Building a 230aH DIY Lithium Battery for our 4WD

A few months back I started looking at options for replacing our 150aH AGM battery in the canopy of our Isuzu Dmax. The battery was nearing 4 years old, and with a big lap of Australia approaching fast, I wanted to swap it out before it decided to die. After a heap of research, I went down the DIY lithium battery path, and ended up with a 230aH custom battery.

This was a fun project that I was prepared to wait the freight time for, and if you are interested in doing the same I’ve provided as much information as I can. Feel free to ask questions, and if I can answer them I will.

This post is not to encourage you to go and do the same, but just to show you what we did; I take no responsibility for your DIY lithium batteries!

Why did we move to lithium batteries?

There’s a heap of reasons why people are moving to lithium batteries today, and with the way pricing is going it will be a no brainer shortly. For us, I made the move because of the following reasons:

End of life for our AGM

I mentioned above that our 150aH Bosch AGM deep cycle battery was 4 years old, and we had a big lap of Australia planned where I wanted reliable power.

We literally live out of our Bushman Upright fridge, and having battery issues just wasn’t an option I was prepared to play with. 

On top of this, the battery is quite hard to remove, and would need new brackets made, which are far easier to do at home than on the road with basic tools. We probably would have gotten a few more years out of our AGM, but if it failed mid trip it would have been a major inconvenience

Needing more capacity

After really committing to running this blog full time, I found myself on a number of occasions running our 150aH AGM deep cycle battery down to around 50%, which I hated doing. This is about the normal recommended maximum consumption for an AGM; you can read more here; Are you damaging your 12V batteries?

This was mainly when you’d park in a shady area, and were charging camera and laptop batteries along with running the fridge, and could have been avoided by driving the vehicle around, or putting a solar blanket out, but I like to keep things simple and efficient, and we much prefer our roof rack mounted solar panel.

A 150aH AGM has a usable capacity long term of not much more than 75 aH, which doesn’t give you a whole lot of wiggle room. Lithium gives you a lot more usable capacity, and if you upsize, you get heaps more.

To learn something new

I’m always keen to learn more, and seeing how lithium batteries perform was a huge motivator to make the move.

This was especially the case with the DIY option, which we go into more below; buying cells, and a BMS and making it all work together was a good project, and I’ve always wanted to understand a bit more about 12V and general electrics.

Weight reduction

The weight reduction that you achieve when moving to lithium batteries is nothing short of astounding. We pulled our 43kg AGM out, and put about 18kg of lithium back in, and got 2 and a half times more usable power!

Our Dmax towing the Reconn R2 is only just legal, and I decided it was time to strip some weight out. If you want to know more about this, check out our Mobile Weighing post.

I wanted a backup power source

I’ve always tried to build independent electrical systems, so you don’t rely on two things being connected to make it work.

Our Reconn R2 hybrid camper now has 340aH of Renogy lithium batteries, which is fantastic for running our gear with minimal sunshine, but if we needed extra power, I now have the Dmax that I can use to move power across, or to run appliances off if we really need to.

My mate had already done a few

The final piece of the puzzle was simple; a really good mate of mine had been reading up, and building his own DIY lithium batteries for a while and was more than happy to help me get a DIY lithium battery set up in the Dmax. 

He’d found a solid supplier online, purchased a few units and played with them enough to know that they were decent. 

It fit well in the space

I’m all about putting any heavy items as far forward in the Ute Canopy as possible. This is to reduce the rear axle weight by getting rid of any leverage.

Our existing space right at the front of the canopy was tiny, and I was limited to slim line batteries over 150aH, but with the lithium cells you can make them in any shape you want. They can be as thin as 70 odd mm wide and really long like a sausage, or doubled up at 140mm wide, or in a number of different configurations.

See our electrical system on YouTube

Want to know more about our total electrical system in the Dmax and camper? We’re running 570Ah of lithium, and 920W of fixed solar, and here’s the vlog covering it all:

Why 230aH?

I could have gone with any different sized lithium battery; they start at 50aH, then 105, 230, 280 and 304aH. I considered a slightly smaller unit, but given the tiny increase in footprint and weight, it just didn’t make sense. Anything larger just seemed way overkill, and the price was decent for these cells.

A 105aH lithium would have given us a similar usable capacity to the 150aH AGM, at a tiny fraction of the weight and the size, but I wanted to increase our storage capacity and for the minor increase in price and size it made sense.

What did we buy?

The total purchase was 4 x 3.2V 230aH A grade prismatic cells, a cell balancer, Daly 150 amp BMS, Renogy shunt and battery monitor, some battery terminals, cable and other bits and pieces.

The BMS limits the discharge to 150 amps (actually we had it at 220 and it didn’t shut off!) and 150 amp charge. 

The cells are supposed to be good for 3500 cycles at 1C. They are 207mm tall, 174mm long and 54mm thick, and weigh just over 4kg each. 

The 1C means that you can discharge the entire battery over 1 hour, so pulling a whopping 230 amps, and the cells can be charged at a maximum of 230 amps too.

How much was it?

$766.35 for the cells

$31.50 for the cell balancer

$110 for the Daly 150 BMS

$100 for cable, lugs and other random bits

Plywood and screws were already in my garage

$100 for a Renogy 500A battery monitor and shunt 

Total of $1110 for 230aH, delivered to Perth in about 3 months

Building the lithium battery

I’ll be completely honest here, and say I had far less involvement in this project than I’d have liked to, simply due to time constraints trying to get everything ready for our lap of Australia.

