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Old 01-12-2018, 05:29 PM   #1
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Default Lead acid charging voltages

Harry (hbn7hj) has a discussion going about the often misunderstood 50% rule for lead acid batteries in which he has a quote from the always interesting "handybob", that many of us have spent lots of time reading his articles in the past. I hadn't checked in on him lately, so I used Harry's link to go look at some of his more current, 2018, preachings. As always, they are as entertaining as informative.

Handybob's specialty is living off of solar and batteries, so sort of, kinda, applies to how most of use our vans. No regular generator or shore power options for him.

He likes wet cells, like many off grid solar users do, and some very specific products for controllers, monitors, etc.

His recent articles described early battery failures, which kind of surprised me because of his charging pickyness. He attributes the failures to too high of charge voltage being recommended by the battery manufacutrers, particularly when they start going up over 14.6v absorption Handybob attributes the very high recommendations to an overreaction to the chronic undercharging that has happened in the past on nearly all systems, which I totally agree with.

In typical handybob form, he kind of lumped a bunch of stuff together in saying he would never, ever, put a wet cell over 14.6v or AGM over 14.4v, which isn't inherently bad, IMO, but probably isn't completely right either in a lot of cases.

I think a lot of the higher voltage things started about 10 years ago when folks like Trojan started showing 14.7v absorption voltages as being desirable. It was kind of odd to me how they presented it in their charging tables, as they used 14.7v for a "daily charge", but 14.3v for "absorption charge" in another line. I called them and got a bunch of different answers to what it was all about, and after also talking to some local golf cart shops, it seemed to make some sense.

It appears that the higher voltage was directly aimed at batteries that are cycled fairly deeply, every day, and need to be ready to go after overnight. They also need to have a reliable charging source to give that voltage for the right amount of time without overcharging. In other words, this is for golf courses because the 14.4v charging voltage couldn't get them all the way full, to give best capacity and life, in the time available. Trojan has even add a short 15+v stage after the absorption as a mini equalize for the daily charged setups like golf carts now

As everything battery seems to be, the whole thing quickly spread to pretty much all applications, regardless if it was correct or not. In particular, I think solar is one of the application where it often not a good idea to go with the higher voltages, so that would explain why handybob came to his conclusions.

We have seen first hand, in repeated tests on our 300 watt system, that there are conditions that can make the controller mess up the voltage to the batteries, to the high side, and it is worse if the absorption is set to more than 14.3v. In our case it only happens in the no man's land of charging between about 80% full and 100% full, where controller is in full absorption voltage, but if the solar input conditions vary with clouds, shade, whatever, the panels may not be able supply enough energy to hold that full absorption voltage. If the controller doesn't see absorption full voltage, the absorption timer does not run, even though it may be only .1v below setpoint. We saw ours run 14.5-14.6 for many hours on essentially full batteries because there were clouds holding down output, and the small van loads were enough to drop the voltage. It got even worse with compressor frig because on many cycles, it would drop the voltage enough to put it in bulk again. If you put 14.6v on a wet cell all for 8 hours, it is going to use a lot of water, and an AGM will start to dry out. This is what had to be happening with handybob, it think, but it may have also had some other causes contributing. He mentioned the controllers he uses having "calculated absorption times", which says no shunt, so no accurate stopping of absorption stage. With the higher voltage, solar conditions would leave him in bulk for a long time, so the calculated absorption time would also likely go long because of that. Lowering the voltage made his system react better because it could hold the 14.4v easier, and thus got more accurate absorption times, when he has enough capacity.

Hanyybob states he likes using the Trimetric % returned AH to determine full, which isn't horrible but not nearly as accurate as measuring the actual amps to the batteries. With no shunt, he has no automatic voltage reduction when the batteries are full, except for the internal timers of the controllers.

The solar overvoltaging thing is very hard to address completely, I think. I know we have not come up with a foolproof way to this point. If we are getting good sun nearly every day and not doing any driving, I will set the solar absorption to 14.4v, and it will get there and go to float well. We do have a problem that the Blue Sky controller will go back into absorption if the voltage drops below float voltage, so in the later afternoon a cloud can go over and the frig turn on and it rebulks and holds up the voltage above float when the cloud goes away or the frig goes off. I normally set the float voltage low, a bit below where the full batteries run, at about 12.7v so that is will not rebulk once full and in float so easily. Blue Sky says they will addressing the rebulk in future controllers by lowering the rebulk threshold to 12.8v.

