question

loomin avatar image
loomin asked

Charge Source Priority?

Hey Everyone,


I am in the middle of a van conversion. I've got solar, shore power and alternator for charge sources.

I was curious about how the devices in my charging system decide which source to charge from and if they are smart enough to realize that the system is already being charged by another device already. I don't want to jam too much current into my batteries.


My current setup is:

-200AH (100AHx2) AGM batteries (wired in parallel) max charge current is 60A

-310W Solar Panels

-Victron BMV-712

-Victron SmartSolar MPPT 100/30 Smart

-Victron Orion TR smart 12/12-30 Charger

-Kisae IC-122055 AC Charger/Inverter (55A Charge) - Shore Power

https://www.kisaepower.com/wp-content/uploads/2016/07/Inverter-Charger_datasheet_high_frequency.pdf

-Victron Smart Battery Protect - I was thinking of using this to turn off all DC loads with the push of a button.


Scenario 1: If I am plugged into shore power and the sun comes out and the MPPT decides to start charging at the same time, I could see a very high charge current (80A) with both devices trying to charge at the same time, correct? Or would the MPPT somehow detect the charge voltage of my Inverter/Charger and not start?


Scenario 2:

The van is charging from the MPPT and I decide to go for a drive. I start the engine and the Orion decides to start charging. Technically this scenario wouldn't exceed the max charge amps of the battery but I am just using it as an example.


Am I overthinking this?



MPPT ControllersBMV Battery Monitororion-tr smartBattery Protect
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4 Answers
JohnC avatar image
JohnC answered ·

Hi @Loomin

Overthinking is for people who care for what they do. Welcome.. :)

An all-Victron (and higher end) setup could do what you want, but the kit you have will communicate only by the charge V it detects. Just sayin. But it's not a big deal.

Please check that 60A max is real. That's 0.3C into 200Ah of batts, and probably impossible to achieve anyway in practice with AGM's, at least for more than seconds/minutes. They'll self-limit, show high (target) V, and the charger(s) will back off.

Scenario 1: Even if you'd just turned on the shore power at sunup, the solar will come on slowly, and by the time it can produce anything useful the batts are partly done, and one/both chargers will back off.

Scenario 2: Same story.

The 60A limit does seem unrealistic though, and in practice would likely never be reached.

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loomin avatar image
loomin answered ·

Hey @JohnC


Thanks for clarifying this for me. The spec sheet for a single battery says max charge current is 30A (but recommended is 10-15A each. Since they are in parallel, max charge current becomes 60A am I right?

I just wanted to make sure I don't melt anything when I get everything connected.


Thanks again!


Chris





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JohnC avatar image JohnC ♦ commented ·

Yeh, your figures are right, and make much more sense when you show the whole story.

You won't melt anything down, provided of course your wiring and fittings are up to par. If your inverter/charger can't be charge limited then that's a shame (you know what to get next time). Experience will help as you learn to manage your system.

And just in case you haven't seen these: https://www.victronenergy.com/blog/2019/06/18/the-victron-van-install/

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf


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adric avatar image
adric answered ·

Hi John,

I have a very similar question to Loomin posted here,

https://community.victronenergy.com/questions/48180/how-to-setup-multiple-chargers-connecting-simultan.html

but I received no answer. I guess I can now use your reply to Loomin as a reference, which is great.

However, it would be great to understand how all the three charging devices could be prioritized via the Victron connect app. Would there be a way to do this?

Also, looking at the Victron Van install link, I cannot make sense of the highlighted in yellow section below.

As it seems that the AC/DC Charger flow could be reaching the Battery Protect Out, which I thought was wrong and could cause the BP to fail and catch fire, by reversing the flow.

Shouldn't the AC/DC Charger be connected on the Input side of the BP, like the MPPT and Starter are?

I would appreciate you feedback on both these questions.

Thank you in advance,

Adri


29-04-2020-12-11-23-pm.jpg (304.1 KiB)
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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ commented ·

Hi @adric,

There are only other charge sources connected to the top battery protect in that diagram.

The starter battery+alternator, which is connected to the buck+boost charger, which is also on that BatteryProtect, does not allow current to flow back to the starter battery.

So there is no load that would draw the current the wrong direction through the Battery Protect.

The other side of that Battery Protect is connected to the DC bus, from there, if there was any surplus current from the Inverter/Charger, it would flow to the batteries (and not back to the BatteryProtect).


The AC/DC charger in this example is a MultiPlus Inverter/Charger, so it can be both a charge source, and a load. It is never appropriate to connect a BatteryProtect between an Inverter/Charger and the battery. There are other ways to protect the battery from an Inverter/Charger.

If it was JUST an AC/DC charger, like a Skylla, then it should be on the same side as the MPPTs like you say.



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JohnC avatar image JohnC ♦ commented ·

Hi @adric

In a simple system the only real way of prioritizing charge sources is by setting the charge V targets at different levels on each piece of kit. So the higher settings will get priority once the lower-set ones have reached their targets. A coarseish type of approach, but effective. Then there's the on-off isolators, again effective.

What I don't like to see is a full batt Absorb cycle being applied more than once-a-day by secondary kit.

In a higher level system, like with a GX box, there are more comprehensive options like DVCC, assistants, gen-start relays, even ESS, etc. We've come a long way in the last few years, and Perfection is still elusive. Victron are still working hard on that.. :)

I'm not sure what your issue is with that BatteryProtect. It appears to be set up with remote control from a BMV to shut off both charge sources when not needed. Neither of the upstream mppt's nor BuckBoost would accept reverse current.

Just heading out to start my generator. Foul solar day, but we need the rain here. So yes, the 'isolator switch' in use..


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adric avatar image
adric answered ·

Thank you Guy and John for your feedback, it is greatly appreciated. Regards, Adri

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