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Hey All, Merry Christmas!!! Mostly a lurker here but just wanted to share my new experience.

Since getting her running I've only taken her around the harbor a couple times (4-8 mile trips). But today I took her for a full 30+ mile round trip to town and I'm really excited about the results.

The Build: I picked up an old "already converted" Bradly GT 2.0 with dead batteries (of course). Such a great deal at only $1000.

She came with an 8" Advanced DC motor and a 700 Amp LogiSystems Controller (also a spare 400 amp Curtis controller which seems not to work). The car was in running condition when I picked her up, with the exception of the dead batteries.

So after scrapping the old batteries (made back almost $300 - easily covering the cost of transporting the Bradley from the South Bay Area up to my place 100m North of Sacramento - pulling it with my old 1-ton Dodge).... I started looking, and measuring, for new replacement batteries.

I finally decided on used Lithium Ion batteries from a low mileage Chevy Volt. They are about 9 inches wide at the base so they fit easily in the rack designed for golf carts - which are about 10.5" wide).. I actually got three complete Volt packs (again, really lucky to find them for about $1600 each - per 16kWh pack, delivered). One pack had about 29k miles, another 36k miles, and the third unknown mileage.

So I managed to fit 24kWh worth of Chevy Volt batteries into the Bradley - mostly into the original battery racks - which are actually very tough - it was a nicely done conversion. The Volt modules - each individual 2kW module - are 9" x 9"... so I could fit 3 of them in a row (27") in the space designed for 4 golf carts (28"). A nice tight fit. Two of these rows in the engine compartment along side the motor. Between these two rows there's a total of 12kWh - all wired as 4kWh units in parallel.

I cut the mounting plate (from one of the Volt battery packs) so I could use it to mount two 4kWh units inside the cab of the Bradley, behind the seats.

And I fit one 4kWh unit under the front hood of the Bradley where there had been some more golf cart batteries.

Each 4kWh unit is 100 volts, 47Amp Hours (The Fundamental Chevy Volt Cell Blocks are 12 Series (excepting the rare 6 Cell blocks) - so my 4kWh Units consist of 2x Chevy Volt basic units, for a total 24 cells in series). There are 6x of these 4kWh units in my build, in total, all wired in parallel.

So basically I'm running 100 volts (max voltage) at almost 300 Amp Hours.

So, my maiden voyage today:
I went 31.2 miles today (round trip total). I started out with 97.8 volts measured at the combining point (where all parallel wires come together). After my trip I measured 92.2 volts. That's a drop of only 5.6 volts. i was happily surprised, I thought it would be more.

The low cutoff is 72 volts. (24 Cells in Series, so the low is 3v per cell, and the high is 4.16 although technically I think I can go a little lower / higher - that's a pretty safe range as far as I understand for the health of the batteries). 100 - 72 volts = 28 volt range. 28/5.6 = 5 volts used in 31+ miles. 5x31 miles = 150+ mile range!!! Seems too good to be true! But even if I get 100 miles range I will be ecstatic.

I believe Lithiums run on a fairly linear scale as far as relating voltage to capacity. So I'm really excited about the potential total range of this setup.

During my trip today, I cruised at 50 - 55mph pulling around 150 - 200 amps (depending on terrain). I saw roughly 300 amps during acceleration, and 400 at certain moments. I did not push my limits. But it was very satisfying and I kept up with traffic easily. I got on the freeway for about 1 mile where I pushed it to 60mph... pulling around 200 - 250 amps up a slight grade - but being only one mile it's not conclusive how much amps will be pulled to cruise on the freeway.

So ok... all those amps! BUT Here's the kicker: Even when pulling 300 amps, each individual 100v battery (4kWh Unit - and therefore each individual cell block) only feels 50 amps. Because there are 6 of them all wired in parallel! And each one being a 47Amp Hour Battery, that means at most they each see barely 1C! And when cruising at 50 - 55, they see roughly only 0.5C! Which means my batteries are barely stressed at all. After the whole trip they did not become even warm to the touch (although admittedly it was only 50 Degree F outside when I left this morning, so the batteries were pretty cool to start out with... but again, very cool - even cold - to the touch after 31+ Miles!)

