# Upgrading/Modernizing a '76 Citicar



## OR-Carl (Oct 6, 2018)

Haha, this is a really fun looking project, I am excited to see it come back to life.



xevion said:


> My understanding is that batteries like these are recyclable, and some auto parts stores will even give you an in-store credit for bringing them in.


I just scrapped a few batteries, and they are worth 0.15$/lb at my local scrap yard at the moment. Auto parts places have a core charge of about 20 bucks, which is a better deal if they will take a bunch of them for store credit.

Your assessment on what needs to be done is spot on. If all the "electronics" in the drive system are still functional, then you can probably push their replacement down the road. As long as you get back to your original battery voltage, they should work fine. Or at least as well as such a crude system ever worked . You likely have a 96v system, with 8x 12v batteries. You will be a little limited in what sort of battery you can cram into that battery box, but lithiums will give you a big boost even if they have a nominal rating that is simply equal to the lead acids they replace.

There are a couple of routes you could go for batteries. Used EV batteries are the current DIY solution of choice, as they are cheap and already really well engineered for the application. This build might be tough, as the OEM batteries are usually in fairly large modules, and obviously you will only be using a partial pack. Leaf cells might be a good fit, you will have to do some measuring though to see what would fit in that space.

Another option, that I would not suggest for a full-sized car might actually work out for your case; which is to get prismatic LFP cells. This used to be the only way to get large lithium batteries, but they are not really ideal for mobile applications. There is also some concern that when you buy small quantities online, you might be getting QC rejects.

Lastly, if you have lots of free time, this might be a good candidate for building a custom 18650 pack. This route would likely let you cram the most battery into the space, but it is a LOT of work. 

As for the motor: if it is still working, then there is really no reason to mess with it at this point. The gains from switching to AC would be very small for the amount of work and expense it would add. 

And that leads to the final point: budget. I suggest you do some research about what batteries might cost, as that will be the biggest expense for your project. Dont forget about a BMS, and a programmable lithium battery charger. Anyway, do some reading, and post more questions as they come up.


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## brian_ (Feb 7, 2017)

OR-Carl said:


> You likely have a 96v system, with 8x 12v batteries.


I assume that the batteries shown under the seat and in the driveway are the whole set, and they are eight "6V" (three-cell) lead-acid... very typical for a golf cart. So, nominally 48 V rather than 96 V.

Think "golf cart" rather than "early EV".



OR-Carl said:


> You will be a little limited in what sort of battery you can cram into that battery box, but lithiums will give you a big boost even if they have a nominal rating that is simply equal to the lead acids they replace.
> 
> There are a couple of routes you could go for batteries. Used EV batteries are the current DIY solution of choice, as they are cheap and already really well engineered for the application. This build might be tough, as the OEM batteries are usually in fairly large modules, and obviously you will only be using a partial pack. Leaf cells might be a good fit, you will have to do some measuring though to see what would fit in that space.
> 
> Another option, that I would not suggest for a full-sized car might actually work out for your case; which is to get prismatic LFP cells. This used to be the only way to get large lithium batteries, but they are not really ideal for mobile applications. There is also some concern that when you buy small quantities online, you might be getting QC rejects.


I agree.

The tougher part about using production EV modules is that they are configured for much higher voltage, so arranging for only 48 V or so means either a very small pack or having to connect modules in parallel.

Since lithium-ion cells are lower in density (mass per unit volume) than lead-acid, any replacement that fits in the same space will be lighter. It will also have more energy capacity, if it fills the space even close to as effectively.

The original batteries are likely the GC2 (yes, "golf car") sized:
260 mm long x 180 mm wide x 274 mm tall (10.24 x 7.09 x 10.79 inches)​30 kg​The same volume (about 12 litres per battery times eight batteries for about 100 litres) of lithium-ion cells would have an energy capacity of about 35 kWh, but realistically they won't likely pack that nicely.

If the space is four GC2 battery lengths long, two GC2 battery widths wide, and one GC2 battery height tall, that's
1040 m (41") long x 360 mm (14") wide x 274 mm (11") tall

A stack of 24 original-style Nissan Leaf modules would fit in there, configured 6 sets of 4 modules, with each 4 modules wired in parallel. That's half of a complete Leaf pack (the part under the rear seat of the Leaf), which is 12 kWh to 20 kWh depending on the generation of Leaf modules used.

Up to six of the VDA 355-sized modules would sit side by side with lots of space, and just four of them in the 3S4P configuration such as the LG "X590" modules available from Zero EV would add up to the right voltage and hold about 10 kWh (and weigh only 51 kilograms - or 112 pounds - compared to the original 240 kg or 530 lbs).

There are also some prismatics in other chemistries (not just LFP), and prismatics do offer the best hope for optimal packing. At least 15 kWh of NMC cells would fit, in just one layer. If LFP cells are used, about 16 of them in series (multiplied by a suitable number in parallel) would run at about the right voltage; in other lithium-ion chemistries about 12 of them in series (again multiplied by a suitable number in parallel) would be suitable.

For example, a 16S4P (64 cells, paralleled in sets of four, 16 sets in series) configuration of a LiFePO4 High Power Cell (3.2V/60Ah) from GWL (which happened to come up in another forum discussion) would provide 12.3 kWh in 109 kg, and fit easily.


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## OR-Carl (Oct 6, 2018)

Nice catch on the batteries, I looked right past the fact that there were only 3 cell caps on them!


