Boards Frying From 14 volt Solar Charging?

[John in Santa Cruz]

my PD4655Li with the jumper set to Lithium mode outputs 14.6V when the battery is fully charged., and this is not adjustable. The Victron stuff can be programmed. 13.6 or 13.8V max will charge a LFP battery to better than 95% which is good enough, and if I could, I would turn the PD4655 down to 13.8 or so.

this 90 minute or so voltage/amp graph shows the PD4655 being switched on with a 90% charged pair of SOK 206AH, initially the charging voltage is around 13.5 volts at 40 amps or so, as the batteries approach 100%, the voltage goes up to 14.3 as teh current drops to 11 amps, then the SOK battery BMS kicks in, and those two big spikes are cell equalization (per SOK engineering, I showed them this graph and a complete description of what I was doing, and they gave me a very succinct response, thanking me for supplying sufficient info that they could answer in one pass).



the PD4655 is actually trying to output its full 14.6V during this charge cycle, the reason the smartshunt on the batteries only sees 13.5 or whatever is due to wiring and connector resistive losses (at 50A, it doesn't take much to drop 1V).

[John in Santa Cruz]

p.s. I'm mildly annoyed that the SmartShunt doesn't record internally, you have to leave VictronConnect running and connected on your tablet/phone to get graphs like this, and even then, it only graphs the last 2 hours.

The SmartShunt *does* keep this data without the app running...

[Centex]

Originally Posted by bborzell

...Am I missing something in assuming that if 14+V from solar panels are suspected of harming appliance circuit boards, then the same might be said for DC-DC chargers?

Methinks you're on the correct path of understanding.

If you have a lithium battery system, and thus any charging device (solar controller, DC-to-DC vehicle interface, and/or a shore-power charger) which is programmed to allow 14.xx volts charging as a part of its output profile, then the attendant risk is present to voltage-sensitive load devices (appliances, etc) on your DC distribution system whenever any of those charging devices (or the battery alone) is delivering that higher voltage. Volts is volts no matter what the source.

[alanmalk]

Originally Posted by John in Santa Cruz

my PD4655Li with the jumper set to Lithium mode outputs 14.6V when the battery is fully charged., and this is not adjustable. The Victron stuff can be programmed. 13.6 or 13.8V max will charge a LFP battery to better than 95% which is good enough, and if I could, I would turn the PD4655 down to 13.8 or so.
...

You might want to consider a Schottky diode in series at the output terminal of the PD4655Li. A 0.6 volt drop is my solution to half the world's problem.

[tdf-texas]

Originally Posted by bborzell

Given that any potentially vulnerable circuit board is at risk only when a switch has been thrown that allows 12V power to reach it, and that most folks are taught to turn off water heaters and furnaces while towing, perhaps those towing conditions are protective, though not necessarily thought out.

Am I missing something in assuming that if 14+V from solar panels are suspected of harming appliance circuit boards, then the same might be said for DC-DC chargers?

Uh, Bob. The furnace, hot water heater, etc. control boards are powered by the DC supply all the time - not just when you turn them on. Even when the hot water heater is running on propane, the igniter board is still seeing the battery voltage. The only time they are powered down is when their fuse in the WFCO is pulled or blown.

So when you are towing and the charge voltage is up above 14 volts, that is the voltage all the devices are being exposed to.

Yes, all the electrical stuff in our trailers should have been designed for at least 15 volts - but they're not. So we have to either live with it when they fail, keep spares for when they do, or modify our DC system so they don't see voltages that high.

The trailer equipment manufacturers figure that enough of them will survive past the warranty period that it makes it cost effective to not redesign them for longer life. Think of it this way - if the RV stuff lasts too long, they don't get to sell replacements as much. Hurts the bottom line.

[bborzell]

Originally Posted by tdf-texas

Uh, Bob. The furnace, hot water heater, etc. control boards are powered by the DC supply all the time - not just when you turn them on. Even when the hot water heater is running on propane, the igniter board is still seeing the battery voltage. The only time they are powered down is when their fuse in the WFCO is pulled or blown.

