Should I Use a Battery Tender?

  • Thread starter KodyWallice
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May 7, 2021
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I went out to start up my pickup truck a few days ago and it didn't start. For the first time in over eight years of owning this truck, the battery was dead. Not completely dead, but dead enough that the truck wouldn't start in cold weather. The problem is that I only use this truck about every six months and even then, I hardly use it at all. Just for very short distances. It's got two batteries in it and I would hate to think that I need to replace them.

This event got me thinking. I wonder if I need to hook up a battery tender to one of the batteries, just to keep them charged. I have a small tender that I bought for a motorcycle I owned years and years ago. Would this work? Should I hook it up? Is a battery tender the right thing to use here? Why use a battery tender at all? What's their purpose? To keep the battery charged when it's not in use for a long time? I know, so many questions.

COMMENT: Your situation is exactly what battery tenders (trickle chargers) were made for. They're for those vehicles or motorcycles that aren't used very much. Instead of going outside to find your battery dead, the tender will keep it charged. I have heard that it's also good for the battery to keep it changed like this.

Some people confuse regular battery charger trickle charge settings to be the same thing as a battery tender. This isn't the case. I believe, and this may have changed through the years, that trickle chargers can over charge a battery. Battery tenders have what the refer to as "brains." A battery tender, once hooked up, will trickle a charge back into the battery only when it's necessary. When the battery is full, it'll stop charging. They say there's a microprocessor inside the tender that tells it when it should turn on and off.

There are many sites online that describe how and when to use these tenders. The tenders have red and green lights and these lights mean different things when blinking and when they're solid. Really though, if your battery is already more than 30% charged, all you need to do is connect the tender, plug it in, and that's it. Just keep it plugged in until you want to use your truck again. Here's a good model to buy: I don't know if that's like the one you already have, but it's decent for what you need.

Here are a few photos of the one I bought a while back.

This is the tender itself. This is what plugs into the wall or extension cord.


This charger comes with two connection types. These are the regular clips. They don't have teeth or I'd call them alligator clips. Almost the same thing.


This is the entire setup. The charger (tender) and the clips.


And finally, we have the eyelet connections, otherwise known as ring terminals. You can use these instead of the clips. The wires simply plug in to each other. These are particularly good for motorcycles that sit for a long time. Just disconnect the batter from the bike and bolt these connectors on. I suppose you can do the same thing with trucks and cars. Or boats - whatever.

battery-tender-eyelet-connections.jpg eyelets-connection-cord.jpg

COMMENT: I have the same battery tender. I just hooked it up to my truck. I took some pictures that I'm including in this post. You can see the red light on. That means it's charging. I'll go back out later to see if it turns green.

I was reading that some trucks have what they call a "parasitic" draw on the batteries, which causes premature battery failure. Because of this type of thing, a few different companies make on-board battery tenders that you install right in the engine compartment. When you're not using the truck, you just plug the tender into an outlet. So the difference between these products is that for the one that I have, I need to pop the hood and connect the charger every time I want to use it and for the other one, it's already connected. I only need to plug it in. These are the two models that I just read about in a Ford Truck forum:

Schumacher SC1300 1.5A 6/12V Fully Automatic Battery Maintainer -

NOCO Genius GENM1 4 Amp 1-Bank On-Board Battery Charger -

I think this is a great idea and I might invest in one of these. There are many more brands and models, so I'll check them out too. I like the idea of only having to plug the truck in as opposed to going through the whole opening the hood and then connecting the one I have up. I'll use that for my lawnmower or something. By the way, if you want to read that post I just referred to, here it is.

battery-tender-charging.jpg connected-to-truck-battery.jpg

COMMENT: Actually, you know what I was just thinking? Can't I simply bolt the ring terminals from the charger that I already own to the battery and then zip tie the tender somewhere in my engine compartment? And then I could zip tie the cord (plug) somewhere near the front grill so I could plug it in easily. Isn't this the same thing as an "on-board" tender? It sure seems that way to me. I'll check it out.

