Help! Parallax 7300 blowing 1 30a fuse & not charging batt

[Droptop351]

So I have a 2009 Winnebago access 31c just bought it from original owner. I went down to replace the bulbs with LEDs and found them dim so I check the status meter and batteries were dead I thought this was weird because it's plugged in. So I checked the fuses on the box see pic of similar below. ( I didn't take a picture of my actual unit) it's blowing the top right 30 amp fuse only, not the left one.

So I replaced it and it pops instantly, so I unplugged battery positive cable put fuse in and all good had wife put cable back on and poof. I understand these are for reverse polarity protection but from what I understand it would blow both if batteries were in wrong.

Random info
1. Plugged into shore power microwave powers on
2. Engine running 13.8 volts on battery under hood 7.8 volts on house batteries
3. Batteries are both brand new
4. When I put batteries on trickle charger the lights go real bright. ( I have the rv plugged into shore power and trickle charger plugged into 110 outlet in the rv charging the batteries)
5. Previous owner replaced batteries because the guy told him they were bad and that's why lights were dim
a. I understand new batteries would make lights brighter and that's what happened after replacing them but I believe this to be an early sign of the real problem, of the converter blowing the fuse and batteries not recharging and lights now being dim again.
6 I don't believe the batteries to be wired incorrectly they are in parallel
7. Checked breakers In a compartment and none were tripped ( not the ones to left of fuses in pic below but a diff one they are like pop out breakers (round buttons)
8. when I checked voltage at blown fuse leads I got same voltage as batteries on it
9. Fridge works - furnace works
I will try to take pics and better explain what I find with volt meter at various points.
I have tried to find wiring diagrams or ts document but they all seem to have been removed from parallax website. I'm leaning towards this unit being bad although I can't rule out a short just yet either.
Any help is appreciated, if I need to test something different or provide more info just let me know what.

[Bobbo]

Note: those fuses always blow in pairs. You will never find only one of them blown.

Those fuses are wired in parallel, each taking about half of the current load. When one of them blows, the other takes the full current load, and it blows too.

[Droptop351]

Solved it today appears that the 2nd fuse was indeed blown even though didn't look it. After charging batteries and replacing it and then the other fuse everything appears to be on up and up. Going to check it over next few days to make sure. I'm guessing when previous owner replaced batteries they were put in backwards first

Thank you all for your help

[YC_1]

Ditto on the dead battery trying to draw more than 30 amps. Get it charged back up if it will take a charge. That is severely low.

Your alternator should be charging it but it seems that circuit is not working for you. Start the engine and press the emergency start/aux start button. Prop it in the active mode or have someone hold it down. Then measure the voltage on the dead battery.

If the previous test does not show the second coach batteries getting charged then start looking for a blow fuse. It could be the combining solenoid but that can be chased later.

[wa8yxm]

You said Batteries are DEAD Now what is the full model number of that Parallex? a 7345 can, in theory pump up to 45 amps into the batteries if they are that low.. But the fuse is only 30 amp.

The solution.. Partially charge the batteries via another method, such as a "Dumb" auto charger (odds are smart chargers will refuse the job) say a 10 amp for one hour.. Then see if the parallex will hold. Or drop one battery off, see if the parallex will charge the other, then tomorrow sway them and then hook them back together.. The parallex normally does not put full current into the batteries but if they are very dead,, It will try, and that can pop the fuse.

[RoyB]

Are the two new batteries 12VDC batteries or 6VDC batteries...

If they are 6VDC batteries they must be connected in series to give you 12VDC to supply your system with...


About the only thing that will blow the 30A FUSES that are off to them self (The GREEN Ones) is cables going to the batteries connected wrong, batteries are not connected together correctly, or a dead cell in the battery drawing alot of DC current.

If your two batteries are 12VDC they are to be connected in Parallel. If they are 6VDC batteries then they must be connected in series...

Other note is the older parallax converter/charger is not one of the smart mode chargers and should be replaced for a smart mode version converter/charger. The smart mode converter/chargers will almost take care of your batteries automatically...

Roy Ken

[MEXICOWANDERER]

So if it worked before and without touching the battery connections so it doesn't work now so you have one of 2 possibilities. A bad breaker or a bad converter. So you can start checking those two items.

[Old-Biscuit]

Batteries are both brand new


That would indicate where your problem is.

Those 30A Fuses are the 'Reverse Polarity' fuses and blow when battery pos/neg cables have been reversed. They protect the converter/charger system

Your NEW batteries maybe connected together correctly but the pos/neg cables going from battery bank are reversed.
Follow the NEG cable to frame ground to verify it is connected to ground.


In your picture of the 'panel' you see that the RED cable goes to POS and the White Cable goes to GRD.
Those may not be your actual battery cable colors but that is the way the cables should be at the battery terminals.
RED cable on one battery POS post and WHITE cable on other battery NEG post
RED cable coming on to converter
WHITE cable coming into converter and going to frame ground




12V DC items in coach are working cause when plugged into AC Power the converter is supplying the DC System but can NT charge batteries due to reversed polarity condition

[Droptop351]

So found this wiring diagram and it says the right one is a gnd? I do remember checking and I do have voltage on one side of the fuse so if it is a ground that explains it popping the fuse. How do I go about troubleshooting this now?

PDFs link

[Droptop351]

This is a pretty good representation of mine without having access to actual picture of it