[SyCo]

Originally Posted by major

Look for the words Deep Cycle. Batteries advertising cold cranking amps are most likely cranking batteries. Good for 30 or so deep cycles. Real deep cycle Pb-acid batteries are good for 300 or more deep cycles. Look for golf cart batteries or similar.

Check out the Battery section of this forum.

Regards,

major

Ok I will, and I suppose those type of batteries will have AH ratings... Thank you!

[SyCo]

I did my first test drive yesterday, with full acceleration I read ~275A DC on the Fluke meter. At half throttle, I read 150A DC.

So 48x275=13,200W (~17hp) and 48x150=7,200W (~9hp). I think that is within the specs of my motor.

In second gear acceleration was surprising, even in third gear but top speed was not that fast ~15-20 mph. I did not try 4th because I did not have enough juice. Keep in mind tests were done in a small street and I may have reached a better top speed with more road available or in 4th/5th gear since I'm running low RPM on my motor.

I will have to get some decent batteries to do more tests.

[icec0o1]

That's sweet. Congrats on the good buy. Do you know what RPM your motor was running at at 20mph and 3rd?

[SyCo]

Originally Posted by icec0o1

That's sweet. Congrats on the good buy. Do you know what RPM your motor was running at at 20mph and 3rd?

Unfortunately not ... It was at night and I did not have enough light to look a the programmer (monitor) and the meter.

I will, of course, do some tests during the day and keep notes of everything I can

[SyCo]

Second test drive !! The chain tensioner is now installed to prevent the chain from wobbling. The previous owner installed a removable Reese tow bar so I can tow my EV behind my Honda CR-V. So first I went to a truck scale and weighted the car. 1060kg (2330lbs) with test batteries (4 x 35 lbs).

* Motor rpm limited to 2000rpm within the controller for the tests. Current set to 100%.

I did my test on a flat surface. Starting in 3rd acceleration was pretty good up to ~25mph @ 1400rpm (~280A). I then shifted to 4th and went to ~35mph @ 1200rpm (~150A). I was able to cruise for 2-3 miles at 35mph drawing ~150A.

I was a bit surprised to see how easy it was to reach and maintain the speed. I'd had thought that 48V would take forever to reach speeds in the range of 35-40mph.

Oh well, that is good news for me. Now I will have to try some slopes to see the amp draw and speed at different grades.

Using tests above, I've calculated my Wh/mile to be approximately 220Wh/mile at cruising speed on flat ground.

Originally Posted by icec0o1

That's sweet. Congrats on the good buy. Do you know what RPM your motor was running at at 20mph and 3rd?

according to tests above, that would be ~1200rpm.

[SyCo]

Quick update, I've cleaned my setup. Everything was loose for test purpose but now I'm starting to clean up everything.

Here are some pics which I think look a lot nicer


(Don't worry, my 12 volt battery will be fixed with something safer than an elastic luggage strap.)







Now I need some loom to make it even cleaner.



My next step should be my vacuum system for the brakes .

I'm still looking at a cost effective solution for a 48VDC to 12VDC converter. I saw some in Golf Cart parts on Ebay

[SyCo]

Ok Spring Update !!!

So my EV was asleep all winter but now the project continues.

I've bought some new batteries. Costco/Kirkland Marine Deep Cycles (125Ah with 12 months replacement and pro-rate after) (4 of them).

With more powerfull batteries I'm now able to accelerate much more quickly since more Amps are available (400-425A at times on my meter). Accelerating and running on flat ground is a breeze.

I ran 6 miles to ~40% DOD. I was accelerating hard and climbing light slopes. Of course batteries are not cycled yet but I seem on a good way to reach my 10 miles commute each day.

Now I really need to do more tests in slopes (I live in a city full of slopes). Preliminary tests showed that I don't have much power to spare in steep grades. But half of my commute is going down and half is going up so it should almost be okay.

[SyCo]

Here is an estimate I'm trying to do of my Ah requirements using some wiki information.

Since I'm using a 48V high amps AC system, I've guessed 400Wh/mile efficiency (anyone one with more accurate value for my efficiency is welcome to chime in ).

I want to be able to travel 20 miles.

So total energy required at 100% throttle (275A) is 275x20=5500 or 5.5Kwh.

Since my voltage is 48V this means my Ah rating will be the total energy divided by the voltage. In this case 5500W / 48V = 114.5Ah

I plan on going 80% DOD. So 114.5Ah x 1.25 = 143Ah

Now add Peukert effect. 143Ah x 1.8 = 257Ah

This is the worst case scenario for my energy consumption. I hope, after more tests, to get lower amps draw. In the meantime, I think that to reach my required distance, I would need something like 8 Trojan T-1275 rated at 150Ah. Two series of 4 batteries (total 48V) wired in parallel (total 300Ah).

Bank1: 12V-12V-12V-12V (48V, 150Ah)
Bank2: 12V-12V-12V-12V (48V, 150Ah)

Bank1 + Bank2= (48V, 300Ah)

Is this a realistic estimate ?

Note: I have not included my top speed since I'm using 100% throttle and I'm assuming I will need most of that to reach at least 30 mph.

EDIT: Btw I've got some price for local batteries...
Trojan T-105 6V, 225Ah @ 154$
Trojan T-1275 12V, 150Ah @ 224$
DEKA 8AGC2 6V @ 241$
DEKA 8GGC2 6V, 185AH @ 273$
T-105 reconditionned (1 year warranty) @ 61$
8AGC2 reconditionned (1 year warranty) @ 70$
Are those good prices ? What about recon batteries ?

[Buckster]

I think the chain will stretch pretty fast, you really need a slightly longer chain with a tensioner to preserve its life.

[icec0o1]

You have the math a little wrong there.

watts = amps * voltage

You have to go backwards. Based on your efficiency estimates, you say you'd use about 400Wh per mile which is probably a good guess. You want to go 20 miles so 400 * 20 = 8,000 Wh or 8Kwh.

8,000Wh / 48volts = 166 amp hours * 1.25% = 207 amp hours for 80% DOD to 20 miles.

If you want to max out the amps and add the Peukert effect,
207 * 1.8 = 373 amp hours.

If you're willing to drive very efficiently and maybe 15 mile range, go for 8 T-105 batteries for 225AH.

For a 20 mile range, you can go for 8 T-1275, 4 in parallel for 300amp hours. Or 16 T-105's would give you 450Ah but that'd be pretty heavy.

I would be tempted to buy the reconditioned ones. They're less than half the price and I would think they'd last longer than half of brand new ones. They'd only last a year or two max anyways so warranty is good (300 cycles or so).