COMMENT: I wouldn't do that. The on-board tenders are made for that. The one you're using isn't. Yours might not be able to handle the shaking, heat, or getting wet. Yours is made to sit in a dry garage doing what it's meant to do. Pick the right tool for the job.

COMMENT: Well, it's been almost a day of having the battery tender connected to my Ford F250 and the light is still red. That means it's not charged yet. I am wondering two things: does this little tender have enough power to actually charge the batteries, and do I need to actually put a charger on the batteries to fill them up first, before connecting the tender? From what I've been reading on the forums, I really don't think I'm going to be charging the batteries with this thing. I believe I need to top them off first. I'll let you know what I end up doing. I happen to have a real battery charger on hand, so I may put that on trickle charge for a while.

COMMENT: If your battery tender isn't sized properly for your truck, it may never charge the batteries. I assume you've got two pretty large batteries in that thing, so you might want to look at how many amps your tender is capable of putting out. I see from the photo above that the output is 750mA, which is about half of what you want. You probably need at least 1.5A.

COMMENT: I've actually been reading that a 1.5A won't be large enough either. I'm probably going to go with a 3A. Right now, I'm researching the:

Schumacher SP129 -

and the:


Both look very good. The Schumacher is a 3A and the NOCO is a 2A. I'll have to read up and watch some videos on both before I buy. But yeah, my little 750mA ain't going to cut it.

COMMENT: I just went out to my truck to check on the battery tender again and the red light was still on. This has led me to wonder if it was keeping up with the demands of the batter. Because of this, I disconnected the tender and replaced it with my Black & Decker battery charger. I bought this a few years ago. Here's the official title:

BLACK+DECKER BC15BD Fully Automatic 15 Amp 12V Bench Battery Charger/Maintainer with 40A Engine Start, Alternator Check, Cable Clamps

Strange thing happened. When I pushed the Charge button, the interface told me that about 2-3 amps were flowing to the battery. But after only a few minutes, the charger switched over to FLO mode. I think that stands for float mode, indicating that the battery is completely charged. That's what the interface said as well. Take a look. I snapped a photo of it.


I guess that's good, but after reading some reviews on this charger, I'm not so sure. The reviews claimed that this charger gets stuck on FLO mode and never actually charges the battery. I'll have to check that out, but as of right now, it looks good. I've also used this charger over the summer to charge up my ride-on lawnmower battery and then this winter to charge up my truck batteries. Every time it has performed well. I should probably go out and start the truck up just to see.

COMMENT: I just read this on Amazon: According to the instruction manual, when the battery is completely charged, the unit automatically goes into float charge (FLO). This means your battery is fully charged and the charger will only charge to keep the voltage up.

COMMENT: I wanted to quickly update this thread. I have big news. The light on my battery tender has finally turned green. I just went out this morning to check on it and yes, it was green. I checked yesterday and it was still red. I did start the truck yesterday and I must say that the battery was very strong. Maybe the strongest I've ever felt it. The truck (diesel) started immediately and now today, that light on the tender is green. I guess it just took a while to charge, but it did. And all this with a 750mA charger. Not bad. I still want to get that other one though. The NOCO Genius 2.

COMMENT: I'm starting to read information about batteries all over the place. I just read this on Facebook:

Keep the battery stored out of the freezing cold environment and keep the battery charged.
There is a direct relationship between a battery’s state-of-charge and the temperature at which it will freeze. A fully charged battery can be stored at subfreezing temperatures (down to -75° F) with no damage. By contrast, a discharged (dead) battery will freeze at only 27° F. A battery not connected to anything can lose up to one percent of its charge each day at 70° F and more as the ambient temperature drops.

I had no idea that batteries can even freeze. I've got two auto batteries out there in the cold, a lawnmower one, and an ATV one. I'm starting to think that I'll need maintenance chargers on all of them. The lawnmower battery was dead this spring when I tried to start the mower. I just chalked that up to getting old, but now I know better. And I certainly don't want the ATV battery to die before its due. I need to get on the stick. I'm thinking about removing the two batteries to keep them inside over the winter. I'll connect tenders to them in indoors.

