John Frum
Tell me your problems
- Joined
- Nov 30, 2019
- Messages
- 15,233
20 volts is about 4 volts to low IMHO20V low voltage disconnect MINIMUM also applies for 24v LifePO4.
20 volts is about 4 volts to low IMHO20V low voltage disconnect MINIMUM also applies for 24v LifePO4.
Exactly. It is at least 3 volts too low!20V low voltage disconnect MINIMUM also applies for 24v LifePO4.
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.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?
Why not use a quality switch? Blue Sea as an example; https://www.bluesea.com/products/category/7/38/Switches/Rotary_Switches
Not for LifePO4. Search on it.20 volts is about 4 volts to low IMHO
I have.Not for LifePO4. Search on it.
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.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
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).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.
Less than 2 is empty for LifePO4.Not for LifePO4. Search on it.
"5.4 Standard DischargeLess than 2 is empty for LifePO4.
Do you have any evidence to support that claim?Less than 2 is empty for LifePO4.
I’ll post a few threads on Weds.Do you have any evidence to support that claim?
20V low voltage disconnect MINIMUM also applies for 24v LifePO4.
Less than 2 is empty for LifePO4.
So not 2.0 volts then?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
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.So not 2.0 volts then?
You have not presented anything close to compelling evidence for your claim.There was question about minimums and 2V is still absolute minimum.