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## xevion (Dec 26, 2020)

OR-Carl said:


> There are a couple of routes you could go for batteries. Used EV batteries are the current DIY solution of choice, as they are cheap and already really well engineered for the application. This build might be tough, as the OEM batteries are usually in fairly large modules, and obviously you will only be using a partial pack. Leaf cells might be a good fit, you will have to do some measuring though to see what would fit in that space.
> 
> Another option, that I would not suggest for a full-sized car might actually work out for your case; which is to get prismatic LFP cells. This used to be the only way to get large lithium batteries, but they are not really ideal for mobile applications. There is also some concern that when you buy small quantities online, you might be getting QC rejects.
> 
> Lastly, if you have lots of free time, this might be a good candidate for building a custom 18650 pack. This route would likely let you cram the most battery into the space, but it is a LOT of work.


Thanks for this info, getting batteries ordered is a top priority so I'll start to look into all of these options. I'm not exactly sure what kind of capacity (in kWh) I should be shooting for, but I think this will likely be dictated by the physical space I have and how much I want to spend. 



OR-Carl said:


> As for the motor: if it is still working, then there is really no reason to mess with it at this point. The gains from switching to AC would be very small for the amount of work and expense it would add.


This pretty much settles it for me, if the motor is good it's staying in.



brian_ said:


> Since lithium-ion cells are lower in density (mass per unit volume) than lead-acid, any replacement that fits in the same space will be lighter. It will also have more energy capacity, if it fills the space even close to as effectively.
> 
> The original batteries are likely the GC2 (yes, "golf car") sized:
> 260 mm long x 180 mm wide x 274 mm tall (10.24 x 7.09 x 10.79 inches)30 kgThe same volume (about 12 litres per battery times eight batteries for about 100 litres) of lithium-ion cells would have an energy capacity of about 35 kWh, but realistically they won't likely pack that nicely.
> ...


I really appreciate the detailed response. I'm looking forward to seeing how the reduced weight effects things, those golf cart batteries are so heavy. How much does delivery factor in to the cost of batteries? I can't imagine it's cheap to ship them. Does it make sense to try to look for local ev sellers? I'm located in New England for reference.



OR-Carl said:


> Nice catch on the batteries, I looked right past the fact that there were only 3 cell caps on them!


I made the same mistake.


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## xevion (Dec 26, 2020)

Spent a good 8 hours getting things cleaned and disassembled today. Here are some of the highlights:








Pulling the original charger out. It really is just an off the shelf golf cart battery charger shoved under the dash. I may look to sell this since it works.








The batteries that were in there were really nasty, some baking soda confirmed they were covered in battery acid. Yuck.








Could this duct tape be.....factory? It's goes between the frame the body, and I can't see how someone would have gotten it in there unless the two were separate.








The vent tubes under the dash just fell apart in my hands. They should be easy to replace.








Found some vacant wasp homes under the dash. These were fun to take out, especially the one on the left which was built on top of a circuit board.




Here's a close up look at the mechanism that runs the 3 position pedal. The first click runs the 48 V pack as 2 24V packs in parallel, and then runs them through a resistor. The second position takes the resistor out of the equation. The third gives you the full 48V. I'm thinking it's going to be easier to just get a modern motor controller instead of shoehorning a modern pack to work with this system. That being said the car is wired to work like this right now, so maybe I should give it a try. Thoughts?















The previous owner did some work on overhauling the old hydraulic brake system, which is awesome. Less awesome is this homemade parking brake setup zip screwed to the bottom of the car, which doesn't seem to actually function. 















The rear drums actually don't look that bad, but I can't seem to figure out why the e brake cable won't engage the brake shoes. More investigation is required. Also this stack of washers looks a little suspicious. 








This is the air intake to the motor. Luckily there is a grate preventing this stuff from getting sucked in, but it being here doesn't inspire lots of confidence.


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## xevion (Dec 26, 2020)

Here's the blower that keeps the motor cool. That second picture is what's left of the impeller. Good thing blower motors are easy to come by. Might also try to 3D print another impeller since the motor seems to work just fine.


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## OR-Carl (Oct 6, 2018)

xevion said:


> Does it make sense to try to look for local ev sellers?


Yeah, I would definitely look. You might start prowling the local craigslist for EV Batteries; thats how I found my pack. It was an outfit that specialized in replacing and refurbishing hybrid battery packs, so they no doubt had a bunch of contacts keeping an eye out for batteries to salvage. I see an ad all the time for a place that does Nissan leaf battery upgrades, and that might also be a good bet for tracking down a partial pack. I do not have experience with getting batteries shipped, but I do know it is possible.



xevion said:


> I'm thinking it's going to be easier to just get a modern motor controller instead of shoehorning a modern pack to work with this system. That being said the car is wired to work like this right now, so maybe I should give it a try. Thoughts?


Yeah, I am starting to think that a new controller might not be a bad idea. 48 volts seems like it is just going to be a hassle to deal with. Parallel stings should really be avoided if possible. It will greatly simplify your BMS - which you should include with just about any lithium battery pack. And reconfiguring a pack would be a lot of work if you are going to plan on putting in a new controller later anyway. Anyway, I like the pictures, do you have any more of the motor (and what its approximate dimensions are?)


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## xevion (Dec 26, 2020)

OR-Carl said:


> Yeah, I am starting to think that a new controller might not be a bad idea. 48 volts seems like it is just going to be a hassle to deal with. Parallel stings should really be avoided if possible. It will greatly simplify your BMS - which you should include with just about any lithium battery pack. And reconfiguring a pack would be a lot of work if you are going to plan on putting in a new controller later anyway.


As much as I want to slap two 24V packs in here and get this thing on the road, I want to do it right the first time even more. I'm thinking it might make sense to start with what the motor needs and work my way back. Size a good controller for the motor, then a good pack for the motor controller.



