7s2p battery build which cells

Hi, this is my first post and also my first battery build. I have a carbon gt which I use mainly. But I also have a boardup folding build for time when I can use the gt. The problem is the range and sag are terrible. It’s running the 7s2p 83mm hub diyeboard kit with Samsung 22p cells. Im going to re make the battery with better cells. It doesn’t need to crazy powerful more of a comuter. I’m thinking either sanyo 20700b 4250mah or samsung 40t 4000mah. The pack can only be 7s2p because of the tight space. Which cells would get me more range. Thanks in advance. Jamie

I just use lipos on my commuter board and works pretty well. Problem is if you can’t increase cells in series to increase voltage then your amp draw is going to remain what it is and the max discharge or ampacity of the cells is the only thing you can increase (assuming no room to add cells in parallel) and really there isn’t some 10X cell they are more like 30% difference in ampacity. I use 2 5Ah 5S in series to make 5Ah 10S or 185Wh battery (good for me for about 12 miles without sweating it)

Thanks for the reply, I hadn’t though of lipos. Do you remove to charge or are you using a bms? I was thinking the 40t cells (35a each) would make a big difference from the 22p cells (10a each) do you think this would still not be enough?

You should be fine on 40T if you are not a heavy rider. I have a 7s2p 30Q on a light weight 5kg build that gives me 23km range on a single gear drive. I weigh 70kg and am not a very aggressive rider.

Thanks, I am pretty heavy 90kg. Its actual runs pretty well on the 22p cells when it’s fully charged. I might just try the 40t. Do you think I would get more range with 40t or sanyo? I’m not to concerned with going fast.

molicel 42a is better than the 40t although a bit expensive. at only 14 cells, it may be worth it

Thanks, I’ll have to check them out. I’m not to concerned with price as it’s such a small pack. Just want to get some decent range

Personally remove them for charging but using backpack buckles bolted to the board to make that easy (have a pair of backup batteries in case I want extra insurance on a long cruise or don’t want to wait for batteries to charge) but have seen other setups with lipo and BMS. 7S charger might be a hard thing to find.

Edit found one not sure how good it is but exists at least https://hobbyking.com/en_us/turnigy-mega-1000w-8s-40a-lithium-polymer-balance-charger.html

Says out of stock but guess this one superseded the one above https://hobbyking.com/en_us/turnigy-reaktor-30a-1000w-balance-charger.html

I think I’ll have a look into bms and charging options before I decide what to use. Thanks for the advice everyone. I’ll update once I get it sorted.

Figured worth taking a quick pic to share of my setup. I admit it isn’t the prettiest build but I’m super happy with it functionality wise.

IMG_20190609_065237

Actually going to shorten those phase wires because it’s bothering me now that I’m staring at it. Could also route the connections through the battery boxes but I was at the limit of my 200x200mm print bed for the shells.

Edit a little better now

IMG_20190609_073653

1 Like

Looks great, I’m all for function over looks. I’d really like a single Outrunner on mine but the space is so limited on the board up deck.

After much deliberation, I’ve decided to go with 20700 cells. I realised the 21700 cells wouldn’t fit. I’ve ended up going with sanyo 20700 3500mah 30a. I’ll repot back when it’s all together. Thanks again for the advice everyone. Jamie.

Got my pack finished and just been for a test ride. Got just over 8 miles with some cruising along and a couple of hills. Doesn’t seem to be much sag. All in all I’m really pleased with it. Thanks to everyone who gave me advice. Just got to tackle the new battery for my carbon gt now.

1 Like