(This question was prompted by a different thread, but I thought it may warrant a separate thread.)If I get Lithium batteries but my converter is old school, how much capacity (amp/hours) will I lose? I know the old converter will not fully charge Lithium batteries. For what it is worth, I often connect a 120 watt solar panel to my batteries and often can boondock for a week without any other charging device. That charge does not go through my converter -- I just use alligator clamps from my solar panel to my battery.Thanks in advance for your collective wisdom.(And yes, I know I should update my old converter, but I don't want to do that unless I have to.)

profdant139 wrote:(This question was prompted by a different thread, but I thought it may warrant a separate thread.)If I get Lithium batteries but my converter is old school, how much capacity (amp/hours) will I lose? I know the old converter will not fully charge Lithium batteries. It is impossible to tell unless we know the output of your converter, so you can go by that chart to guess approximately where you will be. one other thing to consider is whether or not your battery has balancing (active or passive) and what that setting is at. part of the issue with not having enough charge voltage is you don't hit the level your balancing is set for, and you never balance your cells, this causes the week cell to get weaker and the strong to get stronger so gradual over time you lose capacity as you only have the capacity of your weakest cell. also the table PT posted is not for charging it is resting voltage to get 100% capacity you need to charge to 14.6V so just having a converter that pouts out 13.6 will never quite make it to fully charged and it is a big issue as people see the improper chart that PT posted where the real one has the word "resting" after the 13.6 and has another row on top that says 14.6 with "charging" in small letters. if you don't mind losing some capacity you can charge to a lower level so say 13.3V, that will give you somewhere between 70 and 99 depending on how accurate your measuring the voltage, but we will say 85 to 90% assuming accurat measurment. if you cant access your balancing start voltage you still need to charge it to 100% once and a while to make sure it stays top ballanced. if you can access it, then you can change that volate for balancing to reflect what voltage you are using . so for 13.3V you would simply devide that by 4 and set your balancing start voltage to 3.325V and your cells will start balancing when they reach 13.3V and stay in ballance. there are a few more things to think about, the quality of the power supply its self. if it is a old one with unregulated/unfiltered dc then just change it as your volatage will float around a bit and its just not good for any 12V electronics. a single stage would be best if your never going to hit the 14.6V and stay under 13.6 but your better off to save up and get one that will allow you to customize the settings

Generally LFP will rest fully charged at 13.4 volts. Need a bit more to actually charge so 13.6 is fine but will take an extended period. 14.2 to 14.4 is certainly faster.The good thing is charging to 90%-95% will not cause a loss of capacity like lead-acid over time. And the LFP will definitely charge faster than lead-acid at similar voltage.Solar panel may eventually cause LFP to go to over volt protection if used during storage.

You need 14.2 to 14.6V (Per battery manufacturers specs) to get a full charge. 13.6 will likely negate the benefit of having spent all that money on Lipo4 batteries. Remember, that voltage has to first go to a BMS that's looking for an appropriate level to work with. Unlike older technology batts, the power doesn't just flow to the cells no matter whats feeding the battery. The BMS also needs the higher voltage to be able to activate its cell balancing mode, which is crucial to long term battery performance and life. Without the proper charge coltage, the battery will continuously degrade.You would also need to ensure the dusulphate mode (if it has one) is disabled.You'd be better off buying a small, 20A Lipo4 capable charger and using that to top it off.

Your existing converter will take care of most of the charging but take a longer time. Your solar should take care of reaching the higher voltages needed to reach 100% and equalizing the cells. That’s what I’m currently doing. I do have a lithium capable stand-alone charger that I used before permanently mounting solar panels.

How much capacity is lost if converter isn't Li-friendly?

StirCrazy
Moderator
Nov 03, 2023
Horsedoc wrote:
I don't have a dog in this discussion, but Lithium scares me with all the fires that have taken place. (Geezers get worried over nothing.) I think I will stay with the lead/acid and genset.

LiFePO4 is not a chemistry that is susceptible to thermal runaway and fires. While it is possible you pretty much have to shove an iron spike right through its shorting out all the internal layers and even then, it is mostly a smoke show. don't confuse Nicad and nickel metal hydride with LifePo4
Boomerweps
Explorer
Nov 03, 2023
My SIL went to a Yamaha ATV mechanics course and they were big on showing early Lithium battery fires. The tech were told to walk away if a battery fire started and just protect the surrounding area.
He thought I was crazy installing LiFePO4 batteries under my TT bed.
If you do a little online research, you will find that LiFePO4 batteries are safer than all other batteries.
You can go online and watch Will Prose and others take a drill to them.
I’ve seen two battery fires in vehicles, one actually blew up. Standard Lead Acid.
Itinerant1
Explorer
Nov 03, 2023
Even after all these years folks still giving advice on lithium fires when not even talking about LiFePO4 chemistry being used in rv's. LOL
Horsedoc
Explorer II
Nov 04, 2023
Itinerant1 wrote:
Even after all these years folks still giving advice on lithium fires when not even talking about LiFePO4 chemistry being used in rv's. LOL

I believe I said I didn't want one. Go buy yourself a whole pile. Did you see any advice I gave? Nah, don't think you did.
Have a good day

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