~14.4V lithium charging vs ‘nominal 12V’ house devices?

[Centex]

Not Escape specific, just RV's in general including Escapes ...

For a very long time I believe it’s been generally accepted that ‘nominal 12VDC’ systems and devices used in motor vehicles and RV’s actually experience and are designed to be ‘happy’ with voltages up to ~13.6VDC. Please correct me if that’s wrong.

Yes, I’m aware that the latest vehicle ‘smart charging’ alternator systems now bump-up to ~14.1VDC (and even higher approaching ~15.xxVDC when in ‘desulfation mode’ for brief periods). But sticking with RV systems ….

We know that many LiFePO4 batteries like to see upwards of ~14.4VDC, maybe even a tad more, to achieve ‘full capacity charge’. We also know that many of the latest RV converter/ chargers/ power-centers /charge controllers designed for LiFePO4 batteries deliver those voltages for varying periods of time, some of them ‘smarter than others’ in terms of when, for how long, and at what current (amps) that happens. We note for example that several of the Progressive Dynamics “9xxxL” (lithium application) converter/ chargers are specified to deliver 14.6VDC output at full-rated amperage at all times.

We also know that for most (all?) of those RV systems the voltage above ~13.6VDC is what’s delivered to all the 'nominal 12VDC rated' house devices (lights, pumps, refrigerators, fans, etc, etc, etc) via the common DC distribution bus / fuse panel. Focusing only on the house-distribution side of this ….

• What’s the implication of that for all those ‘nominal 12VDC rated’ house devices?
• Are all of those devices ‘happy’ with those ~14.xxVDC ‘excursions’? (the saga of Maxxfan control boards of a certain vintage with apparent particular sensitivity to power-supply voltage comes to mind)
• How do we avoid possible adverse impacts on the longevity / health of ‘nominal 12VDC rated’ RV devices?

OR, is all of this a total non-issue of my own imagining and that’s why, with the emergence of LiFePO4 systems for RV’s, we’ve not seen the emergence of house-distribution panels that are voltage-regulated separate from the LiFePO4 battery charging systems and batteries?

Just curious, figuring some of the resident experts can set me straight/ explain / give reassurance …

[TX_Clint]

DC appliances that run on 12 VDC will easily handle voltages from 10 – 15 VDC without any problems. To recharge a lead acid battery you commonly need a charging voltage of 14.4 VDC and so it’s a common voltage.

[Brian B-P]

Originally Posted by Centex

For a very long time I believe it’s been generally accepted that ‘nominal 12VDC’ systems and devices used in motor vehicles and RV’s actually experience and are designed to be ‘happy’ with voltages up to ~13.6VDC. Please correct me if that’s wrong.

Yes, I’m aware that the latest vehicle ‘smart charging’ alternator systems now bump-up to ~14.1VDC (and even higher approaching ~15.xxVDC when in ‘desulfation mode’ for brief periods). But sticking with RV systems ….

I've seen about 14.2 V on ordinary vehicle charging systems for many years. Of course the connected trailer doesn't generally see that due to resistive losses in the long (and often questionable) connecting wiring.

Originally Posted by Centex

• What’s the implication of that for all those ‘nominal 12VDC rated’ house devices?

The ones which are not suitable for the increased voltage die.

Originally Posted by Centex

• Are all of those devices ‘happy’ with those ~14.xxVDC ‘excursions’? (the saga of Maxxfan control boards of a certain vintage with apparent particular sensitivity to power-supply voltage comes to mind)

No, but most are... and I can't remember what other than MaxxFans have been failing. I suspect that some LED lighting intended for use on regulated 12 V supplies in homes would be in trouble. The absorption charging stage of my Progressive Dynamics converter in one RV certainly makes the Atwood furnace sound like it is being run ragged, although the board has only failed once...

Originally Posted by Centex

• How do we avoid possible adverse impacts on the longevity / health of ‘nominal 12VDC rated’ RV devices?

Some people, including Escape owners in this forum, have added voltage regulators ahead of only the devices which need; you know the other obvious answer...

Originally Posted by Centex

OR, is all of this a total non-issue of my own imagining and that’s why, with the emergence of LiFePO4 systems for RV’s, we’ve not seen the emergence of house-distribution panels that are voltage-regulated separate from the LiFePO4 battery charging systems and batteries?

I think that this is primarily a financial matter, not a technical one. The vast majority of RV buyers are not willing to pay for a more sophisticated solution, so rational RV manufacturers will not provide it except as an option. Due to the extent of changes required, most RV manufacturers would not want to offer this even as an option.

There are at least two whole-RV solutions:

1. DC-to-DC power supply (voltage regulator) between the battery and the distribution panel, preferably with a bypass switch for reliability (can be bypassed if it fails, especially if the battery voltage isn't high anyway)
2. separating the two functions of battery charging and powering loads from a converter:
   • provide separate lithium-specific battery charger and constant voltage (no more than 13.2 V) converter
   • add a transfer switch which connects loads to either the battery or (when shore power is available) the converter
   • set all other charging sources (solar, tow vehicle) to maximum voltages which are safe for loads, even though that won't maximize battery charge