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Old 10-31-2020, 05:02 PM   #57
dkoldman
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Brand: Still Looking
Model: Sunstar 29VE Winnebago
State: Texas
Posts: 5,584
THOR #13058
Quote:
Originally Posted by 16ACE27 View Post
Well, look at it this way:

Your battery puts out 12 VDC and is capable of supplying hundreds of amps to DC loads. But it only supplies the amps the loads call for. The loads have some "resistance" to current flow. In a simple DC circuit the "resistance" is actually resistance measured in ohms.

So if you connect your 12 volt battery to a lightbulb that has a resistance of 12 ohms, Ohm's Law says there will be 1 amp flowing in that circuit.
I (current) = Voltage/Resistance or 1 = 12 VDC/12 Ohms.

In more complex DC circuits that have motors and other batteries being charged the "resistance" includes the push-back from the charging battery and the Counter Electromotive Force (CEMF) of the operating motor, both of which are variable (as the battery charges its voltage increases so its "push-back" increases. As the workload on the motor increases its CEMF decreases and it draws more current to supply the load).

So when you change the range of your battery charger from say; 10 amps, to 50 amps, it does 2 things:
Raises the voltage applied to increase the current for a given battery.
Increases the ability of the charger to supply more current.

So if your battery charger applies; say, 14 VDC on the 10 amp setting, it will raise that applied voltage to; say, 16 VDC on the 50 amps setting - these are just theoretical numbers - your charger's voltage numbers may be different.

So if you are charging a battery on the 10 amp setting and it's actually only drawing 5 amps due to its state of charge ("resistance"), and you switch it to the 50 amp setting, the current will go up due to the increased applied voltage, but it won't go up to 50 amps because the battery is not dead and is still opposing the applied voltage reducing the current to what it will accept for it's state of charge.

Now unless you have a modern smart charger if you leave the battery on the 50 amp setting you will "cook" it because it can't charge to 16 VDC so the current will never decrease to 0 amps when it is fully charged.

Bottom line - get your voltmeter out and check the applied voltage on your charger on the 50 amp setting to be sure it's not ridiculously high. Remember, it's a charger, not a DC power supply.
This is what my voltmeters says. Mind you my charger is at least 20 years old

.3 amps Maintainer 9.90 vdc
2 amps 10.29 vdc
10 amps 11.80 vdc
50 amps 13.71 vdc
Off 3.43 vdc ( I found this odd, I guess off don't mean off? )

Sounds like the charger should work for me. The manual says the Jet-flo should not run longer than 15 minutes; so I think I will allow it to run no more than 10 minutes max at one time; until it has had time to cool down.


I am also looking at other power alternatives.

1. Portable Generator - Out 8.3 vdc amp limit
2. Connect to Chassis Batteries - Not preferred would have to run wire across the entire coach
3. Connect to 12vdc going to the Onan 5500 generator - Not Preferred as the wiring is with a pack of about 8 looms so it is hard to know which is which; see picture.
4. Connect to wiring in wet bay that supplies the 10 amp water pump. See picture. Ideally if I could find a Y splitter connect and it would be plug and play. (assuming that the wiring could handle a possible 20 amp load) or I could put the male connector on the end of my sea dog plug? That would have mean simply unplug the pump, and then plug in the Jet flo using same connector. The latter has a built in safety because no chance of running water pump and macerator pump at the same time. What I don't know is what type of fuse is on the water pump line? I need 20 amps.


Related:
I returned the 2 new 50' 3/4" hoses in favor of 1 100' 3/4" hose. I only need 75 feet so I may cut off the last 25' or so.

When I was measuring this morning I was worried that the connection of the two 50' hoses would join somewhere in the house I am sure I could tighten the fittings so it would not leak, but why fool with it. a 75 ft hose is preferred for me, but they cost a lot more and can be 1 week or so to get in 3/4" size. It may be that cutting it off to be a perfect fit for my longest possible run of 71' or so is best anyway. Sticking the hose with no metal fitting down in toilet may also be better?
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2019 Sunstar 29ve; Toad Lincoln Navigator; RVi Brake 3 & Command Center; Roadmaster Nighthawk Tow bar & Baseplate; Sumo Springs; Safe T Plus; Onan EC-30 AGS; Vmax 250ah AGM; T-Mobile Internet; H/W Heater / Chassis Disconnect Switches; Southwire Surge Guard 44270 & 34951 w/Monitor 40301; Jet Flo Macerator; Alpine SPE500 Speakers; Visio M21D-H8R
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