wildebus
Full Member
- Messages
- 6,435
This may be of interest to some people who wonder why their solar does not seem to be producing as much power as it should despite it being a sunny day, etc? If you think of solar harvesting as a water pipe and your battery as a bath, your solar controller is a ballcock 
To illustrate this, here is my setup.
The Solar is feeding both Lithium and Lead Batteries here and is harvesting 234W from the panels, and excluding DC loads, and device losses, all that power is going into the Lithium, which is only half charged, and nothing into the Lead (it is the way the Hybrid Lithium/Lead works, but that is another story - the key thing is the Lithium is getting over 200W of charge.)
In the Solar Water pipe analogy, plenty of room in the bath to take the water...
If I remove the half-empty Lithium from the charging system, the amount of harvesting drops pretty dramatically. The panels, controller or weather has not changed (this screenshot was seconds after the first one), but we are getting just about half the power into the battery.
The reason for this is that even though the Lead Battery needs charging (which can be seen by it taking 7.40A), the characteristic of Lead Acid technology (even Lead Carbon ones like these) is that as the battery gets closer to fully charged, the amount of charge current it will accept gets smaller and smaller.
Back to the water pipe and bath analogy, think of it as having to turn the tap down to avoid water splashing over the side as the water gets to the top.
So what this illustrates, I think, is that even though you may have a solar setup capable of say 570W (in my case) and the weather is permitting upto 234W maximium (here at 10AM in Scotland), the system may just not be able to accept that much power as there is just nowhere for it to go (even though your batteries may still be in need of some charging!)
That could be down to the battery nearing full charge or even fully charged (Lead OR Lithium), so to check how well your solar setup is doing, you MUST make room for that water (power) to come through the ballcock (controller).
Just because the Solar Controller says "145W" doesn't mean that is all it can produce and you have been short-changed. It may also mean 145W is all your van can take in at that time.
If you want to check what it might be able to do at any particular time, you need to either make sure there is room in the battery, which means having room in the Lithium, or possibly having a Lead Battery under 70% charge to take a full current - or more easily, get some loads going to increase the demand - so turn on lights, TV, fan, inverter, etc and see what the Solar jumps up to.
To illustrate this, here is my setup.
The Solar is feeding both Lithium and Lead Batteries here and is harvesting 234W from the panels, and excluding DC loads, and device losses, all that power is going into the Lithium, which is only half charged, and nothing into the Lead (it is the way the Hybrid Lithium/Lead works, but that is another story - the key thing is the Lithium is getting over 200W of charge.)
In the Solar Water pipe analogy, plenty of room in the bath to take the water...
If I remove the half-empty Lithium from the charging system, the amount of harvesting drops pretty dramatically. The panels, controller or weather has not changed (this screenshot was seconds after the first one), but we are getting just about half the power into the battery.
The reason for this is that even though the Lead Battery needs charging (which can be seen by it taking 7.40A), the characteristic of Lead Acid technology (even Lead Carbon ones like these) is that as the battery gets closer to fully charged, the amount of charge current it will accept gets smaller and smaller.
Back to the water pipe and bath analogy, think of it as having to turn the tap down to avoid water splashing over the side as the water gets to the top.
So what this illustrates, I think, is that even though you may have a solar setup capable of say 570W (in my case) and the weather is permitting upto 234W maximium (here at 10AM in Scotland), the system may just not be able to accept that much power as there is just nowhere for it to go (even though your batteries may still be in need of some charging!)
That could be down to the battery nearing full charge or even fully charged (Lead OR Lithium), so to check how well your solar setup is doing, you MUST make room for that water (power) to come through the ballcock (controller).
Just because the Solar Controller says "145W" doesn't mean that is all it can produce and you have been short-changed. It may also mean 145W is all your van can take in at that time.
If you want to check what it might be able to do at any particular time, you need to either make sure there is room in the battery, which means having room in the Lithium, or possibly having a Lead Battery under 70% charge to take a full current - or more easily, get some loads going to increase the demand - so turn on lights, TV, fan, inverter, etc and see what the Solar jumps up to.
