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  #1  
Old 12-24-2016, 12:37 AM
Ocean Ocean is offline
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Default Bradley GT2 Electric Conversion

Hi All, Merry Christmas!!! Happy New Year and Best Wishes on your Journeys...

I'm Ocean. After browsing and researching and reading several interesting threads, I'm excited to introduce myself here as I am now taking my first step into the world of EV's. I've wanted to do this for sooo long, and I finally jumped into something with style that I could afford to get started with.

I'm the proud new owner of the Bradley GT2 Electric Conversion that was recently listed on the EV Tradin' Post.

The Bradley is a sporty kit car from the 70's - early 80's. A fiberglass shell built over a VW Chassis. Overall the car is in very good condition.

The Bradley came with an 8" ADC Motor, and a pack of 15 essentially dead 8-volt LA batteries (120 volt system). The vehicle also has a relatively new Logisystems 750 Amp Controller (says 120/144volts on it), and a 15 amp on-board charger with variable amp / volt controls up to 170 volts. Nice Guages with amps to 500A and volts to 150V. Batteries were arranged in custom steel cages low in the vehicle - 9 in the back (around motor) and 6 up front. As far as I understand, re-building the pack is all that I need to do to get this baby back on the road. However, some TLC will also be involved.

So my big contemplation here is the new battery pack. My main concern is range, with a secondary desire for performance, and another primary concern for longevity of the pack. I want at least 100 miles... and 200 would be much better.

According to his page, Richard Slatin's electric Bradley GT2 at evalbum/916 weighs in at 1700 pounds with 10x 13volt NiMH batteries (130 volts nom) and has a range of about 65 miles...

So, trying to figure what my curb weight will be. I don't know what those NiMH batteries weigh, but I'm going to guess about 40 pounds per each (which would be just over half the weight of LA's in the size of a golf cart, which are usually around 70lbs each)... so that's 400 pounds of batteries in his car. Subtract that and I myself have a rolling chassis of about 1300 pounds.

So back to the battery: L-ion of some type, Of course. But how. I'm looking at 24 volt Tesla Modules. (6s @ max 4.2volts = 25.2 max voltage) I feel like 5 is not enough (25.2 x 5 = 126 max voltage of the system). 6 would give 151.2 max voltage. Now my concern: is that too much for the 8" ADC??? I don't know. Research suggest that it can handle it. It's listed as a 120 volt motor, but 120 nominal on LA's is at least 130 volts... (and it seems to be some people are out there running 8" ADC motors at 144 nominal) so... I'm thinking that about 150 max voltage would be ok. Thoughts on this???

So at 5.5 Kw per Tesla module, that would give a 33KwHour Pack (say 30 KwH conservative).... which sounds pretty good to start. The modules size (about 3" thick x 27" long x 12" high standing on edge) suggests it would fit nicely in the old battery racks (10.5 wide x 29 long x plenty vertical space in the back) - I could get 3 standing on edge together in one rack, on either side of the motor. At about 55lbs per module, I'm only adding 330 pounds to the curb weight for about 1600 - 1700 pounds.

Seems like this setup should get me at least 100 mile range. Any other estimates??? Could I expect more? What's that rule of thumb??? ev-propulsion.com/ev-calculations gave a nice formula of 250 - 300 Wh / Mile for a small car. I will say that this is a particularly small car with good aerodynamics.... so if it actually got 250 Wh / Mile that would give 30000Wh/250Wh/m = 120 miles which would be excellent. And in fact, in the long run, I can see adding another 6 in parallel (4 up front and 2 more in back) for a range of 200+ miles which would be ideal. Expensive though unless I find an amazing way to get into those batteries other than saving for a couple years...

