# Help designing battery pack



## cool_stepdad (Oct 16, 2021)

Hello again,
I am still thinking through the battery solution for my 1985 westfalia conversion. 
I would like my range to be around 200miles for camping trips and whatnot. 
I’ve done some math and the numbers I’ve come up with are as follows:

600wh/m vehicle power usage
132v ac motor (hyper 9)
120kw needed for range
Which comes out to 909ah
Multiply by 1.32 to account for peukerts etc to get 1199.9 ah
Convert to kwh and we get 158.4 kwh 

so. My question is, how feasible is it to build a 132v 159ish kwh pack with commercially available modules vs building my own?

I am under the impression that parallel modules add to wh and series adds to voltage. If that is the case and I’m not missing anything, that means with the lg chem cells at 232ah and 22.8v I would need something like 6s5p.
Does this sound right? Is there something simpler I am missing? Any help / number checking would be appreciated.
Thanks!


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## remy_martian (Feb 4, 2019)

Parallel adds to Ah

Cells add to Wh

Continuous discharge on most cells I've seen is beyond 1C, so your Ah estimates should be able to be reduced.


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## cricketo (Oct 4, 2018)

I use Nissan Leaf 24kWh pack at 440lb as a unit of measure to guesstimate these things. The main thing to point out is the weight - 158.4kWh / 24kWh = 6.6. Multiply that by 440...2904lb. In reality it would be a bit lighter, but not by more than 10%. So easily 2600lb battery pack. Found some relevant numbers from googling :



> *Type II Bay Window
> 
> From a 1978 owners manual:*
> 
> ...


In other words I think 158kWh is a non-starter.


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## cool_stepdad (Oct 16, 2021)

remy_martian said:


> Parallel adds to Ah
> 
> Cells add to Wh
> 
> Continuous discharge on most cells I've seen is beyond 1C, so your Ah estimates should be able to be reduced.


Ok thanks! Could you elaborate on why the ah estimate could be reduced?


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## cool_stepdad (Oct 16, 2021)

cricketo said:


> I use Nissan Leaf 24kWh pack at 440lb as a unit of measure to guesstimate these things. The main thing to point out is the weight - 158.4kWh / 24kWh = 6.6. Multiply that by 440...2904lb. In reality it would be a bit lighter, but not by more than 10%. So easily 2600lb battery pack. Found some relevant numbers from googling :
> 
> 
> 
> In other words I think 158kWh is a non-starter.


Yeah… and the newer models are a bit heavier from what I’ve seen. Kind of a bummer. I’ll look into increasing the payload capacity but seems that I will have to settle for lower range for the time being.

thanks a bunch!


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## cool_stepdad (Oct 16, 2021)

So these numbers were calculated with 600wh/m in mind but the more I look, I think that may have been a little aggressive. The Chevy bolt build from this forum was something like 60kwh and he was getting over 100 miles out of it. I am seeing people with over two ton trucks getting 400wh/m and the van, while not very aerodynamic, weighs less. If I use the bolt range numbers I come out to a pack that need to be 128kwh to get 200 miles of range. I will still have to dial that back since that would mean a battery weight of close to 23k lbs. Just thought I’d share.
Thanks guys!


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## brian_ (Feb 7, 2017)

cool_stepdad said:


> ... with the lg chem cells at 232ah and 22.8v I would need something like 6s5p.


22.8 V would be a module, not a single cell; presumably it has six cell groups in series. What LG Chem module is this? 

Paralleling modules is problematic; it would be better to use modules with more cell capacity in parallel and fewer cell groups in series. No matter what module is found, getting this extreme capacity with such a low voltage will mean a complex pack.


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## brian_ (Feb 7, 2017)

cool_stepdad said:


> If I use the bolt range numbers I come out to a pack that need to be 128kwh to get 200 miles of range. I will still have to dial that back since that would mean a battery weight of close to 23k lbs.


A 23,000 pound battery for only 128 kWh is wildly unreasonable. Did you mean 2,300 pounds? The battery weight is still a problem for a long-range conversion.


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## cool_stepdad (Oct 16, 2021)

brian_ said:


> A 23,000 pound battery for only 128 kWh is wildly unreasonable. Did you mean 2,300 pounds? The battery weight is still a problem for a long-range conversion.


Ha yep. I fat fingered the number. And yeah. Gotta get the weight down.


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## cool_stepdad (Oct 16, 2021)

brian_ said:


> 22.8 V would be a module, not a single cell; presumably it has six cell groups in series. What LG Chem module is this?
> 
> Paralleling modules is problematic; it would be better to use modules with more cell capacity in parallel and fewer cell groups in series. No matter what module is found, getting this extreme capacity with such a low voltage will mean a complex pack.


