Jump to content

Hi Guys.... and Gals!


Charlie
 Share

Recommended Posts

Good morning!

Just to introduce myself....... Charl from the Free State. I have a 5kVa Axpert running of 12 x 255W aray and 4x 230a raylights. In the process of doubling the system. All the items needed is in the store room.... now to find the time to install!!

Yesterday I replaced the battery bank to find that is was only one battery that was the coulprit bringing the whole bank to its knees. Should have checked them beforehand....... but all good because I'm doubling anyway. Took the batteries off and checked the individual voltages of each. Three measured 13.3v and the one 8.8v. What would make such a battery to decide its time to say good bye?

So will replace that one and use the bank on the new Axpert. The old bank is about 4 years old.

Link to comment
Share on other sites

Batteries develop bad cells. Either internal short between the plates or sulphation. Once it starts to go out tends to accelerate too. 5 years not too bad if the batteries worked hard, but in a ups mostly-floating application I'd expect raylites to do better. 

Link to comment
Share on other sites

2 hours ago, Charlie said:

I have set the cut off at 48v and charge at 58v would this be ok?

@Chris Hobson is the expert on these matters when it comes to the Axpert. 58V sounds good to me, but the right answer is to use what the battery manufacturer asked for.

For the low side, that depends. The inverter usually has two settings. The one is the "back to grid" voltage, the point where it switches back to the grid because the batteries are deemed low on charge. 48V is a good voltage for that. But there is also the shutdown voltage which is more of an emergency setting, where the inverter must shut down to avoid damage to the batteries. 48V is way too high for that.

Technically a lead acid battery is only empty at around 10.5V (for a 12V battery), and that's open circuit (not under load), which equates to 42V for a 48V bank. So for the shutdown voltage, you want to use something like 44V or so if you want to be conservative.

Link to comment
Share on other sites

Thanks P

I don't want to run the batteries down completely.... too expensive to replace! So I'm treating them as well as I can! So I would rather switch back to utility as soon as possible. The manufacturer works out to 58.8v but the Axpert does not have descimals.

Link to comment
Share on other sites

On 1/6/2018 at 10:56 AM, Charlie said:

So will replace that one and use the bank on the new Axpert. The old bank is about 4 years old.

The two inverters are going to have to share a battery bank. I would think twice about combining a 4 year old bank with a new bank. 

 

6 hours ago, Charlie said:

I don't want to run the batteries down completely.... too expensive to replace! So I'm treating them as well as I can! So I would rather switch back to utility as soon as possible. The manufacturer works out to 58.8v but the Axpert does not have descimals.

 Set Program 5 to USE and the you can set Program 26 to 58.4V the highest your Axpert will go. What does the manufacturer recommend for float (Program 27)?

If you plan to use your batteries lightly then program 12 49V program 13 55V. Might I suggest you invest in a BMV 702 to know the real SOC of your batteries (voltage  is a poor approximation) and Manie's ICC software which you can get here.

If you get a 702 you can hand responsibility of preventing too deep a discharge to the BMV. via a relay on the load side. If not you are caught between a rock and a hard place. The default 42V is too low but if you change it then the SOC (for what is is worth) is completely scrambled.

3 hours ago, plonkster said:

Sure, but a lead acid can pull down lower than 48v under load. Setting too low a cut-off will be a hindrance. Anyway, Chris will be able to ask the right questions with the relevant "program numbers". 

:lol: There done!

 

 

Link to comment
Share on other sites

On 1/6/2018 at 1:52 PM, plonkster said:

Batteries develop bad cells. Either internal short between the plates or sulphation. Once it starts to go out tends to accelerate too. 5 years not too bad if the batteries worked hard, but in a ups mostly-floating application I'd expect raylites to do better. 

And if left unchecked, they can explode.

Link to comment
Share on other sites

  • 4 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...