Charge up

[Hittheroad]

I think I have finally understood a battery problem I have been working on for several months and I wonder if anyone else has had this problem.

This past summer I traded in my 1999 Tacoma for a 2011. Since then I have found the camper battery never gets fully charged - that is until today.

I have learned that AGM batteries may require 12.8 volts or higher to get full charge.
I have found that the voltage put out by the alternator is usually less than 13 volts (not really enough)
The voltage put out by the AC hook up is similar (not really enough)
Today I installed a new solar panel and am getting about 14 volts. Charging is going well.

My conclusion is that the old Tacoma had a higher voltage output and could charge my AGM but the new one has a lower maximum voltage and only gives a partial charge.

Does this fit any one else's experience?

 

[leadsled9]

I think there is a problem with your 120 volt system. When I plug into 120 volt socket at home....there is plenty of voltage (14.5 v) to charge my two group 31 Diehard AGM batteries. The output of your trucks alternator needs to be checked too. It should be putting out 14+ volts while at highway rpms.

You might want to check out this link:
http://www.wanderthewest.com/forum/index.php?/topic/2884/

It might be worth a try since it's so cheap.

 

[bsharp007]

Not at all, Ive had no problem with my coach battery getting charged either by the truck alternator, 120v or solar.



I think I have finally understood a battery problem I have been working on for several months and I wonder if anyone else has had this problem.

This past summer I traded in my 1999 Tacoma for a 2011. Since then I have found the camper battery never gets fully charged - that is until today.

I have learned that AGM batteries may require 12.8 volts or higher to get full charge.
I have found that the voltage put out by the alternator is usually less than 13 volts (not really enough)
The voltage put out by the AC hook up is similar (not really enough)
Today I installed a new solar panel and am getting about 14 volts. Charging is going well.

My conclusion is that the old Tacoma had a higher voltage output and could charge my AGM but the new one has a lower maximum voltage and only gives a partial charge.

Does this fit any one else's experience?

 

[Hittheroad]

I think there is a problem with your 120 volt system. When I plug into 120 volt socket at home....there is plenty of voltage (14.5 v) to charge my two group 31 Diehard AGM batteries. The output of your trucks alternator needs to be checked too. It should be putting out 14+ volts while at highway rpms.

You might want to check out this link:
http://www.wanderthewest.com/forum/index.php?/topic/2884/

It might be worth a try since it's so cheap.


Any idea where I might be losing a volt in the AC system? Seems an odd thing to lose.
I will check out the IQ4 but I think the controller I have with the solar may already cover the need.
Thanks for telling me that I should be getting 14.5v out of both the alternator and the AC - It is what I thought I should get but have not yet managed to find.
Fortunately the solar works great so I may just depend on that - until I visit Seattle.

 

[pods8]

I have learned that AGM batteries may require 12.8 volts or higher to get full charge.


More than that, most want 14.4+ for bulk charging and 13.7V float charge. You need the higher voltage to actually drive the current in.

 

[White Dog]

You might want to check the gauge of the charge wire leading to your camper batteries. If you are using your stock 7-pin on the back bumper, the current has to go from the alternator to the back of the truck then forward to the batteries. With a small wire, 12 VDC can have significant drop in this distance if the wire is too small.

 

[leadsled9]

Any idea where I might be losing a volt in the AC system?


First place I'd check would be the connections to the camper battery. Are they clean? Is the battery in good condition?

I don't think it is a wire size problem because your old truck used to charge the camper ok.

 

[Hittheroad]

First place I'd check would be the connections to the camper battery. Are they clean? Is the battery in good condition?

I don't think it is a wire size problem because your old truck used to charge the camper ok.


I am just back from a visit to Toyota for my 5,000 mile service. They say the charging system is working as it should but they agree that I am not getting 14.5 volts.
They indicate I may need the alternator that comes with the towing package to handle two batteries. It is likely all BS but the message I want to get out is that the newer Tacos may not be able to handle AGM batteries unless you upgrade to the point that you would be better off with a Tundra.
The real story is get Solar and forget the alternator.

 

[pods8]

I am just back from a visit to Toyota for my 5,000 mile service. They say the charging system is working as it should but they agree that I am not getting 14.5 volts.
They indicate I may need the alternator that comes with the towing package to handle two batteries.


What voltage were you getting?

I call BS on the bigger alt needed unless you're drawing a lot off it, which is doubtful for our setups. Could easily call their bluff by disconnecting the second battery and see if the voltage goes up.

Personally I'd be inclined to verify what the factory desired charge voltage is and go back to the dealer on warranty if it's quite a bit off.

 

[Hittheroad]

What voltage were you getting?

I call BS on the bigger alt needed unless you're drawing a lot off it, which is doubtful for our setups. Could easily call their bluff by disconnecting the second battery and see if the voltage goes up.

Personally I'd be inclined to verify what the factory desired charge voltage is and go back to the dealer on warranty if it's quite a bit off.


I think it is the truck AC that has been eating a volt. Today I was getting 13v and then click, less belt noise and 14v at idle. I need to do some more tests to be sure because even 14 is not what is really needed.
But many thanks for all your input. It helps to push me to get to the bottom of this.

