Daly Bms problem

[wildebus]

I misunderstood your first post David, I thought you'd suggested it was OK to charge Lifepo4 below zero as long as it was done at low current. The flow chart doesn't show that, only a means of using available solar to heat the packs prior to charging.
150W of solar isn't something that's readily attainable in the winter for your average camper but anyone with directional panels could possibly benefit from the above and if the control unit isn't commercially available? then it would be a relatively simple device to construct with either logic ICs or an Arduino / Raspberry Pi.
Merl

you didn't misunderstand, and I did suggest that.
Have a look at the flow chart again..... (and follow the flow and not stop at just the initial "Turn on Heating Function" text)

 

[alwaysared]

Can i ask what sort of heat pad did you use for your batteries i have 4 x 100amp Relion lithium and i dont know what you use that is reliable thanks.

Jeff

I've been in your van with the propex heater on so like me I don't expect your temperature will ever be 5°c let alone below it

Regards,
Del

 

[Derekoak]

Largest number? or largest per capita? I don't know which, but the numbers will be very different.
Also Norwegians I believe tend to live mainly in the metropolitan areas and not spread out around the Country, so the typical journey is a lot shorter. Ideal for electric cars.
Electric Car Battery packs have a heating/cooling system so they will not get too hot or too cold. -20C ambient or whatever is not what the batteries will be at - especially as the cars are plugged into power (even the petrol ones) for pre-heating where possible.
And it is quite possible the tax on Electric cars is way more friendly in Norway than their insane taxes of 'normal' cars to encourage people to buy them. it is very easy to influence sales with sticks as well as carrots

77.5% ..... statistics, damn statistics, and means nothing without the background data behind it.

I am just back from a Northern Norway trip and I think you are right I saw EV s with Norway plates but not anywhere near 77%. Perhaps 15%. The EVs must be concentrated in the urban South.

 

[merl]

you didn't misunderstand, and I did suggest that.
Have a look at the flow chart again..... (and follow the flow and not stop at just the initial "Turn on Heating Function" text)

Following the chart alone I interpret it as follows:
After the "Turn on heating function" box you get to choose if the available current (at 14.4V) is greater or less than 0.1C, (10A in this 100Ah scenario) , if yes then you go to the right and through the heating prior to charging rules. If NO then you go to the left and "no heating occurs" and the flow chart stops. I interpret this (from the flowchart alone) to mean STOP, go no further, No heating No Charging. Otherwise there should be an additional lower box below on the left with "charge at available current".
Also for maximum efficiency the uppermost box on the right ("power is for heater pads, no charge rate") should read, "Charge at 0.1C, remainder to the heater pads"
Do you have any additional text/info/ documentation to augment the flowchart David?
Merl

 

[wildebus]

Following the chart alone I interpret it as follows:
After the "Turn on heating function" box you get to choose if the available current (at 14.4V) is greater or less than 0.1C, (10A in this 100Ah scenario) , if yes then you go to the right and through the heating prior to charging rules. If NO then you go to the left and "no heating occurs" and the flow chart stops. I interpret this (from the flowchart alone) to mean STOP, go no further, No heating No Charging. Otherwise there should be an additional lower box below on the left with "charge at available current".
Also for maximum efficiency the uppermost box on the right ("power is for heater pads, no charge rate") should read, "Charge at 0.1C, remainder to the heater pads"
Do you have any additional text/info/ documentation to augment the flowchart David?
Merl

Ok, bear in mind this is a Chinglish Flowchart first of all. The "Turn on the heating function" should be better read as "Switch to heating logic" or similar.
If current is below 10A at 14.4V, turn left. No need to turn on heater. It doesn't say "do not charge " any more than it says "charge".
If current is above 10A@14.4V, turn right, heat pads until 5C , etc.

Now WHY on earth if the current was below 10A, would there be what you are concluding an "ignore current entirely" process? Where is the logic of ignoring up to 144W of available power when on the right hand side they divert 130W of power to the heater pads between 5C and 10C?
As far as maximum efficiency goes, I reckon they probably looked at the different options and decided on the most effective (could be technical, or could be financial?). Would you not think that is likely? Yes, it could be done as you suggest perfectly well I have no doubt, but there will be design reasons for not doing that which you or I are not privy to.