OR-Carl said:


> do you have any more of the motor (and what its approximate dimensions are?)


This is the best shot of the motor from today, I'll grab some more next time I'm under there. I had the motor info somewhere but I can't find it at the moment. I think this is a 3.5hp GE motor.


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## MattsAwesomeStuff (Aug 10, 2017)

I wouldn't toss your golf cart charger.

I'd use it to charge your lithiums.

Just know that "48v" of lead acids can be as high as 60v. I would put a capacitor across the output of the charger and measure its voltage when turned on. You'll see the peak to which the charger actually charges. Size your lithiums to be slightly higher voltage than that, and they'll never overcharge. It's probably just a big dummy transformer with magnetic shunts to limit the max current (lead acid batteries too are an almost bottomless current sink when empty, the charger will have to gracefully limit the current so, no issues there).

A BMS... you could get away with a low-power e-bike or scooter BMS, if you need to use one at all. For how few cells you have, ~13 or so, I would be tempted to just buy 13 little 1/2" tall panel meters for $1 apiece, mount them to a sheet of plastic or wood, and give them a glance once in a while before driving to make sure they're roughly equal. Else, just top up the weak ones manually. This is what many e-bike builders do. With low cell counts, you have low likelihood of imbalance.

Speed control... lots of low voltage golf car controllers available on the cheap. Nothing fancy needed.

Damien's had a dead simple Prius DC controller brain on the backburner for a year or more, but if that ever gets fleshed out it would be more power than you'd ever use for something around $300-ish including the Prius inverter.

The thing I love about these cars is that they're so simple, and so terrible, that anything you want to do you can do, and it improves the car


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## wjbitner (Apr 5, 2010)

MattsAwesomeStuff said:


> I wouldn't toss your golf cart charger.
> 
> I'd use it to charge your lithiums.
> 
> ...


Hi Matt!

Not to quibble, but.. 


> Size your lithiums to be slightly higher voltage than that, and they'll never overcharge.


If it's truly a big transformer, then the output voltage is dependent on the line voltage, which can vary significantly. The only guarantee is that the frequency will average to 60 hz. Even that
varies somewhat. Just wanting to be a little cautious, since some lithium's will burn quite energetically if over-charged..

Hi xevion:

Since your top speed is probably limited to ~40-45 mph, and your desired range is 50 miles (what's your desired budget?) I'd look for 2 Telsa packs which should give you ~10Kw, and then consider two more if needed for your range goals. Of course you have to figure out where they will fit..  Fun project!


Bill


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## xevion (Dec 26, 2020)

MattsAwesomeStuff said:


> A BMS... you could get away with a low-power e-bike or scooter BMS, if you need to use one at all. For how few cells you have, ~13 or so, I would be tempted to just buy 13 little 1/2" tall panel meters for $1 apiece, mount them to a sheet of plastic or wood, and give them a glance once in a while before driving to make sure they're roughly equal. Else, just top up the weak ones manually. This is what many e-bike builders do. With low cell counts, you have low likelihood of imbalance.


I do like the idea of keeping things simple, as long as it's not at the expense of safety.



MattsAwesomeStuff said:


> Speed control... lots of low voltage golf car controllers available on the cheap. Nothing fancy needed.


Yea I'm hoping to be able to pick one of these up second hand, just need to figure out how big the motor is so I can size the controller appropriately. 



wjbitner said:


> some lithium's will burn quite energetically if over-charged


Yea this is something I definitely want to avoid. From what I remember the stock charger is just a huge transformer, I'll take a closer look tonight.



wjbitner said:


> Since your top speed is probably limited to ~40-45 mph, and your desired range is 50 miles (what's your desired budget?) I'd look for 2 Telsa packs which should give you ~10Kw, and then consider two more if needed for your range goals. Of course you have to figure out where they will fit..


The speedo only goes up to 45, stock these things maxed out at ~35. My range will probably dictated to a certain extent by my budget. I'm hoping to keep the battery/bms/charger under $2k, but maybe that's just not realistic. A quick google puts tesla packs at around $800-$1000 so that might be an option. Some back of the napkin math puts the capacity of the original pack at ~10KW (and 500lbs). The original batteries were rated at a range of around 40 miles. What's needed to charge/maintain 24V tesla modules? 

Original pack calculation:
200Ah @6V = 1200 Wh * 8 batteries = 9600 Wh


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## brian_ (Feb 7, 2017)

wjbitner said:


> ... I'd look for 2 Telsa packs which should give you ~10Kw, and then consider two more if needed for your range goals.


Of course this don't mean two Tesla _packs _(which would be heavier than the car), but two Tesla Model S or Model S *modules*.

These are 6S modules, so nominally 22.5 V per module (but over 24 volts each at full charge).


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## xevion (Dec 26, 2020)

brian_ said:


> Of course this don't mean two Tesla _packs _(which would be heavier than the car), but two Tesla Model S or Model S *modules*.
> 
> These are 6S modules, so nominally 22.5 V per module (but over 24 volts each at full charge).


Haha yes, my mistake. 2 modules, not packs.

Sent from my Pixel 3 using Tapatalk


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## OR-Carl (Oct 6, 2018)

xevion said:


> What's needed to charge/maintain 24V tesla modules?


First off, have you measured that space under the seat? Most Tesla modules are big.

As for charging, and this goes for nearly all lithiums, It depends how risk averse you are. Overcharging lithium cells is bad news, and discharging them too low is also to be avoided. The safest way to do it is to have a BMS that monitors each cell in your battery, and reports that info over CAN a couple times a second. Then you have a CAN enabled charger that reads those messages and adjusts the charging current based on SOC. As soon as the first cell gets to your user-defined cut-off, the charger shuts itself down. At the same time, the BMS should be checking for cell imbalances and bleeding down the highest voltage cells to get all the voltages to match. 

