LiFePO4 at 11.71v

[Hoovie]

I have percentage and volts and cell balance on an app but under loads the voltage dosnt drop much at 1st

If you have percentage, then that is the key value to go for. If you take the Roamer advice (12.9V), then using your table that relates to 20%. So if you avoid going below 20% SOC, you will be using a more accurate way of knowing what to avoid

The level of sag depends on the size of the load of course. if you have typical Motorhome loads, you are unlikely to be pulling more than around 6A or so. If you have an inverter and use saya Microwave or high loads like that, you will see a much bigger sag.
This will show that ... my battery two days ago and used the Microwave... (oh, Voltage is blue line, Current is red line).

The voltage dropped from 13.14V down to 12.34V in 3 minutes when the current pulled hit 97A.
This is why I say the tables are not a good indicator - using voltage vs SOC, I went from around 55% SOC to 14% SOC in three minutes!


PS. Just a point on that table. It has a significant terminology error. it says on the Lithium 20% (DofD). It should say 20% (SoC). DofD is "Depth of Discharge" and 20% DofD is actually 80% SoC. (DofD + SoC = 100%).

 

[Pausim]

I have a roamer lifepo4 they have told me rely on the voltage try not going below 12.9v as per the chart

The rate of discharge also makes a big difference to the voltage curve so I don’t see how voltage can be relied on. Bad advice. This graph is for a Relion LiFePO4 but the chemicals and the principle are the same.

 

[bigtwin]

PS. Just a point on that table. It has a significant terminology error. it says on the Lithium 20% (DofD). It should say 20% (SoC). DofD is "Depth of Discharge" and 20% DofD is actually 80% SoC. (DofD + SoC = 100%).

Indeed. Language/terminology matters.

Ian

 

[Hoovie]

The rate of discharge also makes a big difference to the voltage curve so I don’t see how voltage can be relied on. Bad advice. This graph is for a Relion LiFePO4 but the chemicals and the principle are the same.

This is why a proper SOC monitor is often worth the money as they use this kind of logic to adapt how the State of Charge is calculated and adjust it accordingly. The effect is more 'dramatic' on Lead but still has an impact on Lithium.
The Victron BMVs and Smartshunt has a way to apply that. some of the cheaper monitors, for example the AliMeter don't (although that one is still fine value for money).
I really don't know if the built-in SOC monitors in the batteries do. I would hope so but to be honest I suspect they are rarely that sophisticated. I find the reported SOC of my Batteries are usually pretty close to the SOC of the BMV that I have fitted to them. Not always the same, but close enough not to be a concern.

 

[NASHMAN600]

I have a pair of KS 120 Low profile..
All last season and up to November the App and SOC tallied with the voltage .
Then I just looked at the SOC ,not voltage.
Somehow like others have found the SOC and voltage ,became out of balance,although one of the pair was Shut down ,the app still showed 85%.
this was in the Cold spell at the end of the year.
When I removed them and split them from parallel,they then showed their true Soc ..
I will only trust Voltage in the future and as on my old MH I will disconnect and separate the Batteries to measure individual battery voltage..
Great batteries, been fantastic, just waiting for spring now...

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[The Artilleryman]

Sorry, but relying on voltage with LiFePO4, is a waste of time. IT WILL NOT GIVE YOU AN ACCURATE STATE OF CHARGE.

The only way, is to record ah in and ah out, in our case using something like the Victron BMV.

 

[The Artilleryman]

Battery has now had 18 hours @ 4.4a to 5a charge. Electrics shut down and fuse pulled on PDA 0.0a discharge. Will let it rest till tomorrow morning and then discharge for 20 hours @ 1a - interior lights on - and note SOC and volts.

Does anybody know if there is a way to get more info from the KS Energy app. other than current state of battery, looking for discharge data to when the battery discharged.

 

[Googlebot]

Battery has now had 18 hours @ 4.4a to 5a charge. Electrics shut down and fuse pulled on PDA 0.0a discharge. Will let it rest till tomorrow morning and then discharge for 20 hours @ 1a - interior lights on - and note SOC and volts.

Does anybody know if there is a way to get more info from the KS Energy app. other than current state of battery, looking for discharge data to when the battery discharged.

I would give Neil a ring at KS energy. He was really helpful when I got an inverter via him.

He may be able to answer why you are having issues too.

He will know the app inside out too.

 

[MichaelT]

Battery has now had 18 hours @ 4.4a to 5a charge. Electrics shut down and fuse pulled on PDA 0.0a discharge. Will let it rest till tomorrow morning and then discharge for 20 hours @ 1a - interior lights on - and note SOC and volts.

