Solar Charge Profile?

[RedFrame]

We have a 325W panel up top driving a Victron 100/15 Smartsolar unit connected to 2 parallel 300Ah Lithium Batteries, which has just been commissioned at the start of this weekend.

I have selected the LifPo charge profile in settings on the controller.

Over the past few days with the sun high in the sky it has consistently delivered close to 15A... but it refuses to charge at over 13.5v and just stays in Bulk.

Batteries are around 70% charged atm, they'll get to 100% on the journey to Swaffham this Thursday.

I'm pretty sure this isn't right, anyone come across this issue? Anyone confirm it is an issue?

Cheers
Red.

 

[Kannon Fodda]

If you only have a 100/15 MPPT controller that is undersized for your 325W panel. The 15A charging rate shows it is at the maximum.

 

[RedFrame]

Yes, I understand that "on occasion" I will loose a few charging amps and am ok with that.

However it will not affect the charge profile.

It should drop out of Bulk after 2 hrs or so and should be charging at around 14.4v unless on float (13.6v or so), that's my understanding.

Cheers
Rex

 

[Vansflyer]

Maybe you need to set the Victron profile to exactly what the lithium battery / BMS wants. The default lithium setting on our Victron was different to what Fogstar says our battery needs. Eg: our float is set at 13.8V for "holiday mode" and absorption @ 14.4V, both as per Fogstar instructions. Our "storage mode is set lower to keep the battery at about 75%.
The bulk time depends on how low the battery is and what is being consumed during the day, someone left the inverter on standby today (me) whilst we were out so ours has bulk charged all day, when in reality it was feeding the fridge fans and the inverter.

 

[paddymcc]

Do you have the ability to see the voltage of the individual cells on the BMS app? Could be that one of the cells is getting to voltage before the others and causing charging to cut off?

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[ChrisL]

I think the default lithium settings in the Victron solar controller provides the following, In the bulk stage, the controller will deliver the maximum amount of current it can until the battery reaches about 97% charged, however long that takes, then it should change to absorption phase and deliver 14.2v until it is 100% full or 2 hrs have elapsed, it should then drop to a float voltage of 13.2v. Your controller is not going to give you the best charging rate because your lithium battery can cope with more then the15 amps that your controller is providing.

 

[Raul]

Yes, I understand that "on occasion" I will loose a few charging amps and am ok with that.

However it will not affect the charge profile.

It should drop out of Bulk after 2 hrs or so and should be charging at around 14.4v unless on float (13.6v or so), that's my understanding.

Cheers
Rex

I see nothing wrong, give it enough time, you will see it at 14.2v providing your loads do not eat into already limited charging rate.
At the moment, you have 600ah of lithium and a max 15a charge, that is shared with loads as well. It will take few days or weeks, depending on you loads intrusion.
Its like filling a bath tub with a spoon . The 600ah barttery will be more responsive to voltage if you would charge it at 120a. That’s a mild 0.2C rate.
Give it 1kw charge, then you will see the voltage rise a bit quicker.

If you have ehu charger, leave it overnight to charge, then solar to top up/ replenish your usage. Your batteries capacity it’s about 7.6kwh, and you solar set up can harvest about 0.8kwh daily.

 

[RedFrame]

I see nothing wrong, give it enough time, you will see it at 14.2v providing your loads do not eat into already limited charging rate.
At the moment, you have 600ah of lithium and a max 15a charge, that is shared with loads as well. It will take few days or weeks, depending on you loads intrusion.
Its like filling a bath tub with a spoon . The 600ah barttery will be more responsive to voltage if you would charge it at 120a. That’s a mild 0.2C rate.
Give it 1kw charge, then you will see the voltage rise a bit quicker.

If you have ehu charger, leave it overnight to charge, then solar to top up/ replenish your usage. Your batteries capacity it’s about 7.6kwh, and you solar set up can harvest about 0.8kwh daily.

Thanks Raul,

We're heading to Swaffham on Thursday morning so will get 114A from the B2B at around 14.2v which should give us 100% within a few hours of the journey.

We draw about 40Ah/24hr so will monitor the Solar over the weekend, I was just concerned that the lower charge voltage may be damaging the batteries as I understood that Bulk/Absorbtion should be 14.2+v.

Cheers
Red.

 

[ChrisL]

Thanks Raul,

We're heading to Swaffham on Thursday morning so will get 114A from the B2B at around 14.2v which should give us 100% within a few hours of the journey.

We draw about 40Ah/24hr so will monitor the Solar over the weekend, I was just concerned that the lower charge voltage may be damaging the batteries as I understood that Bulk/Absorbtion should be 14.2+v.

