Living up to the hype Lithium Batteries

[Charliesmom]

After flipping the cut off switch, the BMS shows discharge with the start battery on the charger.
Gee, I should have thought about that …

[Lcavalletti]

I am very happy with my LifePO4 300 amp battery made by Powerqueen. Bought on amazon for under 900 bucks.

In the morning when the solar wakes up, , and with my fridge going 24/7, DC water heater and max fan that is on a thermastat, I get down to 88-92% then back to 100% daily with 400 watts of solar on the roof. In the summer witht he fan going full blast I probably get into the 90's in the vehicle.

Am I understanding from this thread, that i dont want to continue to trickle charge if the batteries are at 100%? This usually happens mid afternoon, I would have to manually kill the solar each day whcih woudl be a PIA.

I thought the BMS manages this and the battery will "float" in the 100 percent range.

Am I supposed to be doing something different?

I have all my alternative charging methods on a switch namely my DC to DC charger.

On a 6 day trip to Yosemite camping under the trees I did get down to about 40% charge, this was before I added another 200 watts to the roof.

With this much solar on a sunny day it seems like I have infinite power.

[Scalf77]

So looking at the list , the first two items are the heavy hitters. So no being in float won't kill the battery quickly. It may have a negative effect on your over all number of lifecycle, but not as big as the first two. So the point of the thread, is that you can try to limit some of the things that can have a negative impact on cycle life. When you are on a trip, and trying to maximize your solar input, it won't be the end of world.

More important would be just letting it sit out in your driveway, in the summer heat, float charging everyday.

You should view the BMS as a protection device, much like a circuit breaker. While it does do some important functions such as cell balancing and such. It does not control the charging devices other than shutting them down. The voltage settings, absorption time, etc. are controlled by the charging device. So the goal is to not let the BMS shut anything down.

-greg

[Scalf77]

I thought I would update this thread with my solution to some of the charging challenges with Lithium. For the most part I just monitored the system and adjusted while needed. I do generally charge to 100% SOC once a month, I usually don’t get much above 80%. Obviously, when camping and traveling I will charge as much as I can.
About a week ago someone posted on the Transit forum about trying to keep his Lithium battery between 40% and 60%. He was trying to do this with voltage, because he said his SOC meter got out sync. My take on it was to make sure you know why your SOC meter got out of sync. He has an all Victron system, Batteries, Lynx Smart BMS, Multiplus inverter/charger, SmartSolar MPPT and Cerbo. So, he had all the capabilities to do what he needed to do.

One member instructed him to use the Node-Red install on Cerbo’s Venus OS Large or install Home Assistant on a Raspberry PI. Of course, either of those things would get the job done, I just don’t it helped the OP. In any event it got me chasing down a couple of solutions.

Node-red is kind of a dashboard software, being that I am running the Venus OS large version, I put together a quick and dirty way for the OP to do so.




And add a little code to the turnoff functions.




I played around with Node-Red, I am not a fan connect blocks coding, so I put it to the side.

The Home Assistant solution also is probably very good, there are a few good threads on automation using it on the Transit Forum. I am not ready to go down that path, but I turned to my updated for Victron RV status program. The new program is running on a MeLE PCG02 Fanless Mini PC Stick Desktop Computer.



It uses vary little power (powered off a USB charging port), and is fanless, So I can just leave the unit on all the time when the van is parked. I can also connect over the wireless connection from my house. This is my first draft of the SOC charge control and Temp Charge control.



Here, you can see both the Mult and MPPT controller have separate SOC input, both are enabled (green button), along with temperature control. I changed the input as I was trying to get things charged before we get hot. You can see in the following picture that the Multplus was disable at 85% SOC. The green color means it met the trigger point.



I use two Cerbo relays to enable both the Multiplus and SmartSolar, although I could directly turn the devices on or off directly. The Temperature control allows me to charge between 34 and 86.

While not relatively useful to anyone without a Victron system, it does show things that can be done. I am not/was not a professional coder, so my coding style is pretty basic get it done. If anyone wanted some code snippets, let me know it written in C#

[Scalf77]

I guess the timing was good to write this code, We have a heatwave in the PDX area this week, twice now the software control has disable the solar charger as the battery temperature went to 85°F