When to recharge Li Time 100Ah mini lifep04 battery

[Bluenoser316]

This is my 1st post here.
I purchased a 100Ah Li Time lifep04 mini battery and am building a power box to use as a ham radio backup (run my ham radios from it daily instead of wall power), and maybe to run a few household things diring power outages, and I am charging this battery with the supplied Li Time 10A AC wall charger manually as I have no solar yet due to living constraints.
Forgive me for asking a totally basic question, but I have been trying to get a straight forward answer about when to recharge this battery for awhile now. Maybe I'm just not asking correctly, because either the question is avoided, or im told to ask LiTime (which i have repetitively) , or, I get a page and a half answer about the state of charge, a bunch of technical jargon ect ect, and still the answer isn't given.
I just want to know at what point when I run the battery down do I recharge it again. What point do I not go below?
It seems like a simple question, isn't it??

I have a renogy battery monitor, and I asked Li Time what settings to put into the monitor, and they replied with the following, but still didn't tell me when to actually recharge the battery after several times asking them, grrrr.

Renogy battery monitor settings:
-Capacity - 100Ah
-Full - 13.33v
-Zero V - 10.8v
-PowerOff - 10.8v (Li Time then told me switch it to 12v just to be safe)
-Alarm - 5Ah
-Atten - 0.2%

So, I entered these values into the battery monitor settings, but, i still do not know when to be triggered to plug in my charger and recharge my battery.

Do i recharge it when it hits 12.2v as I seen on a Will Prouse video? Will said never go below 12.2v.
Do i recharge it at 12v, as Li Time told me to enter 12v as an alarm?
Do i ignore the voltage and recharge it after it hits a certain Ah or percent charge left on my battery monitor, as someone else told me reading voltages was "old school" and no longer valid these days?
It seems like a simple answer to a simple question, yet, I can't seem to get a straight answer.

A straight answer would sound something like this for example: " yes, when the battery voltage drops to 12.2v, that is when you should recharge the battery to 100%, dont let it fall below 12.2v". Lol.
This is the info I'm after, of course I made that up, but you get the idea.

I hope someone here can help me with this, because as you probably noticed, I'm getting a bit frustrated. I'm happy to spend all the time in the world learning lifep04 battery theory, the how and why I should charge it ect ect, but first I just want to get into a routine of charging, using and recharging the battery, and need the basic parameters to do this!

Thanks in advance for your assistance.

 

[NVS]

Your battery monitor should be set to these parameters.

Renogy battery monitor settings:
-Capacity - 100Ah
-Full - 14.6v
-Zero V - 10.8v
-PowerOff - 10.8v (Li Time then told me switch it to 12v just to be safe)
-Alarm - 5Ah
-Atten - 0.2%

Is there a reason you can't leave the charger on all the time? If you just want the battery for backup power and you have a good charger you should keep it fully charged. Lifepo4 batteries charge to 14.6v but float at 13.6v.

I would recharge at 20% capacity. Your battery monitor if set right will tell you this.

Lifepo4 cells are usually rated at 2.5v to 3.65v which × 4 = 10v to 14.6v. The bms in the battery monitors the individual cell voltages and will turn off the battery if any one cell exceeds these voltages. At 10.8v your cell voltage is 2.7v per cell.
Li Time 12v recommendation each cell would be at 3v.

So my answer would be 20% of capacity as indicated by your battery monitor once the parameters are set correctly. Voltage on Lifepo4 batteries is really not a good determining factor to go by since the voltage curve is so small.

 

[Tomthumb62]

This is a big debate akin to religion.

I say don’t worry about it. Just use the battery.

Some say you can discharge to 0% regularly without affecting the useful life of the battery. Because they think (Will Prowse is one of these people) that the battery will die of old age faster than you can run through the 2000-5000 charge cycles the battery is rated for.

Others say different things. Such as try not to discharge below 20% on a daily basis.

So charge it when you want. Just don’t charge it to 100%, drain to 95% then charge to 100% and repeat that every day. Lithium batteries don’t like that. Let it get down to 80% or lower before charging. Use your shunt to know what the SOC is, ignore the voltage, because it’s very difficult to accurately measure lifepo4 SOC on voltage alone. Your battery monitor shunt is your friend.

 

[MiSh]

There is no correct answer when you need to recharge the battery. If you look at most Lifepo4 charge/discharge data sheets, they will show that the deeper the discharge, the shorter the life cycle of the battery. And, vice/versa the shallower the discharge, the longer the life cycle. All depends what you feel important. That said, I wouldn't be discharging to zero on a regular basis. As other posters stated above, discharging to 20% capacity seems to be the norm.