Cheers
Red.

Have you checked if your B2B is turning on as expected? I found on mine that if the starter battery was fully charged the alternator only put out 13.6v which wasn't enough to trigger the B2B, once I changed the start voltage to 13.6v the B2B opened and the alternator was putting out 14.4v and consequently charging the leisure batteries, it's worth checking otherwise you may arrive with less than full batteries.

 

[RedFrame]

Thanks for the heads up ChrisL , the B2B is working fine, it was the Solar I was concerned with.

Cheers
Red.

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[Raul]

Thanks Raul,

We're heading to Swaffham on Thursday morning so will get 114A from the B2B at around 14.2v which should give us 100% within a few hours of the journey.

We draw about 40Ah/24hr so will monitor the Solar over the weekend, I was just concerned that the lower charge voltage may be damaging the batteries as I understood that Bulk/Absorbtion should be 14.2+v.

Cheers
Red.

Bulk is the term used for max amp/power charging, until voltage raises and hits CV constant voltage, this is 14.2-14.4. Bulk can take hrs or weeks, until battery is full. This duration is dependable on two things: depth of discharge and charge rate.
When bulk is finished, means that voltage has raised and hit the limit set: 14.2-14.4v. At This moment enters absorb, at constant voltage. It stays in absorb CV for a set time, or, until current tappers of to a set value. Usually absorb can be max 2hrs or as little as 15mins. Absorb duration is dictated by CV absorb setting. If set at 14.2v, absorb time can take little longer, compared to 14.4v setting.
Higher voltage only speeds up the charging, nothing else.

 

[RedFrame]

Ahhhhh, that's where I was getting mixed up with the 2 hrs....

Thanks Raul

Cheers
Red.

 

[Lenny HB]

Have you checked if your B2B is turning on as expected? I found on mine that if the starter battery was fully charged the alternator only put out 13.6v which wasn't enough to trigger the B2B, once I changed the start voltage to 13.6v the B2B opened and the alternator was putting out 14.4v and consequently charging the leisure batteries, it's worth checking otherwise you may arrive with less than full batteries.

Better to wire the B2B so it's triggered by the D+, then it will always turn on when the engine is running. Also stops any loop problems when the starter battery is charged from solar or mains.

 

[RedFrame]

Better to wire the B2B so it's triggered by the D+, then it will always turn on when the engine is running. Also stops any loop problems when the starter battery is charged from solar or mains.

Did that Lenny, also put a switch in the signal wire so I have manual override to switch off B2B if I want...

Cheers
Red

 

[autorouter]

In bulk mode, the charger puts out a constant current of 15A, and doesn't control the voltage at all. The voltage will be whatever the battery is at. The voltage should gradually rise as the battery becomes charged. The charger will be continuously monitoring that voltage. It stays in bulk mode until the battery is so full that the 15A current brings the voltage up to the absorption voltage. At that point it flips to absorption mode.

With lithium batteries the absorption and float modes are not really necessary, they are a legacy from lead-acid charging. The 'float mode' isn't really a float mode at all. Float mode means it's slightly above the maximum battery voltage, feeding a small current in to prevent self-discharge and keep the battery at 100% to prevent sulfation. That is something you definitely don't want to do with a lithium battery, it degrades it. However the true 'float voltage' of a lithium battery is quite high, over 14V, so keeping it at a 'float voltage' of 13.5V is OK.

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[RedFrame]

Thank you all for your help so far ... next question...(sorry, this Lithium is new to me... )

As I mentioned there are two Batteries in parallel. One has reached 99% charged the other is at 78%. The solar has moved into Absorbtion and onto Float today and no amps are being delivered...

Surely it would continue charging until both batteries were around 100%?

Edit: Sorry should have said... The DC-DC Charger is doing the same, and having read Lenny's post below, the batteries each have their own on board BMS.

Cheers
Red.

 

[Lenny HB]

Thank you all for your help so far ... next question...(sorry, this Lithium is new to me... )

As I mentioned there are two Batteries in parallel. One has reached 99% charged the other is at 78%. The solar has moved into Absorbtion and onto Float today and no amps are being delivered...

Surely it would continue charging until both batteries were around 100%?

Cheers
Red.

If one battery reaches its charged voltage before the other one the controller would see the battery as charged and switch to absorption mode.

With normal batteries what you are seeing couldn't happen with Lithium the output from the BMS's will be in parallel rather than the batteries themselves I don't really know what goes on when they are paralleled maybe a BMS problem rather than a Battery problem, over to Raul I think.

