Can regular PWM regulator charge AGM batteries?

**inetdog** · 09-18-2014, 08:41 PM

If the CC does not have a custom voltage adjustment, chances are that the default voltage is not suitable for AGMs.
The result would be that you will chronically undercharge the battery.
At least it has temperature compensation (although that will be useless unless it includes a remote temperature sensor to mount at the battery.

If the Float voltage of the CC matches the desired Float voltage of our AGM, then you might get away with it.

The unit appears to be intelligent enough that it could be made capable of setting the stage voltages over the communications interface, but if the manual does not describe how to do that, the feature must not be there.

**Mike90250** · 09-18-2014, 09:31 PM

major name brand PWM controllers have AGM settings, and should work fine if you have enough PV panels to charge the battery.

cheap knock off MPPT controllers may not have AGM settings either, check the specs before you buy. Morningstar has a good example on their web site of how specs should read. Most of their mid & large are capable.

**Bratan** · 09-18-2014, 10:28 PM

Originally posted by Mike90250

major name brand PWM controllers have AGM settings, and should work fine if you have enough PV panels to charge the battery.

cheap knock off MPPT controllers may not have AGM settings either, check the specs before you buy. Morningstar has a good example on their web site of how specs should read. Most of their mid & large are capable.

Thank you, I will check voltage. What is the least expensive controller that can charge AGM?

**jony101** · 09-18-2014, 10:38 PM

When I started in solar I also used an ebay 20 dollar pwm charger to charge both a 75 ah and 145 ah agm battery. never had any problems with the charger or the batteries.
But my pwm charger didnt have an EQ setting, I read that AGM's might not handle that too well, if possible I would disable the EQ setting. What EQ does is pulse high voltage to the cell to reduce deposits on the plates that reduce battery efficiency.
Most PWM have 3 parameters bulk/absorb/float, thats all most batterys require.
For a 100 watt panel PWM is the best way to charge. You would see absolutely no improvement by using an expensive MPPT charger. For MPPT you need a panel that well put out at least 30 volts, like a 200 watt panel or higher.

**inetdog** · 09-19-2014, 03:25 AM

Originally posted by jony101

When I started in solar I also used an ebay 20 dollar pwm charger to charge both a 75 ah and 145 ah agm battery. never had any problems with the charger or the batteries.
But my pwm charger didnt have an EQ setting, I read that AGM's might not handle that too well, if possible I would disable the EQ setting. What EQ does is pulse high voltage to the cell to reduce deposits on the plates that reduce battery efficiency.
Most PWM have 3 parameters bulk/absorb/float, thats all most batterys require.
For a 100 watt panel PWM is the best way to charge. You would see absolutely no improvement by using an expensive MPPT charger. For MPPT you need a panel that well put out at least 30 volts, like a 200 watt panel or higher.

And just why do you think that only high wattage panels have GT level voltages?
Even if you have nothing but 100W panels for 12V battery charging, an MPPT controller will allow you to put two or more panels in series to reduce the wiring cost and complexity.
Also, EQ is not necessarily (or even usually) a pulsed high voltage charge. It can either be just an extended Absorb on some inexpensive CCs or it can be a steady higher than Float voltage which is high enough to drive significant current through fully charged cells to charge other cells in the series string which have not reached 100% SOC yet. Hence the term "equalizing".
Since it is effectively continuing to charge fully charged cells, all of the energy going into those cells ends up as gassing and heat, so the process has to be carefully monitored, especially with sealed (VLRA) battery types.

**Bratan** · 09-19-2014, 11:46 AM

Thanks guys, but now I'm even more confused... Am I going to overcharge or undercharge my battery? For the record it's VMaxxtank SLR125. From specs: MAX. CHARGING VOLTAGE: 14.7V

**Sunking** · 09-19-2014, 01:29 PM

Undercharge if it is set for FLA.

**SunEagle** · 09-19-2014, 01:32 PM

Originally posted by Bratan

Thanks guys, but now I'm even more confused... Am I going to overcharge or undercharge my battery? For the record it's VMaxxtank SLR125. From specs: MAX. CHARGING VOLTAGE: 14.7V

There isn't much on the CC that you listed. It only states it will charge a 12 or 24volt battery and has 4 stages of charging; EQU, Bulk, ABS & Float.