Yeah sorry I meant module. It’s the lg module on ev west.


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## MesquiteTim (Sep 30, 2021)

Are you considering Tesla modules?


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## brian_ (Feb 7, 2017)

cool_stepdad said:


> Yeah sorry I meant module. It’s the lg module on ev west.


There have been many LG modules, and EV West has sold a lot of a different module (the one intended for the Chrysler Pacifica Hybrid, which is no longer available). So it's presumably this one:
LG Chem Super Cells 1.6 kWh - JH3 63Ah 7S High Power Battery Module - For Tesla Systems
[LGSS1.7]

As I noted in another thread,


brian_ said:


> I had not heard of a "JH3" cell or module, so I did a quick search...
> 
> An LG Chem catalog suggests that JH3 is the "Energy" (rather than "High Energy" or "Power") variant in their range of cells for large energy storage systems. It may not be intended for use in a vehicle, as it is intended for discharge rates under 1C. Based on this catalog, the 7S 63 Ah JH3 module appears to be one of two used in LG Chem's smallest residential energy storage system, the "48 V" RESU3.3. The other RESU models may use more of the same modules in parallel. The catalog shows that stationary ESS and automotive applications are distinct.
> 
> Whether this is the same cell construction as used in EVs or not, the JH3 modules being sold by EV West at 3.22 Wh/USD (or USD $312/kWh) is a 7S (26 V) 63 Ah module; it is *not* the 16S (60 V) 43 Ah module used in the Chrysler Pacifica, and not even built of the same cells. The Pacifica module is designed to thermal management via a bottom plate, but it is not apparent whether or not there is any thermal management provision in the JH3 module, although the general construction is similar. The JH3 module is a recent addition to the EV West website.


It is 7S, so about 26 V nominal not 22.6 V. It has 63 Ah capacity, not 232 Ah.



cool_stepdad said:


> ... with the lg chem cells at 232ah and 22.8v I would need something like 6s5p.


If the 22.6 V and 232 Ah specs are for a different module, I assume that it is the Tesla Model S module, but that's not an LG module.

With the LG H3 63 Ah 7S modules, 128 kW at 1.6 kWh per module would be 80 modules, for a total of 1568 pounds (711 kg). For about 130 V nominal, they would be 5S16P... sixteen strings of five modules each, with sixteen 35-point BMS systems.

With the 232 Ah 22.6 V Tesla model S modules, 128 kW at 5.3 kWh per module would be 24 modules, for a total of 1320 pounds (599 kg). For about 136 V nominal, that could indeed be 6S5P modules... five strings of six modules each, with five 36-point BMS systems.


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## cool_stepdad (Oct 16, 2021)

brian_ said:


> There have been many LG modules, and EV West has sold a lot of a different module (the one intended for the Chrysler Pacifica Hybrid, which is no longer available). So it's presumably this one:
> LG Chem Super Cells 1.6 kWh - JH3 63Ah 7S High Power Battery Module - For Tesla Systems
> [LGSS1.7]
> 
> ...


Awesome. Thanks so much. I’ve been trying to find the module I was looking at and apparently it wasn’t at ev west. Sorry about that and thanks for the information!


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## cool_stepdad (Oct 16, 2021)

brian_ said:


> There have been many LG modules, and EV West has sold a lot of a different module (the one intended for the Chrysler Pacifica Hybrid, which is no longer available). So it's presumably this one:
> LG Chem Super Cells 1.6 kWh - JH3 63Ah 7S High Power Battery Module - For Tesla Systems
> [LGSS1.7]
> 
> ...


Quick question about this. If I am shooting for 128kwh then With the lg modules 80x1.6=128. How does this work if some of the modules are in series and not adding up their kwh? Or am I misunderstanding series vs parallel or kwh vs ah? Thanks again.


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## cool_stepdad (Oct 16, 2021)

MesquiteTim said:


> Are you considering Tesla modules?


I am. Kind of open to anything at this point.


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## brian_ (Feb 7, 2017)

cool_stepdad said:


> If I am shooting for 128kwh then With the lg modules 80x1.6=128.


Right... regardless of how they are arranged.



cool_stepdad said:


> How does this work if some of the modules are in series and not adding up their kwh? Or am I misunderstanding series vs parallel or kwh vs ah? Thanks again.


The voltage of anything connected in series (cells, battery modules, batteries, solar cells, any voltage source) adds up, so the possible configuration of these 26-volt modules would be five in series; that is, a string of five of them would give you 130 volts, still at 63 amp-hours.

