[pottscb]

Hey all,
I just bought a “for parts” heavy duty ATV for use on my place. It’s basically just a frame and bed, all the batteries were gone and most of the plastic, rubber, brakes, suspension, needs replacing, or so I thought. After getting it apart I found an aftermarket motor that is high torque (600A) and an aftermarket Curtis 600A motor controller so I can afford to throw a little money at the batteries (and I’ll have to as that motor will crush most 48V batteries, or at least the BMS of light duty batteries) I haven’t put the inrush amp load logger on it yet but I’d like to spec batteries that can handle 600A for a few seconds on startup (and 200A continuous) as I’ll be hauling/towing with it at low speed. It has a 24”x27”x12” battery compartment under the bed so I’ve got room. The battery compartment has openings on most sides and vent in front to let airflow through so cooling shouldn’t be a problem. I’m looking for enough capacity that I only have to charge 1xWk at most so probably 200Ah+. This limits my choices and makes them much more expensive, you can either have high amperage or long range relatively inexpensively, not both.

As I’m new to this, I started out looking
for the easiest PnP solution I could find, such as kilovault HLX+ 48V-300Ah but these run $6K MSR. Then I migrated to Nissan Leaf, but I’m having trouble finding them worth the money that aren’t at less than 50-70% capacity (which is when Nissan warranty replaces them). So now I’m at Tesla S modules which are the best bang for buck as far 48V-250Ah…but implementing them isn’t for the faint of heart. I’m not an engineer but I can read a schematic, the problem is, the current electrical system has been piggybacked/spiced for several small accessory switches and implementing the BMS and contactors complicate things and I can’t find a schematic for specifically what I want to do, which would be 2X 24V Tesla modules, fairly simple BMS (SimpBMS?), onboard charger with 12V shunt for lights, commercial sprayer, etc.

Anyone have feedback on this? Am I barking up the wrong tree with Tesla modules for a first time build? Anyone interested in me posting my build pics?

 

[remy_martian]

Not sure what you mean by "12V shunt"?

If you can afford them, Tesla is fine. @Functional Artist uses Chevy Volt modules.

Yes, by all means, do a build thread if you're up to it. Helps anyone else that might do a similar conversion and you can think out loud before spending the money or doing something.

 

[pottscb]

Not sure what you mean by "12V shunt"?

If you can afford them, Tesla is fine. @Functional Artist uses Chevy Volt modules.

Yes, by all means, do a build thread if you're up to it. Helps anyone else that might do a similar conversion and you can think out loud before spending the money or doing something.

So, I did the math and it’s just no cheaper to buy 30-40Ah-50% depleted Nissan leaf modules for $60/ea. when I’d need 7 to get 48V and 7 sets (49) to get close to 250Ah…the only excessively expensive thing with Tesla is BMS…but I think you recoup that by the very slow capacity loss.

Sorry, I was trying to communicate a 48V step down converter for 12V accessories…as the current one in my setup has been Jerry-rigged to the point of unusability.

As far as mechanical system design, the nice thing about EV is that, if it’s not being used, it’s not creating heat, so different from ICE that actually need more fans when it’s not moving. Most of my use with this vehicle will be drive 100 ft, stop unload, drive back 100 Ft reload, which is one reason I chose EV, all that time idling is wasteful and hard on vehicle and nature, or you can replace a starter every couple years.

 

[remy_martian]

The slow capacity loss is the result of very aggressive temperature management.

Few DIYers go there.

 

[Functional Artist]

Howdy & welcome

For what it sounds like your building
...& what you want to use it for

IMO you'll only need a ~2kWH (~50AH) to~4kWh (~100AH) battery pack
...& for a vehicle of that size, you'll never need or use 600A

Probably more like ~200A peak (for a few seconds)
...& maybe ~50A - ~100A continuous

I have a 48V 8kW PM motor on an old motorcycle
...& doing "the math" (8,000/48V=166.67A)

When riding around, I've seen it draw ~150A on hard accelerations
...& more like ~50A to ~100A when just cruising
...& hardly anything while coasting

 

[pottscb]

Not sure what you mean by "12V shunt"?

If you can afford them, Tesla is fine. @Functional Artist uses Chevy Volt modules.

Yes, by all means, do a build thread if you're up to it. Helps anyone else that might do a similar conversion and you can think out loud before spending the money or doing something.

So, I did the math and it’s just no cheaper to buy 30-40Ah-50% depleted Nissan leaf modules for $60/ea. when I’d need 7 to get 48V and 7 sets (49) to get close to 250Ah…the only excessively expensive thing with Tesla is BMS…but I think you recoup that by the very slow capacity loss.

Sorry, I was trying to communicate a 48V step down converter for 12V accessories…as the current one in my setup has been Jerry-rigged to the point of unusability.

As far as mechanical system design, the nice thing about EV is that, if it’s not being used, it’s not creating heat, so different from ICE that actually need more fans when it’s not moving. Most of my use with this vehicle will be drive 100 ft, stop unload, drive back 100 Ft reload, which is one reason I chose EV, all that time idling is wasteful and hard on vehicle and nature, or you can replace a starter every couple years.

