80 Series charging travel trailer AGM batteries

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I have read that the charging system on the 80's can mess up AGM batteries.

My question is, will that also be the case if my travel trailer has AGM batteries or will the 7 pin adapter be enough of a buffer?

1990 HDJ81 1HDT

Thanks in advance.
 
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Unfortunately, I cannot find the thread that i read just yesterday, but folks were mentioning that the alternators on the older vehicles were not compatable with the AGM batteries. They mentioned that the newer alternators from Tundras or Sequoias were okay, but not the older Land Cruisers.

I am not the expert, just trying to figure out if I will be okay towing my trailer which has AGM batteries. I do use a 7 pin connector.
 
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AGM batteries prefer slightly different charging voltage than flooded, but it's minor. I've been running AGM batteries on my old motorcycles, which came with flooded batteries, with no problems.

I'm even running a flooded primary battery and an AGM auxiliary battery in my Land Cruiser. It's supposed to be a no-no, but it's been fine for several years. I ran that way on the original alternator, and now using a Sequoia 150 amp alternator.

A couple of times per year, I'll unplug my battery isolator controller and treat each battery with the Harbor Freight battery charger/conditioner. If I don't unplug the isolator controller, it will bridge the two batteries as soon as it sees charging voltage.

63350_I.jpg
 

jellis

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Probably depends on the batteries, but Odyssey's at least want 14.7V from the alternator which is presumably higher than stock which should be more like 14.2-14.4. Apparently overall cycle life can be cut in half by the seemingly-small difference, but perhaps more importantly it makes a HUGE difference to power capacity (running a fridge for 58 hours instead of 8 hours), see the quote from another thread in my post with all the details on this here:

There's a drop-in GM fuse diode (ghetto drop-in, it's a mini not full size ATC fuse) which I have installed but not yet measured the voltage difference, I'll report back when I get a chance to fuss with it--hopefully in the next few days.

I suppose the amperage isn't a big limiting concern thru that connector to the trailer since most chargers aren't huge amperage anyway? EDIT: What circuit did you tap into for the 12V supply? I don't recall when I installed my 7 pin setup what I did...hmmm.....
 
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Been using AGM Optimas, Sears Diehard Gold, X2 Power in various cruisers for over 30 years. Never an issue keeping them charged or dying prematurely. Used with a wide variety of alternators too from stock, to Leece Neville, Delco, and Sequoia. No mods to the alternators.
 
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Your best bet is to install some version of a DC to DC charger on the camper. Feed the charger with power from the Cruiser through the 7-pin and it will output the proper charging voltage to the AGM batteries. Or better yet add a simple 100w or so solar panel with a solar charge controller and let them stay charged through that.
Straight charging the batteries from the alternator on the cruiser will not harm the batteries though.
I've also been running AGM batteries for years with no problems. The alternator may not put out quite high enough voltage to completely top off the battery but its close. I usually try to connect my batteries to a charger on a regular basis to bring them up to full with the correct voltage, and then have them float at the proper voltage.
 
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Your best bet is to install some version of a DC to DC charger on the camper. Feed the charger with power from the Cruiser through the 7-pin and it will output the proper charging voltage to the AGM batteries. Or better yet add a simple 100w or so solar panel with a solar charge controller and let them stay charged through that.
Straight charging the batteries from the alternator on the cruiser will not harm the batteries though.
I've also been running AGM batteries for years with no problems. The alternator may not put out quite high enough voltage to completely top off the battery but its close. I usually try to connect my batteries to a charger on a regular basis to bring them up to full with the correct voltage, and then have them float at the proper voltage.
Thanks!

Our trailer does have solar panels which charge the batteries and I also periodically use a battery charger to ensure both batteries are topped off.

Thanks again, and I want to thank everyone who has shared their knowledge in this regard. You guys are awesome!
 
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Denver Colorado
I have read that the charging system on the 80's can mess up AGM batteries.

My question is, will that also be the case if my travel trailer has AGM batteries or will the 7 pin adapter be enough of a buffer?

1990 HDJ81 1HDT

Thanks in advance.
I know your question is about charging AGM batteries but do you need to run AGM batteries in your trailer? I use a group 31 flooded marine battery in my trailer and it has been great. No special charging at all, just leave it on a battery tender through the winter when not using.
 

jellis

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Since you have panels that fully charge the batteries in addition to the alternator, this is entirely a moot point. The solar will top-up appropriately. Basically you've already addressed your concern.

The stock alternator's lower-voltage configuration as the only charging option will leave a significant amount of amp-hour capacity on the table with AGMs, and according to Odyssey's test data will result in a significant reduction in the number of deep-discharge cycles the battery can tolerate before losing capacity. If you are simply using an AGM as a starter battery then both of these concerns are totally irrelevant and you won't notice any difference at all or care either way. But if you're interested in running a fridge for extended periods, it's absolutely worth paying attention to especially since the "fix" can be as simple as $10 and 2 minutes and I spent over $700 on my batteries.
 

jellis

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I finally got a chance to check voltages, and it's weird. I have a 1HDT with dual batteries but that shouldn't matter?!?

With everything disconnected on the LH battery including the alternator, my alternator will output 14.8V. If I reconnect the fusible link on that side and disconnect the alternator (so now all electronic circuits are connected between both batteries, but no charge input from the alternator), the alternator now outputs 14.35-14.4V. This does NOT change, ever, regardless of what's happening with the 7.5A Charge fuse even if no fuse is in there at all. If I measure like that video above, the measurement never changes no matter what I do to the fuse.

The fuse does not seem to control alternator output voltage but instead seems to control nominal ambient voltage to the rest of the truck. With no fuse in there (open circuit), I get 13.45V on the + terminal and 12.9V on the - terminal of the fuse. With a normal fuse in there, both sides drop to 12.93V. With my GM diode, + 13.25V and - 12.9V. With a huge 22MOhm resistor or 3 1N914 diodes in series, it acts as if there's an open circuit and maxed out at + 13.45V and - 12.9V. So as resistance goes up across the terminals the voltage does go up, but it has no affect on my alternator output voltage whatsoever.

So, I'm not sure what to think. Basically the option which yields the greatest voltage increase is simply to leave the fuse empty. Is something wrong with the regulator on my alternator or what?!?

I do have an LED in my charge light instead of a normal bulb. I think this can screw with the system as it expects some resistance there, although I think that's mainly on startup (my dash Christmas lights all stay on until I rev it and hit 12.8V, I think this is because the LED has such a lower resistance than a standard bulb so it takes a higher voltage to hit the cutoff threshold).
 
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my dash Christmas lights all stay on until I rev it and hit 12.8V
This seems suspicious to me, but I've been running the Sequoia alternator and Photoman bracket for so long that I don't remember the idle voltage with the stock alternator. Also, I have zero experience with the 1HDT.

What's your voltage at idle?

Here's an old thread discussing idle voltage:

 

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