Converter with adjustable charge current?

[rickst29]

ANL fuses become blown on the basis of high current, and do not actually see or "feel" any voltage differential associated with that current. They have no "frame ground" reference; it has no "shunt" comparator circuit, and they have virtually no internal resistance to maintain any differential across themselves.
It would theoretically be better to have a faster-responding fuse (than my cheap ANL pair), to protect the SCC in a lightning strike- but I could possibly pay a lot for such a fuse and still lose the SCC. ("Faster" might not be fast enough.)

(complex and skip-able info about my Solar follows)

Within my own TM, I have both an ANL fuse and a 5-pin switching Relay on the "Solar +" path from panels in Series, and an equally cheap ANL fuse on the PV "-" connector. My own Solar operating Voltage is around 85V, and I have no issues with frequent Voltage switching (from totally disconnected, up to about 85 volts) through the fuse and a 5-pin "switching Relay" on that fused wire path.

In my switching Relay, "Common" power lead is sent into the Solar controller. The Coil-Off, "Normally Closed" power lead comes from the genuine Solar Array, at up to about 85 volts, The "coil-activated" NO lead comes from the Bargman's "Trailer Battery Charge" connector, and the Power Relay Coil is activated (at ~12v) by a different "switching controller Relay".

That "switching controller Relay" detects Voltage well in excess of 24V coming in on the Bargeman "Trailer Battery Charge". (My "charge-the-TM from the Tow vehicle" operating Voltage is 36.0 Volts, when I activate the Voltage Booster from the Tow Vehicle Dashboard).

My point is that the power pins on the supposedly "low Voltage" 5-pin automotive relay and ANL fuse are frequently and almost instantly switched from an 85-Volt power source to total disconnect and also switched back (almost instantly) when I turn off the engine, or switch off the dashboard switch. Both of the fuses, along with the supposedly "low voltage" switching Relay, have suffered no ill effects from doing this several hundred times.

The Panels and ANL fuse also temporarily "see" the "PV+" line being operated at 36 Volts, at the beginning of the switch-back and before the SCC has re-tuned to the "genuine panel" Voltage. But the fuse still doesn't care. Since the CURRENT remains well below the rated value at all times, it doesn't blow up.

[ShrimpBurrito]

Hi Rick,

Thanks for the feedback. As you correctly stated, a fuse current rating determines the load at which the fuse will melt and break the circuit, however, as I understand it, the fuse VOLTAGE rating only comes into play AFTER the fuse melts, and preserves its ability to break the circuit after the fuse melts.

If the circuit voltage is in excess of the fuse voltage rating when the fuse melts, the circuit may not break because the high voltage is able to arc across the melted fuse. This obviously can quickly become a hazard of course, not only because the fuse has now failed to do its job and there is still an over-current scenario, but presumably the arcing itself could also contribute to a fire.

Most low current rated DC fuses and breakers I’ve found are limited to 36 or 48 volts.

Circuit breakers also have voltage ratings for the same reason.

Dave

[Bill]

Originally Posted by ShrimpBurrito

I'm connecting the panels in series, so at around 65V max, the voltage will exceed the rating of most DC breakers and fuses I've found. Larger fuses ... are rated for higher voltages, but I can't find a fuse small enough.....probably around 15A.

Dave -

Re current ratings: You are exactly right, and in agreement with discussions from major fuse manufacturers and suppliers. It is generally recommended that the current rating of a fuse should be 125-150% of the expected max current in the circuit, to avoid nuisance blowing.

It is worth noting that these same articles remind us that a fuse has a max voltage rating, as you noted in #10 above. The max voltage to be encountered in the circuit must be less than the fuse rating, but it is OK to use a fuse that is rated for a much higher voltage. It is also important to use a fuse that has an interruption spec stated in DC current, not AC current. AC is easier to interrupt because the current goes to zero 120 times per second, which helps to extinguish the arc. DC is harder to interrupt because the interruption has to be accomplished by the fuse itself, while handling the entire overload current.

I suggest that you check out a major component supplier such as McMaster-Carr or Digi-Key. The latter site has at least one fuse rated at 10 amps at 100 VDC, and dozens as soon as you go to 15 amps or more.

