Another dumb dual battery question

[boondocking]

I totally agree with the bad cell battery discharging the good battery. I can not see where one battery will draw from the other then vise versa. I don't understand how that could be possible.

By the way your link does not work.

[A32Deuce]

Generaly if a cell goes bad, it will discharge all the other cells connected to it. That is how a battery goes bad. Test with a hydrometer to find a bad cell. If you catch it soon enough, you can save a battery. Where I retired from, we had big banks of battery and daily checked the fluid in them.

[N6ZCM]

Originally Posted by TitanMike

Does it have an Isolation Solenoid that only connects therm when you turn on the key and disconnects them from the parallel circuit when you turn it off?

If not then hope you don't have one of those batteries develop a bad cell that lowers it's voltage. You will end up with two dead batteries.

BTW, I've never heard of a lot of things. Doesn't mean they don't exist.

No there is no Isolation solenoid.
It was built this way, I did not add a second battery, all Dodges with Cummins Diesel have dual battery setup.

Yes, I totally agree with you 100%, if one battery goes bad it can drain the good one, since they are the same age if one is going bad then the other is right behind.
The one time it happened in my Dodge in the past 10 years, it was never dead just low voltage, hard starting BUT never totally dead! The bad battery will only drag the other down to what the bad battery voltage can hold, so one cell goes bad it still will have 10.5 volts in a battery! All the cells would have to go bad for a battery to drain to zero volts. It is rare that a cell would totally fail, get weak yes!

For the past 30 plus years of owning, Travel Trailer, Motor Homes, and several 5th wheels, ALL have had dual parallel battery setup.
I have never had less than 5 year old batteries do what you have described, except when one goes bad... but the first sign of a problem is quick voltage drop when you pull a heavy load, like the water pump or the heater! When that happens time for new batteries!
But I always replace both NEVER one!

As stated my Dodge and 5th wheel have Dual parallel battery setup that sets 3 months, the 5th wheel could sit for 6 months, never had dead batteries. The 5th wheel all I do is turn the disconnect off but the batteries are still connected parallel. maybe 12.5 after 6 months, but it all depends on how cold batteries get, if they get cold, then they can drain a little!

[Jonol]

Here you go with a marine selector switch.

See Diagram

[TitanMike]

Originally Posted by Jonol

Here you go with a marine selector switch.

See Diagram

With mine I have a 50 Amp Circuit breaker mounted near the batteries (where I have my switch) to protect the line that runs most of the length of the trailer to the Converter. The Converter has the dual 40 amp fuses to protect the Converter itself. If I had a 20 amp fuse at the batteries there's a chance it would blow every time I powered up the A/C line and the batteries began to charge. My Converter is a 55 amp unit so I suspect the charging current is a lot more than 20 amp initially..

[Jonol]

Then since you have a 50 Amp Circuit breaker on the line ,you dont need to add the 20 amp fuse.

[TitanMike]

Originally Posted by Jonol

Then since you have a 50 Amp Circuit breaker on the line ,you dont need to add the 20 amp fuse.

Just curious but where does your converter connect in your circuit?

[Jonol]

It connect on 120 volt AC like your hause outlet.

[Maxwell D Pratt]

N6ZCN my call is N8SAC and name is Dale and I agree I use two battery's and have on two campers. I also have a HF 75 watt solar . I have a Rockwood Freedom with all the extras. I replace both battery's about every five years. The solar panels keep the battery's up all year round without plugging in to 120 volt AC.

[TitanMike]

Originally Posted by Jonol

It connect on 120 volt AC like your hause outlet.

Where does it deliver it's 12V charging current? At the battery or downstream from the fuse.

[Jonol]

It delever downstream from the fuse, so if you connect the switch after your 50 amp braker, it will work.

[N6ZCM]

Originally Posted by Maxwell D Pratt

N6ZCN my call is N8SAC and name is Dale and I agree I use two battery's and have on two campers. I also have a HF 75 watt solar . I have a Rockwood Freedom with all the extras. I replace both battery's about every five years. The solar panels keep the battery's up all year round without plugging in to 120 volt AC.

Small world... 2 hams same name......

When I was building and maintaining hilltop 2m, 440, 1200 repeaters here in Los Angeles we used 3 and 4 12 volt batteries in parallel as backup power to keep the repeaters on air for several days, of course low power (10 watts), and the key was to replace the batteries every 5 years whether it needed or not!
and every month for 2 days, we would put it into emergency mode to test battery system! never once did we have one battery kill another!

One site was total solar powered, it had four, 6 volts, 2 in series then in parallel.

Dale
73's N6ZCM

[Maxwell D Pratt]

Pleased to meet you . We have two hobbys that are the same. Don't get to camp enough to enjoy the way a retired person should . Usually camp close to home so I can take pontoon too. Nothing like taking a relaxing boat ride on the afternoon. I am on FB , Maxwell D Pratt. When I was working installed simplex repeaters for telemetry systems ( Water & Sewer Plants) we had a lot of them runing on solar panels with battery power.