I’m not so much a newbie for Solar as we’ve been off-grid for 12 years and replaced SLA twice. However, we’ve now bought two Eco-Worthy LiFePo4 280Ah batteries to replace the SLA, which are very much on the way out. They are popular in this part of the world and have decent reviews here. Lots of people seem to have simply swapped them in. We have 4* 250w panels through the Victron 100/50 charger. I know this has a Lithium setting so will use this when swapping out the batteries.
The info sheet with the batteries (both came today, both are 13.2v) says the standard charge/discharge is 140A. So I’m now a little confused. Will the Lithium setting be too little to charge them? I have never needed to play with the charger settings, do I need to? How?
The idea is that we swap these in and, probably, never need new batteries again before we leave this mortal coil.
I’ve now swapped out the old batteries . The rotary dial is not particularly clear but if it was set to the default ‘3’ then I’m sure it’s now at ‘7’.
Overnight the battery V has dropped only 0.1v (inverter only on, which uses 0.8A, thereabouts). It’s been light for 90 minutes and the SLA batteries would have shown an increase in V by now. The LiFePo4 haven’t yet. Sun will hit the panels properly around 10am and stay full until 5-5:30pm. We vary between a minimum of 5hrs in Dec to 14hrs in midsummer. We take very little power (LED lights, a 40w fridge, router for internet) and the freezer is outside the cave on a separate system, AGM battery, to further reduce draw.
Do the new batteries charge (and discharge) more slowly?
We have 4 250w panels, 2s to parallel. With efficiency loss we’ll probably get about 680-720w at peak. I can’t remember the exact ‘A’ but I think it’s about 38-40 how the panels are wired (they go crazy high in the winter if all in series).
They should charge no slower than AGM. St the start of the day the solar limits so they may not be much different, they may charge faster as the solar increases and will maintain higher charge as they fill up.
They reached 26.9 about 10:45 and have stayed there. It’s now 18:15 with bright sunlight, though not on the panels. They are just beginning to flutter to 26.8. According to their data sheet this is 90% of charge. I’ve read they maintain charge for much longer than ‘normal’ batteries so if they return to 26.4 by 23:00 and this is repeated most days, I think I’m going to be happy with their performance. We have a timer on the inverter so that when we are in bed, asleep, the power to the house shuts off at 23:00 until 8am. If we need power during the wee hours, a touch of the button and it’s instant. Obviously as we count down to shorter nights I’d expect lower highs (and lower lows), but OK the first day.
Going to be an an interesting journey. And thank you for not being a ‘data show off’ haha. I’ve given up on many sites/forums because of graphs, formulae and tech-speak. Simple questions is all I have. Simple answers should suffice.
OK, good news. The other difference I should have mentioned is that the voltage rise when charging is much smaller with lithium. With SLA the voltage might rise quickly to 28+V while. With lithium they only climb to 28+V at the very end of charge and will do lots of charging below this voltage so what you are seeing is OK.
Here is a generic graph showing how the two types are different because sometimes a graph can be useful
An update. Yesterday we had a grey day until 5pm-ish and the batteries managed 27.1, dropping to 26.8 overnight (at 8am). Today, sun all day. We have had the fridge on all day, plus the TV for the F1, so this seems high. The charge controller has got to the absorption stage. An hour ago they were 27.6, now 28.2. The inverter (I think; I don’t know if the batteries have an audible alarm) has beeped twice. Is this ok? Overvoltage, perhaps?
Your batteries and charging are behaving fine, per the graph they only really increase in voltage when they get full.
Regarding the beeping, not enough info to go on. Some batteries will shut off the charging when they are full and give a warning but I do not know Eco-Worthy. The charge shut off may momentarily drop voltage and then switch the batteries to discharge. You would have to check battery and inverter manuals and any voltage history.
Ok, thanks (btw, is your profile pic the bridge over the canal between Saltaire/Eldwick? Looks very similar and I lived there when in the UK).
The only audible alarm from the inverter is for low voltage, so I don’t really know what it was. We’ve had two more since. I think I will invest in the Victron Control and cable so I can see more information.
