Understanding solar panel charging for lithium batteries

[Moto GBR]

I have a Victron 100/30 - Installed a Craig Solar 300w with the leads provided into MPPT- Used Swift original wiring from Mppt to battery- I have added a Renogy 2000W Inverter using 40mm wires from battery.

 

[Moto GBR]

I am not at the MH today but will try over the weekend. TA

 

[Raul]

If you don't fancy my first suggestion how about this.
Did you connect it up in the right sequence?
Battery to solar controller then connect panels to controller.

It’s irrelevant at this stage, the controller clearly auto detected 12v system, and appears to be working fine. What we don’t know is, what distance, or cable size from controller to battery, could be a dodgy bad connection from controller to battery. The battery for some reason does not receive full voltage from the controller. It only reads 13.1v an£ bms acordin* to this voltage thinks is half charged.

 

[Raul]

I have a Victron 100/30 - Installed a Craig Solar 300w with the leads provided into MPPT- Used Swift original wiring from Mppt to battery- I have added a Renogy 2000W Inverter using 40mm wires from battery.

Not good, thats your problem, skinny wiring. Change the wires from controller to battery with 10mm2, and you will get full charge from solar.
Good mppt and good panel,
What is the distance from controller to battery?
The 2kw Renogy by should be wired with minimum 50mm2 for very short under one metre, or correct cable 70mm2.

 

[berni109]

Just a thought. Not trying to teach OP 'how to suck eggs' but sometimes the simple thing can get overlooked.

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[Moto GBR]

Just a thought. Not trying to teach OP 'how to suck eggs' but sometimes the simple thing can get overlooked.

Too true. I will give it ago at the weekend. Ta

 

[Moto GBR]

Not good, thats your problem, skinny wiring. Change the wires from controller to battery with 10mm2, and you will get full charge from solar.
Good mppt and good panel,
What is the distance from controller to battery?
The 2kw Renogy by should be wired with minimum 50mm2 for very short under one metre, or correct cable 70mm2.

I did think the original wiring was a bit flimsy. The distance is around 1.5m from battery. I will change it when I get a minute and see if it improves. The wires to Renogy were recommended by Simply Split Charge and came with a 250a fuse, the inverter is less than 500mm from battery. Ta

 

[Raul]

Please change that fuse to 150A or upgrade the wire. A 250a on a 40mm2 wire is to much.

 

[Moto GBR]

Please change that fuse to 150A or upgrade the wire. A 250a on a 40mm2 wire is to much.

ok, ta

 

[monzer]

If you're at the van this weekend I'd switch your solar off in the app, put a load on the batteries to be sure the battery is depleting (leave the TV and lights on for a good few hours) and then switch the solar back on to see what it is putting in.

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[Raul]

If you're at the van this weekend I'd switch your solar off in the app, put a load on the batteries to be sure the battery is depleting (leave the TV and lights on for a good few hours) and then switch the solar back on to see what it is putting in.

Please don’t do this. If controller has small 2.5mm wires, and the solar will push its best, it can exceed 20A towards the battery.
First check and replace the wires from controller to battery. There is a big voltage difference as it is, controller end is 13.5v and battery end is 13.1v. This suggests bad connection or small undersized wires.

 

[Moto GBR]

Ok, I have managed to route to new thicker cables from MPPT to Battery. Would it be ok to leave the original wires and run the new cables alongside them so we have 2 wires on both ends?

TA Steve

 

[TobyQuest]

Havent seen anyone mention this, but as far as I know when you switch to lithium you need to change the parameters, settings on the Victron charge controller. Lithium may operate and charge at different voltages etc to lead acid. In theory you shouldnt need this Fogstar app, just sounds like an unnecessary evil.

One test would be to thoroughly discharge the battery, then charge it as much as it will go and use the Victron app to see how many Watt Hours went into the battery. Then you'll know if you got 100ah (1200WH) or not.

 

[autorouter]

Would it be ok to leave the original wires and run the new cables alongside them so we have 2 wires on both ends?

Yes, that would be fine. What matters is the total cross-sectional area of copper, so the two cross-sectional areas add together. The only downsides to thicker cables are the weight and the expense. Electrically, more is better.

 

[treblid]

Please don’t do this. If controller has small 2.5mm wires, and the solar will push its best, it can exceed 20A towards the battery.
First check and replace the wires from controller to battery. There is a big voltage difference as it is, controller end is 13.5v and battery end is 13.1v. This suggests bad connection or small undersized wires.