COMMENT: Two interesting things as of late. First, I ordered the NOCO Genius2 last night from Amazon. I picked it up for around $50, so I'll update this thread when I get it. I'm going to connect it to my ATV battery. I'm still deciding on whether I want to completely remove the battery from the quad and charge it in my garage or if I want to keep it installed and run an extension cord out to the charger. I really don't want to do either. I'd like to be able to just plug it into a wall, but it's too far away.

Second, I just connected my BLACK+DECKER BC15BD battery charger to my Cub Cadet ride on lawnmower battery and the charger went straight to FLO mode. That's a problem. I turned the key and the mower lights came up. The battery was pretty dead though, so it may need some charging before it gets up high enough for this charger to do its job. I'll figure that out. I may have to force charge it somehow and then let it trickle.

Here are some photos of that. The battery model number is 725-1750a. People say that if this charger goes straight to FLO, then the battery is completely dead. Well, it's not, so it should really charge the battery before going to FLO.

725-1750a-battery.jpg 725-1750a-cub-cadet-lawnmower-battery.jpg under-cub-cadet-riding-mower-seat.jpg

COMMENT: Update: Something very strange is going on. I decided to swap the Black & Decker battery charger for the Battery Tender I had connected to my truck. I connected the battery tender to the lawnmower battery and after about three seconds of displaying a red light, the light turned green, indicating a full charge and maintenance mode. I know for a fact that the battery doesn't have a full charge. I won't even turn the lawnmower over. So what's going on?

I just read something on another forum that made sense.

My experience is that the green light will remain steady when the battery cannot be charged any further. It does not indicate that the battery is at 100% of "new" rated capacity. It means that what ever the capacity of the battery is at is charged to that point. A battery loses capacity over time with normal use. If the battery is fully discharged and dead ( like left the lights on overnight) it will only accept a charge of about 60% of it's previous capacity. Do that twice and you have a battery that is only capable of 35% rated capacity. And that battery if placed on a tender will show a "green light," just like a brand new battery with a CCA of 380.

That actually makes sense. I have not taken very good care of this battery at all. It's gone completely dead a few times. I think I'm going to go back and and connect the real battery charger back up and run the recondition mode, just to see what happens.

COMMENT: Yes, your battery certainly seems like it needs to be reconditioned. Most people throw their batteries out (or recycle them) at this point and buy new ones, but it's much more economical to recondition them. Allowing your battery to go dead just a few times is very bad news. Every time a battery discharges, lead sulfate crystals forum around the interior plates. As these crystals build up, they affect how much the battery is able to charge and discharge. By keeping a battery maintenance device, such as a tender, connected to a battery while not in use keeps the crystals at bay. In your case, it appears that your battery has gone dead one too many times and now the capacity is so low that every charger you attach to it thinks it's at full charge. The thing is, it may be. Your battery may actually be at full charge, even when it's nearly dead. That's why your Black & Decker charger and your Battery Tender are reading that the battery is full. Recondition it if you can. I'd like to see how this turns out.

Also, if you're curious, the types of batteries that are able to be reconditioned are AGM, Gel batteries, Lead Acid car batteries, Lithium-ion batteries, NiCad, and NiMH rechargeable batteries. The one you have in your mower is probably a lead acid. I looked up some replacements and that's what they were.

COMMENT: Thanks for your reply. If this works, I may just recondition all of my batteries and then keep tenders on them all. I'm sure the capacity of them has been diminished, as I've let them all go dead a few times. I'll keep this thread updated.

