Don't charge your lithium batteries 100% (1 Viewer)

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Tombola

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Nov 21, 2020
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Ok so we know they dont like to be charged and held at 100% , but lots of us have electric drain, so the vans sitting on the drive, I charge it to 100% , unplug then over the days, say Im losing .5amp per hour,then techincially the battery is being used.

Does this mean 100% in this case is OK., as it isnt just " sat" at any period.
 
Jan 30, 2020
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Just a tad..
I really wouldn’t worry. The advice is ‘just’ to maximise the life of them. If you abuse them in every way ‘they’ say you shouldn’t, you will still get 2k charge cycles out of them. You’ll be wanting to swap to new fangled (better than lithium) salt or plutonium or kryptonite batteries way before you use up your charge cycles… 🤪
 
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Tombola

Tombola

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I really wouldn’t worry. The advice is ‘just’ to maximise the life of them. If you abuse them in every way ‘they’ say you shouldn’t, you will still get 2k charge cycles out of them. You’ll be wanting to swap to new fangled (better than lithium) salt or plutonium or kryptonite batteries way before you use up your charge cycles… 🤪
Good point.

Yeah this was my thinking. We can all talk about the 100% efficiency for as long as poss to the life of the batts.
But does a bit of degradation reeeealy matter
 
Apr 3, 2018
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Maybe it does.... maybe it doesn't,
Why not play safe and only charge to 80%, It will last for a good while if only discharging 0.5A.
 

bigtwin

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I charge to 100% most times I have had my lithium install for just short of a year used the van quite extensively and it's done 33 full cycles even if I only get 1000 cycles your looking at 30yrs use.

Charging to 100% is fine; it’s storing them at 100% that isn’t but even then that only results in a reduction in their life.

Ian
 

bigtwin

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Reduction by how much ?

Difficult to quantify but it’s a recognised phenomenon.

Most vehicles are run regularly and not stored so, in practice, for most people, it’s irrelevant.

Ian
 
Apr 27, 2016
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This compulsively keeping the battery at 100% is a throwback to lead-acid management, and is not a good idea for lithiums. If you want 100Ah of battery, it's best to get a 110Ah battery and charge it to 90%. I understand that you can in theory take the battery to 100% then stop charging, but how do you do that, and will you do it every time? Most chargers I've seen still have the lead-acid 'bulk, absorption, float' cycle that is decidedly suboptimal for lithiums. I would have thought by now we would get chargers appearing that will charge a battery to 90% then keep it there.
I charge it to 100% , unplug then over the days, say Im losing .5amp per hour,then techincially the battery is being used.
You need a charger that will charge up to a voltage where it's say 90%, then keep it at that voltage. The 0.5A draw will then come from the charger, not the battery. The battery will stay in the 90% state indefinitely, so it won't take any current from the charger, and won't be 'cycling', and any demand from the habitation circuitry will be met by the charger.
 
Last edited:
Dec 31, 2010
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This compulsively keeping the battery at 100% is a throwback to lead-acid management, and is not a good idea for lithiums. If you want 100Ah of battery, it's best to get a 110Ah battery and charge it to 90%. I understand that you can in theory take the battery to 100% then stop charging, but how do you do that, and will you do it every time? Most chargers I've seen still have the lead-acid 'bulk, absorption, float' cycle that is decidedly suboptimal for lithiums. I would have thought by now we would get chargers appearing that will charge a battery to 90% then keep it there.

You need a charger that will charge up to a voltage where it's say 90%, then keep it at that voltage. The 0.5A draw will then come from the charger, not the battery. The battery will stay in the 90% state indefinitely, so it won't take any current from the charger, and won't be 'cycling', and any demand from the habitation circuitry will be met by the charger.
With victron kit you can select your own charge profiles on the mains charger side and mppt side so can take your lithium to almost any state of charge you want.

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Jim

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Think we fret too much about our batteries, At different times I've ignored a lot of really good advice over the years. I once had an RV and ignored all the good advice, all at once. I had a whole load of batteries, different ages, makes and capacities, my lights stayed on.