The other possibility for me is to build my own custom pack for half the cost and 50x the work. I may be up to it. Anybody have any experience with FullRiver LifePo4 individual cells? Are they reliable to their spec is my main question. Looks like I can get large volumes of these off ebay for about 1/each (26650's) - and they are 3.3Ah x 3.2 volt nom = 10.56 call it 10Wh each. So, 3000 of those would yield a 30KwH pack... built in blocks of say 75p x 40 units in series I would then have 75*3.3 = almost 250 Ah pack at 128v nominal (148 max voltage, which I like because the volt meter goes to 150). Any ideas about how these configurations would translate to Performance on the ADC 8" motor? I would love feedback on these considerations. This pack would be a bit heavier I think than the Tesla pack, but it might have a longer life because of the difference in battery chemistry... any ideas on this???

About me: I'm an off-gridder in N. California. I've lived off grid with Solar Power for the last 8 years and happily married for the most recent three+. Slowly building up our little piece of paradise out here on the land, growing food and living in a permaculture lifestyle. An EV is a natural step in alignment with our values that we're looking forward too. We use Solar Energy for almost everything. I plan to build an array to charge this car. If I can charge 100 miles of range in about 3 - 4 days that would be more than enough as I typically drive less than 50 miles per week but sometimes I need to go 100. I expect a 2kw dedicated array will do it. We get lots of sun. Ultimately I would like to have the EV drive down to visit family in the bay area which is about 200 miles. That's where the range really factors in...

Cheers!!!
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  #2  
Old 12-24-2016, 03:07 PM
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dtbaker dtbaker is offline
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Default Re: Bradley GT2 Electric Conversion

very exciting!

If it were you.... I would ditch the Pb asap consider building up a 144v or 156v nominal Lithium battery pack.

I don't know much about the Tesla battery packs, but the small format cells present a real challenge in the DIY world when it comes to balancing and monitoring multiple parallel/series strings. I would recommend you strongly consider large format LiFePO cells.... like the CALB for instance. In a nice 130ah size, you put 48 in series and you have a heck of a battery pack.

You'd have to re-program your charger, make sure your dc-dc can handle it, but little else would need to change. You'd want to design your racking in a couple sections to balance the weight. I'd recommend polyprop or ABS 1/4" sheets. It's easy to work with, easy to heat weld, non-conductive, etc.

enjoy!
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  #3  
Old 12-24-2016, 03:37 PM
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Default Re: Bradley GT2 Electric Conversion

Thanks Dan! Yes I'm very excited about it. I will indeed be going to lithium. goodbye SLA's. The CALB cells are pretty expensive though, and I want serious range - like 200 miles ultimately... and why not replicate the method used in a tesla pack? Tesla packs are built with hundreds of individual cells - like 74parallel x 6 series for a 24 volt 5.5Kw pack... Only difference is that I would be using LiFePo4 instead of LiCobalt or whatever their chemistry is. I think the parallel cells work to balance each other - and the parallel block could be balanced with other blocks in the series string. Right now I'm looking at TENERGY 5.5Ah cells (32650). If I stack a block of 80 in a 8x10 arrangement I believe I can fit them into the old rack (originally for the SLA's). If I build 40 of those in series I will have 3.2 x 40 = 128 nominal at about 440 Amp Hours which I think might actually get me the range I really want - about 200+ miles. Again, this vehicle was already converted and running on SLA's, so it has a pretty tough racking system built into - well balanced. If I did 45 in series it would be a 144 volt nominal pack... but I'm worried about giving the 8" ADC motor too much voltage.... Any idea about that? What's the max safe voltage to run an 8" ADC motor at? Thanks.... and Cheers!
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  #4  
Old 12-24-2016, 04:01 PM
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Default Re: Bradley GT2 Electric Conversion

144v nominal should be fine for the motor... remember it rarely sees peak voltage.

The CALB cells are a little pricey, BUT I think you will find that fabricating, balancing, debugging hundreds of smaller cells in parallel and series will take so much more of your time and cost for reasonable BMS that you are better off with the simplicity of 45 of the large format cells in series.