I decided to build a plywood box to house the cells, and after discussing different orientations to make them fit into the Dmax properly, I knocked the timber up and dropped them off at my mates place. 

He did all the testing, balancing of the cells, installing the BMS and putting the rest of it together and kept me in the loop with what was going on.

I left about 70mm above the cells for the BMS, shunt and cell balancer, and it was only just enough. I’d leave more space next time.

The design allowed for 4 pieces of threaded rod to pull the end plywood piece inwards to apply some compression. I did a heap of reading on this, and decided its the biggest rabbit hole you can go down. In essence, some compression is good when the cells are at 50% SOC, but don’t overdo it.

I just tightened them gently and measured the deflection (after reading up on converting 12 PSI to nM and so on) and put a second nut in place with Loctite, so it couldn’t come loose.

We did put a few holes in the box for ventilation for the BMS, and its spaced off the lid to allow it to keep cool. We plan on being fairly gentle with this battery though; its not going to be doing 150A for huge periods.

Installing the lithium battery

The battery installation was fairly straight forward. I removed the existing AGM, which was insanely heavy, and the new lithium slid in just perfectly. I managed to get rid of the steel frame to support the battery, and some additional plywood that was lifting it up to give more room, which saved even more weight.

Once it was in place, I went about installing some aluminium angle, and timber supports bolted to the canopy, to ensure it would never move. Being much lighter, you need far less support to keep it in place; I had 6mm x 30mm flat bar in a custom bracket holding our 45kg AGM down!

The terminals made it easy to wire up, and it wasn’t much longer and I had the shunt live, and could see exactly what the battery was doing.

This is hugely appreciated, as we’ve always gone off a voltage gauge which is a rather unscientific and simple method, and I could never tell what the battery was actually doing. A shunt would have been very handy diagnosing charging issues with our Projecta DCDC, but you live and learn.

Using the existing DCDC without a lithium profile

For a week or so, I had the lithium battery hooked up to the original setup, which was a Projecta IDC25 DCDC charger without a lithium profile.

Some people will tell you this shouldn’t be done, but if you actually look into it there’s unlikely to be any harm. Providing the voltages are similar and it has no equalisation phase, the lead acid, or AGM charger will still charge the lithium, just not efficiently, and it will likely take longer.

I did have a number of instances where the Projecta didn’t disconnect after I turned the car off, and it was still pumping 400W from the front battery into the rear. I’m still puzzled by this, and just put it down to another random Projecta fault.

I actually ended up disconnecting the 12V feed into the DCDC, as I couldn’t trust that it wouldn’t flatten my cranking battery.

On another occasion, I plugged a separate solar panel with its own regulator into the front battery to try and charge it up, and when it got to 13.2V it turned the DCDC on, and was pushing 360W from the front battery to the rear.

I unplugged the solar, and the DCDC didn’t disconnect, until I’d run the vehicle and then shut it down. Strange, and annoying.

Swapping DCDC chargers and finishing it all off

About a week after finishing my part of the lithium battery, Stephen from Hunter Autoelectrics came to my place to finish it all off.

He ripped out the Projecta IDC25 DCDC and installed a 50 amp Renogy DCDC, removed the auto reset circuit breakers, mounted the shunt display, wired up a 2000W inverter and tidied it all up, along with wiring our new 600W of caravan solar panels into the hybrid camper trailer.

What other lithium batteries could we have purchased?

I went down the DIY lithium path to learn something new, and have a cost effective build. Of course, I looked at other options, and could have gone for a few different setups.

I did consider a Renogy 170aH or Renogy 200aH lithium battery, but both were too wide to fit up against the headboard, and I have more than enough Renogy products to test already.

You’d almost think we were sponsored by them (we are absolutely not, and never will be).

Custom Lithium do a 200aH slim line battery which would have worked, for around $1900.

DCS also do a 200aH slim line battery for $2350.

The main limitation was the limited width (anything over 150mm was pushing the friendship), and I wasn’t prepared to pay 2 grand for another battery.

Maybe I’ll live to regret this. Maybe I won’t. Time will tell, and I’ll let you know either way. I’d say the end result is a much better quality unit than some of the cheaper end lithium batteries on the market, and I’ve learnt a heap in the process.

Where did we get the cells from?

Our cells came from a reputable seller on Alibaba, who has been servicing the world for a number of years and has great feedback from a heap of different places.

That said, I take no responsibility for your experience with them; please do your own research and buy where you are comfortable with. Here’s the Alibaba link.

Would we do it again?

Yep, every day of the week. I’ve enjoyed learning a bit more about lithium batteries, saving a huge chunk of cash and I’ll be able to give a more accurate reply once we’ve given this thing a flogging off road, and running our induction cooktop or toaster for a few months on the road.

If it causes us grief without several solid years of use I might regret it then, but I reckon we’ve ended up with a product that will work well for a long time. 3500 cycles is depleting the battery every single day for 10 years, and I doubt we’ll ever get close to doing that.

Overall, I’d do this again, and absolutely again for static environments (I’d love to build an off grid house). A massive thanks goes out to Justin, who spent a fair chunk of his own time working on the battery and helping me out. 

Have you built your own lithium battery? What do you run in your 4WD or camper/caravan?

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