[integrawow]

For a little bit of info, I have an old 91 Acura Integra that has been lightened a lot. I've got a 5-speed transmission and LOTS of room inside of the car and under the hood as compared to smaller cars. The car isn't as light as a Metro, but it's pretty darned light.

I've done research and figured that I could roll with an:

--ADC 8" dc motor
--Curtis 1221c (400amp) controller
--Curtis 1400 (or something similar) dc-dc for my lights and items like that, which I wouldn't mind using a independent 12V battery with an alternator setup off of some sort of secondary motor output shaft to power the independent 12V battery.
--Elcon charger (i'll have to get accustomed to selecting a charger designed to charge approx. ten 12V batteries at the same time)

Now, the problem(s):

1) I'm stuck on which Ah rating I should focus on when selecting a 12V battery. It only makes sense that a larger Ah rating is better, but does this simply mean that the higher the number the more of a beating the battery will take?

2) I'd like to think that I could stuff as many batteries in the car as possible, which would be great. However, why stuff more batteries than the 8" motor and Curtis controller will handle (more batteries = more voltage)?

3) I'd like to commute with the car, and had my mind fixated on 50 to 60 miles. I have this great suspicion that i'm going to be disappointed. Hey, the lead battery route is the game I may have to play. I personally have experience with lithium batteries in other area's of trade, and I know enough about them to know that they're definitely NOT cheap.

4) What about those sealed 12V 10 to 15Ah (saw it on one of the EV supply sites) batteries that were like approx. $50 or so? Also, I couldn't imagine a billy bad Interstate battery being worth a darn. Perhaps an Optima "red top," but I just don't see that being a good idea and I see myself getting poor results.

Overall, i'm stuck on the battery deal. Most of all, I think my combo isn't going to get close to 50 miles of range even if driving easy at around 45'ish mph. I'm not looking for someone to just tell me what I want to hear. I mean, hey, let it fly. Be honest. It saves us all some time.

 

[madderscience]

Howdy-

Your basic specifications will be workable for the integra. Go with a Curtis 1231 instead of 1221 though. Higher voltage and Higher amp rating and a newer design.

Hondas (acuras) have counter-rotating engines to most everything else which means you may need to adjust the brush timing of your motor. Not a big deal, but something to remember to do.

As for the chassis, it is often said around here that if you are going to spend the time to do a conversion, do it to the BEST car you can find for the job, not necessarily the one that is already in the driveway. That said an older acura integra (aka honda accord) is not a terrible choice especially if stripped down.

It sounds like you really need to read up some more on batteries and how to calculate expected range for a given conversion. Take a stroll through the wiki and FAQ here. Make sure you understand how volts, amps, amp hours, kilowatt hours, and kilowatt hours per mile relate to each other before you do anything else.

To sum it up though, you can certainly use 12V lead acid batteries to make a workable car (you would want 12 of them for a 144V system) but you will want deep cycle batteries or traction batteries. If you are looking at optimas, this means the yellow top models (but these days, exide orbital deep cycle are considered better quality) If looking at traction batteries, there are 12V golf cart batteries out there. You will not get satisfactory long term performance out of regular starting batteries.

Also, you aren't going to get 50-60 miles of range with such a setup. Conservative driving would give up to 40 miles of range in that chassis with the golf cart batteries, and 25 to 30 miles with the orbitals or optimas.

Lithium is more expensive up front, but all signs are pointing to it being cheaper in the long run (especially compared to AGM lead acid) and you could easily install enough lithium to get a solid 50-60 mile range and still be way lighter than a lead acid conversion would be.

Good Luck.

 

[integrawow]

Thanks for the reply. After posting for the first time I did go take a look at an article that teaches one how to calculate the approximate number of lead batteries needed. This info was based on a .3 kWh per mile @ approx 35 mph (35mph means nothing since every car is geared differently) and the fact that you'd need to double the kWh of your figures since you'd want to avoid going below 50% of the battery's charge without putting the battery through hell.

