Harden Electric Blog Batteries: A challenge to Electric Car Conversions

Batteries: A challenge to Electric Car Conversions


The main driver for an electric vehicle, and the things that keep us up at night with regards to range anxiety, how far can I go? How fast? Can I tow? What impact will that have on my range? How fast can I charge? These are all questions that people have posed to us via our facebook page and other means, so we thought we would do up a quick article as to what the challenges are, not so much for a vehicle from scratch, but for converting your existing internal combustion engined vehicle (ICE) to an EV. In this article we are going to cover some things that people know, some things that people should know, and some challenges to cramming as many batteries as possible into your conversion.


This should go without saying, cost is a major factor for a lot of people, batteries are not cheap. Anyone that has had to put a new battery in their conventional car can attest to this. I myself have owned numerous 4WD’s over the years, and batteries for them range from $250-500 depending on your needs, and this is just for a simple lead-acid cranking battery.

So the average weight for the general consumer can be around $900 for 400Ah, or, as a 3.2v cell using these cells from EVWorks Australia gives you 1.28kWh or $687.50/kWh which is a good amount of money for your vehicle.

Factoring in that most EV’s today need around the 50kWh for a decent range, that’s around the $‭34,375‬ range for 50kWh at this price.

Now there are cheaper cells on the market, and you can assemble your own battery packs to get the required voltages you need, but suffice to say, batteries will make up the overwhelmingly vast majority of your conversion. This is where companies like Harden will come in on this, because if we can make kits for you to convert your vehicle, we can achieve an economy of scale that we can pass onto the consumer.

Likewise, if we can construct vehicles ourselves to market, if we can have “all our ducks in a row” so to speak and send out kits that are identical, we can bulk order batteries and pass those savings on. But we can 100% say go have a look at https://www.evworks.com.au/ and have a look at what you need and what it would cost as a consumer.

Charging rate

This is a whole other issue with batteries, the charging rate, or discharging rate. Picking batteries is not just the instant thing that you can pick any old battery and they will all be the same, different batteries will have different charge and discharge rates, and this can factor heavily into your performance of the vehicle on the road, and the performance of your charger.

Whilst we like to talk about 6.6kW Chargers, 25kW, 50kW, 100kW, 150kW or 250kW chargers, and their charging speeds, a lot needs to be known about the batteries, the chemistry, and the charger required to go behind all of that.

You can’t just take your average battery and pump in a rate of 150kW DC and charge it, you will need both a Battery Management system that can accept that, and can balance your cells correctly, as well as a cooling system to get the batteries up to temperature to accept the charge, and then hold them at a stable temperature while charging is taking place. As charging will heat up your batteries, and you need to be able to remove that heat if you want to charge efficiently. This is why there are stories out there of vehicles bursting into flames when charging, as they experience thermal runaway while charging due to inadequate cooling.

This is more an issue with fast chargers than slow chargers. However, as a company, we understand that people have places to go and things to do. You don’t want to be in a situation where you need 60kWh into your car, and all you have is a 6kW charger, you don’t have 10 hours to wait. So we need to be able to design a robust cooling system that will allow you to charge your vehicle at a decent rate.


Weight is another huge factor in an electric vehicle, batteries are heavy. On just the raw numbers we mentioned before, the Winston 400Ah LiFePO4 cell we mentioned before weighs in at a chonky 16kg, and at 1.28kWh for that battery, to get the required 50kWh out of that, you’ll need at least ‭39.0625‬ of these, as you can’t have 0.625 batteries, we’ll round up to 40 batteries (As to link batteries together, even numbers are easier, and running a slightly larger battery pack than required means you can avoid full discharges and high charges, thus prolonging your battery life)

So 40 batteries at 16kg each gives you 640kg of weight that you now have to distribute around the car, this needs to be worked out correctly, otherwise you end up being nose heavy, tail heavy, or raising the centre of gravity of your vehicle, which can lead to unintended handling issues or rollover issues. You want to keep the weight low and balanced. A common reason why people will install their batteries in place of the engine and fuel tanks is to help keep the distribution similar to a factory vehicle in the conversion. Engines are heavy, batteries are heavy, so this can help you in your conversion by retaining fairly similar vehicle behaviour on the road.

Legal issues

When it comes to mounting batteries in your vehicle for a conversion, and the whole conversion itself, at the time of writing, federally, in Australia, your primary go-to is Vehicle Standards Bulletin 14 – National Code of Practice which is the go-to Federal document on vehicle modification, and you have to comply with every bit of it in order to get your conversion on the road.

Main issues that you will face will be covered under NCOP13 Section LV Alternative Power Units and NCOP14 Guidelines Electric Drive which cover the main parts of an electric conversion. With regards to batteries it covers how they are secured in the event of a crash, as well as how they are protected against rupture, short circuit, how they can be disabled and cut off by first responders, as well as correct marking of high voltage components.


Hopefully this will give you some idea of the issues that can be faced when picking the correct batteries for your conversion, and some of the challenges we will be facing when it comes to designing a conversion kit for our customers. This is partially why we were originally leaning towards building a vehicle entirely from scratch.

However, people have spoken, and we have listened, and it seems there is a large number of people that would love to have a crack at this themselves, as such, we would love to explore this further, and we would love to know what vehicles people would be interested in converting. So please, leave a comment below as to what you would like to see us convert!

2 thoughts on “Batteries: A challenge to Electric Car Conversions”

  1. Interesting article. I was considering converting a 2000 Mazda 323. Originally being 5 speed manual I was hopeful of retaining the transmission to make driving the front wheels easier. As for batteries I expected to divide them between the engine bay & the boot (happy to sacrifice some space). As the car just commutes 10km each way per day range wasn’t a big issue as long as I could maybe get around 100km from a single charge that would do. It could sit on the charger all weekend. The car would be a project (toy) and as technology and my budget improved I would look at more a more powerful motor and better batteries. Cheers Jason.

    1. G’Day Jason,
      That sounds like a minit little project, shouldn’t be too hard to do either, as range wouldn’t be a huge issue to someone such as yourself. Especially with the ability to charge overnight such a short distance, regardless of your battery size, with that kind of short run, you’d actually get better performance out of the batteries by allowing them to run 2-3 days worth of travel between charges.

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