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solaruser125 asked

Smartsolar 100/50 Goal Zero 25 amp Fast Charger as PV input

I'm trying to use a Goal Zero 25 am Fast charger as the PV input to charged 3 connected 100amp AGM batteries connected in parallel. For some reason, when I use the Goal Zero fast charger, the only thing that shows up on the victron app under Solar is 15.24V (voltage) and 0.0 A (current) and under battery it says 12.70V (voltage) and 0.0A (Current).

Why isn't this setup working?

I tested the same setup but connected a 100 W solar panel to the PV input and the app showed 62 W from solar and 59 W charging the AGMs.

Thanks for any help here.


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Justin Cook answered ·

For an MPPT to initialize and start permitting throughput, it needs to see battery voltage +5v at the PV input, so if your batteries are at 12.70v, the MPPT won't initialize until it sees >17.70v at the PV input. Since your GoalZero battery charger is generally charging at around 14.4v (apparently 15.24 at fast-charge), your setup won't work unless you have <10.24v on your batteries, which is obviously a bit too late.

If you're set on using a charger through your MPPT, get a 24v version. That way you can put around 26.5v to the PV side, your MPPT will initialize and step down the voltage and step up the amperage just like it does when it's connected to actual PVs. (I know this works because I have this setup on my test bench for the express purpose of testing MPPTs).

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solaruser125 avatar image solaruser125 commented ·

Thank you for the explanation. Can you recommend a 24V charger? Thank you again.

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solaruser125 avatar image solaruser125 commented ·

One more question. if what you are saying about the +5v at the PV is correct, then why was it charging when i plugged in a single 100W panel. I know that the battery was at like 12.5 when the MPPT was charging. Thanks.

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Justin Cook avatar image Justin Cook ♦♦ solaruser125 commented ·

@solaruser125, if you're looking for a good portable plug-in 24v charger, I definitely recommend the Victron Smart IP67 charger: https://www.victronenergy.com/chargers/blue-smart-ip67-charger-waterproof

orrrrr the Victron Smart IP65 charger https://www.victronenergy.com/chargers/blue-smart-ip65-charger

I fundamentally like the IP65 better because it's a bit more customizable... the IP67 has pre-wired ring terminals at the battery side whereas the IP65 has interchangeable end connectors with quick-disconnect fittings, which is super convenient particularly if you plan to use it for other things than just hooking into your MPPT. The IP65 is the one I use on my test bench. That being said, the IP67 version has a higher amperage; up to 12A in the 24v version as opposed to 8A in 24v on the IP65. Your call on that.

The reason the MPPT started charging when you hooked up your solar panel is because your PV panel is outputting ~19.5v... VOC should be somewhere between 20.5vDC and 22vDC (typically), which means on average you'll be seeing around 18.5-20vDC depending on the day, the time, and the angle of the panel in relation to the sun; this voltage meets the +5v requirement of the MPPT. Remember that you have high voltage and low amperage coming from your panel; the MPPT turns that into low voltage and high amperage to charge your battery.

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solaruser125 avatar image solaruser125 Justin Cook ♦♦ commented ·

Justin. Thanks. I purchased the IP67 charger and connected it to the MPPT. It's charging the battery. The IP67 shows 27.31V at 4.0A and in Float stage. The MPPT shows 12.88V at 7.8A going to the AGMs so that's great. My questions is threefold:

Why does the IP67 say the charge status is in Float but the MPPT says the charge status is in Bluk? Shouldn't they be the same charge status?

Does the IP67 connection through the MPPT affect its accuracy as to the charge status: bulk, absorption, float, storage? In other words, can the IP67 still measure the battery so that it deploys the right charging algorithm?

Is it dangerous to leave the IP67 charging overnight/indefinitely through the MPPT to AGMs? The IP67 says that it can intelligently charge and put it in a "Storage" mode, but I'm worried about keeping it plugged in over many days/weeks.

Thanks so much for your help here as I'm a total newbie just trying to learn stuff.



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solaruser125 avatar image solaruser125 Justin Cook ♦♦ commented ·

Justin, one other thing I don't quite understand about the IP67 is that it has been going from bulk to absorption to float, then back to bulk, to absorption to float again as if it is cycling through these stages.

The IP67 shows that the 12V AGMs (3 in parallel) were reading 12.85V (absorption), then 12.88V (Float), but then back to Bulk stage at 12. 98V. Why is this happening? Am I somehow damaging the batteries?

Thanks.

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Justin Cook avatar image Justin Cook ♦♦ solaruser125 commented ·

@solaruser125, that's an interesting condition that I haven't observed in my IP65 version that I'm using on my test bench; that being said, you can go into the settings via Bluetooth and turn off the charger's charge profile. Ideally you want it (as long as it's connected through the MPPT) to output a relatively steady charging voltage, and let the MPPT decide when to go into bulk/absorption/float, etc. The MPPT is constantly varying the load that it's putting on the charger (which is what it's supposed to do when hooked up to PV, thus the name Maximum Power Point Tracking), which the charger is interpreting as state of battery charge and thus changing its charge rate; in turn, the MPPT is interpreting the variance in charge rate as "clouds over the sun" and varying its load to get the most current out of the charger, which the charger sees as a change in battery state, etc etc. Basically an intelligent charging loop.

You're not damaging your batteries; what's charging your batteries is the MPPT, your IP67 is only acting as a power supply and doesn't see your batteries at all. Thus, for maximum efficiency, you should go into the settings of the IP67 and set it for a flat output, or as flat as possible, so the MPPT doesn't need to keep cycling around looking for the most efficient current setting.

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solaruser125 avatar image solaruser125 Justin Cook ♦♦ commented ·

Justin, on the IP67, there is no way to "turn off" the charger's charge profile. In the settings gear icon there are only 5 charge options: Normal, Normal + recondition, High, High + recondition and Li-ion. You can also toggle the charge current from 4A to 12A.

Also on the 100/50 MPPT, I've never seen it change from Bulk to anything else while the PV had solar panels or the IP67, even though I know from the AGM's volts that it is close to 90% or more charged. For example, I got a screen shot from the MPPT (while the IP67 is in the PV) that says Battery Voltage is 12.88V, Current is 7.8A and State is Bulk. It never seems to change from Bulk to anything else, which is what I would expect based on your explanation that the MPPT is doing the charging.

Do you think I have a defective MPPT?

Also, you are saying basically ignore anything that the IP67 is saying except Volts and Amps as the MPPT is what I should be paying attention to?

Thanks.

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