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Battery Tender

8K views 67 replies 29 participants last post by  Zgeo 
#1 ·
My battery died while I've had my fj on jackstands for awhile due to some parasitic draw think my hatch wasn't shut completely. It's now to low for me to feel safe jumping. I'm looking for a good battery tender to hopefully bring it back for a few more months of use until I get a larger agm.
I'll be keeping it outside through the cold winter. Something small not the big ones on dollies. All the threads I could find related to this were older. Appreciate it.
 
#7 ·
The one we used for the the bikes was 750ma (.750amps) not sure that is enough to bring a dead battery back up to spec. It is enough to keep it up. I know they have other models.

I ended up buying a charger from Optima. Optima Battery Chargers

Besides the Optima batteries they also do other AGMs and standard lead acid batteries. ATV/Motorcycle batteries too.

I got the 1200 (don't like waiting around) The 400 would work fine. I'd definitely shop around for a good price and check other brands for a better price, be sure it does AGMs. AGMs require a little higher charging voltage.

I got mine when my FJ sat idle for a long time and the Optima charger would recover a dead AGM. (maybe an old wives tale)
 
#8 ·
if the battery is too low, a tender might not be able to start charging so it is not uncommon for an overly discharged battery to need to put the battery on a normal battery charger first, for, say 30 min, and then remove that and put it on the tender for storage

A good one, like the ones made by Battery Tender will tell you by the blinking lights if it needs this or not.

One thing that might be worth doing is first take the battery to the auto parts store and have them do a quick test to confirm none of the cells shorted out by the low charge, making it no longer serviceable. That can happen when an older battery has been allowed to discharge too far.

Since I don't drive my FJ all of the time, and want the AGM battery to last for as long as is possible, I hard wired in a Battery Tender lead (it has large ring eyes that fit under the battery terminal nuts), from the battery through the grille, and has a 2 pin joint on its end for quick connect/disconnect with the wall wart in the outlet. Then, I have an outlet in the front of the garage for the wart. If you forget to unplug the quick connect joint and pull out without disconnecting it, the design of the joint will allow it to come apart without damage (BTDT). Now, I put a cloth on the steering wheel as my reminder to disconnect first.


Norm
 
#9 ·
Or, just run it once per week for 15 minutes or so. I wouldn't call it a parasitic draw as all automobiles with an ECM have a normal draw for memory purposes and clocks such as in your radio. If you are getting a high (200mA) draw or more, I would look into actually fixing the draw instead of Band-Aiding it with a maintainer. Some newer vehicles with a lot of gizmos and multiple modules can see as high as 600mA draw, so more frequent running of the engine is necessary.
 
#10 ·
I have an Optima 1200, and have been very happy with it. I use it for my FJ that has an Optima red top, and several work vehicles that have lead acid batteries. Has worked well the dozen or so times I have used it to recharge batteries and maintain my red top.

Work paid for it, so the price didn’t bother me. But I imagine there are similar products out there that function just as well, for a lower price.
 
#11 ·
" just run it once per week for 15 minutes or so"

my concern with running the engine during the winter is acid/moisture buildup in the engine and exhaust that is created during the initial startup but which requires a fully through-heated system to burn off, the risk of causing internal harm (gradual, accumulative, not right away apparent when it happens) makes me put my car to sleep at the beginning of winter and not touch it until it is OK to drive in the spring

Some winters there will be a good rain storm well above freezing to rinse off the streets, and then a few days of dry weather when it can be taken out for a few good 20+ minute drives to get everything up to temp (including transmission, differentials, etc.) and fully dry out the exhaust, without the road salt dust that will attack the underside. Other winters it just sits in storage on the battery tender until spring.

On a modern car, the normal parasitic losses will tend to run down a healthy battery in about 2~4 weeks of sitting.
Trying to start a car on a partially charged battery puts a terrible strain on the battery, wearing one out much faster than if its in a daily driver.

So, a tender is a great way to deal with all of the above.
 
#13 · (Edited)
I've purchased many tenders over the years for various vehicles and Harley's. Wasted money on brands that did not work as advertised. At the beginning of Covid my Cruiser sat for several months and the battery discharged so low I had to replace it. Researching I discovered the brand CTEK. Pricier than others but it actually works as advertised. What sold me on the product was a Jay Leno Youtube video where he stated that he replaced all his tenders with CTEK products.

I'll never purchase another brand.

 
#17 ·
I bought one of these years ago due to the wife's car needing a full charge. I got it for sale at Auto Zone or Advance for like $49.99. I didn't have time to do any charger shopping or research beforehand and is still working great after many years. It charges and maintains(long term trickle charge storage) regular and AGM batteries.

For the FJ, I can fit the whole unit under the hood between the air filter box and firewall and completely close the hood.

I'm not sure if I would use it for long term trickle charging due to it having a fan. If the fan is always running the charger will probably build up with too much dust over time. It's been a while since I have used mine and I don't remember if the fan turns off after the battery is fully charged and the charger automatically switches itself to trickle charging.

 
#18 ·
I bought one of these years ago due to the wife's car needing a full charge. I got it for sale at Auto Zone or Advance for like $49.99. I didn't have time to do any charger shopping or research beforehand and is still working great after many years. It charges and maintains(long term trickle charge storage) regular and AGM batteries.

