thegoogler
New Member
- Joined
- Apr 15, 2021
- Messages
- 108
I've got about 2 months of usage on my DIY 280Ah LiFePO4 battery. After a 5 week trip, I decided the Renogy Rover Elite 40A wasn't sufficiently configurable, as I found myself regularly adjusting the absorption voltage in order to either speed up charging when I'd been in the shade a few days, or to cut off charging when I started the morning off at ~90%. So I'm selling it and I've installed a Victron SmartSolar MPPT 100/50 along with a SmartSense monitor.
If I just wanted to charge my LFP to 100% this would be easy. But my goal is to stop around 90% SoC, according to both the Overkill BMS and my Simarine Pico. Note that while I have 280Ah, most days when I'm in the camper I'm only using maybe 10% of the battery capacity, and when the camper is parked between trips I'm using maybe 1%. But when living in the camper I might go 4 days in the shade and be down to 50-60% capacity by the end of the trip. Also note that I have 350W of solar currently available, though I've never seen it deliver more than about 17A at peak (which is barely above 0.05C).
The Victron LiFePO4 default seems to be too aggressive for me, so I've used the LFP settings as the baseline and then I'm customizing from there.
Victron defaults
absorption: 14.2V
float: 13.5V
equalization: disabled
My initial settings:
absorption: 14.2V
float: 13.5V
equalization: disabled
re-bulk voltage offset: 0.10V
absorption duration: adaptive
max absorption time: 2 hours
tail current: 2A
I installed this yesterday. My SoC was at 100%. Upon enabling the device, the Victron went into bulk mode and was applying between 0.5A and 1.2A, depending on the amount of sun (I was in the shade). So immediately I'm confused because the Amps being applied are less than the tail current. So lots of questions for those with some experience with Victron, and I'm particularly interested in feedback from anyone who has successfully used Victron to limit SoC to <100%:
1. try to bulk charge at a high voltage (ideally 14.4V) when the battery is depleted to as to get the highest # Amps possible back into the battery
2. as I get close to full (90%+) I want to decrease the target voltage (or just plain stop charging) so as not to fully cycle the battery
I'm really interested in feedback and any experience others have had accomplishing the same, especially with Victron.
If I just wanted to charge my LFP to 100% this would be easy. But my goal is to stop around 90% SoC, according to both the Overkill BMS and my Simarine Pico. Note that while I have 280Ah, most days when I'm in the camper I'm only using maybe 10% of the battery capacity, and when the camper is parked between trips I'm using maybe 1%. But when living in the camper I might go 4 days in the shade and be down to 50-60% capacity by the end of the trip. Also note that I have 350W of solar currently available, though I've never seen it deliver more than about 17A at peak (which is barely above 0.05C).
The Victron LiFePO4 default seems to be too aggressive for me, so I've used the LFP settings as the baseline and then I'm customizing from there.
Victron defaults
absorption: 14.2V
float: 13.5V
equalization: disabled
My initial settings:
absorption: 14.2V
float: 13.5V
equalization: disabled
re-bulk voltage offset: 0.10V
absorption duration: adaptive
max absorption time: 2 hours
tail current: 2A
I installed this yesterday. My SoC was at 100%. Upon enabling the device, the Victron went into bulk mode and was applying between 0.5A and 1.2A, depending on the amount of sun (I was in the shade). So immediately I'm confused because the Amps being applied are less than the tail current. So lots of questions for those with some experience with Victron, and I'm particularly interested in feedback from anyone who has successfully used Victron to limit SoC to <100%:
- Is bulk charging just "constant current @ absorption voltage"?
- Is there no direct way to control any of the bulk charging parameters? I assume the Victron went into bulk mode because it was able to apply constant current. But SoC should be 100%. Battery voltage was showing ~13.8 with current being applied
- Should I decrease the absorption voltage? With the Renogy I ended up adjusting it between 13.6V and 14.4V depending on the battery SoC each morning. With the Renogy I found if I set it to a lower voltage (i.e. 13.6V) the # of Amps was lower too (i.e. 3A) but as I increased it I could get up to ~17A @ 14.4V delivered to the battery. So if I'd been in the shade for days and was down ~100Ah I would set it to 14.2 or 14.4V when driving to ensure I got a sufficient recharge, but if I was parked in the sun and only using ~20-30Ah/day I'd leave it at 13.6V or maybe 13.8V and let it "trickle" charge.
- Should I change the max absorption time and/or tail current value? I feel like in my limited testing and research tail current should actually be set based on absorption voltage, not based on battery size.
1. try to bulk charge at a high voltage (ideally 14.4V) when the battery is depleted to as to get the highest # Amps possible back into the battery
2. as I get close to full (90%+) I want to decrease the target voltage (or just plain stop charging) so as not to fully cycle the battery
I'm really interested in feedback and any experience others have had accomplishing the same, especially with Victron.