Have smartsolar mppt charging my vehicle’s cranking AGM battery. Would like to add a LifePO4 for a bit more reserve for a fridge. Can I add an Orion on the load side of the MPPT to charge a lifePo4 battery? Or is there a smarter way to achieve this?
asked
AGM from SmartSolar Mppt plus LifePo4 with Orion on load side?
Load output is limited, depending on the MPPT model. I guess you're going to connect the fridge to the new LiFePO4 directly and feed the combo from the Orion. Just make sure the Orion is set up properly. And that the load settings for cut off voltage are right for your starter battery.
Would it be wiser to connect Orion and MPPT in parallel to the starter battery?
The fridge barely sips power so not worried about needing to charge second battery too quickly. Thought the load side data from the MPPT could be interesting because it would show in context with inbound solar. Don’t have an Orion yet, so unsure what info is in there.
More common is to connect mppt to leisure battery and trickle charge the starter form leisure. If engine charging leisure needed, add another Orion for that. But this is expensive. The thing to avoid is allow loads like the fridge to run the starter battery down, leaving you with a vehicle that won't start. The load output of an MPPT issue intended to protect the battery it is charging, i.e. avoid the battery being flattened.
Starter has two charging needs. After engine start, maintenancewhen long periods between starts. After engine start, the vehicle alternator brings it back to fully charged very quickly. Maintenance charge is very low current.
My earlier answer was intended to give a practical solution with minimum change.
You should be using a LiFePO4 with either internal or external BMS. Battery protection comes from the BMS so protection via load output is not needed and it's now become a nice to have for separate reporting. The voltage change during lithium discharge is low and and you may find accurate protection setup tricky.
Connecting the lithium and starter together isn't an option due to the different chemistries and cgpharging needs. And if you don't switch the fridge to the lithium battery, you might as well not install it. There's another factor not discussed. Starter batteries are not intended for loads like fridges. Running a fridge will shorten its life considerably.
Given all this what I would do is:
Check if your mppt load will run the fridge, bearing in mind that compressor fridges have very high startup currents.
Switch fridge wiring to either lithium or MPPT load or lithium.
Configure mppt for lithium.
Install a low power Orion to charge starter battery from lithium/solar. Set the ouput (battery) voltages so that absorption is no more than .1V over starter battery float to avoid overcharging. Use engine on detection to switch on when mppt kicks in.
