Don't charge your lithium batteries 100%

[peterc10]

See Peter if you had a victron MPPT you could have used the same preset with that.

But then I wouldn't be able to get my fridge and freezer to automatically run on 12v, instead of gas, when the batteries are full. And to monitor that state every half hour. Very useful in the summer. In reality it is simple to just isolate the solar when in storage mode and leave it all to the IP22, now that I know how to do that. My calculations suggest that the cost of electricity will be about £1 per month, which I can cope with knowing that my very expensive lithiums will be even better protected.

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.

If that was aimed at me, it is not what I have done. All leisure battery chargers were added (B2B) or changed (solar and mains) so that they all have dedicated LiFePo4 profiles. My question was just about getting them to stop at 80% charge when in storage mode. So no "dumb" chargers, just one dumb user (me).

 

[Lenny HB]

But then I wouldn't be able to get my fridge and freezer to automatically run on 12v, instead of gas, when the batteries are full. And to monitor that state every half hour.

It can be done, I'm going to fit a Victron on the next van. I've worked out that if I fit a BMV 712 I can use the relay in that to switch 12v to the S+ line when the batteries are at say 90% & turn off when down to 50%, then fit a 12v 7 day timer inline that will allow the S+ feed to be switched on & off in blocks throughout the day during the hours of sunlight.

 

[Hoovie]

people should do the maths ....

Ok, instead of using a 100Ah Lithim fully, you charge to 80% and you never discharge below 20% in order to "save the battery"
so straight away you are only using 60% of the quoted battery capacity. What happens then to the shouts of "Get lithium, you get twice as much power for the same capacity!"? Well, that goes out the window to start with.

Next ... yes you may get more charge cycles out a Lithium battery by doing this, but by extending the battery life it is also costing you more up-front as you need to buy more batteries to get the USEABLE capacity you are after (and why maybe you changed to Lithium in the first place?)

And Next after Next ... say you get 5,000 cycles if you 'abuse' the battery by fully charging and then using till empty. 100Ah battery = 500,000 Ahs of energy taken out. If you doubled the life of the battery (10,000 cycles say) by going between 80% and 20%, you are getting 60Ahs of energy for 10,000 cycles, which equals 600,000Ahs over the battery life.
So what have you done? you may have theoretically doubled the service life of the battery but you have only gained 20% of energy in total.
And that service life? yes the LiFePO4 cells may be still good, but what about the cheap electronics in the BMS (let's not kid ourselves they are anything but built as cheaply as possible) - will they last 20 years? will they even last 10 years? And when you have good cells but cannot access them due to a failed BMS, what use is that? You can't open the battery to replace the BMS in most cases. and if you could, how many people WOULD? Some yes, but in the minority for sure.
And who needs or wants a battery that will outlive them? I don't.


I charge my Lithiums to 100%.
I typically drain to around 10-15% and that is a happenstance of my Hybrid Lithium/Lead System. I would not be overly worried about draining to 0% in terms of battery longevity, but would more so for the inconvenience of not having any battery power left.

 

[peterc10]

It can be done, I'm going to fit a Victron on the next van. I've worked out that if I fit a BMV 712 I can use the relay in that to switch 12v to the S+ line when the batteries are at say 90% & turn off when down to 50%, then fit a 12v 7 day timer inline that will allow the S+ feed to be switched on & off in blocks throughout the day during the hours of sunlight.

Lenny HB Knowing me, what do you think the odds are that I even understood that, let alone being able to do it??????

 

[AdrianChen]

It can be done, I'm going to fit a Victron on the next van. I've worked out that if I fit a BMV 712 I can use the relay in that to switch 12v to the S+ line when the batteries are at say 90% & turn off when down to 50%, then fit a 12v 7 day timer inline that will allow the S+ feed to be switched on & off in blocks throughout the day during the hours of sunlight.

I was going to look at the load output on our Victron MPPT to see if I could get a similar result, timer is a good idea - haven't actually made any progress so far - too cold.

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[Two on Tour]

Lenny HB Knowing me, what do you think the odds are that I even understood that, let alone being able to do it??????

I'm sure you can sort that out Peter, after all, you are married so I know that you can take and work under instructions.

 

[Minxy]

Ok, instead of using a 100Ah Lithim fully, you charge to 80% and you never discharge below 20% in order to "save the battery"
so straight away you are only using 60% of the quoted battery capacity. What happens then to the shouts of "Get lithium, you get twice as much power for the same capacity!"? Well, that goes out the window to start with.

I agree. We have gels so can go down to 30% thus can use 70%, I would only gain 10% extra so it would be a lot of dosh just for that and I don't need to be overly concerned about keeping them happy

If space/weight was an issue then lithium may be the way to go but I think a lot of people are jumping on the lithium bandwagon as the answer to their prayers without thinking it through... It seems to be the latest 'must have' ie keeping up with the Jones', rather than from a real need perspective for some, just as having a Honda genny was in the past to provide extra power.

