Dual Batterys...One Charger??

[Nicki]

While charging one battery with my Battery Tender, does it charge the second battery at the same time? I want to hook up a quick disconnect to the Battery Tender, to keep them topped off when out of town.

Thanks

Nicki

 

[Bob4x4]

Yes... ... ... ... ... they are connected in parallel



Bob

 

[LambertM]

Extract from DR Service Manual, Chapter 8-8F attached. Why does the manual recommend disconnecting the batteries from each other ? I had to charge my batteries last weekend and charged them seperately as recommended. I was just a pain in the butt to disconnect each battery and having two chargers cranking 10 amps in each battery for at least 1 hour. I believe that the short trips here and there wasn't enough to charge the batteries on its own, or my batteries just need to be changed. I don't know. Any thoughts.

 

[rbattelle]

Wow, that is really interesting. I would have answered exactly as Bob did.



Maybe the reason Dodge advises against this is because current in a parallel circuit is a function of the resistance of each individual element in the circuit. That means both batteries won't necessarily receive the same amount of current during the charge. Maybe that could cause an over-charge condition at one battery?



That's just a wild guess. I'm not an electrical engineer. I doubt you'd actually hurt anything by charging both at the same time.



Ryan

 

[LambertM]

rbattelle,



Your comment makes senses. I'm a mechanical eng, not technically inclined on the electrical side, however, having mentionning the service manual requirement to a friend of mine who owns a Jeep GC btw, he believes that doing so, may cause current spikes which could potentially damage electrical equipement. Just a hypothesis, but there's a reason behind the requirement. Notice that the term "MUST" stands out.

 

[MChildress]

That has me scratching my head too. I have always charged both batteries at the same time going back to 1983 with my first 6. 9 Ford and my boat batteries also with no ill effects. They are chargeing together when the truck is running. You know they do not disconnect all the batteries in a golf cart to charge them.

 

[DBrickel]

I work in construction where we use electric driven sizzer lifts and other battery powered equipment similar to golf carts. They have on board chargers and multiple batterys. I assume these are in series as well. We do not disconnect the batterys and charge them individually. We just plug them in and they charge back up overnight. How is this different than our trucks?

 

[LambertM]

I don't know, nor could I explain how it could be any different, however, I can say with confidence that there are more electric/electronic components sensitive to DC current spikes between each battery on our Rams compared to a golf cart or even a scissor lift whose batteries (usually 6V or less in series) which simply are connected to an electrical motor drive and a few system components. Bottom line, comparing the electrical wiring diagrams between both applications would be day and night IMO.

 

[jelag]

I used to sell test equipment for batteries and charging system testing..... it was our suggestion to disconnect both batteries... . for the reason is that if you don't have a good connection from one battery to the other... . you'll not fully charge the one battery with the bad connection... .



Remember that the charging system on the truck charges both batteries together... but on a battery charger you can turn it up and damage the circuits of you exceed 16 volts... a voltage that you can't see with the charging system on the vehicle... its my guess that Dodge has got some dumb tech's who can't set a battery charger correctly and will crank it up past 16 volts and have damages some systems..... but this would be the case with a single battery and a charger as well... .



Just my thoughts.....



BTW when you plug in that charger to the sizzer lift, if you listen you'll hears some clicks on the equipment... . as you plug in the charger it should lock out the lift and isolate each battery so that you can charge it... like the series / parallel circuits on some CATS, and other large graders that use that sort of circuit... . 24 volts to start and 12 to charge and run all the lights etc... .

 

[betterthanstock]

While charging one battery with my Battery Tender, does it charge the second battery at the same time? I want to hook up a quick disconnect to the Battery Tender, to keep them topped off when out of town.

Thanks

Nicki

If all you want is to keep them topped off, just hook up a real small "float charger" ($10) at one battery, and leave them hooked up.

Nothing will be harmed.



The manual refers to charging discharged batteries. Modern "pulse chargers" that can restore a sulfated battery will spike up to 16 V and more, to break thru the sulphur. Those could damage your electronics, and should be hooked up to each battery separately, as they "read" the condition of the individual battery. Wal mart has $4 battery post disconnects, and you only need one per battery, but if they ever both become disconnected with the engine running, you may damage the alternator, or even the ECM.

 

[JimB1]

Battery tender, 2A range setting is just right. Industrial electronics pretty durable stuff and there's most likely a number of surge suppressors distrubuted thru the system protecting various circuitry but getting it all, who knows? I found out last weekend with my '07 the battery lugs are curved just right for the tender clamps to make lots of electrical contact.

 

[Nicki]

The Battery Tender I am using is a small 1. 25 amp unit. Its an older model without the de-sulphation mode, so I felt somewhat safe (after reading all of your posts) nervously went ahead and tried it today.

It did charge both batteries!

Thanks for all the info.

Nicki

 

[skipro3]

I work on large strings of batterys. There are several configurations where the batteries are in parrallel, series and combinations. There is no way we would use a seperate charger for each battery in the string. Of course it is o. k. to charge 2 twelve volt batteries that are in parrallel with a twelve volt charger.

 

[JR2]

I was just doing this yesterday to my Ford Excursion 7. 3 I charged on battery for about 4 hours and then switched the charger to the other to make sure I got both batts good.