Lithium Charge and Discharge Rates

[Martynovo]

Im wondering about the discharge rate from my recent lithium install. A few months ago in a thread I asked why my batteries said only 80% charge when voltage said they were full. That wasn’t solved, so trying to see if at least the discharge pattern is correct by putting on a substantial load.

It’s 2x100 amp hour lithium batteries, Victron shunt, Renogy 50 amp B2B , Renogy 2000w inverter, Victron mains charger so Electroblock fuse removed, Battery Master lead moved.

Load tried was a 565watt small kettle with 500ml of water. At start shunt says Leisure battery 13.8v 78% full. On solar or EHU cant get it higher than that. Voltage drops immediately on kettle switch on to 12.93v, 44.6amp load. Question 1. Should it go that low?. Solar input ranging from 10watts to 60watts. On a chart I have 12.9v is absolute lowest a lithium should be allowed to go. What would happen if I put on a 1000watt load?

Immediately after water boiled and switched off voltage jumps to 13.2v. 10mins later it was 13.3v and 75% full but as solar input now low after another 5 minutes it only read 13.38v so switched on engine.

Shunt immediately said warning high starter battery voltage 14.2v , a 3.9amp output from alternator but after 30 seconds it dropped to 2.0 amps then on engine rev increase charged at 11.4amps . In 3 minutes leisure battery was clearly charging well so engine switched off.

2: Is Alternator output very high, there appears no way I can regulate that.? (2016/17 316 CDI Sprinter based Hymer)

3. Is what the voltage is saying correct , and that the battery is actually full when the shunt only says 78 %? If so I can live with that. Thanks.

 

[Pausim]

I would start with checking that the Victron shunt has been set up with the correct Voltages and tail current so that it knows when to synchronise to showing 100%.

 

[Martynovo]

Tail current set to 2.0, charge voltage 14.1. Ive tried sync and setting to 100% but after a while it returns to the low range. Peukert is 1.05. .

 

[AdrianChen]

Does the shunt history show the battery discharging after you've set it to 100%?

In calculating the SOC the shunt just counts amps in and out.

The voltage figure in the setting for charged voltage is used with the tail current to determine when the shunt should sync to 100%, it isn't involved in calculating the SOC after that. So when the battery is above the charged voltage setting, and the tail current is less than the setting for 3mins, the shunt sets to 100%. Thereafter the SOC goes up or down based on the amps in and out - so if the SOC is reducing the shunt should show a discharge current......

Do you have a smart alternator?

 

[jonasw19]

2: Is Alternator output very high, there appears no way I can regulate that.? (2016/17 316 CDI Sprinter based Hymer)


I wonder if your Hymer came with a standard B2B from the factory? Our 620 on a 2016 sprinter had a 45 amp Votronic B2B from new. If so you may have got 2 fighting each other.

Your charging voltage should be around 14.3v.
The B2B charges at ca. 45 amps up to about 99% then gradually reduces over a long time to get to 100%.

Jon

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[Martynovo]

Does the shunt history show the battery discharging after you've set it to 100%?

In calculating the SOC the shunt just counts amps in and out.

The voltage figure in the setting for charged voltage is used with the tail current to determine when the shunt should sync to 100%, it isn't involved in calculating the SOC after that. So when the battery is above the charged voltage setting, and the tail current is less than the setting for 3mins, the shunt sets to 100%. Thereafter the SOC goes up or down based on the amps in and out - so if the SOC is reducing the shunt should show a discharge current......

Do you have a smart alternator?

I dont think I have a smart alternator and assume its one of the last ones without it. The Hymer was built in mid 2016 but not registered until 2017

 

[Martynovo]

2: Is Alternator output very high, there appears no way I can regulate that.? (2016/17 316 CDI Sprinter based Hymer)


I wonder if your Hymer came with a standard B2B from the factory? Our 620 on a 2016 sprinter had a 45 amp Votronic B2B from new. If so you may have got 2 fighting each other.

Your charging voltage should be around 14.3v.
The B2B charges at ca. 45 amps up to about 99% then gradually reduces over a long time to get to 100%.

Jon

An interesting idea but I dont think so as the charge was originally from the EBL30. Your comment about charging at 99% made me look again. The shunt was set at 98% by default, Ive just changed it to 99% so give it an hour on solar and I will look again.

 

[AdrianChen]

I dont think I have a smart alternator and assume its one of the last ones without it. The Hymer was built in mid 2016 but not registered until 2017

I don't think the alternator voltage is too high - so I guess the warning is coming up because the setting in the Victron connect amp needs changing to something more appropriate - if you don't have a smart alternator, try setting it to 14.6v high, and 12.2v for low - or just disable the alarms!

 

[AdrianChen]

Your question 1 - under load the battery voltage dropping down is to be expected - doesn't strike me as too low for a high load - just in case, what size cables do you have between the batteries and the inverter, and how long is the cable run?