I don't know what my lithium are doing between trips 100%- 90%, not than bothered. Maybe I'm just reckless and cavalier. In fact I must be because I never read the long list of precautions and side effects that come with a pack of Aspirin either. :D
 
Dec 2, 2019
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Also, some BMS's can be programmed to achieve the same. Mine have always been set at 90%.
With bms yes it’s possible to stop at 90% Soc.
But as others suggested above with voltage to determine the Soc? Not a chance. There’s more chances to win the lottery, rather than guess the soc of LFP by voltage. And specially the 90% Soc mark.
 
May 7, 2011
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I have lithium,so if my solar/EHU charges them up to 100% and keeps it topped up is that ok . I have a Victron charger/inverter, so is there something inbuilt to protect from over charging?


This compulsively keeping the battery at 100% is a throwback to lead-acid management, and is not a good idea for lithiums. If you want 100Ah of battery, it's best to get a 110Ah battery and charge it to 90%. I understand that you can in theory take the battery to 100% then stop charging, but how do you do that, and will you do it every time? Most chargers I've seen still have the lead-acid 'bulk, absorption, float' cycle that is decidedly suboptimal for lithiums. I would have thought by now we would get chargers appearing that will charge a battery to 90% then keep it there.

You need a charger that will charge up to a voltage where it's say 90%, then keep it at that voltage. The 0.5A draw will then come from the charger, not the battery. The battery will stay in the 90% state indefinitely, so it won't take any current from the charger, and won't be 'cycling', and any demand from the habitation circuitry will be met by the charger.
 
Sep 17, 2017
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I have lithium,so if my solar/EHU charges them up to 100% and keeps it topped up is that ok . I have a Victron charger/inverter, so is there something inbuilt to protect from over charging?
You might get slightly more life out of them if you only charge to 90%. But with the time lithium batteries are expected to last, I'm not sure if it's worth bothering about.

If you did want to do it, it would have to be done via the battery's BMS app (if it has one). You can't do it from your chargers because they only know battery voltage. Lithium battery voltage remains almost the same through most of the charge range, so external chargers are clueless.

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Apr 27, 2016
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You might get slightly more life out of them if you only charge to 90%. But with the time lithium batteries are expected to last, I'm not sure if it's worth bothering about.

If you did want to do it, it would have to be done via the battery's BMS app (if it has one). You can't do it from your chargers because they only know battery voltage. Lithium battery voltage remains almost the same through most of the charge range, so external chargers are clueless.
This is true, it's practically impossible to tell the difference between 90% and 100% SOC by using only the voltage. But that also means it's practically impossible to tell the difference between 100% and '110%', ie overcharging. And one big difference between lead-acid and lithium is that overcharging lithiums, even by a small amount, causes degradation.

It looks like the best way to do it is to communicate with the BMS to find the SOC, and use that as a cutoff. That's how it's done by Victron and other 'hybrid inverter' companies that do house PV/battery systems, and they have a list of compatible batteries they allow to be used. I don't know of anything like that in motorhomes, except maybe using Victron gear with Victron batteries or batteries on the compatible list. Trouble is, I think nearly all the compatible batteries are packaged as 48V, except the Victron ones.
 

Minxy

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In fact I must be because I never read the long list of precautions and side effects that come with a pack of Aspirin either. :D
They apparently can make you age quicker, get fat and go bald ... :eek::imoutahere:
 
Sep 17, 2017
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This is true, it's practically impossible to tell the difference between 90% and 100% SOC by using only the voltage. But that also means it's practically impossible to tell the difference between 100% and '110%', ie overcharging. And one big difference between lead-acid and lithium is that overcharging lithiums, even by a small amount, causes degradation.

It looks like the best way to do it is to communicate with the BMS to find the SOC, and use that as a cutoff. That's how it's done by Victron and other 'hybrid inverter' companies that do house PV/battery systems, and they have a list of compatible batteries they allow to be used. I don't know of anything like that in motorhomes, except maybe using Victron gear with Victron batteries or batteries on the compatible list. Trouble is, I think nearly all the compatible batteries are packaged as 48V, except the Victron ones.
The BMS should block any attempt to overcharge. Your chargers don't need to know. All they'll see is that the current suddenly drops to zero when you hit the limit.
 
