AGM Battery Charging THE PRIME DIRECTIVE

[MEXICOWANDERER]

I have gotten several communications about AGM battery maintenance. Using solar voltaic charging.

The big error I read is that the subject of total and complete recharging is not mentioned. And that is the # 1 most important mandatory requirement in AGM management.

If panels cannot do it and your electricity charger cannot do it you are condemning the battery.

The battery must be subjected to enough power to allow resistance to rise so that applying 14.4 volts across the battery...

One group 24 battery allows .4 AMP or less into the battery

Group 27 or 31 .5 amp

GC220 1.1 amp

Multiple batteries? Add each additional battery. Four golf car batteries -- 480 amp hour total = 2.2 amps maximum at 14.4 volts

Forget amo hour counting, slide rules or hocus pocus -- one half amp per hundred ampere hours at 14.4 volts. That's the battery's law not mine.

And this is a CHEMICAL matter, so time spent discharge is critical. Cycled to 50% every day is not as significant as cycling to 50% and then allowing the battery to remain at 50% level for days on end.

The CLOSER you can recover to that 1/2% flow of amperage the longer you can go without actually reaching the half percent at 14.4.

The deeper the discharge the more critical it becomes

It's exactly like radiation dosage. Accumulation is far more important than intensity or time. Only in this case it is depth of discharge and time spent at depth. A battery that is discharged to only 70% total capacity and then spending many weeks at that level is affected every bit as much as a battery that is discharged to 40% state of charge for 10 days.

But no matter what getting the battery at 14.4 volts and one half of one percent amp hour capacity amperage flow is key.

A measly 400 watt megawatt power supply can take over when your converter falls flat on it's face delivering less than 35 amps and the megawatt which is set a 14.4 volts will finish the job.

[MEXICOWANDERER]

One of the last things I purchased from the Lockheed surplus auction sale in Lancaster was a 115 pound transformer with secondary windings that look to be around 12 AWG. Center tapped transformer with six Hx connections.

It took me several hours but I managed to configure it as close to 2.666 rectified DC output as I could.

This is my inner cell balancer for my 12-cell series parallel bank. The weak sister cell out of 24 has been disconnected from it's sister by means of a four 3/8" bolt plate so it is isolated.

Individual cell management is about as thorough as a person can get.

An IR pistol even the Harbor Fright model is useful to scan cells in a jar and detect a warmer cell.

It's less damaging to slightly overcharge an absorbed glass mat battery than it is to undercharge it chronically. This does not give license to go hog wild with the charging but may lend weight to deciding where to compromise.

[Itinerant1]

brulaz wrote:

Itinerant1 wrote:

...
I'm using the PT100 and it does integrate nicely with the Magnum inverter/ charger (hybrid) following the settings set throught the Me-Arc. This is with GBS LiFePo4 Batteries which have their own EMS CPU (shunt and more) so no BMK.
...

Off-topic, but I gotta ask:

GBS makes LiFeMnPO4 batteries, but I've never seen them advertise their own BMS (or EMS). Could you provide more detail about your BMS and/or where you got the system?

I suppose the basic idea is the same: like Mex says, you don't want to overcharge an AGM (or undercharge it). And you can use something like Magnum's BMK to be sure you don't. A Li battery's BMS provides the same function and cell balancing as well as other protections, depending upon the BMS.

Heck, for my 24V system I even have a Victron Battery Balancer that ensures the two 12V banks in series are charged properly (they are different brands and ages). A Li BMS should do the same but at the individual cell level.

I purchased and had it installed at Starlight Solar in Yuma. Yes same concept as Mex said about AGMs. Without going into the weeds on this thread I suppose the difference is what the end user sets their own charging parameters as long as the charging source that has adjustability in settings. If anything happens that would cause conditions beyond programmed limits, the BMS will disconnect the charge source or loads.

Inside the trailer.


Here they explain their BMS.
https://www.elitepowersolutions.com/bms/

[brulaz]

Itinerant1 wrote:

...
I'm using the PT100 and it does integrate nicely with the Magnum inverter/ charger (hybrid) following the settings set throught the Me-Arc. This is with GBS LiFePo4 Batteries which have their own EMS CPU (shunt and more) so no BMK.
...

Off-topic, but I gotta ask:

GBS makes LiFeMnPO4 batteries, but I've never seen them advertise their own BMS (or EMS). Could you provide more detail about your BMS and/or where you got the system?

I suppose the basic idea is the same: like Mex says, you don't want to overcharge an AGM (or undercharge it). And you can use something like Magnum's BMK to be sure you don't. A Li battery's BMS provides the same function and cell balancing as well as other protections, depending upon the BMS.

Heck, for my 24V system I even have a Victron Battery Balancer that ensures the two 12V banks in series are charged properly (they are different brands and ages). A Li BMS should do the same but at the individual cell level.

