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Robbie (Forum Supporter)
Robbie (Forum Supporter) MegaDork
2/9/22 2:20 p.m.
frenchyd said:
Robbie (Forum Supporter) said:

I think an important topic (sorry if it has been mentioned) is safety. 

Car guys are pretty comfortable with the safety of working with gasoline. But propulsion batteries are a whole different class. 

In general, what safety gear do you need, and are there any standard procedures for connecting or disconnecting or protecting the terminals of a mega batt?

Robbie have you watched the guy on UTube who converted a 1947? Jaguar mk 4 to EV using mostly Tesla stuff?  
  While I'm never going to do that the how to was very informative without  too much, " this how you hold a wrench" stuff. 

Yeah I've watched those and that guy is great. He's also funny, which makes for some great content. 

He does have some safety precautions and tools in the videos but I feel it is something easily glossed over (right up until you're the guy who has to use a metal wrench to bolt a cable to the 2nd terminal of a 400v*zillion amp battery). 

I seem to always get some minor sparks simply connecting the 12v rock, that would scare the bejesus out of me on anything much bigger (or maybe I'd just be dead before was I even able to feel scared). 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
2/9/22 3:12 p.m.

Smallest I've found is a 250cc kid's jet ski.  It's not terrible overkill (I think it's 36hp) but it's just too heavy.  The boat is 4' x 8' and only about 12" deep.  I was hoping to find some appropriate jet drive for something like a hopped up GY6 which only weighs about 35 lbs.

Right now it has a 3.5hp outboard.  A lower unit in the water on this river doesn't last long with the craziness of rocks which was my reasoning for a jet.  The other reason that electric is so attractive to me is because the boat in stored leaned up against the garage... which is easy with a removable outboard.  I can load the boat myself in the back of the van, but I can't do either of those things with an ICE permanently mounted.  I was thinking with an electric I could yank the batteries and still flip/load myself.

But enough threadjacking laugh  Back to your regularly scheduled programming.

frenchyd UltimaDork
2/9/22 3:33 p.m.
MadScientistMatt said:

What condition would junkyard battery packs likely be in? Still have most of their service life? Not as good as new but still usable? Or are you likely to be buying the reason the car got sent to the junkyard? And is there a good way to test them before buying?

It would be just like any wrecked car. It depends on the accident.
  There is a guy ( on U Tube) who bought a wrecked Tesla and he put that in his Jaguar. Seems to be nice.  

frenchyd UltimaDork
2/9/22 3:37 p.m.

In reply to Robbie (Forum Supporter) :

Well you could do what I used to do.  Start out at the end and work towards the power source. Until you get to connecting the final hot wire. 
 Then pay for a service call to make the final connection.  He turn off the main circuit breaker made the connection and then flip back on the circuit breaker. 
      Expensive lesson but I learned. 

Chris_V UberDork
2/9/22 3:42 p.m.

A lot of of the answers can be had talking to people like these guys (confession, I have known them since the '80s): http://www.manzanitamicro.com/

They've done a lot of EV conversions and supplied parts to EV racers and hobbyists (and places like EV West) for decades. Though it's interesting their "latest news" is from 2012 (probably because Rich took some time  off to do "Alaska Off Road warriors for History), the parts and the like are quite current.

John Welsh
John Welsh Mod Squad
2/9/22 4:20 p.m.

Keith, the Maserati Biturbo might be the right chassis looking for a reliable power plant. At least that's the car I envision for an ev swap. 

Oapfu New Reader
2/9/22 4:47 p.m.

In reply to frenchyd :

