Arising from the small difference in voltage over the charge cycle, I wonder how a solar panel controller is able to manage its output? Also, if floating is undesirable, how does it decide when to stop?
EZA 130 Lithium Power-Pack (1 Viewer)
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DBK
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That's why it pays to buy a good solar controller. The Victron ones have battery management built in and alter the charging voltage accordingly. This is an extract from one of their manuals about the 75/15 model I have:
1.7.1. Bulk During this stage the controller delivers as much charge current as possible to rapidly recharge the batteries.
1.7.2. Absorption When the battery voltage reaches the absorption voltage setting, the controller switches to constant voltage mode. When only shallow discharges occur the absorption time is kept short in order to prevent overcharging of the battery. After a deep discharge the absorption time is automatically increased to make sure that the battery is completely recharged. Additionally, the absorption period is also ended when the charge current decreases to less than 1A.
1.7.3. Float During this stage, float voltage is applied to the battery to maintain a fully charged state. When the battery voltage drops below float voltage during at least 1 minute a new charge cycle will be triggered.
Lenny HB
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To add to that both the Victron & the Votronic Solar regulators are user programmable you can set your own prarameters, bulk charge voltage, absorption time etc.
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Devices intended to operate in vehicle 12v systems have to be tested so that they can stand everything that the vehicle electrics can throw at them. Voltages from 8V (while starter motor cranking) to 32V (over-enthusiastic 24V boost starting), and even 60V for several seconds (battery disconnected while engine running).
Car radios, satnav chargers and in fact anything that has a cigarette lighter plug on it should pass these tests OK.
Other '12V' devices like TVs and LED lights normally have a 12V 'transformer' power brick that plug into the mains. The voltage from that is 11.5 to 12.5V, and that's what the devices are designed to withstand.
If you want to run these things in a vehicle, you need a regulated 12V supply that takes the vehicle supply and controls it to 11.5 to 12.5V.
For other voltages, like USB (5V) and laptops (19V) you don't think twice about using a regulated power supply. But it's an understandable mistake to think you can get away with direct connection when the device input says 12V.
The big difference between charging Pb and Li (can't be bothered type LiFePO4 in anymore) are that a Pb battery requires 3 stages and an Li only requires 2.
Bulk is technically Constant current. you basically set the voltage to a point where the charger is pumping out as much current as it can handle.
Absorption is technically constant voltage. At this point the voltage has reach as high as it is safe to go in CC mode and it will hold at this voltage. As the charge level increases the current will fall.
Float, This is a maintenance voltage only required by Pb batteries.
For an Li battery you only need the 1st two stages. So what I will do is set the float and CV level the same at around the 95% mark. This way the batteries will never over charge. As the batteries voltage rise to the level of the float charge the current will decrease until it reaches zero. Whereas on a Pb battery in float mode there is still a small maintenance current flowing there won't be on an Li battery.
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What I am trying to understand is how a solar panel controller would operate. It will wake up when the sun is right, but then what? I had imagined that it would decide what to do based on the voltage it sees across its output but, if that voltage is not going to vary (much), I’m not sure how it can make the right decision about the type of charging to perform, if any.
A LiFePO4 battery requires no floating charge to maintain its voltage. Not only that, I understand that they are best stored between 50% and 75% charged, so I’m also curious how that will be achieved using solar panels.
A LiFePO4 battery requires no floating charge to maintain its voltage. Not only that, I understand that they are best stored between 50% and 75% charged, so I’m also curious how that will be achieved using solar panels.
As I said above I would program both the float and CV voltage to be around the 95% mark. The solar controller would then no be able to push current into the batteries beyond that charge point/
A LiFePO4 battery requires no floating charge to maintain its voltage. Not only that, I understand that they are best stored between 50% and 75% charged, so I’m also curious how that will be achieved using solar panels.[/QUOTE]
That is quite correct. LiFePO4 batteries prefer being stored at the 60% mark but it is not critical and the reduction in lifespan is not overly reduced from storing at say 90%. The storage issues are mainly to do with maintenance levels I think. At high and low levels of SoC there is little material left for intercalation. This means as I understand it that oxidisation and other bad things can occur. If however you don't have a current source this should not affect things at the 95% level. However leaving them empty for extended periods will cause dendrites to form.
