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Old 12-16-2021, 10:27 AM   #1
Mini-Skoolie
 
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Lithium Battery Charging

So I think I went and did a dumb thing. I purchased a Ampere Time 12V 300Ah Lithium LiFePO4 Battery ($1,139!), but then it was sitting for awhile, so I went to charge it to keep it "up". Unfortunately, after charging I read a passage somewhere that charging it as a regular 12 V battery could damage the Lithium battery, which I did for about a day (it never fully charged). I've just purchased a specialized Lithium batter charger, but did I screw up and kill the battery? If I messed up, is there a way to fix this stupid blunder?

Thanks!

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Old 12-16-2021, 10:56 AM   #2
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I would guess that nothing bad happened if you didnít charge it all the way. You really need to keep the voltage lower than 14.6 to keep it safe but thereís a good chance if you have a built in bms it would do that for you.

Lithium batteries are happiest at mid capacity and not fully charged or discharged, so itís okay to leave it in the middle most of the time if youíre not using it, unlike lead acid.

I would check the voltage while resting and as long as itís around 13.2 - 13.6 (prolly should double check) itís a good place to let it sit. If itís much higher than that I would draw it down with a load until it rests somewhere in that range.
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Old 12-16-2021, 11:01 AM   #3
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i have only used a tradional charger to charge my big lithium battery.

my understanding is that while it leaves some performace on the table, the standard charger is fine. it doesnt make it up to 100% (voltage to low), therefore increasing life for the lipo battery. charging to 80% puts the life at these batteries over 20years, vs 100% charge and shorter life.

others are wiser about these issues. just my understanding and actions.
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Old 12-16-2021, 02:03 PM   #4
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Thank you so much! You have put my mind at ease. Unfortunately, I don't (yet) have a way to measure the exact voltage (only % full), so I will get what I need to do that. Excellent.

Cheers,
Jim
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Old 12-16-2021, 02:04 PM   #5
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Excellent! Thanks!
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Old 12-17-2021, 03:51 AM   #6
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Quote:
Originally Posted by jch511 View Post
So I think I went and did a dumb thing. I purchased a Ampere Time 12V 300Ah Lithium LiFePO4 Battery ($1,139!), but then it was sitting for awhile, so I went to charge it to keep it "up". Unfortunately, after charging I read a passage somewhere that charging it as a regular 12 V battery could damage the Lithium battery, which I did for about a day (it never fully charged). I've just purchased a specialized Lithium batter charger, but did I screw up and kill the battery? If I messed up, is there a way to fix this stupid blunder?

Thanks!

As others have said:
1. you probably didn't do any real harm
2. There is no such concept as 'keeping up' a lifepo4 battery. Its the opposite of what you want to do from a battery health perspective. Unlike lead acid batteries lifepo4 never need or want to be kept at 100%, the only reason we charge lifepo4 batteries to full or near full is because we want the capacity. You never need to charge a lifepo4 to full just becuase you think it might need it. No real 'harm' is done in the short term if you keep it within its normal voltage range (2.5V to 3.65V per cell) but it will take a toll on cycle life over time if done repeatedly.
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Old 12-22-2021, 04:58 PM   #7
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You can charge lithium with a conventional charger but you should study up on the the details and differences. One that often gets by people is the rate of charge. Consult the mfg. For mine the mfg advice is not more than 50A. I charge at 30A. There are people around who think that dumping juice in at 100A is cool. Study up.
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Old 12-25-2021, 09:49 PM   #8
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@jch511, for future reference...



Here are a couple links that provide a wealth of information on lithium-chemistry batteries. Not a complete education on the subject, and probably some info that's not directly applicable to your situation, but still good stuff. No matter how 'easy' manufacturers try to make lithium to implement, it's not a direct plug-n-play replacement for lead acid, and not knowing what you're doing could lead to very costly (money, property, maybe even lives) mistakes. At a bare minimum, you'll learn to get the most out of it while protecting and prolonging your significant investment. Hope this helps! (BTW, don't let the bit about boats turn you off. The second link is an exceptional article by a cat you really knows his stuff, and 99.9% of it is just as applicable to an RV/Skoolie).



https://batteryuniversity.com/articl...ased-batteries


https://marinehowto.com/lifepo4-batteries-on-boats/
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Old 12-26-2021, 01:56 AM   #9
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The Marinehowto article posted above is one of the absolute best introductions to LFP I have encountered. I highly suggest reading it. But to the totally uninitiated the detail can be overwhelming.


