I would like to know the correct voltage settings on the Axpert inverter for float and absorb charging.

Also how long is it suppose to stay in absorb mode or what is the recommended setting

I have 8 x 260a/h SonX AGM batteries

Currently set to 55.2 volt float and 57.6 volt absorb

My absorb charge is set to 240 minutes

 

Thanks

The best settings depend on what the manufacturer recommends.

The common values are 0.15C for maximum charge current, where C is the battery capacity cast to amps. Axperts (in "automatic" absorb mode) stop charging at 1/5 of the maximum charge current. So that's 0.03C.

But Axperts from the factory come for free with a premature float bug, which means that they stop charging when the current falls to 1/5 of the maximum charge current setting, even if the battery voltage is up to 0.5 V below the float voltage setting. It should be the absorb voltage setting. The common workaround for this (apart from patched firmware, which is only available for a few models) is to use the absorb timer, often for 1-2 hours. This is not ideal, as sometimes it will take more than the specified time to charge the battery (e.g. a lot of clouds or loads), and sometimes it will take less, thereby overcharging the battery and risking loss of water (especially for sealed types, which are the most common form of lead acid battery).

Without looking up the specifications for your battery, they seem reasonable. It's becoming more common of late to put the really important specifications (maximum charge current and the two charge voltages) on the front of each battery module.

47 minutes ago, Coulomb said:

The best settings depend on what the manufacturer recommends.

The common values are 0.15C for maximum charge current, where C is the battery capacity cast to amps. Axperts (in "automatic" absorb mode) stop charging at 1/5 of the maximum charge current. So that's 0.03C.

But Axperts from the factory come for free with a premature float bug, which means that they stop charging when the current falls to 1/5 of the maximum charge current setting, even if the battery voltage is up to 0.5 V below the float voltage setting. It should be the absorb voltage setting. The common workaround for this (apart from patched firmware, which is only available for a few models) is to use the absorb timer, often for 1-2 hours. This is not ideal, as sometimes it will take more than the specified time to charge the battery (e.g. a lot of clouds or loads), and sometimes it will take less, thereby overcharging the battery and risking loss of water (especially for sealed types, which are the most common form of lead acid battery).

Without looking up the specifications for your battery, they seem reasonable. It's becoming more common of late to put the really important specifications (maximum charge current and the two charge voltages) on the front of each battery module.

Thanks Coulomb, 

I am no expert on these software patches and would not attempt to do this. Maybe I must put the absorb in Auto setting and the once a week do a proper absorb for a few hours.

What is your thoughts on a battery balancer? I am looking at the HA02 model. https://shop.thesunpays.co.za/collections/solar-batteries/products/battery-balancer-24v-to-48v-battery-banks

Is it worth the money?

Sorry, I've never used a battery balancer. Perhaps I should have back in the lead acid days.

3 minutes ago, Coulomb said:

Sorry, I've never used a battery balancer. Perhaps I should have back in the lead acid days.

Thanks

Hi Coulomb!

Can you explain a litle bit more this paragraph?? maybe is because my english, but i don´t understand complitelly. : When you say above ..."which means that they stop charging when the current falls to 1/5 of the maximum charge current setting, even if the battery voltage is up to 0.5 V below the float voltage setting. It should be the absorb voltage setting."..  What voltage should be the absorb one?? the one 0,5 v below the float?
Sorry. Maybe is obvious but is not clear for me.

I am having the same problem about bank not getting 100% charge in my 4 x Ultracell UCgel 200Ah/12 , and I am never seing the bulk voltage on the display of my Axpert VM III 5Kv (my max charge current is 20 Amp)-.

Thanks in advance for your help.

On 2021/07/24 at 8:03 AM, huviolan said:

When you say above ..."which means that they stop charging when the current falls to 1/5 of the maximum charge current setting, even if the battery voltage is up to 0.5 V below the float voltage setting. It should be the absorb voltage setting."..  What voltage should be the absorb one?? the one 0,5 v below the float?

When it comes to deciding whether to exit bulk charging and enter the float stage, they use the wrong threshold for battery voltage. The threshold should be 0.5 V less than the bulk/absorb setting; they use 0.5 V below the float setting. So a passing cloud could easily cause the battery voltage to fall to say 0.4 V below the float voltage setting, with the current below 1/5 of the maximum charge current setting (setting 02). This could be when the battery is only say 65% charged; if it happens for long enough, the bulk/absorb charge is terminated and the battery voltage falls to the float voltage. At this voltage, the battery could take days to get to 100% SOC, so the battery is chronically undercharged. Not every day, but most days that have some clouds.

If instead the threshold was the absorb voltage less 0.5 V, then this would not happen at 65% SOC, but could only happen at about 99% SOC or higher, which is obviously what you want. Why they can't see this error is beyond me; it's been there from the beginning.

55 minutes ago, Coulomb said:

When it comes to deciding whether to exit bulk charging and enter the float stage, they use the wrong threshold for battery voltage. The threshold should be 0.5 V less than the bulk/absorb setting; they use 0.5 V below the float setting. So a passing cloud could easily cause the battery voltage to fall to say 0.4 V below the float voltage setting, with the current below 1/5 of the maximum charge current setting (setting 02). This could be when the battery is only say 65% charged; if it happens for long enough, the bulk/absorb charge is terminated and the battery voltage falls to the float voltage. At this voltage, the battery could take days to get to 100% SOC, so the battery is chronically undercharged. Not every day, but most days that have some clouds.

If instead the threshold was the absorb voltage less 0.5 V, then this would not happen at 65% SOC, but could only happen at about 99% SOC or higher, which is obviously what you want. Why they can't see this error is beyond me; it's been there from the beginning.

Hi Coulomb,

I am thinking to install a separate Victron MPPT and only use the mains charger of the Axpert when there is no sun for a few days.

I think the Victron chargers is quite 👍

23 hours ago, Namreh said:

I am thinking to install a separate Victron MPPT and only use the mains charger of the Axpert when...

Several forum readers seem to have done this, and I have not heard of any problems with it. It's a shame to waste that hardware that you've paid for, but maybe it's a good compromise.

3 minutes ago, Coulomb said:

Several forum readers seem to have done this, and I have not heard of any problems with it. It's a shame to waste that hardware that you've paid for, but maybe it's a good compromise.

True, at least I will still be able to see the battery voltage on the APP.....🤔 including usage. I see the ICC software can link to the Victron.