Charger Confusion - Multiple Charging Sources

[ssurabus]

Hi,

I've seen various posts touching on this topic, but not a definitive answer. Many of us have multiple charging sources. I'd like to add solar. Now the solar charger will be charging the batteries basically at all times. When I fire up the generator and turn on the charger, which presumably will have a higher charging capability than solar, I'd like to ensure that the charge from the solar panels doesn't prevent the generator/generator charger from producing its full output. In my mind, I think I'd like the solar charger only to be active when no other charging sources are present. I presume that I could do nothing and just live with the chargers being a little confused by each other. For example, when I start the generator and turn on the gen battery charger, it sees a higher voltage on the batteries due to the solar charger. I already have an example of this type of arrangement on the boat with 2 alternators wired to the same battery, but that one doesn't rub me the wrong way as the 2 alternators are "equal" charging sources. I don't really care which one might be working a little harder or longer than the other. In the case of solar vs the generator, I prefer that that the generator be dominant. Is this valid thinking? What are possibilities for implementation (i.e., have solar charger automatically turn itself off in the presence of other charging sources)

As an aside, the whole issue of multiple charging sources seems to be a bit of a rat's nest. At some point I may add a dc-dc charger from my start bank to the house in which case, yet a third charger will potentially be charging the house. However, with the solar charging source and the generator charging source, I'd probably just forget about the added complication of the dc-dc charger.

Thanks,
--Howie

 

[cafesport]

A lead acid or agm bank needs 3 stages for proper charging. A problem could potentially occur if the battery chargers all sense different voltages. Pretty easy to work around though if this occurs. FWIW we routinely use, solar, dc to dc and genny/shore power which runs two different make chargers simultaneously.

 

[ssurabus]

I didn't consider the possibility of the chargers reading different voltages from the same battery bank. Is that possible? Just to restate your response, you are running all your chargers simultaneously with no workarounds or added logic/isolators/switches etc. Is this correct? It is a path that I've considered.

It still seems to me that the 'artificially' high voltage of the bank due to the solar charger could prevent the higher amp charger run from the generator from kicking on - as you point out it might go to absortion or even float instead of bulk.

 

[Iggy]

Yes, one charger could see 14v and back down thinking the battery is charged. Using them at the same time, I would try to avoid it. But thats me.............

 

[ssurabus]

What's the 'best' way? I would like the solar charger to only be active when no other charging source is 'on' - and I would prefer not to have to press a button. I don't recall a setting like that on my house charger (run from genset/shore power). Do the solar chargers have anything like that built in?

 

[JDCAVE]

What's the 'best' way? I would like the solar charger to only be active when no other charging source is 'on' - and I would prefer not to have to press a button. I don't recall a setting like that on my house charger (run from genset/shore power). Do the solar chargers have anything like that built in?

I’d turn it off. If you are going to turn on your Genny, it’s best that the main charger, say a Magnum 2812 in our case, senses a lower voltage initially so it starts with the bulk charge. To ensure this is the case, first turn off your solar charger (flip off the breaker) then run an inverter load to drop the battery voltage below 12.6 or so. Even if your battery is significantly discharged, the solar panels can raise the surface voltage on the batteries above 12.7 volts. You might find that the Magnum will go to float charge straight away, which is a PITA. I would leave it off for the entire time you are running the Genny. It’s at this time, you want your water heater on and you are doing your laundry and water maker tasks. Give your Genny some honest exercise!

Jim

 

[ssurabus]

Thanks Jim. I agree with the everything you say, but was hoping not to have to manually throw the switch - or, more specifically, depend on my family to remember!

 

[JDCAVE]

I’m sure there is a way to program this but I have not done so. You can print out some point by point instructions that can make the steps pretty clear.

Jim

 

[NoRain]

What brand and type (MPPT hopefully) is your solar controller? What charger is the genset powering? And is that charger getting its SoC info from the same place as the solar controller? ie only one shunt in your system.

 

[ssurabus]

The solar panels and charger have not been purchased yet. I'm trying to get a feel for how the system will work and what type of charger to buy. The main charger (AC powered...genset/shore) is a Xantrex Freedom 2000 inverter. I don't really have SoC), I infer from voltage.

 

[ValhowellPower]

You are facing a real systems engineering problem. There are some easy ways to do this, but could be more costly. I run a very similar situation. We use a suite of Victron products. The BMV712 battery monitor talks to the solar chargers and the 120V charger (Victron Inverter Charger). If you have a smart external alternator regulator they can talk to the system as well through a Cerbo unit. The good side of all this is that all the systems see the same battery voltage, amperage, temperature and if needed, alternator amperage. No issues with systems fighting with one another. BTW, I am an ABYC certified electrician.

