Batteries not charging.

This is what is balanced and best for twin twelve volt batteries.



As it often doesn't cost a dime more to do this, I think it is worth the trouble.

If you wish to understand the "why" surf here:

correctly interconnecting multiple twelve volt batteries

Others may say it doesn't matter--but unless there is a compelling reason to not optimize charging and discharging why not do it the best possible way?

It doesn't matter how the batteries are connected, they will get charged.

There isn't "two paths for power" and the charger won't get confused as to which battery needs charged.

Batteries draw current from the charger, so each one will "draw" whatever amount of current is needed in order to become fully charged"

The other diagram is better way because it "balances" the load, meaning it draws power more equally from both batteries in a discharge situation.

When I worked for Heart Interface (now known as Xantrex) this was how we always recommended connecting batteries in RVs and boats, or any system where an inverter or DC loads were being powered by a battery bank.

Barkoff wrote:

jimh425 wrote:
I can't tell how you have it wired, but look at this diagram. It doesn't really sound like the converter/charger is working.

No, I went simplistic, simplistic won't work?

Hi,

The CPAP can use 5 amps per hour, or about 50 amp hours overnight, even more with the humidifier in use.

Each group 27 battery is about 105 amp hours in a LAB, not the real world.

Your factory charging system from truck to camper is probably #12 wire, or smaller. Basically you are hooking together a 12 volt truck battery to the 11.7 volt camper battery. So not much amperage is going to flow.

You can improve your camper battery charge rate by installing a #4 wire from the alternator (a 13.8 volt source) to the plug on the side of the truck, then to the camper via more #8 or #4 wire. You can buy a Anderson Connection - made for forklifts, and rated at 50 or 250 amps.

I would also use a forklift relay such as the 6C017 forklift relay rated at 100 amps with 12 volt DC coil. And a automatic reset circuit breaker rated at around 40 or 50 amps. This will allow you to recharge all the batteries in a couple of hours of drive time.

However you can not charge the battery while parked, unless you run the generator a long time. You can also use a pair of large solar panels to help refill the batteries.

SunElec.com They sell many house sized panels, you might need to call to ask about 12 volt nominal panels (21 volt open circuit panels).

I installed a 400 watt system for a friend, and he could recharge the batteries about 30% to 75% in one day, but still used more power each day than the 400W system made - even in sunny AZ. He ran a 120 volt CPAP with a 1,500 watt inverter.

Fred.

The real simple test is to use a multimeter and read the battery terminals with the shore power turned off. This is assuming that both batteries are 12VDC batteries connected in parallel. If the battery is fully charged it will read 12.6-7VDC. Then turn ON the Shore Power and reading the same battery terminals should now jump to 13.6VDC. This is telling you the connection between the converter/charger and the battery terminals are good. It is also telling you the converter/charger unit is working.

If you do see any increase in DC VOLTAGE when you turn on Shore Power then obviously you are not making connections between the converter/charger and the battery terminals. Both the battery connections and the DC output of the converter/charger unit should feed the 12VDC power distribution panel where all of the 12VDC fuses are located.

There is a couple of things to check. You should find a in-line fuse real close to the battery terminals. Check this fuse. You also have two fuses on the 12VDC distribution Panel labeled REVERSE POLARITY. These two fuse will be be high current values. Make sure they are not blown. These fuses and mechanical battery cable connections are about the only things between the output of the converter/charger and the battery terminals. You have already said the ceiling lights etc work just fine when on Shore Power so this tells you the converter/charge unit is working OK.

If your trailer has a battery disconnect switch installed it must be connected to charge your batteries.

Shouldn't be too hard to tell where you are not getting the 13.6VDC coming from your powered up converter/charger unit and the battery terminals.

just some of my thoughts
Roy Ken

No simplicity doesn't work......wired your way you have 2 separate 12v batteries
Need to wire them parallel (+ to + and - to -) so that you still have 12v but double amp/hours and they discharge/recharge together as a whole vs 2 independent


Then you need to check your converter DC output when connected to an AC power source (shore or generator) With 110V AC input to converter should have at minimum 13.2V DC output from converter (test at converter with battery cable disconnected)
Also check that 'reverse polarity' fuses aren't blown (2 large fuses on converter).

And a 'load test' on batteries would be a good thing...local auto parts store

That will be my next effort, thank you!

Your diagram shows more than one path for the charging and power draw. I'm not sure the converter would understand how to balance the power. I'd change yours to match the 12V diagram and see if it works better. Feel free to leave the cables full length for the test.

jimh425 wrote:
I can't tell how you have it wired, but look at this diagram. It doesn't really sound like the converter/charger is working.

No, I went simplistic, simplistic won't work?

Mike, are you checking voltage with a VOLT METER? What SIZE batters are we talking about?? Goggle 12 volt side of life and read. JMO

I can't tell how you have it wired, but look at this diagram. It doesn't really sound like the converter/charger is working.