Whilst I totally agree with the requirements for correct wire sizes, I don't think that is contributing to the voltage reading differences. The screen shots only show 0.2A or 0.5A charging current in post #22. You would have to have VERY thin wire to get that sort of voltage difference at 200mA.

I would believe the Victron voltage reading. Many BMS readings are inaccurate.

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[Moto GBR]

Havent seen anyone mention this, but as far as I know when you switch to lithium you need to change the parameters, settings on the Victron charge controller. Lithium may operate and charge at different voltages etc to lead acid. In theory you shouldnt need this Fogstar app, just sounds like an unnecessary evil.

One test would be to thoroughly discharge the battery, then charge it as much as it will go and use the Victron app to see how many Watt Hours went into the battery. Then you'll know if you got 100ah (1200WH) or not.

See post #10 TA S

 

[Raul]

Whilst I totally agree with the requirements for correct wire sizes, I don't think that is contributing to the voltage reading differences. The screen shots only show 0.2A or 0.5A charging current in post #22. You would have to have VERY thin wire to get that sort of voltage difference at 200mA.

I would believe the Victron voltage reading. Many BMS readings are inaccurate.

Quite possible, but, it’s not just the wire I mentioned, even a bad connection can drop the voltage over a distance, even at 0.2A. Without proper testing at both ends to have a voltage reference, it’s just a guess that fogstar reading is inaccurate.
I hope the OP keeps us informed and we all can learn from it.

 

[treblid]

Quite possible, but, it’s not just the wire I mentioned, even a bad connection can drop the voltage over a distance, even at 0.2A. Without proper testing at both ends to have a voltage reference, it’s just a guess that fogstar reading is inaccurate.
I hope the OP keeps us informed and we all can learn from it.

Bad connections don't provide linear voltage drops.

I agree with the proper testing. I would not be rewiring the system or physically changing anything without independent voltage measurements by a decent quality multimeter.

With all diagnostics the cause needs to be identified before wading in and changing things.

 

[Raul]

Bad connections don't provide linear voltage drops.

I agree with the proper testing. I would not be rewiring the system or physically changing anything without independent voltage measurements by a decent quality multimeter.

With all diagnostics the cause needs to be identified before wading in and changing things.

How do you know that is a linear drop? We only had a snippet of that instance, situation can change with load or charging rate.
I agree with the testing fully.

 

[treblid]

How do you know that is a linear drop? We only had a snippet of that instance, situation can change with load or charging rate.

From it the fact it was showing 1.6V difference at at 2.2A and 1.6V at 0.2A.

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[Raul]

From it the fact it was showing 1.6V difference at at 2.2A and 1.6V at 0.2A.

I see you confusion, the voltages that really matter are those posted on #22, the op was posting snippets taken all at different times, hence different values. The difference is 13.52 on controller, and 13.1v on the battery app. Those are taken at the same time.

 

[treblid]

OK, good point.

Let's look towards the next update from the OP.

 

[Moto GBR]

Update. I have taken the battery off the MH and have it on charge at home using a Lithium charger that I use for my motorbike batteries. As of this morning it has gone up to, See screenshot. It was put on charge nearly 40hrs ago and gone up to 62% from 51% with 174ah charge in it. Does it usually take this long to charge to full capacity?

 

[stevec]

40 hrs at half an amp is only 20Ah. So not surprised it’s taking that long.

 

[stevec]

Sorry looks like half an amp but see it’s 10 W. Less than an amp anyway.

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[Moto GBR]

Do you think I should change the charger for a more rapid charge?

 

[Brianmor]

Don't forget that your mh batteries are 20 to 30 times larger than your motorbike batteries are, so your battery charger might not have the output required for adequate charging for your lithiums

 

[ChrisL]

Update. I have taken the battery off the MH and have it on charge at home using a Lithium charger that I use for my motorbike batteries. As of this morning it has gone up to, See screenshot. It was put on charge nearly 40hrs ago and gone up to 62% from 51% with 174ah charge in it. Does it usually take this long to charge to full capacity?

View attachment 781655

13.3v and .8amp charge sounds like your charger thinks it's full?

 

[Moto GBR]

Any suggestions to get it fully charged? Or is it a case of waiting for the charger to charge it.

TA S

 

[Raul]

I think the charger is small, or not able to deliver a high enough voltage. At 13.3v, it should gobble amps in, all the way to about 13.8v, then it starts to tapper of the amps, then hold at 14.4v for about 10-15mins. If you can achieve that, you guarantee the battery is full.

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