Thor Forums

[FW28z]

If you go AGM for your coach batteries, make sure the charger in your rig will support AGM, or you could end up damaging them.

For AGM, it requires a lower charge current when the battery goes into the overcharge state. This is not generally an issue with an engine battery as it is never in the overcharge state due to the load from the engine.

However, for the house battery, it might go into an overcharge state when the coach is just sitting there with a charger running.

So you may need to possibly out your charger, if the one you have won't do AGM.

Most of my experience comes from when I had boats. My last boat had three batteries (two engines and house). Our boat was located on Lake Michigan, and on that lake, you could die if your equipment is faulty, and good batteries are a big part of that. I sure didn't want to get in to a storm and have the batteries conk out in the middle of it.

For safety reasons, I always changed my batteries every three seasons, whether it needed it or not. The batteries I used were around $100 each, so $100 per year.

AGM batteries were about twice the initial cost, and they could go 6 years, but the per-year cost was the same.

The only real difference in the two (other than having to buy an AGM-specific charger) is AGM could be stored a lot longer without damage. AGM also typically has a lower internal resistance, so they can deliver energy efficiently.

So AGM, while they are better, the cost differential was not much different in my case. And premium wet-cells these days have really improved a lot.

Even so, in Michigan, we stored the boat from Oct to Apr; during that time, there was no charge on the battery. But the batteries also had a disconnect switch so they were completely removed from any loads.

In the spring, I found that the batteries still had a charge to them, and about 4 hours on the charger was enough to bring them back up.

So the way I always looked at is the cost-differential for my boats between the two batteries was about the same per year, which was a wash.

And since I did not have an AGM capable charger, a good marine three bank charger would have cost $600 or more to install in the boat.

While this does not make me an expert at batteries, I have learned how well they hold up under storage conditions.

The batteries of choice for me were Interstate... which perhaps are better than Harris. In reality, there are only a few true battery manufacturers. Don't know much about Harris, but I would not be surprised if their batteries are actually made by someone else.

My 2011 coach still has two Harris batteries for the coach. They have already survived four seasons, so I probably need to think about replacing them next year. When the time comes, I will use Interstate batteries as I have had good luck with them in my boats.