Charging Amps

[fernlane]

I keep reading that battery chargers ought to have at least 10% of the battery's capacity, and ideally more like 20-25%. In my case that number would about 8 amps minimally but up to about 20 amps. I also have read that this capacity is more important if the battery is more than 80% discharged, that fewer amps are necessary for a smaller discharge level.

I'm still using the Battery Tender charger that came with the 550 back in 2014. It works fine and is well-protected now that Camp Inn moved it to the rear of the galley storage area when we were in for a repair from being rear-ended. That charger only puts out five amps, however.

I just got about six years out of a Trojan group 24 deep cycle. In its early years I didn't have the ctek dc-dc installed so I undoubtedly shortened its life by frequent inadequate charging.

I'd just as soon not replace a functioning charger but if it would noticeably extend my battery life I probably would. Those Victron smart chargers are pretty appealing.

So my question is how big a deal is having the "ideal" charging capacity? How much life am I taking off the battery by continuing to use the five amp Battery Tender?

 

[Sweeney]

Why do you think 5amp charging would damage your battery? As long as you don't exceed the maximum you will be OK. I'll defer to any battery experts here, but I've never seen a "minimum" charge rate...as long as you're not taking out more pixies than you are putting back, and depleat the battery --- which I've done several times :\

 

[rotus8]

I would say it depends on your use case. In the most usual case, the built in charger is almost always only used to maintain a mostly charged battery. The battery is charged when you tow, the trailer is parked with a charged battery, and the charger is plugged in to keep the battery in good shape for the next time you take it out.

At least the way we use our trailer, it is at camp and the battery is used for whatever needs, then on the way to the next spot or home the TV charges is up again. I use a solar panel in camp when I can but that simply extends the amount of time we have before needing to hook up to the tow. The car's alternator, especially with a DC-DC will get the battery full in short order.

If you camp at a place with shore power, the little on-board charger is likely also adequate unless you are heavily using electricity for something; it's unlikely that on the average you will use more than it can keep the battery happy and you can camp for as long as you like.

 

[fernlane]

I would say it depends on your use case. In the most usual case, the built in charger is almost always only used to maintain a mostly charged battery. The battery is charged when you tow, the trailer is parked with a charged battery, and the charger is plugged in to keep the battery in good shape for the next time you take it out.

At least the way we use our trailer, it is at camp and the battery is used for whatever needs, then on the way to the next spot or home the TV charges is up again. I use a solar panel in camp when I can but that simply extends the amount of time we have before needing to hook up to the tow. The car's alternator, especially with a DC-DC will get the battery full in short order.

If you camp at a place with shore power, the little on-board charger is likely also adequate unless you are heavily using electricity for something; it's unlikely that on the average you will use more than it can keep the battery happy and you can camp for as long as you like.

I agree with all this, and pretty much with what Sweeney says as well. I'm just curious as to whether there's a real, scientific, i.e. measurable, effect on the battery from using a charger that's less than optimally sized. I've read in Victron's literature, for instance, that they recommend a charger with something like 20% of the capacity of the battery. That's not the only place I've read that recommendation.
This is really just a curiosity. It doesn't worry me much for all the reasons that rotus laid out. The ctek and the solar panel will do most of the charging when we're on the road.