 

[ssurabus]

Sounds like a well thought out, unified system. While enticing, I'd probably just turn off the solar charger manually before going down path of really engineering the system as you have - and I don't have the capability to do so on my own. Just not worth it to me at this time. I can probably program the solar charger to turn-off at 13.4ish on my lifepo4 house bank. When the main charger comes on it always enters bulk for a minute or so which would kick off the solar charger. I think I'll try that. I just assumed that this was a common problem that people had solved in a fairly simple way. Maybe most just let the chargers fight it out. I think in my case, and probably many others, it will just work as long as I set the solar charger to turn off beneath the voltage where the big charger seems to always start. Thanks to everyone for help.

 

[Choices]

When you have separate chargers of different mfgs and design, you use the batteries voltage to charge the system.

With a single mtg design, the voltage is controlled via the dc capacitors and bus.

This allows power in from multiple devices with the ability to throttle the voltage charging rate at the device. These designs can also simultaneously back feed the AC system of the boat. This can only be done when one mfg is controlling system. Otherwise you have to tune it, and your going to be fighting it forever.

 

[dhays]

I have solar as well as inverter/charger that charge the house bank. When the charger is on powered either with shore power or genset, the solar will continue to also charge until the battery voltage hits the absorb voltage as set in the MPPT controller. Then the solar will no longer provide amps to the batteries as they are already at or above the absorb voltage. When the charger stops and the bank voltage drops, if the absorb time in the MPPT controller hasn't expired then the solar will continue to charge until its absorb timer is done, otherwise drop to float.

 

[Jeff F]

I can probably program the solar charger to turn-off at 13.4ish on my lifepo4 house bank. When the main charger comes on it always enters bulk for a minute or so which would kick off the solar charger. I think I'll try that. I just assumed that this was a common problem that people had solved in a fairly simple way.

I have 3 charging sources for my LiFePo house bank and have spent two years using and monitoring the system. I think you're trying to solve a non-existent problem.

When you turn on the charger it's not going to make a material difference whether the solar charging is on or off, unless the battery is very close to full charge, and then you don't care. And having solar on is not in any way going to throttle back the charger once it starts until you get to the target voltage, but by then you're at >95% SoC so it doesn't matter in my experience.

I wanted the opposite, to maximize solar at the expense of the other charging sources. So I set the solar to the battery specs, and set the bulk charge voltage on my other sources to 0.2v lower.

But none of this has any effect until the battery is very near full charge. Until then all the chargers contribute at their full capacity. They're not competing with one another. All I've done is dictate the order in which they drop out when the battery approaches full charge.

 

[guy with a boat]

I agree with Jeff F that there is likely no problem that needs to be solved. Our boat has 2 Outback inverter/chargers, 2 Victron Skylla chargers, 2 high-output alternators, and solar panels that are all connected and charge as needed. There is no management system to it other than slight differences in charging settings. They just figure it out and it works with no drama.

You could say that they fight it out but I think a better description is one source may loaf a bit if another source(s) is already doing the work. Regardless, they combine to provide all the charge output that the LFP bank needs and can accept.

 

[ksanders]

The bigger problem occurs when you are plugged into shore power.

There is a relay in your inverter/charger to automatically supply all the inverter loads via shore power.
Also your inverter charger if set to the same float voltage setting as the solar controller will result in very little solar production

 

[Jeff F]

I think battery type matters in this discussion. One of the great advantages of lithium is the high charge acceptance rate.

A lot of conventional wisdom on charging has been developed around LA battery needs and limitations, and much of it goes away with lithium.

 

[motion30]

I agree with Jeff f as well I've charged with solar multiple battery chargers and the alternator from the motor all at one time. And it seems to make no difference they all do what they were designed to do without interference from one another. And yes with the voltage approaches 14.4 they start the throttle back like any particular charging sure she would do on its own

 

[RobertLeatch]

The bigger problem occurs when you are plugged into shore power.

There is a relay in your inverter/charger to automatically supply all the inverter loads via shore power.
Also your inverter charger if set to the same float voltage setting as the solar controller will result in very little solar production

Have just been playing around with a cool feature of the Victron Multiplus inverter/charger called Ignore AC In that can mitigate this. It essentially allows you to bypass (turnoff) the AC In relay under defined conditions. I'm using load and/or battery SoC so that if the load is low (say less than 1000w) and the SoC is high (say > 80%) then it will be in inverter mode and not be using shore power. For me, on most days on shore power, it seems to result in solar being the only active charging source for the last 20% but still allow for shore power to be available when a high AC load appears (stove, kettle etc).