Kale44 said:
"160ah / 8h = 20A continuous current load." I've read that lead acid batteries (which I'm using for cheaper price) should not be discharged lower than %25, so wouldn't I need something like 200ah batteries.
Going by the common wisdom about SLA, even going below 50% will shorten their lifespan (which is already very short, only a hundred or so cycles; I got a lot less out of the ones I started out powering by bikes with way back when). You also have to recharge them immediately after use; leaving them in teh discharged state causes damage.
Then there's the Peukert effect, which wastes a huge amount of the capacity available in a lead-acid battery (not nearly so much in most other chemistries; hardly even noticeable in Lithium packs).
All the numbers below are off the top of my head, so you'll need to look up actual present-day numbers for batteries; my direct experience with them is almost a decade old, since I switched over to NiMh, then RC LiPo, LiFePO4, and now NMC for the last 8 or 9 years, I think it is.
So, you might need up to 300Ah+ of lead, which is going to be immensely heavy.
Even the original 160Ah is going to be hundreds of pounds--completely impractical.
IIRC, the last set of SLA I used were group 35s, like a lot of powerchairs use. I think they were about 9"x7"x9", and weighed about 35-40lbs each, for only around 20-25Ah usable (the 35Ah+ claimed is at 1/20C, meaning 0.05 * 35Ah = 1.75A current draw. At the high currents needed for motors and stuff, peukert effect steals so much energy you don't get anywhere near the rated Ah).
So, if you used group 35 SLAs, you'd put two in series, for 24v 35Ah nominal. To get 160Ah you'd need 160 / 35 = 4.5, so 5 of those pairs of batteries. That's 10 of them. If they weigh conservatively 30lbs each, that's 300lbs. If you only were able to use say, half of the actual capacity, you'd really only have 80Ah. So to get the actual 160Ah, you'd need 600lbs of SLA to do that.
It's worse than that, though, because the mass of the batteries is so great it will rival or exceed the system and load mass, so the power needed just to move the batteries themselves is so high you have to use more batteries just to do that.
Generally the group35 size is around $80-$100 each, so it would cost you up to $1000 for one set of 10, or $2000-$4000 for the full set of 20 or 40 you may actually need.
You can look up numbers for the various types of SLA to see what actually works out best for your application...but I can virtually guarantee you it isn't cheaper for your purposes, given the lack of capacity you can get out of them, the mass you have to use, and the fact they must power the motor enough to move themselves up the hill along with the rest of the system.
This page has some info on sizes, though they don't list the weights, etc
https://www.batteryequivalents.com/bci-battery-group-size-chart.html
A 160Ah 24v lithium battery, which will be fairly small and light, will last 10-50 times as long as a lead-acid pack, and will probably cost less than $1000.
A quick google finds 12v 160Ah LiFePO4 packs for around $500 each or less, though that's on Alibaba / Aliexpress, so from unknown Chinese vendors, and unknown shipping costs and times. So two of those in series, or one of the 24v versions (about twice the cost) would work. Specs vary, but on average I find the 12v units are around a foot by a foot and a half by 7-9", and around 60lbs.
I've been told regen braking would not be an option, as walking speed would not be enough to generate any electricity back into the batteries.
It's not the ground speed that's important, it's the motor speed. Since that will still be the same speed (presumably) walking downhill unpowered as the motor will power the system uphill, then the motor (because of the gearing between wheel and motor) will generate the same voltage downhill that it took to power it uphill, and if the voltage of teh batery is lower than that, current will flow into the battery.
That's only if there is no freewheel or clutch between the wheel and the motor, though. So for instance with the pwoerchair motors with worm gears, they won't really bea ble to be pushed downhill without motor power; you'd have to disengage the clutch on the gearing and lose the regen ability. If it's not a worm gear it will proably work ok.
But regen is only likely to recapture a few percent, maybe up to a quarter, of the energy used, depends on the situation. Might be worth having, assuming the extra wear on the mechanical parts of the system, and the potential inability to use the system without the motor, are compensated for by whatever amount of energy you get back.
https://www.motiondynamics.com.au/my101 ... motor.html
Your link is incomplete; you'll have to repost the part after "my101".
