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I would like to hook up a trickle charger to my batteries for the winter... better to heat them from the inside out by using a smart trickle charger ( I reckon). I've had good luck with the Battery Tender brand and I am hesitant to use a cheap HF charger on expensive batteries so I will likely stick with the Battery Tender brand.

My question is will a smart trickle charger work with dual batteries? I don't see how it can? I could use to chargers but since the batteries are connected in parallel I don't see how even 2 chargers would work.

Any thoughts?
 

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Because the batteries are hooked together, the trickle charger will charge both batteries if you put it on just one.

Does your alternator charge just one battery?


Answered on my iPhone.
 

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Trickle chargers might not have enough ass to do two batteries in a reasonable amount of time. I might be wrong, but if they're only putting out milliamps, they might just be too small for a job like that.
 

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Because the batteries are hooked together, the trickle charger will charge both batteries if you put it on just one.

Does your alternator charge just one battery?


Answered on my iPhone.
i put a charger on one of my batteries and it took about 10 hours to charge, if that case was that you can only hook up to one battery and charge both then my second battery would not take another 8 hours to fully charge.

i ws always wondering, if lets say you kill your batteries, which one to you try to jump ?? lol
 

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The batteries are connected in parallel.

Any charging or discharging you do happens to both at the same time.

You can use either battery for jumping.
 

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The batteries are connected in parallel.

Any charging or discharging you do happens to both at the same time.

You can use either battery for jumping.
X2

And that's the same reason you replace batteries in pairs. If one is bad, the other may not be far behind. Hate to ruin a new battery because of a 3yo battery. Then you end up buying 3 battery's.

I thought about the sane thing with the battery tender, then split off from the cord to a timer for the block heater. Just think, you'll have 300 more cca with warm battery's. They also make solar versions so if you wasn't close to a outlet.

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There are times my truck is parked for long periods of time... I use a single trickle charger to maintain the batteries... It works great all year... Battery life is shortened every time they die or are jumped.. Maintaining the charge helps extend the life...
 

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The Battery Tender will work fine, you are not trying to charge your batteries you are only trying to maintain them. I have a Battery Tender Plus mounted under the hood and a Marinco power inlet for it on the bumper. It has a "smart" charging algorithm that goes through 3 stages, ending up at the "maintain" stage where it will stay for months if left undisturbed, without overcharging your batteries. If for any reason the charge drops to a specified level the 3 stage cycle will begin again automatically.

When you connect the charger to dual batteries you must connect it to the positive terminal of one battery and the negative terminal of the other. I ran a #10 wire hidden along the front where the battery cable is from the drivers side battery over to the Battery Tender which I mounted on the pass side fender well next to the battery. The positive lead easily reaches the pass side terminal.
 

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If you do a search on here there was a thread I think last spring all about trickle chargers and which one is best. It went on for 3+ pages I believe.

As for jumping it is recommended that you jump off of the passenger side battery since it has the larger cable going to the starter and glow plugs. But in reality you can jump off of either one if needed.
 

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but i still dont understand why it took me about 10 hours to charge one battery fully and then i plugged the other one in and it took about the same time for that one, if i can charge one battery and it will charge both, then why did i have to fully charge the other one, could it be something is faulty or if i connect to one, it will fully charge that one and then carry on to the second battery?
 

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nickt916

Search is your friend, there is a wealth of info on this forum about batteries, charging, charge rates etc. Have a look...

Net net - what the other guys have said is correct, batteries in parallel will charge at a reduced rate given a constant output of the charger. 50% is correct in theory versus a single battery, where the variance comes in is that each battery has variations due to the chemical makeup and physical variations. Too many to list here.

If you find one batt charges fully and one does not, then remove the black ground wire off of one of the batt's charge each separately. Could be one battery is starting to fail.

Age, amount of sulfation etc has an impact. As others have said, replacing in pairs is the way to go.

Good Luck

Coolhand
 

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I've got a smart charger hooked up to one battery (drivers side ) on my 99 F250 7.3. It works great to keep the batteries at peak charge without overcharging. Make sure you buy a "smart charger" vs a trickle charger so you don't end up overcharging the batteries. I got mine from GRIOT'S GARAGE .
 

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You may need to check the condition of the cables and clean the connections. If the batteries, cables and connections are in good condition both batteries should charge equally by connecting the charger to either battery.
 

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... you must connect it to the positive terminal of one battery and the negative terminal of the other. ...
Sorry, no. This technique is necessary only when there's a significant amount of voltage drop, which won't occur with short, heavy cables and a 5 Amp battery maintainer. Hook it up to whichever battery makes the hookup more convenient.

There's no compelling reason to replace batteries in pairs if one has a hard failure (such as a shorted cell) and the other does not.

A regulated battery maintainer will maintain a 100% state of charge but it won't raise the battery temperature.
 

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Sorry, no. This technique is necessary only when there's a significant amount of voltage drop, which won't occur with short, heavy cables and a 5 Amp battery maintainer. Hook it up to whichever battery makes the hookup more convenient.

There's no compelling reason to replace batteries in pairs if one has a hard failure (such as a shorted cell) and the other does not.

A regulated battery maintainer will maintain a 100% state of charge but it won't raise the battery temperature.

I would have thought the same but the instuction to connect to opposite ends of the bank comes from the Battery Tender instruction manual, I was quoting directly from the instructions.

"In Figure 9 we see a pair of 12-volt batteries connected in parallel. This 12-volt battery pack is connected to a single 12-volt charger. Note the blue wire designated W1. The purpose of this wire is to balance the voltage drop evenly across both batteries and each wire during charging. This is not critical for lower current chargers, but when you start to get into the 10 amp and above range, the voltage differential can be significant. The blue wire W1 must be connected to the opposite end of the battery pack as the black wire at the top of the battery pack."

I do see now that the instructions state it is not critical for lower current charging as you stated. I did connect mine that way though, thinking it was better.
 

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I usually go for a long period of time with out driving my vehicles ans have always used a battery tender on my vehicles and for most of the last 15 yrs they have been diesels. It always worked great but a by product of the charging process I guess while sitting with no air flow, any bare aluminum will pit and get a white powder usually most noticeable on the alternator bracket.
 
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