[jharrell]

Itinerant1 wrote:

I'm using the PT100 and it does integrate nicely with the Magnum inverter/ charger (hybrid) following the settings set throught the Me-Arc. This is with GBS LiFePo4 Batteries which have their own EMS CPU (shunt and more) so no BMK.
The PT100 will work with 12v panels except they need to be in series. Mine are 160w (22.50 VOC) panels, 2 in series 4 sets parallel to combiner box, 1,280w. On occasion I will get P04 code which is "Power Limited" (Internal Frequency) happens at +/- 1,150w _ 75-80a area. It's been in service for 2 years now fulltime with no apparent problems.
I spoke with the installer and some systems don't like the PT100 with the lower voltage from panels and he corrected the issue, don't know if that was using a different controller or added panels in series.

I wish Magnum would do a smaller 50-60 amp controller that can do 12v panels. The other thing that kept me away from it was its physical size and mounting requirements (must be mounted vertically, 15" tall with 1" above, 6" below clearance). Magnum is making a small 10a MPPT controller now but I think they are just rebranding something else as it doesn't integrate on their network either.

I actually really like my Tristar MPPT, temp corrected, fully programmable, passive cooling, Ethernet with built in web page and modbus for monitoring and 97% efficiency at 13 Vmp. Has to use a separate remote display since it doesn't integrate with the Magnum remote, but I haven't bothered since I watch it on my computer.

[Itinerant1]

jharrell wrote:


The PT-100 has nice integration to be sure, I would have gone with it except that it won't use panels below 24V on a 12V system. I have 12V (20 VOC) panels in parallel and didn't want to go to series yet, so I went with a Tristar MPPT 60 which has no issue.

Works ok with two independent systems, they basically communicate with voltage, have the solar set slightly higher for charge settings so it tends to be dominant but when batteries are down both go into bulk and both contribute.

The Magnum network is actually not that complicated, just a RS-485 bus with the inverter as master sending it state at 10hz, the remote sends its config right after, then BMK and AGS at 1hz, not sure about PT-100 probably similar to BMK. I have written some software to display the info on a web page using a $5 USB dongle and a Raspberry pi. I also show my Tristar info on the same page as it has ethernet and does modbus.

I'm using the PT100 and it does integrate nicely with the Magnum inverter/ charger (hybrid) following the settings set throught the Me-Arc. This is with GBS LiFePo4 Batteries which have their own EMS CPU (shunt and more) so no BMK.
The PT100 will work with 12v panels except they need to be in series. Mine are 160w (22.50 VOC) panels, 2 in series 4 sets parallel to combiner box, 1,280w. On occasion I will get P04 code which is "Power Limited" (Internal Frequency) happens at +/- 1,150w _ 75-80a area. It's been in service for 2 years now fulltime with no apparent problems.
I spoke with the installer and some systems don't like the PT100 with the lower voltage from panels and he corrected the issue, don't know if that was using a different controller or added panels in series.

[jharrell]

brulaz wrote:
WRT the Magnum inverter/charger and BMK+shunt:

Apparently Magnum's MPPT solar charger can be networked in along with the BMK+shunt and ARC (advanced remote control). It can be controlled by the ARC and inverter/charger settings so the BMK's estimate of battery SOC can be used to terminate absorb from solar charging as well as from shorepower charging.

But if instead you use a NON-Magnum, NON-networked solar charger, things might go awry with the Magnum's logic?

Pretty complicated networked system:

The PT-100 has nice integration to be sure, I would have gone with it except that it won't use panels below 24V on a 12V system. I have 12V (20 VOC) panels in parallel and didn't want to go to series yet, so I went with a Tristar MPPT 60 which has no issue.

Works ok with two independent systems, they basically communicate with voltage, have the solar set slightly higher for charge settings so it tends to be dominant but when batteries are down both go into bulk and both contribute.

The Magnum network is actually not that complicated, just a RS-485 bus with the inverter as master sending it state at 10hz, the remote sends its config right after, then BMK and AGS at 1hz, not sure about PT-100 probably similar to BMK. I have written some software to display the info on a web page using a $5 USB dongle and a Raspberry pi. I also show my Tristar info on the same page as it has ethernet and does modbus.

[JimK-NY]

It is too bad I did not read this years ago and understand how important it is to properly charge AGM batteries.

I only had a simple single stage charge controller which was set at 13.6 v regardless of temperature. I am sure a great many days that I used my RV I did not full charge the batteries even to 13.6. The few times I had a 110v hook up I may not have adequately charged. The cheap single stage charger floated at 13.3 v. There were lots of times I did not reach that level because the charger cut way back on charging current well before 13.3 v.