 

[LostInSpace]

Our 620 on a 2016 sprinter had a 45 amp Votronic B2B from new

I think Hymer are now using a Schaudt WA121545.

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[DBK]

Im wondering about the discharge rate from my recent lithium install. A few months ago in a thread I asked why my batteries said only 80% charge when voltage said they were full. That wasn’t solved, so trying to see if at least the discharge pattern is correct by putting on a substantial load.

It’s 2x100 amp hour lithium batteries, Victron shunt, Renogy 50 amp B2B , Renogy 2000w inverter, Victron mains charger so Electroblock fuse removed, Battery Master lead moved.

Load tried was a 565watt small kettle with 500ml of water. At start shunt says Leisure battery 13.8v 78% full. On solar or EHU cant get it higher than that. Voltage drops immediately on kettle switch on to 12.93v, 44.6amp load. Question 1. Should it go that low?. Solar input ranging from 10watts to 60watts. On a chart I have 12.9v is absolute lowest a lithium should be allowed to go. What would happen if I put on a 1000watt load?

Immediately after water boiled and switched off voltage jumps to 13.2v. 10mins later it was 13.3v and 75% full but as solar input now low after another 5 minutes it only read 13.38v so switched on engine.

Shunt immediately said warning high starter battery voltage 14.2v , a 3.9amp output from alternator but after 30 seconds it dropped to 2.0 amps then on engine rev increase charged at 11.4amps . In 3 minutes leisure battery was clearly charging well so engine switched off.

2: Is Alternator output very high, there appears no way I can regulate that.? (2016/17 316 CDI Sprinter based Hymer)

3. Is what the voltage is saying correct , and that the battery is actually full when the shunt only says 78 %? If so I can live with that. Thanks.

The charging voltage for a lithium battery should be around 14.4 volts plus or minus a little if that is what the battery maker recommends.

Under load the battery voltage will drop. The 12.9 volts you mention is the resting voltage of a battery not under load or charging. Seeing 12.9 volts under load is nothing to worry about.

My suspicion is your shunt isn't reporting correctly either due to a fault or incorrect setup. I assume you have told it you have 200Ah of capacity?

 

[Martynovo]

2: Is Alternator output very high, there appears no way I can regulate that.? (2016/17 316 CDI Sprinter based Hymer)


I wonder if your Hymer came with a standard B2B from the factory? Our 620 on a 2016 sprinter had a 45 amp Votronic B2B from new. If so you may have got 2 fighting each other.

Your charging voltage should be around 14.3v.
The B2B charges at ca. 45 amps up to about 99% then gradually reduces over a long time to get to 100%.

Jon

Having put the efficiency up to 99% from the 98% default with a dim 0.6amp solar charge the voltage is up to 14.06v - the highest its been. So thanks very much. Still only says 77%!

 

[Martynovo]

The charging voltage for a lithium battery should be around 14.4 volts plus or minus a little if that is what the battery maker recommends.

Under load the battery voltage will drop. The 12.9 volts you mention is the resting voltage of a battery not under load or charging. Seeing 12.9 volts under load is nothing to worry about.

My suspicion is your shunt isn't reporting correctly either due to a fault or incorrect setup. I assume you have told it you have 200Ah of capacity?

Thats a relief - thankyou. So 12.9v is OK. If I put on a larger load will it go down further, if so is there a cut-off point?
The shunt is set up for 200 Ah.

 

[Martynovo]

Your question 1 - under load the battery voltage dropping down is to be expected - doesn't strike me as too low for a high load - just in case, what size cables do you have between the batteries and the inverter, and how long is the cable run?

cables are stamped 100 amp, swg3 and no more than 40cms

 

[Pausim]

I dont think I have a smart alternator and assume its one of the last ones without it. The Hymer was built in mid 2016 but not registered until 2017

I had a 2015 Hymer on a Mercedes chassis and that had a smart alternator. If it has AdBlue it probably has a smart alternator. Mercedes didn’t play the Fiat game of providing vehicles without smart alternators for converters.

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[headlight]

Thats a relief - thankyou. So 12.9v is OK. If I put on a larger load will it go down further, if so is there a cut-off point?
The shunt is set up for 200 Ah.

Yes a larger load will pull the battery voltage down lower.
When my 230AH LifePo4 and 2,000 watt inverter are powering my air fryer my battery voltage drops to about 12.6v - 12.5v.
iirc you posted that your charged voltage on your shunt is set at 14.1v.
That should be a little higher depending on your battery manufacturer specs.
On my Fogstar LifePo4 my fully charged voltage is set at 14.2v as that is the 100% SOC voltage for my battery and the correct voltage for the shunt to reset to 100%.
Without the correct shunt settings SOC will be out.

 

[headlight]

cables are stamped 100 amp, swg3 and no more than 40cms

If you go on the 12v Planet website they have cable calculators.

