Using Solar to trickle charge series batteries in parallel

[booster]

You have to be careful not to mix the wet cell equalization need with the AGM batteries care. If on a good charger, AGM batteries should not need to be equalized and many say you shouldn't equalize ever as it can wreck them. Lifeline is the major exception in that they say you can equalize/condition the batteries but only should do it if they are showing signs of capacity loss. Our AGMs have been hanging under the van for 5 years now without being touched and still have the charge characteristics and very low float amps as when new. Tested capacity is also the same.


Nearly all the maintenance on batteries can be eliminated by having good charging equipment, IMO.

[markopolo]

Originally Posted by booster

................... Nearly all the maintenance on batteries can be eliminated by having good charging equipment, IMO.

That sums it up nicely.

Once you understand what it takes to best charge and maintain a battery then you purchase suitable equipment. It will have programmable parameters and terminate charging based on ending amps. Look at Magnum & Samlex etc.

[JohnnyCLE]

That is encouraging. Was this accomplished by tuning your RV charging systems to "do their thing properly" or was it though some level of manual outside care and feeding?

I will quickly get a battery monitoring system installed to get better data. But rereading your great thread on "What a Battery Monitor may not tell you" it seems like some intervention may sometimes be needed.

I am guilty of being a bit of a "lazy farmer", willing to work hard to try to get things to theoretically automatically take care of themselves. What is the optimal state of the industry?

Interesting how different batteries react. Would lithium batteries with individual BMSs behave better? Self sensing what is needed and taking the steps necessary to stay in optimum health as long as a charge is available? Quite a bit to learn here! And fascinating.

[booster]

Originally Posted by JohnnyCLE

That is encouraging. Was this accomplished by tuning your RV charging systems to "do their thing properly" or was it though some level of manual outside care and feeding?

I will quickly get a battery monitoring system installed to get better data. But rereading your great thread on "What a Battery Monitor may not tell you" it seems like some intervention may sometimes be needed.

I am guilty of being a bit of a "lazy farmer", willing to work hard to try to get things to theoretically automatically take care of themselves. What is the optimal state of the industry?

Interesting how different batteries react. Would lithium batteries with individual BMSs behave better? Self sensing what is needed and taking the steps necessary to stay in optimum health as long as a charge is available? Quite a bit to learn here! And fascinating.

Our system requires essentially no real interventions, but I do monitor it closely just because it is my nature and also good from and education standpoint for me. There are only two minor exceptions to the no interventions, both of which are no effort things. Main one is that there is no equipment available readily that can accurately control the alternator charging, so I have an ammeter on the dash to show battery charge amps and a switch to shut off the charging to the coach. When the amps get into a level that the solar can finish I just shut off the engine charging. It is a big range of like 10 amps so no need to watch closely. Second is a glitch built into the Magnum charger that can prevent a full charge cycle when plugging into shore power if the batteries are over 90% full. It goes to float based on voltage at that point. Not a big deal if it will get a full charge later on but a couple of button pushes on the remote will start a full charge if I choose to.



The no interventions but top charging was accomplished by using a shore charger and solar charger that run off their internal battery monitors with an external shunt input. When programmed correctly, they will always give a full charge without overcharging with no interventions needed.



It was not an inexpensive system to put together, but it works well and has been reliable for us. Not having to worry about it is a big benefit for us.


The top of the line, and expensive, lithium systems certainly seem to take good care of the themselves. The biggest issues many times is the convoluted ways to recover them into running state after a self shutdown for temp, voltage, etc. The can't be used or stored in cold winter conditions, however, so would need to be removed, heated, or have the van in a conditioned area if you are in a cold part of the country. The drop in batteries claim to be totally self protecting and require no special care or equipment, but personally I just don't see how that can be totally correct with how much control is done on the higher end stuff. None of this has been out long enough to know how they will survive longer term and if they will make anywhere near their rated life in real use.

[markopolo]

I'll just add a bit to what Booster posted.

The charging equipment that is installed by RV builders is often mid-range stuff, a one size fits all approach with cost being a deciding factor. You have to replace it if you want precise control.

Lifeline's AGM charging recommendations for deep cycling applications are to charge at least a 0.2C rate until current drops below 0.5% of battery capacity. If you have 200Ah of batteries then charge at least 40A until current drops to 1A. You can't predictably meet that recommendation with any charger that uses profiles or algorithms etc. You have to have a charger that lets you set ending amps or transition to float amps.

Basic 3 stage chargers in RV's run the absorption stage on a timer. The result is under charge or over charge.

Just above that level would be algorithm based profile charging with time limits. The result is less under charge or less over charge than the basic units.

The best charge control comes from chargers that let the user set specific ending or transition amps. The result is a predictably fully charged battery.

Typical use for a BMS with lithium batteries is not charge control. It's a last line of defense to prevent damage from over or under voltage and current and temperature. You still need precise charging and environment control.

[JohnnyCLE]

Thanks for both of those very informative posts. The approach of purposely throttling the least intelligent charging so that a more intelligent charging process can properly finish is brilliant.

Very good information as I consider upgrades to the electrical system. I had come to the conclusion that I might need to upgrade a lot of components to optimize the electrical system for my use case.

I also have to humbly correct a perception I posted earlier which I now know is incorrect. The ZLPower inverter does not show the status of two banks. The different numbers are for two different modes. I was able to get several hours of Dan Neeley's time over the phone. This was quite helpful and he was able to provide a user manual for the ZLPower inverter. The ZLPower remote being used is only a remote switch and not a second 12v charge level reading. The 12v charge level reading comes from a second voltmeter which has tolerances that appear to be relatively useless.

[JohnnyCLE]

The more I begin to understand the subtleties of discharging and charging a bank of batteries I realize that Roadtrek was selling lasers to cavemen in the number of E-Treks which were sold to first time RV owners, like myself. We were sold them and trained in their use by dealer Neanderthals.

The best thing that can said is that, other than batteries, nobody died! The owners manual talks a lot about prepping the fresh water tank but very little of battery care. Most of these RV's were likely put away without a proper recharge. If parked in the driveway they may have been connected to a 15-20amp outdoor outlet. If parked at a storage unit they may have shared a 15amp outlet with the Prevost next door.

People who used them for touring vans with a 4-6 hour finishing drive home likely put them away close to completely charged. People who used them for local tailgating or for weekend soccer tournaments may have put them away empty with only solar to recharge. The suggestion of "run your engine for 30 minutes to get a charge back in" leaves one well short of a full charge. Boondockers may have slowly milked the 12v dry while driving very little every day.

For new users there was very little education and many false expectations set. For experienced users there was little useful instrumentation to know or control what was going on. No wonder batteries got toasted. Because of the series connections as soon as one battery went bad they all needed to be replaced.

Fortunately it seems that all of these problems are correctable with the right instrumentation and management system. The battery balancer helps by leveling abuse and bad care equally across all batteries and by eliminating any imbalances caused by the wiring design. It doesn't correct the lack of visibility, control, or bad operating practices.

Now that I am beginning to understand the issues better I hope to set about correcting them. It seems like the E-Trek is a great platform to start with given it's capacity to carry batteries, weight, space and handling. And there are many new options today which did not exist 5 years ago. Perhaps I was the only new owner who was clueless, but perhaps not!

I do hope to find a use for that solar trickle charge in the end!