I personally would be very nervous to plug a dumb charger into a 10kwh bank of lithium cells and walk away. Under charging the bank would add a margin of safety, but you are then buying and hauling more battery than you are using. You also end up having to decide how many extra miles you are willing to wager in a game of "will-this-voltage-burn-down-my-car-and-maybe-garage/house." LFP cells, which do not experience thermal run-away, would be safer without a BMS. Still, over voltage can ruin the cells. I would think of a BMS as an insurance policy. A 24 cell bms from Thunderstruck is like 450 bucks, which would get you to about a 90volts-nominal system. It can tie into a CAN-enabled charger, or control a relay if you want it just to use it to disconnect a dumb charger. This may all sound like paranoia, but catching an e-bike battery on fire is not the same thing as lighting up a few hundred pounds of lithium cells inside a vehicle.


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## brian_ (Feb 7, 2017)

xevion said:


> What's needed to charge/maintain 24V tesla modules?


They're 22.5 volts nominal, not 24 V.

In a Tesla (as in any other EV), the modules are managed by a BMS (battery management system) which monitors module temperature and the voltage of each group of parallel cells, tells the charger what rate to charge at, tells the charger when to stop, tells the motor controller how much power it can use, and balances cell groups by partially discharging the most-charged groups to bring them down closer to the voltage of the other cell groups.



xevion said:


> Original pack calculation:
> 200Ah @6V = 1200 Wh * 8 batteries = 9600 Wh


Ideally, yes, but that 200 Ah capacity is for very slow discharge (over 20 hours, which is 10 amps for a "200 Ah" battery, so about 480 watts for the whole 8-battery 48-volt set). Useful capacity in a car will be a fraction of that.


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## xevion (Dec 26, 2020)

OR-Carl said:


> First off, have you measured that space under the seat? Most Tesla modules are big.


Took some quick measurements, very conservatively the space I have to work with is 15"x43"x9" (l*w*h). A quick google puts the tesla packs at ~12"x27"x3" so I should be good for two packs should I choose to go that route. The photos below measure the height, length and width respectively at the narrowest spots.


























OR-Carl said:


> I personally would be very nervous to plug a dumb charger into a 10kwh bank of lithium cells and walk away. Under charging the bank would add a margin of safety, but you are then buying and hauling more battery than you are using. You also end up having to decide how many extra miles you are willing to wager in a game of "will-this-voltage-burn-down-my-car-and-maybe-garage/house." LFP cells, which do not experience thermal run-away, would be safer without a BMS. Still, over voltage can ruin the cells. I would think of a BMS as an insurance policy. A 24 cell bms from Thunderstruck is like 450 bucks, which would get you to about a 90volts-nominal system. It can tie into a CAN-enabled charger, or control a relay if you want it just to use it to disconnect a dumb charger. This may all sound like paranoia, but catching an e-bike battery on fire is not the same thing as lighting up a few hundred pounds of lithium cells inside a vehicle.


Yea if I choose to go lithium I'm definitely not going to skimp when it comes to battery safety. A fully CAN-enabled setup may be beyond what's needed for this project, but we'll see.



brian_ said:


> Ideally, yes, but that 200 Ah capacity is for very slow discharge (over 20 hours, which is 10 amps for a "200 Ah" battery, so about 480 watts for the whole 8-battery 48-volt set). Useful capacity in a car will be a fraction of that.


Makes sense. This means my conservative estimate for the original battery capacity was even more conservative then I thought.


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## Electric Land Cruiser (Dec 30, 2020)

Cool project! Nice find I have seen several of these but none as in good of shape as that one. Way cool that the original batteries still held a charge, that is really amazing.

A couple points about resurrecting vintage EVs I've learned that may help you:

-The battery bank is 48V nominal, but that means it probably has a max voltage of 60V and a minumum of 40V. You need to know what the minimum voltage cut-off is before choosing your lithium pack, or at least it's a good idea. For instance you might think "I want a 14S lithium pack because that gives me a nominal 48V!" but the lithium can be discharged much further than lead-acid, and most of the lithium's energy is in the bottom half vs the top half of the voltage curve. So the car will shut down at 40V but the 14S lithium pack can still be used down to 35V so there's energy left on the table. In this case you could go with a 15S or even 16S lithium pack and just make sure to keep the maximum voltage to 60V max and end up with more range.

-Like others I would be wary of a 45 year old charger, however if you test it rigorously enough there's no reason it cannot be used with a new lithium pack. Of course, no matter what you need a BMS for your lithium pack, but there's no reason you can't charge the pack with the original charger as long as the voltages are all compatible. You'll likely want a more modern charger at some point though, as you'll have way more capacity than stock to recharge and also probably want the option to use public charge points.

-Figure out what the motor is. Take some photos and run the model numbers. That will dictate whether you should try to keep the original controller (probably not) or get an aftermarket one. Will also dictate if you can increase voltage above 48V for more power or replace with a different motor.

-Luckily a 48VDC car is very similar to golf carts as brian_ mentioned so things like motor controllers, chargers, DC-DC converters, even Sepex motor controllers are all readily available and cheap!

Good luck resurrecting this little goofy car! Can't wait to see what it can do with modern tech.


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## MattsAwesomeStuff (Aug 10, 2017)

wjbitner said:


> If it's truly a big transformer, then the output voltage is dependent on the line voltage, which can vary significantly.


True, regardless, you would want a simple high voltage cutoff. No reason not to, it's simple, you already have contactors, and it will prevent 99.99% of rare problems.

