I am getting a high voltage ripple error and can’t figure out why.
All new Victron, MPPT 250/185, Multiplus II 5000/48, oversized cables, good connections, LiTime 48V LifePo4 batteries, no grid connection. I checked the MPPT and it was configured for GEL so I changed that, along with parameters, and rebooted thinking I had found the problem . Nope
The MPPT charger stays in Bulk mode even when the battery exceeds float voltage (54). Then keeps charging. Once it exceeds 55.5 V, I get the error and A/C output from the Multiplus flickers my lighting. Is there battery info to be configured in the Multiplus? If the battery voltage stays under 55, then everything runs perfectly.
Yes, the Multiplus needs to be configured for its absorption voltage. What may be happening is your battery BMS is disconnecting in one or more of the batteries due to an over-voltage cell. I recommend you keep your absorption voltages low (like 55.2 V) until you understand the state of your batteries balancing. You can increase it later. This is for both the MPPTs and for the Multiplus.
You will need a MK3-USB adaptor and Victron Connect on a desktop to configure the Multiplus
If you have a Cerbo GX, you should also enable DVCC and set a maximum charge current so you do not overcharge your batteries.
If not, the sum of the MPPT max current (85A) and the whatever the Multiplus is set to for max charge current will go into the batteries, so you might want to lower the max charge current depending on how many batteries you have.
Much appreciated. (4) 24V 200ah in parallel and series for 48V @ 400ah. I’ll hook my computer up and config the Multiplus. But I’m surprised that it might help as the MPPT is doing the charging given no grid connection. Thanks again and wish me luck.
If you never plan to connect to the grid for charging, the Multiplus parameters will not matter. I gave general advice not knowing your configuration, so if others see this they will know what to do as well. It’s still a good idea to configure it so if you ever want to charge from grid or generator, (from a week of full clouds, for example), it will do the right thing for your batteries. Otherwise, the default settings may be problematic.
I assume you are ONLY seeing the high-ripple when batteries are fully charged. If you see it at other times as well, then you may have other issues.
How are you measuring SoC? Do you have a shunt, or are you relying on the battery BMS to tell you? BMSes are notoriously inaccurate.
The MPPT should be configured using expert mode. Here are my conservative settings for a 250/70:
The idea is to prevent the batteries from hitting a cell over-votage, but still give them enough voltage to let the internal balancer work. With these settings, when your batteries get to 55.2V, the MPPT will go into absorption mode for 30 minutes and hold the voltage (enough time for some balancing). After that, it will go into float mode and hold the voltage at 54V.
Do you have the bluetooth version of the batteries? If so, you can monitor the cell voltages for each when you get over 55.0V and see how imbalanced the cells are. There’s no point in looking at the cell balance below 55V, they will always look balanced. You can always attempt to adjust the absorption voltage higher later once you have it working without problems.
Another potential problem is the series-parallel wiring of the 24V batteries.
There is no way to keep the series batteries in balance. Over time, they will drift apart in voltage.
I’m not aware of a battery balancer for 2x 24V to 48V batteries. Victron’s is for 12V batteries.
Thanks again. I’m taking soc from the Victron shunt 1000 (through the cerbo). Yes, I only see the ripple when fully/over charged. I’ll lower the absorption voltage and see if it helps. I think that ultimately it’s a battery issue (fact that they’re LiTime and in series). I’ll eventually get a stack of EG4-LLs.
Good choice on the shunt. All batteries have cell balancing issues, and there are no BMSes out there that really do the right thing (well, Victron probably does )
I’ve got a stack of EG4-LL v1s, they aren’t any better for balancing.
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