A conversation with an RV tech (long)

[John in Santa Cruz]

here's the end of a charge cycle on mine.



starts with the battery at about 13.2V and minimal current output. charger is turned on, voltage almost immediately climbs to 13.6V or so and current to around 40 amps, then the current drops as the voltage climbs, when the current drops to 11 amps, the voltage is at 14.3V, then the current drops to zero because the batteries are fully charged, the voltage jumps to 14.6V and two cell balance cycles commence oover the next 15-20 minutes, where the battery draws around 12-15 amps for short periods.

[Mike G]

This is powerful information. (pun intended)
I think most solar controllers will also charge to 14.4V or thereabout, won't they? So, a similar issue perhaps?

[John in Santa Cruz]

Originally Posted by Mike G

This is powerful information. (pun intended)
I think most solar controllers will also charge to 14.4V or thereabout, won't they? So, a similar issue perhaps?

My Victron solar controller in lithium mode defaults to 14.4 for no more than hour after full charge then it drops to 13.6

[tdf-texas]

Originally Posted by Mike Lewis

"I think I killed the circuit board," I said.

He pulled the cover off and confirmed that the circuit board was the problem. "Your voltage is 14.7. That's too high." I was plugged in at the time to shore power. "Your voltage needs to be in the 13 volt range."

"I was afraid of that."

The Atwood AFSAD12 / Dometic™ AFSD12 gas heater control board doesn't seem like voltages higher than 13.7v. Some will seem to last forever but tend to fail when it's most inconvenient to the owner. Other devices in your RV that tend to let the smoke out are the previous versions of Maxxfan control boards and the Suburban SW6DE control board.

But as you said, you already know that. Sorry you didn't get your voltage regulators installed before the failure. Hopefully you can get them in before one of the other two fail.

[Tonny LR]

I am not familiar with voltage controller? May I ask which brand of voltage controller to buy and the proper location to install it? Thank you.

Tonny LR

[rubicon327]

Originally Posted by wind bear

Curious to know what he would recommend!

Probably anything besides Dometic

[fudge_brownie]

Good question Tonny, what I know is you will need several. They are pretty cheap.

Are they easy to install ?

Is soldering required?

I know the MaxxFan is one that is prone to failure.

Finally, it appears this issue affects only users who install the upgrade to the WFCO power center that charges the lithium batteries at some quite high charge rates. It does not seem having lithium batteries cause the problem.

This is not to say a voltage regulator is bad and there maybe other benefits. It just may not be worth the effort in all situations.

[Tonny LR]

Paul,
Thank you for your response.
Tonny LR

[alanmalk]

Originally Posted by fudge_brownie

...
It does not seem having lithium batteries cause the problem.

This is not to say a voltage regulator is bad and there maybe other benefits. It just may not be worth the effort in all situations.

Worth noting: Most lithium batteries say "12.8 Volts". In round numbers this is correct, however, they supply most of their power at or above 12.8. When they drop to 12.8 they are not too far from empty. That leaves, as you said, the charger and charging voltage as the problem - typically 14.4 - 14.8. That's the upper limit for many trailer electronics.

Which brings us to voltage regulators. The principal is OK, regulate a single device or perhaps a number of low to moderate power devices on one circuit (wire). 14.4 volts in, 12.8 volts out. But - and this a big "but" - what happens when the battery is down to 12.9 volts? Some regulators might work fine at voltages near the output setting, and some will just pass the voltage along even if it is below the output setting - but only the fine print will confirm this. The alternative is that the voltage regulator just cuts off the power, or even worse, gets damaged in the process. Its just one more thing to think about when switching to Lithium batteries.

The answer of course is "lithium ready" devices than can handle 11 to 16 volts. Not too many out there yet...

[fudge_brownie]

Nice explanation of a voltage regulator. I would guess there is a myriad of brands and specs to sort through in making a selection.

I would agree that converting to lithium opens many new issues. Not sure these exist when ordering a trailer with lithium. In considering a conversion I have developed such a long list of auxiliary costs and tasks I am wondering if it is worth it.

[Mike Lewis]

Originally Posted by Tonny LR

I am not familiar with voltage controller? May I ask which brand of voltage controller to buy and the proper location to install it? Thank you.

Tonny LR

Based upon a recommendation in the forum, I bought two of these and have done nothing with them:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


I don't know where to put the regulators. In my trailer the ceiling fan, furnace, and water heater all use the same 15A fuse, so maybe near it.

[alanmalk]

Originally Posted by Mike Lewis

Based upon a recommendation in the forum, I bought two of these and have done nothing with them:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


I don't know where to put the regulators. In my trailer the ceiling fan, furnace, and water heater all use the same 15A fuse, so maybe near it.

Looks like these are no longer available. Being a buck/boost regulator they are fine for a wide range of input voltages. But be alert to the specs - at certain voltage combinations of input/output the maximum amperage drops a bit. So for that reason I would not put them at the head of a 15 amp circuit, but rather at the input of an individual device.

