4 hours ago, ebrsa said:

Hi @Don, On the video that I posted, the  presenter recommends that for solar installations, the charged voltage on the BMV be set slightly below the absorption voltage just after recommending the normal settings. The BMV manual also recommends slightly below the float voltage.

Hi @ebrsa, you only set the "Charged Voltage" which is set slightly below the "Float Voltage" (54.0 V in your case) on the BMV. Forget about Bulk and Absorption Voltage. You only set Bulk Charge voltage on your inverter, not the BMV. Your Bulk Charge Voltage on the Inverter should be set to the maximum = 58.4 V and your Float Voltage = 54.0 V.

If you set the BMV charged voltage at 58.6 and 1% tail current as you posted above, you are telling the BMV to go to 100% once your charge current is below 1% tail current (4.5 amps) and the Charging Voltage at that stage need to be above 58.6 Volts. Then at the same time you tell it how long those parameters need to be true (held for) in minutes with the set the "detection time setting".

If your batteries are fully charged and at Float Voltage which is 54.0 Volt and your Charge Current is less than 2.5 Amps, there is now way it can go to 100%, because of the 58.6 Volt setting. It needs to satisfy both parameters.for the BMV to go to 100%. Your Charged Voltage setting need to be lower than the Actual Voltage reading at that time which should be at 54.0 V. That is why they recommend you set the Charged Voltage setting 0.3 Volt less than Charging Voltage which is your Float Voltage. Therefore the Charged Voltage setting on the BMV should be 53.7 Volts. 

4 hours ago, ebrsa said:

Yesterday I turned everything off including the BMV and then restarted. I have been having a problem that with your settings, the Axperts stop charging when the batteries reach about 96%. Turning on grid charging did not help either.

That means your batteries were fully charged, but the parameters were set to high for your batteries to come by and could not display the SOC as 100%. What was the Charge Current and Charge Voltage at that stage?

50 minutes ago, ebrsa said:

As I said before, I measured the SG of just one cell and it was at 1.265 instead of 1.277 for a fully charged battery.

@ebrsa, you cannot just measure one cell and assume the rest are the same. You will need to check all 48 cells to determine the state of your batteries and if they are in need of an equalization charge. Battery balancers can assist to direct charge to a battery or batteries that have degraded more than the rest of the batteries and "force charge" them, but it cannot remove sulfate crystals that might have built up on the plates. Only an equalization charge can do that to improve the battery capacity. 

On 4/17/2017 at 9:07 AM, ebrsa said:

charged voltage on the BMV be set slightly below the absorption voltage just after recommending the normal settings. The BMV manual also recommends slightly below the float voltage.

I suppose it depends. Do you want it to auto-sync at float voltage? In my experience, the answer is yes, you do.

For my 24V bank, I find that when fully charged they rest at just over 26V. So if the voltage is above 27V, then we can know with certainty that current is going into them: They are charging. If, at a charging voltage (anything above 27V, which is also where the balancers turn on), they accept very little current, we can conclude that the batteries are full.

If you set the voltage too high, it might fail to sync in some circumstances. For example, if I drain the batteries to 90% SoC, then the charger will switch to float relatively early tomorrow, and if the float voltage is lower than what the BMV requires to sync, it will never sync on shallow discharges. This probably not a problem though, all that causes is that it fails to sync while float-charging, and since you won't overcharge at float voltage, the only bad thing that happens is the BMV estimates the SoC lower than it really is. Which is better than the alternative.

Nevertheless, I have my "charged voltage" set to 27V (equivalent 54 for 48V), which is above the at-rest voltage, and below the float voltage. So far it works very well for me.

Also, Bulk vs Absorption voltage. I believe this is the same thing, or that is what is meant, although technically there is no such thing as "bulk" voltage. The Bulk stage is the constant-current phase (or as much as you have available), so the only regulation that happens during Bulk is to ensure that the charge current remains within safe bounds. Once you hit the required voltage, the charger changes from bulk mode to absorb mode. Then the batteries are held at the ABSORPTION VOLTAGE, while the current slowly drops off. When the current drops low enough, or after some time period passes, you switch to float, which does the same thing, but at a lower voltage.

When you report bugs to Victron, for example, it is important not to mix the two. Confuses the heck out of them.... and rightly so :-)

@Don and others who participated in the thread, today I just got fed up and erased the history on the BMV700. I set the Charged Voltage on the BMV to 58.1V as per the instructions for solar systems in the video I posted. Tail Current is set to 0.5% and detection time to 30 minutes. On the Axperts I set setting 16 to SNU (solar and grid will both charge) and grid and maximum currents to 20A on each Axpert.

It seems to make sense as explained in the video. For example assume the float voltage on the BMV is set at 54V, charged voltage is set to 58V with tail current  to 2A. Also assume the battery voltage has reached at least 54V but less than the charged voltage and at that point either a large load is turned on or cloud cover reduces the panel output to the extent that the charge current drops to below the tail current of 2A. The BMV will interpret it as 100% battery charge provided the condition lasts for the tail current detection time. Yet the batteries will be undercharged.

