Tow vehichle not charging the battery?

daisy1804 · 10-17-2011, 07:04 PM

How long does it take for my F 150 to charge my batteries? 2003 sunline 1950. I plug in, my lights and brakes are working fine, I thought I could charge up in a few minutes? Not the case? Couple hours? Thanks for the help. Is there a fuse just for the tow vehichle? In one of my compartments I have A little square box on the floor and it looks like it has something electrical in, any help on that too? Thanks everybody.

MOKID · 10-17-2011, 07:23 PM

We have a 2006 F150 and there is a 30A fuse located in the panel by the passengers feet. It is located at #106 in the fuse box. We had to purchase the fuse as it wasn't in the fuse panel when we purchased the truck.

The truck came with a Trailer Towing Package, Go figure. The way I understand it the fuse is needed in order to charge the Trailer Battery.

**JohnB** · 10-17-2011, 08:21 PM

Charging a TT battery off the tow vehicle can take a really long time and still not get it charged. The wire is so long that not much current passes that far.

If you are driving 8 to 12 hours and nothing much is on in the TT, the truck can replace some of the lost energy in the TT battery. But not a lot especially if the TT battery is drained down a lot.

However first the battery charge line in the truck 7 wire receptacle has to be working. On many Fords they use a relay in the truck charge line to the trailer. Meaning the truck has to be running for power to flow. And there is a fuse in the truck to protect it. The Ford fuse may be under the hood. On mine I have a fuse panel under the hood next to the master brake cylinder and one in the cab next to the parking brake. This must all be working first.

Then in the TT there is generally a 30 amp fuse on the campers that is in the line coming from the truck to the battery. That fuse must be good. For your year camper that box on the floor may have 2 fuses in it. Make sure both are OK.

If the TT battery is drained down a good ways, using a stand alone battery charger or the converter in the TT will get the battery back faster then the truck ever will. However once the battery is charged up, the truck can help maintain it. Pending the charger/converter you have and how drained the battery is, it could take all night long and then some to get the battery close to 90% charged. Then that last 10% to get to 100% charged may take a few days.

Hope this helps

John

pwb01 · 10-20-2011, 05:51 AM

I have an F150 and a T-1950. I've tested that from our favorite campsite a few times so that I'd know. My two batteries when at 20% to 30% leaving the campsite are at 100% after 90 minutes driving when I get home. You might check to make sure your pin is live on your vehicle as mentioned. I have in the past tried to charge the battery with the truck at an idle while sitting at a campsite and that just won't work.

As MOKID mentioned, my 2006 was the same way but in my case there was a plastic bag in the glove compartment with the fuse he mentioned and wire for the brake hookup.

**JohnB** · 10-20-2011, 07:31 PM

Hi Paul

Your truck charging sounds really good, almost too good or I'm miss understanding how your reading it. I'm not questioning your seeing what your seeing, just trying to figure out how this is accomplished as something is not adding up.

When you say your 2 batteries are at 20 to 30% and then 1 1/2 hours later both batteries are charged up to 100% by the truck, what are you using to determine the 20 to 30% and then the 100%?

Is this by the tank gage monitor panel, push button and see what red LED shows, or is this by a stand alone volt meter right at the battery?

I'm thinking this must be by the tank gage panel but even then I do not remember % numbers on the KIB panels.

Assuming you have 2 group 24 deep cycle batteries, maybe bigger, if this is by a volt meter at the battery bank 20% state of charge would be around 11.7 volts or really drained down. And if that is the case to charge 2 batteries all the way back to 100% full state of charge or up at 12.7 resting voltage takes days with a 10 amp stand alone battery charger or even a TT converter system.

I really do not "yet" know what the tank gage % number lines up with if yours has %.

This is a copy of the KIB panel info if this is what you where using.

They use C, G, F and L on the face plate which line up with the full words they list in the chart.

OK what did I miss? Pumping that high a amps in 90 minutes is more then one normally gets through a trailer charge wire.

Again not questioning you are seeing something that shows this, just trying to figure out how this can happen.

Thanks

John

pwb01 · 10-21-2011, 10:53 AM

Quote:

Originally Posted by JohnB

Hi Paul

When you say your 2 batteries are at 20 to 30% and then 1 1/2 hours later both batteries are charged up to 100% by the truck, what are you using to determine the 20 to 30% and then the 100%?

John,
I have two batteries mounted on the A frame and actually tie 2 more in if I camp for a week. Anyway, I have a battery condition meter that I bought at an auto parts store that reads the battery condition in percent of charge. Equating the meter to the panel, I see around 20% to 25% charge on my meter when the lights on my panel are down to one light.

When I see 20% on my meter as I leave the campsite, (one light lit on my panel) I see 100% on my meter when I get home 1.5 hours later indicating a full charge. The three lights on my panel indicate full charge also.

mainah · 10-21-2011, 03:37 PM

Most of the charge lines are fused 30 amp so that is the max charge you'll get in a perfect world. Now the not so perfect world the length of wire and voltage drop so that may bring your charge rate down to maybe 20 amps, so in an 1 1/2 hour you'll get a 30 amp charge. If the lights on your panel only have 4 lights there can be a pretty big error as much as 25% with one on and the other off so I'm guessing your batteries have a better charge then your lights are telling you if the truck charge line is bring them back to full charge. A good volt meter right at the batteries will tell you where you stand there are several web sights that have voltage to charge level charts.