On days where we know that there isn't going to be enough sun to have solar run a full charge cycle because it won't hold voltage, I often will turn the absorption voltage down to under the gassing point of the AGM batteries, usually 13.9v.

I wish we didn't need to do this, but without more sophisticated control, the variable input is difficult to address.

For the shore charger, it is a lot easier because there is always enough power to hold the voltages up where they are set. The "daily charge" thing can apply here though, if you chose to do it, and it may help especially if you have a smallish charger. If we are doing longer offgrid times and aren't able to get full on solar regularly because of conditions, I will use 14.5v for absorption to give bit of a boost to the charging to recover better from mid state of charge cycling. If we anticipate longer shore power stays, storage, or are getting full with driving and solar, the absorption is at 14.2-14.3v. It is really very rare that we would turn up to the 14.5v because the solar and even tiny amounts of driving get us full most of the time.

I think all of this also is a good reminder that for many of us it is important to know when the coach batteries are full when driving, so they can be shut off to prevent them from seeing high voltage all day.

The handybob articles are the first that I remember seeing about being careful about the new higher recommendation, but I think we will be seeing more if it in the future, as the higher voltages will likely tilt the battery damage ratio of undercharge to overcharge toward overcharging.
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Old 01-12-2018, 06:11 PM   #2
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Booster, thanks for the summary! I couldn't make sense of what he was saying and was going to try again this evening. I will still read it again now that you have explained some things.
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Old 01-15-2018, 02:26 AM   #3
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I watched one "handybob" video and concluded he is an idiot who will likely die in a van fire. But that's just like, my opinion man.
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Old 01-15-2018, 02:51 AM   #4
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.

Lol

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Old 01-15-2018, 07:55 AM   #5
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If it wasn't for Handybob's rant I'd still be trying to get by on 3/4 charged batteries so he has made all the difference for me and I do appreciate it. I wouldn't have figured it out on my own.

The higher voltages work fine for me so I think I'll stick with them. I seldom see full charge and full sun for hours on end so that may be the difference. I have one manual charger set for 15.4 volts on a group 27 battery so I'll pay attention to that one. I may cut it down to 14.8 volts. Anyhow, I owe him one.

Now if I could only figure out the 1.2 volt drop between my batteries and TV. It isn't resistive because it doesn't vary with current nor did it change when I parallel it with 6 gauge. Thinking it had to be in the ground path I put six gauge in for that but it is still there. The TV cuts off at 11.4. I quit trying to figure it out and put in a voltage stabilizer but one of these days I may reopen that research project. It can't be that difficult.

Most of the people I meet dry camping don't have a clue. They run the generator to watch evening TV and charge the battery with a 13.7 volt converter. One of the camp hosts couldn't figure out why he had to run the truck engine or generator to open a slide out after a day's driving. Handybob's rant would tell him.

Between Booster and Handybob I get all the info I need!

Harry 2006RB LazyDaze and 2003 C190P Roadtrek.
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Old 01-15-2018, 03:52 PM   #6
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Any discussion of Handybob always has a wide variety of opinions, that is for certain.

I certainly do think that his personality and presentation get in the way both his own ability to expand his knowledge and to explain his ideas to others, which is unfortunate, but the way he is.

I would be the last one to say to take Handybob's ideas as gospel facts, as I do think he misapplies some things and misses others, but he does understand, and preach, some things that many of us also support (50% rule for instance). Most of his stuff is derived from offgrid stationary solar applications like his, and I do think he tends to apply it to other applications where it might not be as applicable.

A read of Handybob's writings can be very entertaining as long as you keep in mind that no matter how he presents things as facts, they are really opinions and just another piece of the puzzle we all are working on all the time.
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Old 01-24-2018, 04:06 PM   #7
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I have had a bit of time between snow and cold adventures here in the frozen north, so I went to the Trojan site to see what they are currently saying about charging their deep cycle batteries, in relation to Handybob's statements. There have been a few small changes since the last time I looked a couple of years ago.

Trojan specializes in deep cycle wet cells, and does a very good job of it, IMO. The pair of 260ah six volt GC batteries we had tested as new after 5 years when did the switch to AGM. I will show the parameters they recommend for AGM, but they are very normal middle of the road, and likely haven't been tweaked to the extent of their wet cell recommendations. Lifeline has their AGM recommendations more refined, and IMO are more detailed for how to use in the real world.

Handybob's big complaint was about the "new" higher charge voltage profiles being recommended by various, particularly wet cell, manufacturers. AFAIK, Trojan was among the first of GC type suppliers to go to higher voltages a number of years ago. Forklift charging profiles have been at higher voltages for as long as I remember, though, for most all of them.

