I want to make/upgrade solar charging of 3 batteries in my boat. Total solar panel power is 600W.
The battery types would be:
-Starting Battery (AGM, 90Ah) -1st priority
-Service 1 Battery (AGM, 100Ah) -2nd priority
-Service 2 (A/C) Battery (LiFePO4, 100Ah) -3rd priority
What would be the best connection and hardware used?
The easiest would be solar MPPT Controller with three separate outputs, but as I can see that one does not exist.
Cyrix is one way but I am afraid that cyrix is not precise enough to control charging of LiFePO4 battery.
Just put all the solar in battery 1 with a VSR between the 2 AGM and then a victron Orion 12v 12v 18 amp from the second AGM to the Lithium. I did have a setup like this in the past it worked well.
Thank You for the answer.
This what you said is good solution but I have non-essential hi load consumers (like A/C) on Lithium battery, and they need to be supplied most of it in real time from solar (600W).
In configuration like you suggested max real time load would be limited by DC - DC charger 18 amp.
Please can you tell me what is VSR exactly between battery 1 and 2? Not sure what that is?
Just something like a Blue Sea Systems Batterylink Automatic Charging Relay to combine them in parallel. They are the same chemistry so will be no problem. You can use a 100/50 MPPT for the solar and then up the DC-DC charger to the VICTRON Orion XS 12/12-50A DC-DC battery charger. With 600w of solar you might see 25-40amps max.
I would charge the Lithium from the solar, then use Orion XS to charge the AGMs from the lithium. I had this set up running very well on my boat for a season.
Thank You for answer. You said that you had it configured like that, at the moment when Orion XS is charging (has available power from Lithium side) and engine is running so there is charging from Alternator to Starting AGM, there is no problem for Orion XS output, it is handling this 14.4V from alternator well?
I think so. The Cyrix is Bi-Directional Voltage Sensing which means the house can charge the starter. The Blue sea also has this feature, * Optional Auxiliary Battery Priority connection shares the alternator charge with the Auxiliary battery longer when the engine is running to allow the use of auxiliary loads for an extended period of time.
The AGM’s will draw current from both charge sources. In this configuration the Orion XS knows nothing about the alternator. It is acting as a B2B charger.
My reason for charging the lithiums from solar is that lithiums charge very quickly right up to almost 100% SOC. AGMs rate of charge slows down the more they are charged. Lithiums will make better use of the limited hours of sunshine than AGMs.
Just to be 100% honest, when I was running this set up I had the older Orion TR, I have since upgraded to Orion XS and would highly recommend the XS over the TR.
Lithium does not like to be at 100% SOC. It’s best between 20- 80%. It is very difficult to get the logic correct because the voltage curve is so flat for lithium, AGM has a definite % based on voltage. AGM likes to be 100% all the time and I would expect they will be. Any current flowing through the system will be in pass thru and the AGM will take what they need and always be close to a high voltage. The charge current of the Orion XS will need to be adjusted just below the mean current of the system charge to stop microcycling the AGM. I guess either way there is no perfect solution to share one charging circuit.
I agree what you saying especially last sentence. There is no ideal solution…
It would be the best somehow to split system on 2 solar MPPT chargers, to separately charge Lithium and another MPPT to charge AGM-s. But I have only one set of solar panels. Do you know is there any way to connect one set of panels to 2 MPPT chargers?
If you have AC available, you could use something like a 5A NOCO charger with two outputs. If you’re avoiding alternator charging for the lithium battery, one option is to connect the solar panel directly to the lithium battery and use a DC-DC charger for the AGM battery, similar to how Martin set his up. It’s even possible to connect two MPPTs (Maximum Power Point Trackers) to a single panel.
Without knowing how much power the AGM battery needs to stay topped up, it’s hard to say whether this setup will work reliably. You could try using a 100/50 MPPT for the lithium battery and a smaller 75/10 MPPT for the AGM. Also, turning off the solar input with a breaker is a simple way to disconnect it when needed.