Heck, I think even something dumb like a UPS charger would have that built in.

No need for fancy charging profiles or any of that BS. Feed it voltage lower than it's max voltage, have the power supply limit itself so it doesn't overheat, and let it charge.



> The only guarantee is that the frequency will average to 60 hz. Even that varies somewhat.


Form what I understand, frequency is so consistently 60hz that clocks have run on AC based on this frequency for decades without needing adjustment. It takes things like, Texas' entire power grid failing for that to fail.



OR-Carl said:


> The safest way to do it is to have a BMS that monitors each cell in your battery, and reports that info over CAN a couple times a second.


That would stop a somehow random, spontaneous, catastrophic failure of a battery module, but is otherwise in my opinion absurdly paranoid. For an OEM concerned with liability and the most irresponsible owner, yes. See: Almost every ruined DIY EV has a story that goes "I lent it to someone and told them how to use it, but they ...". But for a DIYer? Not really practical.

OEM batteries don't just randomly, wildly start drifting apart while driving (or any other time). Has this ever happened, even once?

And if it does happen, the BMS isn't saving it. Best it can do is blow the canopy and eject, shut everything down. A BMS trickle isn't going to recover a failed cell.

Yeah, over an entire season and different weather conditions, many charge/discharge cycles, gradually, perhaps cells in a module could slightly drift apart, and some would need to be occasionally given a little burp of charge.

A crappy little passive BMS (not one that the whole driving circuit goes though) would keep these topped up. So, I would go with one of those, not a big vehicular-sized one if you didn't want to have to monitor them.

But like I said, on such a little vehicle, I'd almost just make a little column of panel meters to watch the voltage now and then.

A better backup, and a better sign of any looming catastrophic failure, is to have temperature sensors and cutoffs. A failing pack is a hot pack.



> I personally would be very nervous to plug a dumb charger into a 10kwh bank of lithium cells and walk away.


It's up to everyone's choice. But, a good rule of thumb is to have a consistent level of paranoia, and to tackle the low hanging fruit across the entire project. At some point you'd be paranoid about not spending extra on special extra-durable tires or taking your suspension in for regular checks, etc, perhaps before you'd bother with this. Or you wouldn't drive it at all if you care about safety. What do you think the survivability is when this plastic cheese wedge gets into even a minor crash? It's going to crumple like saran wrap and tumble like dice on a craps table, it's no longer than it is tall or wide! Instead of spending $2000 to upgrade it, for $500 you can buy a used 90s Honda Civic that's, I don't think I'd exaggerate to say 10-100x as safe.

For the extra cost of a vehicular-scale BMS, I'd say just throw more batteries in and then undercharge them so there's even more overhead.



Electric Land Cruiser said:


> most of the lithium's energy is in the bottom half vs the top half of the voltage curve.


Mmm... no. It's almost all fairly steadily right around 3.7v. Something like 80% of it is 3.6-3.8v. Discharge curve is quite flat.



> So the car will shut down at 40V but the 14S lithium pack can still be used down to 35V so there's energy left on the table.


I pretty strongly disagree with this point.

35v / 14 cells = 2.5v per cell.

That is not a smart discharge level for lithiums, nor is there any useful power to discharge that low.

40v / 14 cells = 2.85v per cell.

Even that is pretty low for lithium and most people will not let their batteries discharge that far. There is certainly all-but-zero energy left below 2.85v per cell.

42v might be a smarter discharge cutoff for most people. The difference energy between 42 and 40v is also nearly zero. It plummets fast.

Heck there's people who set their lower limit to 3.3v, (46.2v), which itself is like, 90%+ of the energy.

Also, the dash will almost certainly have a volt gauge on it that the driver would occasionally glance at, to make their own determination of their range. With such a short range vehicle, your mind is always partially on how much range you have left. The alternative being that the car would suddenly cut out mid-trip, and, you think it's best to beat the cells down to 2.5v before being forced to shut off? I don't think that's wise or useful.



> Of course, no matter what you need a BMS for your lithium pack


"need" is a strong word. Lots of DIY EVers never did, most E-bike builders don't either.

He's really not using that much more battery than an E-bike or a scooter.

To travel 45mph (pegging the gauge), it would use ~92 Wh/mile. If he wants a 50 mile range that's only 4600 Wh.

To travel the speed the vehicle was built for (35mph), it would use 75 Wh/mile. 50 mile range means 3750 Wh. That's only a 4-slice toaster volume of battery. It's 375x 18650s.



xevion said:


> I'm thinking it's going to be easier to just get a modern motor controller instead of shoehorning a modern pack to work with this system. That being said the car is wired to work like this right now, so maybe I should give it a try. Thoughts?


Your best money is probably spent on the controller, more so even than upgrading the batteries.

That said...

Half the reason most people do things is for the narrative of it.

If you just wanted the end result you'd buy... literally any other car ever made 

I think a fun part of the stories you'd tell about this project, would be how awful it was to drive with the default 3-position speed controller. Don't keep the controller, but, do you want to miss out on the story of knowing what it was like to drive it the way it was built? I'd drive it for a few days at least so you can pick up some memories and situational context.

There's almost nothing to break. It's series/parallel contactors, and a resistor. That's your 3 speeds. No transistors allowed. Heck, I'd keep it around in the vehicle as a speed controller spare-tire kind of thing.

One of the nice things about EV builds is that your setup is modular and agnostic to the rest of the system. If you want to add battery capacity later, you can. If you want to upgrade the speed control, you can. If you want to upgrade the dash, you can.

You're looking at under 100 amps. Probably under 50 amps unless you're climbing a hill or accelerating. Almost any little used golf cart speed controller is going to be excessive for this. I wouldn't spend a lot of money here.