COMMENT: I received my NOCO GENIUS2 battery maintenance charger today. Boy, what a package. They did this up nice. I took some photos of the unboxing if you're interested. Also, I wanted to mention, I thought they'd include an extra wire with eyelet connections along with the clips, but they didn't. I see that I can unscrew them from the clamps, but that's kind of a pain. Whatever. This device looks very nice. Tomorrow, I'll take a look at my ATV to see exactly what type of battery it's got in it and I'll either run an extension cord to it and charge it in my trailer or I'll remove the battery to keep it charged inside my house. I'll take photos of that too.

battery-maintenance-charger-parts.jpg noco-genius2-battery-charger.jpg noco-genius2-box.jpg noco-genius2-contents.jpg noco-genius2-unboxing.jpg

COMMENT: I removed the battery from my 2018 Polaris Sportsman 850 this afternoon (different post) and I just finished connecting my new NOCO GENIUS2 to it inside my house. Surprisingly, after just a few seconds, the green charger light went on, indicating that it was fully charged. This is good, but slightly disappointing. I sort of wanted to see it charge. Oh well. I'll keep the charger on the batter until springtime when I bring the quad back out for some work. At least I don't have to worry about it freezing and discharging outside in my trailer.

Here are a few photos of the battery maintainer connected to the battery.

First, I connected the charger to the battery and pressed the mode button on the charger. I chose AGM mode because that's what type of battery came with the ATV.


The lights on the NOCO GENIUS 2 began cycling and the AGM mode light was illuminated.


After a few seconds, the green "fully charged" light came on. As I sit here and type, that green light is slowing phasing on and off. I guess that indicates a full charge as well. It was steady green a little while ago.


Here's the entire setup. It's pretty nice.


COMMENT: By the way, here's a post about how I removed this battery from my quad and a few videos about how to operate the NOCO charger. They cover how to set the mode and how to force charge the battery.

COMMENT: I connected my voltmeter to this NOCO charger yesterday to see if it was pulling any current in standby mode. Having three of these maintenance chargers connected to three different batteries has given me concern in regards to my house electricity usage. I don't want any surprises when I get my electric bill. If this 2 amp charger were to charge at the full 2 amps for a month, that would be like having a 240 watt light bulb on the entire time. That'll add to the bill, for sure. Basically, at 120 volts x 2 amps, I'd get 240 watts.

The charger displayed the steady green light, indicating that the battery was full and the charger was in maintenance mode. I connected the multimeter to check the amperage. At first, the charger displayed a red light and then an orange one. The initial current showed .5 amps for the red light and then it dropped down to .2 amps with the orange light. The closer the charger came to seeing the battery at a full charge, the less current it drew. After a few seconds, the green light became illuminated again and the amperage dropped to 0. So basically, when the battery is full and this charger is in maintenance mode, it doesn't use any electricity. Although, I'm sure it uses some from the wall outlet to keep it on. Maybe I'll test that next.


May 10, 2021
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  • #2

Charging My Motorcycle Battery - Why is it Bubbling/Fizzing?​

The battery in my 2005 Suzuki Boulevard S50 has been fine all summer. I've been riding the bike and it's been starting without hesitation. The battery has been holding a charge with no problems at all. That all changed when I inadvertently left the lights on one night. This completely drained the battery and left it with nothing at all. I've been trying to charge it up to no avail. It's like it won't take a charge at all. A friend owns a Black & Decker battery charger and told me he can recondition the battery, so we gave that a shot. I really had nothing to lose, since the battery was dead anyway. We reconditioned the battery for a few days, but now when we put the trickle charger back on, I can hear a slight fizzing or bubbling noise coming from the bottom. Is this bad? The battery doesn't feel hot at all - or even warm for that matter. It's not like it's boiling or being overcharged either. What's going on? Should I be worried?

COMMENT: What are the amp hours on the battery? I looked up a replacement battery for your bike and see the average is 16 amp hours. The rule is that you divide that number by 10 to find your charging rate, as to not overcharge it. This would mean that you shouldn't be charging the battery with anything more than 1.6 amps. Since you say you've got it on a trickle charger, I don't think this is your problem, especially since the battery isn't warm or hot.

COMMENT: Here's a picture of the battery:


It's a Motocross Platinum Original Equipment battery (YB16B-A1) with a part number of M22161. There's no information on the amp hours on the battery. I have seen other motorcycle batteries with their amp hours displayed right on the front, so I'm curious as to why this one isn't showing anything. When I search the part number, I find a comparable battery that people use for the Suziki S50 motorcycles. It sells for around $82 on Amazon. It's called a Yuasa YUAM22161 YB16B-A1 Battery. I'm assuming this is the same exact battery, but under a different brand name.

