt logging roads circumnavigating Saddle Mountain here in the NW Coast area of Oregon. Along the way we are going to try and find a stand of Old Growth Cedars that we both have heard about that are on the SE side of the mtn, we'll be starting the ride from the NW side. They are far enough off the road so that there will be some hiking involved but we have all day and will be in no big hurry, at least that is what he said but I know better because he has one speed and that is a few notches below full out. Ex marines are like that I guess.

I doubted that the 10ah battery would suffice so I fit a 52v/20ah battery we have on a used eBike into my frame bag and as it already had Anderson connectors on it so it mates up with my controller. The CA3 I use as a brain/display on this bike has the ability to allow for an A and a B battery that can be different voltages and chemistry even. In fact I was going to use a 36v/15ah Dolphin that was ordered by a guy who flaked on the deal as it fits into the same tray but I have been wanting to try a battery under the top tube so I went that route.


Got the bike all prepped and my pack packed this afternoon and it all looks good to go. If I eat all the snacks I am bringing I will come home weighing more than when I left. Part of the experience is to dial in the bike for some back country bike packing I hope to do later in the summer. With 30ah on board the bike should be able to do 100 miles @15wh/mile which is about my average if I want to end up with an average speed in the high teens to low 20's. Still that is about the same speed that a winner of a 100 mile gravel race these days would achieve without assist.....It's fun to get old!

rich c

Well-Known Member
I’d be seriously concerned with controller life when running on that 52 volt battery. How many amps is your controller rated for? Aren’t you going to build a lot of extra heat in it?


Well-Known Member
I have used the same Grin 40A controller, that I run @ 20A via my CA3 which provides all the power I need, on my other road bike which has a 52v battery for a couple of thousand miles with no problems. So I think i'm ok. While the day is going to be long with elevation gain and temps in the 60's and I won't be pushing out much for watts, probably 350w most of the time anyway.


Well-Known Member
40.5 miles 9 hrs. door to door on the day but he was an hr. late to the meet up, I was able to ride out from my friends place to the gate. The 20ah battery turned out to be a 17.5ah that cut out at 16.9ah and ran about 4ah through the other battery. My gps tracker let me down and didn't record properly and we only got to make a more informed decision about about where the old growth stand is for next time. Saw lots of clear cuts though and a few stands of nice Firs. Cloudy day for the most part with some spots of rain and some route head scratching/map consulting along the way but never had to back track. Which my friend who has been going out there for years told me is his first time not having performed that before. Had snacks leftover.

No problem staying with my friend on his dino bike and he was pretty beat at the end whereas I got to eat a delicious dinner cooked in a parrilla and a stroll on the beach with friends and don't feel over worked by the day.