Jul 5, 2013
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Can anybody advise me as to how to keep my LiFePo4 batteries at 80% ( or any other % I want) when not using the motorhome. I park on my drive and I keep the the EHU plugged in all the time, mainly to keep the cab battery fully charged via the trickle charge on my EBL. The EBL does not charge my leisure batteries at all.

My set up for charging the leisure batteries has a Votronic B2B and MPPT solar regulator, a Victron BMV 700 battery monitor and a Victron IP22 20A mains charger. At the moment the IP22 and solar keep the batteries fully charged and I haven't found a way to change that to just keep them at 80% by changing the settings on the IP22 or the BMV 700. I know I can't do it on the solar regulator, but I can isolate that if needs be. But how can I change the settings on the IP22 or the BMV700 to just maintain the batteries at 80%.

I can access my batteries BMS by Bluetooth, but that only allows me to see what state they are in, I can't use it to change any parameters.

Would be grateful for any advice.

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Dec 31, 2010
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Dave, how do you do that? Can't find anything in the instructions for my Victron IP22 mains charger to do that.
Not sure with your charger but can you not set the absorption voltage to say 13.9v and float to 13.4v not sure what your batteries are and what the recommendation is for charging so can't really comment. If your BMS is a decent Bluetooth one you could discharge your battery then switch of the charge function.
I tend to always charge to 100% then switch the solar off and just let the battery discharge then every so often if needed re connect the solar and charge or charge fully with your charger and repeat the process if needed.
 
May 7, 2016
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How many off the shelf batteries have a programmable BMS? I am rather glad that my Relion doesn’t, just something else to worry about setting up correctly and getting wrong. My BMS is a simple safety cutoff for extremes that would seriously damage the battery. Most consumers want to fit and forget. If my forget approach knocks a few cycles off the battery life so be it, I am not counting them and therefore I will not be disappointed. After 5 years of use I haven’t noticed any change in its performance. The price I paid for the battery equates to about 30 nights on a CAMC site. I have probably already paid for it by sometimes staying at cheaper locations without an EHU.
 
Dec 31, 2010
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Dave, how do you do that? Can't find anything in the instructions for my Victron IP22 mains charger to do that.
Just quickly looked at the manual you can set up your own presets in advanced settings create one and may be call it storage mode and put the settings in as above or even lower if you want.
 
Dec 31, 2010
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How many off the shelf batteries have a programmable BMS? I am rather glad that my Relion doesn’t, just something else to worry about setting up correctly and getting wrong. My BMS is a simple safety cutoff for extremes that would seriously damage the battery. Most consumers want to fit and forget. If my forget approach knocks a few cycles off the battery life so be it, I am not counting them and therefore I will not be disappointed. After 5 years of use I haven’t noticed any change in its performance. The price I paid for the battery equates to about 30 nights on a CAMC site. I have probably already paid for it by sometimes staying at cheaper locations without an EHU.
I suppose if you want one size fits all settings that's the way to go me I like to be able to tailor things to what I want not what other people think I want.

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Last edited:
Apr 24, 2018
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Whether it is safe to leave a charger permanently connected and lithium batteries at 100% is down to the type of charger used. If you have done a straight battery swap and are using the same ‘dumb’ charger that was designed for lead acid, then it will be detrimental to the lithiums as it can not switch to the lower float profile when the batteries are charged - this will result in overcharge and ultimately damage to the batteries.

If you are using a dedicated lithium battery charger, or an ‘intelligent’ one that can be switched to a lithium profile you will be fine.

The ability to select lithium charge profile is going to be available on most modern solar charge controllers and it will be there on all MPPT chargers.
 
May 7, 2016
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I suppose if you want one size fits all settings that's the way to go me I like to be able to tailor things to what I want not what other people think I want.
I am just concerned that some people are being put off Li batteries because they are being portrayed as complex and delicate when they are not.

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