I used my AGM batteries for 2 years as a full timer and then about 3 months a year for the next 5 years. I tested the capacity at 6 1/2 years and they had full capacity within my testing error using tungsten light bulbs. I then got a 3 stage charge controller. Now at 7 1/2 years the batteries lost substantial capacity. Rather than try a regeneration cycle, I replaced them yesterday. I wonder how long they would have lasted if I had properly charged them at least once in a while.

[brulaz]

pianotuna wrote:
Hi brulaz,

No, I am shunt free.

All I can say is I get to 0.5 amps per 100 amp-hours of capacity.
...

My Rogue will terminate absorb when its current output drops to ? amps. Think I have the value set to 0.8% Ah + parasitic current draw.
Something like that.

But when boondocking and the loads are higher, absorb current never drops that low, so absorb is terminated by timer instead. So after 2 hours at absorb it drops to float, then to mppt and then back to absorb mode for another 2 hours, repeat. Prolly not *that* bad for the batteries but also not what the battery manufacturer recommends. And these are not AGMs.

My daily logs from several years ago show the Rogue at absorb V for as much as 7 hrs a day when boondocking. With my current system it can be 3-5 hrs per day at absorb V when boondocking.

A charger (solar and/or shorepower) that limits the time at absorb V so as not to overcharge the batteries, like that networked Magnum system, would be an improvement. But pretty pricey I expect. If we were to spend the big bucks I'd prolly move to LiFePO4 (with built-in BMS!) instead.:B

[MEXICOWANDERER]

Americans have ZERO experience with authentic Mexican frijoles de la olla. Compared to the garbage that Americans and most urban Mexicans are eating these days, the real McCoy is as different as comparing Tony Roma ribs to a McSynthoBurger. It's the smoke flavoring, the uneven cooking leaving part of the pot contents soft and creamy and others making crusty beans that make this dish and genuine hand patted from field corn rolled by hand and cooked over a pottery slab and smoky fire tortillas something I can gladly feast on five meals a week.

Even citified tortillas and blender refried beans in Mexico taste like @#$%&!

When China cannot build a jet engine they sure as hell cannot build a good AGM battery. FOREIGN SUPERVISION and machinery is needed to build a decent Chinese AGM battery. China's new class of "silent" electric submarines USE BATTERIES MADE IN INDIA. Using EXIDE technology.

Workers Division Number 6502 in Smoking Tailpipe Dragon Factory number three cannot compete now or in my lifetime with Concorde battery. The entire product philosophy is different. Four Wal-Mart $60 tires versus a single $85 Michelin.

I need to buy an electrical tool. I have enough money to buy a forty dollar tool. I know better. The project can wait until I save and buy an eighty dollar tool. I have created enough needless land fill in my lifetime.

I love this analogy
I have purchased fifty dollar meals that were a bargain and have been ripped-off spending two dollars for lunch.

I am going to slip-on a pair of seventeen-year-old Dickies trousers, and go to work. Yeah thirty dollars hurt seventeen years ago -- but I got over it...

[pianotuna]

Hi,

I unplugged the RV, turned off all loads (master disconnect switch). Blue Sky showing 1.7 amps for 556 amp-hours of battery bank in float.

MrWizard wrote:
To know the amps charger into the battery
Install a separate amp meter for the battery,
Or
Turn off all 12dc loads, lights, water pump etc.. Turn off any stand alone inverter, except the fridge parasitic control
And see what your Magnum displays says
The low milliamp draw of the fridge will be negligbile
The display will reflect the charge amps

[brulaz]

pianotuna wrote:

...
May I ask you to reduce the width of your picture--it makes reading the thread hard when it is so wide. (I use 375)

Thanks. Was wondering what to do about that.
375 it is.

[pianotuna]

Hi brulaz,

No, I am shunt free.

All I can say is I get to 0.5 amps per 100 amp-hours of capacity.

May I ask you to reduce the width of your picture--it makes reading the thread hard when it is so wide. (I use 375)

[brulaz]

pianotuna wrote:
My Magnum plays well with my Blue Sky 3024di solar controller.

You must have the BlueSky IPN remote with current shunt so the Bluesky solar controller can use that to determine when to terminate absorb.

Do you also have the Magnum BKM with current shunt so the Magnum can determine when to terminate absorb when on shorepower?

Prolly can't network the BlueSky and Magnum together because of proprietary protocols. AFAIK with an All Magnum networked system you need only one shunt and both networked chargers (solar & shorepower) can use that current & SOC info to terminate absorb.

Prolly Victron and other big players can do this too nowadays, but the technology has been moving so fast I'm having trouble keeping up with it.

[MrWizard]

To know the amps charger into the battery
Install a separate amp meter for the battery,
Or
Turn off all 12dc loads, lights, water pump etc.. Turn off any stand alone inverter, except the fridge parasitic control
And see what your Magnum displays says
The low milliamp draw of the fridge will be negligbile
The display will reflect the charge amps