How to boost charge AGM batteries in storage?

[bobbolotune]

The manual for my Lifeline 100 Amp Hour Deep Cycle AGM 12 volt batteries says this:

"While in storage, batteries should be boost charged every 90 days or when open circuit voltage drops to 12.5 volts for a 12 volt battery. Boost charge batteries using a constant voltage charger set to 14.4 to 15.0 volts for a 12 volt battery. The boost charge should be applied until the charging current falls below 0.5 percent of the battery's 20 hour rated capacity (0.5 amps for a 100 Ah battery)."

I don't understand this at all. What is a boost charge? What is a constant voltage charger? How do I measure when the charging current falls below 0.5 percent?

So I tried calling the battery technical support, but it didn't help. He said several things. He said a cheap battery charger from Walmart might not be able to get up to the required 14.4 to 15.0 volts. He recommended a specific charger and said there is a boost charge button. He said just press that button and it will do what is needed.

But then I looked up the recommended charger and there is no boost charge button. Rather, it is one of these fully automatic battery chargers with no buttons at all. Also when I got to the 5th review on Amazon saying that this charger overcharged and boiled their AGM batteries I decided to believe it and stay away from this specific charger.

So where do I get a charger with "constant voltage boost charge" capability? Well, he also said that boost charge is just the first stage of a 3 stage charger. So does that mean I can just get any 3 stage charger and it will boost charge the batteries, then harmlessly let it go into the other 2 stages? That actually there isn't any special charger needed?

Also, that the manual says the boost charge should be applied until the charging current falls below 0.5 percent. He said that only high end chargers will say the charging current. Including the specific charger he recommended doesn't have this feature, so he said don't worry about that. I suppose because a smart charger knows when to cut off.

I am still completely lost about what I need to do. Do I need a special charger or will any charger that supports AGM batteries do what is needed? Most battery chargers are completely automatic, so will it automatically do what I need? Maybe the battery manual quote above is only confusing words (saying to use a constant voltage charger set to specific volts) where actually any battery charger will do what is needed?

If someone could even recommend a specific charger, maybe something available on Amazon, that would be greatly appreciated. There are so many battery chargers around it is hard to pick a specific one. My needs are minimal, only to boost charge the batteries while in storage once every 90 days at most, so a low end charger should be enough... if it has the features that are required (and does not have a reputation for boiling AGM batteries).

I am completely lost and hoping someone can help. Thanks!

[MEXICOWANDERER]

Stored

Cycled

[JimK-NY]

red31 wrote:

JimK-NY wrote:

MEXICOWANDERER wrote:
Maintenance not in use.

I think I need a Mex to English translator.

maintenance - not in use, not being discharged, stand by.

in use - being discharged or used!

This makes even less sense. I feel like I landed on an alien planet.

[red31]

JimK-NY wrote:

MEXICOWANDERER wrote:
Maintenance not in use.

I think I need a Mex to English translator.

maintenance - not in use, not being discharged, stand by.

in use - being discharged or used!

[JimK-NY]

MEXICOWANDERER wrote:
Maintenance not in use.

I think I need a Mex to English translator.

[MEXICOWANDERER]

Maintenance not in use.

[JimK-NY]

MEXICOWANDERER wrote:
.........

Weekly application of temp compensated 14.4 volts constant for 2 hours each would approach ideal numbers. Temp compensation would be important.......

I use temp compensation. Even so 14.3 or 14.4 nominal volts and 2 hours typically leaves me a long way short of 0.5%. In fact if I start with batteries at about 75%, after bulk, I can hold the absorption for 2 hours and am still pulling about 3% amps. I called Lifeline and discussed this without any resolution or new information. I typically need to maintain 14.3 volts for at least 4 hours to get below 1%. That is with relatively new batteries. Since I am using solar, an interruption with a passing cloud or some shade will greatly prolong the absorption charging time. Sometimes it seems that even a brief interruption results in the need for another hour of absorption charging.

The whole process just seems weird and exceedingly slow.

[MEXICOWANDERER]

Using kWh measurement, recharging at less than 20% A/H capacity from 50% level of charge progressively deteriorates the final AH storage capacity of the Lifeline. Like any other electrochemical reaction, the effect is time reactionary. The longer the accumulator stays discharged and the slower the recharge x cumulative number the greater the storage degradation. In effect - my stored 31 would be affected more by slow recharge than a similar unit discharged for a day or week.

Weekly application of temp compensated 14.4 volts constant for 2 hours each would approach ideal numbers. Temp compensation would be important.

But for my unit I have decided that 8 hours at 14.4 voltage saturated (constant voltage) would be ideal. The battery may start out at 80 amperes acceptance. Such high amperage in excess of 20.0 (It's a 100 amp hour 31) is not necessary.

Any arguments against this protocol would have to contain explanation of its service life and ultimate low loss of capacity, please.

[BFL13]

http://lifelinebatteries.com/wp-content/uploads/2015/12/6-0101-Rev-E-Lifeline-Technical-Manual.pdf

Page 20 has the 20% mention but is for deeper than 50% DOD cycling. They do say if you don't have that many amps of a charger, you could use their constant current final stage trick (hard to do with normal charging equipment)

That is in contrast with Trojan's 20% for all Bulk stage AGM charging (which would have to be under 75% SOC to get any Bulk Stage with a 20% initial charging rate)

The Lifeline manual does give some times for the Absorption stage, which are not very long, but not clear on the whole profile those times go with seems to me.

That Lifeline blurb also mentions progressive capacity loss from a series of incomplete recharging like 50-90s when you would get sulphation and then have to do a reconditioning. That desulphation would not harm the battery anywhere near as much as leaving it sulphated IMO.

