Do I need Lithium?

[matbic]

So just my pennies worth - the main difference between Lithium-Iron-Phosphate and led-acid is efficiency - how much of what you put in you get back.

So an led-acid battery is about 80% efficient when you only charge to 80% of its capacity and after that the efficiency drops to 50%. It’s getting the last 20% “in” that take too long and wastes energy.

A Lithium-Iron-Phosphate battery is very easy to use efficiently it’s about 90% efficient at all states of charge - so getting it full is really easy and quick. The last 20% goes in as quickly as the first.

So coupled with Lithium-Iron-Phosphate protected with a good battery management unit you basically get much more and easy to use power for much less charging time.

It’s ideal when one is off grid a lot. Not so important if always driving or hooked up.

If you let Lithium-Iron-Phosphate regularly drop below 50% charge you will halve its life, so best to keep topping it up with solar and leave on float charge over winter.

 

[headlight]

May I clarify something please.. my 1000w (2000 surge) pure sine wave inverter would not power my espresso coffee machine label says 1100w. I have 2x100amp LA in parallel each 20ah power. If I went with a 100amp lithium, would I have more AH power for my inverter or do I simply need a bigger inverter, or bigger lithium? Trying to understand if lithium actually provides more AH power than LA..... I think you understand what I am likely not asking corectly, to understand...!!

Your 2 x 100AH will power approximately a 400 watt inverter as they are rated at 20AH discharge each. A 100AH lithium will generally be rated at 100AH discharge which will power a 1000 watt inverter.
As your coffee machine is 1100 watts you need an inverter of approximately 1500 watts to give some headroom IMO.
To power a 1500 watt inverter you would need approximately 7 x 100AH lead acids or a lithium with a discharge rate of about 150AH.
So in conclusion you need a bigger inverter and more battery power unfortunately.

 

[headlight]

So just my pennies worth - the main difference between Lithium-Iron-Phosphate and led-acid is efficiency - how much of what you put in you get back.

So an led-acid battery is about 80% efficient when you only charge to 80% of its capacity and after that the efficiency drops to 50%. It’s getting the last 20% “in” that take too long and wastes energy.

A Lithium-Iron-Phosphate battery is very easy to use efficiently it’s about 90% efficient at all states of charge - so getting it full is really easy and quick. The last 20% goes in as quickly as the first.

So coupled with Lithium-Iron-Phosphate protected with a good battery management unit you basically get much more and easy to use power for much less charging time.

It’s ideal when one is off grid a lot. Not so important if always driving or hooked up.

If you let Lithium-Iron-Phosphate regularly drop below 50% charge you will halve its life, so best to keep topping it up with solar and leave on float charge over winter.

Sorry but no.
You do not want to leave a LifePo4 on float over winter as that will shorten its life.
If not being used over winter you want to charge it to 50-80% then turn charging off.
Self discharge on LifePo4 is virtually nothing.
Keeping a battery on float over winter is what you do with lead acids not LifePo4.

 

[Gellyneck]

Are you saying Gels are nearly as good as AGMs?

Wash out your mouth and get your tin helmet on!

 

[SteveandSueJ]

Sorry but no.
You do not want to leave a LifePo4 on float over winter as that will shorten its life.
If not being used over winter you want to charge it to 50-80% then turn charging off.
Self discharge on LifePo4 is virtually nothing.
Keeping a battery on float over winter is what you do with lead acids not LifePo4.

Interesting as instruction manual for my golf trolley lithium battery, says to be left on charge at all times after use... perhaps a different chemistry?

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[Lenny HB]

Are you saying Gels are nearly as good as AGMs?

Go back to sleep boy.

 

[bigtwin]

Interesting as instruction manual for my golf trolley lithium battery, says to be left on charge at all times after use... perhaps a different chemistry?

Undoubtedly.

Ian

 

[68c]

.........If you let Lithium-Iron-Phosphate regularly drop below 50% charge you will halve its life, so best to keep topping it up with solar and leave on float charge over winter.
[/QUOTE]

Sorry, I think you meant to state Lead Acid, not Lithium.

 

[pwilmo]

So a question for Lenny B
Is this true for winter storage ? to charge your lithium battery to 80% and no charge over winter.