Howdy & welcome

For what it sounds like your building
...& what you want to use it for

IMO you'll only need a ~2kWH (~50AH) to~4kWh (~100AH) battery pack
...& for a vehicle of that size, you'll never need or use 600A

Probably more like ~200A peak (for a few seconds)
...& maybe ~50A - ~100A continuous

I have a 48V 8kW PM motor on an old motorcycle
...& doing "the math" (8,000/48V=166.67A)

When riding around, I've seen it draw ~150A on hard accelerations
...& more like ~50A to ~100A when just cruising
...& hardly anything while coasting

I’m not worried about the amp draw as much as range and how often I have to charge (as I’m not doing any sort of fast changing). Not sure what it will weight after battery conversion but it was 1600lbs before, & occasionally pulling a loaded 16’ flatbed trailer which, if Ford lightning is any indication, will decrease my range by 75%…

Here’s my motor: 502:1 EZ GO Motor - Details and Specifications

 

[pottscb]

The slow capacity loss is the result of very aggressive temperature management.

Few DIYers go there.

Agreed. Also true that few DIYers would need to go there. I’m using a motor that tops out at 14 mph. It will be in a battery compartment vented from the front and rear with airflow above & below which Tesla chose not to do. Different applications but I’m not worried about range as I might put 20-30 charge cycles on it a year…they’re expected to make 1500? (Or is that to half capacity). I’m sure everyone is familiar with this but it illustrates they go a long darn way with minimal degradation.

A look at Tesla battery degradation and replacement after 400,000 miles

In this new installment of our series on the highest-mileage Tesla Model X (and one of the highest mileage EVs...

electrek.co

 

[pottscb]

Turns out I just won an auction for 2 Tesla mod. S battery modules out of a 2017 with 54K mi. So I guess the discussion now turns to, who has DIY’d this battery in any application and with which available BMS and what did you use to charge it? (and can you post links so I can learn how). The battery comes with the Tesla balance boards and pigtail connectors so I’m seriously considering the SimpBMS or its sucessor (for simplicity). I know Orion is another choice but would be more money as I’d have to rebuy balance boards and the BMS itself is substantially more expensive, I really don’t need all the bells and whistles on a ranch vehicle that I plan to use pretty hard…I’d rather have something PnP that is waterproof, dust proof and shockproof (which I don’t think exists).

 

[kennybobby]

IMO, those tesla cell monitoring boards are really high quality with some unique features that i've not seen on any other cell monitoring boards, OEM or A/M; i think some folks may have figured out the code needed to use them, might be worth keeping and using for your modules.

i hope the modules fit, or you can make them fit, that will be a cool little work truck.

 

[remy_martian]

It will be in a battery compartment vented from the front and rear with airflow above & below which Tesla chose not to do.

A look at Tesla battery degradation and replacement after 400,000 miles

In this new installment of our series on the highest-mileage Tesla Model X (and one of the highest mileage EVs...

electrek.co

I really don’t need all the bells and whistles on a ranch vehicle that I plan to use pretty hard…I’d rather have something PnP that is waterproof, dust proof and shockproof...

Really?

Because that genius vented box of yours isn't at least 2 of your 3 requirements.

You also want to run the batteries up to 3C without liquid cooling...bring marshmallows. Without coolant, the cells are thermally coupled and it's not a matter of if, but when you have a gator bonfire at the ranch, imo.

 

[pottscb]

IMO, those tesla cell monitoring boards are really high quality with some unique features that i've not seen on any other cell monitoring boards, OEM or A/M; i think some folks may have figured out the code needed to use them, might be worth keeping and using for your modules.

i hope the modules fit, or you can make them fit, that will be a cool little work truck.

Yeah, I hope to be able to figure out all the BMS options and get them to work.

 

[pottscb]

I’ve been shopping for a month for a John Deere Gator TE which is the turf electric model, to replace the SLA with lithium but problem with most of them is that they have integrated BMS (battery management) that limit the output to 100Amp output) and are designed for solar use. Most golf carts don’t pull that much but a Polaris/Gator might and a (weighs 1250lbs without batteries, wider stance than most golf carts) anyway, Signaturesolar.com has a one-enclosure 48V-100Ah battery that puts out 200Amp (more in bursts) for nearly the same price as others 100Amp output and I just purchased it today but won’t be able to tell you if it’s any good for a while (though it’s been reviewed well by David Poz et Al. I know when compared to lead acid lithium has substantially more capacity because they can use used safely down to 10% (leads in use half their capacity) and the lithiums can charge from 10-90% in a couple hours.(one could use this rationale to buy less capacity, but I’m lazy so hopefully I’ll only have to charge it once a month which should last forever as they’re rated for 5000 charge cycles.). Anyway, I could’ve saved a little by buying cells, figuring out how to solder in a BMS, program that BMS (which is a problem as I’m an all Max family) and make an enclosure, but as it’s going to be in a hard use ranch vehicle I decided to go with a well manufactured enclosure that’s waterproof (IP68 rated) and simple. If I have difficulties with the amperage limit I’ll either program the motor controller or add a second battery in parallel.

 

[remy_martian]

One approach to get more current out is to fake the BMS out by hacking its current sensor output to say it's 100A when there's really 200A or 300A flowing.

That may have other implications, so you need to do some homework.

 

[cricketo]

Wow, I didn't know JD made electrics. Is that thing 2WD or 4WD ?

I think Tesla modules are the wrong tool for this job - they're 6S, so you get a 12S with two in series. Lead-Acids would be at 45.6V near full discharge, but 12S NCA would be 36V or so... Thus 14S is a better configuration for converting former Lead-Acid 48V systems, and even 16S in some cases.