Handybob says that he thinks the higher voltage is in response to the chronic undercharge that most deep cycle batteries get with nearly all of the "smart" multistage chargers, and for the most part I agree with him, especially in RV and boat applications. Most of us with mobile battery systems in our vans don't have the luxury of big, expensive, very high power and accurate control, chargers every night like golf courses do for their carts. Most of us don't need a charge every day, either, like a cart does, so the application is different besides. Throw in the variability and low output of solar (which is 100% of Handybob's charging most times) and everything is messed up even more.

Here is what Trojan says about charging their deep cycle wet cells.



It shows the now very common 14.7v absorption stage, which they have for several years now. The used to also show a 14.3v for absorption if the charging was not a "daily" charge (in their terminology). This likely would indicate a golf cart charged every day would use the 14.7v and a battery charged less frequently, and that had enough time available for a longer charge cycle would use the 14.3v. I know from personal testing, confirmed by specific gravity and end of charge amps that both of those voltages will get the batteries full. The 14.7v charge will be considerably faster, though, and surprisingly they will use about the same amount of water, as long as the charges are ended at the right time. I think it is important to point out that the end of charge amps usually will be significantly higher for the 14.7v than at 14.3v so if you have your Trimetric set for 1.5%C ending amps at 14.3v, you will almost certainly overcharge the batteries at 14.7v getting to the same ending amp reading. You need to watch the amps at the end of charge to determine what appears to be the best balance of water use and charge times at each voltage to get the best results.

The Trojan description also shows a stage after the absorption stage. Essentially all of us don't have a separate stage available for that, and Handybob didn't mention how he was doing it, or I missed it. The first instinct is to just increase the absorption voltage to the higher (16+v) voltage called out for the new stage. THIS IS NOT THE THING TO DO, IMO. The absorption stage is constant voltage and ramps up to that voltage based on the battery acceptance until it levels off at setpoint. The new stage that Trojan call out is Constant Current, which is a totally different thing. The constant current will limit the amount of energy going into the battery, and thus the heat and gassing, compared to using the constant voltage, likely much higher current. Equalizing is also supposed to be constant current, but many chargers don't let you set it. This stage terminates off of voltage not current, so very different than most of us are used to seeing. This may well be at least part of what helped kill of Handybob's batteries.

Here is what the recommended Trojan wet cell profile looks like in graph form.

Attached Images
File Type: jpg Trojan GC charge description.jpg (93.7 KB, 87 views)
File Type: jpg Trojan GC charge profile.jpg (36.7 KB, 90 views)
File Type: jpg Trojan AGM charge description.jpg (89.7 KB, 2 views)
File Type: jpg Trojan AGM charge profile.jpg (32.3 KB, 2 views)
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Old 01-24-2018, 05:41 PM   #8
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So, with all of this "stuff" going on, what could possibly go wrong that would hurt your batteries?

Here is the profile for the wet cells again, with some zones marked.



The bottom of the blue zone is 13.2v and is where Trojan wants to float a full battery. In theory, you don't want to be above 13.2v with a full battery for any significant amount of time. This is why a 13.8v fixed charger will "cook" you battery over time. I think it can also show how various conditions and system differences can hard on batteries.

If you had a charger that was capable of doing the Trojan profile, you would start charging at a fairly low voltage, constant current of 10-13%C. As the battery charged, the voltage would climb with the current staying the same until it got to the 14.7v (depending on how big the charger capacity is, current might be lower by then). The charger would then go into fixed voltage of 14.7v and continue charging, and the current would start to drop until it got to the 1-3%C stage transition point. The charger would then switch back to supplying constant current at the 1-3%C amps and the voltage would start to climb above the 14.7v until it got the 16.2v setpoint (if it is set to the high end of the spec) with the same 1-3%C current. The charger would then go to float if it were to be in longer term storage, or just shut off if the battery will be used the next day.

I don't know of any charger that we could use in a van that would do even most of that cycle, unless you eliminate the final stage.

If the cycle shown, or one shortened by not using the last stage, is followed, I don't think there is much chance for battery damage at all because high voltage is never applied to a less than full battery.

What you really don't want to happen is to get the charge cycle "stuck" in one of the 3 outlined areas when the battery is full, as that will put high voltage on a full battery and could cause damage, which will get worse, I think the further up you go in the voltage.

We use the shortened, normal type, charge cycle in our system, which is all controlled by monitoring amps to the batteries, so if all works right we won't ever be putting the higher voltage on full batteries.

