How configurable a charge controller should be?

[wdc]

Hello, I have the cheap blue PWM charge controller (CC) from ebay, I don't like how little configurable is so I went online to find a better one, I came across an Epever CC (model VS2024A) that is more expensive and, supossedly, better but I found that is as little configurable as my cheap one, basically you can only choose between sealed, flooded and gel battery type and the float voltage, you can't choose the bulk and absortion voltage in both CC, so I wonder: should I trust this kind of CC or should I go for a fully configurable one? is there any advantage on being able to choose every stage voltage by myself or should I let the CC do that for me? thanks!

the cheap blue CC from ebay:

CMTD20%20a.jpg

the Epever CC:
VS2024AU.jpg

[Ampster]

I think there are advantages to having lots of configuration options, if you are using Lithium which have different voltage specs. If you are using Lead Acid, no advantage that I know.

[Mike90250]

you can look at their specs, and see if the pre-programmed voltages & set points will work for you. Also notice if there is an automatic EQ cycle every 30 days and if it can be disabled or run on demand..

[secessus]

The top CC is an on/off controller (sometimes called a "shunt"). It has one configurable voltage setpoint, which for offgrid use would be Vabs. For off-grid, deep cycle use this isn't necessarily a bad thing since it gets around the (larger, IMO) problem of insufficient Absorption duration.

I have no direct experience with the bottom one, though the specs say it is a three-stage PWM with presets for battery type. Looks like a typical low-cost actual PWM. Here is the datasheet (PDF) including the voltage setpoints for the presets.

* If one of the charging profiles on the bottom one lines up with your battery mfg's recommendations I'd use it, particularly if the batteries aren't cycled deeply and daily. If they are cycled deeply the hardcoded absorption duration (undocumented, but typically something insufficient like 2hrs) is probably too short to complete absorption.
* If the charging profiles don't line up or if the batteries are ridden hard I'd use the top one set to your battery mfg's reco for Absorption and tweak the voltage every season to account for temp differences.
* if you want full control on the cheap for ~$60 you could use something like a LS2024B with a PC cable to program exact setpoints. It'd be $75 with the meter/display. Of course by that point you are getting close in price to the small MPPT neighborhood with gear by Victron, EpEver, etc.

One can get around insufficient absorption duration by setting Vfloat == Vabs, but then we could be using the shunt for far less money.

[wdc]

I think there are advantages to having lots of configuration options, if you are using Lithium which have different voltage specs. If you are using Lead Acid, no advantage that I know.

Thanks! I wish I could buy a lithium battery but I have no money even for the 10% of it, LOL.

you can look at their specs, and see if the pre-programmed voltages & set points will work for you. Also notice if there is an automatic EQ cycle every 30 days and if it can be disabled or run on demand..

Thanks! I saw their specs and neither even mention absorbtion stage, the first one only mention equalize and float and the second one boost (bulk?), equalize and float. Either manufacturers don't care about absorbtion at all or they just integrate it into their chips to let the CC handle it.

The top CC is an on/off controller (sometimes called a "shunt"). It has one configurable voltage setpoint, which for offgrid use would be Vabs. For off-grid, deep cycle use this isn't necessarily a bad thing since it gets around the (larger, IMO) problem of insufficient Absorption duration.

I have no direct experience with the bottom one, though the specs say it is a three-stage PWM with presets for battery type. Looks like a typical low-cost actual PWM. Here is the datasheet (PDF) including the voltage setpoints for the presets.

* If one of the charging profiles on the bottom one lines up with your battery mfg's recommendations I'd use it, particularly if the batteries aren't cycled deeply and daily. If they are cycled deeply the hardcoded absorption duration (undocumented, but typically something insufficient like 2hrs) is probably too short to complete absorption.
* If the charging profiles don't line up or if the batteries are ridden hard I'd use the top one set to your battery mfg's reco for Absorption and tweak the voltage every season to account for temp differences.
* if you want full control on the cheap for ~$60 you could use something like a LS2024B with a PC cable to program exact setpoints. It'd be $75 with the meter/display. Of course by that point you are getting close in price to the small MPPT neighborhood with gear by Victron, EpEver, etc.

One can get around insufficient absorption duration by setting Vfloat == Vabs, but then we could be using the shunt for far less money.

Thanks! My old actual battery is dying and I'm seeing bulk time getting shorter every week, that's why I thought "I wish I could make absorbtion time longer", now reading your post I know I was right yesterday when I changed Vfloat from 13,8 to 14,2. Soon I'll have to buy a new battery but I'm having a hard time finding a refillable one, that's why I wanted to buy a better CC, now I'll stick to my "shunt" CC and just keep an eye on float voltage between seasons.

Thanks everybody!

[wdc]

The top CC is an on/off controller (sometimes called a "shunt"). It has one configurable voltage setpoint, which for offgrid use would be Vabs. For off-grid, deep cycle use this isn't necessarily a bad thing since it gets around the (larger, IMO) problem of insufficient Absorption duration.

I have no direct experience with the bottom one, though the specs say it is a three-stage PWM with presets for battery type. Looks like a typical low-cost actual PWM. Here is the datasheet (PDF) including the voltage setpoints for the presets.