So I'm very happy with the results. My batteries will hardly ever see more than 1C. And yes they are plumbed for liquid cooling but I'll probably never need it.

This means I will get the most range possible from my setup... and the batteries will hardly ever be stressed.

But we will see. After those 31 miles the controller was only warm but the motor was pretty hot. Barely touchable. I think I need to direct some more airflow over the motor. Should be pretty easy to do that.

My next longest trip will be 40-50 miles... so I will see if the numbers are as good after the higher mileage. The furthest I need to be able to go is about 80 miles round trip... hoping!!!!

And the real win for me is this: I'm off grid, charging my car with solar power.

Merry Christmas!!!:D
 

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Ocean, I don't see any fuses in your High Voltage(HV) wiring. If the wiring is not protected by the proper fuses, a dead short between the + and - anywhere in the HV system as you have it set-up, could burn-up all the wiring and possibly destroy all the batteries.

The usual convention is to have a proper fuse as close as possible to each battery bank, near the + terminal(maybe the - also?). If a dead short occurs, each fuse will blow in succession. But, the wiring and batteries will be protected.

WolfTronix, in his My Power Controller thread discuses the potential fire risk if just one of the cells shorts in a series bank paralleled with other series banks. Since you have six banks paralleled, some of different ages (and probably different conditions) , you need to be particularly careful. Like WT says each cell in each bank should be monitored with a BMS.
 

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Hi
I'm using Volt batteries
I am abusing them a bit - 1200 amps

But I have one string of 340v - 84 S - 6 off 2Kw modules and two 1 kw modules
I'm using 4.1 v as a max and 3.5 v as a minimum

You wouldn't need the water cooling to cool the batteries but it may be useful to ensure that they are all at the same temperature
Or to cool something else - I'm essentially using my batteries to cool my controller

I've been going for about 18 months without a BMS
Just checked all my cells again all - all inside 0.01volt
 

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Discussion Starter #4
Electro you are correct and I've been thinking about just that. And in fact I just recently read through Wolftronix thread on his power controller. I'm wondering if he has those available for sale.

Can you or anyone recommend a good "affordable" BMS solution for this system? I'm a little reluctant because I would need 6x individual 24S BMS all in parallel.

If I don't hear from Wolftronix I may just find some 50amp breakers for each parallel pack.

thanks!
-Ocean
 

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Discussion Starter #5
Wow Duncan! Dang if you are pulling 1200 amps through one string that puts me a little at ease only pulling 50 per string. For how long are you pulling those amps??? Do you batteries warm up?

But I'm still interested in a cool safety device / setup. The volt packs do seem very consistent, although I did find a inconsistency in one of their modules (which I am not currently using)... I do like Wolftronix's idea because it's a cool way of managing the parallel system if nothing else.

24C and still going with all cells in balance... thanks for the perspective.
-O
 

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Hi Ocean
A LOT of battery problems have been CAUSED by BMS's - OEM ones are good but....

I'm using a Battbridge
http://www.evdl.org/pages/battbridge.html

As far as I can see the problems are that a cell fails - and with non OEM cells that is very common - This makes the "string" one cell shorter and then you effectively overcharge the string

With a Battbridge you will see if a cell has failed

With four strings in parallel you can either parallel them up at the cell level

OR treat them as four separate strings with a Battbridge on each string - I did that when I had Headway cells

My controller is set to 1200 amps
When I do my 1/8th drag the battery will see less than 1200 amps - as the revs rise it will hit 1200 amps and then as the revs rise further the motor current and the battery current will drop

I did the 1/8th in 9.2 seconds at 85mph last February - the next drag is March 4th 2018 I have some stickier tyres ordered for that

I really ought to put a battery warmer in my car - they apparently like 30C and mine have never been that warm
 

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Discussion Starter #7
Sounds like your Dragracer is lots of fun! Super Cool. Yeah I've read that too -
the BMS's sometimes inadvertently killing the batteries (maybe when they were sitting for a long time, not being charged, with an active BMS...?) Thanks for the link I will check out the BattBridge.

Cheers!
-O
 

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Discussion Starter #9
That roadster looks super fun.... so cool! I've been wondering about the forklift motors... looks like you put them to good use!
 
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