I'm using a NOCO Genius2 as the charger and it charges at only 1 amp, so I don't think the charger is the problem.

COMMENT: You need to be very careful when describing what is happening inside the battery. Large bubbles and a lot of heat is called boiling. This occurs when the amperage entering the battery from the charger is too much for the battery to absorb. When the amperage is too high, bubbles form to create a flammable hydrogen gas, which is extremely explosive when mixed with air. A dangerous situation indeed.

The more likely situation in your case is just bubbles forming in between the plates inside the battery as the electrons enter it. The bubbles start off small, but then grow in size to make noise and rise to the top of the interior liquid.

If you've got a battery tender (smart charger in float mode) connected to the battery and the battery is making sounds like a glass of soda (pop - fizzy drink - carbonated beverage), then don't worry about it. Most people will say this is normal. If you've got larger bubbles though and it sounds like you're boiling a pop of pasta with a rolling boil on your stove top, yeah, you better disconnect that battery pronto. You're definitely overcharging it. Either way, keep an eye on things to make sure they don't get out of hand.


May 11, 2021
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  • #3

Suzuki Boulevard S50 Battery Installation Problems​

I am having a helluva time dealing with the battery installation in my 2005 Suzuki Boulevard S50. Finding it and removing the old one from the bike was a chore and a half and now that I have to install a new one - well, let's just say I'm ready to go nuts. Why in the world did Suzuki decide to hide the battery all the way at the bottom of this bike? It's such a pain to deal with. Basically, I left the lights on one night and the battery was drained until it went completely dead. I couldn't charge it at all. For some reason it wouldn't hold a charge in the least. I tried everything, even reconditioning it. Nothing worked, so I just bought a new lead acid battery. For anyone who needs help finding their battery in this bike, this video should help:

2005 Suzuki Boulevard S50 Battery Change

Te problem is, the new battery I bought uses some strange hardware. There are two posts for the positive and negative terminals that have got holes in them. The holes aren't top to bottom, but side to side. There are nuts and bolts to use as well, but the problem is, once I place the nuts in place next to the posts and slide the battery up into position and try to push the bolts through, the nut gets knocked over and I have to start over again. I'm at my wits end.

My question is: does anyone have any ideas for how I can keep the battery terminal nuts held in place so I can screw the bolt into it?

COMMENT: People have been plagued by the problem you're describing forever. Some bikes hide their batteries, but snowmobiles are the worst. With some snowmobiles, you really have to snake the battery down and behind so many things. When it comes time to attach the wires to the terminals, the task can become very difficult. Those nuts rarely stay in position and they fall off never to be seen again.

Professionals use a little trick that can help immensely. Basically, what you need to do is put the nut in position on the terminal post and then wedge a piece of rubber hose, sponge, foam - whatever - behind the nut so it's being pressed up against the terminal. This way, that nut will stay in place as the battery is moved into its home. And since whatever it is you choose to wedge behind the nut is soft, when you screw the bolt into the nut and it hits that soft backing, it really doesn't matter. You can bolt right into it and the soft object will give way.

Here are a few videos to show you what I'm trying to describe:

Battery Nut Hack

Never Lose Your Battery Bolts Again! Yuasa Bikemaster Batteries Plus Interstate

COMMENT: OMG! Thank you so much for your help. I think this will work out. I'm going to try it in a little while.

Two quick questions:

1. When connecting the red and black wires from my motorcycle to the battery, which terminal do I connect to first?

2. Let's say I lose a terminal nut or bolt. What's the size of those in case I need to replace them?


COMMENT: No problem. Glad I can help.

To answer your questions:

1. When removing a battery, first disconnect the black negative wire and then connect the red positive wire. When replacing a battery, reverse that order. Attach the red positive wire first and then the black negative wire.

2. There is a universal size for motorcycle battery nuts and bolts. It is Course M6 (6mm x 1.0mm). Generally, the thread length is 12mm, but your battery may come with a few different bolt sizes (lengths), from shorter to longer, that may assist in your specific situation.