* If one of the charging profiles on the bottom one lines up with your battery mfg's recommendations I'd use it, particularly if the batteries aren't cycled deeply and daily. If they are cycled deeply the hardcoded absorption duration (undocumented, but typically something insufficient like 2hrs) is probably too short to complete absorption.
* If the charging profiles don't line up or if the batteries are ridden hard I'd use the top one set to your battery mfg's reco for Absorption and tweak the voltage every season to account for temp differences.
* if you want full control on the cheap for ~$60 you could use something like a LS2024B with a PC cable to program exact setpoints. It'd be $75 with the meter/display. Of course by that point you are getting close in price to the small MPPT neighborhood with gear by Victron, EpEver, etc.

One can get around insufficient absorption duration by setting Vfloat == Vabs, but then we could be using the shunt for far less money.

Hello again, I'm still deciding between buying a FLA or AGM battery, but already bought the bottom one charge controller (waiting for it to arrive). I was reading about healthy AGM batteries and found that those kind of battery should never be equalized to prevent outgassing, but the Epever CC (the bottom one) does have an equalizer stage for sealed batteries (including AGM's), the equalize voltage is 14,6V, should I use the "gel" preset in the CC with an AGM battery because that preset doesn't have an equalizer stage? thanks.

[Mike90250]

You must use the voltages published by your battery manufacturer,

I could make a charge controller and preset voltages all over the place and give them any label I want, as long as it sounds better than every other controller. I'm selling controllers, and can care less about your battery, it was weak anyway.

[wdc]

You must use the voltages published by your battery manufacturer,

I could make a charge controller and preset voltages all over the place and give them any label I want, as long as it sounds better than every other controller. I'm selling controllers, and can care less about your battery, it was weak anyway.

I understand, but the manual of the AGM battery I like says nothing about equalization, and I don't remember any AGM manual saying something about it, do you think AGM's need equalization or not? thanks.

[Mike90250]

AGM's do NOT get EQ'd
Sometimes, if it's acting really sick and a normal charge does not help, you can try extending the absorb time 15 min. But different mfg's have different ways to recover their AGM's

read this:

https://batteryuniversity.com/index.php/learn/article/absorbent_glass_mat_agm

and this
Batteries naturally become warm during charging, but excessive heat may be an indication that there really is something wrong with the battery. Discontinue charging immediately if the battery is hot to the touch. Also discontinue the process if you hear the battery "gassing" — a hissing sound coming from the safety valves.

If it's hot or gassing, STOP CHARGING IMMEDIATELY!

[wdc]

AGM's do NOT get EQ'd
Sometimes, if it's acting really sick and a normal charge does not help, you can try extending the absorb time 15 min. But different mfg's have different ways to recover their AGM's

read this:

https://batteryuniversity.com/index.php/learn/article/absorbent_glass_mat_agm

and this
Batteries naturally become warm during charging, but excessive heat may be an indication that there really is something wrong with the battery. Discontinue charging immediately if the battery is hot to the touch. Also discontinue the process if you hear the battery "gassing" — a hissing sound coming from the safety valves.

If it's hot or gassing, STOP CHARGING IMMEDIATELY!

Thanks, what I don't understand now is why Epever makes a charge controller that has an equalization phase for sealed batteries, AGM are sealed but should not be equalized, then why Epever allows it?

[Mike90250]

Marketing ! Our controller even will EQ your expensive sealed batteries. Buy it.

[wdc]

Marketing ! Our controller even will EQ your expensive sealed batteries. Buy it.

I see, thanks Mike90250, I'll stay away from AGM's for now.

[Mike90250]

I see, thanks Mike90250, I'll stay away from AGM's for now.

Just know what you are getting into. They are fine for their purpose (I just bought a new one for my electric gate)

[wdc]

Just know what you are getting into. They are fine for their purpose (I just bought a new one for my electric gate)

yes, I know. I have too little solar panel power to use AGM, my max current is 13,7 amps at noon and I don't want to buy a smaller than 150Ah battery, so I'll stick with wet cells for now. Thanks.

edit: what do you think about eternal absortion approach? I'm using it with my battery (bulk charging at 14,4V and same to float) and it seems to work, the battery holds charge longer at night.

[secessus]

the Epever CC (the bottom one) does have an equalizer stage for sealed batteries (including AGM's), the equalize voltage is 14,6V, should I use the "gel" preset in the CC with an AGM battery because that preset doesn't have an equalizer stage? thanks.

AGM doesn't have the problem EQ is meant to address (stratifying liquid electrolyte in stationary use) but if if the voltage is tolerable (according to the battery mfg) it's a non-issue.

what do you think about eternal absortion approach?

It's meant as a workaround for controllers that move to Float prematurely. That scenario is most likely with: deep-cycled lead-chemistry batts (FLA, AGM)
periods of incomplete charging (poor insolation?)
old or injured batteries
max charging rates, as this tends to shorten Bulk and lengthen Absorption requirements


Not useful (and perhaps harmful) when: batteries are sitting on shore power or otherwise not deeply discharged regularly
charging lithium, as Li doesn't like to sit at 100% SoC
using non-deepcycle, lead batteries (box store "hybrid", marine, automotive), which are more susceptible to grid corrosion from long periods of higher voltage.

The easiest way to tell if the batts would benefit from longer Absorption is If the tail/trailing/end/finishing Amps aren't coming down to manufacturer recommendations (.5A/100Ah of capacity, for example). If the batteries are fully fed by the end of the CC's normal Absorption program then more absorption won't do anything useful for the battery. Caveat: If using PWM then running at the higher Vbatt will increase power harvest somewhat.