I understand the obvious points:
12V has more power, equating to higher speed
same voltage = 12v half as heavy
however, I notice on the Trojan battery spec sheet that the 6V’s are rated for almost twice as long @ 75 amps. I’m kinda stupid, but does this mean that at a constant 75amp pull, the 6Vs last longer?
Also, it seems that the 6Vs have a much greater number of cycles before biting it.
Am I tracking here, or am I missing something big? Thanks.
for a 120 volt car you’d need ten 12 volt batteries or twenty 6 volt’s. The 6 volts would give you more range but weigh a good bit more (twice as many). The 12 volts would weigh less but drain quicker. If your range isn’t too important then the 12 volts may be a viable option.
Assuming the 6v batts were the same weight and capacity of the 12v. It would take (20) 6v to make 120v and (10) 12v to make 120v. Would that then be a wash if you got (20) 12v batts and wired in buddies of two for a pack of 120v with twice the capacity? Or would there still be some other advantage to running one over the other?
I ask because I was wondering if I could run (20) 12v batts in (2) strings of (10) when commuting, but then change the jumpers to run all (20) in series for a pack of 240v at the strip.
Cheers
Almost always the 6v batteries will have larger ah ratings. So if you have 20 6v batteries @120V you will go farther than you will with 20 12v batteries @120V(2 strings).
You could do something like your booster pack (120V commute, 240V race) but you would have to make sure all of your equipment could handle it. Your controller would have to be reprogrammed every time you went from race to commute and then again when you went from commute to race. Mounting and unmounting (both physically and electrically) 10 12v batteries is not going to be a trivial job (6hrs min? one way). You will also probably run into problems with one pack of batteries being "newer’ (less used) than the other. Bad things tend to occur under those conditions (batteries blow).
[QUOTE=Lazlow;284]Almost always the 6v batteries will have larger ah ratings. So if you have 20 6v batteries @120V you will go farther than you will with 20 12v batteries @120V(2 strings).
You could do something like your booster pack (120V commute, 240V race) but you would have to make sure all of your equipment could handle it. Your controller would have to be reprogrammed every time you went from race to commute and then again when you went from commute to race. Mounting and unmounting (both physically and electrically) 10 12v batteries is not going to be a trivial job (6hrs min? one way). You will also probably run into problems with one pack of batteries being "newer’ (less used) than the other. Bad things tend to occur under those conditions (batteries blow).[/QUOTE]
I don’t think reprogramming a controller would be that much after the first couple of times (IF even needed) since the settings would be the same. I remember a good friend doing a fuel injection reflash with his lap top in seconds in the parking lot before a race (names have been with held to protect the not so innocent lol). When people asked what he was doing he’d just say he’s playing a game. He wasn’t lying, they just didn’t realize THEY were his game. He had a hot turbo Buick Regal that had a computer controlled wastegate. He’d run a minimal boost fuel / timing curve during the week and then reflash the computer with the “race” fuel/timing curve and high boost opening.
If I can do an entire engine swap with one helper in a couple hours (don’t ask how or why I got that fast, I’ll just say it used to be this ex-street racer’s weekend warrior up the sleeve trick. Notice a trend here? Tame daily drivers that were absolute monsters on the weekends.) I’m sure I can disconnect and re-connect twenty batts in less than 30 minutes.
As for the uneven battery wear, no batteries would be eliminated. I would merely switch from 20 batts wired as two strings of 10 (for a voltage of 120 at Ah times 2) to 20 batts wired all in series (for a voltage of 240 at Ah times 1). All batts still wear evenly. The problem would actually be finding batts that were not a weight burden, but had high enough Ah ratings for a hard 1000+ amp launch and 1/4" mile run. And it doesn’t really matter anymore because I plan to go autocross, not dragstrip. So, no real need for monster high top speeds anymore (as of yet, heh heh.)
Cheers
Come to think of it, maybe I should give up on the EV hot rod dream and go back to saving up for my turbo V6 I’ve researched and planned for over the last 4 years. It’d be cheaper… Nah, once I got it done gas would be either $8 / gal. or maybe even regulated and restricted from personal use.
The more I think about it the simpler this idea seems. Assuming that the connections coming off the packs where joined at some point, one could just connect the pos side of one pack to the neg side of the other. You could probably even hook it up with contactors so you could just hit a switch to go from series to parallel.
P1(junction)P2 N1(junction)N2
Changes to
P1-N2 P2(junction) N1(junction)
Now you know what I’m talking about! Sorry if I’m just regurgitating what you just posted. If one were to just wire two 10 batt packs, each in series, then you would have just one junction to worry about. Then it’s a choice…Do I wire the two packs together in parallel (120v / 2Ah) or series (240v / 1Ah)?
Simple, no?
I used to do the same with the 6 cell battery packs on my r/c boat. I now use a simple little connector for my Elec. RC planes. I have a little racer that uses a 3 cell Lipo pack (terminology for that would be 3s1p) and then I use two of the same packs with a parallel connector (3s2p) for a bigger plane for longer duration with the bigger motor. Then again in a twin that has the motors wired in parallel, but I connect the two packs together in series for twice the voltage (6s1p). This setup allows me to use one type of pack in several configurations so I don’t get stuck with one pack for plane A and another for plane B and so on… Okay, I got a little carried away with the RC stuff. I guess I’m just trying to justify my 20 year long obsession with RC electrics. See dad…I knew playing with those “toys” would serve some purpose! haha…
You’ll probably see me slip in the pack cell(batt) number and string(parallel) terminology in future posts. It would look like this:
For New Dawn…10 batts in series = 10s1p.
The configuration at the top of my post- 20 batts all in series = 20s1p
or the split setup (2) parallel strings of (10) batts = 10s2p.
Incidentally the (2) packs of (10) batts joined together in series would be termed as 20s1p because it would be the same as 20 batts all in series.
Okay this might be getting confusing so I’ll stop now.
Cheers
When I first responded to your booster pack idea I had it in my head that you were going to physically remove the batteries. Thats where the 6 hours would come in.
The P and N I was using was positive and negative.
Yeah
Just after I posted I reread your post and saw that you wrote “packs” not “batts” and I understood the P and N, so I’m pretty sure we’re talking about the same thing now. Man, if I could only post screen shots from autocad. Then I could draw diagrams and not be so verbose. Oh, wait. I’m just that way anyway 
.
White Zombie is currently using 16Ah Hawker Genesis batteries 30s2p :eek: . I wonder if there is an equalizer that will handle that many batts or if he equalizes all 60 of them by hand. I wouldn’t have a life if I had to do that with a daily commuter.
Cheers
Yeah, we are on the same wavelength now.
I think they make little equalizer circuits that you attach one to each battery. When that battery is full (charged) it cuts off the input voltage to that battery. It would be a major PITA getting it set up the first time but then I think you are done. Until you replace the batteries in about three years.
Lazlow