Of course, you must read it the way you want to - that is up to you. I think I know what it means (and I have had the benefit of discussions with one of the QC engineers in China for the product this applies to, but that is by the bye). If I am wrong, then I am wrong

Additional text/info/etc.? no, just common sense as far as the flowchart goes. Just ignore it is probably your best bet if you don't get the logic. As I said in the post, this was posted for "entertainment purposes" and people need to do their own research on matters sometimes.

 

[merl]

David, your right, the flow chart isn't terribly well written,
Now WHY on earth if the current was below 10A, would there be what you are concluding an "ignore current entirely" process? Where is the logic of ignoring up to 144W of available power when on the right hand side they divert 130W of power to the heater pads between 5C and 10C?
Because the heaters take 130W which is approximately the same as the available power.
The designers decided that the charging process didn't start until there was a reasonable surplus of power available over and above the heater current and they decided to choose a threshold 14W, seemed sensible and coincided with 0.1C at 14.4 volts which are nice round numbers.

It doesn't say "do not charge " any more than it says "charge".
True but when a flow chart is written you don't list all of the things that you don't do unless you've previously been instructed to do so, it's a rule of logic (which I get). An allow charge instruction was not previously given so there would be no reason to give an inhibit charge instruction. An example is in the flow chart, the "turn on the heating" function (allow heating) is followed by "heating function not activated" (inhibit heating) command.

As far as maximum efficiency goes, I reckon they probably looked at the different options and decided on the most effective (could be technical, or could be financial?). Would you not think that is likely? Yes, it could be done as you suggest perfectly well I have no doubt, but there will be design reasons for not doing that which you or I are not privy to.
Or maybe it's simply because (as I suspect) they don't actually advocate sub zero charging and IF they did say "Charge at 0.1C, remainder to the heater pads" this would knacker your battery.

I can't find ANY reference to sub zero charging of standard lifepo4s being permissible anywhere on the internet David, this coupled with all of the red flags above leads me to think that it's more likely that the R&D guy you spoke to misunderstood the flow chart and/or the sub zero charging process or you misunderstood him when he was trying to explain an 'improved version of sub zero charging from solar only'. Was the conversation in Chinglish as well David? That could explain it
Merl

 

[wildebus]

We will have to disagree then. Your first rebuttal makes no sense to start with.
So you are saying as there is only enough power to use on the heaters, let's not bother with powering the heaters??? Sorry, but after that idea, not going to spend time discussing it.
Time to draw a line.

 

[merl]

We will have to disagree then. Your first rebuttal makes no sense to start with.
So you are saying as there is only enough power to use on the heaters, let's not bother with powering the heaters??? Sorry, but after that idea, not going to spend time discussing it.
Time to draw a line.

Sorry if I've upset you David, It's not easy getting across the intended attitude in a written message hence my attempt to use imojis. It doesn't seem to have worked. Maybe I'm wrong and I'm misunderstanding your vibe. Anyway, sorry again. Dont read any further down if you dont want to and we'll leave it there.

My rebuttal makes perfect sense, if there was little or no surplus power then you'd be heating the batteries for no reason at all!
Why is the notion that a company could make that decision so implausible?
Merl

 

[SquirrellCook]

Merl, if your batteries were nearly flat and cold. Surly you would want to charge them.
Just remember making sense is a very personal thing.

Mark about to see if my lithium's are warm enough to charge.

 

[merl]

Merl, if your batteries were nearly flat and cold. Surly you would want to charge them.
Just remember making sense is a very personal thing.

Mark about to see if my lithium's are warm enough to charge.

Merl, if your batteries were nearly flat and cold. Surly you would want to charge them.

Of course, but if the available power was not actually able to give any charge and only warm them up then I could see why a company would choose not to advocate doing so. That's my point
Merl

 

[Nabsim]

I've been in your van with the propex heater on so like me I don't expect your temperature will ever be 5°c let alone below it

Regards,
Del

The only time my battery’s have got near to zero is if I leave the van parked up without being in it. Mine are inside under one of the side benches. Never been a problem at all when I am in the van as I usually am

 

[Chasn]

This is just a guess, as I don't have the time to prove it.
When the Daly BMS's (I have two in one of my setups) get cold and stop accepting a charge they seem to get confused as to their state of charge. Also in my setup I have a Victron BMS. When the the Daly's stop accepting and charge the Victron BMS jumps to 100% charged.
My lithium batteries are heated from the Eberspaecher exhaust, working on the theory that if it's that cold the heating will be on.
The only real way to calibrate the BMS's is to fully charge the batteries.