 

[Martynovo]

Your question 1 - under load the battery voltage dropping down is to be expected - doesn't strike me as too low for a high load - just in case, what size cables do you have between the batteries and the inverter, and how long is the cable run?

cables are stamped 100 amp, swg3 and no more than 40

Yes a larger load will pull the battery voltage down lower.
When my 230AH LifePo4 and 2,000 watt inverter are powering my air fryer my battery voltage drops to about 12.6v - 12.5v.
iirc you posted that your charged voltage on your shunt is set at 14.1v.
That should be a little higher depending on your battery manufacturer specs.
On my Fogstar LifePo4 my fully charged voltage is set at 14.2v as that is the 100% SOC voltage for my battery and the correct voltage for the shunt to reset to 100%.
Without the correct shunt settings SOC will be out.

Ecoflow say it can go higher but I thought I was following the general recommendations in several threads. So a gentle tweek to 14.2v but I have to wait for sun, nothing promised today. Thanks

 

[headlight]

cables are stamped 100 amp, swg3 and no more than 40

Ecoflow say it can go higher but I thought I was following the general recommendations in several threads. So a gentle tweek to 14.2v but I have to wait for sun, nothing promised today. Thanks

Ecoflow ? So it's a powerbank ?

 

[Martynovo]

Ecoflow ? So it's a powerbank ?

Oops! Sorry, Ecoworthy. As a retired Ecologist you would think I know better.! Either way its a misuse of "Eco"

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[DBK]

Thats a relief - thankyou. So 12.9v is OK. If I put on a larger load will it go down further, if so is there a cut-off point?
The shunt is set up for 200 Ah.

There will be a maximum discharge rate for the batteries but I doubt you will ever get near it. If you have a spec for the batteries it should say what it is.

 

[Martynovo]

Thanks. Ive discovered it says 100 amps for a 100 amp hour Ecoworthy battery and has inbuilt BMS that limits discharge according to their site. I have 2 but 100 amp hour discharge is a huge draw so wont be approaching that under normal circumstances.
I see you are just the other side of the Tamar with no sun to test anything today but patience.

 

[headlight]

Thanks. Ive discovered it says 100 amps for a 100 amp hour Ecoworthy battery and has inbuilt BMS that limits discharge according to their site. I have 2 but 100 amp hour discharge is a huge draw so wont be approaching that under normal circumstances.
I see you are just the other side of the Tamar with no sun to test anything today but patience.

So 2 x 100AH batteries in parallel with 100AH continuous discharge BMS's = 200AH power and 200AH max continuous discharge.
Similar to my single 230AH battery with 200AH BMS.
I run a 2,000 watt inverter off mine but limit my max draw at any one time to about 1,500 watts as its not good practice to run the inverter at max, especially with cheaper inverters.
Runs my 1,400 watt air fryer, 700 watt microwave etc fine.
Not both at the same time obviously.

 

[oldiesontour]

Thanks. Ive discovered it says 100 amps for a 100 amp hour Ecoworthy battery and has inbuilt BMS that limits discharge according to their site. I have 2 but 100 amp hour discharge is a huge draw so wont be approaching that under normal circumstances.
I see you are just the other side of the Tamar with no sun to test anything today but patience.

Your inverter will be capable of drawing in excess of 150ah

 

[Martynovo]

So 2 x 100AH batteries in parallel with 100AH continuous discharge BMS's = 200AH power and 200AH max continuous discharge.
Similar to my single 230AH battery with 200AH BMS.
I run a 2,000 watt inverter off mine but limit my max draw at any one time to about 1,500 watts as its not good practice to run the inverter at max, especially with cheaper inverters.
Runs my 1,400 watt air fryer, 700 watt microwave etc fine.
Not both at the same time obviously.

Thanks, that is very reassuring. An air fryer on 200aH, thats an idea. No surges in power that there is in a microwave.. Just a long drive or a lot of sun afterwards. Im off to Spain in 6 days so hopefully will have both.

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[headlight]

Thanks, that is very reassuring. An air fryer on 200aH, thats an idea. No surges in power that there is in a microwave.. Just a long drive or a lot of sun afterwards. Im off to Spain in 6 days so hopefully will have both.

An air fryer cycles the heating element on and off and the fan runs continuously.
In the case of my 1,400 wat air fryer it draws 1,430 watts for one minute (the fan takes 30 watts) then 30 watts for one minute then 1,430 watts for one minute and so on.
So running the air fryer for typically 20 minutes it is only drawing 1,430 watts for half that time so 10 minutes and the other 10 minutes it is only drawing 30 watts.
A 20 minute run time, for say frozen chips, uses approximately 20 amps so not a big dent in 200AH of LifePo4.
My 700 watt microwave has a start up surge of 1,300 watts then again cycles the heating element on and off so again does not use that much power for the minutes it's on.
I have 230AH of LifePo4, 230 watts of solar and a 60 amp B2B.
I do not need to plug in to EHU at all even in UK winter as my daily winter average use is about 50 amps a day so I can do up to 4 days stationary with no solar or B2B charge input then driving charges the battery back up.
In summer I can remain stationary for weeks at a time as solar covers my usage.