Unqualified comments on safety for entertainment purposes only:
(IANAL; I have a supposedly real engineering degree but bugger-all that ever means for anything anywhere, and more accurately I flunked out but had enough credits they gave me a degree to keep up their graduation rate stats)
Terminology: a battery pack is made of up of multiple battery modules; a battery module is made up of multiple battery cells.
Along the lines of "Beware of stupid people in large numbers", or gerrymandering: battery cells are perfectly safe in small numbers, so your strategy is to keep them divided and conquered by creating separate battery modules.  You probably can give an individual battery module a full body massage with bare hands and get only a little tingling sensation (although, as SFM says, your <expletive> could still explode).
Once you connect too many modules together everything gets dangerous and, back to my original metaphor, they may try to... revolt.  Many OEM 400V battery packs (nominal-ish voltage, typical up to now for most 'modern' EVs) have a service disconnect which splits the connection between two ~200V sub groups of battery modules.   This is the awesomely named 'pyrofuse' in a Tesla battery pack.  So, the vehicle has a 12V contactor (big f'n relay) to isolate the vehicle from the scary-dangerous high voltage in the battery pack, and then the pack itself has a disconnect to internally split it into more-safe voltages.
References (yeah, I really do NOT know anything beyond what I've watched at 2x speed on YT)
Superfast Matt (the guy tesla-swapping the Jaguar); Jerry Rig Everything; Weber Auto; Damien Maguire et. al. with OpenInverter; etc etc etc
The problem is not so much a lack of info, it is mining all the existing info and making sure it is better than for entertainment purposes only. And "perfectly safe" is, of course, a reference to the short story by Douglas Adams.

frenchyd UltimaDork
2/10/22 8:23 a.m.

In reply to Oapfu :

OK I got that.  ( I think)  too much power is a bad thing.  

Oapfu New Reader
2/10/22 12:11 p.m.

In reply to frenchyd :

Too much voltage is potentially dangerous.
Power= V^2/R, so that puts voltage squarely in the "more dangerous" category.
But you are right, too much Power is bad if you become a member of the Resistance.

2/10/22 12:56 p.m.

I hope I can help answer- let me know if I'm stepping on toes Kieth.

wheelsmithy (Joe-with-an-L) said:

-how to make my own batteries. I see a lot on electric bicycle YouTube stuff where people weld/solder cells together, shrink wrap     the whole mess, and put that in a steel box, and it is supposed to be weather proof (ie, won't burn the vehicle to the ground).

For our purposes as hobbyists, to build your own battery you need:

  1. A lithium spot welder. The only 'real' difference between a lithium spot welder and a normal electronics spot-welder is that ones made for our fiery boys should have the ability to alter millisecond pulses, amperage of the weld, and use IGBTs instead of a transformer for excellent control. Good cooling is necessary- spot welders are easily made,but they need to be able to handle a lot of current and you're typical Chinese kit (NOT the K-Weld) need modification to really work well.
  2. Current conducting strips. The current (heh) meta for eBiker's is the "Copper nickel/steel sandwich"- basically, nickel strip was the compromise metal for batteries because it was the only one that had the resistance to allow itself to be welded to cathodes/anodes; copper is too conductive, and could only be attached via solder (which can put too much heat into the electrolyte and make it boil, damaging the battery). Hobbyists however found that you can "Sandwich" copper onto the terminals by using a resistive metal to force it to the head. This also has a secondary effect, as copper acts as a great heat-sink on the batteries.
  3. A BMS. You don't NEED one, but to be frank, each person who claims they don't need a management system for a lithium battery is one easily preventable fire away. A BMS Keeps them from over/under discharging like a fuse, and tactically drains cells to keep them consistent. Many now also act as your % meter for lifespan and some super-advanced ones can even tell you when it's time to replace the pack itself.
  4. Kapton tape, or some other heat and electrical resistant tape.
  5. Some kind of glue to hold them together. Hot glue is fine, so is silicone sealant. Some makers even fully pot the batteries in epoxies.
  6. A case. Some make metal boxes like you said, but really shouldn't. Water-resistant, gasketed plastic boxes are best for starting and can be easily bought from hammer stores. Some companies like Lunacycle fully pot the battery in epoxies and some people have posted their formulas online.

-What about controllers? How do they work in layman's terms?

Controllers are for DC motors, Inverters are for AC. Controllers combine voltage regulation and give it in a form of sine wave to form the magnetic field through 3-phases- pure sine is the most expensive and best seen with controllers like with Grin Technologies, whereas modified sine is cheapest but tends to have less power, torque, more heat and more noise. Those are typically your Amazon specials. Pure sine also tend to be much smaller.

-Wattage, Voltage, etc. Are cars 24V? Break down why a car battery gives a very mild shock, but an electric car is full of deadly       High Voltage.

Car batteries are low voltage, high amperage and your skin is high resistance. Electricity is like water pressure, its trying to reach an osmosis or "Base" level where it doesn't want to move anywhere. Eventually, as you pile on volts for more "speed" or "pressure", it'll overcome that resistance and you will become the easiest thing to go through. All safety with batteries is becoming the hardest path.

