question

javiangulo avatar image
javiangulo asked

Battery charging to SoC 100% then discharging with plenty of solar

Hi,

I have the following system:

  • Inverter: MultiPlus-II 48/5000/70-48
  • Solar charger: SmartSolar MPPT 250/100
  • Batteries: 2 x Meterboost MB48LI82 Li-ion NMC (82 Ah / 4.2 kWh each, 8.4 kWh total)
  • Battery monitor: SmartShunt 500A
  • Panels: 9 x Sunpower SPR-P6-405-BLK, 405W

The SmartSolar is configured with the recommended parameters as per the manufacturer, I've attached the configuration, the battery specs sheet and battery configuration manual. battery_specs.pdf battery_manual_configuration.pdf

The following pattern occurs daily:

  1. Early morning batteries are around 80% SoC
  2. Solar charges the battery at 1500-2000W, reaching 100% SoC in 2-3 hours
  3. Charger stays in 'float', discharging the battery, which goes down all day even with plenty of solar, getting to the 80% SoC mentioned before

Wouldn't it be expected that the battery keeps at 100%, with solar supplying the AC output of system while present, and starting to drop after solar is gone?

1709729466957.jpeg



screenshot-from-2024-03-06-12-09-15.png

1709724254910.png


battery chargingmeterboost
screenshot-from-2024-03-06-12-09-15.png (61.7 KiB)
1709724254910.png (63.9 KiB)
1709729466957.jpeg (96.1 KiB)
battery-specs.pdf (928.6 KiB)
battery-manual-configuration.pdf (5.0 MiB)
9 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

klim8skeptic avatar image klim8skeptic ♦ commented ·

@javiangulo The SmartSolar is configured with the recommended parameters as per the manufacturer.

Really?

Post your settings config, and the manufacturers specs.

1 Like 1 ·
matt1309 avatar image matt1309 klim8skeptic ♦ commented ·
I'd also add what's monitoring the SoC, smart shunt or a BMS?
1 Like 1 ·
javiangulo avatar image javiangulo matt1309 commented ·
@klim8skeptic @matt1309 edited with the missing information, thank you very much for checking it, very appreciated
0 Likes 0 ·
matt1309 avatar image matt1309 javiangulo commented ·

Hi @javiangulo

Is it just a case that float voltage is too low? I'm not familiar with Li-ion chemistry to advise on voltages but could it be it's hitting absorption and charging to 100. Then FLoat is too low so discharges to reach float voltage which drops you to 80%.

And then reabsorbs? My guess is float is not set correctly and needs to be higher. but check with manufacturer for specs/suggested float voltages. LiFePo4 I can suggested but Li-ion im less familiar sorry.



0 Likes 0 ·
nickdb avatar image nickdb ♦♦ matt1309 commented ·
It is a managed battery, it will set its CVL. In lithium charge and absorb are either the same value, or so close as to make little difference.

Any settings will be overridden by what the BMS sends, assuming it is visible and configured to be the BMS and monitor in the GX.

0 Likes 0 ·
javiangulo avatar image javiangulo nickdb ♦♦ commented ·
the BMS is not connected to the system, it is the SmartShunt acting as the battery monitor. the battery manual suggests connecting through VE Can port, perhaps this could help? or it wouldn't make much difference compared to the SmartShunt? However, the battery manual recommends setting those values regardless of connecting through the VE Can port..
0 Likes 0 ·
nickdb avatar image nickdb ♦♦ javiangulo commented ·
It is designed to be connected over CAN. Do that rather. It is the best way to connect a compatible battery and will provide reliable parameters and data to the GX. Shunts can be a royal pain, so unless it is actually required (incompatible or problematic BMS), it may just be causing your issues, or contributing to them.
0 Likes 0 ·
matt1309 avatar image matt1309 javiangulo commented ·

I personally prefer a shunt, In my head i like the logic of having the BMS be a separate secondary system with lower limits, than that of the solar. I dont tend to trust BMS manufacturers enough.

0 Likes 0 ·
nickdb avatar image nickdb ♦♦ matt1309 commented ·

Shunts are somewhat unintelligent devices, which are fine when paired with an equally unsophisticated battery, which has predictable behaviour.

A Li battery is far more emotionally unstable, much less tolerant of abuse and requires. constant management to keep the magic smoke inside the box.

The BMS will constantly shuffle what it needs to stay healthy and to raise a white flag if it has a problem. You really need that data to manage the charging and the discharging of the battery.

I have lost count of the number of people, myself included, who permanently tuned their shunts to try get it to work optimally in all conditions, and came to this community to plead for help.

Everything on the tested list works well. All batteries have some quirks, but it works best when the battery can steer the ship.

It was a wonderful day when I tossed my last BMV into the bin.

0 Likes 0 ·
1 Answer
Sebastião Beirão avatar image
Sebastião Beirão answered ·

Hi Javi,

I'm the Lead Engineer at MeterBoost. Your issue is because we had a small typo on our Quick Start Guide. The float voltage for the MPPT should be 57.5V and not 55.5V.

Nonetheless, and considering you have batteries with communication, as mentioned before we would advise you to connect the MtB GateWay to the Cerbo so that you have a more advanced system.

Please find bellow the most recent version of the Quick Start Guide.

MtB Quick Start Guide r2024-1.pdf


mtb-quick-start-guide-r2024-1.pdf (17.9 MiB)
1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

javiangulo avatar image javiangulo commented ·
system is working wonderfully after the configuration change, the battery reaches 100% at a slower pace when about 95%, then stays at 100% with solar increasing if the AC output requires as much. thank you!!
1 Like 1 ·