Or would my Vanbitz trickle charger for the starter battery - drain the lithium leisure battery.

Or because the leisure lithium is only 80%; would it not maintain the starter battery at all?

Cheers Lenny

 

[headlight]

So a question for Lenny B
Is this true for winter storage ? to charge your lithium battery to 80% and no charge over winter.

Or would my Vanbitz trickle charger for the starter battery - drain the lithium leisure battery.

Or because the leisure lithium is only 80%; would it not maintain the starter battery at all?

Cheers Lenny

If you have discharge on on the battery then yes the Vanbitz Battery Master will slowly drain the leisure battery.
How much and how fast will depend on what parasitic drain is on the starter battery.

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[Lenny HB]

So a question for Lenny B
Is this true for winter storage ? to charge your lithium battery to 80% and no charge over winter.

Or would my Vanbitz trickle charger for the starter battery - drain the lithium leisure battery.

Or because the leisure lithium is only 80%; would it not maintain the starter battery at all?

Cheers Lenny

Normal recommendation is to turn off charging and store between 50 to 80 %.

Starter battery would probably use 10 ah a week depending on alarm tracker etc.
So if you were using a battery maintainer like a BM or Ablemail you wouldn't need to worry about discharging to 80% just fully charge then then turn off charging it would last approx 16 weeks before it was down to 20%.

 

[matbic]

.........If you let Lithium-Iron-Phosphate regularly drop below 50% charge you will halve its life, so best to keep topping it up with solar and leave on float charge over winter.

Sorry, I think you meant to state Lead Acid, not Lithium.
[/QUOTE]

No it’s for Lithium-Iron-Phosphate not picking on Victron it’s just they make it quite clear.

50% Depth Of Discharge gives 5000 cycles to 80% of capacity and 80% DOD gives only 2500 cycles.

 

[headlight]

Sorry, I think you meant to state Lead Acid, not Lithium.

No it’s for Lithium-Iron-Phosphate not picking on Victron it’s just they make it quite clear.

Have a look here …

50% Depth Of Discharge gives 5000 cycles to 80% of capacity and 80% DOD gives only 2500 cycles.
[/QUOTE]

And they say to leave a LifePo4 on permanent float over winter ?
Your link says "site can't be reached".

 

[matbic]

Sorry but no.
You do not want to leave a LifePo4 on float over winter as that will shorten its life.
If not being used over winter you want to charge it to 50-80% then turn charging off.
Self discharge on LifePo4 is virtually nothing.
Keeping a battery on float over winter is what you do with lead acids not LifePo4.

My understanding is that : If you have the float value on your chargers set correctly (much lower than used for lead-acid) all will be fine. The advantage is you guard against some load discharging the battery which is very bad for LifePo4.

This is useful at section 5.5

I guess if the van is completely off during the winter then disconnection is a good and safe option.

But I need to keep the power on as I have frost protection, alarm, tracker etc. which all need some power so correctly set float and it all should be good as well.

I would be interested with your comments.

 

[matbic]

Your link says "site can't be reached".

That’s annoying so I put screen grab in instead - it’s from victron Smart Lithium Battery Manual technical data section.

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[headlight]

My understanding is that : If you have the float value on your chargers set correctly (much lower than used for lead-acid) all will be fine. The advantage is you guard against some load discharging the battery which is very bad for LifePo4.

This is useful at section 5.5

I guess if the van is completely off during the winter then disconnection is a good and safe option.

But I need to keep the power on as I have frost protection, alarm, tracker etc. which all need some power so correctly set float and it all should be good as well.

I would be interested with your comments.

What float voltage have you got.
Why is discharging the battery bad, it's designed to be discharged ?
Or do you mean completely flttening it ?
If you try to over discharge the BMS will step in to protect the battery.

 

[matbic]

What float voltage have you got.
Why is discharging the battery bad, it's designed to be discharged ?
Or do you mean completely flttening it ?
If you try to over discharge the BMS will step in to protect the battery.

So as I understand it: Yes discharge is perfectly OK and a BMS is designed to stop you destroying a battery by completely flattening it - which is a terminal event.

