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Hello Group,
Today I am posting about a new battery pack I constructed from CHEAP IMR-18650 cells. I say cheap because these are on the cheap side of the market. I am a vapor and I often buy IMR cells for my vaporizer which are of much higher quality than these. The first thing I noticed when I took them out of the package was that they were very light compared to the higher quality ones I am used too. I suspect that they have lied about the capacity and filled them with far less active material than the quality cells used in vaping products, hence they are cheap. I knew that going in however and I wanted to see what could be done with them even if they do not have the advertised capacity.
This pack is constructed from 72 cells. I have three parallel sections of 24 cells which are then put into series to create a 12.6v pack at full charge. The cells were rated at 2500mah but as I have said I doubt they actually have that much capacity. My cost per cell with the two plastic end caps that form an interlocked frame was 76 cents per cell so this pack is roughly a 55 dollar investment.
Here are some shots of the top and bottom:
I have just completed the build and am currently doing a few initial test runs. I will be covering the exposed connections with shrink tape later on once I am sure I don't need access to that area anymore. Each of the three parallel string has a pos and neg lead connected via deans plugs so that I can check each string individually for balancing. Later on if I build more packs I can simply remove that and make some cross connections to convert the whole pack into a single parallel pack that would then become part of a series in a larger pack. That is why I laid them out physically all in the same direction instead of inverting the middle row.
I choose the IMR cells because with their chemistry they are able to handle large current drains and have a reputation for being much safer than ICR which is the typical Li-ION cell that has been out longer and is widely used for things like laptop batteries. For example in my vaporizer with the good cells I use IMR's and it takes two cells in series. When using the device I run a .25 OHM coil on it which results in about a 15A draw every time I take a puff. Granted this is not continuous but the point is that IMR's can give a lot of current. The downside of using IMR is that it inherently has much lower capacity. Generally you will only find IMR's up to about 2500mah but other lithium cells can go into 6000 and higher, they don't handle high draws well though.
I have not decided on exactly how I will use this pack but one idea I had is to pair it up with this little 400 watt inverter. I would only be pulling the battery pack down about half each time because it cuts off at 10.5v or so, but that would be very safe for the pack. In reality the IMR cells are nominal 3.7v with 4.2v being the top and 3v considered drained.
Today I am posting about a new battery pack I constructed from CHEAP IMR-18650 cells. I say cheap because these are on the cheap side of the market. I am a vapor and I often buy IMR cells for my vaporizer which are of much higher quality than these. The first thing I noticed when I took them out of the package was that they were very light compared to the higher quality ones I am used too. I suspect that they have lied about the capacity and filled them with far less active material than the quality cells used in vaping products, hence they are cheap. I knew that going in however and I wanted to see what could be done with them even if they do not have the advertised capacity.
This pack is constructed from 72 cells. I have three parallel sections of 24 cells which are then put into series to create a 12.6v pack at full charge. The cells were rated at 2500mah but as I have said I doubt they actually have that much capacity. My cost per cell with the two plastic end caps that form an interlocked frame was 76 cents per cell so this pack is roughly a 55 dollar investment.
Here are some shots of the top and bottom:
I have just completed the build and am currently doing a few initial test runs. I will be covering the exposed connections with shrink tape later on once I am sure I don't need access to that area anymore. Each of the three parallel string has a pos and neg lead connected via deans plugs so that I can check each string individually for balancing. Later on if I build more packs I can simply remove that and make some cross connections to convert the whole pack into a single parallel pack that would then become part of a series in a larger pack. That is why I laid them out physically all in the same direction instead of inverting the middle row.
I choose the IMR cells because with their chemistry they are able to handle large current drains and have a reputation for being much safer than ICR which is the typical Li-ION cell that has been out longer and is widely used for things like laptop batteries. For example in my vaporizer with the good cells I use IMR's and it takes two cells in series. When using the device I run a .25 OHM coil on it which results in about a 15A draw every time I take a puff. Granted this is not continuous but the point is that IMR's can give a lot of current. The downside of using IMR is that it inherently has much lower capacity. Generally you will only find IMR's up to about 2500mah but other lithium cells can go into 6000 and higher, they don't handle high draws well though.
I have not decided on exactly how I will use this pack but one idea I had is to pair it up with this little 400 watt inverter. I would only be pulling the battery pack down about half each time because it cuts off at 10.5v or so, but that would be very safe for the pack. In reality the IMR cells are nominal 3.7v with 4.2v being the top and 3v considered drained.
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