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## brian_ (Feb 7, 2017)

I think in all of these cell voltage discussions everyone should be careful about which lithium-ion electrode chemistry they are discussing. LFP (LiFePO4) voltages are significantly lower from most of the others.


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## brian_ (Feb 7, 2017)

MattsAwesomeStuff said:


> One of the nice things about EV builds is that your setup is modular and agnostic to the rest of the system. If you want to add battery capacity later, you can. If you want to upgrade the speed control, you can. If you want to upgrade the dash, you can.


But it's not, really. At the very least, the system voltage matters to every power-handling component. You can't just swap a nominally 48 volt battery with a nominally 360 volt battery like nothing else (such as the controller) will care. I do agree that once an operating voltage range is established, components can be changed individually to a significant extent.


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## xevion (Dec 26, 2020)

This morning I turned my 460lbs of lead and sulfuric acid into $106 cash at the scrapyard.








Cleaned up some stuff in the citicar as well, and snapped a pic of the motor ID plate. Some surprising specs on here, the motor seems to be designed for 36V and I believe the INT signifies intermittent use. I'm not sure if this is going to change my approach to batteries, I still may go with a 48V pack, but it's nice to know I have some flexibility.


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## brian_ (Feb 7, 2017)

That's presumably the original motor - it exactly matches an EV Album listing for a "1976 Sebring Vanguard Citicar". 

The nameplate values of 98 A @ 36 V correspond to 3528 W or 4.7 HP (input), which makes sense with the 3.5 HP output rating. "INT" suggests intermittent to me, too.

From what I have learned about GE DC motor naming in the past few minutes, the entire "5BC 49 JB 320" string is the model identification, and this plate doesn't have a serial number.


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## xevion (Dec 26, 2020)

Electric Land Cruiser said:


> The battery bank is 48V nominal, but that means it probably has a max voltage of 60V and a minumum of 40V. You need to know what the minimum voltage cut-off is before choosing your lithium pack, or at least it's a good idea. For instance you might think "I want a 14S lithium pack because that gives me a nominal 48V!" but the lithium can be discharged much further than lead-acid, and most of the lithium's energy is in the bottom half vs the top half of the voltage curve. So the car will shut down at 40V but the 14S lithium pack can still be used down to 35V so there's energy left on the table. In this case you could go with a 15S or even 16S lithium pack and just make sure to keep the maximum voltage to 60V max and end up with more range.


I'll definitely keep this in mind. Ideally I'd like to have easy control over the max/min levels for the pack (what voltage corresponds to 100% vs "0%" state of charge).



Electric Land Cruiser said:


> You'll likely want a more modern charger at some point though, as you'll have way more capacity than stock to recharge and also probably want the option to use public charge points.


What options are there out there for enabling the use of public charge points? My assumption would be that these types of chargers use standard safety protocols that prevent just anyone from plugging /charging anything.



Electric Land Cruiser said:


> Luckily a 48VDC car is very similar to golf carts as brian_ mentioned so things like motor controllers, chargers, DC-DC converters, even Sepex motor controllers are all readily available and cheap!


It seems like lots of people go with some sort of golf cart motor controller when upgrading these vehicles. I haven't heard of sepex yet, but from a brief ebay search it seems like they can be had for less then $200 with is great.


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## Electric Land Cruiser (Dec 30, 2020)

@MattsAwesomeStuff yes I was not talking specific voltages but just generally that when considering pack voltage the minimum voltage is just as important as maximum. Probably should have made that more clear.

@xevion to use most public L2 charge points you just need a J1772 plug and a subscription to their service, there is no handshake protocol for those chargers and they put out ~240VAC, same as a home L2 EVSE. Can charge much, much faster than using the 120VAC plug that it has now.

You do not actually need a Sepex controller however, looking at your motor you want a "series" motor controller which is also commonly available.


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## xevion (Dec 26, 2020)

Electric Land Cruiser said:


> You do not actually need a Sepex controller however, looking at your motor you want a "series" motor controller which is also commonly available.


Yea I'm looking into something along the lines of this. These Curtis/Curtis clone controllers seem like a good value and seem fairly straightforward to wire up/ program.


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## xevion (Dec 26, 2020)

I've got my eye on these 48V 2.2kwh LG server rack modules from battery hookup. $100/kwh is pretty sweet, and if I disassembled them into two sub-modules I bet I could squeeze them under the seat, but I'll have to take some better measurements. I'd probably grab 2 or 4 of them, depending on how much space I have.

They do seem pretty degraded, and might need to be reconfigured to work well though...


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## brian_ (Feb 7, 2017)

xevion said:


> What options are there out there for enabling the use of public charge points? My assumption would be that these types of chargers use standard safety protocols that prevent just anyone from plugging /charging anything.


True, but you can buy equipment to work with the SAE J1772 standard for AC charging of EVs, which is used at both public charging stations and home charging points for production EVs.


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## summetj (Mar 30, 2011)

For example, this kit bundles a J1772 inlet with a charger and EVCC that will interface with a BMS to turn the charger off if any cell voltage hits the maximum:






Chargers :: TSM2500 & EVCC with J1772


Programmable battery charger




www.thunderstruck-ev.com





Jay


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## brian_ (Feb 7, 2017)

xevion said:


> I've got my eye on these 48V 2.2kwh LG server rack modules from battery hookup.


It's either amusing or sad that these are described as "48 V", given that according to the specs provided in the listing they are 14S in something other than LFP, and as a result have a nominal voltage around 53 volts.



xevion said:


> ... if I disassembled them into two sub-modules I bet I could squeeze them under the seat, but I'll have to take some better measurements.