I would bet that a 144v x 130ah CALB pack will get your Bradley 60-70 miles. If you step up to the 160ah or 200ah you'll be over 100 but the car will weigh more. You need to evaluate what your actual range needed is, and build to that to keep your costs down and performance up.
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Old 12-24-2016, 04:58 PM
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Cool Re: Bradley GT2 Electric Conversion

I appreciate that - I will start thinking in terms of 144 volts nominal. As far as range is concerned... I really do want 200+ miles. I know it's heavy - but really I don't think it will be any more heavy than what the car was originally carrying - 15 x 8 volt golf carts at about 70 lbs each. Performance is again secondary. Perhaps one day I will upgrade to a 9" motor. Regarding the CALB's - to get 200 miles I believe I need a 400 AH pack and that's just too expensive.

These
http://www.ebay.com/itm/NEW-Box-of-8...oAAOSwoi1X87JG

are looking good. that's under $5k (plus shipping) for 40s x 80p x 5.5Ah * 3.2V = 56.320KwH Pack once built.

I have much more time than money. To get 400 AH of prysmatic cells would be on the order of $18-20K. Way beyond me. Used Tesla modules (12 of them) would only be $12 - 15k - a much better deal at 250AH per module (6 x 5.5Kw Modules in Series for 133v nominal, Two strings, for a total of over 60Kw Pack)... but still way too expensive for me.

Once the blocks of 80p are built, they are installed in series just like any other. I'm not afraid of batteries. I don't see a problem building a block of 80p with appropriate bars and terminals etc. So I think BMS questions will be the same as any other large format LiFePo4 setup.

I really want 200+ mile range - 220 ideally. I really do. And if I go to 45s modules for the full 144v nominal pack, at 440 Ah... that's a 63.360KwH Pack for about $5-6k in batteries... and a lot of fab time... it's sounding pretty good. At about 117 WH / Kg that's 63360/117 = 541kg = 1194 lbs which is about 150lbs more than old lead acids which were mounted in the car originally....maybe I'll keep it down to 40s....
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Old 12-25-2016, 07:44 AM
piotrsko piotrsko is offline
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Default Re: Bradley GT2 Electric Conversion

First thing: How much energy does your vehicle use in its current configuration to go a mile?

Size your pack around that. Li batteries weigh 1/3 to 1/2 of fla depending on packaging, so there is a range boost just right there. They are a lot smaller too so you can put more in the same space.

If you are low bucks, see what is available in the local wrecking yards, use that. If you score a tesla, wonderful, otherwise leafs, VW, fiats,ETC all have a lithium pack and you can sometimes score a whole donor car for the price of a battery pack. Then you could go AC with regeneration and hvac, have a 100 + mile range right off the bat.

Your car, your conversion. My $0.02, YMMV
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  #7  
Old 12-25-2016, 12:45 PM
nucleus nucleus is offline
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Talking Re: Bradley GT2 Electric Conversion

Quote:
Originally Posted by Ocean View Post
I appreciate that - I will start thinking in terms of 144 volts nominal. As far as range is concerned... I really do want 200+ miles. I know it's heavy - but really I don't think it will be any more heavy than what the car was originally carrying - 15 x 8 volt golf carts at about 70 lbs each. Performance is again secondary. Perhaps one day I will upgrade to a 9" motor. Regarding the CALB's - to get 200 miles I believe I need a 400 AH pack and that's just too expensive.

These
http://www.ebay.com/itm/NEW-Box-of-8...oAAOSwoi1X87JG

are looking good. that's under $5k (plus shipping) for 40s x 80p x 5.5Ah * 3.2V = 56.320KwH Pack once built.

I have much more time than money. To get 400 AH of prysmatic cells would be on the order of $18-20K. Way beyond me. Used Tesla modules (12 of them) would only be $12 - 15k - a much better deal at 250AH per module (6 x 5.5Kw Modules in Series for 133v nominal, Two strings, for a total of over 60Kw Pack)... but still way too expensive for me.

