Discovery: Electrical Problem

[Scuba00]

Went to visit my coach today (19 Discovery 38N) it had been awhile since we have seen each other. House batteries good ( I assume from solar charger) but coach batteries dead. Started Generator and let her run for awhile until I had good coach power and tried staring the engine - engine didn’t start but everything else shutdown, including the generator. I believe I have blown a fuse some where, I just don’t know where. I checked the Gen, outside drivers bay, inside panel by the bunks. Anyone have an idea where I should look, or what I did? Thanks in advance.

Steve

[d.mark]

I'm not commenting on your current crisis ( no pun intended )

but when you get it resolved, a 40-amp NTE5986 diode, it's cathode-case mounted on a piece of copper or aluminium, with the other end of the strip mounted on the positive battery terminal of the starter battery,

and a 30-amp inline fused wire coming from the 12+ 'house battery' terminal of your momentary/dual solenoid, one end with a ring crimp connector for the solenoid terminal, the other with an insulated spade female shoved over the anode terminal of the diode, will keep your starter battery topped-up from your house system, with a 0.7v drop. With no drainback to your house system.

[d.mark]

see below.

[KF5UMC]

You should conquer and divide. First start with coach starting batteries. How old are they? Whats your DVM show for voltage on each battery? Check water levels. check battery cables and connections. Use an external charger on the starting batteries over night.

Once you have good 12-13 vdc on engine batteries, does the engine start?

On our coach, there are large fuses/circuit breakers one for the starting batteries and one for the house batteries. Do you have drawings showing battery connections?

See my coach drawing. Keep us posted.

[Scuba00]

Thank you both for the response and advice, I returned to the coach, checked the high amp battery fuses and a few of the regular ones. Got in the coach and checked battery levels, chase showed low 8 on the dash, hit the house battery switch over button, and she fired up. Not sure what caused the shutdown the other day (might have been a slight overload that caused a auto fuse somewhere to trip) let the engine run on high idle for a bit, and then started the generator. Drove for a little and let the gen run under-load for awhile and everything looks and is working normal.

D.Mark thanks for the info, looks a little out of my comfort zone, was actually thinking of adding an additional solar panel for the chases batteries.

Steve

[KF5UMC]

Ok Steve good deal. Before my chassis (starting batteries) died on me, I started noticing while cranking the engine, the dash volt meter would drop to 8 volts DC but the engine would start. Then while at a fuel stop I had to start the genset to get enough power via the charger/inverter to get the chassis batteries up enough to kick the engine over. As soon as I got to our destination, I replaced the two chassis batteries. Now when I crank the engine, the DC volt meter on the dash stays at 12 volts or a bit more.


There is a small solar panel mounted on top of the front A/C unit. This solar panel is connected to the chassis batteries. But at the end of the day the batteries just wore out.

[d.mark]

Originally Posted by Scuba00

Was actually thinking of adding an additional solar panel for the chases batteries.

I thought about that too. But there are HUGE solar panels on the roof, and an existing charging system. And the house battery 12+ goes right up to the 'emergency start solenoid' depicted in the diagram from KF5UMC.

You need:
1 out of 5 of these, 5-count of inline fuse holders:
https://www.ebay.com/itm/5-Pack-12-G...A/122607199658

and 1 of these:
https://www.frys.com/product/1980774

You're in about $10.

A ring crimp terminal for one end:
https://www.amazon.com/12-10-High-Te.../dp/B00NVD4F4U

and a female spade connector crimp for the other end:
https://www.amazon.com/XHF2018-Fully.../dp/B07FQ87PQQ

A flat piece of metal, that has two holes: one for the post on the starter battery, one for the hole for the diode mount/cathode terminal. It acts as a mounting point and heatsink for the diode.

Hook it up like in the photo: put your ring crimp -> fuse -> female spade crimp connector together. Put the ring on the solenoid 12v+ house battery terminal (opposite side of the chassis battery wire). Let the other end, the female spade, hang for now.

Bolt the diode on the piece of metal. It comes with a washer and nut. Bolt the metal on the starter 12v+ battery post.

Finally, push the female spade connector over the anode (top) of the diode. Then install a 30-amp spade fuse to make the circuit 'live'.

Done.

[GuyG]

d.mark,
Not to hijack the thread but thanks for putting that diode info out there. I cut and pasted all of it into a Word doc for future use.

[d.mark]

Originally Posted by GuyG

d.mark,
Not to hijack the thread but thanks for putting that diode info out there. I cut and pasted all of it into a Word doc for future use.

I'll try to take another photo when the sun is cooperating and draw the circuit path on top.

prevention is the best medicine.