This video is great for understanding the chemistry.
PS: Just had a thought. If you are leaving your van for say 2 months or more. You could change the programming profile so that float/cv voltage is at the 60% mark. Change back to 95% mark a week before you need the van or put it on EHU charger.
I am a fulltimer so my biggest concern will be being on hookup for months at a time...
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Just a quick thought. I may have gotten my figures mixed up in a previous post. I have not been looking at this recently so my memory was a bit rusty..
Here is the charge profile for a Pb vs LiFePO4 battery. (There may be some variation based on chemistry/manufacturer).
As you can (red line). At 10% an Li cell is at 3.35v and at 90% it is about 3.55v.
In a 4s1p battery this means your voltage range would actually be 13.4v to 14.2v.
This is not going to full charge or to empty. Ideally I would like to keep my usage within the the constraints of the knees as once you pass the knee you start in to the area where damage can occur.
Here is the charge profile for a Pb vs LiFePO4 battery. (There may be some variation based on chemistry/manufacturer).
As you can (red line). At 10% an Li cell is at 3.35v and at 90% it is about 3.55v.
In a 4s1p battery this means your voltage range would actually be 13.4v to 14.2v.
This is not going to full charge or to empty. Ideally I would like to keep my usage within the the constraints of the knees as once you pass the knee you start in to the area where damage can occur.
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Thanks for the info, I'll wait for the technology to mature and come down in price. Plus if Samsung can get lithium technology so wrong......... 
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Very succinctly put.Thanks for the info, I'll wait for the technology to mature and come down in price. Plus if Samsung can get lithium technology so wrong.........
I have made no study of the issue on the basis that if Boeing, Yuasa and now it appears Samsung can get it wrong with their huge development budgets, and with an inrush of newly developed technologies soon to enter the market, why would I put my trust in the claims of a comparatively tiny enterprise such as this lot and part with a staggering sum of money in the process?
There will always be people who think differently, and I wish them well with their adventures
Lithium Ion and LifePO4 are completely different.
The reason Lithium Ion can be so volatile, is it reacts badly if exposed to air.
LifePO4 (Lithium Phosphate) doesn't react badly with air.
The Samsung, Boeing, Tesla, etc fires all use Lithium Ion. The better leisure batteries are all Lithium Phosphate.
They are completely different technologies. I wouldn't touch Lithium Ion either.
The reason Lithium Ion can be so volatile, is it reacts badly if exposed to air.
LifePO4 (Lithium Phosphate) doesn't react badly with air.
The Samsung, Boeing, Tesla, etc fires all use Lithium Ion. The better leisure batteries are all Lithium Phosphate.
They are completely different technologies. I wouldn't touch Lithium Ion either.
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No disrespect intended, but I am certainly aware of the differences, as I believe are most reading this thread
Perhaps it is telling you something when organisations such as Boeing still use lithium ion storage cells in their multi million $ passenger carrying aircraft?
There have been a number of major developments announced in cell composition and technology over the past year. This article is one of many: https://www.forbes.com/sites/jamesc...echnologies-keep-getting-better/#4f78e9fb4e62
Until the emerging technologies sort themselves out and prices become sensible, I will keep my hands in my pockets.
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I think the ones used by Boeing and Samsung are Lithium Manganese, probably because they can pack more energy into a smaller battery. I don't think it is the lithium that is the problem anyway, it is the other chemicals used as an electrolyte that misbehave. When it comes to dangerous chemicals I am not a great fan of the Sulphuric Acid used in Lead batteries.
I do agree though that cost is a factor to weigh up.
