Backup charger using LiFePo4 batteries

[Cslagel]

I have a 2012 leaf with its original battery now down to 7bars 54% SOH. I’ve looked into batteries replacement but the cost is still too high here in Vancouver BC, it’s cheaper to replace the car. I decided while I wait for battery replacement cost to either drop or for the time for me to replace my car, and to invest in a backup battery system instead.
I’ve started by purchasing 2 12.8v Mini LiFePo4 100AH batteries and a 2000w pure sine inverter. This initial setup cost less than $1000cad.
This will allow me to charge a bit via my Level 1 charger. I plan to add more batteries up to 8 total that eventually will give me an estimated extra 60km. My initial setup should give 15k for those times I have to hunt around for charging station (when the planned one is busy or broken).

My reasons for this is that I can this setup for many other things, and if someone major happens to my car I probably wouldn’t be able to recover much of a battery upgrade cost.

I’ve also considered the weight, each of the batteries I’ve selected weigh 19lb each, the inverter is 8lb, so if I go got the max setup the total weight would 160lb. And total cost would be around $3000cad

 

[negue001]

Better buy 96 cells NMC 100+ah , swap with your actual cells and sell original cells.

 

[MikeinPA]

These batteries? https://www.litime.com/products/litime-12v-100ah-lithium-lifepo4-battery

 

[mrlithium]

Litime used to be called Amperetime .. before they disappeared. funny how the absolute cheapest stuff is the most promoted.

 

[Cslagel]

Better buy 96 cells NMC 100+ah , swap with your actual cells and sell original cells.

This isn’t something I can do myself or any shops nearby offer, the cost would be much higher and when I replace my car I wouldn’t be able to keep or reuse those cells.

Most my longer trip are for events where the car will be parked for the entire day at a park with no charging options. This system will allow me to charge a bit during the day making it easier to get to a charger or home after the event.

 

[OntarioSV2018]

I have a 2012 leaf with its original battery now down to 7bars 54% SOH. I’ve looked into batteries replacement but the cost is still too high here in Vancouver BC, it’s cheaper to replace the car. I decided while I wait for battery replacement cost to either drop or for the time for me to replace my car, and to invest in a backup battery system instead.
I’ve started by purchasing 2 12.8v Mini LiFePo4 100AH batteries and a 2000w pure sine inverter. This initial setup cost less than $1000cad.
This will allow me to charge a bit via my Level 1 charger. I plan to add more batteries up to 8 total that eventually will give me an estimated extra 60km. My initial setup should give 15k for those times I have to hunt around for charging station (when the planned one is busy or broken).

My reasons for this is that I can this setup for many other things, and if someone major happens to my car I probably wouldn’t be able to recover much of a battery upgrade cost.

I’ve also considered the weight, each of the batteries I’ve selected weigh 19lb each, the inverter is 8lb, so if I go got the max setup the total weight would 160lb. And total cost would be around $3000cad

I've been thinking about something similar. Amazon has some decent deals on LFP. You get better bang for your buck with 25.6V batteries, and 24V inverters are more efficient than 12V. 48V is also an option, but 24V is usualy easier to work with.

https://www.amazon.ca/ECO-WORTHY-LiFePO4-Rechargeable-Replacement-Household/dp/B0CJY2WBQR/

I was thinking of putting an inlet plug for charging like this: https://www.amazon.ca/Leviton-5278-CWP-Receptacle-Industrial-Grounding/dp/B003ATXIBG

and something like this to plug the car into itself. https://www.amazon.ca/AC-WORKS-ASOU.../dp/B07Q429WK5/ref=sr_1_45?crid=3K5Q9RXT64A6G

With cheap inverters, you usually want to run continuously with at least double the power you want to pull. A cheap 2000W inverter with a 4000W surge will likely burn out if you try running it for a few hours above 1000W. For a 12A 120V charger, I'd get at least a 3000W.

For Charging, I would use 2x 500W Computer power supplier in series to get 24V, and one of these https://www.amazon.ca/qazaa-Convert...B0CYCGT7CX/ref=sr_1_1_sspa?crid=1DUD1EU51GSDY to regulate the current and step up slightly to 28.8V needed to charge the LFP batteries.

 

[ericssonvacuum]

I've been thinking about something similar. Amazon has some decent deals on LFP. You get better bang for your buck with 25.6V batteries, and 24V inverters are more efficient than 12V. 48V is also an option, but 24V is usualy easier to work with.

https://www.amazon.ca/ECO-WORTHY-LiFePO4-Rechargeable-Replacement-Household/dp/B0CJY2WBQR/

I was thinking of putting an inlet plug for charging like this: https://www.amazon.ca/Leviton-5278-CWP-Receptacle-Industrial-Grounding/dp/B003ATXIBG

and something like this to plug the car into itself. https://www.amazon.ca/AC-WORKS-ASOU.../dp/B07Q429WK5/ref=sr_1_45?crid=3K5Q9RXT64A6G

With cheap inverters, you usually want to run continuously with at least double the power you want to pull. A cheap 2000W inverter with a 4000W surge will likely burn out if you try running it for a few hours above 1000W. For a 12A 120V charger, I'd get at least a 3000W.

For Charging, I would use 2x 500W Computer power supplier in series to get 24V, and one of these https://www.amazon.ca/qazaa-Convert...B0CYCGT7CX/ref=sr_1_1_sspa?crid=1DUD1EU51GSDY basket random to regulate the current and step up slightly to 28.8V needed to charge the LFP batteries.

Does using a 25.6V battery and a 24V inverter ensure the device's capacity?

 

[OntarioSV2018]

Does using a 25.6V battery and a 24V inverter ensure the device's capacity?

Yes, the cutout on many 24V inverters is about 20V-21V, and the overvoltage threshold is usually 32-33V.

That lines up nicely to squeeze all the capacity of LiFePo4 batteries.

LFP 25.6V batteries have a 0%-100% range of 20V to 29.2V, but to maximize cycle life, you can stay between 10% and 90% SoC, which is about 24.0V to 26.8V.