For the FJ, I can fit the whole unit under the hood between the air filter box and firewall and completely close the hood.

I'm not sure if I would use it for long term trickle charging due to it having a fan. If the fan is always running the charger will probably build up with too much dust over time. It's been a while since I have used mine and I don't remember if the fan turns off after the battery is fully charged and the charger automatically switches itself to trickle charging.

It also charges/maintains Deep-Cycle batteries too.
 
#21 ·
Agree with everything said, including by Jay and the CTEK guys.

Note that Battery Tender brand battery tenders are not trickle chargers, they monitor the battery and only supply charge as required, as the CTEK tenders do.

A trickle charger is a setting on a battery charger which is only safe to use for a short period of time, never while in storage.

Just thought I'd point that out in case the use of that term was confusing anyone into thinking that CTEK is the only source of a good tender (I admit theirs do sound awesome, and may even justify their higher price).

I've been using Battery Tender brand and its been serving my batteries well, for decades (and only cost $50), on occasional use cars that may only get a few 1000 miles a year, but their batteries still last 7 years, typically.

Norm
 
#23 ·
I've had 2 vikings for a couple of years that I purchased from (don't beat me up) harbor freight. I've used them on my tractor, boat, 4 wheelers, and mowers. I really have no complaints. They stay outside under a lean-to on something all the time. They have a cold mode, volt meter, and will do all kinds of batteries. They are sealed and they are digital so they will not charge completely dead batteries but they have been good to me.
 
#30 ·
I tried this Viking on my OEM Panasonic battery last year:


I left it charging for a few hours and when I came back to check it I could hear my battery boiling, and the multimeter said the battery was at 14.2 volts. I took it right back to HF - I’m not afraid of Harbor Freight products, but this is not one I would trust with my FJ’s battery. I have a Battery Tender Jr. that I use on my lawn tractor and some other small 12V batteries, but wanted something with a bit higher current and a desulfating mode, so I went with the BatteryMINDer. Got it from Battery Mart for $54:


It charges at 1.5A vs the Battery Tender at 750mA, has temperature compensation (so it won’t over or undercharge your battery in extreme temps) and has full time desulfation.

This recovered a bad battery from the wife’s car that showed 2V and 30% state of health on a battery tester. I’ve been using it on my FJ and it keeps the charge right at 13.2V when it’s charging, and no boiling batteries. My OEM battery went from 81% state of health to 91% within a few days of use. I hard wired it to the battery with a quick connect like Winterpeg did above, so now when I pull the FJ into the garage I just plug it in with the quick connect and forget about it. Can’t give it a higher recommendation.
 
#24 ·
I use this for my dual batteries.
1142432




With this extension to plug in without opening the hood.

1142433
 
#26 ·
Another +1 for CTEK. I have a Tri-Metric battery monitor on my camp trailer AGM batteries and can monitor exactly what the charge is that they are receiving. When I have the CTEK connected it charges the batteries to the exact perimeters that is recommended by the manufacturer wether it is flooded acid or AGM. It does as good a job as my more expensive solar charger. It does get pretty warm if you are trying to charge a battery rather than using it as a maintainer.
I also own a battery tender that is only used rarely. The CTEK is the go to.
 
#28 ·
I have at least five Battery Tender Jr units for my motorcycles, quads and implements, an 800ma Tender for my Camaro, a Battery Tender solar panel charger for my '69 VW Bug, and a Schumacher 1.5 amp on-board battery maintainer/charger on my 2008 FJ. The FJ has the OEM Panasonic battery in it at twelve years old, all in Alaska, always parked outside, and still going strong. I go out of town for work a lot, and anything over one week has the maintainer plugged in. The battery in my 2006 Softail is fourteen years old and still working fine. The good quality maintainer/chargers are worth their weight in gold! Schumacher, CTEK, and Battery Tender are all excellent products, and work very well with modern AGM batteries.
 
#32 ·
Hooked the charger up with the ring terminal connectors and had it on recondition mode. It stayed on it for 6 hours until I decided I needed to take the battery out and take a look at things. Coming out I noticed the insides of my terminals had some corrosion build up. I'm assuming the charger was reading this corrosion as the internal resistance of the battery which would be why it keep it on the desulfation mode. Used alligator clips and the charger skipped to step 4. Staying up for awhile to keep an eye on things. I like the ctek so far.
Technology Electronic device Electronics Wire
 
#35 ·
Decided what the heck, I'll get a Ctek. Got the MUS 4.3 test & charge. I ran a 14AWG (50ft) (min. required 18AWG) extension cord through the right front wheel well and set all wires up so, they have a dip in them just in case water manages to get on a cable it will just drip off the bottom and not make it to any power connections or the Ctek unit (eventhough it's basically waterproof IP65 rating). I couldn't really run the extension cord through the hood as it would be pinched too much so, that's why I went through the wheel well. I'll keep the Ctek in between the air filter box and the firewall area. Battery is a NorthStar AGM31A. Ctek claims that maintaining your battery with their charges can increase the batteries life by up to three times so, I figured that's great especially with how much a NorthStar battery costs. I guess there is really no way to tell how much more life the Ctek will give you but, at least I should be confident I got every last penny's worth of the battery.

I only drive my FJ like once a week sometimes only once every two. So, I don't forget to disconnect the charger, I'll keep all three windshield wipers extended out as a reminder.

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