diy solar

diy solar

Simple design for using an inverter to power your 50 amp service RV using a $30 Change over switch

Here is a link to the manual. It has the exact same control configuration as the 24V/2000W unit


The remote won't let you power down the inverter if the switch on the inverter is ON, have to make sure to keep that switch OFF. The logic of this function is screwed up in my opinion.

"2.5.7 Remote Control Apart from the switch panel on the front (or top) of the inverter, an extra switch panel connected to the RJ11 port at the DC side of the inverter thru a standard telephone cable can also control the operation of the inverter (sold separately Part # PICGLFREMOTE). If an extra switch panel is connected to the inverter via “remote control port”, together with the panel on the inverter case, the two panels will be connected and operated in parallel. Whichever first switches from “Off” to “Power saver off” or “Power saver on”, it will power the inverter on. If the commands from the two panels conflict, the inverter will operate according to the following priority: Power saver on> Power saver off> Power off Only when both panels are turned to the “Unit Off” position, will the inverter be powered off. The max length of the cable is 60 feet. "
 
jvbutter01 said:
Thanks scott for your layout of the switch. My issue is remembering to switch over. I tend to not always remember things. I'm thinking automatic is better...
@HaldorEE what model do you use?
Click to expand...
If you are in a standard I modified RV you still will have to flip off on and off the circuitbreaker that powers your charger converter depending on if you are running from generator or battery/inverter. The switch takes care of all that and is cheaper than an automatic setup. Another possible advantage is by starting your generator and letting it run for a minute while you walk over to the flip the switch gives it time to warm up before you put a big load on it. Likewise when you shut down- you flip the switch and let the generator run for a minute to cool off before turning it off will help it to last longer.

The transfer switch between shorepower and the internal generator in my rig is the factory unit that came with the RV. I do not know what the brand is. The manual change over switch was one I got from Amazon In the link above.
 
Last edited:
TedH said:
Not for LifePO4. Search on it.
Click to expand...
I have.
2.5 is dead empty and I don't want to get any closer than ~2.90 volts per cell.

1600815730284.png

How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries –...

By: Rob Beckers You have just sold your first-born into slavery, remortgaged the house, and bought yourself a lithium-ion battery! Now you want to know how to take care of your precious new purchase: How to best charge lithium-iron batteries, how to discharge them, and how to get the maximum...
www.solacity.com www.solacity.com
 
smoothJoey said:
I have.
2.5 is dead empty and I don't want to get any closer than ~2.90 volts per cell.

View attachment 23452

How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries –...

By: Rob Beckers You have just sold your first-born into slavery, remortgaged the house, and bought yourself a lithium-ion battery! Now you want to know how to take care of your precious new purchase: How to best charge lithium-iron batteries, how to discharge them, and how to get the maximum...
www.solacity.com www.solacity.com
Click to expand...
What he said. The batteries are the most expensive part of the system and I really don't want to have multi thousand dollar opps.
 
Further to my previous statement.
I want layers of protection.
inverter cutoff set to 24.0 volts
battery protect for dc loads 23.8 volts
bms low pack 23.6 volts
bms low cell 2.90 volts ~= 23.2 volts for the pack

Consider this scenario...
My inverter is pulling ~200 amps as the cells get into the low knee.
Things snowball very quickly as the voltage starts dropping the amperage goes up at a compensatory rate.
 
smoothJoey said:
Further to my previous statement.
I want layers of protection.
inverter cutoff set to 24.0 volts
battery protect for dc loads 23.8 volts
bms low pack 23.6 volts
bms low cell 2.90 volts ~= 23.2 volts for the pack

Consider this scenario...
My inverter is pulling ~200 amps as the cells get into the low knee.
Things happen very quickly because as the voltage starts dropping the amperage goes up at a compensatory rate.
Click to expand...
We think very much alike. In my opinion the role of a BMS is to protect against unbalanced cells and as a very last gasp protection if something else breaks. If the BMS ever disconnects then something bad has happened (just like if a fuse has blown).
 
Last edited:
TedH said:
20V low voltage disconnect MINIMUM also applies for 24v LifePO4.
Click to expand...

As an absolute minimum, yes.

But the absolute minimum is usually set at the BMS not the inverter, and then most people use a value above absolute minimum even for the BMS (but this is a personal choice I suppose).

TedH said:
Less than 2 is empty for LifePO4.
Click to expand...

This is old info as far as I know.

I have not come across any cell manufacturer datasheet from the last 5ish years that defines 0% SOC as less than 2.5vpc, or allows discharging below 2.5vpc at normal temperatures.

I have seen some cheap non-configurable BMSes that still use 2.2vpc or 2.1vpc as the cutoff points.

As to what Will currently recommends--which is just one (fairly experienced) person's recommendation--2.675 to 3 VPC (21.4-24 volts for an 8S battery).
 
*I did find one manufacturer that still used 2.3VPC as absolute minimum cutoff as of 2018 (Higee 152Ah)

(EVE, CALB, Sinoply, and GBS and CATL list 2.5v as absolute minimum VPC)
 
Sharing the parameters for my CALB LifePO4 cells:

Operating Conditions

  • Maximum Charge Current: 100A
  • Maximum Constant Discharging Current: 200A
  • Charging Cut-off Voltage: 3.65V
  • Discharging Cut-off Voltage: 2.5V (8 cells @ 2.5V = 20V)
  • SOC Usage Window: 10% ~ 90% - I will configure my BMS using this range. 10% is close to the 2.5V minimum per cell
  • Charging Temperature: 0 C ~ 45 C
  • Discharging Temperature: -20 C ~ 55 C
  • Storage Temperature within 1 month: -20 C ~ 45 C
  • Storage Temperature within 1 year: -20 C ~ 20 C
 
TedH said:
Sharing the parameters for my CALB LifePO4 cells:

Operating Conditions

  • Maximum Charge Current: 100A
  • Maximum Constant Discharging Current: 200A
  • Charging Cut-off Voltage: 3.65V
  • Discharging Cut-off Voltage: 2.5V (8 cells @ 2.5V = 20V)
  • SOC Usage Window: 10% ~ 90% - I will configure my BMS using this range. 10% is close to the 2.5V minimum per cell
  • Charging Temperature: 0 C ~ 45 C
  • Discharging Temperature: -20 C ~ 55 C
  • Storage Temperature within 1 month: -20 C ~ 45 C
  • Storage Temperature within 1 year: -20 C ~ 20 C
Click to expand...
So not 2.0 volts then?
 
smoothJoey said:
So not 2.0 volts then?
Click to expand...
At the Inverter, Low Voltage Cut-off will still be 10V (2.5V per cell). That was the original discussion regarding Inverter Cut off at 10V or 10.1V for a 12V system. There was question about minimums and 2V is still absolute minimum. However, for longevity, 2.5V (approx. 90% discharged) is my target.
 
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