So when you are towing and the charge voltage is up above 14 volts, that is the voltage all the devices are being exposed to.

So much for that theory.

The official response from ETI was that only the early Maxxfan boards were susceptible to failure due to higher voltage. Given that both the water heater and furnace specs show a <14V upper input range, it would appear that the boards will eventually succumb to death from some large number of small voltage insults. Maybe the fact that many RVs sit doing nothing for so much of the year, gives a time to failure range that is only slightly longer than the time it takes for infrequently used rigs to be sold.

[tdf-texas]

Originally Posted by bborzell

So much for that theory.

The official response from ETI was that only the early Maxxfan boards were susceptible to failure due to higher voltage. Given that both the water heater and furnace specs show a <14V upper input range, it would appear that the boards will eventually succumb to death from some large number of small voltage insults. Maybe the fact that many RVs sit doing nothing for so much of the year, gives a time to failure range that is only slightly longer than the time it takes for infrequently used rigs to be sold.

That and the voltage tolerance of these boards vary. Some fail shortly after purchase and others last for years. The <14V rating is to protect the manufacturer - oh, your voltage is too high so the board's warranty is void.

If the boards failed more often, there would be such an outcry that the manufacturers would have to redesign. That's what happened to Maxxfan and why they came out with the C series boards that are now rated for 15V.
https://www.etrailer.com/Accessories...ll-description
https://pantherrvproducts.com/10c21276k/

[John in Santa Cruz]

Originally Posted by alanmalk

You might want to consider a Schottky diode in series at the output terminal of the PD4655Li. A 0.6 volt drop is my solution to half the world's problem.

do those exist that can handle 50 amp loads? 50 amps at 0.6 volts means that diode will be a 30 watt heater. hmm, this one drops between 0.91 to 0.76 volts at 40A/leg, 80A total if both legs are paralleled. http://www.smc-diodes.com/propdf/STW...97%20REV.A.pdf

[alanmalk]

Originally Posted by John in Santa Cruz

do those exist that can handle 50 amp loads? 50 amps at 0.6 volts means that diode will be a 30 watt heater. hmm, this one drops between 0.91 to 0.76 volts at 40A/leg, 80A total if both legs are paralleled. http://www.smc-diodes.com/propdf/STW...97%20REV.A.pdf

There is some good news and some bad in those specifications. At a rated temperature of 175C it is ok for the device to get rather hot. But also in the spec, in smaller type, it is rated 80 amps per device - at 50% duty cycle. Whoops...

Anyway, stepping back a bit, diodes are easy to parallel. I might consider using 4 singles instead of one double. They are also easy to cool. Bolt the 4 to a short length of aluminum "L" bracket (protected from accidental contact since it will be hot.) Another advantage of parallel diodes - lower current thru an individual diode results in less voltage drop, say .5 volts, for 25 watts dissipation total. FYI, Mouser Electronics has nice tabular specifications for all their products making it easy to compare different parts if you want to pick and choose components.

[Semievolved]

Originally Posted by alanmalk

I say this bothers me too. My brand new lithium's call for 14.4V for charging. At the moment my charging sources (truck, solar, WFCO) can't, or won't, go into 14.4V charging mode. So my lithium's will be under charged by 10 to 20%. No harm in the short term, possible harm in the long term (depending on who you read).

So I am faced with living with 3 possible choices: Under charged batteries, fully charged batteries with possible damage to equipment, or double voltage regulation.

To explain the third choice: Double voltage regulation means to me that after the WFCO DC distribution, a voltage regulator on each DC branch. Specifically, a DC-DC smps (switch mode power supply, similar to the working innards of a MPPT solar controller). This would provide high efficiency but at a steep price point. To refine this a bit more, my options are either pricey US brand name DC-DC converters or ultra cheap Chinese parts.

My jury of one is still out on this...