Mark

A Victron shunt will always show 100% on power up so if it is connected downstream of a BMS it can lose its power and will therefore show 100% on reconnect. For that reason the Victron shunt should always be directly connected to the battery. Its power consumption is less than 1mA so it takes over a month for it to consume just 1Ah. The low voltage shut off protection of a BMS will leave a margin of a few percent above total discharge. Even if this is just 2%, on a pair of 90Ah batteries this would power a Victron shunt for 5 months so directly connecting it to the battery is very unlikely to cause a problem.

 

[Lenny24v]

If you are talking about the Victron shunt always showing 100% on power up there is a setting you alter to stop this happening and it’s recommended to switch to this as shown in the photo , batter starts synchronised to off

 

[SquirrellCook]

A Victron shunt will always show 100% on power up so if it is connected downstream of a BMS it can lose its power and will therefore show 100% on reconnect. For that reason the Victron shunt should always be directly connected to the battery. Its power consumption is less than 1mA so it takes over a month for it to consume just 1Ah. The low voltage shut off protection of a BMS will leave a margin of a few percent above total discharge. Even if this is just 2%, on a pair of 90Ah batteries this would power a Victron shunt for 5 months so directly connecting it to the battery is very unlikely to cause a problem.

In many cases when a Victron shunt is connected to a lithium managed battery it is not possible to connect directly to the cells. So if they lithium setup choses to shut down it will confuse the Victron device. The only answer to reset the BMS's is by fully charging.

 

[wildebus]

I would also suggest turning off the "sync to 100% on reset" switch on the Victron Smartshunt/BMVs to avoid this 100% reading (and avoiding the "always show 100% on power up" error).
This SOC reset can give a very incorrect perception on the battery true State of Charge, especially with Lithium where it is very hard to even ballpark by voltage.
As Squirrellcook says, just about the only way to know the state of charge is to fully charge the batteries until they take no more current. (another option is to drain them till they die and then set the SOC at 0%, but that is less friendly on the battery )

 

[merl]

Following the 'discussion' that David an I had previously in the post I've spent a few hours digging deep into the net for available info on charging Lifepo4 batteries. I found a couple of very useful papers and the results are quite surprising.
The issue basically centres around this perceived 'knee' that we have at 0 Deg C which we all understand as 'OK to charge above zero deg and it's very bad to charge below zero'. This is not the case and just like many/all of the other battery chemistries, charging, efficiency, harm etc are altered by temperature for sure but GRADUALLY and not one specific point on the temperature scale.
Just like a 30mph speed limit through a village it doesn't mean that it's SAFE to drive at 29 and reckless to drive at 31 (I'm not talking about legality here btw)
0 deg celcius charging point was chosen as the 'limit' rather like the 30mph above.
What does this mean as far as the typical motorhome Lifepo4 user?
For normal day to day at normal temperatures charging not a great deal.
For charging at low temperature AROUND the zero deg it get's interesting.
You CAN charge at below zero but there are rules to follow.
More importantly perhaps you need to know that some caution should be exercised when charging just above zero too.
An additional complication occurs near full charge at low temperatures.
It's a long detailed paper and when I've got my teeth around it properly I'll post the details fully here in a separate post. I don't want to post something that I have to retract further down the line and I want to keep it as simple to understand as possible.
I think it would be a good idea have a few additional sets of eyes looking at it before I post anything so In the meantime If anyone wants the paper PM me and I'll send you a PDF, good for getting you off to sleep at night if nothing else!
Merl

 

[Nabsim]

Yes it said in the data sheet for mine they can be charged at lower temps than most folks say but at reduced rate as David said.

At the end of the day I have been happy charging mine at lower temps but I wouldn’t push big amps into them if they ever were at zero. I have put a single 30A Victron IP22 charger set to night charge rate of 15A into my 2 x 100Ah batteries but would not use full 30A or switch the second charger on. It’s very rare my battery’s get as low as zero as I am normally in the van with heating on though as well.