Interesting article
At a guess, I'd say the reason companies use Lithium Ion is due to the energy density. It's just far more powerful compared to the same size LifePO4 battery.
Thanks for the info, I'll wait for the technology to mature and come down in price. Plus if Samsung can get lithium technology so wrong.........
Go watch the video at #98 from beginning to end.
By the time it's finished, they'll already be down a notch!
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Heartily agree. One of the most interesting threads around.
There are three main chemistries floating around at the moment. They are All Lithium Ions.
Samsungs and Boeings problems were with Lithium Cobalt Batteries I believe.
Lithium Iron Phosphate batteries however are a different beast. They are a bit less energy dense, do NOT explode or flame out when abused..
The other thing worth noting is we are not trying to pack them into a very small area like Samsung did where they suffer from flexing and impacts. And we won't be abusing them with cheap chinese chargers. Boeings issue was a manufacturing defect. The same defect with LiFePO4 would not have the same issue...
You will note in all my posts I use the full chemistry of LiFePO4 to distinguish them from other cells. Please do not mistake them for LiCoO2 or Li2MnO3 cells.
A lot of posts around the net use the Term Lithium polymer (Lipo) which is not really a good description as it doesn't give the chemistry. Lipo is simply the way the electrolyte is constructed.
Saying all Lithium batteries are unsafe is not accurate, as the chemistry, construction and safety vary massively.
Samsungs and Boeings problems were with Lithium Cobalt Batteries I believe.
Lithium Iron Phosphate batteries however are a different beast. They are a bit less energy dense, do NOT explode or flame out when abused..
The other thing worth noting is we are not trying to pack them into a very small area like Samsung did where they suffer from flexing and impacts. And we won't be abusing them with cheap chinese chargers. Boeings issue was a manufacturing defect. The same defect with LiFePO4 would not have the same issue...
You will note in all my posts I use the full chemistry of LiFePO4 to distinguish them from other cells. Please do not mistake them for LiCoO2 or Li2MnO3 cells.
A lot of posts around the net use the Term Lithium polymer (Lipo) which is not really a good description as it doesn't give the chemistry. Lipo is simply the way the electrolyte is constructed.
Saying all Lithium batteries are unsafe is not accurate, as the chemistry, construction and safety vary massively.
I just recalled watching a video of serious LiFePO4 cell abuse. The cell was overcharged then put under a complete dead short.
This cannot happen in a well installed system as you would have a fuse on the positive terminal that would break the circuit.
However, it shows the failure mode of the cell. At 10 minutes it starts gassing, at 13 minutes it goes pop. Lots of smoke and a bang. But no flames.
Smoke stinks badly. However this is the same as what happens to a lead acid battery. Except there is no visible smoke. Just a nasty rotten egg smell and lots of hydrogen released which can explode.
the only time I have seen flames from a LiFePO4 was from an overcharged cell which was then shot 10+ times with a handgun.
I wouldn't put LiCoO2 cells in my van, but I am happy with LiFePO4 cells.
This cannot happen in a well installed system as you would have a fuse on the positive terminal that would break the circuit.
However, it shows the failure mode of the cell. At 10 minutes it starts gassing, at 13 minutes it goes pop. Lots of smoke and a bang. But no flames.
Smoke stinks badly. However this is the same as what happens to a lead acid battery. Except there is no visible smoke. Just a nasty rotten egg smell and lots of hydrogen released which can explode.
the only time I have seen flames from a LiFePO4 was from an overcharged cell which was then shot 10+ times with a handgun.
I wouldn't put LiCoO2 cells in my van, but I am happy with LiFePO4 cells.