Does anybody know if there is a way to get more info from the KS Energy app. other than current state of battery, looking for discharge data to when the battery discharged.

Do you have the ks energy 2.0 app?

 

[Ingwe]

Been following the thread with interest.

The poster having problem with the shunt giving weird readings when it’s cold doesn’t accord with my experience with the same make of lithium battery (Ecotree). We’ve spent the last three nights which have been cold (going down to -4°) and my Victron SmartShunt is giving the same readings as usual. The SOC is currently 80% and the voltage is 13.50v. I have had no erratic readings and have had no issues with the two 110ah Ecotree batteries (other than not winning them and having to pay full price).

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[Googlebot]

Been following the thread with interest.

The poster having problem with the shunt giving weird readings when it’s cold doesn’t accord with my experience with the same make of lithium battery (Ecotree). We’ve spent the last three nights which have been cold (going down to -4°) and my Victron SmartShunt is giving the same readings as usual. The SOC is currently 80% and the voltage is 13.50v. I have had no erratic readings and have had no issues with the two 110ah Ecotree batteries (other than not winning them and having to pay full price).

Perhaps I have a setting wrong on the smart shunt then?

Yesterday morning they showed 100% but the engine battery was also showing a charge from the battery master which would indicate that the voltage had risen.

I have changed the setting so it won’t show the SOC until it synchronises if disconnected and it still goes to 100% when it’s cold.

I have no idea why, I suspect it may be the solar controllers as occasionally they lock out and have to be disconnected which is also weird as they are Votronic so not cheap.

Short answer is I don’t think the batteries are to blame but I actually have no idea.

 

[Ingwe]

Perhaps I have a setting wrong on the smart shunt then?

Yesterday morning they showed 100% but the engine battery was also showing a charge from the battery master which would indicate that the voltage had risen.

I have changed the setting so it won’t show the SOC until it synchronises if disconnected and it still goes to 100% when it’s cold.

I have no idea why, I suspect it may be the solar controllers as occasionally they lock out and have to be disconnected which is also weird as they are Votronic so not cheap.

Short answer is I don’t think the batteries are to blame but I actually have no idea.

I agree it’s unlikely to be the batteries. But I’m not really in the know about this. I’ll be looking at the responses to your issue with interest.

 

[Ingwe]

I agree it’s unlikely to be the batteries. But I’m not really in the know about this. I’ll be looking at the responses to your issue with interest.

Edit: if it’ll help, I’ll gladly post screen shots of my Smart Shunt settings.

 

[The Artilleryman]

Do you have the ks energy 2.0 app?

Yes. It's time I got out and fitted the rest of the kit then I would be able to see exactly what's happening.

 

[Lenny HB]

I have no idea why, I suspect it may be the solar controllers as occasionally they lock out and have to be disconnected which is also weird as they are Votronic so not cheap.

That is a common problem with Lithium on the Votronic, I think there are 4 Lithium settings try a different one if there is another one that is OK with your batteries.

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[Googlebot]

That is a common problem with Lithium on the Votronic, I think there are 4 Lithium settings try a different one if there is another one that is OK with your batteries.

Ah, good point Lenny. I never thought of that.

I was on the verge of selling them and going Victron for the lot but will try that first. Wonder if that’s why they keep going wrong.

Edit: if it’ll help, I’ll gladly post screen shots of my Smart Shunt settings.

It will all help someone!

Will post my settings below.

Ignore the SOC, I know it’s wrong. Just waiting for them to fully charge and synchronise.

What a great forum this is!

 

[Googlebot]

Yes. It's time I got out and fitted the rest of the kit then I would be able to see exactly what's happening.

Keep us updated.

It all helps.

 

[Ingwe]

 

[pat100]

Sorry if this has already been said or is irrelevant but the BCA PDU inbuilt charger doesn’t have a lithium profile AFAIK

 

[The Artilleryman]

Correct, but I'll be fitting a Victron IP22 charger.

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[pat100]

Correct, but I'll be fitting a Victron IP22 charger.

Ah! Being filthy rich, I bought the Apuljack one for compatibility but I think the IP22 fits in, also, with a change of plug. I only realised after the event that the on/off switch on the new unit may be awkward to reach but is rather useful.

 

[The Artilleryman]

On Bailey MH's the BCA PDU has 2 outputs :-
1.12v psu to run habitation electrics when on EHU
2. 12v battery charger

So on mine it's a case of disconnect the charger, but leave the psu in place.
Which also means I need to find somewhere to securely mount the Victron IP22, and will probably have to dismantle the wardrobe to do this and the other wiring.

 

[pat100]

Sounds good. I think my PDU is different. Hope it all works out well.