aangel
New Member
- Joined
- Aug 12, 2020
- Messages
- 97
I'm in the market for an MPPT charge controller that dumps the power to an alternate circuit when the batteries reach a certain charge state. I will have ~1200W from the solar panels and LiPo batteries. This is for a vehicle mount but posting here seems to make more sense since it deals with heating hot water. I'm currently looking at this Camco water heater conversion kit (my current unit uses propane) but there are others on the market.
Looking through some marketing pages, the following units say they can do this (not exhaustive)
• Victron
• Outback
• Xantrex
• Morningstar
However, this fellow makes the case that his Outback units are taking power from the batteries and not directly from the solar panels thus are unnecessarily wearing them down due to micro-cycling on the top end. Thinking about it, I can see that this design was likely the easiest for the manufacturers but it doesn't seem optimal to me. Over time it seems that this causes avoidable excess wear on the batteries.
Instead, he says, don't use this charge controller feature. Avoid going to the battery via the controller and divert the DC power directly from the solar panels before it gets to the charge controller. Looking through his channel I can't find the follow up video he suggested he might make that would detail his solution. He mentioned two relays.
On the other hand, there may be other features of the controller that make it worthwhile; it might be that, on balance, this design is actually the best one.
Making things more interesting, someone commented with the following opinion:
Here are my questions:
Is this a real problem? If it's real, is it a significant problem? The answer might be no to both questions.
If it is a real and significant problem, it seems to me there are two ways of resolving this:
Soliciting thoughts on all the above.
Looking through some marketing pages, the following units say they can do this (not exhaustive)
• Victron
• Outback
• Xantrex
• Morningstar
However, this fellow makes the case that his Outback units are taking power from the batteries and not directly from the solar panels thus are unnecessarily wearing them down due to micro-cycling on the top end. Thinking about it, I can see that this design was likely the easiest for the manufacturers but it doesn't seem optimal to me. Over time it seems that this causes avoidable excess wear on the batteries.
Instead, he says, don't use this charge controller feature. Avoid going to the battery via the controller and divert the DC power directly from the solar panels before it gets to the charge controller. Looking through his channel I can't find the follow up video he suggested he might make that would detail his solution. He mentioned two relays.
On the other hand, there may be other features of the controller that make it worthwhile; it might be that, on balance, this design is actually the best one.
Making things more interesting, someone commented with the following opinion:
It isn't actually cycling the batteries. What is happening is that the charge controller is directly connected to your dump load when your batteries are fully charged. What you see as the voltage dropping slightly is the charger not being able to adjust voltage fast enough for the load. Since it knows that it can't raise the voltage due to over charging the batteries it goes on the safe side and ups the amperage causing a sag in voltage but when the amperage is available from solar it's not taking anything from the battery until the load is too much for the solar input.
Here are my questions:
Is this a real problem? If it's real, is it a significant problem? The answer might be no to both questions.
If it is a real and significant problem, it seems to me there are two ways of resolving this:
- find a charge controller with a different design; this is attractive from an installation standpoint
- use a charge controller that raises a signal when the batteries are full or empty and use additional equipment (a signal relay) that is between the panels and the charge controller (these seem to be common). What would be a simple setup to divert before the charge controller?
Soliciting thoughts on all the above.
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