[QUOTE=bblocher;3702]I’m so focus on 12v I did forget to mention that costco also carries 6v 220AH batteries for like $75. The only problem is I usually only see 6 or so in stock at a time 
If you’re like me and have 3 costcos within an hour drive it might work out 
Brian[/QUOTE]
hahaha I’ll definetly have to go look at costco for some batteries then…
I also need to do more research. 
I’m going to run a 36v system. I was thinking of using three 12v batteries in series. and three series in parallel so i could get some range. but the controller needs 400 AH and the batteries that i was thinking of using only put out 85 AH
I don’t know, but i think that three batteries that put out 85 AH each wired in series will still put out 85 AH. But I’m not sure. If I’m right then i will come out 155 AH sort (and i don’t want to put too much weight in my car).
I found a 125 AH 12v battery but it is expensive, and i will still come up 25 AH sort. we can get the AH using 6v batteries (which is even more expensive), but i don’t want to spend that kind of money unless i know my first idea wont work.
I’m thinking that using less AH will ether
Not work
Or work, but run at a lower rpm
Thanks for your time
[QUOTE=U4edot;4022]I’m going to run a 36v system. I was thinking of using three 12v batteries in series. and three series in parallel so i could get some range. but the controller needs 400 AH and the batteries that i was thinking of using only put out 85 AH
I don’t know, but i think that three batteries that put out 85 AH each wired in series will still put out 85 AH. But I’m not sure. If I’m right then i will come out 155 AH sort (and i don’t want to put too much weight in my car).
I found a 125 AH 12v battery but it is expensive, and i will still come up 25 AH sort. we can get the AH using 6v batteries (which is even more expensive), but i don’t want to spend that kind of money unless i know my first idea wont work.
I’m thinking that using less AH will ether
Not work
Or work, but run at a lower rpm
Thanks for your time[/QUOTE]
I think you might have some of your numbers confused. Motor controllers have no idea how many AH your batteries have. The controller WILL have a MAX Amps that it can draw and this is NOT related to the AH rating of the battery. AH is Amps over a given hour rating (most batteries published number is a 20 hour span for lead acid). You really need to view your system on how many watts it will take for your purpose and go from there. If this is going in a car then 36V will honestly only get you to about 25mph, if that. I’m not sure what your application is. You’ll need to increase volts to get faster speeds.
Hope this helps,
Brian
Thanks but
I was told that the fork lift motor would get up to about 4000 rpm’s and with a five speed transmission i think i can get 75mph.
I don’t know how many W the motor uses
But does adding batteries in series increase amp draw. (I don’t think so but I’m not positive)
Sorry not trying to bring down your project or anything. I did some math and as long as the motor can take that kind of current it’s possible. The motor can only take 36v though?
As I mentioned before it call comes down to how many watts you need. There are some formulas to figure out how much horsepower is required to move an object and take into account air resistence, etc.
1 hp = 745.699872 watts not accounting for motor inefficiencies. So lets say it takes 20hp to move your vehicle at 55mph. That’s about 15k watts of continuous power. If you want to drive that speed for an hour you need a 15k watt/hr power source. Now lets use a 36V source and figure out how many Amps would be required. 15000/36 = Amps = 417 AMPs. Which is about what you were mentioning earlier and maybe I misunderstood.
So the only problem I see is dividing that kind of amperage up over multiple series of batteries. For each series you can divide the amperage. Even with three series you’re still looking at almost 140 amps on those batteries. Also you’ll need to check the size of wire required at the motor (it’ll need to be huge to push 400+ amps). Can the motor sustain this kind of amperage?
Typically what you’ll find are motors designed to work at much higher voltages so the amps can be reduced and therefore also the gauge of wire required. If you think of the internal windings of the motor they also would need to be large to accomidate for the higher amps.
I found this table for amps vs gauge:
http://www.powerstream.com/Wire_Size.htm
Brian
My motor is rated at 7.5 HP (I think it can get more than that).
That would take 5,592W.
Which would draw 155A
Can you check my math please
But if that is the case then i can get away with only 2 series of batteries
Thanks for the link and your time you’ve been a great help
[QUOTE=U4edot;4028]My motor is rated at 7.5 HP (I think it can get more than that).