It doesn't indicate what the charge voltage actually is for each of those stages. Hopefully it does not exceed that 14.7v battery limit.

**Bratan** · 09-19-2014, 01:48 PM

Originally posted by SunEagle

There isn't much on the CC that you listed. It only states it will charge a 12 or 24volt battery and has 4 stages of charging; EQU, Bulk, ABS & Float.

It doesn't indicate what the charge voltage actually is for each of those stages. Hopefully it does not exceed that 14.7v battery limit.

Good point, manual that came with CC has more info, I'm gonna study it more closely tonight. But sounds like best way is to hook it up to panel, and when it's fully lit by sun check output voltage, correct? Should it work without battery connected?

**SunEagle** · 09-19-2014, 02:00 PM

Originally posted by Bratan

Good point, manual that came with CC has more info, I'm gonna study it more closely tonight. But sounds like best way is to hook it up to panel, and when it's fully lit by sun check output voltage, correct? Should it work without battery connected?

No. Most chargers will not work properly unless you FIRST connect them to a battery and then to the panels. Doing it the other way could cause the CC to not properly work.

**Bratan** · 09-19-2014, 02:19 PM

Originally posted by SunEagle

No. Most chargers will not work properly unless you FIRST connect them to a battery and then to the panels. Doing it the other way could cause the CC to not properly work.

Ah I see, makes sense, it needs constant power for the microprocessor...

**SunEagle** · 09-19-2014, 02:22 PM

Originally posted by Bratan

Ah I see, makes sense, it needs constant power for the microprocessor...

That and the charger controller needs to know what type of battery voltage it is going to be working with so it can go through the proper set up to for charging.

**Bratan** · 09-24-2014, 02:53 PM

I finally had a chance to hook everything up, and see what CC says. As my battery was already charged it went right to Float mode, and was showing 14.1V. This is higher than recommended voltage which is 13.5-13.7V...
But then I disconnected it and move to another area and this time float charging was at 13.8V...
There seems to be no way to disable or adjust Floating voltage on this charge controller.
I scanned and attached manual.
I found this paragraph particularly worrisome

In floating charge status, voltage of photovoltaic panel is stabilized to the rated voltage of floating
charge (mean value) to limit the charge rate of battery. This charge status is to continuously supplement
the battery and make up the energy loss caused by self-discharge. In the loaded condition, voltage of
floating charge also provides electric energy of photovoltaic panel for load.
Some kinds of batteries are benefited from regular equalizing charge which can stir electrolyte and
balance the voltage of battery to complete chemical reaction. Equalizing charge raises battery voltage
and makes it higher than standard supplemented voltage, and gasifies battery electrolyte.

I think I'm going to try to return it...

Attached Files

LMS Charge Controller.pdf (332.3 KB, 2 views)

**inetdog** · 09-24-2014, 03:03 PM

Originally posted by Bratan

I finally had a chance to hook everything up, and see what CC says. As my battery was already charged it went right to Float mode, and was showing 14.1V. This is higher than recommended voltage which is 13.5-13.7V...
But then I disconnected it and move to another area and this time float charging was at 13.8V...
There seems to be no way to disable or adjust Floating voltage on this charge controller.
I scanned and attached manual.
I found this paragraph particularly worrisome

I think I'm going to try to return it...

All that section is telling you is that you should never apply an equalizing charge voltage to an AGM unless you first check the guidelines of the AGM manufacturer and stay within them. There will always be come gassing inside an AGM at full charge, but if the rate is low enough the hydrogen and oxygen will recombine internally at a pressure lower than the relief valve threshold of the AGM.

You should NOT use any charger that automatically applies an equalizing voltage occasionally and does not allow you to disable that feature.
If the Float voltage is high, but still not in the equalizing range, you definitely want a charger that senses the battery temperature and reduces the voltages as the battery heats up. Otherwise that high float voltage may become too high a voltage for a hot battery.

Can regular PWM regulator charge AGM batteries?

Can regular PWM regulator charge AGM batteries?

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