Voltage in DC (and partially AC but I dont understand frequency yet) directly affects speed. You CAN use transformers to increase voltage at the expense of amperage- like in your microwave- but without amps, you lack physical "oomph" to move things. Electric cars get around this by going ~400 volts (because your industrial 3-phase power is at 440v) and getting huge amperage for huge power almost as a side affect. That way, you have no efficiency losses and a drained battery in an EV doesn't feel slower than a full one.

-Safety. What is there to be afraid of (when doing a DIY electric car)?

Being the easiest way to the ground. Activating and testing a motor without it being secured to the ground AND without modifying voltage (Brushed DC runaway is NOT fun). Not being well-fused.

-How does one get weight down?

You want to do this also for efficiency, but the shortest distance from battery exit -> Inverter/controller -> Motor is best. There is a reason why the Nissan Leaf inverter is practically apart of the motor housing, and the same with Tesla- 400v+ and thousands of amps makes TONS of heat in cables no matter how well they're made. Use packaging to your advantage.

Next, cooling for batteries. They really need refrigeration, but they also don't run at "pressure"- a Tesla Y maybe runs it's coolant system at 1PSI. You could easily use plastic for hoses, and their heat exchangers tend to be smaller than radiators. Know that they don't/can't use a car radiator well as batteries don't like 100F+, and their coolants use sillicone bases instead of the salts in our standard ethylene glycol (which is also more conductive).

-Know anything about the new "glass" batteries that are supposed to be a revolution for electrics?

Nothing super-new from Mr. Goodenough. Everyone's focusing on Sodium-ion from India and CALB, and the "We totally got it now! honestly! any day now!" goal of solid-state batteries.

-Tell us more about hot rodding an existing motor. Can I just feed more electrons to that wrecked Leaf motor?

In essence yes, but eventually the electrons going the other direction in the field- called "Back EMF"- will become too much. You'll get too much heat, or it might lock the motor because it cannot overcome the field. DC on the other hand...

-Are batteries as poisonous to the environment as I imagine? Are electric cars simply the methadone to get us off our heroin (gasoline) addiction?

I'd have to pull up articles to prove this, BUT: The real 'problem' with a lot of lithium mining is, you're taking something out of the ground and you're not replacing the mass, so the ground literally sinks (just like in Germany with their coal mines). You have mining runoff but it's not much different from mining nickel and every other metal; the one heavy metal that DOES give issues is Cobalt, but Tesla gets theirs from Canada and that's only for a specific form of Lithium-ion. If you're using Lithium Iron Phosphates, you're literally using farm phosphates, lithium salt, and iron. You could genuinely mine all of that out of a junkyard.

Basically- the mining is overblown, especially versus Petroleum. It IS still a problem. Disposal is a worse issue, but more because the electrolytes (even when fully spent) can still oxidize and start fires. Recycling lithium batteries now is because it is a cheap way of getting 99% pure metals.

-Is there any need for gearing (I know transmissions are unnecessary)? 

If you call a Diff gearing- AC yes, DC maybe. DC spins at slower speeds and has more off-line torque, but AC has WAY more options available and doesn't loose speed and power with low voltage. Typically, most EV vehicles are at a minimum of 6:1 reduction. Teslas are 8:1 or maybe 10:1.

2-speeds can be a good idea for them, if you can keep efficiency up (like using a Lenco box) and can run the trans in reverse.

Keith Tanner
Keith Tanner MegaDork
2/10/22 1:29 p.m.

Quite helpful, Girthquake. My goal for this video is to sound like I know what I'm talking about, so learning as much as possible is a requirement :)

2/10/22 2:07 p.m.

Oh I forgot- DC motors you kinda CAN just, jam more electricity in and get more power out. Your real problem tho, is how that power is going in- Brushless DC will form plasma arcs that will eventually weld metals together, Brushed DC motors can take literally thousands of amps (the record holders for EV drags, and one-time fastest car ever until ~2018, were brushed DC motors) but they also can weld the brushes to the commutator or set them on fire. LonestarEV has a brushless drag car that causes these huge flameouts because it's a brushless DC motor pushing tens of thousands of amps a second, and the arcs for the magnetic fields are literally hotter than the sun and setting the goddamn air on fire.

