LifePO4 vs AGM Batteries

[cdnred]

156Ah LiFePO4 battery (soon to be 246 with the addition of a second 90Ah battery)

As I was told, connecting my 40ah to 100ah in parallel wouldn't give me the 140ah that I was hoping to get so was I misinformed..? Something about the capacity difference being too far apart..? As you state you have a 156ah presently and plan to add another 90ah to give you 246ah total. How are you planning to connect it up to achieve that..? I'm a bit confused and not too electrically minded..

Helmuth

[cdnred]

As long as I don't use the heated hose, I use 8-10 amps per night (If I recall correctly). I assume you have a battery monitor in your teardrop you can test it with?

Tony

I just bought a Victron battery monitor the other day and will have to connect it up to test that out. If your DreamStation is only using 8-10 amps per nite then I won't even worry about getting another 100ah LifePO4, I'm good with what I've got. I've pulled my 40ah out of the TD for the winter but I could still try it out in the house to check that out..

Thanks for helpful info Tony..

Helmuth

[lfhoward]

156Ah LiFePO4 battery (soon to be 246 with the addition of a second 90Ah battery)

As I was told, connecting my 40ah to 100ah in parallel wouldn't give me the 140ah that I was hoping to get so was I misinformed..? Something about the capacity difference being too far apart..? As you state you have a 156ah presently and plan to add another 90ah to give you 246ah total. How are you planning to connect it up to achieve that..? I'm a bit confused and not too electrically minded..

Helmuth

Hi, I haven’t tested it yet with them both together, but the idea came from Andy on his Off Grid Garage YouTube channel:

https://youtu.be/bhCSccNsQOw?si=-B88C_90x1r365yg

Because LiFePO4 has a flat charge curve (meaning a battery at 30% charge and a battery at 70% charge can be at nearly the same voltage), you can charge them and run them in parallel. Each battery must have its own BMS, but a Victron battery monitor can keep track of the whole battery bank. Andy does a good job in his video. I’ve learned a lot from him that has directly impacted my trailer’s electrical system build. I keep wanting to improve it after I learn new things!

[cdnred]

Hi, I haven’t tested it yet with them both together, but the idea came from Andy on his Off Grid Garage YouTube channel:

https://youtu.be/bhCSccNsQOw?si=-B88C_90x1r365yg

Because LiFePO4 has a flat charge curve (meaning a battery at 30% charge and a battery at 70% charge can be at nearly the same voltage), you can charge them and run them in parallel. Each battery must have its own BMS, but a Victron battery monitor can keep track of the whole battery bank. Andy does a good job in his video. I’ve learned a lot from him that has directly impacted my trailer’s electrical system build. I keep wanting to improve it after I learn new things!

I watched his channel and saw that you can connected different LifePO4 ah rated batteries together in parallel. Maybe I missed it but I don't recall him mentioning that the ah combined would increase..? I did a search and came across on Quora where it did mention the increase in amps..

When batteries are connected in parallel, the total output amperage does increase. In a parallel connection, the voltage remains the same, but the capacity to deliver current (measured in amps) increases. This means that the total amperage available from the batteries is the sum of the individual amperages of each battery. However, it's important to ensure that the batteries are of the same voltage and type when connecting them in parallel to avoid potential issues.

Very confusing and causes me some concern since where I bought it they recommended against it. This was the LifePO4 that I was planning on getting off Amazon but now with Tony saying that his CPAP which I have also is only using 8-10 amps per nite, I may just stay with what I've got now (LifePO4 40ah) and avoid the issue..

https://www.amazon.com/gp/product/B08LD ... =UTF8&th=1

[Pmullen503]

That's why I suggested that you actually measure how much power your system will consume running on battery power.

Running batteries in parallel not only increases the maximum amps the pack is able to produce but the total watt hours. You really don't care about the maximum amps unless you are using it for something that requires a lot of amps like starting an engine. Even a middling LiFePO4 should be able do 5C discharge which would mean you could completely drain your battery in 12 minutes without damage. Good old A123 (in power tool packs) are rated at 20C.

[hidesertrocker]

I've learned a lot from Will Prowse's Youtube channel where he tears down LiPos. A lot are junk, but he comes up with some that are not and still inexpensive.

https://www.youtube.com/@WillProwse

Another good resource is the forum Will hosts:

https://diysolarforum.com/

[Tom&Shelly]

I did a search and came across on Quora where it did mention the increase in amps..

I'd be wary of getting any important technical information on Quora. As it happens, yesterday I wanted to whip up a quick FM antenna from speaker wire and looked at an article of theirs. It is not particularly correct.

Tom