I think your board is about 770 watt hours. The 30 mile range of the GT is a best case scenario, light weight rider, lots of stops which allow the battery to cool, low average speed, etc…
The board in that photo is sporting a 12s6p LGHE4 system Panasonic GA’s work well in a pack this large too. MJ1’s are another that have similar specs to the GA.
@Stevemk14ebr 18650’s are ubiquitous and have been around for a long time so they have already been proven within a specific criteria. I am all for improvement and optimization but when it comes to investing several hundred dollars in a power source I think it is best to stick with a proven source. Tesla for instance is leading the way in battery assembly, they use 18650’s and provide an 8 year warranty on their packs! Of course the empty space around the cells in a tesla pack is used for cooling fluid so a solid block of square cells may end up running much hotter than cylindrical cells.
@Randyc1 you can actually use recycled laptop cells once you get into packs this large but the voltage will sag a bit more than higher discharge cells while climbing or accelerating heavily. This is from personal experience and not just speculation.
Good to know. I should be getting an extra motor when I upgrade my Carvon to the V2.5. Was thinking of putting it on a belt drive, but like the way the single Hub feels.
What amount of voltage sag have you seen with the LG 18650 cells when going up steep hills?
How low would you recommend letting a li-ion pack go before charging it, 10% 20%?
You are usually safe taking cells down to 3.3v per cell under load, once you go lower heat will build quickly in your pack so it is best to go lighter on the throttle and nurse yourself home at this point to keep the pack from heating up and deteriorating.
Voltage sag is relative to the size of the pack and the resistance of the cells as well as the size of the load so it is difficult to give hard numbers that will translate to smaller packs. Needless to say the voltage sag is almost nil with 72 LGHE4 cells. It is quite impressive.
I was wondering about the voltage sag because with my 10s 2p with the basen 4500 near full charge and going hard up a fairly steep hill my total voltage sagged about 4 or 5 volts. I thought that was a lot but i’m not sure. Do you think that is a lot or does that sound about right for a pack this size?
That sounds about right. The easiest way to get your head around what is happening is to see that voltage sag and heat build up are linked. One important aspect of going big is the fact that voltage sag is decreased allowing us to discharge a pack more deeply before triggering a low voltage event which increases range. In theory doubling a packs size while keeping the load the same will result in more than double the range because voltage sag will be halved. Heat will also be lower so the pack will deteriorate more slowly resulting in more charge cycles before noticeable loss in capacity.
In my experience: yes.
I started off with a single motor setup, and later decided to add a second motor to the existing setup see what the difference was.
More uphill power, better acceleration but my range dropped noticeably, I’d say around 20-25% at least.
More strain on the batteries too.
I have a 10s2p made with x10 2s lipos (x5 in each parallel series) that’s gets 20 + miles. I haven’t actually pushed it to the limit because after 20 miles my legs are like jelly . But I think it will do 25, just guessing though.
I am on the Sanyo 20700 bandwagon right now. Our Pikes Peak edition FreeRide uses them and has 24 Ah @ 36v.
I like LG HG2 or LG HE4 if using 18650’s. It is a big jump in price to the 21700 size cell but it is worth it for the extra capacity and still be able to fit inside a 33inch wheelbase.
. But I think it will do 25, just guessing though.