 

[Ditcha]

I agree. We have gels so can go down to 30% thus can use 70%, I would only gain 10% extra so it would be a lot of dosh just for that and I don't need to be overly concerned about keeping them happy

If space/weight was an issue then lithium may be the way to go but I think a lot of people are jumping on the lithium bandwagon as the answer to their prayers without thinking it through... It seems to be the latest 'must have' ie keeping up with the Jones', rather than from a real need perspective for some, just as having a Honda genny was in the past to provide extra power.

I can remember when "gels" were the latest must haves it was a few years back

 

[Hoovie]

I was going to look at the load output on our Victron MPPT to see if I could get a similar result, timer is a good idea - haven't actually made any progress so far - too cold.

Just a note on that ...
If you have a compressor fridge, do NOT use the load output on the MPPT to connect to it. The compressor surge will shut down the output circuit as it is above the rated 20A (max) output.

I used the BMV Relay along with SSR (240V Relay with 12V control line) to send power from the Inverter to the 3-way fridge (when I had one) and the Electric element in the Water Heater, depending on the battery SOC. Works very well and is a good use of excess Solar.

 

[peterc10]

Nope. I am only doing this when the motorhome is not going to be used for long periods. When in regular use it will be being charged fully by whatever charger(s) that are in use.

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[Lenny HB]

Lenny HB Knowing me, what do you think the odds are that I even understood that, let alone being able to do it??????

Now Peter you even proved yourself wrong you managed to fit your own Lithium and you did a good job of it.
You would be able to do it with a bit of coaching from us but you wouldn't like the price as not only the cost of the controller you would have to replace your BMV700 with a BMV712.

 

[Hoovie]

I agree. We have gels so can go down to 30% thus can use 70%, I would only gain 10% extra so it would be a lot of dosh just for that and I don't need to be overly concerned about keeping them happy

If space/weight was an issue then lithium may be the way to go but I think a lot of people are jumping on the lithium bandwagon as the answer to their prayers without thinking it through... It seems to be the latest 'must have' ie keeping up with the Jones', rather than from a real need perspective for some, just as having a Honda genny was in the past to provide extra power.

If payload is not an issue (and I know it is a genuine one for some), then the only real tangible benefit in the here and now (as opposed to what will be in ten years) is the speed and efficency of recharge.
THAT truely is a significant advantage. But even then, how much of a advantage still depends on the user - if they plug in to EHU for say 10 hours, having the battery pack recharged in 2 hours instead of 8 makes no difference.

Horses for course. The "Go Lithium" cry is no more valid than the "Go Auto Gearbox" or "Go Avtex telly" ones

 

[Two on Tour]

Now Peter you even proved yourself wrong you managed to fit your own Lithium and you did a good job of it.
You would be able to do it with a bit of coaching from us but you wouldn't like the price as not only the cost of the controller you would have to replace your BMV700 with a BMV712.

Both the BMV700 and the BMV712 have a relay Lenny.

 

[Ditcha]

Now Peter you even proved yourself wrong you managed to fit your own Lithium and you did a good job of it.
You would be able to do it with a bit of coaching from us but you wouldn't like the price as not only the cost of the controller you would have to replace your BMV700 with a BMV712.

He did have more hair tho Lenny before starting the upgrade

 

[Lenny HB]

I agree. We have gels so can go down to 30% thus can use 70%, I would only gain 10% extra so it would be a lot of dosh just for that and I don't need to be overly concerned about keeping them happy

If space/weight was an issue then lithium may be the way to go but I think a lot of people are jumping on the lithium bandwagon as the answer to their prayers without thinking it through... It seems to be the latest 'must have' ie keeping up with the Jones', rather than from a real need perspective for some, just as having a Honda genny was in the past to provide extra power.

It depends on how you want to use your van, with the new van I took the decision not to have an oven (didn't like where or how it was fitted) and to fit a decent amount of Lithium and use electric for most things obviously not the heating but that's gas only anyway.

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[AdrianChen]

Just a note on that ...
If you have a compressor fridge, do NOT use the load output on the MPPT to connect to it. The compressor surge will shut down the output circuit as it is above the rated 20A (max) output.

I used the BMV Relay along with SSR (240V Relay with 12V control line) to send power from the Inverter to the 3-way fridge (when I had one) and the Electric element in the Water Heater, depending on the battery SOC. Works very well and is a good use of excess Solar.

Thanks for that - we have an AES fridge, and the idea was just to use the load output to trigger the AES thing on the fridge, not to try and power it directly - pretty sure I wont have enough solar for that. - I can also use the inverter (manually at the moment) so not sure which way to go, or if it's even worth the hassle!

