Which battery tender is better 800mha or 3a

[HappyCamper1]

....looking at our idle Roadtrek I finally purchased a battery tender to deal with the long cold months ahead. I got a 3 amp instead of the 800mha...Good choice or not.. I figured the 3 amp charges quicker but is that good for the battery ?? Like I said this RV will be idle for months, and does the battery emit gasses inside the van during charging? Thanks

[avanti]

Better to just disconnect the battery. The self-discharge rate of modern batteries is insignificant over the period of a winter. Just make sure the batteries are fully-charged when you put them to sleep.

[mkguitar]

Alarms and other systems can draw down the battery when parked

when I lived in Canadia, I might pull batteries over the winter and put them on the bench
I live in AZ now, batteries stay in vehicles.

My Chev has an issue with the electronics where it will draw down the battery when parked. I have a battery tender on a timer which goes on a couple of hours each night, I let the Tender decide to charge or float

electrons can travel through dirt on the outside of the casing when damp. Helps to keep the battery casing cleaned off.

my coach battery is in a drawer, so easy for me to clean
I connect the tender to that every once in a while too

My Chev ECM is 'cleared' when the battery is disconnected.
When started it may not idle well and runs rough until the ECM has responded to sensor inputs and made correction


any trickle charger I've seen will calculate what to do, charge or maintain- I have a few from different manufacturers, most of them are less than 2 amps


mike

[nicaland]

I have been using the Battery Tender Junior for many years (750mH) on everything from very small motorcycle batteries and all the way up to 210 AH flooded lead acid and AGM's and have never lost a battery when connected to it for very long periods of time.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Check out the Amazon ratings on these little beauties and you will see that I'm not the only one that loves these things. Pricing has gone up quite a bit but they are still cheap insurance (currently $39, maybe cheper elsewhere). They are advertised as having a true 4 step auto charging program, and I think they really do. They also make a 800mH charger that is advertised as being suitable for Lithium batteries as well.

[alaskasail]

I have been putting tenders on my stable and a boat for years with varying degrees of success and now I read here and in other forums that just unhooking the batteries is enough. There's must be a lot of discussion/opinion about this somewhere. I'd like to see some serious data, but the variables are staggering. Not only for the tender, but for the batteries and the environment they endure.

[avanti]

Originally Posted by alaskasail

I have been putting tenders on my stable and a boat for years with varying degrees of success and now I read here and in other forums that just unhooking the batteries is enough. There's must be a lot of discussion/opinion about this somewhere. I'd like to see some serious data, but the variables are staggering. Not only for the tender, but for the batteries and the environment they endure.

What kind of data would be helpful to you?

--The battery manufacturers usually publish self-discharge times. Modern FLA batteries are almost never more than 3%/month, often much less.

--I had a vehicle stored outdoors at a vacation home for 18 months during the pandemic, with a battery disconnect switch on the starter battery. When I finally rescued it, it started right up.

There is NO reason for a battery tender, unless you wish to leave your parasitic loads connected. It is just that most people don't actually fully-disconnect their batteries. You need to air-gap the ground wire, and you will be fine for a very long time.

As I said before, just make sure you are fully-charged when you put the rig to sleep.

[peteco]

Originally Posted by avanti

What kind of data would be helpful to you?

--The battery manufacturers usually publish self-discharge times. Modern FLA batteries are almost never more than 3%/month, often much less.

--I had a vehicle stored outdoors at a vacation home for 18 months during the pandemic, with a battery disconnect switch on the starter battery. When I finally rescued it, it started right up.

There is NO reason for a battery tender, unless you wish to leave your parasitic loads connected. It is just that most people don't actually fully-disconnect their batteries. You need to air-gap the ground wire, and you will be fine for a very long time.

As I said before, just make sure you are fully-charged when you put the rig to sleep.

Yes, the biggest long-term killer is the parasitic loads. They seem to come and go on my 2006 Roadtrek for some reason. Fortunately I drive it at least once a week. I did leave it for 10 days and came back to a low battery. If I have to leave it for an extended period I hook up to shore power. That is easier than having to reprogram the radio if I disconnect the battery.

[booster]

A lot of things can affect the self discharge rate in lead acid, both AGM and wet cells.


Here is what Trojan says about storing wet cells and shows an actual self discharge rate vs time for one of their true deep cycle batteries. This is a technical white paper so should be less sales dept influenced.


https://www.trojanbattery.com/pdf/WP...orage_0512.pdf


I have found the latest generations of starting batteries do not self discharge as fast as they used to in general but really never checked the rate (on most you can only check voltage because you can't get to the water to do specific gravity.


There is probably similar information out there for AGM batteries also, but all this will vary some brand to brand because they use different chemistry mixes.

[markopolo]

Originally Posted by HappyCamper1

....looking at our idle Roadtrek I finally purchased a battery tender to deal with the long cold months ahead. I got a 3 amp instead of the 800mha...Good choice or not.. I figured the 3 amp charges quicker but is that good for the battery ?? Like I said this RV will be idle for months, and does the battery emit gasses inside the van during charging? Thanks

3A or 800mA are both suitable for what you want. Neither are fast chargers for the size of your chassis battery or coach battery(ies). Current will taper to just a trickle once in float mode. The 3A could also come in handy if you any other small 12V batteries to take of.

If your coach has a Sure-Power Separator then the 3A is the better choice because those Separators use about 1.5A just holding the coil closed.

If the batteries are outside of the cabin/coach area then you don't have to be concerned about outgassing inside the van. If there is a battery inside the cabin/coach area then is likely an AGM and outgassing would be unlikely to occur during normal charging. The voltage is lower in Float or Maintenance mode and that further reduces the chance of any outgassing.