That would take 5,592W.
Which would draw 155A
Can you check my math please
But if that is the case then i can get away with only 2 series of batteries[/QUOTE]
Yep the math is correct. The only question is can 7.5 HP meet your needs.
Brian
[QUOTE=U4edot;4028]My motor is rated at 7.5 HP (I think it can get more than that).
That would take 5,592W.
Which would draw 155A
Can you check my math please
But if that is the case then i can get away with only 2 series of batteries[/QUOTE]
eDot, keep in mind that 7.5 HP is the MAX OUT PUT of your motor which means 155A is your MAX draw for that motor… .righT???
Unless you’re always gonna have this puppy floored and pushing the limits you wont always be drawing 155A, if that makes sense.
[QUOTE=bblocher;4030]Yep the math is correct. The only question is can 7.5 HP meet your needs.
Brian[/QUOTE]
Again, if 7.5 HP DOES meet his needs, that would mean that his system would be under full stress whenever being used. Right?
Sorry if any of that is wrong. I’m still a SuperNoob myself and just learning. 
bbbllloooocher,
you were saying if it takes 20 HP to move your vehicle and maintain 55 MPH, that would mean while you’re cruising around at a constant 55 MPH you’d be drawing 14.92 kW, and per hr it’d be 14.92 kWh. Thats a lot, ja?
Does it honestly take 20 HP to maintain 55 MPH?
Maybe i just put 2 and 2 together… ahahha
Umm,
I just did the math, and 20 HP is going to cost you 14.92 kWh,
and if you have a 120V system, using 6v 220AH batteries, you’ve got a bank of 120v * 220AH = [B]26.4 kW[/B].
Using a bank of 26.4 kW and drawing 14.92 kW an hour will allow you to go 55 MPH (drawing 14.92kW) for 1.77 hrs.
26.4kW / 14.92kW = 1.77 hours
Right or wrong?
[QUOTE=PATZKE;4164]Maybe i just put 2 and 2 together… ahahha
Umm,
I just did the math, and 20 HP is going to cost you 14.92 kWh,
and if you have a 120V system, using 6v 220AH batteries, you’ve got a bank of 120v * 220AH = [B]26.4 kW[/B].
Using a bank of 26.4 kW and drawing 14.92 kW an hour will allow you to go 55 MPH (drawing 14.92kW) for 1.77 hrs.
26.4kW / 14.92kW = 1.77 hours
Right or wrong? :D[/QUOTE]
Technially the math is correct, BUT lead acid batteries are not designed to be drained in that short of a time frame and in addition you don’t want to drain lead acid 100%. Lead acid batteries AH rating is for a 20 hour drain. Some brands will advertise a 5 hour drain rating too but it’s not as common. For example the Trojan T-105 6V is a 220AH battery. However, it’s 5 hour rating brings it down to 185 AH rating. I’ve read that you’ll only get maybe 60% of the 20 hour AH rating if you drain the battery in 1 hour and it goes up from there.
So long story short, there are many variables that will affect the performance/range of your EV As for how much HP is required to do 55? That number can very dramatically based on your vehicles drag coefficient. Unless you can find this number for your vehicle it is somewhat of a guessing game.
Brian
[QUOTE=bblocher;4172]Technially the math is correct, BUT lead acid batteries are not designed to be drained in that short of a time frame and in addition you don’t want to drain lead acid 100%. Lead acid batteries AH rating is for a 20 hour drain. Some brands will advertise a 5 hour drain rating too but it’s not as common. For example the Trojan T-105 6V is a 220AH battery. However, it’s 5 hour rating brings it down to 185 AH rating. I’ve read that you’ll only get maybe 60% of the 20 hour AH rating if you drain the battery in 1 hour and it goes up from there.
So long story short, there are many variables that will affect the performance/range of your EV As for how much HP is required to do 55? That number can very dramatically based on your vehicles drag coefficient. Unless you can find this number for your vehicle it is somewhat of a guessing game.
Brian[/QUOTE]
Sweet.
So essentially i am headed the right direction with my math, i just forgot to factor in the inefficiencies.