Problem with those speeds is how you can cool them. Most motors need both the windings cooled- typically by oil- and the stator or turning shaft cooled. No bushed DC motor has been built to my knowledge for that purpose, and the only mainstream EV that uses a brushless DC motor was the EV Smart.

Keith Tanner
Keith Tanner MegaDork
2/10/22 2:24 p.m.

FYI, here's some experimental data from AEM on hotrodding Tesla motors. It's all about the power supply. I wish they'd included a picture of their dyno setup.


note for dyno nerds - these are metric units (kW and Nm) so the lines don't cross at the same RPM as they do with horses and pounds.

2/10/22 2:45 p.m.
Oapfu said:

Batteries are the Big Question, or at least the Expensive Question.
What are realistic sources for batteries, assuming you really want to spend as much under $10k as possible for 'em (possibilities?: modules made for conversions by EV specialty suppliers; used OEM modules; DIY using individual cells; is buying direct from China somehow NOT a really risky and bad idea)?

Pre-used OEM cells seem to be the best bet. All OEMs have pack-level fuses AND The major pack fuse (the Pyrofuse in Teslas) so as long as you have voltage and your battery resistance is fine- and you see no obvious damage- they should be just fine to use.

What’s the best "value" for batteries (present state, near future state; yeah, depends on what battery specs ya need)?
What batteries are semi-futureproof to design a conversion around while putting off buying actual batteries for a year or two?

Lithium Iron-phosphate has a cycle life of over 2,500 Charge-discharge cycles (i.e. 0% to 100% with no degradation) and thus, LiFePo4 packs now have lifespans over 10 years. They also have the best discharge profile partialyl thanks to their super-low internal resistance, with only one lithium cell type I know of being able to dump power faster. Problem is, LiFePO4 lacks charging speed and has lower voltage and capacity than Lithium ion, so if you do a head-to-head the phosphate packs are always bigger. They are also, because of that Iron olivine group, heavier.

Leaf batteries were the go-to at one point for not-all-out-performance applications (relatively common, relatively easy to repackage) but is that still true at all?

Decently! Nissan hasn't stopped making them, they just keep upgrading the base design I think. eBiker's would be using them more often if they weren't so pancake-ey.

Is there going to be a flood of probably-perfectly-safe ex-Bolt batteries? (Nope.)

Probably not. OEMs are gunshy about revealing much on their packs because, while legally they are not liable, COULD be drawn into one if someone was dickin' around with 400 volts for kicks. They also may want to follow Tesla's lead in not revealing many of their internal secrets. On the other hand, GM might see it prudent to openly reveal what was wrong to everyone... too many options to really say.

What is involved with upgrading or retrofiting the battery in an older OEM EV (e.g. pre-2013 Leaf, or the $5k Smart ED on autotempest which "NEEDS BATTERY WORK!”)?  Can I take a Leaf, remove the original battery and cut out the floor, and then weld in a box to hold Tesla battery modules?  Obviously I don't care about the interior of the car or being able to carry more than 1 passenger.

Pretty much! Battery modules will work even without active liquid cooling, you just need to not draw as much current from them so you don't generate as much heat. Heck, there are even kits and companies right now in the UK that have these retrofit packs for the leaf, where it just adds another +20Kw Hr lithium pack in the spare tire well and Y-splits into the main pack to add more range. The ECU even recognizes it!

frenchyd UltimaDork
2/10/22 3:14 p.m.
Oapfu said:

In reply to frenchyd :

Too much voltage is potentially dangerous.
Power= V^2/R, so that puts voltage squarely in the "more dangerous" category.
But you are right, too much Power is bad if you become a member of the Resistance.

You need a smiley face. I know just enough electronics to understand the joke.   Thanks.  

2/10/22 4:06 p.m.
MadScientistMatt said:

What condition would junkyard battery packs likely be in? Still have most of their service life? Not as good as new but still usable? Or are you likely to be buying the reason the car got sent to the junkyard? And is there a good way to test them before buying?

Genuinely? Assuming it's there from a collision, they would be pretty good. OEMs test batteries in worst-case scenarios and an EV you find in a yard is only gonna be ~10 years old max at this point- the first two steps on finding one in a yard is to see what voltage the pack should be at nominally (pretty easy) then find out what it's internal resistance it (not so much). For the second my tiny little single 18650 chargers have a method to measure it in milliohms, so a handheld voltimeter SHOULD be able to do it, so long as you know how many series and paralell cells are in each pack.