 

[richard cabesa]

This is a big debate akin to religion.

Or a “what oil to use” on a BMW motorcycle forum ?

Don’t ask me how I know.

For Fu’ks sake, just make sure there is oil in it

 

[Tomthumb62]

Or a “what oil to use” on a BMW motorcycle forum ?

Don’t ask me how I know.

For Fu’ks sake, just make sure there is oil in it

I prefer peanut oil in my beemer. Smells like a baseball game.

 

[Bluenoser316]

This is a big debate akin to religion.

I say don’t worry about it. Just use the battery.

Some say you can discharge to 0% regularly without affecting the useful life of the battery. Because they think (Will Prowse is one of these people) that the battery will die of old age faster than you can run through the 2000-5000 charge cycles the battery is rated for.

Others say different things. Such as try not to discharge below 20% on a daily basis.

So charge it when you want. Just don’t charge it to 100%, drain to 95% then charge to 100% and repeat that every day. Lithium batteries don’t like that. Let it get down to 80% or lower before charging. Use your shunt to know what the SOC is, ignore the voltage, because it’s very difficult to accurately measure lifepo4 SOC on voltage alone. Your battery monitor shunt is your friend.

Thanks for the reply.
Currently, I'm just using the battery to power my ham radio gear, mostly receiving, so, it draws about 1A, and around 12.5w or so, and it runs all day long like this. If I transmit, it draws about 17A as its a 100w transceiver. The weird thing is, that when I charge this battery with the Li time 10A AC wall charger, it only seems to charge at 13.8v, and at 9.8A or so, and when the battery reaches full charge, not 14.5v, and when uts fully charged, its sitting at around 13.4v. After several hours if resting, the battery voltage falls to 13.33v as it should.
The weird thing is this, I watch the Ah and "percent battery left" fall throughout the day, it drops to 99% , then, 97%, 95%, 93%, then 91%, and buy that time, the day is done, and i turn off my radio gear. Voltage sits at 13.28v when I turn off the radios. This all seems normal as the battery is slowly and lightly being drained by running the radios all day.
The next morning, I look at my battery monitor, and the Ah is 99Ah, the percent left is back up to 100%, and the time left is 99:59 again!
What's going on here?
The battery has topped itself back up to 100% according to the battery monitor for 2 days in a row since i charged it. Why?
I find it hard to figure out how to judge how much I've got left on the battery when it tops itself back up to 100% the next day.
Maybe I need to more deeply discharge the battery somehow with more of a load?

 

[MisterSandals]

If I transmit, it draws about 17A as its a 100w transceiver.

Is that 100W signal using 12.8V power = 7.8A signal and 9A of overhead (heat)?

12.5W x 12h (all day?) = 150Wh

12.8V battery x 100Ah = 1280Wh

150Wh daily receiving use / 1280Wh battery = 11.7% of capacity (more depending on transmit time of course)

 

[NVS]

Doesn't sound like your charger is charging your battery at the right voltage. When you are charging does the amp meter go to 0 amps or is it still giving you 2 or 3 amps going in? It should charge to 14.6v and float charge at 13.6v. Once you get your battery to 14.6 volts reset your amp meter to 100%

Double check your voltage output of the charger it should be at least 14.6v with no load. If not get a better charger.

 

[Bluenoser316]

Doesn't sound like your charger is charging your battery at the right voltage. When you are charging does the amp meter go to 0 amps or is it still giving you 2 or 3 amps going in? It should charge to 14.6v and float charge at 13.6v. Once you get your battery to 14.6 volts reset your amp meter to 100%

Double check your voltage output of the charger it should be at least 14.6v with no load. If not get a better charger.

Li time actually sent me this charger for free, as a recommendation to use instead of the generic 20A charger I bought on Amazon. It's a brand new Li Time charger. This is what it looks like when it is charging according to the Renogy battery monitor. There are no settings, you just connect the battery and plug it in. See the Li Time charger, ad well as the Amazon 20A one I no longer use.

 

[NVS]

Well the one they sent you says it's output is 14.6v, so it should fully charge your battery to 14.6v. So that is good. And after fully charging to 14.6v a lifepo4 will have a resting voltage of 13.6v. That is where you want your renogy shunt meter to read 100%.

On my shunt meter I had to completely discharge the battery then recharge it to 14.6v to get the meter calibrated. And now it's always right on the money.

 

[Bluenoser316]

Is that 100W signal using 12.8V power = 7.8A signal and 9A of overhead (heat)?