[tdf-texas]

Originally Posted by alanmalk

Looks like these are no longer available. Being a buck/boost regulator they are fine for a wide range of input voltages. But be alert to the specs - at certain voltage combinations of input/output the maximum amperage drops a bit. So for that reason I would not put them at the head of a 15 amp circuit, but rather at the input of an individual device.

I've been buying them from Ebay shipped from China but they are still available from Amazon. A search for LTC3780 picks them up. Be sure to get the single adjustment pot ones - some have three adjustments that take some expertise to set.
https://www.amazon.com/LTC3780-Autom.../dp/B08MDG1LLT

One voltage regulator per device is the rule of thumb - the inrush current that a Maxfan pulls is enough to require a separate one of these. I usually mount these at the device I'm protecting using SAE connectors. It makes it easy to install and, if it ever happens, easy to replace the regulators.
https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1

I use the SAE connectors installed such that, if I needed to, the regulator could be removed and the SAE connectors connected back to each other.

I found some little plastic vented boxes that the regulators fit in to use to mount them. The boxes allow more mounting options without having to worry about shorting issues.

[Perry Butler]

Originally Posted by tdf-texas

I found some little plastic vented boxes that the regulators fit in to use to mount them. The boxes allow more mounting options without having to worry about shorting issues.

Do you have a link to this box?

Thanks,

Perry

[rubicon327]

Originally Posted by fudge_brownie

I would agree that converting to lithium opens many new issues. Not sure these exist when ordering a trailer with lithium. In considering a conversion I have developed such a long list of auxiliary costs and tasks I am wondering if it is worth it.

There are definitely a few things to think about. As I ponder this over-voltage issue a bit more I realize the WFCO converter/charger whether lithium-ready or not is not an ideal solution. The unit puts out the same non-adjustable voltage (as high as 14.6V in bulk) to all 12V devices as it sends to charge the battery. This is apparently too high in some cases - although admittedly we never had an issue with the stock WFCO 8955 charger or the Progressive Dynamics WildKat main board upgrade (14.4V in bulk/boost). When I finally decided on a major upgrade to lithium I changed the system architecture with a combination inverter/charger. I believe the way it is designed and wired should provide inherent protection from the (possible) over-voltage issues. In my system there is no "converter". I must have a battery installed to have 12V DC power and it acts as a buffer between the 12V devices and the charger. The Xantrex Freedom XC unit also allows you to customize the charging voltage. The Bestgo lithium battery calls for 14.4-14.6V optimal charge voltage but I believe I'm set a bit conservatively at 14.0V (3.5V/cell). The battery is a nominal 12.8V (3.2V/cell) and when fully charged I typically see around 13.3V on the Victron battery monitor.

Proper lithium setups can get a bit complex. I needed the amp-hours for extended boondocking and didn't want the extra weight of lead acid. While I was at it I did the combo inverter/charger for the programming flexibility and to run mini-split A/C just because I could. For many users an upgrade to sealed AGM batteries that require no maintenance would be more than adequate and would be my recommendation.

[Tonny LR]

Originally Posted by Mike Lewis

Based upon a recommendation in the forum, I bought two of these and have done nothing with them:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


I don't know where to put the regulators. In my trailer the ceiling fan, furnace, and water heater all use the same 15A fuse, so maybe near it.

Mike,
Thank you for explaining the need for voltage regulator for each appliance. Due to lack of knowledge, I though that I could use one voltage regulator for the whole trailer.
Tonny LR

[alanmalk]

Originally Posted by Tonny LR

Mike,
Thank you for explaining the need for voltage regulator for each appliance. Due to lack of knowledge, I though that I could use one voltage regulator for the whole trailer.
Tonny LR

The devices currently for sale on Amazon have a max output of 10 amps and a recommended continuous output of 7 amps. Definitely one per device, and low amp devices at that. In other words it would not work for the 12 volt heating option of the refrigerator.

[fudge_brownie]

Originally Posted by rubicon327

For many users an upgrade to sealed AGM batteries that require no maintenance would be more than adequate and would be my recommendation.

I agree with that recommendation.

[tdf-texas]

Originally Posted by alanmalk

The devices currently for sale on Amazon have a max output of 10 amps and a recommended continuous output of 7 amps. Definitely one per device, and low amp devices at that. In other words it would not work for the 12 volt heating option of the refrigerator.

Alan, why would you want to install a voltage regulator on a resistive device such as the refrigerator? It doesn't care if the voltage is higher - in fact it rather likes the higher voltages as that allows it to cool better.

Devices that should be considered for boost/buck voltage regulators are:

1. Maxxfan
2. Propane Heater
3. Hot water heater

The rest of the devices should be fine.

Those owners with the electric awning might want to look at where the power is coming from for that device. Dometic requires that the awning be powered from a dedicated 15 amp DC run. On my trailer, the whole passenger side of the trailer was powered off the single DC run that also powered the awning. My awning now has a 14ga dedicated DC run.

[tdf-texas]

Originally Posted by Perry Butler

Do you have a link to this box?

Thanks,

Perry

The ones I used seem to be not available. But this one would be a great choice.
https://www.amazon.com/Ventilated-Pr.../dp/B00V8MK9TG