For 18650s, a Milliohm resistance reading under 80 is unused. I think LiFePO4 is under 50-40. For a single lithium-ion, "heavy" use is 250-300mOhm I think.

2/10/22 4:23 p.m.
RevRico said:

Short of welding, or making a fire, how are diagnostics different from an ICE motor?

Do you just swap the whole thing, or can the CAN/obd3/HAL system tell you something like "bad ground at terminal 3 on wheel 4" or "over voltage situation at motor 2"?

While I imagine it would be home brew software on a swap, are there diagnostic programs that would need to come from a donor or be added on to a crate purchase?

Even now, most EV problems can be found using the equivalent of a centech voltimeter. Hacked tesla modules show that their internal BMS reads individual cell resistances which ALWAYS rise before the events that can cause a fire, so genuinely anything electrical is readily diagnosed.

Curtis73 said :

Problem is, not too many jet manufacturers make anything appropriate for the 20-ish hp I'm planning. 

 I know Grin Technologies at https://ebikes.ca/ are planning on trolling motors, but theirs goes up to ~10HP. The copies of the Lynch/Agni motors from Motenergy Here are brushed, so you'd only need a very basic (and cheap) controller and have been used by channels like this one for EV Boats- the OG Lynch motor made like, 13 horsepower with some going up to 50(!). Lynch motors are berkeleying wild. Maybe that's what you're looking for?


wheelsmithy (Joe-with-an-L)
wheelsmithy (Joe-with-an-L) PowerDork
2/19/22 12:20 p.m.

I just watched the video. Thank You, Mr. Tanner.

Question for anyone able to answer: What is a Tesla cabin heater like? Coiled wires that heat by resistance? Ok, heated seats might do in a DIY, or these :


Keith Tanner
Keith Tanner MegaDork
2/19/22 12:37 p.m.

Thanks for linking that.

"Resistance heater" basically means a toaster :) They're using heat pumps now, but my car has the resistance setup. 

Oapfu New Reader
2/19/22 2:02 p.m.

+1 on the video!

So the next question: is it practical to put a heat pump into a home-built EV or EV conversion, or, how long before it becomes practical?

Using low-tech, I'd been wondering about an on-board diesel or propane heater.  Either forced air or hot water thru a traditional heater core.  It would be a combustion range-extender, except not exactly internal combustion.

For more tech analysis than you ever wanted about the latest Tesla system, search for "octovalve" on YT.

Keith Tanner
Keith Tanner MegaDork
2/19/22 3:12 p.m.

A heat pump is basically bidirectional AC from my limited understanding. It's likely in the "possible but difficult" category, like AC in an engine swapped car. The EV might be easier because you're not constrained on the location of the compressor in the same way. That would be an interesting thing to dive into.

I've seen the superbottle on my car, and a tech told me the cooling pumps can pull 30A each. We're used to stealing some of the spare horsepower from the ICE to pump things around. 

wheelsmithy (Joe-with-an-L)
wheelsmithy (Joe-with-an-L) PowerDork
2/19/22 4:18 p.m.


I'm calling a heat pump style HVAC out of the realm for most mere mortals at the moment, but the above video shows an electric AC only setup for an air cooled Porsche that sparks my interest. Apparently the same unit Singer uses, so it should be good quality. The same guy is doing a similar thing in the rear of an engine swapped Alfa that is sweet.

I also understand heat pumps can alternate from heating to cooling, then my knowledge gets thin quickly. What I know from house heat pumps is that while more efficient, they may not heat/cool as well as a conventional unit. Please don't quote me on that.  

Caperix New Reader
2/19/22 5:24 p.m.

some electric cars use an electric heater to heat coolant to run through a conventional heater core.  Electric AC compressors are common even on hybrids so it should just be finding one that matches your battery voltage.

I would be more interested in a home brew hybrid system, probably with the motor between the engine & transmission like honda/Acura use.  But that would require making sure your engine management can talk with the inverter and vice versa

MrFancypants HalfDork
2/20/22 1:12 p.m.
Oapfu said:

Once you connect too many modules together everything gets dangerous and, back to my original metaphor, they may try to... revolt

I can't be the only person who read this and laughed.

llysgennad Reader
2/21/22 1:14 p.m.

Silly question, how hard is it to switch from Rev to Fwd quickly? Can I still pull a Rockford? 

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