Battery charger for storage of battery in garage over winter

SueBC

I will be storing my T@B in an RV storage place (not at my house). It does not have any way to keep the battery charged - so I will be removing and storing the battery in my garage for winter (after I've taken it there of course). The type of battery is -

Interstate SRM-24
12V
Wet
(link to actual battery)

What actual battery charger should I buy to keep it charged over the winter months? - any recommendations?

Michigan_Mike

Look at the battery tenders or a smart charger.   I use tenders at home and also installed a fixed 50W Renogy solar panel with a solar controller on my garage.  

pthomas745

I like my Noco.  This is a smart charger, and I use it for my trailer battery and car batteries. 

https://www.amazon.com/NOCO-G3500-UltraSafe-Battery-Charger/dp/B004LWVEKS

Keep in mind  your battery should not lose too much charge while sitting out of your trailer, but you are right to look for a way to keep it up.

Look up "battery self discharge" to see how temperature will affect a stored battery.

SueBC

Looks like the Noco G3500 is a good all round battery charger. I'd probably only need to check the battery 2-3 times over the winter at most, but the NOCO is a good way to keep the charge up while out of the trailer. Thanks pthomas

dhauf

I use these for all my deep cycle batteries in storage and never had an issue.  Doesn't damage batteries by constantly trickle charging them.

https://www.amazon.com/dp/B00068XCQU/ref=psdc_15707061_t1_B00DJ5KEEA

I've heard Noco is also a good choice.  I don't have one, but they seem like they have a few more features.

Carolyn

If you have two 6 volt golf cart batteries, will a battery tender keep them both charged? How would you hook it up?

dhauf

@Carolyn that’s a great question, I thinks it mainly for 12v application you certainly can hook it up to the two 6v batteries in series and have it charge that way but it may not be optimal due to it not balancing the cells properly.  It may be best to have two 6v battery maintainers when in storage and disconnect the 6v cells from each other first.  I know that Victron sells a battery balancer unit as well.

ColoradoJon

Check out this Pro-Logix charger.  Fully automatic with temperature compensation, 6v and 12v, 4 amp max charge rate, flooded, gel, and AGM modes:

Pro-Logix PL2140

I have the larger 20 amp version but only use the 2 amp mode.  This charger is one of the better ones that I have used!

Sparky13

Hi - I know very little (= nothing!) about battery chargers. I looked at the NOCO G3500 on Amazon. Which “amp” level should I choose? Thanks!

pthomas745

The "amp level" essentially tells you how fast the charger will charge the battery.  I chose the 3.5 amp, since it seems to be in the middle of the range, and my batteries are usually being topped off rather being brought back from the dead. 

This page explains the amp level of the charger a little better in simple language:

https://www.batterystuff.com/kb/articles/charging-articles/how-do-i-pick-a-battery-charger.html

Step 2: Determining Battery Size

We don’t mean physical size, but how many amp hours your battery stores. For example, a typical full-size auto battery is about 50 amp hours, so you would choose a 10 amp charger that would take about 6 hours to recharge it if the battery were completely dead. Another instance would be a marine deep cycle battery rated at 100 amp hours. It would take a 10 amp charger about 11 hours to recharge a dead battery to near 100% full charge. To calculate your total charge time, a good rule of thumb is to take the amp hour rating of the battery and divide by the charger rating (amps) and then add about 10% for the extra time to totally top off the battery.

Some folks wanting quick recharge should look for a charger with more amps. If you’re not in a hurry, you can select a smaller charger. The most important thing is to make sure you have enough charger power to do the job you require in the time you allocate.

ColoradoJon

Typically you want to charge at a low amperage.  Fast charging (10 amps or more) can increase the heat inside a battery and, in the case of flooded lead acid batteries, boil or steam off electrolyte.  I would choose something between 2 and 4 amps, or choose a charger that has selectable options.

The NOCO 3500 you mentioned is a 3.5 amp smart charger and they come highly recommended.  I am surprised that the description says it is for lead acid or lithium batteries only, up to 120 amp hours.  Seems a little limited for the price.  I'd take a serious look at the Pro-Logix charger that I linked above.  It's only $45 and you can charge any type of battery regardless of size.

pthomas745

I went back and looked at the Noco on Amazon.  The description of what batteries it can handle is a bit odd, but it will do AGM, etc.  For some reason the tech writer drifted off and separated sentences that should have been kept together:

• A 6-volt and 12-volt battery charger and maintainer for lead-acid and lithium-ion batteries up to 120 amp-hours
• An ultra-safe design featuring spark-proof technology, as well as reverse polarity and overcharge protection
• Safely charge automotive, marine, RV, powersport and lawn & garden batteries, as well as, AGM and deep-cycle batteries

ColoradoJon

@pthomas745 thanks for the correction!  I'd still save $15 and go for the Pro-Logix .  It can handle my 230aH 6V batteries without any doubt, and it has temperature compensation.