It looks exactly the same. You walk on the right but have to cross over, walking behind a small mill, to continue on the left. A bridge further and there’s a mooring behind a fabulous pub, in Eldwick. Many happy hours walking my whippet there.
Anyway.
Another couple of beeps. I wonder if the BMS is shutting down the batteries for a moment or two to stop overcharging, which would cut power for a second to the inverter? We are now down to 27 and the last was as I replied earlier. I guess I’ll be a touch nervous and hyper-aware until I’m used to their foibles.
Hi. Sorry to keep bothering you. This morning voltage climbed to 28.2 by 11:30 and the controller showed float. Power draw is the fridge and the router. One odd thing just before I went out the door. I put milk away in the fridge and the controller flashed the Bill and Absorption lights, three or four times I think, the voltage on the inverter dropped to 26.7, then began to climb again. It steadied back at 28.1/28.2.
We have come back and the batteries are now at 26.6, still the controller shows float.
I’ve looked at the error codes on the controller. It says either Configuration or Internal error. Looking further that’s either a mismatch between what the Bv is and what the controller thinks, or the controller is cooked. Pv in is showing at 62v, didn’t check current, and the multimeter shows the inverter reading and the Bv cables from the controller to be accurate.
Should I remove and reseat the cables from Pv Array and batteries to reset the controller to check whether the error is in that?
I have just realised that you have put 2 12V batteries in series for 24V, with lithium it is always best to have a 24V battery under control of a single BMS.
Did you fully charge the 2 batteries individually before connecting them.in series to make sure that they were balanced with each other to the exact same charge. Do you have bluetooth on your batteries to check the single battery voltages and SOC on both. What can happen when charging 2 12V batteries in series that do not communicate together if they are not perfectly balanced is that one battery ends up getting to 100% first and spiking up in voltage and shutting down which causes troubles. Perhaps you are seeing this.
When the batteries arrived I checked with my multimeter and they were both at 13.21v.
I have a Victron Controller arriving tomorrow or Wednesday which will make it easier to see what’s happening. The battery manual says that this issue might be that the Solar charge controller doesn’t have an ‘activation’ function.
I shall remove all the cables from the Victron this evening, which will do a reset, as it is entirely possible one of the cables to it has loosened or moved while we were changing over. I’ll also check that the rotary dial is at ‘7’, though it seems to be (the markings on it for the supposed arrow are not particularly clear). I shall also remove the -ve cable from the battery and check the voltage of each. I shall then reconnect everything and see what happens tomorrow.
I have also contacted the battery manufacturer in case they think the BMS might have become damaged, by the courier, in transit. I don’t know how robust the electronics are with them.
Have a look at the voltage graph I posted, the voltage is very flat in the middle of the curve and SOC varies a lot for small variations in Voltage, 13.2V is about 50% charged. You need to confirm they are the same voltage when full as voltage varies rapidly for small changes in SOC.
The Victron battery manual states
If a battery bank will consist of batteries connected in series to make a higher voltage bank, then each battery must be charged individually first.
When the batteries get close to 28V, measure the voltage of both batteries individually and see if they are the same. Charging them singly to full would still be a good idea.
Ok. I have a battery charger that can charge at 12/24v, 8 or 16A that I can hook up to our generator, which I have wired to power the house. That way we’d have power inside while charging them. Do you think this will be ok to use? I’d disconnect the short cable making them a series, then I can use the crocodile clamps separately on each. How will I know maximum charge is reached (will the BMS shut down charging?).
Alternately, though I know each battery has its own BMS, will a specific BMS (from Victron for e.g.) between controller and batteries be feasible?
Finally…what is your charge out rate? Haha. I feel I need to acknowledge your help.
Does your charger have a proper float function and lithium charging settings bevause ideally you rely on the charger taking them to 14.2V to 14.4V and then going to float so if you use the same charger you should get the same result. If the charger is dumb then you would have to keep an eye on it and stop charging when you get to 14.4V. The trouble is, as you have seen the voltage rises only at the end and quite quickly. The BMS will shut charging down at something like 14.6V as a final safety.
. The rotary dial is not particularly clear but if it was set to the default ‘3’ then I’m sure it’s now at ‘7’.
