CAB96
LIFE MEMBER
Lithium? The big con?
- Thread starter haganap
- Start date
There's me thinking a motorhome was for pleasure, after reading these posts I obviously need to enroll in an electronics degree coarse to understand all this technical stuff plus an encyclopedia for all the "jargon" and abbreviations
- Jul 29, 2024
- 225
- 670
- Funster No
- 105,029
- MH
- Imminent Purchase!
It’s very simple if the units and terminology is correct.
A battery holds electricity at a fixed voltage, usually around 12v in the case of truck and leisure batteries.
It has a known amount of electricity inside it so can deliver this to a load.
The rate of flow is Amps. Two amps for two hours is four amp hours, and so on.
A lead based battery can usefully deliver half its rated capacity, such as 100 amp hours, so fifty.
That can be an amp for fifty hours or five amps for ten hours.
A lithium maybe eighty percent.
There are number factors that complicate the situation but if you get this so far you are going to understand it well.
Tony
A battery holds electricity at a fixed voltage, usually around 12v in the case of truck and leisure batteries.
It has a known amount of electricity inside it so can deliver this to a load.
The rate of flow is Amps. Two amps for two hours is four amp hours, and so on.
A lead based battery can usefully deliver half its rated capacity, such as 100 amp hours, so fifty.
That can be an amp for fifty hours or five amps for ten hours.
A lithium maybe eighty percent.
There are number factors that complicate the situation but if you get this so far you are going to understand it well.
Tony
Getting battery power envy here.
If you were to replace a conventional system from scratch what would be the best route forward based on not having an air fryer, hairdryer and still would want to use the fridge and hob on gas. Or are these 12 pages all about testosterone?
If you were to replace a conventional system from scratch what would be the best route forward based on not having an air fryer, hairdryer and still would want to use the fridge and hob on gas. Or are these 12 pages all about testosterone?
Subscribers do not see these advertisements
Exactly…….
80AH lead acid leisure battery and simple split charge.
If you want to run anything power hungry plug into EHU.
Simples lol.
The best route for me would be to talk to an expert, but you do need an idea of what you'll use, then double it.
Like batteries, and amps/AH/watts Testosterone does eventually run out I think. I hope so because my ears are getting bigger, and I don't have much hair left.....
- Feb 5, 2024
- 514
- 812
- Funster No
- 101,061
- MH
- Etrusco CV540 DB
- Exp
- On and off for about 30 years
I know it has been asked before but please quote power consumption in Ah (Amp hours) not Amps, to avoid confusion. Your numbers are correct because you obviously understand how this works, but not everyone does.
As a less obvious example, running
an air fryer via an inverter might take 120 Amps of current measured at the 12V battery, and run for 15 mins. The total amount of energy taken out of the battery in this case is 120 Amps × 0.25 hrs = 30 Ah.
The other misleading thing is when battery or power bank capacities are quoted in Wh, (Watt hours). This gives an impressively large number but this is just because Watts = Volts x Amps, so a 12V battery with a capacity of 100 Ah could also be expressed as 1200 Wh.
3 simple steps:
1. Establish all your total loads for one day: add all your loads and multiply by time used each load separately, and add them up. as ex: 50Ah
2. Ensure your replenishing means (recharging), can put back all of your daily consumption back in, within that day, (plan for worst case scenario), if you operate in winter, factor in contingency plans to cover it.
Recharging capacity as ex. 50Ah.
3. Storage 150Ah Li and 300Ah for Pb =minimum 3x your daily consumption so you only end up 1/3 discharged IF recharging fails within that day.
More storage if economically viable will sustain the system through unforeseen external factors ( bad weather, winter etc).
Or more storage if you have large peak loads to sustain, this will have to be taken in consideration to.
Guess what? Non many follow this simple rules and end up crying, hope for the best, or learn to manage the limitations of what they got.
Subscribers do not see these advertisements
We put a 280Ah Fogstar, 170w victron panel, 500w inverter + 30A b2b in the van a couple of years ago for less than £1500 and it WAS a game changer. We've just had 4 nights away in Northumberland and used less than 50% of available charge. That's with a diesel heater on about 60% of the time, mobile broadband, TV, 2 laptops + mobiles and tablets etc. Cooking, fridge and hot water are all on gas. Yes it would be nice to run a kettle, air fryer and microwave off the battery but it's definitely not necessary. In the summer we do go weeks without EHU and the freedom is fantastic.
What the OP needs is a Mr Fusion reactor. Last I heard was you get a minimum of 1.21Gw output just using banana skins and other rubbish. Get in touch with Doc Brown - Hill Valley for the details. Failing that if you use Metcheck to forecast a nearby storm you could always wire the batteries up to a local clocktower and juice them up from a lightning strike!
What the OP needs is a Mr Fusion reactor. Last I heard was you get a minimum of 1.21Gw output just using banana skins and other rubbish. Get in touch with Doc Brown - Hill Valley for the details. Failing that if you use Metcheck to forecast a nearby storm you could always wire the batteries up to a local clocktower and juice them up from a lightning strike!
Perhaps to satisfy all electrical (and propulsion) needs, maybe consider this technology?
