question

wisey avatar image

Bluesolar 75/50 gets to float voltage too early.

Seen some with similar problem but not seeing many answers. Please help. Trying to improve SOC during daylight hours. Have Smartshunt onto 600Ah Lithium. Po4. Come the afternoon, solar producing close to 50Amps. The voltage moves increasingly higher and then goes into Float. Float set at 14.2v. Trying to keep voltage low and Amps high to increase SOC. Is the charger regulating the max. Output by increasing the charge voltage? When I turn the charger off for a few minutes, voltage regulates to below 13.8 and charger goes into Bulk mode with higher charging current obviously. Running VE Bluetooth dongle and Smartshunt networked

voltagefloatamps
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5 Answers
wisey avatar image
wisey answered ·

Any replies as to why the Amps consumed meter is not reversing (and increasing SOC) albeit there is sufficient energy available to do so?

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Normally errors in SOC are nailed down to 3 things.

Incorrect shunt wiring > loads and chargers must not bypass the shunt, the battery side of the shunt goes directly to the battery.

Badly programmed BMV's that wont synchronize reliably. Youtube tutorial.

Undersized arrays or excessive loads on the system.


You can tell just by looking at your mppt's history if the battery has been fully charged. Eg....

screenshot-2020-02-03-21-36-43-375.jpeg



wisey avatar image
wisey answered ·

Thanks for the assistance. Still battling with the SOC meter not returning to a higher percentage, despite having plentiful power available from the PV array to do so. Please see the attached screenshots. See the energy charged versus discharged figures. Any further suggedtions? 16965F9B-E60C-42DB-BBF8-5EDDBB57AFC2.png48CC4D57-A412-46EA-964B-B2174BBFC3FA.png


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You have watched the Youtube tutorial??

Your history screenshot shows that the mppt has reached float stage for the last 8 days, but only has an absorption stage on 2 days.

Voltages for absorp-float/absorp duration for the MPPT?

Post your BMV settings....

bmv-settings.png

bmv-settings.png (279.6 KiB)
Yes, watched the you tube tutorial. Thx. Sorry, battling with this website a bit too. We have been having sun-filled days. Are close to the Equator so as you will note, there is sufficient power available, its just not transferring to the batteries. Thx for you assistance
scubadoo avatar image
scubadoo answered ·

Your battery must be very different to our now 7 year old 4 cell Sinopoly 300Ah LiFePO4 motorhome battery or there is some setup anomaly.

We also have a Victron 75/50 solar controller, Victron 500A Smartshunt and a Juntek battery monitor.

Our battery is always at 100% SOC on our 2 battery monitors when the battery terminals reach 14.1V. The solar controller is currently set to 2 minutes absorption. They accept no more energy.

Float is purposely set low at 13.30V and that permanently maintains around 90-95% SOC for the rest of the day. The next days solar bulk charge or a five minute 80A alternator driving charge soon restore those few percent.

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Thx for the contribution. Yes, I have three 200Ah Ampere Time LifePo4. They have been in for three months. We are using approx. 15 to 20Amps every hour. So the draw is pretty high. I intend fitting another 300Ah in a few months, But I still do think the Bulk charge period of the charger could be increased/lengthened to increase the SOC. It's almost as if the charger has a timer. By 14h00ish I begin to see it switching to Float and the battery SOC is still way low. Scubadoo would you mind posting a screen shot of your BMV settings?
wisey avatar image
wisey answered ·

Yes, I watched the Youtube tutorial, most of my settings are based on the battery manufacturer specifications. I have adjusted the absorption and float voltages to suit the Bulk phase - as I say to take advantage of available PV power during the day. Please see screenshot of my BMV. Also, thank you again for all your time and help. IMG_4F4F1A1DAAB9-1.jpg


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I have adjusted the absorption and float voltages to suit the Bulk phase - as I say to take advantage of available PV power during the day.

I would be more comfortable knowing your mppt settings.

The mppt will supply the loads during absorp and float phase, while holding/increasing the battery SOC, as long as there is enough sun to hold the battery voltage steady.

Scooby has set his battery float at 13.3v, and that maintains SOC at 90-95% until the sun goes down.

I have set my float voltage at 13.4v, and that maintains 98-99% SOC until the sun goes down.


wkirby avatar image
wkirby answered ·

I'm not sure what you mean by "trying to keep Voltage low and Amps high to increase SOC"?
When in Bulk mode the charge will charge with the maximum power that it can get from the PV array. The actual battery Voltage is irrelevant at this charging stage, the maximum charge current for the PV power available will be delivered by the MPPT.
The Absorb stage is triggered when the set Absorb Voltage limit is reached. When in this stage the MPPT supplies the maximum current that is required to aintain that particular Voltage limit - any more current would raise the battery Voltage and possibly damage it. That is the reason foor the Voltage limit. The more energy that the battery absorbs, the less current is required to hold the Absorb Voltage and so the the current gradually drops down.
After some time, either fixed or variable, depending upon your settings, the Float stage will be enforced. This is similar to the Absorb stage but with a lower Voltage limit. Charge current will be minimal but that's fine because the battery is full, so no more charge power is required other than to satisfy loads.

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Thank you for your help.


I mean the following:


1) The SOC meter remains below 80 percent despite there being much power available (and not used). I cannot get the SOC higher. SOC percentage has been tweaked to find an average. Still, I do not believe these new batteries are fully charged - the consumed Ah meter is never fully reversed to even close to what has been consumed.


2) Yes, the battery voltage is raised to 14.2 (Float level) by lunchtime and one would assume they are fully charged at that Voltage, but the Amps consumed during the night hours are never replaced (or reversed) sufficiently, because the MPPT switches to Float when it reaches 14.2V and supplies related current to maintain Float level.


3) When "forced to Bulk' by disabling charger and allowing Voltage to drop below 14.2, the charger obviously switches to Bulk and provides higher amperage. But of course for just a short period. The Ah consumed meter remains un-reversed and the SOC unchanged. My assumption for the installation of an SOC meter is to monitor the Amps consumed (and returned) as the Voltmeter alone, does not reflect true SOC.

Hence my statement to keep the Voltage supplied lower and the Amps higher.

If that is not possible.

My question is:

1) If the Float voltage on the LifePo4's I have is 14.2V, what would you set the Absorption voltage to, to increase the SOC. Would this help? As have monitored "Absorption" by setting to 14.0V but do not see the Ah consumed meter reversing. Please bare in mind - the period of maximum charge (13h00 to 16h00) is not being utilised because the charger is switching to either Float or Absorption phase as the Voltage reaches 14.0 (Absorption) or 14.2V (Float).

I do understand LifePo4 does not require recharging to 100 percent but would like to see higher SOC for when on passage, as the load during the night hours increases and would like full capacity available.

Currently drawing 300Ah in a 24 hour cycle.

Set to increase battery capacity to 900Ah (by adding another 300Ah) in three months time.

Have 1200W solar with two MPPT chargers. One being a 40Amp WRND, the other the 75/50 Bluesolar

Thanks for assisting


the charger is switching to either Float or Absorption phase as the Voltage reaches 14.0 (Absorption) or 14.2V (Float).

You seem to have mixed the float and absorption voltages around.

There is also differences as what WRND and Victron call STAGE 2 charging. Stage 2 = Absorption = Boost.

3-stage-charge-2.png

3-stage-charge-1.jpg3-stage-charge-2.png

Please check that both charge controllers are set up the same to the battery manufacturers recommendations.

WRND manual. Victron manual.

3-stage-charge-1.jpg (191.0 KiB)
3-stage-charge-2.png (634.9 KiB)