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200a continuous would be beating up any 51ah cells and the likelihood of them having a bms that would allow it is close to 0.

Just reading this thread for the first time. Cool stuff, ready to see what's next!

I have my small off grid house running off 48v, have about 3.6kwh of lifepo4 in my RV, and am into hybrids and EVs.. so this is right up my alley.
 

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No clutch , so no grass cutting or snow blowing in this setup. We'll see with the tiller but have my doubts on 200A continuous...
There is a way to use the mower and blower. The GE Elec Trak (1969-1975) had electric motors on each attachment. The GE's were also rebranded for CUB, Wheel Horse and others.
Here is a quick search result.


Cheers,
Gordy
 

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So i was in a hurry last time i posted, freed up a bit now.. As far as 200a @ 48v, it's fairly easy to get a ballpark idea of power requirements between hp and W, because 746w=1hp.

So for example i have an old JD 112 garden tractor that had 12hp, and it's got a 30" tiller on the back of it. Right there you know it takes less than 12hp to run a 30" tiller under a wide range of conditions or they wouldn't sell it that way. It would depend on ground conditions, depth, and travel speed how much hp was actually required. But let's say it took 6hp to run the tiller. 6 x 746 = ~4500w. Now, 4500w divided by 48v would equal Amps required to do it (but let's use 50v because that's more realistic for a "48v" lifepo4 pack, and easier math). 4500w / 50v = 90amps. But, nothing is 100% efficient, so if we say that all the junk between the battery and the tiller adds maybe 20%, 90 X 1.2 = 108amps. So if you assume 6hp to run a 30" tiller, with a 48v nominal battery pack and 20% efficiency losses, you would need 108 amps to do that. Now, take your 51ah battery, and divide by amps to get hours. 51ah / 108a = .47h. So about half an hour of tilling like that to drain from full to empty.

That doesn't consider the power used to push the tractor, but considering the speeds involved you could be pedaling the tractor with your own legs and it wouldn't kill you. The power to propel the tractor at tilling speeds would probably add only 5% to that power consumption.

So that's an example of how to ballpark power, amps required, and how long it will last. Not exact, but good enough to plan a project around.

Now, issues.. i think the Case tillers are bigger. You have electric conversion losses AND hydraulic conversion losses. And probably biggest issue is just the size of the battery, not in terms of run time but in terms of something called C rate. Batteries have certain rates of charge and discharge they are comfortable with, and beyond that bad things start happening. On an old lead acid battery you get a lot of heat buildup, bubbling electrolyte creating flammable gases, etc. On a Lifepo4 you're mostly just shortening it's lifespan but not making it dangerous, so that's nice.. Lifepo4 im pretty sure have max recommended current of about .5c, which means you preferably shouldn't fully charge or discharge it any faster than 2 hours. So the above scenario would be highly abusive to the battery as it would be closer to 2c.
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You can get the C rate from the amp hours. 51ah means 51amps flowing out of it represents 1c, because it would take 51amps for 1 hour to get 51ah, that's 1C. Trying to flow ~25amps out of it would be .5c (it should be happy). 25amps x 50v= 1250w / 746 = 1.6hp continuous. That battery is only happy providing ~1.6hp continuously, any faster and you're burning the candle from both ends and shortening its lifespan.

I understand it's a 'proof of concept' battery and more capacity will be installed later. This is just an example of how it's not just how long the battery can do something once, but whether it's healthy for the battery to be doing that repeatedly.

And with the old GE electraks my impression is that while they could perform for longish periods, they were killing the batteries by doing so. This is the same truth as the current lead acid 48v zero turn mowers which CAN mow 1 or 2 acres or whatever they claim, but you're beating the batteries to death and by next year it'll be a fraction of that because you're murdering the batteries. If you stay in their 'long term healthy' rate-of-discharge and depth-of-discharge limits, they can probably mow .5 acres or less and be able to expect to do that for several years, more like we would expect a set of properly maintained golf cart batteries or a car battery to last. But that number doesn't sell mowers OR batteries. ;) Saying it can mow 1 or 2 acres gets the mowers out the door, and what happens next year is that guy's problem. But we do sell replacement batteries so you can mow 2 acres again. 🤑
 

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Discussion Starter · #68 ·
Still waiting on the hydraulic pump mounting plate but thought I’d share a couple more pictures. My plan of the piano hinge motor controller panel didn’t work out (oh, how I tried),
this panel is now fixed:
Gas Engineering Machine Composite material Motor vehicle




Motor vehicle Gas Engineering Machine Auto part



I also decided to make all the major connection points in the former home of the gas tank as inevitably I'll need to make wiring changes and this seemed to be the most accessible location:
Tire Wheel Vehicle Automotive tire Hood
 

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If not running a 3pt a decent sized battery box might be able to hang in the 3pt area and not extend beyond the rear tires much or at all and still hold 100lbs of batteries.. a lot of it is just going to come down to the shape of the cells you run. That will dictate in practical terms, how they can be laid out and what the battery box ends up looking like and where it can fit.
 

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If you never intend to run your tires in the narrow position there is a good 6+" of clearance on either side of the gas tank 'box' before you actually hit the tire. So if you were to cut up and rebuild that area you could take advantage of a lot of empty space under the fenders.
 

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Discussion Starter · #76 ·
I'd reshape the fender/seat support and fit the pack where the gas tank was. Could make it fairly factory looking and not hinder your view of the drawbar.
Ok, you really got me re-thinking my temporary sleeve hitch location for the battery bank as I removed a lot of front end weight swapping the ICE for with this electric motor. Think I’ll figure out a front-end battery mounting setup to start with. I do agree over the rear wheels would be ideal and maybe the final location but I really want to use that (accessible area) for making wiring changes while getting things working.
 
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