12.5W x 12h (all day?) = 150Wh

12.8V battery x 100Ah = 1280Wh

150Wh daily receiving use / 1280Wh battery = 11.7% of capacity (more depending on transmit time of course)

That's great to calculate all of that, but isn't that what rhe battery monitor is supposed to do for me?
Also, why is my battery going back to 100% by the next day after resting overnight?

 

[Bluenoser316]

Well the one they sent you says it's output is 14.6v, so it should fully charge your battery to 14.6v. So that is good. And after fully charging to 14.6v a lifepo4 will have a resting voltage of 13.6v. That is where you want your renogy shunt meter to read 100%.

On my shunt meter I had to completely discharge the battery then recharge it to 14.6v to get the meter calibrated. And now it's always right on the money.

Actually, the Li Time 10A charger only seems to charge at 13.4v for some reason, and not more than 9.87A as it's a 10A charger. I asked Li Time why it was only 13.4v instead of 14.6v, they just said "it is ok".
Li time also said the full resting voltage is 13.33v, which I have verified to be true for this battery, at least with the charger I have.

 

[NVS]

That's great to calculate all of that, but isn't that what rhe battery monitor is supposed to do for me?
Also, why is my battery going back to 100% by the next day after resting overnight?

I think that is happening because your shunt meter hasn't been calibrated to the correct voltage vs amp hours used.

I would leave your radio on until the BMS on the battery shuts off. Then recharge battery to 14.6v and etc that as your 100% charge level.

 

[NVS]

I would use the charger you bought on Amazon and set it to lifepo4 and let it charge to 14.6v.. I read the Amazon listing on that charger and it says it will bulk charge to 14.6 and then float charges at 13.6v.

All lifepo4 battery cells I have seen have voltages of 2.5 to 3.65v 4 of them together gives you 10v to 14.6v. Unless they are doing something funky with the settings in their BMS you should see these voltages.

I guess the lower voltage you are seeing is ok as long as you are getting 100ah out of the battery.

 

[Bluenoser316]

I would use the charger you bought on Amazon and set it to lifepo4 and let it charge to 14.6v.. I read the Amazon listing on that charger and it says it will bulk charge to 14.6 and then float charges at 13.6v.

All lifepo4 battery cells I have seen have voltages of 2.5 to 3.65v 4 of them together gives you 10v to 14.6v. Unless they are doing something funky with the settings in their BMS you should see these voltages.

I guess the lower voltage you are seeing is ok as long as you are getting 100ah out of the battery.

Even that Amazon charger only charges at 14.1v max, and at 15 to 16 amps, not 20A, that's how i ended up with the Li time charger, as I asked them why it only charged at 14.1v, so Li time just sent me a charger and said I could keep it lol. I thought that was nice of them.

 

[Bluenoser316]

I think that is happening because your shunt meter hasn't been calibrated to the correct voltage vs amp hours used.

I would leave your radio on until the BMS on the battery shuts off. Then recharge battery to 14.6v and etc that as your 100% charge level.

Neither of my chargers ever charge the battery to 14.6v, the amazon charger charges to max 13.68v, charger shows 14.1v) then, after a few hours settle down to 13.33v. Li time said this was normal.
The Li Time 10A charger charges at 13.4v @ 9.68A.

 

[400bird]

Are you checking voltage as it is charging (and reaching peak voltage) or some time after it is complete? The voltage settles down to something like 13.4 after charging, this is normal.

With your use, I'd either charge it every night (so I didn't forget to charge it for too many days) or wait until it gets to something like 50%
But, unlike lead, there's no rule about when it needs to be charged. With lead the rule is recharge once it hits 50% for best life. This doesn't apply, charge it whenever you want.
I'm guessing that this is why you aren't getting and answer, there isn't one.

 

[NVS]

I would use the Amazon charger. It got good reviews. You can also use both chargers at once to charge faster. The two together should give you close to 30amps

 

[Bluenoser316]

Are you checking voltage as it is charging (and reaching peak voltage) or some time after it is complete? The voltage settles down to something like 13.4 after charging, this is normal.

With your use, I'd either charge it every night (so I didn't forget to charge it for too many days) or wait until it gets to something like 50%
But, unlike lead, there's no rule about when it needs to be charged. With lead the rule is recharge once it hits 50% for best life. This doesn't apply, charge it whenever you want.
I'm guessing that this is why you aren't getting and answer, there isn't one.

So there's no threshold that I should never let it fall below?
I'm checking thr voltage worh my meter as it's charging yes, and it doesn't charge more than 13.4v@ 9.86A with the Li time charger.