Disclaimer: I mention vendors below and use them as an example and as reference. This should not be considered an endorsement of said vendors!
In light of Will's recent video and some of the comments both there and on the forum, I thought it would be a good idea to do a full cost analysis of a DIY LiFePO4 battery with cells available at this moment. I'll compare the DIY build with a current off the shelf available system that is considered most 'bang for the buck' - at the time of writing the EG4 48V/100Ah rack mounted system coming in at $1500. The goal is not to make the absolute cheapest DIY version, but to make one with readily available, grade A, new cells that have been used and reviewed by many. I'm going to pretend to be in the US for this, even though in Europe we can do the same - we don't have the EG4 available at these prices. The total calculation does include things like BMS, bus bars and fuse in the DIY build so we can compare a complete system. As for shipping cost, I'll pretend the EG4 includes shipping, or that you can pick them up. The EVE cells I'm using as reference are advertised with free shipping.
Another reason for writing this is that there seems to be some confusion with a lot of people in comparing systems and doing the math. The Amp-Hour (Ah) unit still forms a great source of confusion for example. Also, it would be nice to do this calculation again in a year or so and compare the differences. In other words, at the very least it can be a historical record for comparing systems to in the future.
Let's start with leveling the playing field. The EG4 is a 5kWh battery pack. The most common and popular cells available right now are arguably the 304Ah EVE cells. So if we compare 3x the EG4 (15kWh) to 16x EVE 304 cells (15kWh) we're pretty much comparing apples to apples. At a cost of $4500 for the three EG4 systems we now have a price target to compare against.
For the cells, I'm using Docan as a reference: 304Ah EVE cells. These go for $158 per cell. As mentioned we need 16, so this brings the cost to $2528.
Of course, we need a BMS. I'm going to pick one I have experience with, and I'm not picking the cheapest one. The 200A with 2A balancing JK BMS bought from Aliexpress would set me back $185 with free shipping.
Bus bars. Since I'm lazy and didn't want to figure out where to get copper stock in the US and then drill them, I'll get them from the same place I would get the cells. Cost: $48 for 16.
I'm going to add a decent Class T fuse to the system. Personally I wouldn't use anything else, or at least, use it in combination with a breaker if you need to. Class T fuses are a bit hard to find at the moment, and expensive. I'll use the prices listed at Blue Sea. A 300A fuse will set you back around $45, and a holder will cost a additional $71. You could just use the same breaker they use in the EG4, or you can add it so you have an 'off' switch for the pack. The EG4 uses a Chint breaker, but I didn't find an equivalent from them for higher currents. Therefor, let's pick Schneider 250A 160V DC breaker instead, at a cost of $128. We don't really need both, but anyway, the breaker will add an on/off switch.
Adding this all together, we get to: $3005.
The one thing left to do is find a box to put it all into. This varies quite a lot depending on your requirements. If we pick a box like what Andy from Off Grid Garage put his first one in, something like this should do. Add another $75 for that.
That bring the total to $3080, compared to $4500 for the EG4. You can decide for yourself if it's worth it.
In light of Will's recent video and some of the comments both there and on the forum, I thought it would be a good idea to do a full cost analysis of a DIY LiFePO4 battery with cells available at this moment. I'll compare the DIY build with a current off the shelf available system that is considered most 'bang for the buck' - at the time of writing the EG4 48V/100Ah rack mounted system coming in at $1500. The goal is not to make the absolute cheapest DIY version, but to make one with readily available, grade A, new cells that have been used and reviewed by many. I'm going to pretend to be in the US for this, even though in Europe we can do the same - we don't have the EG4 available at these prices. The total calculation does include things like BMS, bus bars and fuse in the DIY build so we can compare a complete system. As for shipping cost, I'll pretend the EG4 includes shipping, or that you can pick them up. The EVE cells I'm using as reference are advertised with free shipping.
Another reason for writing this is that there seems to be some confusion with a lot of people in comparing systems and doing the math. The Amp-Hour (Ah) unit still forms a great source of confusion for example. Also, it would be nice to do this calculation again in a year or so and compare the differences. In other words, at the very least it can be a historical record for comparing systems to in the future.
Let's start with leveling the playing field. The EG4 is a 5kWh battery pack. The most common and popular cells available right now are arguably the 304Ah EVE cells. So if we compare 3x the EG4 (15kWh) to 16x EVE 304 cells (15kWh) we're pretty much comparing apples to apples. At a cost of $4500 for the three EG4 systems we now have a price target to compare against.
For the cells, I'm using Docan as a reference: 304Ah EVE cells. These go for $158 per cell. As mentioned we need 16, so this brings the cost to $2528.
Of course, we need a BMS. I'm going to pick one I have experience with, and I'm not picking the cheapest one. The 200A with 2A balancing JK BMS bought from Aliexpress would set me back $185 with free shipping.
Bus bars. Since I'm lazy and didn't want to figure out where to get copper stock in the US and then drill them, I'll get them from the same place I would get the cells. Cost: $48 for 16.
I'm going to add a decent Class T fuse to the system. Personally I wouldn't use anything else, or at least, use it in combination with a breaker if you need to. Class T fuses are a bit hard to find at the moment, and expensive. I'll use the prices listed at Blue Sea. A 300A fuse will set you back around $45, and a holder will cost a additional $71. You could just use the same breaker they use in the EG4, or you can add it so you have an 'off' switch for the pack. The EG4 uses a Chint breaker, but I didn't find an equivalent from them for higher currents. Therefor, let's pick Schneider 250A 160V DC breaker instead, at a cost of $128. We don't really need both, but anyway, the breaker will add an on/off switch.
Adding this all together, we get to: $3005.
The one thing left to do is find a box to put it all into. This varies quite a lot depending on your requirements. If we pick a box like what Andy from Off Grid Garage put his first one in, something like this should do. Add another $75 for that.
That bring the total to $3080, compared to $4500 for the EG4. You can decide for yourself if it's worth it.
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