Batteyr charging in an RV

The old Magtek converters used to have a separate 3A charge output to the battery - so yes, it's very possible. Then someone finally realized it just doesn't matter if all the circuits in the RV are attached to the battery and seeing the same higher charge voltage. Either way the batterys internal resistance dictates how much current it takes relative to voltage at the source.
Most of the OP's statements are either wrong or point out something that just doesn't matter.

Now haven't we fed this huge troll enough?

jrnymn7 wrote:
"no converter manufactured today by anyone can charge a battery separately from the 12v system"

... insert foot... swallow hard!

You might want to read the OP's statement No. 3 again: I THINK what is meant is that RV manufacturers do not wire in the stock converter that they install such that you can switch it off from the main 12 volt circuit but still have it connected only to the RV's battery(ies) so that the converter's function during that time is to only charge the battery bank.

I could be wrong on my interpretation above, but if I'm right .... then statement No. 3 is a true description of what's going on with respect to how converters are installed in most/all Class C motorhomes.

That's how my converter is wired into my Itasca: It can be switched off competely, but of course then neither the RV's 12 volt system nor the batteries see the converter's ~13.6 volts. There is NO WAY to have the converter powered up and supplying ONLY the batteries BUT NOT the 12 volt system. IAW, the converter must be left connected to the main 12 volt system in order for the batteries to see the converters ~13.6 volt output.

However, the converse is not the case: It is possible to have the converter supplying current to only the 12 volt system, BUT NOT supplying current to the batteries (by using the battery bank's ON/OFF connection solenoid).

Matt_Collie

fustercluck. It's an Irish/Welsh term. Commonly inserted after the seventh pint...

"no converter manufactured today by anyone can charge a battery separately from the 12v system"

... insert foot... swallow hard!

When I opened this, I though that (based on engineering degrees and experience) I might write and explicit answer. No, I'm going to skip this one. What a cluster . . . Operation.

EE Excited Engineer?

Being an authority allows a battery engineer to understand and know the characteristics between a high antimony battery another of 2.75% Sb, a third with 1% and hybrid calcium negative plates. The ability to troubleshoot battery performance and lifespan and determine whether the problem is user or manufacturer caused.

This forum is a discussion thread. Actual work comes into play when a user inquires "My thirteen thousand dollar battery bank went south. Tell me why?" The when that issue is resolved...

"My budget is limited. I need the sole correct answer that will rectify this problem. And I need it fast..."

Sort of like comparing driving down Maple drive on a Sunday to driving the Indy 500. The latter brooks zero errors.

Then you approach OEM and supply -workable- answers as to how to rectify the problem.

It does require a little education and experience...

MEXICOWANDERER wrote:
Uh partner, me hates to tell you this but an electrical engineering degree is a mere single component needed to make an individual an authority on batteries. A chemical engineering degrer is also mandatory then the two disciplines have to be melded with oh, say, several decades of practical experience actually working with genuine live batteries. It also helps to have some decades of experience working around yachts, RVs and alternative energy.

An ability to shovel coal does not make one a locomotive engineer.

Also, being an authority on batteries doesn't require a rocket science degree, because understanding what makes sense for batteries isn't rocket science ... and it probably could take decades of practical experience to realize that. ;)

Well ..... I'll take a shot at rounding off some of this rhetoric ... in general terms. IMHO, the original post contains truth in it ... irrespective of whether or not it came from a trolling motive.

Regarding the OP's statement No. 1: This appears to me as true.

Regarding the OP's statement No 2: When loads are "in parallel" - as they are when both the RV's general 12 volt electrical system plus it's battery(ies) are connected separately to a stock converter's output terminals - any current from the converter will be shared between the loads, depending upon an easy math equation showing how current divides between parallel loads depending upon the size of each load. What this means in the RV world is if, to the converter, the partially discharged battery appears as a low resistance when compared to the resistance of any other 12 volt items that happen to be turned on, the battery will get most (per the equation) of the converter's current - if the battery will accept that much current relative to the voltage that winds up on it's terminals. Of course what voltage winds up on the battery's(ies') terminals in turn depends upon the converter's output voltage value -> after being reduced by the voltage drop from the current flowing through the wiring between the converter and the battery(ies).

Regarding the OP's statement No. 3: A qualified statement, but probably true 99.X% of the time .... depending upon how the RV's manufacturer installed a converter and integrated it into the RV's 12 volt system.

Regarding the OP's statement No. 4: This appears to me as true.

Regarding the OP's statement No. 5: The first three sentences very well might be true - but the information that these three sentences are trying to is convey is subtle, and would require some careful study of charging curves and an understanding of how to interpret the areas under the curvers. In the engineering world areas under curves are very important and are part of the information that's intended for them to convey. However the remainder of statement No. 5 could have been worded more clearly and qualified a bit ... I myself would be concerned about voltages above 14.8 volts appearing on my RV's entire 12 volt system.

FWIW, my (somewhat unusual) RV battery power situation agrees with what is implied in the OP's statements: My dual 100 amp hour 12 volt true deep cycle AGM coach batteries both safely float, and charge, mostly on only the RV's stock 45 amp single voltage converter. Their recommended float voltage exactly matches the converter's nominal output voltage, and .... since AGM batteries have much lower internal resistance than that of wet cell batteries .... if needing charge they also bulk charge "well" from that same nominal converter output voltage. So the fact that a converter is basically just a "power supply" works well in my setup.

I may be wrong, but I think that for decades lead acid batteries in many applications have been charged and kept charged by a single-output power supply. As far as I can tell, the main reasons for use of muilt-stage chargers in RVs are for: Squeezing longer service life out of the bulk of wet cell lead acid batteries (via a proper floating voltage) and putting more charging current faster (using a boost voltage) into both wet and dry lead acid batteries so that generator run times can be reduced. Multiple voltage levels from a charger optimize these two goals - but are not necessarily required in all situations for creating happy batteries and happy campers.

Personally I'm glad we have new members come on here and tell us whats what. Even when they are wrong about some of it and some of it is simply semantics.

I sometimes suspect that new members are really senior members that create a new identity because they want to post anonymously and/or troll.