However BMS is not really able to help you with extending life of battery, it’s only there to stop you destroying it. If you want it to last a long time then the depth of discharge is important and lithium batteries work well on a life of shallow discharges with the occasional full charge to allow the BMS to equalise the cells.

This is how I read it anyway! This was useful background.

 

[Carpmart]

I think we are talking about details which are frankly academic. It’s a hangover from the careful management needed with lead chemistry.

For context, I’ve solar charged my lithium 400A batteries with just over a Megawatt of power in the last three years (I’ve also charged with mains and vehicle B2B as well (not included in the Megawatt), we use 140-180A of power most days, yet I’m at 80 odd charge cycles..

So, it’s all academic. If you abuse the cells by charging to 100%, discharging to 20% or less, you’ll be wanting to swap them out for higher density cells way before you wear them out!

 

[LithiumConvert]

So, it’s all academic. If you abuse the cells by charging to 100%, discharging to 20% or less, you’ll be wanting to swap them out for higher density cells way before you wear them out!

Spot on. Sums it all up very nicely!

Although I see no reason to swap them out. Just buy some more to fit alongside.

 

[bigtwin]

I think we are talking about details which are frankly academic. It’s a hangover from the careful management needed with lead chemistry.

Indeed, worst case a cycle life of 2500 is still five times better than a very well cosseted lead acid (and that’s a very rare beasty indeed).

Ian

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[funflair]

Indeed, worst case a cycle life of 2500 is still five times better than a very well cosseted lead acid (and that’s a very rare beasty indeed).

Ian

And 2500 cycles is still a lot of use,

This is our 640ah battery bank and we had the shunt fitted a couple of years ago.

I find 23 charge cycles quite interesting as is nearly 26,000 ah drawn.

 

[TrudeandDall]

Indeed, worst case a cycle life of 2500 is still five times better than a very well cosseted lead acid (and that’s a very rare beasty indeed).

Ian

In fact with that many cycles to use up - my van will be rust and I will be dust long before the cycle mountain is used up

 

[matbic]

I find 23 charge cycles quite interesting as is nearly 26,000 ah drawn.

I am not sure if this is true for all victron gear - but mine counts a cycle when SOC goes bellow 65% then above 90%. So maybe you don’t discharge below 65% so often - your average discharge is -364Ah and 65% of your bank is -416Ah so it’s not counting your average discharge “cycle” as a cycle.

 

[funflair]

I am not sure if this is true for all victron gear - but mine counts a cycle when SOC goes bellow 65% then above 90%. So maybe you don’t discharge below 65% so often - your average discharge is -364Ah and 65% of your bank is -416Ah so it’s not counting your average discharge “cycle” as a cycle.

Interesting I was thinking that a cycle was a charge-discharge on a cumulative basis, I did notice though that total ah of the bank multiplied by the number of cycles was less that the total ah drawn, I thought that this might be due to some draw being taken direct from solar without actually coming from the battery, a bit more reading possibly

Edit, a little bit of Google and I have most likely found the same article as you and indeed it say under 65% to over 90% triggers a cycle count

 

[headlight]

matbic one of the advantages of lithium is that you can discharge below 50%, unlike lead acids without compromising the battery, therfore giving you more usable amps.
The spec for my 230Ah Fogstar LifePo4 states 4,000 cycles at 80% DOD.
A cycle, according to Fogstar, is 100% down to 20% then back to 100%, or any combination of that.
So 100% down to 60%, back to 100%, down to 60% then back to 100% is also 1 cycle.
Fogstar state that after these 4,000 cycles at 80% DOD my 230Ah battery will still have 80% of its original capacity or 184 AH.
The battery has a 10 year warranty.
This battery doesn't need molly coddling.
Fogstar advise not storing the battery at 100% for long periods and in such circumstances they advise storing at 50-80% SOC.
Keeping the battery constantly on float whilst not being used stresses the battery so is also not recommended.
The only thing I do, other than using the battery normally, is that my last night of a trip I turn charging off so when I park up till my next trip my battery is not at 100% SOC and is not kept on float.
I am away at the moment, going home later this morning.
Yesterday evening I turned charge off.
My battery is at 86% so will be at 86% when I park up.
The van will not be used for the next 2 weeks.
During that time my leisure battery will supply a few amps to my starter battery via my Battery Master and a few amps due to my inverter standby drain.
When I next use the van I will turn charge back on and when I arrive at my chosed location my battery will be at 100% SOC again.