T@Balong

I have an inexpensive 15w solar charger for my Group 27 AGM battery.   Over the winter months, when using this charger, should the battery switch be on or off? or doesn't it matter?

Sharon_is_SAM

AGMs hold their charge incredibly well.  I think if you store it fully charged (after a full charge from a dedicated battery charger designed for AGMs) you may only need to check it monthly, then recharge as necessary.  If you want to keep a solar tender on it I would think the battery switch should be "on" so it can kick in as the voltage drops.  You did not say the conditions under which you store it - freezing, hot, etc.  That may help determine how often you check it.  We store ours in an area that does not drop below 55 degrees F, and we have gone for 4.5 months without charging and even then it only depleted 1-2%.

ColoradoJon

@T@Balong - that's about 1.25 amps in the best conditions, correct?  Personally I would disconnect the batteries.  The parasitic draw is not that much, but during the winter you won't get the maximum efficiency, and we won't be charging at night.

T@Balong

I'm in Michigan........the trailer will sit idle from mid-October to mid-January when we head to T@Bazona - yay!   I store it outside, covered with the PahaQue cover and under a shelter.   Perhaps I don't need to worry about the solar charger during that time, since it's an AGM.   I'll charge it up before turning off the battery for a few months.  Sound OK?

ColoradoJon

Should probably work just fine.  Check it every once in a while, like @Sharon_is_SAM mentioned, to make sure it is not discharging on you.

Sharon_is_SAM

Sounds like you don’t have a battery switch, so yeah, just pull the 30 amp battery fuse.  Just make sure you validate the voltage and that it is maximally charged after resting without a load.

pthomas745

A Battery FAQ that talks about "self discharge" and the effects of temperature on state of charge.

https://www.solar-electric.com/learning-center/batteries-and-charging/deep-cycle-battery-faq.html#Battery Size Codes

T@Balong

Thanks for the help...........I do have a battery cutoff switch........makes things a lot easier!

rajamar

I highly recommend this BatteryMinder charger:
https://www.amazon.com/gp/product/B00Q3CM2QY/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1 
I have used an older model of this for a Group 27 battery that is going on 9 years old now. I use the battery for CPAP and device charging while tent camping and more recently in the T@B. It is on the charger whenever we're at home. We usually camp for 3 or 4 nights and I've never had that battery go below 12.5 volts when I put it back on the charger. 

One thing to be aware of is that the T@B converter/charger never puts out enough voltage to truly put a full charge on the battery. It takes over 14 Volts and the T@B tops out at 13.6 - 13.7. Never getting a full charge measurably shortens battery life. So, even if you are keeping your T@B in the driveway or backyard on house "shore power" it is a good idea to keep a smart charger (which the BatteryMinder is) on your battery whenever possible.

BrianZ

I think you will do well, @SueBC, with the Noco G3500 charger, as it sounds like a good fit for your size battery.  

One other thing that you may want to be aware of is that it's worth checking to see what the battery manufacturer recommends.  They may specify the voltages and currents to be used for optimal charging, and this is typically a multi-stage profile that uses different voltages and currents at different stages during the charge cycle & vary with battery type.  Depending on the battery's state of charge, the charging voltage & current needed may be higher or lower, and if the battery is significantly discharged, both will be higher during the bulk charging stage.

See this page, for example from our Trojan battery manufacturer (there are different graphs for sealed batteries)..

Some here have recommended only a lower current, but look at the dark line in the graph - it depends on the battery's state of charge & if below 90% the charger should be using a higher current initially & lower in the final stages.  It even shows using up to 10-13% of the battery's Amp-Hour rating, so for our new 150 AH battery, that could be up to 15 amps.  I could be using a higher amp model, but I'm OK with Noco's G7200 model 7.2A charger we got recently, and it includes appropriate modes and the ability to detect the battery's charge & switch to the appropriate mode.

I would also disagree about the T@B's built-in converter/charger not being capable of charging at a higher voltage or achieving a full charge, especially for those who always use hookups, though it does seem to lack the flexibility of a smarter charger, including no equalization mode for correcting electrolyte issues.  We did have a circuit breaker trip once & lost some battery charge, so I have seen our WFCO charger switch up to 14.4 volts when it went into bulk mode that time.