 

[steve69]

This whole thread just scrambles my brain.
I never use my electric bike during the winter. The Li battery is charge to 100% and left in storage for a few months.
I did this believing it was the right thing to do.
If this is wrong, what level of charge should a bike Li battery be left at to preserve it's life?
I want to preserve it's life as they are currently near £500 a pop!

 

[Minxy]

If payload is not an issue (and I know it is a genuine one for some), then the only real tangible benefit in the here and now (as opposed to what will be in ten years) is the speed and efficency of recharge.
THAT truely is a significant advantage. But even then, how much of a advantage still depends on the user - if they plug in to EHU for say 10 hours, having the battery pack recharged in 2 hours instead of 8 makes no difference.

Horses for course. The "Go Lithium" cry is no more valid than the "Go Auto Gearbox" or "Go Avtex telly" ones

We only ever have ehu at home when we ensure the batteries are fully charged before setting off so can leave it on for a while thus no need for quick charging. When away we never have ehu, just solar, so don't think it would make any difference to us.

 

[Minxy]

I can remember when "gels" were the latest must haves it was a few years back

... I think Lenny has shares in them!

Ours came with gels so quite happy with them.

 

[Jim]

The Li battery is charge to 100% and left in storage for a few months.
I did this believing it was the right thing to do.
If this is wrong, what level of charge should a bike Li battery be left at to preserve it's life?
I want to preserve it's life as they are currently near £500 a pop!

Your bike battery is probably not LiFePO4

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[Minxy]

This whole thread just scrambles my brain.
I never use my electric bike during the winter. The Li battery is charge to 100% and left in storage for a few months.
I did this believing it was the right thing to do.
If this is wrong, what level of charge should a bike Li battery be left at to preserve it's life?
I want to preserve it's life as they are currently near £500 a pop!

Probably LiOn not Po.

 

[steve69]

Your bike battery is probably not LiFePO4

Probably LiOn not Po.

I think my brain just melted.

 

[Minxy]

I think my brain just melted.

 

[steve69]

Loved that!. I remember it was a hit in 1973. The Goons.....legends.

 

[Kannon Fodda]

This whole thread just scrambles my brain.
I never use my electric bike during the winter. The Li battery is charge to 100% and left in storage for a few months.
I did this believing it was the right thing to do.
If this is wrong, what level of charge should a bike Li battery be left at to preserve it's life?
I want to preserve it's life as they are currently near £500 a pop!

Bosch suggest their batteries should be stored at 60% to 80% charge. As with motorhome Lithium I've never worried and they tend to have been stored fully charged as once I've ridden the bike, I charge ready for next time, whenever that might be, and that can be a few months as cold and cycling doesn't seem like fun.

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[autorouter]

This whole thread just scrambles my brain.
I never use my electric bike during the winter. The Li battery is charge to 100% and left in storage for a few months.
I did this believing it was the right thing to do.
If this is wrong, what level of charge should a bike Li battery be left at to preserve it's life?
I want to preserve it's life as they are currently near £500 a pop!

Just less than 100% is OK. Charge to 100% then take a bit out. If you buy a new battery you'll probably find it's at about 60%, that's how they store them for long storage life.

Lead-acids deteriorate if they are below 100% for a few weeks, so people like to keep them at 100% all the time, that's what 'float charging' is. But not necessary for lithiums, they can stay partly charged for ages with no deterioration. This is true for all kinds of lithium batteries, not just LiFePO4 ones.

 

[Pausim]

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.

A “dumb” single stage charger probably damages lead acid batteries more than LiFePO4. It is lead acid ones that need bulk, absorption and maintenance phases. I had a basic single stage 13.8V charger on one of my motorhomes and it was a lead acid destroyer. That same charger might undercharge LiFePO4 but it’s is not going to harm it either. I have no problems using my CBE mains charger set to lead acid, it charges at 14.3V and then drops back to a 13.6V maintenance charge. After a while my LiFePO4 settles back to a comfortable 90%. I don’t need a full battery when on EHU, I need a full battery when I am not.

 

[bigtwin]

The simple way of achieving the goal of storing at 80%, or less, is to not fully charge the battery prior to storage and then use the BMS to isolate the charge input but perhaps not all batteries have this function.

Ian

 

[cyberyacht]

I've got my CBE charger set to 'Gel', not that it gets used much, just the odd occasion I'm on hookup which mostly when cooling the fridge before departure. I just leave the solar panels and the MPPT to do its stuff. The battery BMS seems to decide when it's had enough to eat anyway.

 

[Pausim]

The simple way of achieving the goal of storing at 80%, or less, is to not fully charge the battery prior to storage and then use the BMS to isolate the charge input but perhaps not all batteries have this function.

Ian

How many makes of LiFePO4 have a BMS with this facility? Not many I suspect, my Relion doesn’t. Perhaps those with these remote control BMSs could say which makes have them.

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