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[SteveandSueJ]

matbic one of the advantages of lithium is that you can discharge below 50%, unlike lead acids without compromising the bjattbatterythe spec for my 230Ah Fogstar LifePo4 states 4,000 cycles at 80% DOD.
A cycle, according to Fogstar, is 100% down to 20% then back to 100%, or any combination of that.
So 100% down to 60%, back to 100%, down to 60% then back to 100% is also 1 cycle.
Fogstar state that after these 4,000 cycles at 80% my 230Ah battery will still have 80% of its original capacity or 184 AH.
The battery has a 10 year warranty.
This battery doesn't need molly coddling.
Fogstar advise not storing the battery at 100% for long periods and in such circumstances they advise storing at 50-80% SOC.
Keeping the battery constantly on float whilst not being used stresses the battery so is not recommended.
The only thingi I do, other than using the batter7y

Right so still considering lithium and not had before. How do you keep SOC at 50 to 80% over winter when I need it installed to feed battery master to keep veh LA topped up for Alarm etc? I would be charging on my CBE charger Gel setting so won't reach 100% but does the BMS manage this via phone connection?

 

[Gellyneck]

Wasn't aware it was a competition.
Thought I was gathering information, advice & opinions.
Which I have
So thank you all for your input.

Good L*rd!
Hurry up and spill the beans.
Please, please, please say you went lead acid (or gels) and gave the lithium luvvies a smacking!

 

[headlight]

Right so still considering lithium and not had before. How do you keep SOC at 50 to 80% over winter when I need it installed to feed battery master to keep veh LA topped up for Alarm etc? I would be charging on my CBE charger Gel setting so won't reach 100% but does the BMS manage this via phone connection?

Just turn charge off, via the app, when the battery is around 80 % SOC, it doesnt have to be exact (I turned charge off on mine last night and my battery is at 86% which is close enough), and leave discharge on so your Battery Master will continue to work.
The battery will slowly drain, speed depending on amount of drain.
If it drops to around 50% before you next use it then charge it up a bit.

 

[matbic]

Right so still considering lithium and not had before. How do you keep SOC at 50 to 80% over winter when I need it installed to feed battery master to keep veh LA topped up for Alarm etc? I would be charging on my CBE charger Gel setting so won't reach 100% but does the BMS manage this via phone connection?

Yes exactly so like you I can only keep at 50-80% if you disconnect battery for the winter. Which like you I can’t do as I have stuff that need to be on.

So Victron advice seems far more practical than Frogstar which is: “

1. When leaving the system unattended for some time, make sure to either keep the batteries charged during that time or make sure the batteries are (almost) full and then disconnect the DC system from the battery.”

So this is what I do leave it on charge! The victron BMS/charge system is connected together l, so the battery management controls the charger and I have noticed when leaving my charger on for long periods the battery is not constantly receiving current it is often slightly discharging . This is what should be happening to look after battery with no hassle and I get power on all over winter!

I am a “lithium luvvie” - need to put that on a T-shirt!

 

[headlight]

Yes exactly so like you I can only keep at 50-80% if you disconnect battery for the winter. Which like you I can’t do as I have stuff that need to be on.

So Victron advice seems far more practical than Frogstar which is: “

1. When leaving the system unattended for some time, make sure to either keep the batteries charged during that time or make sure the batteries are (almost) full and then disconnect the DC system from the battery.”

So this is what I do leave it on charge! The victron BMS/charge system is connected together l, so the battery management controls the charger and I have noticed when leaving my charger on for long periods the battery is not constantly receiving current it is often slightly discharging . This is what should be happening to look after battery with no hassle and I get power on all over winter!

I am a “lithium luvvie” - need to put that on a T-shirt!

You don't need to disconnect the battery.
Just turn charge off and leave discharge on so "stuff" that needs to be on is still on.

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