 

[ChrisL]

Thank you all for your help so far ... next question...(sorry, this Lithium is new to me... )

As I mentioned there are two Batteries in parallel. One has reached 99% charged the other is at 78%. The solar has moved into Absorbtion and onto Float today and no amps are being delivered...

Surely it would continue charging until both batteries were around 100%?

Cheers
Red.

Are those readings from the individual BMS's? And what make and model are the batteries? Also are you using the positive of one battery and the negative of the other or are they wired so you are using the positive and negative of one battery?

 

[RedFrame]

Are those readings from the individual BMS's? And what make and model are the batteries?

Yes the readings are from each battery, they are the AMPS 300Ah from Sterling Power.

Cheers
Red

 

[ChrisL]

That’s interesting, and are they wired diagonally or straight? I know they are in parallel but by diagonally I mean are you using the positive from one and the negative of the other?

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[RedFrame]

That’s interesting, and are they wired diagonally or straight? I know they are in parallel but by diagonally I mean are you using the positive from one and the negative of the other?

For the charging devices? Diagonally as you describe it.

Cheers
Red

 

[ChrisL]

For the charging devices? Diagonally as you describe it.

Cheers
Red

It must be something to do with the BMS then I would think, I wonder if there is a setting for running them as a bank?

 

[Raul]

Check connection on battery with 14.1v. If they are proper wired in parallel, voltage should be equal or no more than 30 ish mv. You have 300mv difference, that’s huge.
Can you see individual cell voltage on that one? Maybe a high cell calls it quits.

 

[RedFrame]

Weird...

Just went out to gather individual cell voltage on the lower battery and both were "Asleep" and would not show in the BMS app.

Applied a load (switched on Maxair) and bot appeared, and furthermore showed this....

Very strange, must have been a Bluetooth communication issue, but I think all looks rosy in the garden...?

Sorry to have wasted your time on the second issue guys.

Cheers
Red.

 

[Raul]

Oh dear, 126mv it’s quite a bit but manageable, in few cycles will reduce nicely. But, the 235mv it’s quite allot. You need to spend a long time in absorb with minimum loads to help balance those cells. No wonder they don’t charge to 100% or close to, at 14v.
A proper balanced battery should have 1-10mv tops, and reach full charge as soon as it hit 14v. The fact it doesn’t, it’s a high cell stops the charge. Repeat absorb at no less than 14.2v few times to help it balance.

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[RedFrame]

Oh dear, 126mv it’s quite a bit but manageable, in few cycles will reduce nicely. But, the 235mv it’s quite allot. You need to spend a long time in absorb with minimum loads to help balance those cells. No wonder they don’t charge to 100% or close to, at 14v.
A proper balanced battery should have 1-10mv tops, and reach full charge as soon as it hit 14v. The fact it doesn’t, it’s a high cell stops the charge. Repeat absorb at no less than 14.2v few times to help it balance.

....?

So for information, these are new batteries that have been sat at or around 50% for about 6 months .

How do I force a "long time" in absorb, and what is a long time...

Thanks for your help.

Cheers
Red.

 

[Raul]

....?

So for information, these are new batteries that have been sat at or around 50% for about 6 months .

How do I force a "long time" in absorb, and what is a long time...

Thanks for your help.

Cheers
Red.

You set absorb at 14.2v, and absorb time at 2hrs and 0 tail current. Every time you discharge a bit, recharge back to spend time in absorb.

The cell at 3.58v it’s 99.99999% charged, while the 3.34v one, it can be anywhere from 30 to 70% charged. Your total capacity will be dictated by that low cell. This it’s pretty poor for a premium priced battery.

 

[RedFrame]

You set absorb at 14.2v, and absorb time at 2hrs and 0 tail current. Every time you discharge a bit, recharge back to spend time in absorb.

The cell at 3.58v it’s 99.99999% charged, while the 3.34v one, it can be anywhere from 30 to 70% charged. Your total capacity will be dictated by that low cell. This it’s pretty poor for a premium priced battery.

Thanks Raul,

I'll have a conversation with Ben at Sterling and report back what the outcome is...

Cheers
Red.

 

[RedFrame]

Thanks for the phone call t'other night Raul .

I thought I'd use the system over this weekend at the Swaffham meet and see what happens.

It seems that a couple of cycles on the batteries and setting Absorbtion to 14.2v has brought the cells into line, it's been dropping consistently and i now have 1 mv difference on one bank and 2 mv on the other.

Thanks to everyone for their help.

Cheers
Red.

 

[Raul]

Its going in the right direction, however, you want the same results close to 100% charge as well. At 70-80% cell drift is not a concern, but at 95% up is where you want to be balanced.

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