 

[pods8]

Yeah the AC shouldn't be bogging down the engine/alt that much, keep working on it and make sure your truck is operating right while it is still under warranty...

 

[White Dog]

If your dealer is correct, the voltage at your engine battery and your camper battery should be the same and low with both batteries connected. The voltage at your engine battery should go up significantly as you disconnect the camper battery. If the voltage is high at the engine battery and low at the camper battery, then the problem is likely in the wiring someplace (loose or poor connector, wire too small a gauge, etc.). If you plug the camper into the 7-pin connector on the back of the truck, disconnect the camper plug and check the voltage at the truck plug. It is pin #4 Trailer plug wiring" It should be the same as the voltage at the battery. If it is low, then the problem is in the truck. If it is the same as the battery, then the problem is probably in the camper somewhere or your dealer is right.

Good luck. Electrical issues can be challenging.

 

[pods8]

If your dealer is correct, the voltage at your engine battery and your camper battery should be the same and low with both batteries connected. The voltage at your engine battery should go up significantly as you disconnect the camper battery.


I wouldn't say the voltage SHOULD be low, it could be if you are overwhelming the charging system but if the truck has been running for a good amount of time I doubt that is the case, but as mentioned unplugging the camper would easily confirm one way or another.

 

[K7MDL]

The A/C turning on could be lowering the engine RPM just enough to cause the alternator voltage output to drop. Make you raise the RPM and retest the voltage, AC running and also not running.

 

[JohnF]

Starting from the original post:

Where are you measuring your voltage? At the camper battery? Does the AC (alt. current, not air conditioner) charge circuit and the truck alternator charge circuit share leads to the camper battery? When you added solar did it get dedicated leads to the battery?

It is curious that you have sudden onset of the same problem from two different sources.

Now the alternator sub-thread:
Ok, for this I assume you are testing voltage at the truck battery. Like this. How much electrical stuff are you running? The AC (air this time) shouldn't drop idle that much, in fact, on some modern cars the computer will raise idle RPM just a bit to run the AC; but it might just like K7MDL said. Also, the AC clutch puts a (what should be) small electrical load, make sure it is small. Check for resistance in the b lead to the alternator or that you just have a bad battery.

I'm with pods8, pursue this and make sure you are happy before the warranty is up.

Right now this looks to me like two different issues. For the first I am betting that you'll come back and tell us that you found a bad ground (screw to the frame, corroded joint, ...) in the shared 110v/12v part of the circuit. For the alternator it will be: turning off the bitch'n amped up stereo

, b lead or bad battery, getting the dealer to replace what appears to be a weak performing alternator, or (and this happens) because you've been jiggling and wiggling and reconnecting stuff - it starts working and we'll never really know why.

 

[Hittheroad]

Starting from the original post:

Where are you measuring your voltage? At the camper battery? Does the AC (alt. current, not air conditioner) charge circuit and the truck alternator charge circuit share leads to the camper battery? When you added solar did it get dedicated leads to the battery?

It is curious that you have sudden onset of the same problem from two different sources.

Now the alternator sub-thread:
Ok, for this I assume you are testing voltage at the truck battery. Like this. How much electrical stuff are you running? The AC (air this time) shouldn't drop idle that much, in fact, on some modern cars the computer will raise idle RPM just a bit to run the AC; but it might just like K7MDL said. Also, the AC clutch puts a (what should be) small electrical load, make sure it is small. Check for resistance in the b lead to the alternator or that you just have a bad battery.

I'm with pods8, pursue this and make sure you are happy before the warranty is up.

Right now this looks to me like two different issues. For the first I am betting that you'll come back and tell us that you found a bad ground (screw to the frame, corroded joint, ...) in the shared 110v/12v part of the circuit. For the alternator it will be: turning off the bitch'n amped up stereo

, b lead or bad battery, getting the dealer to replace what appears to be a weak performing alternator, or (and this happens) because you've been jiggling and wiggling and reconnecting stuff - it starts working and we'll never really know why.


I just want to thank everyone for all this very useful information. If only car dealers were half as concerned and useful.
It may take me a while to get around to performing all the tests on the camper but as the temperature drops I will see if the alternator gets more lively. I was not aware of temperature compensated alternators. Could it be that all my problems are a result of Global Warming. Its December and we have not had the kind of temperatures that demand full voltage charging.
Again many thanks to all of you.

 

[pods8]

I just want to thank everyone for all this very useful information. If only car dealers were half as concerned and useful.
It may take me a while to get around to performing all the tests on the camper but as the temperature drops I will see if the alternator gets more lively. I was not aware of temperature compensated alternators. Could it be that all my problems are a result of Global Warming. Its December and we have not had the kind of temperatures that demand full voltage charging.
Again many thanks to all of you.


Dealers aren't in the buisness to do more work than they get on the hook for. Also finding someone who can change parts in easy, finding someone who can find the cause of a problem is a lot harder, the quality of the latter skill in mechanics can vary a lot.

I don't think a temp compensation has any role in what we're talking about here by the way, there is still a bare minimum that you should be getting out of that alt. I can see being around 14.0V while at idle but when the rpms are up during driving it should be more like 14.4V. Other than a slow idle you should never see it down in the 13s.