People need to do their own investigations and make their own decisions rather than just asking on a forum though, you can get good advice but you can also get absolute bs. This site is much better than a lot of places but I fairly regularly disagree with stuff but I will usually just pass by unless I know it’s wrong or think it’s dangerous advice. Too many times folks just argue for the sake of it.

 

[wildebus]

Indeed so.
I post information if I think it may be useful or of interest and I believe to be accurate - either from my own emperical observations and research or from sources that I trust.
If someone doesn't believe me, than I have no issues with that - they can just ignore what I say and do their own research. No worries.
What I am not going to do is get into some kind of pissing contest to provide extensive detailed proof of what I am saying, or to try and prove others wrong. Life is too short and I don't get paid enough to do that on this forum.

 

[Geek]

Of course, you must read it the way you want to - that is up to you. I think I know what it means (and I have had the benefit of discussions with one of the QC engineers in China for the product this applies to, but that is by the bye). If I am wrong, then I am wrong

I've spoken to two fairly authorative sources who both told me that all the concern about charging cold lithium cells is balderdash.

Yes, if it is colder than -20 you should not charge at all, but when did batteries last get that cold in the UK?

For normal (or even fairly abnormal) winter conditions, batteries inside the van will sometimes fall below 5 degrees, but that's OK. At present I have 200 watts of solar panels, facing south, angled to collect as much sun as possible. Typical output about 0.5A at best.

If we get a gloriously sunny clear, bright day, perhaps the panels migh give half their rated output, but that 8 amps would not be a problem even if it all went into the cold battery (it wouldn't).

Right now my only problem is that the solar controller failed and during the wait for a replacement (fitting, not delivering: I did have a spare) the battery voltages dropped too far for comfort, so I had to start the engine. At -5 temperatures, whacking 35 amps from the b2b didn't seem a smart move, so I removed the lithium battery and took it into the house to charge in the warm. So now that's full and the rest of the bank (300AH of deep discharge SGM) is gradually building up when the sun makes an appearance.

I guess that when I put the lithium back in circuit, it won't take much current because it will be full. In fact, it's more likely to discharge to boost the other batteries up to 13.2v

 

[merl]

I've spoken to two fairly authorative sources who both told me that all the concern about charging cold lithium cells is balderdash.

Yes, if it is colder than -20 you should not charge at all, but when did batteries last get that cold in the UK?

For normal (or even fairly abnormal) winter conditions, batteries inside the van will sometimes fall below 5 degrees, but that's OK. At present I have 200 watts of solar panels, facing south, angled to collect as much sun as possible. Typical output about 0.5A at best.

If we get a gloriously sunny clear, bright day, perhaps the panels migh give half their rated output, but that 8 amps would not be a problem even if it all went into the cold battery (it wouldn't).

Right now my only problem is that the solar controller failed and during the wait for a replacement (fitting, not delivering: I did have a spare) the battery voltages dropped too far for comfort, so I had to start the engine. At -5 temperatures, whacking 35 amps from the b2b didn't seem a smart move, so I removed the lithium battery and took it into the house to charge in the warm. So now that's full and the rest of the bank (300AH of deep discharge SGM) is gradually building up when the sun makes an appearance.

I guess that when I put the lithium back in circuit, it won't take much current because it will be full. In fact, it's more likely to discharge to boost the other batteries up to 13.2v

Hi,
From what I've found thus far there are 3 issues that affect permissible charging, temperature, current and the state of charge. (SOC)
All of these affect the charging in a gradual, linear-ish way, non of them (including temp) change drastically at a specific point ie drop off a cliff suddenly.
Now people like things to be binary, they want a yes or no answer to the question 'is it ok to charge my lithium battery right now?' This is an impossible question to answer accurately when there are three 'grey variables' to consider and take into account. In order to give black and white advice to a very grey area the 'you should not charge lithium below 0deg advice was widely adopted'.
Considering the above it's easy to see that following this advice means we're being over cautious at -1 deg and under cautious at +1 deg, after all there's very little difference between 1 deg and -1 deg yet we're told one is permissible and the other isn't.
Combine charge current and SOC in their most undesirable state and someone could easily end up charging at 40A (or more) from a B2B at say +2 deg temp into a battery with a 80% or greater SOC and he/she would feel safe in doing so when it appears that it would damage the battery irreversibly.
However say 10A of charge at -5 deg would be fine as long at the battery's SOC was below 70%.