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Hi all,

I've used the search function and also scanned through for a few hours and cannot find an answer so if it has been answered already please link me!

When figuring out battery mounting locations for budget builds is there any reason why I couldn't put a battery pack in the engine bay to save space in the cabin?

I am assuming that the weight and heat would be the only limiting factors provided there is space.

Is it as simple as trying to prevent the weight in the engine bay from exceeding the original weight after changing out components?

I'm interested in doing a conversion on a petrol engine, manual transaxle hatchback using agm or spiral deep cycle batteries at a max of 72v as I want to find a balance between range and top speed. Most roads around my house are 80km/hr zones so I would need the vehicle to keep up and be capable of highway speeds but am also chasing a range of around 300km per charge. I understand that this will require some considerable AH storage and have a battery supplier in mind already that supplies batteries that would suit (if my calculations are correct).
Was planning on using a 100lb (approx) forklift motor overvolted to 72v.

I was thinking of having 2 packs in parallel with one above the electric motor in the engine bay space and the other in the floorpan void where the fuel tank will be removed from (under the rear seat floor).
I'm in Australia so there's no issues with snow or salt.

I've also been a motor mechanic and auto electrician for over a decade so am confident I can make it all work space and fabrication wise.

Am I crazy or will this work out ok?
 

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No reason why not, as long as you have the space to do it.
That's one of the joys of EV conversions, you can out the batteries pretty much where you want to get the best weight distribution.
Good luck with the project

Sent from my moto g(8) power lite using Tapatalk
 

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Thanks for the quick reply mate!

Im keen, just have to get the minister for finance to sign off hahaha
 

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Most DIY conversions of front-engine vehicles put at least some of the battery in the engine compartment. Things to avoid include both excessive weight on the front axle (as already considered) and putting massive components too far out toward the ends of the vehicle (as some people do as they stack battery modules all the way to the nose).

Production EVs based on conventional engine-driven cars don't put battery in this location, because they use a substantially modified body and so they can put a single battery pack (for simplicity of manufacturing) under the floor (for a lower centre of mass and larger battery volume). That really isn't an option for most DIY builds.
 

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I recently relocated my pack to the rear of my car, just for the element of safety in a front end collision. The pack is pressed up against the back seats in the trunk, and the cables run under the car where the old exhaust was located previously. I would have preferred to put it in the front though, the car looks like it's doing a wheelie now with all the weight being way in the back. When I move to lithium, I may do what was mentioned above and scatter the cells between the front/rear, but also build a strong 'exoskeleton' for them to ensure they can be protected if anything happens.
 

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I'm interested in doing a conversion on a petrol engine, manual transaxle hatchback using agm or spiral deep cycle batteries at a max of 72v as I want to find a balance between range and top speed.

am also chasing a range of around 300km per charge.

I understand that this will require some considerable AH storage and have a battery supplier in mind already that supplies batteries that would suit (if my calculations are correct).
Hey Sockiemeister, I am curious what you came up with for your calculations. I am concerned you are overestimating what is possible with lead acid batteries, which is what I assume you are talking about with AGM or Spiral Deep Cycles. 300km (~190 miles) per charge is a very heavy lift for a DIY car. Nothing is impossible, but with lead acid, it would be unreasonable.

To get a range estimate, start with the energy density of the battery. For lead acids, I found about 18wh/lb. If you add 1000lbs of batteries, you will get 18,000wh. A good rule of thumb is that a car needs 10% of its weight in watt-hours to go a mile. Say the car starts at 2500lbs, it now weighs 3500lbs, and will need 350wh/mile. Those 18000wh will take you about 50 miles. If you want those batteries to last more than a few cycles, you will need to not discharge them more than 50%, so really, you are down to 25miles. Unless it is cold out... more like 20 miles... The next 1000lbs of batteries will not add as many miles, since you just upped the weight; so before long you are going to need a semi-truck to haul all that lead around.

Long story short: Unless you are happy with going about 20 miles to a charge, you will want to look for lithium batteries. The good news is that they are actually cheaper than lead, if you can source them out of a crashed EV.
 

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For reference, a common Leaf pack is 24kWh and weighs 400lb outside the shell. Costs $4k, tops. Even if you figure 16-18kWh are actual usable watts, and you're still ahead of lead-acid in every way besides needing a BMS and special charger.
 

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Hi all,

I've used the search function and also scanned through for a few hours and cannot find an answer so if it has been answered already please link me!

When figuring out battery mounting locations for budget builds is there any reason why I couldn't put a battery pack in the engine bay to save space in the cabin?

I am assuming that the weight and heat would be the only limiting factors provided there is space.

Is it as simple as trying to prevent the weight in the engine bay from exceeding the original weight after changing out components?

I'm interested in doing a conversion on a petrol engine, manual transaxle hatchback using agm or spiral deep cycle batteries at a max of 72v as I want to find a balance between range and top speed. Most roads around my house are 80km/hr zones so I would need the vehicle to keep up and be capable of highway speeds but am also chasing a range of around 300km per charge. I understand that this will require some considerable AH storage and have a battery supplier in mind already that supplies batteries that would suit (if my calculations are correct).
Was planning on using a 100lb (approx) forklift motor overvolted to 72v.

I was thinking of having 2 packs in parallel with one above the electric motor in the engine bay space and the other in the floorpan void where the fuel tank will be removed from (under the rear seat floor).
I'm in Australia so there's no issues with snow or salt.

I've also been a motor mechanic and auto electrician for over a decade so am confident I can make it all work space and fabrication wise.

Am I crazy or will this work out ok?
you are not crazy at all, i rebuilt a mitsubishi express van with an 144v 24kw rated motor and 65kwh 156v battery pack (the motor has more power if on 156v), i used the whole floor in the back for the batteries and made supports & a cover to carry the goods on top of the batteries...
in your case think about the space you get when removing the exhaust, tank & engine, already in these spaces you may have a lot space available for batteries...but you may have to weld supports, plus under the back seat you may have additional space, re speed, my 24kw motor is connected to the old clutch/gearbox that gives you a lot torque to take off at the intersection and the upper gears allow to drive fast, my van has no problem to do 100km/h, i would recommend min 20kw motor, just be aware 20kw 72v = 277amp (when take off up to 400amp!!!) it needs a lot of copper,,,,good luck
 
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