Bill

[ShrimpBurrito]

Great idea, Bill, in checking out other component suppliers. I had already checked McMaster, which didn't have anything of interest, but hadn't considered Digi-Key (or Mouser). I prefer a breaker, but I can't find a suitable one that is not ridiculously expensive or isn't surface mount, a fuse will do.

Dave

[ShrimpBurrito]

I called Northern Arizona Wind & Sun, and they said for installations where there is only only one "string" of panels (a series-connected group of panels), they don't use circuit protection between the panels and controller because there is such low current. The panels I'm using have a short-circuit current of 6.1A, which would be the case even with 3 panels in series, and I'm using 12 gauge wire between the panels and the controller (the panel pigtails are 14 gauge).

For such installs (at least those on RVs), they simply use a DC disconnect switch instead of circuit protection. The one they use, the IMO SI16-PEL64R-2, is rated up to 16A @ 800VDC (https://www.solar-electric.com/imo-s...ct-switch.html). In contrast, other disconnect switches I see, such as those made by Blue Sea, are only rated up to 36VDC or 48VDC, just like the DC fuses and breakers I've seen.

Dave

[ShrimpBurrito]

Originally Posted by rickst29

Even with PD, the charging Voltage in "Lithium mode" (14.6V) is a little high for LFP battery cells. In my slightly old model, The "Lithium" profile charges at 14.6V ALL THE TIME. At a slight cost (the need for slightly longer charging times), I have chosen to set the PD Converter Section to its "AGM" profile.

The "AGM" profile charges at a lower "Boost Voltage", and then drops to a lower but sufficient "Float Voltage" after a slightly-too-short time. But, when I'm in a hurry, for some unusual reason, I can always whack the "Charge Wizard Remote Pendant" button to force it back into another boost cycle. I've never actually bothered to do that, except for testing.

AGM is the correct "alternate" choice, because it doesn't have any LFP battery-killing "equalize" stages set into the profile.
- - -
The BMS in each of my two LFP batteries is allowed to accept the entire output of the PD, with the limit raised to 65A on each battery.

Rick -

Where did you find the AGM and lithium charge profiles for these PD retrofit units (like the PD4635V)? I see a profile on Best Converter's website (), but I presume is just for flooded lead acid, since it doesn't specify otherwise, and I don't see anything separate listed for AGM or lithium.

Battle Born recommends 14.4v for bulk and absorption phases, and 13.6v for float.

Many thanks,
Dave

[rickst29]

Originally Posted by ShrimpBurrito

Rick -

Where did you find the AGM and lithium charge profiles for these PD retrofit units (like the PD4635V)? I see a profile on Best Converter's website (), but I presume is just for flooded lead acid, since it doesn't specify otherwise, and I don't see anything separate listed for AGM or lithium.

Battle Born recommends 14.4v for bulk and absorption phases, and 13.6v for float.

Many thanks,
Dave

I called PD on the phone, in order to get that information.

[ShrimpBurrito]

Perfect, thanks, that was going to be my next step.

Dave

[ShrimpBurrito]

I talked with Progressive Dynamics today, and wanted to report the feedback I received as more people consider lithium.

I'm going to use Battle Born lithium iron phosphate batteries, and they recommend a bulk/absorption stage at 14.2-14.6v (with 14.4v being the mid-range sweet spot), and a float voltage of 13.6v or lower. With that in mind, Progressive offers 2 made-in-the-USA options for those looking to upgrade their converter to handle lithium.

1) For those with the old Parallax converters, the PD4600-series units (like the PD4635V) will fit in the same bay as the guts of the old one, allowing you to reuse the existing chassis. Most (but apparently not all) resellers also include a new fuse block which makes all DC circuits filtered, which is nice. With the old one, many were not filtered, and those that were simply used the battery as the filter. The lithium charge profile is single stage, with an output of 14.6v. That's it, so not ideal in my scenario. With the AGM/lead acid profile, there are 3 stages: bulk is 14.4v, absorption is 13.6v, and storage/float is 13.2v. That seems perfect, but the unit also does a 15 min equalization charge at 14.4v every 24 hours. So with lithium batteries, with a nearly non-existent rate of self-discharge, the equalization charge seems like a deal breaker if you intend to leave the unit plugged in all the time. Otherwise, if you plan to recharge when you get home and then unplug a day or two later, it seems fine.