Also stealthy silent, so no “noisy” generators to annoy anyone in the next county, whilst off grid wild camping!!!!
Ps. Slightly better range than your EVs too….
Also stealthy silent, so no “noisy” generators to annoy anyone in the next county, whilst off grid wild camping!!!!
Ps. Slightly better range than your EVs too….
OP
OP
haganap
LIFE MEMBER
- Dec 5, 2007
- 13,029
- 28,385
- Funster No
- 974
- MH
- Niesman+Bischoff 79e
- Exp
- I'm an oldbie MH number 10
Tony, please no...
Difficult enough as it is.
No, Minxy husband and above.... my fridge is on gas 100 percent, and it's lovely and cold.
Tude, you need to read the threads about my wife's hair and cooking to understand that...
Lenny HB I have no visible shunt setting. (That i can see)
But I've now arrived home to the joy of electric hook up so will see if that sorts it out...
The thrill of a long hot shower
awaits... whilst watching nikki dry her hair and use the microwave and air fryer at the same time...I've learnt a lot from this thread in its jest... I've also learnt some people take things way way to seriously.
Just going to mark myself safe from lithium anxiety on Facebook, search for a towable 7kva genny..
But don't worry folks, my next 7 long weekends and skiing holiday is all on EHU ...
Then summer kicks in and we'll be back to normal...
Your "Min battery voltage" is way too low.
- Sep 7, 2017
- 1,517
- 6,175
- Funster No
- 50,394
You really need to discuss what your needs actually are, how long off grid, what you power usage is with people who are able to specify a solution. There are some on here who can do it or speak with a specialist installer.
Subscribers do not see these advertisements
- Sep 22, 2023
- 699
- 652
- Funster No
- 98,988
- MH
- 4 berth coachbuilt
But, absolutely essential that we do - if we want to understand what is going on.
Well thanks for starting an interesting thread on a rainy day when I have a cold and can't be bothered to walk the dog, it was entertaining, more so than daytime tv.....Tony, please no...
Difficult enough as it is.
No, Minxy husband and above.... my fridge is on gas 100 percent, and it's lovely and cold.
Tude, you need to read the threads about my wife's hair and cooking to understand that...
Lenny HB I have no visible shunt setting. (That i can see)
But I've now arrived home to the joy of electric hook up so will see if that sorts it out...
The thrill of a long hot shower
I've learnt a lot from this thread in its jest... I've also learnt some people take things way way to seriously.
Just going to mark myself safe from lithium anxiety on Facebook, search for a towable 7kva genny..
But don't worry folks, my next 7 long weekends and skiing holiday is all on EHU ...
Then summer kicks in and we'll be back to normal...
Enjoy the EHU on your next trip - is your cable your old one, or an inferior one supplied with the new van?
- Sep 7, 2017
- 1,517
- 6,175
- Funster No
- 50,394
I'll be very interested to hear about the skiing, where you go, how you get on travelling there, life on camp site etc.Tony, please no...
Difficult enough as it is.
No, Minxy husband and above.... my fridge is on gas 100 percent, and it's lovely and cold.
Tude, you need to read the threads about my wife's hair and cooking to understand that...
Lenny HB I have no visible shunt setting. (That i can see)
But I've now arrived home to the joy of electric hook up so will see if that sorts it out...
The thrill of a long hot shower
I've learnt a lot from this thread in its jest... I've also learnt some people take things way way to seriously.
Just going to mark myself safe from lithium anxiety on Facebook, search for a towable 7kva genny..
But don't worry folks, my next 7 long weekends and skiing holiday is all on EHU ...
Then summer kicks in and we'll be back to normal...
We are flying this year and have rented a place in Bourg, but have considered the campsite as an alternative, obviously staying longer.
Lenny HB
LIFE MEMBER
- Oct 18, 2007
- 58,777
- 183,046
- Funster No
- 658
- MH
- Carthago Compactline
- Exp
- Since 2008 & many years tugging
Click on setting cog top right then click on battery.
Subscribers do not see these advertisements
It's not easy to get people to understand what they don't know. But it's almost impossible to get people to change their mindset if they know for a fact something is true, but actually it isn't. You can only state what is correct, and hope other people reading the thread get the correct version not the incorrect version. You'll never win the amps/amp-hours argument.
Now that you have clarified the fridge is on gas...
I have questions about this image. I saw the -59.3Ah and just assumed you lost this during your night out.
But you state it went from 27% to 81% SOC while you were out for the evening if I am not misreading this? So it appears as though you gained stage of charge (SOC) whilst you were out.
But looking at the voltage vs the SOC, something seems off.
Here is an example SOC chart.
As you can see. from around 17% to around 90% the voltage changes very little. Your voltage reading of 12.64 means each of the 4 cells is at 3.16V which is around 15-16% according to this table.
So your shunt is reporting the voltage for 15% but showing the SOC as being at 81%. If it was at 81% then the voltage would be 3.3V per cell or 13.2V for the battery.
My suspicion is the Coulomb counter (SOC level) is out of sync with where the battery actually is at.