In all cases you still need an ammeter to see when you are down to 0.5a/100AH. Your charger or converter can't tell you that. It especially can't tell you that the amps being accepted have started to rise again after tapering! Oops. Stop the recharge! the battery is heating up.

[MEXICOWANDERER]

This is a key factor in determining whether a 20% of amp hour recharge becomes mandatory...

AGM batteries tend to demand 20% amperage the further they are discharged.

For maintenance purposes if power is available try to keep them from 90% to 100%.

At 50% fill, the 20% rule applies strongly.

I've noticed with my (6) Lifelines that the greater the amperage seen at a 14.4 volt limit the faster they will pass through the final 5% of charging. Meaning a 50 ampere initial charge rate improves the speed of the final 5% by more than 10% Less time. I haven't measured it because it is a moot point. Recharging a 50% discharged Lifeline slows down the final 5% to an agonizingly slow pace.

The 20% recharge factor may be one of the top negative issues with absorbed glass mat technology. The final 5% capacity requirement doesn't help it's reputation either. Raising voltage from 14.4 to say 15.0 does not aid much to recover time loss either. It gives me thought of using a wet battery and a DC to DC booster to finish laggard AGMs.

[JimK-NY]

I talked with Lifeline technical reps in the past. They are used to dealing with returns and issues for older and often neglected batteries. A heavy reconditioning cycle can often restore them for years of use. It seems that the low cost Noco can accomplish a reconditioning cycle.

I am certainly not an expert but if they were my batteries, I would start by a simple 14.3 complete charge. Then I would do a load test (with 100 watt incandescent bulbs). If the load test looked good, I would not do the reconditioning. Perhaps I am just overly cautious but the reconditioning seems to be harsh and a step for otherwise terminal batteries.

In any case the OP has a couple of other choices and for the future they could merely get a low cost trickle charger to maintain charge.

[BFL13]

If it is true that Lifeline is recommending a charger that can't do Lifeline's spec charging profile, then they should be asked about that.

The OP obviously does not understand charging profiles and battery specs, so he should get up to speed on that.

[JimK-NY]

At this point, ideally you want to apply a temperature compensated charging voltage of 14.3 volts until the amperage drops to 0.5% of battery AH rating. It seems you have 3 ways to accomplish this. You can buy the Noco or similar charger and use the "repair" mode. The manual does not detail what happens but presumably the charging voltage is bumped up. I think it actually goes to 16 volts which might be more than needed and unnecessary. Your second choice would be to pull the RV out of covered storage, install the batteries and use the solar system. Ideally you have a 3 stage charger that can hit and maintain 14.3 volts. Your third choice would be to again install the batteries and use the built in 110 volt charger by either plugging in or running a generator for the many hours needed.

[bobbolotune]

I am the OP. I think that I finally have this figured out.

Things went bad when I called Lifeline and he recommended using a Noco Genius charger, same as someone who posted, but Lifeline told me to get the Gen1 model. That is a waterproof model for permanent install in a boat, and it has no buttons or options. Also that is the one I said in my original post I gave up after reading amazon reviews saying it boiled their AGM battery.

A couple responses to this topic talked about the Noco Genius 10. One of those response said that is what Lifeline told them. That is a different model than what was recommended to me. That one has buttons and options. There is still some negative reviews for the Noco Genius 10 on amazon but I am concluding that there is a lot of things that can go wrong with charging batteries so any battery changer will have some negative reviews. That Lifeline recommended it to someone and a couple responses say they use it, it seems my best bet for the way to go.

So I am about to place an order for the Noco Genius 10.

I found the Noco Genius 10 manual online. It indirectly says that it does boost charge when talking about the lights showing charging status. It says: "Pulsing Green LED - Bulk charge complete, optimizing battery for extended life."... actually it says "bulk" charge but I assume that is what the Lifeline manual is referring to.

One of my original questions remains unanswered, which is that the Lifeline manual only talks about boost charging for maintenance when in storage. My questions was if it is ok to also go into the next stages of charging, as it vaguely says in the Noco manual quote above "optimizing battery for extended life".

Lifeline said there is a button to press on the Noco to boost charge as their manual recommends. I read the manual and there is no such button.

But I am sure the question was answered with a couple responses to my question saying "just hook up a Noco Genius 10 and you will be good". It has to be that actually boost charge is the minimal requirement and going into the later stages of charging won't cause harm.

I still say the Lifeline manual is horrible. The performance of these batteries has been outstanding, but the manual assumes understanding the subject. They could have said "any good quality AGM battery changer will do what is needed" in additional to the technical discussion.

Some responses seemed to not understand I was talking about maintaining batteries outside of the camper (maybe because I said "in storage" which could mean when the camper is in storage). I took the batteries out for the winter and they are inside, not in the camper. I do have solar but 1) I took the batteries out for the winter, and 2) the camper is in covered storage so won't get sunlight.

I am grateful for the help! Thanks for the help. This one really had me confused. Finally I have this resolved after reading that manual quote over and over.

In the past I have never had a period between camping trips long enough for the batteries to discharge to the 12.5 volts when the boost charge is needed. But with covid the camper has been in storage (and the batteries inside) for... it's actually (hard to believe) 1 1/2 years now, and finally the batteries have drained to 12.5 volts so I need to boost them. Although now I am concerned that the manual says to boost charge every 90 days *or* at 12.5 volts. I now realize that could be interpreted as whichever happens first or interpreted as whichever happens last. I assumed it meant I was ok as long as the batteries stay above 12.5 which I have been checking regularly. I hope I have not killed the batteries by leaving them for 1.5 years even though they were above 12.5 volts.

[2112]

I wonder what bobbolotune took away from all this. Maybe he'll come back and tell us what converter is installed in his TC.

Or maybe he ran away pulling his hair out, never to be seen again!