**JohnB** · 10-25-2011, 08:14 PM

Quote:

Originally Posted by pwb01

John,
I have two batteries mounted on the A frame and actually tie 2 more in if I camp for a week. Anyway, I have a battery condition meter that I bought at an auto parts store that reads the battery condition in percent of charge. Equating the meter to the panel, I see around 20% to 25% charge on my meter when the lights on my panel are down to one light.

When I see 20% on my meter as I leave the campsite, (one light lit on my panel) I see 100% on my meter when I get home 1.5 hours later indicating a full charge. The three lights on my panel indicate full charge also.

Hi Paul

Sorry so long getting back to. Was out camping and then work was busy.

OK now I see how you are seeing this. A few thoughts as to what may be going on. And possibly tricking the meters.

See this chart form Trojan Battery. go to bottom of page Trojan Battery Company

The Tank panel indicators are really not accurate

I think your year tank panel looks like this

If you look at the standing open circuit voltage on the Trojan chart lets see how that lines up with the tank panel.

The "Charge" indicator (all 4 red lights) lists the voltage can be 12.7 to 12.85. And Trojan says "open circuit voltage" can be 12.73 volts and is 100% state of charge (SOC). In this case the tank panel and the battery manufacture agree if the TT battery has been resting for 8 to 10 hours not being used much.

Now the "Good" indicator (3 red lights) lists the voltage can be 12.10 to 12.15. Trojan says 12.10 open circuit voltage is 50% SOC. Or the battery is 1/2 drained and the tank monitor calls it good. That is very miss leading.

The "Fair" indicator (2 red lights) lists the voltage can be 11.60 to 11.65. Trojan says 11.66 open circuit voltage is 20% SOC. For many, draining a battery down that far is not good for longevity of the battery, but the tank panel says fair.

The "Low" indicator (1 red light) Does not list how far the voltage is. Trojan says 11.51 is 10% or close to totally discharged.

I practice the 50% SOC charge guideline as the point where the battery needs to be recharged. This would be in the 12.10 volt area of a resting battery. By only draining down to 50% and then recharging, long term battery life can be extended if this is done on a routine basis.

OK now directly to what you are seeing. By any chance do you have a volt meter? It would be good to know what the % levels of your autoparts store meter considers what actual voltage.

Since the tank panel is one light lit and the auto part store says 20%, well the battery may be drained down to a real 20% SOC charge area that is around 11.66 volt area or maybe lower. It would be discharged pretty good. So we will say that number/reading may be fairly accurate.

Your truck charge line for sure must be working as you are getting some level of charge in the battery. The charge voltage I'm going to estimate is at least 13.6 volts maybe more. And if your doing this for an hour and a half you have put a level of charge in the battery. Just I do not see it being a full 100%. Here is why I say this.

When charging a battery at elevated voltage, the 13.6 volts is in that range, the battery voltage rises to meet it. They call this a surface charge. When you unhook a battery from a charger or your truck it may well read 13.5 or so. That surface charge is not the real state of charge voltage. It is artificially pumped up that high from the charging process. If you wait 8 to 10 hours and do not charge any further or use the battery that surface charge will be lost and the true'er voltage will show up to show the actual SOC. We call that the resting voltage or the open circuit voltage. You really cannot tell the SOC of a wet cell battery by voltage immediately after charging.

So, your tank panel would be seeing this high 13.6 volts and say 100%. Your autotester is seeing the same thing and tricking it to 100%.

If you have 2, group 24 batteries I'll guess they are 85 amp hour rated each. So that is 170 amp hours of total capacity. If they where drained to 20% that would leave 34 amp hours left. Or that you have to recharge 136 amps for 1 hour to get them back to 100%. There is no way I can see how the truck charge line can put 136 amps into the battery in one hour.

Even our on board converters with 3 stage chargers that boost to high voltage (14.4 vdc) only take the battery to 90% SOC and then it takes a really long time to jam that last 10% in as the battery resistance is then so high. Over night in most cases.

I "think" the elevated surface charge may be tricking your tester and the tank panel. To test this concept, next time you try this do the same thing as you are now. Test before, tow 1 1/2 hours then test and then after 10 hours of no battery use, test again and see what you get.

I'll "guess" you may be putting 10 amps through the charge line to those 2 batteries. In 1.5 hours that puts 15 amp hours of power back into where you started with a 20% charged battery bank (35 amp hours worth) which would come out around 29% SOC. (50 amp hours worth). Even if your putting 15 amps in the truck charge lines only about 33% SOC in 1.5 hours

I'm curious if this test comes out this way. I'm always open to learning more on this battery deal from what folks see. Some day if we end up at a M & G in the same CG lets try this test. I have a clamp on DC amp probe and we can measure what your truck charging line is putting in the battery. I'll have to try that myself on my own truck. This will help add actual data to the theory.

Hope this helps

John