The current capacity of anything connected in parallel adds up, so the possible configuration of these 26-volt modules would be 16 in parallel, still at only 26 volts. So 16 of these modules in parallel could provide 16 * 63 = 1008 amps for an hour (or more likely 252 amps for four hours, or whatever), but only at 26 volts.

You can't have just "some" modules in series. One of those string of five modules is only 63 Ah, so you need 16 of those complete strings, with all the strings connected in parallel to each other, to add up to 130 volts and 1008 Ah of capacity that you need. 130 V multiplied by 1008 Ah is 131,000 Wh (131 kWh); that's the same as 80 modules at 1.6 kWh each multiplying out to 128 kWh, plus or minus a bit of rounding error. That's a bit more than your target, but 15 strings of 5 (75 modules) would be less than the target and 16 strings of four (64 modules) would be substantially less.


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## cricketo (Oct 4, 2018)

cool_stepdad said:


> Quick question about this. If I am shooting for 128kwh then With the lg modules 80x1.6=128. How does this work if some of the modules are in series and not adding up their kwh? Or am I misunderstanding series vs parallel or kwh vs ah? Thanks again.


Is there a particular reason you think you will be successful with this project ?


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## MesquiteTim (Sep 30, 2021)

Isn't your 600 wh/m way too high? Did you ask EV West what they experience with their older van conversions? They offer a kit for the older van that may work for yours. I would build a small pack first assuming that it will average 300 wh/m and get it on the road. Then add the second half of battery power later, if needed at all.


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## cricketo (Oct 4, 2018)

MesquiteTim said:


> Isn't your 600 wh/m way too high? Did you ask EV West what they experience with their older van conversions? They offer a kit for the older van that may work for yours. I would build a small pack first assuming that it will average 300 wh/m and get it on the road. Then add the second half of battery power later, if needed at all.


300wh/m is the average performance that fairly aerodynamic and weight-optimized factory EVs get. I doubt it can be achieved here.


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## csuich (May 20, 2014)

I did a 2003 MINI Cooper conversion. 
I had 15kW battery pack that weighed 350lbs.
My best range was 50 miles. I designed it for a daily commute of 38 miles. 
The watts/mile was typically around 350. Speed (headwind) was the major factor in power usage. If I drove 45-50mph, I was comfortable trying for 45 miles. 
I think your number of 600w/mile is too high. I would think 450 might be a better number. 
Regardless, in my example, a 200 mile range would require 60kwh battery pack and would weigh 1400lbs and would require suspension modifications (springs and tires) to handle the heavier load. 

If you got a Tesla drive train, sub-frame, batteries and build your van on top of that, it might be an easier build. 🤔


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## Cor (Sep 17, 2013)

cool_stepdad said:


> So these numbers were calculated with 600wh/m in mind but the more I look, I think that may have been a little aggressive. The Chevy bolt build from this forum was something like 60kwh and he was getting over 100 miles out of it. I am seeing people with over two ton trucks getting 400wh/m and the van, while not very aerodynamic, weighs less. If I use the bolt range numbers I come out to a pack that need to be 128kwh to get 200 miles of range. I will still have to dial that back since that would mean a battery weight of close to 23k lbs. Just thought I’d share.
> Thanks guys!


The production Bolt has a 65kWh pack and gets 260mi range.
I have a '94 Chevy S10 truck that gets better than 3 mi/kWh as long as I can keep my foot out of it and cruise 55 on the freeway, getting easy 100 mi range on a pack that is barely more than 30kWh. Instantaneous power at 55mph flat road is right around 15kW.
If weight and size are serious issues (and they usually are for lighter vehicles) then I suggest looking into getting a Bolt or a 2019+ Leaf pack (62kWh) which should give you about 800 lbs of battery modules and give you the range you need, as long as you agree to moderate speed. But the VW camper van is not really meant for racing anyway...


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## brian_ (Feb 7, 2017)

csuich said:


> I did a 2003 MINI Cooper conversion.
> I had 15kW battery pack that weighed 350lbs.
> My best range was 50 miles. I designed it for a daily commute of 38 miles.
> The watts/mile was typically around 350. Speed (headwind) was the major factor in power usage. If I drove 45-50mph, I was comfortable trying for 45 miles.
> ...


A Westfalia is a lot heavier and has a lot more aero drag than a Mini, so based on 350 Wh/mile in the Mini, 450 Wh/mile in the Westfalia is unlikely.

The battery pack in any model of Tesla fills all available length under the floor of the car, so none of them would fit under the Westfalia with its much shorter wheelbase. The track width of at least a Model S or X is substantially greater than the Westfalia, so those Tesla subframes (with suspension) would be too wide... and without checking specifications my guess is that even the Model 3 components would be too wide.


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