If my reasoning is flawed, it would be most interesting to hear the reasons. Even more interesting would be information of a battery charger that can do 64.8V, the equalisation voltage of my Trojan 105 batteries, or more of it is adjustable. A battery charger is still seems to be the least expensive solution to my problem of the Axperts being incapable of producing the equalisation voltage.

 

I have have never seen a 48v charger that would do that voltage. Suggestion is to contact Microcare in PE and chat to them. They build the mppts and so may have a charger for you. The mppts do this charge level.

Ive toured their factory and was very impressed. What see in the market is maybe 20% of their other business. They build the Vestus wind turbine controllers for example.

Regards
Mark

Sent from my SM-G800F using Tapatalk

Hi Ed

Charged voltage = Voltage when battery is charged i.e. float voltage. Think about it.  Why would the BMV want to know what voltage your absorb charge is set at? It would make sense for the BMV needing to know your float voltage so that it could interpret when to auto synchronise. Charge voltage, tail current and charged detection time are all parameters the BMV needs to auto synchronise.

 

2 hours ago, ebrsa said:

For example assume the float voltage on the BMV is set at 54V, charged voltage is set to 58V with tail current  to 2A.

There is no float voltage setting on the BMV, only a Charged Voltage setting. The Charged Voltage setting needs to be below the float voltage setting on the Inverter (54.0 V)

2 hours ago, ebrsa said:

I set the Charged Voltage on the BMV to 58.1V

The BMV will not be able to go to 100%. It will get stuck between 90-96%, even if you charge the batteries for a full 2 weeks.

2 hours ago, ebrsa said:

I set the Charged Voltage on the BMV to 58.1V as per the instructions for solar systems in the video I posted.

That is no such instruction on the video.

2 hours ago, ebrsa said:

large load is turned on or cloud cover reduces the panel output to the extent that the charge current drops to below the tail current of 2A.

For the BMV to go to 100%, there are 3 parameters that need to be met:

1.) Tail current below set value (0.5% or 2.25 amps) as per your settings. Although I think that might to be too low for Trojan's. 

2.) Your batteries are floating at 54.0 Volts as set on your Inverter. This current Battery Voltage need to EXCEED the Charged Voltage setting on the BMV of 58.1 V. If your batteries are floating at 54.0, there is no way they can exceed the Charged Voltage set at 58.1 V which you just set to 58.1 on the BMV. 

3.) The third parameter is the above values need to be true for a period of 30 minute.

Therefore, your Battery Actual Voltage (54.0) need to exceed the Charged Voltage of 58.1 V (impossible - 54.0 will never exceed 58.1) and your Tail Current need to be less than 2.5 Amps for a period of 30 minutes.

You have one parameter that will never be met (point 2 above) and therefore never go to 100% with your current settings. 

If a cloud move before the sun, yes, the tail current would could drop below 2 A, but it would drag the actual Battery Voltage below the Charge Voltage, which should be set at say 53.8 V. Once the battery voltage goes below the Charged Voltage value, there is now way the BMV can go to 100%, as all 3 parameters need to be met for the BMV to go to 100%. 

 

3 hours ago, Mark said:

I have have never seen a 48v charger that would do that voltage. 
 

Outback have a unit that can charge to 68VDC.

Victron also has the option to go quite high: Charge voltage 'equalization' Default setting: 16,2V / 32,4V / 64,8V (adjustable)

@Don  what I don't quite understand is that one would assume that charged voltage refers to absorption and not float voltage. The description in the manual is therefore somewhat confusing. Only solution would be to get advice from Victron I suppose. @Chris Hobson is the Outback charger you mentioned an MPPT charger. I have found a Ctek MXT 14 24V at Communica for about R7000 VAT included with an equalising voltage of 31.6V which is only 0.8V below the T105 voltage of 32.4V for a 24V bank. Perhaps I could equalise in banks of 24V if I disconnect from the Axperts. The specs look very good. Does anyone have experience of these chargers.

@The Terrible Triplett is the Victron you mentioned a battery charger only or an inverter/charger combination. Do you know who sells them and if there are prices quoted on the Internet.

2 minutes ago, ebrsa said:

Victron you mentioned a battery charger

You do get Victron battery chargers, they are quite expensive too.

I am talking about this, cheaper than the CTek: https://www.victronenergy.com/solar-charge-controllers/bluesolar-mppt-150-35

@ebrsa I just checked quick, maybe I missed it, but normally battery chargers do not have equalisation settings.

12 minutes ago, The Terrible Triplett said:

You do get Victron battery chargers, they are quite expensive too.

I am talking about this, cheaper than the CTek: https://www.victronenergy.com/solar-charge-controllers/bluesolar-mppt-150-35

Thanks TTT, I will investigate further. The Ctek looks like quite a smart charger though. Some time ago on advice from @Manie I spoke to Cobus van Zyl at Langebaan near me and as I recall, he had a Ctek. I guess another call to him would help.

14 hours ago, Don said:

... as all 3 parameters need to be met for the BMV to go to 100%. 

I have had BMV's for years now, 1st a 600 and now a 700, both still in use.

