So I have a battery pack... - Fuel Economy, Hypermiling, EcoModding News and Forum

Nevyn · 08-03-2010, 08:40 PM

We had a few "failures" in the UPS at work, so we had to get new modules to replace the bad ones. Everything was out of warranty, so there was no return on the old modules being taken out. After a moment's discussion, I walked by and overheard them talking about it. I piped up that I'd take them, and now that the new ones are in place I'm slowly bringing the old, "bad" modules home (not all at once because I don't want to super-kill MPG :P ).

I told them what my plans were for them, and they laughed and called me crazy, but let me have 'em.

So, now I'm the proud owner of EIGHT APC brand UPS modules.

In each of the eight modules, there are EIGHT individual SLABs (Sealed Lead Acid Batteries).

So, I now have SIXTY-FOUR (!!!) batteries to play with!

Some of them may be bad, but I bet most of 'em are good.

I took one apart tonight to see how they were configured. Sticker on the outside said 96V, 7.2Ah. Opening one up, I found this:

So they're set up as 12Vx8, single depth. That makes them 7.2Ah each. Which works out to:

460.8Ah @ 12V
230.4Ah @ 24V
151.2Ah @ 36V (1 spare)
115.2Ah @ 48V
57.6Ah @ 96V

Is it big enough to do anything with?

We have a Go-kart with no motor...

MPaulHolmes · 08-03-2010, 09:06 PM

Dude! That's enough to drive around in a full sized car for like 15 miles!

ldjessee00 · 08-03-2010, 10:29 PM

Wow, EV go-kart would be a fun starting project!

Nevyn · 08-03-2010, 10:47 PM

That's good to know. I wonder if more will go bad at work? We only replaced half of one rack; we have 2 racks...

At what voltage do I get 15 miles range?

Nevyn · 08-05-2010, 09:22 PM

So, I posted out to Freecycle in my area looking for treadmills. Got a hit! brought it home, opened it up, and found this:

Paul, Ben, and crew - is it worth anything, as far as go-kart size is concerned?

PERMANENT MAGNET DC MOTOR
Rotation: CW
Enclosure: Open
External Fan
90VDC, 1 HP SCR Controller 6 MPH
115VDC, 1.25 HP PWM Controller 8 MPH

MPaulHolmes · 08-05-2010, 09:34 PM

A 1 HP or 1.25 HP motor? Does the controller stuff mean that it has a controller built in? That size motor would be perfect for a go cart. I have a motor on my electric bike, that's about 0.5 HP, and it hauls around great! 1HP would be plenty!

Nevyn · 08-05-2010, 10:30 PM

Quote:

Originally Posted by MPaulHolmes

A 1 HP or 1.25 HP motor? Does the controller stuff mean that it has a controller built in? That size motor would be perfect for a go cart. I have a motor on my electric bike, that's about 0.5 HP, and it hauls around great! 1HP would be plenty!

I'm not sure, thus the picture. I'm guessing that if you use SCR, it's good for 90VDC and 1HP; but if you use PWM, it's good for 115VDC and 1.25HP?

Paul - what you mentioned earlier - how would I get 15 miles out of the "battery pack" that I have? As in, what voltage/depth combination would be best?

Daox · 08-06-2010, 07:05 AM

A GOOD efficient/aerodynamic/light car will use 250Wh/mile. You can calculate your range with that.

Higher voltage will give you more power as will a higher amperage controller. Also, being as those are only 7Ah cells, I would be wary of pulling a lot of amps out of them quickly. They only have little tabs. I was going to use these same type of batteries on my mower, but decided to use larger batteries instead.

Nevyn · 08-06-2010, 07:36 AM

Quote:

Originally Posted by Daox

A GOOD efficient/aerodynamic/light car will use 250Wh/mile. You can calculate your range with that.

Higher voltage will give you more power as will a higher amperage controller. Also, being as those are only 7Ah cells, I would be wary of pulling a lot of amps out of them quickly. They only have little tabs. I was going to use these same type of batteries on my mower, but decided to use larger batteries instead.

Higher voltage allows for a lower amperage draw, correct?

I'd use bigger batteries......but these were free.

I'm going with one of Paul's new beta "Killa-Amp" controllers. Overkill for small stuff, but if I'm going to do it, I'm going to do it right. ONCE.

I don't have the available funding to buy a controller outright, but I can space components out over time and actually end up having it sooner that way.

Anyway, let's do some math.

I've got 64x 12V, 7.2Ah batteries.

That's the same as 8x 96V 7.2Ah batteries.
8x 7.2Ah = 57.6 Ah total @ 96V
96V * 57.6Ah = 5529.6 Wh; 5.5296 kWh

Let's use 300 Wh/mi for now, 80% DoD:
5529.6% * 0.80 = 4423.68 Wh @ 80%
4423.68Wh / 300Wh/mi = 14.746 miles

so yeah, we'll call it 15 miles range. I did all the math right, yes?

Daox · 08-06-2010, 07:47 AM

Yeah, higher voltage gives you the same power @ a lower amp draw. Seeing as you have so many batteries I'd go with as high of voltage as you can. I honestly don't know how many amps you can draw out of those batteries, so you're going to need that high voltage to get some usable power (or run some of those batteries in parallel so you can pull more amps).