Here is a good shorter primer that might be a better first read for beginners:
How to find Happiness with LiFePO4
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Old 12-27-2021, 03:27 PM   #10
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Thank you so much! This is one of those things where you don't know what you don't know, so these links will help greatly. Thanks!

Jim
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Old 12-27-2021, 03:28 PM   #11
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Quote:
Originally Posted by dzl_ View Post
The Marinehowto article posted above is one of the absolute best introductions to LFP I have encountered. I highly suggest reading it. But to the totally uninitiated the detail can be overwhelming.


Here is a good shorter primer that might be a better first read for beginners:
How to find Happiness with LiFePO4
Wow, I am getting such great feedback from this forum. Thank you all for these very valuable resources!

Cheers,
Jim
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Old 01-01-2022, 05:49 PM   #12
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You can do all this with parts that will fit in a thimble

Diodes. Look them up. (A one way valve for current)
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Old 01-20-2022, 10:23 AM   #13
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Quote:
Originally Posted by dzl_ View Post
As others have said:
1. you probably didn't do any real harm
2. There is no such concept as 'keeping up' a lifepo4 battery. Its the opposite of what you want to do from a battery health perspective. Unlike lead acid batteries lifepo4 never need or want to be kept at 100%, the only reason we charge lifepo4 batteries to full or near full is because we want the capacity. You never need to charge a lifepo4 to full just becuase you think it might need it. No real 'harm' is done in the short term if you keep it within its normal voltage range (2.5V to 3.65V per cell) but it will take a toll on cycle life over time if done repeatedly.
I am reading back over the messages on this thread and I don't know if I ever thanked you for your response--that was something I didn't know and it is VERY useful for me to know that as I try to work the power budget for the bus. THANKS!

Jim
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Old 01-20-2022, 10:25 AM   #14
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Originally Posted by jackdebear View Post
You can charge lithium with a conventional charger but you should study up on the the details and differences. One that often gets by people is the rate of charge. Consult the mfg. For mine the mfg advice is not more than 50A. I charge at 30A. There are people around who think that dumping juice in at 100A is cool. Study up.
In looking back over the comments on this thread, I don't know if I ever thanked you for this very helpful information. In fact, I DO have a friend that thinks juicing the buhjeezus out of the battery is a good thing (but I didn't do that!), so THANKS!

Cheers,
Jim
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Old 01-20-2022, 10:27 AM   #15
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Quote:
Originally Posted by dzl_ View Post
The Marinehowto article posted above is one of the absolute best introductions to LFP I have encountered. I highly suggest reading it. But to the totally uninitiated the detail can be overwhelming.


Here is a good shorter primer that might be a better first read for beginners:
How to find Happiness with LiFePO4
I don't know if I ever got back to you to thank you for these great references. I wouldn't call myself an expert on it now, but I certainly learned A LOT from those reads! Thanks!

Jim
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Old 01-20-2022, 10:29 AM   #16
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Quote:
Originally Posted by Mekanic View Post
You can do all this with parts that will fit in a thimble

Diodes. Look them up. (A one way valve for current)
Say, Mekanic, I don't think I ever thanked you for this info, but I wanted to ask (and forgot) what you meant by "you can do all this with [diodes]". What did you mean by that? Somehow I lost the context. I guess you can tell I know very little about electronics and usually leave the complex stuff to the pros.

THANKS!

Cheers, Jim
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Old 01-20-2022, 07:37 PM   #17
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Quote:
Originally Posted by dzl_ View Post
The Marinehowto article posted above is one of the absolute best introductions to LFP I have encountered. I highly suggest reading it. But to the totally uninitiated the detail can be overwhelming.


Here is a good shorter primer that might be a better first read for beginners:
How to find Happiness with LiFePO4
Covers all the important points. Good reference for beginners.
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Old 01-21-2022, 12:56 PM   #18
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A question about where to place my batteries:
After reading this thread, I am considering the use of LiFePo4 batteries in my bus. From what I have read so far, mounting them in the trunk of the bus (under floor in Crowns) is not a good option since I live where -40 degrees is possible (already experienced -25 here). Mounting them next to the inverter seems like a good idea. The batteries I looked at are sealed so it seems this is a promising way to do it.


What is the experience of others who have used the LiFePo4 batteries?

