A member asked me for some info on my DIY lithium batteries, and in case anyone else has anything to say on the topic, figured I'd start a thread for it.
I built a LiFePO4 battery. It cost me about $600 for a 200AH battery. It's almost double the capacity and 1/2 the weight of the two lead batteries it replaced.
I built it with the large prismatic(which just means flat, rather than round) cells. So, only 4 cells. The batteries came w/ bus bars to connect the four cells together.
You need a BMS (Battery Management System) which mostly just stops individual cells from becoming over charged. It also cuts power if too much current is drawn, and has limited cell balancing capabilities.
I used a Daly 100A BMS. Ideally, I'd have used a larger 200A unit, but those are more expensive. And, I'll never pull more than 100A with my power needs, so good enough. Some of the nicer BMS's have bluetooth and will give you info about individual cell voltage. The one I got does not, but I have RC gear which is able to tell me the same info if I need to know. So I installed a standard RC lipo balance connector to my battery, just to make it compatible w/ a whole world of RC gear.
That's it, for the basics. Tightly tape it all together, and you could be done.
Details and ramblings..
These are relatively new, so I guess no one really knows the life and durability.
There are rumors that these are taken out of electric buses in China after they reach 80% capacity, and then resold as lower capacity cells. Some people say that's why some cells of the same size might be 150ah, or 120ah. Other people say it doesn't matter, and even more people say that's BS, and they're new. People say to make sure to buy "grade a, new 2020 (or 20201)" cells and BLS is a known good vendor, but a bit on the high price side.
Some say the cells should be in compression. They put plywood or aluminum on the ends of the row of cells with threaded rod going from front to back. Then tighten them all until snug. Most say that for our use, it doesn't matter. For higher current, like running a motor or something, it does matter.
LiFePO4 batteries cannot be charged below freezing. So, either accept that (I'd assume most days you're camping will be above freezing, even if the mornings are not). Or build a heater. I built a heater. I found some 12v heating pads on Amazon, and there are controllers you can buy, which will turn on the heater at a set voltage, and turn it off at another. I haven't done that yet... I had a small inverter and some seed tray heating pads, so I wrapped the battery in the heating pads, and then put foam around them, and taped all that together. To use it, I clip the little inverter to the battery leads and power the heating pads with it. I manually control it, heh.. Plug it in in the morning. Unplug an hour or so later.
I'll post links, but like I said, I have not built the heater yet and verified it works well. (it should)
Heating Pads:
https://www.amazon.com/Icstation-50X100mm-Silicone-Electric-Temperature/dp/B07PFHLP53/
Temp Controller:
https://www.amazon.com/gp/product/B076Y5BXD9
BMS: (There are much better ones, but this is what I used)
https://www.amazon.com/DALY-LiFePO4-Battery-Protection-Balance/dp/B08JBV1X28/ref=psdc_10063711011_t2_B08794B2G8
Cells: well, the ones I got are no longer listed. I'll link to some BLS ones, as they're probably safe. They are more expensive.
https://www.aliexpress.com/item/4001016025169.html
I sealed my battery door, so the vents are no longer vents. At some point, if this battery works out well in the long term, I'll probably rebuild that entire side of the camper. The battery takes up much less space than the lead, and it wants to be in interior conditions. I could definitely get another cabinet over there w/ a redesign.
I built a LiFePO4 battery. It cost me about $600 for a 200AH battery. It's almost double the capacity and 1/2 the weight of the two lead batteries it replaced.
I built it with the large prismatic(which just means flat, rather than round) cells. So, only 4 cells. The batteries came w/ bus bars to connect the four cells together.
You need a BMS (Battery Management System) which mostly just stops individual cells from becoming over charged. It also cuts power if too much current is drawn, and has limited cell balancing capabilities.
I used a Daly 100A BMS. Ideally, I'd have used a larger 200A unit, but those are more expensive. And, I'll never pull more than 100A with my power needs, so good enough. Some of the nicer BMS's have bluetooth and will give you info about individual cell voltage. The one I got does not, but I have RC gear which is able to tell me the same info if I need to know. So I installed a standard RC lipo balance connector to my battery, just to make it compatible w/ a whole world of RC gear.
That's it, for the basics. Tightly tape it all together, and you could be done.
Details and ramblings..
These are relatively new, so I guess no one really knows the life and durability.
There are rumors that these are taken out of electric buses in China after they reach 80% capacity, and then resold as lower capacity cells. Some people say that's why some cells of the same size might be 150ah, or 120ah. Other people say it doesn't matter, and even more people say that's BS, and they're new. People say to make sure to buy "grade a, new 2020 (or 20201)" cells and BLS is a known good vendor, but a bit on the high price side.
Some say the cells should be in compression. They put plywood or aluminum on the ends of the row of cells with threaded rod going from front to back. Then tighten them all until snug. Most say that for our use, it doesn't matter. For higher current, like running a motor or something, it does matter.
LiFePO4 batteries cannot be charged below freezing. So, either accept that (I'd assume most days you're camping will be above freezing, even if the mornings are not). Or build a heater. I built a heater. I found some 12v heating pads on Amazon, and there are controllers you can buy, which will turn on the heater at a set voltage, and turn it off at another. I haven't done that yet... I had a small inverter and some seed tray heating pads, so I wrapped the battery in the heating pads, and then put foam around them, and taped all that together. To use it, I clip the little inverter to the battery leads and power the heating pads with it. I manually control it, heh.. Plug it in in the morning. Unplug an hour or so later.
I'll post links, but like I said, I have not built the heater yet and verified it works well. (it should)
Heating Pads:
https://www.amazon.com/Icstation-50X100mm-Silicone-Electric-Temperature/dp/B07PFHLP53/
Temp Controller:
https://www.amazon.com/gp/product/B076Y5BXD9
BMS: (There are much better ones, but this is what I used)
https://www.amazon.com/DALY-LiFePO4-Battery-Protection-Balance/dp/B08JBV1X28/ref=psdc_10063711011_t2_B08794B2G8
Cells: well, the ones I got are no longer listed. I'll link to some BLS ones, as they're probably safe. They are more expensive.
https://www.aliexpress.com/item/4001016025169.html
I sealed my battery door, so the vents are no longer vents. At some point, if this battery works out well in the long term, I'll probably rebuild that entire side of the camper. The battery takes up much less space than the lead, and it wants to be in interior conditions. I could definitely get another cabinet over there w/ a redesign.