* Shore charger will go to float as soon as the battery amps is low no matter what the time, so won't overcharge. Very few shore chargers work this way, however.

* We monitor the battery amps with a meter on the dash when driving, so we can shut off the alternator charging when the batteries are full, so no overcharging. We had to make this capability ourselves.

* Then there is the solar which has the capability to mess it all up, and is likely why Handybob has issues with the higher charge voltage recommendations.

Our solar controller, and many others, runs off a shunt like the shore charger, so you would think that you could not have an over or under charge situation. True for under charge if you get enough sun, but certainly not true for over charge.

The questions are what can cause the over charge situation and what you can do about it.

* If you solar controller is a timer only version, it will put a full voltage, full length, charge cycle on a full battery like you would have coming off of shore power. I think this is quite common.

* If you solar controller runs of a shunt (good), but doesn't let you set the minimum absorption time to under 5-10 minutes (or you don't set it properly), it will put full voltage on the batteries for as long as the timer is set for, even once the batteries are full. This is likely not very common.

* What happens to us, and I assume a lot of other people, is that the solar messes itself up no matter how you set it, even with a good shunt based system. You can quite easily get "trapped" in one of the circled higher voltage zones for very long periods of time, putting high voltage on full battery.

It all comes down to if the solar is putting out enough power to run whatever loads are on in the van and supply enough power to the batteries to trigger the transition to float. If the solar is low on output compared to those conditions, the output voltage of the controller will never get high enough to trigger the transition to float. We have seen our system sit at .1-.2v under absorption voltage for essentially all day, in sun conditions and use amounts that are being used. It can run there until the maximum adsorption timer is triggered, which is usually a long time on solar systems because the are slow.

If we start out with full batteries, the solar will go right to float when the sun comes up, which is good, but if sun is poor and the frig comes on, the solar will go back into bulk. This is built into the unit and can not be disable, eg lock into float once it is triggered once in a day. Our solar will go back into bulk any time the battery voltage drops below the float setting of the solar, which normally would be 13.2v for us. So we can be in float, cloud comes over and frig turns on, voltage drops to about 12.9 before the batteries start to pick up the load, and suddenly we are back in absorption stage. Frig turns off and the voltage goes up from reduced load to 14.0 volts, but never gets to 14.3v to trigger going back into float. Our "solution" sucks at best, and is to turn down the float voltage to 12.6-12.7v to keep it from going back into bulk. It does work to prevent the rebulking, but it also makes it so the batteries are not held at 100% full with the solar running the power requirements.

We have a Blue Sky controller, and I have talked to them about this, and was told the the new engineering mgr had just recently told them that all new products or major upgrades would make the rebulk happen at 12.8v, which would help, but I do wish it could be set to only do one full cycle per day unless you disable that feature. If you ran a big load and used up some battery on a decent sun day, you would want to do a recharge cycle.

If anyone has any details of how other brands handle this situation, it would be interesting to hear how they do it.

I think this is what bit Handybob in the batteries . If he had setup to run with his top voltage of 16+v, there would be lots more instances when the system would get "stuck" and applying too much voltage to his batteries. From his descriptions, it also sounds like he is not using amps to change changing stages, so he could easily be overcharging by using the "calculated" absorb times that most timed controllers use, and at increased voltages, bad things happen faster. I think.

All of these things also apply to AGM batteries, too, I think, just not as radically, as the highest voltage most recommend is in the 14.3-14.6v range.

Overcharging or undercharging in our vans is very, very, common, I think. based on the shore, solar chargers and uncontrolled alternator charging we almost all deal with. Which you get (or when you get either) will come down to what equipment you have, and your use patterns. It is not particularly cheap or easy to get rid of the issues, but they can be reduced with some less extreme measures.
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Old 01-24-2018, 09:27 PM   #9
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Quote:
Originally Posted by booster View Post

Here is the profile for the wet cells again, with some zones marked.
As usual, I'm hanging on your every word. Did you intend to include a diagram? I don't see it for this last post, and I'm sure it would be helpful.
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Old 01-24-2018, 09:36 PM   #10
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Quote:
Originally Posted by Saldar View Post
As usual, I'm hanging on your every word. Did you intend to include a diagram? I don't see it for this last post, and I'm sure it would be helpful.
Interesting, the diagram shows on my computer right after the line you quote. Did the two in the previous quote show up? None of them are showing as attachments at the bottom of the page, but are showing in the post itself, which is odd. I will put the diagram in here, again, to see if it makes it.

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