Also, see my "Battery Trivia" topic with data showing how our T@B's WFCO has done a good job charging & maintaining our batteries, but we've never deeply discharged them either, always keeping the T@B hooked up.  We plan to do some boondocking, so this will change, and we now have the Noco charger and a higher capacity battery.

Sharon_is_SAM

@BrianZ, I think you may be the only member who has reported seeing the WFCO converter charge above 13.6 - 13.7.  How depleted was your battery at the time?

January 2017 from @ScottG -
"According to the literature that came with the onboard WFCO 8735P converter, it only kicks into "bulk" mode (14.4V) when the battery dips below 12.2V--and then only for "up to four hours."

For those of you that monitor such things, has anyone ever seen the converter put out 14.4V? If so, did you note how long it remained in bulk mode, and what the battery voltage settled to after that?"

Curious, how long did it stay in that mode?  There is another member with some information that the TaB wiring may limit optimal performance of the WFCO.  I will post it in a bit.

Sharon_is_SAM

@BrianZ  - Not sure if you saw this post from January 2017.  Talks voltage and amps and wiring of the WFCO.

wizard1880 said:

Sorry everyone, no insult intended.  Let me explain what I've experienced and read online about the WFCO converter, and some science behind lead acid charging technology.

Let's start with your average 3 (or more) stage charger.  It starts first by pushing in as many amps as its rated for into the battery.  This is known as the bulk charge.  The voltage will slowly rise from 12-something volts (depending on how discharged it is), all the way to 14.4 or so.  Then, it reaches stage 2, the absorption phase.  At this point, your battery is 80% charged.

In stage 2, the voltage holds steady at 14.4, and the amps begin to taper off.  This stage can take many hours, and it continues until the amps drop to less than 1, give or take.  At this point, it now reaches stage 3, and your battery is 95-98% charged.

In stage 3, the volts drop to 13.2 or so, and your battery very slowly charges to 100% over the next couple hours.  It then stays here, indefinitely, at 13.2v, until the charger is disconnected, or sometimes automatically, depending on the charger's programming.

Here's some trivia if you happen to own a battery tender (Deltran) branded charger: Phase 1 is a solid red light.  Phase 2 is flashing green, and phase 3 is solid green.  Other chargers that claim to have multiple phases (more than 3)  like the CTEK line, are actually just exaggerated parts of phase 1 and 2 usually.  For example, the CTEK 7002 has a light for <25% charge, and another for >50%, and while it cycles through those lights, it's actually just splitting stage 1 into two parts.  It's just marketing, really.

There's also an Equalization phase, but let's talk about that later.

Now, let's bring in the WFCO.  They claim to be a 3-way charger, but it's actually just a glorified power supply with variable voltage outputs.  It has no concept of constant current or constant voltage, like a true battery charger does.

The WFCO has a default voltage output of 13.7, at 35 amps.  When the voltage output at the converter itself, not the battery, drops below 13.2v for more than 2 minutes, it kicks up to what they call bulk charge mode, which is 14.4v.  Where the trouble with our wiring comes in, our T@B is wired with 10 gauge cable, at about a 6-10 foot run (depending on your model).  Over this long of a run, there's a high amount of resistance in the cable.

Here's a scenario.  Let's say your battery is very low, at say 11.8V, which is around 20-30% charge.  (Don't do this, if you can avoid it!).  Now you plug in your camper, and the converter comes on at 13.7v.  Since the battery is just an electron "sponge" (or what have you) at this point, it will absorb any juice it can.  The converter is pumping 35 amps, but due to the high resistance in the battery cable run, the battery terminals may show 12.6 or the like, and only 25 or so amps are flowing.  The rest of the energy is heating up the battery cable.  As a result, the converter end of the power cable is actually reading 13.4 volts.  No boost for you!

One way try working around this is by installing thicker cables between the battery and the converter.  When I installed my 2 golf cart battery system last summer, I used 2 gauge cable, and replaced the entire run.  That's almost twice as thick as jumper cables!  But guess what, I'm STILL unable to kick it into boost mode!   The deepest discharge I've done is about 60%, or 12.2v.  When I plug in the converter, the battery voltage jumps to 13 3, and no bulk mode.  :(

I haven't tried going deeper discharge than that, since I'm still easing these new batteries into service.  But why should I need to drain my battery to death, in order for this WFCO to properly charge my battery??  And this, right here, is the root of complaints that plague the WFCO.

The Progressive Dynamics converters, as well as IOTA and a couple other brands out there, will jump into boost charging (14.4) immediately when the converter is plugged in.  Battery full? It tapers back to 13.7 in a couple minutes so it doesn't overcharge.  After a couple hours, as long as the current is low enough (I.e. you're not using your trailer), it drops to 13.2 and stays there.