Once the blocks of 80p are built, they are installed in series just like any other. I'm not afraid of batteries. I don't see a problem building a block of 80p with appropriate bars and terminals etc. So I think BMS questions will be the same as any other large format LiFePo4 setup.

I really want 200+ mile range - 220 ideally. I really do. And if I go to 45s modules for the full 144v nominal pack, at 440 Ah... that's a 63.360KwH Pack for about $5-6k in batteries... and a lot of fab time... it's sounding pretty good. At about 117 WH / Kg that's 63360/117 = 541kg = 1194 lbs which is about 150lbs more than old lead acids which were mounted in the car originally....maybe I'll keep it down to 40s....
Well, if the Tenergy batteries live up to their labeling that is a big pack for the $!

That is a big IF. I would buy a set, get a powerlab 8 and test them through multiple discharge cycles to see if they ACTUALLY have 5.5 Ah of capacity.

You might want to check out jehugarcia on youtube, he is a little ignorant at times, but he has built multiple packs from little batteries.

I think you are on the right track with the LiFePO4 chemistry, you shouldn't need any cooling, and they are far less likely to catch on fire...

Sooner or later you will want to upgrade to AC. Brushes are a hassle and you gain efficiency and regen with an AC motor.

You can find salvage cars on the internet, people are crashing electric cars all the time... I recently missed a rolled i3 for $4500 in my area, that would have been a steal, 170 HP transaxle plus a 24 KwH battery pack.

Interestingly, none of the OEMs seem to use LiFePO4 chemistry...

When you build your packs, I would leave access to check each battery individually so you can find any bad ones. If they reverse that can start a fire.

I would also bottom balance every cell per EVTV.
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Old 12-25-2016, 12:48 PM
Ocean Ocean is offline
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Default Re: Bradley GT2 Electric Conversion

Thanks... good call, I will definitely start checking my local wrecking yards. That's a really good idea.

My understanding from the previous owner is that he got about 40 mile range on a new pack of 15 x 8 volt Lead Acid's.... so, yeah. Again, I'm shooting for 200+, and I do think I can get that for the same weight in Lithium's or LiFePo4's...

Merry Christmas!!!
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Old 12-25-2016, 01:03 PM
Ocean Ocean is offline
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Default Re: Bradley GT2 Electric Conversion

Nucleus I just saw your post as I was replying to piotrsko,

What does is mean "reverse" - in a LiFePo4 cell? it seems like you're implying that the polarity of the physical cell would "reverse" - is that possible? How???

Indeed, I too am concerned about the TENERGY cells living up to their claims, and have been thinking about how to test them. I will look into the PowerLab8. I think I did see one of jehugarcia's videos - making a VW Bus? Or was it a Powerwall? Yeah, good info there.

You are right I would like to upgrade to AC with regen eventually... although the idea of swapping the VW axle setup with something from a commercial vehicle seems a little daunting... maybe. That's all for much later. Maybe when I eventually build an electric truck... I have high aspirations.

Also, what do you mean by: "I would also bottom balance every cell per EVTV." I was thinking that each block would balance itself when all cells are connected in parallel.... then with a series BMS once they're all in the car hooked up together.

My guess on why the big guys don't use LiFePo4 is because it's a little heavier / less power dense than Cobalt (or whatever), and since they can do thermal management fairly easily, they take the benefit of the lighter / smaller pack.

Cheers, and Merry Christmas!
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Old 12-25-2016, 02:16 PM
electro wrks electro wrks is offline
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Default Re: Bradley GT2 Electric Conversion

Quote:
Originally Posted by dtbaker View Post
I would bet that a 144v x 130ah CALB pack will get your Bradley 60-70 miles. If you step up to the 160ah or 200ah you'll be over 100 but the car will weigh more. You need to evaluate what your actual range needed is, and build to that to keep your costs down and performance up.
I haven't seen the CALB 130Ah cells listed for several years now. AIR, in a contact with CALB, they said they were discontinuing them.
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