So you think you are 81% but are actually sub 20%. You are therefore running out of power well before you expect to? Basically only running the battery in the lowest 20 odd % of it's capacity?
My thoughts are. A couple of things to look at?
My first steps would be to go through a full charge cycle. Leaving it on mains charger for at least 12 hours.
If this doesn't get things back to normal.
Check the settings of the BMS to ensure someone hasn't been fiddling with the charge cutoff voltage. If they have lowered this under the misapprehension that it will extend the lifespan of the battery it may not allow the battery to get to a full charge and reset the coulomb counter (SOC level). If they are not synced periodically they will drift and cause issues like this.
Finally if the BMS on each battery are all the same and at a suitable level. It may be a duff cell in one battery. I would disconnect all three batteries completely so you can see naked terminals. Leave it for an hour or two then measure the voltage.
They should all match within very close tolerances. You may be able to detect this if you have access to each batteries software and can see the individual cell voltages. But some suppliers password protect the advanced stuff to protect from warranty claims caused by poor configuration.
My thought here is if one cell in one battery is damaged. Then it may pull that battery down, and once off charge the other 2 batteries will discharge into the bad one. I have had this happen on a lead acid bank.
These are just a few ideas. There are probably other steps you can take.
Last edited:
PS: This is the article I go the chart from and it seems pretty representative.
www.bravabatteries.com
LiFePO4 Battery Discharge and charge Curve
12V LiFePO4 Battery Pack Characteristic Curve 1. Discharge Curve at Different Discharge Rate Different Rate Discharge Curve @ 25 0C 2. Different Curve at Different Temperature Different Temperature Discharge Curve @ 1C 3. State of Charge Curve State of Charge Curve @ 1C 25 0C 4. Cycle Life Curve...
www.bravabatteries.com
I replied to this in post 305.
The scenario to drop a cell its not the case, bms will flag up and notify the victron comms. These are victron lfp batteries. Even if its not fully integrated comms, a cell out is one in a million, and these will not be the symptoms. It's a clear batt monitor issue, or, a bypassed shunt.
As you say, something definitely not right there. It's worth pointing out, for those unfamiliar with shunts and battery capacity measuring, that the voltage is a definite reliable value, taken and reported without any calculation or modification. However the State Of Charge percentage value is a calculated value, built up over time. It calculates the charge lost and gained over time, from the last time it registered the battery as 100% full. Sometimes the shunt does not register all the charge lost or gained, so the SOC value can be in error, and the error can gradually get worse until it is nonsensical.
There are various reasons for this. Maybe one of the charging paths was installed so it bypassed the shunt resistor, so it doesn't register with the shunt software. Maybe a small continuous drain, below the amps measurement threshold of the shunt, has drained the battery without the shunt accounting for the drain.
The SOC reading is usually reliable, but in this case of the two conflicting readings I would tend to believe the voltage, which is indicating a very much lower SOC than 81%.
Subscribers do not see these advertisements
- Feb 5, 2024
- 514
- 812
- Funster No
- 101,061
- MH
- Etrusco CV540 DB
- Exp
- On and off for about 30 years
It could also be the case that the shunt has been erroneously synced at 100% SOC when it was actually much lower.
I don't know about Victron, but my Renogy shunt will automatically synchronise as 100% if I use the mains charger to fully charge the battery. However, it also allows you to manually sync either at 100% or at a custom value, which in my case I could get from the Fogstar app.
If messing about exploring the menus I guess it would be easy to accidentally sync as 100% when the actual SOC is much lower.
I don't know about Victron, but my Renogy shunt will automatically synchronise as 100% if I use the mains charger to fully charge the battery. However, it also allows you to manually sync either at 100% or at a custom value, which in my case I could get from the Fogstar app.
If messing about exploring the menus I guess it would be easy to accidentally sync as 100% when the actual SOC is much lower.
- Aug 18, 2014
- 25,985
- 155,879
- Funster No
- 32,898
- MH
- Transit PVC
- Exp
- 16 years since restarting
Our hob sits above the worktop.
There we are jumarSame here
Yes. Fascinates me why a purpose built system would not have built in detection so that with no loads it doesn't run?
MisterB
LIFE MEMBER
- Feb 25, 2018
- 7,313
- 17,408
- Funster No
- 52,564
- MH
- Adria 670 SLT
- Exp
- enough to know i shouldnt touch things i know nothing about ....
I'd like to thank all the serious contributers to this thread ....... but to also recognise those who just stirred the lithium pot a little ....
I’m doing my best but, can you explain how the following aligns with the symptoms?
Ian
Mine can do that, but there is still a small draw depending on the mode chosen it can be 0.3a IIRC. But I'm used to switching it on when required, so have just stuck with that. The switch is on my phone and will be on my watch soon, also in the garage, so no bother.....
Our hob sits above the worktop.
Same here
Yes. Fascinates me why a purpose built system would not have built in detection so that with no loads it doesn't run?
Subscribers do not see these advertisements
Join us or log in to post a reply.
To join in you must be a member of MotorhomeFun
Join MotorhomeFun
Join us, it quick and easy!
Log in
Already a member? Log in here.