2) The other option does not fit in the old Parallax chassis. For units with a serial number greater than A21244x (the "21" is the year, "244" is the day, and "x" is a letter referring to a specific model, so it varies), it it more consistent with Battle Born's recommendations, with a bulk voltage of 14.6v and a float/idle/storage voltage of 13.6v. They're working on making PD4600-series units that work like this, but COVID has made that challenging, and it's at least a year off.

Since it doesn't fit in the old Parallax bay, you'd have to pull out the converter guts of the Parallax unit and mount the new unit somewhere else, but close to where the old one was. Then, wire the DC output of the new unit to the existing DC distribution panel/fuse block, and also wire the AC input of the new unit to wherever AC came in to the old unit. So, a bit more complicated, particularly as to finding a new mount location that has suitable ventilation.

Dave

[rickst29]

Originally Posted by ShrimpBurrito

I talked with Progressive Dynamics today, .....and wanted to report the feedback I received as more people consider lithium.

1) For those with the old Parallax converters, the PD4600-series units (like the PD4635V) will fit in the same bay as the guts of the old one, allowing you to reuse the existing chassis. Most (but apparently not all) resellers also include a new fuse block which makes all DC circuits filtered, which is nice. With the old one, many were not filtered, and those that were simply used the battery as the filter.

Another issue with the original "power distribution fuse Board" is the extremely low power handling capability: Roughly 40A on each of the two "independent" fuse busses. The replacement Boards can handle well over 100A on the single shared bus.

Originally Posted by ShrimpBurrito

The lithium charge profile is single stage, with an output of 14.6v. That's it, so not ideal in my scenario. With the AGM/lead acid profile, there are 3 stages: bulk is 14.4v, absorption is 13.6v, and storage/float is 13.2v. That seems perfect, but the unit also does a 15 min equalization charge at 14.4v every 24 hours.

Dave, I think that you were misinformed (either the support rep didn't know/forgot, or got misled by you asking a general question about "a" lead acid charging profile). AFAIK, and I'm pretty certain about this - DIP switches are used to distinguish FLA from AGM/Gel batteries, and the latter switch position provides for 3-stage WITHOUT equalization. "Equalization" for FLA should also be higher, at or near 15 volts.

But it's possible that I'm wrong, and also possible that they have changed microcode subsequent to my earlier query. If the behavior is as you describe, with a very LOW "equalization voltage", it's utterly harmless. If equalization voltage is too much (above 14.6V), then each battery BMS will be called upon to invoke "over-voltage disconnect" every 24 hours. Different BMS models may or may not recover from temporary and moderate over-voltage situations automatically. It depends on the BMS.

Within my own battery packs - 14.4V is not defined as "over voltage", but anything exceeding 14.6V definitely invokes disconnection. IIRC, my own "WildKat" (a slightly customized version of the 4600) has a DIP switch position for Gel-AGM, and that'w where I have it.

Through the winter, my TM cord is plugged in continuously. The Wildkat sits within "storage/float", providing about 13.2 V mode, and my batteries sit at almost the same voltage. (A small difference exists, due to voltage drop within the BMS itself). If it's going up to 14.4V for a few minutes in the dead of night, I haven't witnessed those events. If it's going all the way up to 14.8V or 15.0V, then both BMS units are successful in disconnecting the "charge" circuit and recovering automatically. In any case, during mid-winter, charging is usually suppressed on the basis of temperature as well. (Temperature-based charge suppression in Daly "Smart" BMS works great, and it's definitely self-recovering when temperatures warm up.)

AGM/GEL has been a great setting for my LFP batteries. They're plugged in continuously, and this is my second winter with no "degradation" of battery performance having occurred after the first Winter - or during shorter intervals of TM storage within other seasons.