So okay, let's say that I wanted to go 40 miles. Assuming .4kWh per mile at 45 mph, and assuming I went with some sort of batteries that each worked out 40 Ah @ 12VDC, i'd have:

12VDC x 40 Ah = 480 Wh, which is .48 kWh per battery.

Now, assuming again that we wanted to go 40 miles we'd have:

40 miles x .4 kWh per mile = 16 kWh.

Then, considering the "stay above the 50% theory" holds true, we have to double this figure to 32 kWh. So, at this point I should be able to figure out approximately how many batteries I need:

32 kWh / .48 kWh per battery = 66.67 or 67 batteries.

Uhhhhhhhhhh! Now the problem besides having 67 huge batteries is that we get a whopping combined voltage of:

12VDC per battery x 67 batteries = 804VDC.

Okay, this could be a problem. Perhaps this is why a larger Ah rating on the individual battery's used is so important? This car would be unbelievably heavy considering that my numbers are at least halfway realistic.

 

[major]

Now, assuming again that we wanted to go 40 miles we'd have:

40 miles x .4 kWh per mile = 10 kWh.

Math error 40 * 0.4 = 16

And you can wire the batteries in series parallel combinations to get desired voltage. Or like you say, get bigger (Ah) batteries.

Regards,

math police

 

[integrawow]

Math error 40 * 0.4 = 16

And you can wire the batteries in series parallel combinations to get desired voltage. Or like you say, get bigger (Ah) batteries.

Regards,

math police

Fixed. Whoa, now i'd need 67 of those batteries. LOL

The golf cart battery deal looks more promising. You pay a little more for them, but after only looking at them for a couple minutes I can already tell you would get a considerably higher Ah rating by going with them versus traditional lead batteries. I'd have to look into it further, but it's looking a bit more promising.

I'm wondering how long (time in minutes or hours) it would take to get a "full" charge on a pack of these. Would have to similar to the time it would take to charge a single car battery, right?

 

[major]

I'm wondering how long (time in minutes or hours) it would take to get a "full" charge on a pack of these. Would have to similar to the time it would take to charge a single car battery, right?

Simple math If you have a 200 Ah battery and a 20 Ampere charger, it will take 10 hours. Plus add an hour or so for the end of charge "top off". This assumes a complete charge and a charger which really does put out 20 A. If you have a 200 Ah battery half discharged (50% DOD), then the 20 A charge will take 5 hours, plus 1 hour.

Regards,

major

 

[jeremyjs]

Also when looking at lead acid realize that you need to replace those things after 3-5 years.

 

[Bellistner]

Yep, conventional wisdom is that PBa is cheaper now, more expensive in the long run (and if you change to Li later on, you can't re-use most of the PBa ancillaries).

 

[YohnnyLuksh]

Also, check your weather:
in low temperatures (<0 C), lead acid will lose big % of its capacity if they aren't heated!

 

[integrawow]

Would figuring out how many lithium batteries that are needed be figured with the same principles such that i'd need to consider not falling below a 50% capacity?

From what I can tell, you get the Ah needed, but the damned lithium units only pack a 3.2V punch. So in order to get 120V, we're talking roughly 38 batteries. Yikes. Well, the thundersky units are like $50 a pop online, but that's only for a 40Ah unit. Seems like i'd never reach 40 miles if I tried.

Wow.

 

[dtbaker]

ballpark:

with 120v worth of 12v batteries you won't get 40 miles except maybe under a nice warm day and when the batteries are new.

with 120v worth of 8v batteries, you may get close to 40 under perfect conditions, but you are carrying a HEAVY load and maxing out suspension and working very hard on starts and stops. Even good 8v batteries won't last more than 700 cycles most likely, even under average 50% (20 mile use) DOD.

120v worth (38 cells) of 100ah LiFePO4 will get you probably between 40-50miles at 80% DOD, which is pretty hard on them. If you can pony up a little more $$ for 160ah cells, they should last a LOT longer and have a better chance of a comfortable 40+ mile range.

I am pretty convinced that if the predicted life cycles of the Li bear out, the cost/mile of service over the life of the cells will be significantly lower than lead. But, it is a lot higher ante to get in the game...