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Excellent and informative posts, Gromett, as I have come to expect of you. Many thanks
For myself, I have a tendency to be an early adopter of most things, as my stack of now redundant iPhones will testify (not any more since I have finally - and happily -embraced Android), not too mention my long abandoned stack of shoddily made Dyson products (another story entirely), expensive "sous vide" cooking items used once, my fancy robot vacuum cleaner and many other shiny and attractive mistakes that fill my loft and whose destiny is set for landfill when I get round to chucking them out. It has taken literally decades to evolve to the stage where I can now say "if I don't need it, I won't buy it, and if I don't use it for 12 months, just bin it"
My reservations about safety which you have addressed very well are frankly minimal, albeit that if manufacturing defects can get past both Yuasa and Boeing, I have to wonder why I should have any particular confidence in what appears to me to be a French start up. To be truthful such concerns are secondary to the likelihood that the technology employed will be superseded very soon and thus prove any investment now to be yet another costly exercise with only limited if any real benefit to myself.
This is not to say that anyone is wrong to try anything new, I was reluctant to try one of those mini jump start packs, yet when used properly I have to admit they are actually brilliant. But ÂŁ60 as a different kettle of fish altogether from the ÂŁ3,000 mentioned in this thread. Perhaps I am diplomatically trying not to be critical of the OP's decision, whilst appreciating his comprehensive review?
@pyro I have no problems at all with the French system.. They provide a drop in replacement for Lead Acid batteries with many added features. They are pretty unique in the market and as such can command a price premium. For those with the spare cash it isn't a bad option.
However for those of us with a small amount of technical knowledge and a lesser budget... The technology is now available so we can put our own hotchpotch system together which can be just as safe and probably more versatile..
Currently I wouldn't recommend anyone with no technical knowledge to have a go themselves as there are too many variables and still a lot of debate on best practices with respect to LiFePO4 usage in motorhomes. You really do need to go into this with your eyes wide open and with a view that this isn't currently a totally hands off technology if you want the best out of it.
That all said. You could get 4 winston cells. wire them in series and treat them as a lead acid battery. You would get a longer lifespan out of them than a Pb battery and it would reduce your weight.
If you look at the technical specs.
Nominal voltage of the cell is 3,2 V and the operational voltage is 2,8 V - 3,8 V.
The maximum charging voltage for initial charge is 4 V.
Recommended subsequent charging is to 3.8 V.
The minimum voltage is 2.5 V.
Maximum discharge current is 3C continously.
Operating temperature -45°C up to 85°C (discharging)
As you can see the recommended max charge (after initial charge) is 3.8v per cell. For a 4s1p battery this would equate to 15.2V which is well above what standard Pb chargers put out. So you could in theory just treat them as a normal lead acid battery. The downside to doing this is that if the float charge is above 12.8v then you will be floating each cell at above it's 3.2v nominal voltage and will reduce it's lifespan. Without balancing you are likely to eventually kill the weakest cell much quicker than if it was looked after. However.. It should still in practice last longer than a lead acid and give you a significant weight reduction and therefore increased payload. The problem is that because of the reduced lifespan you probably won't get the financial benefits that normally comes from having the 2,000 cycle lifespan so it would probably end up not being as cost effective.
However for those of us with a small amount of technical knowledge and a lesser budget... The technology is now available so we can put our own hotchpotch system together which can be just as safe and probably more versatile..
Currently I wouldn't recommend anyone with no technical knowledge to have a go themselves as there are too many variables and still a lot of debate on best practices with respect to LiFePO4 usage in motorhomes. You really do need to go into this with your eyes wide open and with a view that this isn't currently a totally hands off technology if you want the best out of it.
That all said. You could get 4 winston cells. wire them in series and treat them as a lead acid battery. You would get a longer lifespan out of them than a Pb battery and it would reduce your weight.
If you look at the technical specs.
Nominal voltage of the cell is 3,2 V and the operational voltage is 2,8 V - 3,8 V.
The maximum charging voltage for initial charge is 4 V.
Recommended subsequent charging is to 3.8 V.
The minimum voltage is 2.5 V.
Maximum discharge current is 3C continously.