The RV charger I am using will charge up to 65 amps and the voltage is limited.
The solar array will be capable of maybe 70 amps.
The second alternator is capable of 250 amps, and has remote monitoring capability (I can control output voltage using connection at batteries that does not flow any real current. This is used to overcome voltage loss through high current cables).
Using the remote voltage monitoring I can make sure the alternator voltage never gets too high at the batteries. The batteries I am looking at have internal BMS.


The inverter is mounted inside over the forward rear axle (tandem axles). I would use avionics shock mounted trays like I did for the inverter.
I would never put lead acid batteries in this location because of corrosive issues.
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Old 01-21-2022, 02:01 PM   #19
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Quote:
Originally Posted by flattracker View Post
A question about where to place my batteries:
After reading this thread, I am considering the use of LiFePo4 batteries in my bus. From what I have read so far, mounting them in the trunk of the bus (under floor in Crowns) is not a good option since I live where -40 degrees is possible (already experienced -25 here). Mounting them next to the inverter seems like a good idea. The batteries I looked at are sealed so it seems this is a promising way to do it.
For the health of the batteries (avoiding excess temps either way), inside is definitely preferable to to outside. But that's not to say there aren't still environmental concerns. Unless your space remains conditioned year-long, it will be just as cold or hot inside as out during periods of non-use. But at least then it's just a storage concern. If you have them outside during extreme temps when you're using the bus, then you're going to have to be concerned about keeping them at an appropriate temp when using/charging them. I'd personally much rather them inside. FWIW we're planning to bring our batteries in during periods of non-use during summer here (where excess temps would shorten cycle life).

Mounting them next to the inverter ranges from 'good idea' to 'absolutely necessary', depending on system voltage & your definition of 'near'. With a 12V bank, the voltage drop is so high, you want to do everything possible to shorten the run to the bare minimum. The higher the bank voltage the longer your run can be without using ridiculously-large (and expensive) cabling, so if you're at 24 or 48, you can get away with a bit more. Plus there's the issue of where they're running & what they're running through... penetrations must be protected to prevent shorting, and even then: no penetration is better than one.

Quote:
The RV charger I am using will charge up to 65 amps and the voltage is limited.
The solar array will be capable of maybe 70 amps.
The second alternator is capable of 250 amps, and has remote monitoring capability (I can control output voltage using connection at batteries that does not flow any real current. This is used to overcome voltage loss through high current cables).
Using the remote voltage monitoring I can make sure the alternator voltage never gets too high at the batteries. The batteries I am looking at have internal BMS.

1) Does the RV charger offer a profile compatible with lithium chemistries?
2) Gotta make sure any combined charging sources (at the same time) don't exceed your max charging rate of your bank, at a minimum.
3) A DC-DC charger like the Victron Orion TR might be a good option for charging via alternator (lithium charging profiles, models that convert from 12 to 24, etc), but you're certainly not going to get the full output of your alternator through it. I think the max amp output is 30, but I could be wrong.

Quote:
The inverter is mounted inside over the forward rear axle (tandem axles). I would use avionics shock mounted trays like I did for the inverter.
I would never put lead acid batteries in this location because of corrosive issues.

That tray for your inverter is awesome!
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Old 01-21-2022, 02:49 PM   #20
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Thanks for the compliment on the inverter mounts.
The RV charger has multiple modes and is user adjustable on output voltage. (advertised as compatible with lithium batteries)

The RV charger doesn't charge when the engine is running thus the alternator output isn't combined with the RV charger. The RV charger runs from outside (shore) power or from the generator. It seems that if the solar charge controller is compatible with LiFePo4 batteries that part would be OK.
I guess controlling the alternator voltage would be key to all working together. I am looking at how to determine when the batteries would be fully charged to assure that the alternator voltage would drop to about 13.6 volts. Since the alternator has the remote sensing (monitoring feature), providing a means to lower the output voltage to the batteries is the trick.

In the at rest situation (solar only) shouldn't be an issue as I will use 4 batteries that can safely handle the possible 70 amps of current flow.
Hooked up to outside power with both solar and RV charger power I am thinking that once the voltage is high enough the RV charger and/or solar charge controller will limit output voltage.


I agree with you about inside temperature being an issue. I found that the bus didn't get hot enough inside to be an issue even when 100 degrees outside (windows open).
Winter could still be an issue. I think your approach that removal of the batteries to inside for winter is a good idea. That will bring another issue to solve as my solar charge controller would be damaged if no load is present. Since I planned on installing a cross connect switch between the original bus electrical system and the RV electrical system this could work to keep the bus batteries charged in the winter, and keep a load on the solar charge contrroller



Thanks for the info.
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