question

I am also running BMS 712

@fallguy1000

You can use DVCC to control the system wide current that is the mppts and multiplus charging the system.

But the Orions cannot be controlled by the Cerbo.

Are your battteries rated at C10? If so then it is their capacity divided by 10 that is roughly what you want to charge/discharge at.

What does the manufacturer specifications actually say though. That should give you good direction there.

East Penn says max charge rate is 30% of Ahr rating. AHr rating is 92 per battery, but system is just 24v, so still 92Ahr at 24v. So, max amperage is 27 which means even the Multiplus has been overcharging. I need to do some homework on the cerbo. I printed the manual and gonna go reset cerbo.

How do I deal with the Orions? Typically, the Multiplus would be off when the Orions are, so really when they are on; need to limit the solar..

Max charge rate is max, and for agm that max is high, will shorten battery life. You need to balance charge rate with time available to charge. The C10 rate @Alexandra quoted is a normal balance between charging quickly and shortening battery life. (C10 means 1/10th of battery capacity, 9.2A here, not the 30A from 1/3 capacity)

There's no charge rate setting on the Orions, they're voltage based. There is another potential problem here. The Orions will take pretty much full power from your alternators, which can lead to overheating/burning out the alternators. If you never let the batteries get low, possibly OK, but...

Your system is very low on battery capacity. Suggest you rewire the orions to be switched manually, not automatically, and then only use for short periods. And set up dvcc in the multi as suggested, with a max charge current of 9A. This will control the mppt, if the two are connected with a VE direct cable. You may have to increase this current if you have heavy loads when on shore power.

Background, all the chargers use a 3 stage charging system, stage 1 is max current, during this battery voltage increases, until it gets to the absorption setting, then during the second stage, absorption, voltage is maintained and the current drops as the batteries become charged. Batteries control the charge rate. Once this has gone long enough, chargers switch to float. Keep batteries charged. So as voltage rises under charging conditions, the batteries limit the charge rate. Unless you run your batteries low, the amount of over current won't be as bad as you're thinking.

I suppose one solution would be to rightsize the battery bank and add another pair of batteries. Then the system would handle a theoretical 54amps which would be within the Orions and Solar maximums.

Couldn't Victron fix this with a simple step of cycling the Orion? For example, the Orion could produce current for say 60 seconds and then be off for 2 minutes. So the bulk time would be 60 seconds and then the charging would not start for a time? It already has a delayed start timer for charging the start battery. Seems like using a timer would make it so their Orion devices would be less likely to fry stuff.

...versus starting back up based on low voltage as is now

With your current setup how much charging current does your AGM bank receive from the Orions when the bank is depleted?

I ask this because lead acid batteries (AGM, FLA and GEL) all have a definite charge acceptance rate (CAR). Batteries are rated many ways but the most convenient and familiar is the 20 hour rate designated C20. A battery with a C20 = 100Ahr when subjected to a load of 100Ahr/20A = 5A will reach termination voltage (10.7VDC) in 20 hours. The CAR for LA batteries is between 0.15C and 0.20C (plus or minus). You don't have an overcharging problem caused by too much charging current.

I am going to go get two more batteries and get to 182 Ah, so 10% would be 18.2A. I would never run both 12/24-15 Orions, so one would deliver the 15 amps and keep the bank safe. The problem is if the bank is depleted, I would be pulling 30 amps from a 33-35amp alternator for too long and probably cook them. The Orion needs to cycle or I have to spend money on a Buck Boost.