It looks like they readily break down into 1S2P cell groups with bolted connections between them so they can be configured as desired. The length of the group fits into the width of the housing, which fits in a "19 inch" rack, which is actually 17.75 inches (450.85 mm) between the vertical rails. Two groups end-to-end would fit in the battery compartment, but if you can only get two groups per layer you could only fit in two modules worth (4 times 7S2P, which could be rewired as 14S4P), which wouldn't be much energy (4.4 kWh as listed, 6.2 kWh nominally if they still had 30 Ah capacity per cell).


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## brian_ (Feb 7, 2017)

Electric Land Cruiser said:


> @xevion to use most public L2 charge points you just need a J1772 plug and a subscription to their service, there is no handshake protocol for those chargers and they put out ~240VAC, same as a home L2 EVSE.


There is a simple handshake, as there needs to be, under the J1772 standard. It uses signals on the pilot and proximity terminals of the plug.


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## Bramman (Apr 16, 2021)

I just saw this project, I recently bought one and am restoring it. This one looks in really good shape. There are two main facebook groups(C-car and Vanguard Citicar Registry) were there is a lot of good information or if you have any questions. A lot of people have been using 48V chevy Volt Modules and running 4 in parallel. Lastly just as a good rule, before you start driving it, but real tires and not just trailer tires even though they are about 1/4 the price this will greatly increase drivability and comfort.


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## brian_ (Feb 7, 2017)

Bramman said:


> A lot of people have been using 48V chevy Volt Modules and running 4 in parallel.


There are no 48 volt Chevrolet Volt modules, but there are seven 12S3P modules in a first-generation Volt battery (plus two 6S3P), all bolted together with other modules. A second-generation Volt battery has four 12S2P modules (plus three 16S2P), again all bolted together with other modules. The cells of the two generations have different capacities, so the 12S modules have about the same energy capacity in either generation.

A 12S module of the NMC-LMO LG Chem cells used in the Volt has a nominal voltage of 45 V, so the operating voltage range is relatively close to that of a nominally 48 volt lead-acid battery.


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## xevion (Dec 26, 2020)

Bramman said:


> There are two main facebook groups(C-car and Vanguard Citicar Registry) were there is a lot of good information or if you have any questions. A lot of people have been using 48V chevy Volt Modules and running 4 in parallel. Lastly just as a good rule, before you start driving it, but real tires and not just trailer tires even though they are about 1/4 the price this will greatly increase drivability and comfort.


I'll be sure to check out these groups. Upgrading the tires didn't even occur to me, but that makes a lot of sense.


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## xevion (Dec 26, 2020)

Just picked up two of these modules for this project. Glad to have the largest piece of the puzzle out of the way. Based on my measurements they should fit well, maybe even well enough to fit two more in the future should I want more range. Now I'm on the hunt for a beefy 7S BMS that can handle ~200-300A peak. Anyone have any suggestions? Also I want to start thinking about how I'm going to keep those batteries at a happy temperature under use.

I am having some trouble finding good spec listings for those modules, I can't seem to find examples of others using them, maybe because they are so new.

Anyway, battery tech is just amazing. Those two modules alone should give me nearly the original capacity, at less then a quarter the weight.


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## brian_ (Feb 7, 2017)

xevion said:


> Just picked up two of these modules for this project.
> 
> I am having some trouble finding good spec listings for those modules, I can't seem to find examples of others using them, maybe because they are so new.


That's one of the three different sizes of module found in the 62 kWh battery of the Leaf+:

7S3P (four per pack)
4S3P (eight per pack)
9S3P (four per pack)
The only example of anyone using the Leaf+ 62 kWh battery that I can think of is Rockcrawler and his race 4Runner:

Differences in dimension between 24kwh and 62kwh Nissan Leaf battery modules
Toyota 4Runner 4x4 Race truck Leaf conversion
... although others have discussed the possibility.

Those discussions provide illustrations and dimensions of the modules. That project uses an entire pack, but packages the modules differently.

The 62 kWh Leaf+ battery appears to use the same cells as the current generation base Leaf's 40 kWh battery, just in a 96S3P configuration (split into the listed modules) instead of the Leaf's traditional 96S2P configuration (in the Leaf's traditional 48 identical 2S2P modules). So any specs which apply to the cells of the 40 kWh battery also apply to the cells in these 7S3P modules.

7S of the 96S of the Leaf+ pack is 7/96= 7.3% of the voltage, and the same fraction of the energy (4.5 kWh), and the same fraction of the power. The Leaf+ has a 150 kW motor, so a single module can certainly handle 11 kW for reasonable periods (at least a few seconds at a time of acceleration). That's 14.6% of the pack or 9 kWh and 22 kW, at 52.5 V nominal, for two modules.


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## xevion (Dec 26, 2020)

brian_ said:


> That's one of the three different sizes of module found in the 62 kWh battery of the Leaf+:
> 
> 7S3P (four per pack)
> 4S3P (eight per pack)
> ...


Thanks for all the background info/links! I'm currently looking at the Daly BMS offerings, I think some of there largest ones (14S, 48V, ~250A) might be well suited for my needs. I'll probably make a post in the appropriate sub-forum and see what people suggest.


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## Electric Land Cruiser (Dec 30, 2020)

I found a Daly on Alibaba and was able to get a 500A discharge/250A charge BMS from them built to order for exactly my pack config. Been using that site more and more always had good luck as long as I talk with a rep first.


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## xevion (Dec 26, 2020)

Electric Land Cruiser said:


> I found a Daly on Alibaba and was able to get a 500A discharge/250A charge BMS from them built to order for exactly my pack config. Been using that site more and more always had good luck as long as I talk with a rep first.


