[vfabricius]

If I hook up a battery charger to the one battery under the hood, will it charge the other battery under the floor on the frame rail? since the my van is only driven a couple of times a month should I leave a charger on it set at 2 amps or just use a battery maintainer? Thank you in advance.

 

[bugman]

Yes it will

Other than a regular charger look at a Battery Tender. I have my truck, car, and ATV on separate ones. And they are better for your batteries that a regular charger.

 

[John in OkieLand]

put this on the truck in a place where Engine Heat will not get to it.
--- for myself, I zip tied it to the plastic shelf between the Radiator and Grill.


I leave the DC leads connected to the Battery all the time.

I plug in the shore power if it is cold, or I won't be using the truck for a few weeks or months.

4.5 amps, will do everything your battery needs.

https://www.amazon.com/gp/product/B0B2XP7BXY/

 

[bobofthenorth]

If I hook up a battery charger to the one battery under the hood, will it charge the other battery under the floor on the frame rail?

Yes but ..........

The remote battery will see the voltage at the end of its long cable so the connections on either end of that cable are doubly important. If one or both of those cable ends is compromised by corrosion the remote battery will charge more slowly and won't deliver as much fire to help get the van started. And don't neglect the grounds. The little tiny electrons need to leave the battery AND return to the battery. Anything slowing them down will affect performance of the whole system.

 

[John in OkieLand]

agree with ^^^ post.

the cable between the two batteries, must be big and Fat, with large brass terminals.

Place a Digital Voltmeter across the two battery positive posts.

The difference should be 0.00 volts, especially for a battery charger at low current levels.

 

[klhansen]

the cable between the two batteries, must be big and Fat, with large brass terminals.

That shouldn't be a problem with a diesel van, as both batteries are paralleled at all times for starting capacity. Same as a diesel pickup except for the under body location of the second battery. But corrosion at the terminals and under the insulation is something that has to be eliminated.

 

[James-Bob]

I move the charger from one battery to the other. Or if you look at the attached drawings you will see the difference between unbalance and balanced charging looks like.

 

[klhansen]

@James-Bob
Good info. Unfortunately on a van, the second battery is mounted under the chassis and a PITA to get at. That balanced charging diagram is like reverse-return piping for an HVAC hydronic system. Good if you can do it (long enough leads on the charger to reach both batteries at the same time. I'm questioning how much imbalance they're stating on the unbalanced charging. Assuming that the connecting cables have minimal resistance (are adequately sized) and the internal resistance of the batteries is the same, they should each draw very close to the same amperage on charging. But if the cable connections are corroded, then all bets are off.

 

[James-Bob]

Yep reverse-return...I am now a retired plumbing contractor...specialized in Hydronic Radiant Floor Heating and Hydronic Forced Air Systems, well after 45+ years it's hard to stay retired, people never loose my phone number. These two diagrams are part of a very detailed study. I did my own testing and they are correct on the imbalance. I suppose you could make up your own long cables..I would probably just charge each battery on it's own.

 

[bugman]

I am sure that if there was enough of a imbalance with charging the battery that is under the van the Ford engineers would of addressed that by running a charge wire from the alternator to both batteries, instead of just the top battery.

 

[bobofthenorth]

I've seen that "balanced" charge diagram many times and its nonsense every time. It assumes an inadequate parallel cable. If that is in fact the case then the cable is the problem, not the charging lead arrangement. Use big cables. Keep the connections clean. If you don't believe me, measure the resistance between the positive clamp on Battery A and the positive clamp on Battery B (or C or D or whatever). If you get a measurable resistance then you don't have large enough cable or you've done a bad job putting the ends on the cable you do have. Note: don't measure from the battery post - measure cable clamp to cable clamp. If you've got resistance between post and clamp you just need to clean it up.

Here's a tip that actually works. You can locate high resistance connections using an infrared thermometer. Put a heavy draw on the system - start it a couple of times with the lights on. Then immediately shoot the temperatures of every connection. The hotter ones have higher resistance. In a perfect world they'll all be cold at the same temperature.

 

[John in OkieLand]

That IR gun will also work to find a Crimp Terminal that is going bad, IF, the load thru the terminal is high enough to generate heat.

 

[klhansen]

You can locate high resistance connections using an infrared thermometer.

Or you could look for the smoke drifting up like I've seen on a loose GPR connection. 😕 (not my truck.)

 

[James-Bob]

I thought the issue was trying to charge two batteries. I did a simple voltage test on my Toyhauler with 3 - 12 vdc batteries. They were setup from the factory as the unbalanced drawing shows. I checked the voltage on all three and the result was as shown in the drawing. I changed the Toyhauler battery cable wiring to balanced and sure enough all three were exactly the same voltage. It really isn't b.s. I also have a 50' Skyjack lift with 8 very very deep cycle batteries. They are factory wired as balanced. I was actually surprised someone does things right.

 

[bugman]

I thought the issue was trying to charge two batteries. I did a simple voltage test on my Toyhauler with 3 - 12 vdc batteries. They were setup from the factory as the unbalanced drawing shows. I checked the voltage on all three and the result was as shown in the drawing. I changed the Toyhauler battery cable wiring to balanced and sure enough all three were exactly the same voltage. It really isn't b.s. I also have a 50' Skyjack lift with 8 very very deep cycle batteries. They are factory wired as balanced. I was actually surprised someone does things right.

Your problem is that it is impracticable to wire dual batteries in a automotive situation this way.

You can do it in a RV is one thing, but your examples do not show where to connect the load such as you will have in a truck with dual batteries that depend on both batteries for starting.

 

[James-Bob]

I agree, that is why is said charge each battery one at a time. Putting a charger on one battery and thinking it will charge both the same will not work.

 

[bugman]

I agree, that is why is said charge each battery one at a time. Putting a charger on one battery and thinking it will charge both the same will not work.

It'll work quite well, it has for as long as he has owned the van. Remember we are talking automotive and not RV. As long as the battery cables are up to snuff both batteries will charge.

 

[James-Bob]

If you look at the diagram with 4 batteries, and remove two, then you have a vehicle battery layout. The four battery diagram may be confusing. I did the same battery voltage check on my F-350 diesel after running my batteries down with the radio. The batteries were about 2 months old from Ford. I put my charger on one battery, charged until the charger said OK ready to go...I then checked each battery voltages, the battery closest to the charger was charged to a little over 13 volts. The battery on the other side of the truck was just under 12 volts. A note here. I disconnected the battery cables at each battery before the voltage check after charging. There are ways to add voltage regulators to your multiple battery charging setup, to get perfect cell balance, but I think it is easier to just disconnect the battery I am charging, and keep the other battery connected until it's turn.

 

[James-Bob]

Here is a video that may explain better than I have. This video shows two batteries like in our autos and trucks.

 

[bugman]

Then explain this, how did the batteries charge from the factory in vehicles with dual batteries?

In all the applications that I have seen there is one battery that isn't connected directly to the alternator. and the ground on that battery is connected to the block of the engine in the most direct route, same as the battery that is connected closest to the alternator output.

Remember we are not just charging the batteries in a lab situation but in a vehicle.