KZB2 650 wrote: Hey Ed and DOHC if you guys could get a chance could you check and see what you get for a reading after a few days or longer. Thanks.
I checked the two batteries I have charging. The first, using the newer "Battery Tender High Efficiency Junior", read 13.04 V. The second, a standard "Battery Tender Junior", read 13.09 V. Both of these had green lights, which I believe is float mode.
Based on everything I've read, leaving the Battery Tender Jr. connected forever should keep a battery healthy. That assumes three things. The battery started out healthy, the temperature in roughly "room temp" (the "Jr" is not temperature compensated), and the battery has enough water.
Regarding enough water, I've sworn off unsealed batteries. I've had too many bikes and cars where the paint was eaten off by acid vapors. So all my batteries are sealed AGM. Leaving an unsealed battery on a float charger may make the water evaporate faster if you have an open vent, like the traditional motorcycle batteries with the drain tube. I don't know. But the article I linked to said it's critical to keep the plates flooded. So that would be something to consider.
Regarding starting with a healthy battery, when I went to check the voltage today I noticed that the battery from my son's power-wheels car was only at around 12.5V while on the charger. The charger was still flashing red after more than day. The battery was also slightly warm to the touch. This battery is clearly bad, and I'll have to get a new one. It probably has a failed cell. Since the voltage never reached the float threshold, the charger kept putting out the full charge current (which is still pretty small). But since the battery is bad, it was not storing any of that energy but was instead turning it into heat, which was probably doing more damage to the battery. This is an example of a continuous charger being a bad thing.
As loudhvx said, it's fine to leave them off the charger entirely for some period of time. I do this often as I have more batteries than chargers. You just need to charge it back up before it gets too low. That article I linked to says "Recharge every 6 months while in storage; AGM every 6–12 months." But if you observe the voltage dropping faster, you should charge it.
Also, if you do only connect to the charger occasionally, you don't have to use your 1 amp charger to bring it back up to full. The tender will bring it up, it will just take longer. But then you could leave it on the tender for a 2-3 days before disconnecting it, and not have to worry about coming back to it within 5 hours.
loudhvx wrote: Float charging is active charging. After charging the battery will slowly drop down to a plateau somewhere between 12.5 and 12.9 depending on temp and other factors. Then will very slowly drop from there over a period of weeks or months.
A smart tender should shut off until the battery falls below a set threshold or after a set amount of time.
Based on the articles I linked to, that's not how lead acid float chargers typically work. Lithium batteries for sure shut off after the float period, but lead acid charger seem to typically actively maintain the float voltage forever. That's definitely how the typical computer UPS works. And apparently how the Battery Tender Jr. works, based on their FAQ.