MPPT boost - 24vdc to 48v battery bank

[Psyfy]

Hi everyone,

Been hovering as a guest for several months. Now I am this close (>>.<<) to purchasing both a Classic 150 and Classic Lite 150.

Recently I installed a 48v 1000Ah VRLA (AGM) batterybank made up of 2v cells to replace the existing failing 24vdc batteries.

My question is this... the existing 24v setup outputs 3000watts (120amps cont.). In the meantime until the panels are reconfigured for the new 48vdc system and another 3000watts of panels and a Classic Lite are added, can I just plug the 24vdc into the Classic 150 and boost the output to charge the 48v battery bank? The bank desperately needs a charge/float (current avg. of 2.08v per cell).

So I read that the Classics support BOOST mode but it's still not clear to me if I can do this and at what efficiency?


Thanks in advance.

[Psyfy]

Okay, this is an excerpt from what I found in an online .PDF by Robin Gudgel created circa 2007 ->>

-----------------------------------------------------------------------------------------------------------
Classic MPPT product overview 
(Development status update)

12. Boost or Buck: MPPT controllers take a high voltage and buck it down to the battery
voltage. What if you want to go the other direction and charge a 24 volt battery from a 12
volt battery? No problem. The Classic can be configured as a boost converter too. This
feature is not found on any present day charge controller. 
-----------------------------------------------------------------------------------------------------------

http://www.midnitesolar.com/pdfs/classicDevUpdate3.pdf


It's great news to find this info as it's exactly what I need for my application!!!
However, before I go off and order two 150's, perhaps one of the Midnite Solar devs would be so kind as to confirm the feature in the Classic 150 and tell me where I can find the specs regarding the boost efficiency & maximum current when stepping-up a nominal 24vdc supply to charge a 48volt AGM battery bank?


Thanks again.

[TomW]

I am pretty sure one of those guys will get in here to answer your question. They usually respond very quickly to this type information request. The probably just haven't been on the forum since your first post on it. I will poke Ryan and see if he can help.

Personally, I do not know.

Good luck with it.

Tom

[Halfcrazy]

At this time the Classic is really a Buck only controller, while the hardware can boost there is no software to support that just yet.

Ryan

[Psyfy]

Hi, that's a real downer. <slowly puts wallet back in pocket for the moment>.

Anyone else have any ideas on how to get around the issue until I can sort it out properly in June? Trying to avoid a 5kva 48vdc battery charger, fuel noise etc. when I have nice quiet PV's idling away up there.

Please tell me someone in the know... Is there actually a charge controller out there that will do the job? I've only drawn blanks so far.


Thanks again.

[stephendv]

My question is this... the existing 24v setup outputs 3000watts (120amps cont.). In the meantime until the panels are reconfigured for the new 48vdc system and another 3000watts of panels and a Classic Lite are added, can I just plug the 24vdc into the Classic 150 and boost the output to charge the 48v battery bank?

It sounds like all that's required is just to reconfigure your panels.  Something you need to do anyway and once the panels are reconfigured and if you have a classic, then you can connect it to the 24v battery and it'll work fine.  Then you can disconnect it from the 24v bank and connect it to the 48v bank and it'll auto detect battery voltage and charge that bank.   Simples 

[Psyfy]

It sounds like all that's required is just to reconfigure your panels.  Something you need to do anyway and once the panels are reconfigured and if you have a classic, then you can connect it to the 24v battery and it'll work fine.  Then you can disconnect it from the 24v bank and connect it to the 48v bank and it'll auto detect battery voltage and charge that bank.   Simples 

Thanks Steve, however things are never that simple. The roof (and therefore the panels) all come off in summer as another level is going up. Then the both old 3kw and the new 3kw arrays go up.

Just wanted to avoid doubling handling and unnecessary costs. Will think about it.

[Psyfy]

At this time the Classic is really a Buck only controller, while the hardware can boost there is no software to support that just yet.

Ryan

Software? I don't get it, you're almost there! 2007 and 2010 are long gone in the tech field and vaporware just isn't cool. Outsource it!
Boost is a killer function, this is your goose.  Don't drop the ball.

Best.

[niel]

if the battery bank is not in use i'm sure you would probably be able to charge it up 1/2 at a time.

as to the pvs, you aren't going to get around the rewire, but it isn't as complicated as you make it sound.

[dgd]

if the battery bank is not in use i'm sure you would probably be able to charge it up 1/2 at a time.

as to the pvs, you aren't going to get around the rewire, but it isn't as complicated as you make it sound.

..or just rewire the batteries temporarily as a 24 volt bank

dgd

[boB]

Yeah, this still may happen but it is just not high on the list.  There are too many more important things to do at the present time and not enough resources (engineers) to get it all done.

I thought that  solarconverters.com   made what you want but I just looked and theirs is 12V to 24V.  There are other companies out there that must do this if you can't wait.  I just don't know where right off the top.


boB

[Photowhit]

I'm with DGD, just reconfigure your battery bank for the time being, likely they haven't been discharged much, AGM's hold a charge particularly well, so in the short term you won't need too heavy a wire since you CC will realise they are in the top 5% and reduce the current.

[Psyfy]

Alright, you've all been really helpful. I'll take a look at things over the weekend and get back to the forum.

Regards to all.

[dgd]

At this time the Classic is really a Buck only controller, while the hardware can boost there is no software to support that just yet.

Ryan

Software? I don't get it, you're almost there! 2007 and 2010 are long gone in the tech field and vaporware just isn't cool. Outsource it!
Boost is a killer function, this is your goose.  Don't drop the ball.

Best.

love the mixed metaphors    ...but couldn't agree more, the h/w is excellent, the s/w is woefully behind, outsource or better still make it open source

dgd

[Psyfy]

love the mixed metaphors    ...but couldn't agree more, the h/w is excellent, the s/w is woefully behind, outsource or better still make it open source

dgd

Yep, looks like the kinda device that should be running Ubuntu! haha