That's awesome, that setup looks pretty similar to what I'd be looking for. How much was it if you don't mind me asking? What had to be customized to fit your setup? Does that BMS include any thermal regulation?


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## Electric Land Cruiser (Dec 30, 2020)

xevion said:


> That's awesome, that setup looks pretty similar to what I'd be looking for. How much was it if you don't mind me asking? What had to be customized to fit your setup? Does that BMS include any thermal regulation?


It was $440 including 3 day DHL shipping. It has a thermal protection for the BMS itself, but it doesn't have any input for battery temperature.


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## xevion (Dec 26, 2020)

Electric Land Cruiser said:


> It was $440 including 3 day DHL shipping. It has a thermal protection for the BMS itself, but it doesn't have any input for battery temperature.


I think I'm going to go with a DALY BMS similar to the one you purchased. How did you get in contact with the company?


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## Electric Land Cruiser (Dec 30, 2020)

I used the Alibaba app. Create an account and then search for Daly and you will be able to chat with a rep.


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## xevion (Dec 26, 2020)

Parts!
Since my last posts I've ordered a bunch of parts, some are even already here.

*300A 14S Daly BMS via AliBaba *- There didn't seem to be many BMS options for this battery setup, and this one seems to be a good option with some fun "smart" features.
*2x 7S 2019 Nissan leaf battery modules* - Really looking forward to seeing what these things can do, they were the most expensive part of this build ($1700 total shipped). The seller was awesome (bumblebee batteries) and sent the stock bus bar to connect them in series as well as the car side of the balance connector. 
*Meanwell 1600W 48V programmable battery charger* - Another part I'm very excited about. It can take in 90-250V AC without any adjustment, meaning I can set the car up to take a 110 wall outlet, or charge slightly faster on a 220V from the wall or from a J1772. I'm probably going to pick up a J1772 adapter from Tucson EV. Stock the charger is set up to do 3 stage charging, but can be configured to do 2 stage and has a bunch of other settings adjustable via an i2c connection. I'm currently designing an arduino compatible library to talk to it and will have a display to view charging info/change parameters on the fly.

There are still a handful of other miscellaneous parts I need. Chief among them is a motor controller, I'm looking at just a bog standard ~250A 48V golf cart controller because they can be had relatively cheaply.


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## xevion (Dec 26, 2020)

Lots of progress since my last update. 

The 12V wiring on the car was a mess, and I spent a while getting the turn signals/brake lights/etc. working. Here's what the turn signal module looks like, and my attempt at labeling all the wires that run to it.
















The carpet was pretty rough so we ripped that up and installed some nicer blue carpet















The "windows" were also in pretty rough shape, so we cut some new vinyl material for them and my friends mom sewed them up for us. The new plexiglass looks great too, we just have to make the windows fit and glue everything up.
























Motor controllers! I was able to grab these two for free, which was awesome, however they are both 24-36V and with a max pack voltage around 60V I think my pack might ruin these controllers.








I've been trying to find someone to trade for a 48V controller or sell these with no luck. I'm considering just grabbing a cheap one like this PMC 1204M-5305 DC Motor Controller Upgraded 1204M-5301 for Curtis 48V 0-5k【USA】 | eBay but the listing rates it at only 33-48V which makes me think it still might not work.


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## xevion (Dec 26, 2020)

The batteries are in their (hopefully) final resting place. The battery box is built with PVC board and the batteries are secured down with threaded rod that goes through the aluminum floor. The batteries are also snugly nestled between the frame rails so they shouldn't be going anywhere. There is clearance above, below, and between the batteries to allow air to flow, should I discover the batteries need active cooling. For now there is just a vent, no fan, so I'll keep a close watch on the temps the first few drives. The PVC box is mostly there to keep the batteries & electronics clean and dry since this space under the seats where the original batteries went was not protected from the elements. There's enough room to fit the BMS, charger, and main contactor in there as well. The motor controller and forward reverse contactor are going to live somewhere else.


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## xevion (Dec 26, 2020)

As a part of this project I've also written an open source library for using an Arduino to communicate with both the BMS & the charger, and designed and ordered a custom PCB to hold the microcontroller and a display to show charging information (Rev 1 pictured below).








BMS Library: maland16/daly-bms-uart
Charger Library: maland16/teensy-RPB-1600


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## MattsAwesomeStuff (Aug 10, 2017)

xevion said:


> Motor controllers! I was able to grab these two for free, which was awesome, however they are both 24-36V and with a max pack voltage around 60V I think my pack might ruin these controllers.


If they're anything like the golf kart Curtis that I have, you probably won't blow them up with extra voltage, however, they just won't work. They have graceful overvoltage protection where they just shut down if the input voltage is too high (or too low). That said, I think you can squeeze 44 or so volts out of the 36v one, because they're designed for lead acid batteries and "12v" lead acids are close to 15v when charged.


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## xevion (Dec 26, 2020)

MattsAwesomeStuff said:


> If they're anything like the golf kart Curtis that I have, you probably won't blow them up with extra voltage, however, they just won't work. They have graceful overvoltage protection where they just shut down if the input voltage is too high (or too low). That said, I think you can squeeze 44 or so volts out of the 36v one, because they're designed for lead acid batteries and "12v" lead acids are close to 15v when charged.


Ok, in that case I'll probably pull the trigger on that cheap Ebay controller just so I can get the car on the road. By that math the 48V controller should be able to handle 60V


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## xevion (Dec 26, 2020)

Rev 2 boards are in! I'll be wiring everything up to test this weekend.


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