No, unfortunately I do not nave AC available all the time, it is a boat so I need to set up everything off grid.
This is very interesting and new idea to connect two MPPT chargers to single solar panel.
Do you know any configuration set like that and is it stabile?
This could be the best solution.
In theory each of two MPPT chargers could use power, how much it needs, from single solar in real time depending how empty his designated battery is.
I have played around with 2xMPPT one solar array. It does work but solar panels have very low capacitance so system performance in some conditions is not good. You can increase capacitance with a large capacitor or use a DC-DC converter but since you don’t have anything yet just get a DC-DC charger to go from the lithium to the AGM. They have a remote control and are also programmed on-off with voltage.
If you get a cerbo GX you can control the chargers based on logic with node-red. You could use the small charger in the morning to charge the AGM, 600w is only going to be doing about 100w until 8am the switch over the logic to use the larger MPPT for the lithium and then in the afternoon turn the large off and the small back on when there is only 100w of solar.
If you use victron components the possibilities are endless.
You could also look at a 500w multiplus compact and have AC and shore power charging. They are very affordable.
I’ve been experimenting with splitting power from a solar panel between two batteries using different charge controllers and converters. Here’s a summary of what I observed:
Initial Setup and Power Split:
I connected a 12V, 200W solar panel with an 18V 150W output into a Y splitter, distributing the output to two charge controllers and 2 batteries: a 100/20 and a 100/50.
In this configuration, the larger 100/50 controller consistently drew about 100W for one battery and the 100/20 50W for the second.
Buck-Boost Converters:
I added a 12V to 24V buck-boost converter to each charge controller input, both controllers started to draw power more equally, with each battery receiving around 70W.
Boost Converter Test:
Adding a boost converter to one controller led that controller to draw all the power, directing 140W to its battery, while the other received no power. Once the battery on the dominant controller reached absorption, the other controller took over and began charging its battery with the available power.
This experiment illustrates some key insights into how charge controllers prioritize power distribution, especially when using converters. The buck-boost converters helped achieve a more balanced distribution, which could be useful if you aim to charge both batteries evenly. However, using a boost converter alone seems to cause one controller to take priority, as it draws all available power until the battery reaches a specific charge state.
After more research and optimization I concluded this solution:
Solar Charger SmartSolar MPPT 150/60 TR connected to Lithium Service 2 Battery (LiFePO4, 100Ah) -3rd priority
Then between Lithium Service 2 and AGM Service 1 Battery (AGM, 100Ah) -2nd priority; install DC - DC Charger Orion XS DC-DC 12-12V 50A -to charge Service 2 Battery also from solar
Then between AGM Service 1 and AGM Starting Battery install Cyrix just to maintain Starting Battery on 100% on longer periods without driving engine
What do you think is this setup good?
I would like to have overview status of all batteries, but in this setup explained above I will not be able to see status of charge for Starting battery. (Lithium Service 2 - will be calculated and visible from SmartSolar Charger and AGM Service 1 will be calculated and visible from DC - DC Charger)
Any suggestion how to monitor that?
I was considering SmartShunt 500A to install on Starting Battery but I did not find many Shunt installation on starting battery probably because cranking current is very high.
So this last battery still remain to find some solution…
I think you need to do some more research. Your system is getting very complex. The one problem you will have is the DC-DC charger is non-isolated meaning the ground is shared. If there is a fault with the unit the full current from the Lithium can pass into the AGM. Isolated DC-DC chargers are preferred for different chemistry. You will need sufficient fuses and protection. A 100/50 fits in the palm of your hand, a 150/60 is the size of a dinner plate for 10 extra amps. Maybe consider an Argodiode isolator for the AGM batteries and charge from either the alternator or the DC-DC charger. This will keep them completely isolated. You can use a switch to combine them for emergency sharting and also use the Orion with settings that will allow charging for the lithium if required. You can monitor the AGM with a simple battery display based on voltage but the Lithium will require a shunt to measure current in and out to get the SOC.