Operating temperature -45°C up to 85°C (discharging)
As you can see the recommended max charge (after initial charge) is 3.8v per cell. For a 4s1p battery this would equate to 15.2V which is well above what standard Pb chargers put out. So you could in theory just treat them as a normal lead acid battery. The downside to doing this is that if the float charge is above 12.8v then you will be floating each cell at above it's 3.2v nominal voltage and will reduce it's lifespan. Without balancing you are likely to eventually kill the weakest cell much quicker than if it was looked after. However.. It should still in practice last longer than a lead acid and give you a significant weight reduction and therefore increased payload. The problem is that because of the reduced lifespan you probably won't get the financial benefits that normally comes from having the 2,000 cycle lifespan so it would probably end up not being as cost effective.
dabhand
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This may/may not be of any interest to anyone at the moment but Jon Wagner who up until recently was the battery technology director and head of battery engineering at Tesla has left the company to start his own battery and drivetrain set up in Redwood California.
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I think I was mixing up manganese and cobalt in my last post.
I notice that the same supplier does a ready made 12v 90ah comprising 4 Winston cells but it does not include cell balancing. However, they built each one from matched cells and those of us that had time to sit through the whole video lecture might recall that the lecturer said this was a good alternative if, as he suspected, cell balancing might often be omitted for cost reasons.
I notice that the same supplier does a ready made 12v 90ah comprising 4 Winston cells but it does not include cell balancing. However, they built each one from matched cells and those of us that had time to sit through the whole video lecture might recall that the lecturer said this was a good alternative if, as he suspected, cell balancing might often be omitted for cost reasons.
Yes that is correct. I will be bottom balancing my cells and skipping the BMS which does top balancing. If you bottom balance you avoid the chance of one cell going below it's minimum voltage. Then if you charge up to a level below the maximum for the battery you almost completely remove the risk of overcharging individual cells. You do lose some capacity but in return you get a much longer lifespan out them. This is the reason I don't like most BMS as when they do a top balance they push charge in until one cell reaches max voltage, they then put a small resistor across this cell to discharge it a bit. Once this cell has dropped .1V they resume full charging. The repeat this until all cells are at the same voltage and at maximum charge voltage.
This ensure all cells are balanced at the top and full capacity is achieved. However I feel this micro cycling at the top of the charge voltage range reduces lifespan in order to achieve this slightly higher maximum capacity. I personally want to maximise lifespan at the cost of a few AH to give me the best value out of the battery over time
If anyone is interested this link will show you how Relion build their LiFePO4 batteries.
https://www.solacity.com/docs/RELiON/RELiON_Cell_Features_and_Design.pdf
You will perhaps be reassured to read that if a bullet should penetrate a cell, the battery will continue to function but at a lower capacity. If someone shoots at me concern about the workings of my leisure battery might take second place to concentrating on bowel control.
https://www.solacity.com/docs/RELiON/RELiON_Cell_Features_and_Design.pdf
You will perhaps be reassured to read that if a bullet should penetrate a cell, the battery will continue to function but at a lower capacity. If someone shoots at me concern about the workings of my leisure battery might take second place to concentrating on bowel control.
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skylinersi
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who said motorhoming can be dull..............
@Gromett There is some interesting info here
http://www.technomadia.com/2015/02/living-the-lithium-lifestyle-3-5-year-lithium-rv-battery-update/
These guys fitted Lithium to their RV 4 years ago and posted a review of the performance. It has some good advice on building a battery pack and setting the charging parameters and to maintain performance. Seems they had issues with temperature causing ageing of their pack.
http://www.technomadia.com/2015/02/living-the-lithium-lifestyle-3-5-year-lithium-rv-battery-update/
These guys fitted Lithium to their RV 4 years ago and posted a review of the performance. It has some good advice on building a battery pack and setting the charging parameters and to maintain performance. Seems they had issues with temperature causing ageing of their pack.
I followed that at the time. It was an interesting project and part of what started me looking at it. However back then the cost was extortionate for my needs. Thanks though
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