Help Configure System From My Existing Parts 24 volt

[pimpy]

I have these parts I want to use for a 24v setup.

1 - Victron SmartSolar MPPT 100/20
1 - ECO-WORTHY 120 Watts Solar Panel - VOC 21.6
1 - HQST 100 Watt poly - VOC 21.3
3 - Nissan Leaf Cells together to make one 24 volt battery
1 - Step down Converter 24V to 12V 40A 480W to power
1 - 12 volt Pure Sine Wave Converter



Will I be OK to connect the two panels in series and set my charge limit to 24.9, My max voltage cut off is set to 25.1. My low voltage disconnect is set to 19.5 ?

Any insight on charge controller settings would be helpful. Thanks in advance.

 

[Frank in Thailand]

Hi Pimpy,

I don't know Nissan leaf cells. are they 3.2 or 3.7 volts?

lifepo4 is friendly and have great charge and discharge tolerance
li-ion doesn't like that big window.

Google is your friend on the high and low.
without knowing how many cells you have and how it is setup, hard to answer.
besides, your BMS should be the master in charge and discharge

the inverter will never go below the 12v cut-off (10.5) as your stepdown will drain the 24 volt till empty.
unless you have additional special relais to cut the power.... you can have problems.

Not all BMS actually stop...

Personally,I would invest in 24v inverter, as it will stop at 21v. some you can even program.
For lifepo4 who have may discharge of 2.5, it can go down to 20v.
Nissan leaf cells, i don't know

 

[Sojourner1]

Maybe worded poorly but the bms should be the last line of protection for charging/ discharging for cell protection.

The settings on the PT or other charging devices ( if programmable) are the first line of protection.

 

[Frank in Thailand]

I agree.
BMS for keeping an eye on the individual cells (or parallel strings)
And if one falls below threshold, it should act.

Your charger should stop at the max for the battery pack.
And your inverter / discharger at the minimum.

Sadly not all cells charge or discharge at the same rate.

First line of defence is the 24 Volt Inverter stopping at 21 volt.

If you have 8 cells,and the cells have max discharge to 2.5 volt, 21 is good.

I don't know the Nissan leaf cells.
Nor if their low is 2.5 volt.

For this...
Google

 

[pimpy]

As listed above I have just 3 leaf batteries.

Spec below if new:

Nissan Leaf Battery Module Lithium Ion 0.5 kWh 8.3 v per module



500 watt hour per module
Each Module has 4 cells ( 2 in Series and 2 in Parallel )
8 volts
500 watts hour
66 amp hour
Dimensions are : 12 L x 9 w x 2 thickness
Weight is: 8 lb
Voltage sensing terminal M4 nut
Nominal Capacity 66Ah

Nominal voltage 7.5V

Maximum charge Voltage 8.3V

End of discharge voltage 5.0V

Maximum continuous charge current 130A

Maximum continuous discharge current

Each cell voltage should be less than 4.15V per cell

Each cell voltage should be more that 2.5V per cell

 

[pimpy]

I think I will buy a small 24v inverter https://amzn.to/2Wz1KoR and not use the 24v to 12v step down. I am not sure if it will have the proper low voltage shut off I need which would be 20v or 19.5v.

 

[Frank in Thailand]

Most inverters are made for lead acid, and that have 10.5 or 21 as low.

You should be safe there.

7.5volt nominal (is the voltage you should calculate with)
Is 3.7 volts = li-ion

For li-ion the charge tables are well available.
Personally I'll keep the charging voltage below 4.0 or better even 3.7
Takes a little longer for fully charged but we talk about solar use.
Then you have plenty of time

Your victron should be able to set the max charge voltage to 14.8 volt.

I hope you have BMS with the cells!

 

[onemorebattery]

Using two Leaf batteries (15v) on 12v spec is more feasible than using three Leaf batteries (22.5v) on 24v spec. The panels you have would run fine in parallel. For series I'd need to know the current to see the trade-off. Series current is limited to the lowest panel. Parallel voltage is limited to the lowest panel.

More info on using mixed panels.

Mixing solar panels – Dos and Don’ts • SOLAR POWER SECRETS

Mixing Solar Panels: Discover Now Dos and Dont's of Mixing the Same Types or Different Types of Solar Panels. Act Now to Save Your Money!

solarpanelsvenue.com