# Battery tender



## Rumblejohn (Jul 22, 2019)

Is a Batterytender Plus or Junior inadequate for a group 27 deep cycle lead acid battery? I'm not in a big hurry, but I want the batteries to last as long as possible (I'm a cheap old fart). Any opinions and/or recommendations are welcome.

John


----------



## Matt193 (Jul 23, 2019)

I use either a solar charger or a 2A charger on mine and it works well.


----------



## DaleH (Jul 23, 2019)

For pure charging a depleted battery I say ‘no’, use a good charger w/ more amps. ‘Tickling’ batteries can do more harm than good ...

The difference between a ‘trickle charger’ and a ‘battery tender’ is that a trickle charger constantly applies a charge, whether the battery is fully charged or not. Whereas when a battery tender senses the voltage has dropped, it will resume charging. Because of this a battery tender can be left connected indefinitely. (But I personally never do that ... )


----------



## Rumblejohn (Jul 23, 2019)

Thanks for the replies. 
Should I be concerned about using an old analog 10 amp charger to bring the battery up to near full charge then switch to battery tender to finish? The old Schumacher charger I have drops amperage as it nears full charge, but it has a timer. It never was intended to run full time.

John


----------



## DaleH (Jul 23, 2019)

That is what I do with my even more modern charger that has a fully automatic mode. The charger makers also concerned about causing a fire when in automatic mode, so they tend to shut off somewhat earlier than they should for the absolute best charging results.

When ‘done’ in auto mode, I switch it to manual/low amp charge and give it another hour or two, but I set alarms, or my phone or anything else ... so as NOT to forget.


----------



## Rumblejohn (Jul 23, 2019)

DaleH said:


> That is what I do with my even more modern charger that has a fully automatic mode. The charger makers also concerned about causing a fire when in automatic mode, so they tend to shut off somewhat earlier than they should for the absolute best charging results.
> 
> When ‘done’ in auto mode, I switch it to manual/low amp charge and give it another hour or two, but I set alarms, or my phone or anything else ... so as NOT to forget.



Me too on the phone reminder, how did we survive without them. Sometimes I have to ask Siri what was I thinking.

John


----------



## DaleH (Jul 23, 2019)

What I've been doing lately ... is I'll put the battery on manual/low amp charge for an hour or two before I plan to go to bed and I'll throw the nice box I have for the charger on my pillow. So unless [insert actress of your choice] shows up and coaxes me onto the couch ... I'm pretty much guaranteed to make sure I shut that battery charger off!


----------



## gnappi (Jul 26, 2019)

I have a two bank battery tender I used for a couple of years but pretty much stopped using it for a Noco Genius Gen 3 here's my take on the BT brand.

The 1.2 amp charge rate of the battery tender is too slow for anything but intermittent expected usage and storage. 

For a TM battery you expect to use very infrequently they will maintain the battery and not destroy it.

I started out with a 1 bank TM for my motorcycle which died after 6 months or so, and for my all electric boat I went to a 2 bank and one bank died after a bit over a year. 

The 2 and 4 bank BT models are pricey, enough so that a waterproof 3 bank 4A per bank charger from Noco was a no brainer.

The QD connectors on the BT are pretty handy if you plan on moving it about.

They are NOT waterproof.


----------



## BigTerp (Jul 26, 2019)

I use a Noco Gen 2. Set it and forget it. Just check the water level in my group 27's once a month or so. No issues at all. On my second set of batteries for my boat with this setup. First set lasted over 5 years (Everstarts).


----------



## onthewater102 (Jul 26, 2019)

I have an external smart charger but it's a basement dweller as it's not waterproof. Looking into the onboard tender/chargers is dizzying. The Noco Genious ones keep coming up in my searches with favorable reviews. I saw the ProMariner reviews on Cabelas' were...less than complimentary.

I still don't see an on-board unit that offers pulse charging, and most don't disclose the difference between their primary charging current and however many steps they move down through before reaching their tender charge rate. Makes me nervous because the charger works its way down 7 stages or so in the course of charging from 25amps to less than 1.


----------



## jethro (Jul 30, 2019)

DaleH said:


> What I've been doing lately ... is I'll put the battery on manual/low amp charge for an hour or two before I plan to go to bed and I'll throw the nice box I have for the charger on my pillow. So unless [insert actress of your choice] shows up and coaxes me onto the couch ... I'm pretty much guaranteed to make sure I shut that battery charger off!



Scarlett Johanssen? She can wait a few minutes, those deep cycles are expensive!!


----------