After Zero'ing and syncing them the first time, rest left as is, I have never seen it not get to 100% ever, unless there was insufficient sun, having used them on multiple battery banks and 3 makes of controllers.

So I have a inkling to get an idea to form a thought that maybe it is linked to the charge controllers I use, currently Victron, before that Morningstar PWM and before that Phocos MPPT 100/30 - before I allegedly let the smoke out of it.

@The Terrible Triplett have a look at www.communica.co.za for details of the Ctek MXT14. The data sheet is avalable from their website. Easiest way to find the unit is to do a search.

Equalisation would normally only be required about once or twice a year it would appear from all my research on the issue.

 

Here are my thoughts.

It is a 24v, which immediately makes me worry as I see smoke.
It is not cheap. Axpert plus CTEK you are heading for Victron country prices.
Versus a MPPT that I can connect to same panels and bank and with a change over switches, at night, I change over from one controller to another. 

Take it one step further, if it was ME, Axpert switching is done on BMV parameters right, so if it was ME, I would take a Victron MPPT and make that my charge controller. Axpert still happily continues.

Maybe the BMV issues as raised here are sorted too, we know equalising will be sorted and you won't have spikes anymore as has been discussed re. the Axpert MPPT.

(I wish that person I know of starts posting their before and after experiences between Axpert and Victron.  )

13 minutes ago, ebrsa said:

Ctek MXT14

And it is 14A max, so 140amp max battery bank if you follow solar standards. They do say 300ah bank but that is at wot, 4.5% charge rate?

http://www.communica.co.za/catalog/Details/P2238270594

Any case, as I have looked into this before, actually owned a expensive 12v charger for a while (could handle 200ah @ 12v), chargers are very expensive and must be carefully researched to ensure you get the result you want to achieve. 

2 hours ago, ebrsa said:

@Don  what I don't quite understand is that one would assume that charged voltage refers to absorption and not float voltage. The description in the manual is therefore somewhat confusing.

For me the description in the manual is clear. It states your charged voltage should be less than the float voltage. They do not mention or refer to absorption voltage anywhere. They state exactly the same in the video. 

2 hours ago, The Terrible Triplett said:

So I have a inkling to get an idea to form a thought that maybe it is linked to the charge controllers I use

The BMV goes to 100%, depending on your settings, not the charge controllers you use. If you set the Charged Voltage, Tail Current and Detection time correct, the BMV will go to 100% irrespective which charge controller you use. The BMV does not first check which charge controller you are using before deciding to go to 100%. If you use a Victron Charge controller and you set the Charged Voltage above your float voltage, you can charge the batteries for 365 days, it will not go to 100%. The same goes for the Tail Current. If your batteries are fully charged and they have 5 amps going into them and you set the tail current at 6 amps, the BMV will never be able to go to 100%, no matter how hard you slap the BMV. 

37 minutes ago, Don said:

... not the charge controllers you use.

Sorry Don, not what I meant.

I said linked to ... 

Let me expand. The controllers I mentioned are more stable with less fluctuations, even with clouds, and therefor the BMV may be able to get a more stable reading at the fyndraai level of setting the SOC at 100%, without altering anything on the BMV's bar the 2 things I mentioned.

@Don the first item you circled on the BMV manual page you posted above is "charged voltage parameter"  and then it is recommended that it should be set at the end of charge voltage which is then identified as the float voltage. In the video the example battery has an absorption voltage of 14.4V and a float of 13.4V. If you look from the 2.50 minute point it is suggested that the BMV charged voltage be set at 13.1 as per you posts but immediately afterwards the presenter says that in the case of solar systems or systems with fluctuating charge currents, the parameter should be set at 14.1V or 0.3C below the absorption voltage which is in fact, to my knowledge the end of charge voltage, as at that point chargers drop to the float voltage.

My problem is that the Axpert charging capabilities do not meet the requirements of my T105 batteries. You on the other hand do not have this problem as yours are perfectly matched. So all I am trying to do is find a solution that will give the best results before I buy some more unsuitable equipment. I have last night set the BMV charged voltage at 58.2V or 0.2V below maximum and will see what happens today.

Your previous post makes perfect sense and as long as I set my BMV parameters to achieve the maximum charge that the Axpert can manage to the batteries, even if they are not 100% charged, the BMV will show 100% charge. Perhaps I can overcome the equalisation and sulfation with a Ctek charger. @Manie referred me to @cvzyl in Langebaan, just north of Yzerfontein where I live and I had a chat with him some time ago. I will have to call him again and get information as I seem to remember that he uses a Ctek mains driven charger to recover and equalise batteries. The Ctek I found at Communica is a 24V charger but I could equalise/desulfate in blocks of 24V when the batteries are disconnected from the Axpert. I could also leave one of my two strings connected and then equalise the two 24V banks of the disconnected string and repeat for the other string.

@The Terrible Triplett recommended using a Victron MPPT charger and that may be an option as the Victron matches the requirements of the T105s. Only problem then is that I will lose all the valuable information supplied by ICC, or so it would seem.