Speaking of 13.2v, the WFCO is also designed to drop to 13.2 after approximately 28 hours of idle time (little to no current in use).  The trouble folks run into, is that they can't get it to drop into this rest mode, even after several days.  Sometimes the current draw from your smoke alarm, co2 alarm, and entertainment system is cooling the converter into thinking you're using it.

Personally, I wasn't able to get my WFCO to drop to 13.2 until I disconnected everything from it first (pulled all fuses out except battery fuses), and gave it 3 days time.  Once it finally dropped down, I plugged all fuses back in, and it seemed to stay at 13.2.  This worked for about 2 months.

But now, my converter seems stuck at 13.2, and it won't climb back up to 13.7, even when I plug it out and back in!  Worse, it suddenly jumped into boost mode on me, without warning, just last month before our camping trip!  I left it that way overnight (figured the batteries could use a top-off before the trip), but it's stuck at 13.2 again.

I've found many others have had a similar experience to mine, and have either had it repaired under warranty or just swapped it out with something else.  And others have just added their own battery charger, as many of you have.

Oops, before I forget, let's talk briefly about equalization mode.  Very few battery chargers support it, and the CTEK is probably the most affordable brand that comes with it.  When you choose equalization, the charger first fully charges your battery.  Then, it hops the volts up to 16v, for up to 4 hours.  This literally boils your battery, mixing up the acid, in order to prevent acid stratification ( this is when acid on the top is weaker than acid on bottom of the plates).  Also, it helps remove any light sulfation that may have built up on the battery's plates.  How often you equalize is debatable, and every battery manufacturer has a different opinion on it.  Doing it too often will erode the positive grid plates in your battery, and can shorten its life.  Consult yourself battery manufacturer's web page or owners manual for recommendations.  AND--if you have an AGM battery, avoid equalization!  Only Concord Lifeline AGM batteries state that it's OK to do so, but only in very certain conditions.

I hope this helps some folks out.  I'm not against WFCO converters, heck I still have mine.  I hope this sheds some light on your experiences and expectations of them.

BrianZ

Thanks, @Sharon_is_SAM, yes, I'm pretty sure I've read those threads.  I'm sure I saw 14.4 volts on the display after resetting the breaker, but not knowing how long it had been tripped off, I was likely just happy to see it was doing its job going into bulk mode & didn't check again until the next day when it would have been back to 13.6V.  So, I really don't know what the battery's state of charge was at the time or how long it stayed in bulk mode.  Sorry, but I probably wasn't aware of the WFCO charger issues at the time.  Could resetting the GFCI breaker have possibly played a role in prematurely triggering bulk mode?  I don't know.

Wizard does point out some of the shortcomings of the WFCO, particularly for those who do any significant deep cycling of their batteries & could benefit from a bulk charge cycle, but I also have to wonder if he could have had a defective unit as well.  I've also seen ours drop down to the 13.2 trickle charge, but only when nothing except smoke detectors have been powered on for about 3 days.  That never happens anymore, since we've been keeping the ceiling fan on, exhausting on very low speed with the new continuous speed control.  I'd be tempted to take a closer look if we ever get down near 50% again, but now that I've got a solar panel on order that may not happen.

PS:  After re-reading the WFCO manual, I realize I still need to annotate what I believe is a typo under their description of Bulk Mode:
"When the converter senses that the RV system voltage is less than 13.2 Vdc (equivalent to less than 50% of battery charge), the converter will automatically go into the 'Bulk mode'."
I believe they mean 12.2 Volts.  It does say that bulk mode is for a maximum of four hours.

ScottG

@BrianZ, you are correct about the typo. I've confirmed it directly with WFCO and mentioned it here in a couple threads. At the time it was on both their printed and online literature, and I'm not sure if any effort was made to correct it.

Sharon_is_SAM

@BrianZ, re the GFCI, I think that only serves to halt current flow and the circuit comes out of the converter, so I am guessing it would not impact the charger function.  That is a question for @Michigan_Mike!

ScottG

I assume you are talking about the red button on the 120V GFCI protected receptacle under the driver's side bench. There's no conceivable reason why that should affect the battery charger output. The battery charger is powered through the converter (12V DC) side, while the cabin receptacles are powered directly from the 120V AC distribution panel.

BrianZ

No, sorry, was referring to a gfci outdoor outlet on the side of our house that we plug the T@B into.  I think our washing machine in the house uses the same circuit, or it may be the oversized plug in the outlet interfering with the gfci pushbuttons that flipped it off.