I am curious what your battery capacity is and what your charge rate is. Depending on what your c value is, I wouldn't be surprised if 14.4v is over 99% charged.

[John in Santa Cruz]

if the charger tops off at 13.6-13.8V, a LFP will still get about 95% charged, it will juts take a little longer.

my PD4655LI tries to output 14.4V all the time, but when the battery is sucking 50 amps, the voltage at the battery is more like 13.6V , and it doesn't go up to 14.x V until the last few minutes when the current significantly drops.

I didn't write it all down when I was poking around a the voltage loss, but a fair bit of it was between the power converter output connection block on the fuse panel, and the battery output connector that is less than an inch away, and separated by the two 40A paralleled 'reverse protection' fuses on said fuse panel

[alanerickson]

Originally Posted by John in Santa Cruz

p.s. I'm mildly annoyed that the SmartShunt doesn't record internally, you have to leave VictronConnect running and connected on your tablet/phone to get graphs like this, and even then, it only graphs the last 2 hours.

The SmartShunt *does* keep this data without the app running.....[/IMG]

Victron has a great reputation for quality and feature robust products.

That said, for those interested the Thornwave shunt is supposed to log/graph data even when it's not connected.

https://www.thornwave.com/collection...dc-power-meter

Was that an error in your post? The first paragraph says the Smartshunt "doesn't record internally", and then the second says it does keep data without needing the app.

[John in Santa Cruz]

Originally Posted by alanerickson

Victron has a great reputation for quality and feature robust products.

That said, for those interested the Thornwave shunt is supposed to log/graph data even when it's not connected.

https://www.thornwave.com/collection...dc-power-meter

Was that an error in your post? The first paragraph says the Smartshunt "doesn't record internally", and then the second says it does keep data without needing the app.

it keeps the summary data shown on that screen, not graphs.

[alanerickson]

Sanity check. I'm doing a bunch of upgrades to my E19 and in addition to adding a second 100AH battery and moving them to under the dinette bench, I'm adding a voltage regulator to the fan. Disconnected all power and start with regulator first. Wired it in. I assumed black is +V, white is negative. Put everything together and start working on batteries. A little ways into it I got to thinking...... batteries black is negative, the whole trailer isn't that way is it? So long story short, for the maxxfan is black + and white - ? Thanks.

[John in Santa Cruz]

Originally Posted by alanerickson

Sanity check. I'm doing a bunch of upgrades to my E19 and in addition to adding a second 100AH battery and moving them to under the dinette bench, I'm adding a voltage regulator to the fan. Disconnected all power and start with regulator first. Wired it in. I assumed black is +V, white is negative. Put everything together and start working on batteries. A little ways into it I got to thinking...... batteries black is negative, the whole trailer isn't that way is it? So long story short, for the maxxfan is black + and white - ? Thanks.

the clash of two worlds.

in household wiring, 120VAC, white is 'neutral', and black is 'hot'.

in standard 12VDC wiring, black is ground/negative, and red is positive, +12V.

on *SOME* RV systems, they use the HOUSEHOLD color scheme for DC wiring too, so white is GROUND and black is PLUS. This was a much bigger issue on my 2008 Casita than its been on my 2014 Escape

at the fuse panel, my maxxfan is on the same circuit as the center overhead wiring, the optional front bed reading lights, and the bathroom fan+light.

[alanerickson]

So you're saying I need to open it up and switch things around? Odd thing I was using this tutorial, and they have it as I have it wired. Shown well at 8:41.

https://www.youtube.com/watch?v=fbWuiF2JSXs&t=521s

And no matter how they did the trailer wiring I would think the fan motor leads would be as he is showing them (colors). Is what is shown not correct?

[John in Santa Cruz]

I generally verify everything with a digital voltmeter before proceeding witha ny wiring

[alanerickson]

Yes. I'll dig into it in the morning.

[alanerickson]

Got it squared away. Long day. The backwards colors are what maxxfan uses, so it is wired correctly.