Quote:
Originally Posted by bachler
WeTTBoY My My My;;; Isolater, Battery #1 to BaTT, #2 it will current flow only one way; Diode Will Let Current flow One way; A solenoid Is a manual control, It lets current flow Pos, to neg,or neg to pos; Onec again, There are some that feel bigger when they Be little others by showing there Stupidity, Yhaa wettboy.In my 70 years I have seen many coachs that Did not charge The coach battery when driving.. or charge the engine battery when pluged in; I do not see a need to argue about that subject,, In this day things are quite different.
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I'm starting to feel like I'm picking on a early dementia patient here, so I will attempt to be kind. I'm not picking on you bachler, I only respond because it's important that no else be misinformed by a curmudgeon's unintelligible ramblings. I'm not saying I'm better than you bachler, just more informed. I'm sure you are a better person, you'd almost have to be. Alas, I'm quite the bon vivant with questionable dealings and even more questionable morals...especially when it comes to drink and the ladies... ;-)
First, it is true that some coach's converters are not set up to charge the engine battery. But they rarely need to be.
However, NO modern coaches likely to be out there came from the factory unable to charge the coach battery pack, at least not by design.
The old mechanical isolator typically worked like this:
When you started up in the morning, the alternator would start charging the engine battery first. That would quickly "fill up", and when the voltage reached a preset level, the isolator solenoid would join both batteries as one and the coach battery could start using some of the alternator output to charge.
There are a couple of problems with this setup. First, most of the alternators in RV's are terribly underpowered and often did not get the first battery "filled up" enough, especially when running AC, lights, wipers, etc. Therefore, the voltage never went high enough to trip the isolator, and allow the coach battery to start charging. Even if it did, the amount of amps left over for charging purposes was often pathetic.
Add to that any coach 12V demands like lights, inverter, or fridge, and it would wipe out anything the alternator was adding. This often overloaded the Alt, and would cause further problems. The FIRST step to any 12V problem in a coach, should be to make sure the alt is putting out sufficient amps for all the engine demands AND the coach demands, including charging. Most of the time, the older designs came with a grossly underpowered Alt. A 30 or 45 amp- even a 60- is rarely enough for the smaller RV's, yet this is what they came with because they were cheaper.
I installed a 170 amp performance alternator in mine, that now runs everything including my 12v fridge while going down the road, while charging my coach pack. My 45 amp OEM wouldn't even charge my coach battery if I had a single accessory on. The voltage would never be sufficiently high to "trip" the old solenoid so that it would start charging. Even when it did, it only added a few amps. It would take 12 to 14 hours of driving to fill a single battery.
Another problem with that design is, these car alternators often have their peak voltage set too low. They are fine for passenger cars where the load is pretty constant and you don't want to "cook" the battery. But even if your Alt has enough amp capacity, 13.8 volts is insufficient to trigger the isolator to combine the batteries and start the coach pack charging. Mine is set to 14.7 volts and this gets the job done. Some alts have adjustable voltage, some you have to order at that voltage. I had to order mine. For coaches, this should be the ideal voltage setting as you are already going to have inevitable voltage losses through your wiring and the engine heating up your alt.
OK, so lets assume you have a kick-butt high performance alternator that consistently triggers the isolator to combine the batteries for charging. Here's the next problem with that design:
Unless both batteries are the same model and amp-hour rating, one battery is going to "fill" sooner than the other. This will send a signal to the alternator that "we" are full. The alt will reduce it's charge to a trickle. Since most people have a smaller STARTING battery for the chassis, this will top off first, leaving the coach battery much less charged. Leaving a battery say, 80% full, will quickly kill it, especially when you start using it and it drops regularly below 50% capacity. It's essential that lead acid batteries be completely charged whenever possible!
You could put the same model battery in the chassis that you have for the coach and this would solve that problem. I did this as simple solution for a while, until I got a new solid-state isolator. Gotta admit, it was nice being able to forget my lights on for hours and still be able to start up, but I could BARELY fit that battery in the engine space. You may not be able to at all.
If you don't want to buy a new deep-cycle battery for your chassis, then you have to electrically separate your two batteries, and that's what a solid-state isolator does. It's shortcomings are much easier to overcome, but that's for another day. Just wanted to let you know what to look for when trying to figure out why your coach pack isn't charging, as I have been there before myself.
Sorry these are such long posts, but I'm trying to stuff what should be a 4 hour RV battery seminar into as few paragraphs as possible....