Adding my two cents onto what Plonkster said, in my experiences over the years farting around, charge controllers should be separate.

I changed battery types, needed more batteries and therefor more panels, until I settled down.

Each time I made a move the charge controller could not handle, I simply bought a new better one and sold (or gave) the previous one to a newbie who wanted to start out, as I was helped originally. Passing it on. (Maybe we must put up a section for 2nd hand stuff.)

 

The higher end controllers are quite versatile nowadays.

 

I have lost 2 controllers over time. I believe it was due to them working all day long at full power, for over 2 years. One was nogal a MPPT. I just replaced the controllers the following day with another brand.

 

Panels + Controller + Batteries = one unit, for they are intricately interconnected.

Then the inverter. Especially the ones you can daisy chain if you need more power as your needs expand.

 

The 3 setbacks in doing it this way, a) it can be more expensive initially (but you have so many more options), b ) it is not one device, so a wee bit more wire and c) to get software that combines it all for you in one place, is a big challenge. 

Thanks for your replays guys. Your explanations helped me to understand the charging process better.

Happy New Year to all

Thanks Plonkster for your detailed reply.  I am no battery expert and could not have explained it better either.  In the installation I did with the Trojans, they should have enough time to charge in-between "load-sheddings" - they are not cycled daily, but as per your explanation the Axpert - Trojan combination might not be ideal when cycled daily.

I'll jump in so long, but I'm sure Superdiy will also answer. The Trojan's absorption voltage is 14.8 (for a 12V bank) instead of the usual 14.5 or so that is common for lead acids. This means for a 24V bank, you need to take them up to 29.6V for proper absorption. To make it even worse, you need to take them to 31V for equalisation, and the axpert will turn off if you do that! Thankfully you don't have to do that often.

 

So this means the Axpert cannot properly charge a Trojan bank. This might not be a complete deal breaker, but it is an obstacle. If I am wrong, I hope the others will correct me, but as I understand it, at the end of the absorption phase the battery will be at 85% SoC more or less. Chargers will usually switch to "float" at this point, which is normally 27.6V for a 24V bank. 27.6V is however still a "gassing voltage", it is higher than the sit-open-circuit voltage of the battery, and will still force current through the battery in "the wrong direction" causing it to absorb more energy, so you will eventually get them all the way to 100%.

 

(Ie, contrary to popular belief, the batteries aren't "full" when the charger switched to float...)

 

Now if you're absorption voltage is too low, your charger is going to switch to float at a lower SoC. You might still be able to fully charge them, but it's going to take a lot longer to get there. So this might not be a complete deal breaker if you use it as a UPS, but it sort of is if you cycle it daily.

 

At least, that's how I understand it.

 

There is another thread here about calibrating these inverters. It might be possible to adjust them with a deliberate error of 0.4V... but I don't know if the originator of that thread had much luck with that idea.

Edit: To answer your question, unless you spend enough time floating it all the way to 100%, then yes, it won't have the full 225Ah capacity, and sulphation will begin to set in and reduce the life of the batteries.

 

 

Thanks Plonkster for your detailed reply.  I am no battery expert and could not have explained it better either.  In the installation I did with the Trojans, they should have enough time to charge in-between "load-sheddings" - they are not cycled daily, but as per your explanation the Axpert - Trojan combination might not be ideal when cycled daily.

Just to add to this I just need TTT to confirm this also

The T105RE's batteries have different absorb and float voltages than the normal T105's

Absorb: 2.35-2.45 per cell

Float: 2.2

This fits in with the limits of the Axpert even at 2.35 x 24 = 56.4V or 2.45 x 24 =58.8V

I presume it's safe to use  any value between those 2

 

So for the Axpert using the T105RE's is the better option, unfortunately  the equalize charge is still too high even for the RE 2.58 x 24 = 61.92V

 

Thys

SuperDIY, I am of a different opinion.

 

Trojans need to be cycled ... or get cheaper batts if you are only in UPS mode. 

 

I run my batts up and down the whole day / month, they never get to float stage ever.

One day every +-28 days, I equalize them for that 1 day, the whole day. 

 

My controller has the feature built in to equalize every 28 days automatic, or manual by user.

Most, if not all, of the off-grid guys do that, the ones who live where they are no utilities power, for they never get a full charge charging and using at the same time.

Thys, you are correct.

 

http://www.trojanbattery.com/pdf/datasheets/T105RE_TrojanRE_Data_Sheets.pdf

 

Mine is set as follows (24v system):

Absorb: 29.2v - This is the norm for my setup. Inverter draws all the time, controller adjust input as needed. 

Float: 26.8v - I have never seen this float level under normal operations since I got the batts. 

Equalize: 30.6v - once a month.

 

Each time I check the batts with the hydrometer, all the cells are at the bottom of the green @ 1.30. 

And I do top up regularly, like in once every 6 weeks.

To all you whom like the Trojan batteries.

 

Best to make that a priority before the next batch arrives at the new prices.

 

I would guess as in the next few days to confirm price and stock. At least then you can plan.

 

The Rand/dollar is going to make it very interesting.

 

Ta.