Is this normal? Absorption to float transition

[MarkJ]

I've just brought the van home to give its batteries a good charge and I've been looking at the VRM traces. See below...

The Multiplus was in absorption mode for about 30 mins and then switched to float. But when it left absorption mode the charge current was still around 30A. I thought that normally the transition would be when the charge current was significantly lower - for my 2 x 110Ah jobbies it might be at about 4A, I'd read. Is that not right?

The SOC value was about 90% at that time, but that might be suspect: one of the reasons for giving them a good charge is to reset it when I'm confident the batteries are fully charged.

I'm looking into this because I'm wondering if I'm not getting them charged properly. The capacity going by the voltage, rather than the SOC, is always less than I'd expect.

Thanks...

 

[wildebus]

You get this kind of random thing sometimes I found. With my MultiPlus I often turn the unit off and back on to make it revert out of Float.

 

[SquirrellCook]

I've noticed if you have a load on the battery you are charging it can go into float and still maintain the load?

 

[MarkJ]

It actually went into storage mode, according to the Multiplus.

Settled at about 13.3V and a gradually reducing current. I think that when the current has stopped reducing I'll regard the batteries as well and truly charged.
I'm not sure what the little spikes are caused by - possibly the Ablemail battery maintainer kicking in now and again? Edit: yes, I think so: the starter voltage has a little upwards tick at the same time.

 

[wildebus]

It actually went into storage mode, according to the Multiplus.View attachment 4879
Settled at about 13.3V and a gradually reducing current. I think that when the current has stopped reducing I'll regard the batteries as well and truly charged.
I'm not sure what the little spikes are caused by - possibly the Ablemail battery maintainer kicking in now and again? Edit: yes, I think so: the starter voltage has a little upwards tick at the same time.

The AMT kicks in for a few seconds and then sleeps for some more seconds (maybe 25% of the time it is on?). Your Venus will be checking every minute so if the two events co-incides, you will get the spike.

Interesting comment about the MP going into Storage (rather than Float) ... I looked at my system this morning and despite the EHU being plugged in, I was getting a draw on the battery and I think this is due to my own Multiplus being in Storage mode. I restarted the MP and it straight away went into Bulk and then Absorption.
I think sometimes the current demand might be too low to "kick start" the Multiplus into a different mode? It looks like possibly the Storage Voltage can be too low for a Lithium System as well? You can't specify the Storage Voltage, it is just set at a couple of 10ths of a voltage less than the Float setting (I have my float voltage fairly low as well).

As soon as the MP goes from Float to Storage, the current goes slightly negative. In the summertime, the solar will stop that happening, but this time of year it is not of any meaningful use.

I'll be reconfiguring the Multiplus to remove the Storage Setting so it is just the normal Bulk-Absorption-Float trio, at least over the winter

 

[MarkJ]

Thanks, interesting observation.

I tried restarting the Multiplus but it just went immediately to storage mode.

Curiously, we had some rare sunshine this morning and the MPPT sprang into life. The Multiplus gave way, as is usually the case, and basically stopped charging, but the MPPT decided it should be in Bulk mode and ramped up the voltage. However, it was only giving about 2A so it can't have been that convinced about Bulk mode.

Maybe I'm overthinking all this, but naively you'd think that both chargers from Victron would follow the same regime.

 

[wildebus]

Thanks, interesting observation.

I tried restarting the Multiplus but it just went immediately to storage mode.

Curiously, we had some rare sunshine this morning and the MPPT sprang into life. The Multiplus gave way, as is usually the case, and basically stopped charging, but the MPPT decided it should be in Bulk mode and ramped up the voltage. However, it was only giving about 2A so it can't have been that convinced about Bulk mode.

Maybe I'm overthinking all this, but naively you'd think that both chargers from Victron would follow the same regime.

With the VE.SmartNetworking over Bluetooth, there is common control of paralleled Controllers - so multiple MPPTs or Multiple IP22s now - but I don't think that feature extends to different controller types (such as Solar Charger and Mains Charger).
I am not sure if chargers with different input types should have the same sychronised regimes? On one hand, yes it makes perfect sense, but on the other you may well want to use primarily solar when available for free energy and not use grid power. Matching the modes could stop that principle working?

I don't know if a Venus OS system does it with paralleled controllers either? I have a pair of MPPTs on my Venus system but only one has panels attached so the other is off (Storm Arwen took the panels for the second controller off the shed roof and down the garden). I'll have to plug them back in and check the states of the controllers and see how they track against each other.

 

[MarkJ]

I'll be reconfiguring the Multiplus to remove the Storage Setting so it is just the normal Bulk-Absorption-Float trio, at least over the winter

I think storage mode is intended to stop you over-charging a basically full battery, as I understand it. So if you have some gear on, even if only 300-500mA, then I guess Storage ought to be not needed, as you suggest. But there again, the Victron designers seem to think you do.

I guess it's not a 100% precise science - unless you're in F1 where I imagine the batteries are monitored and controlled with unbelievable precision!

 

[PeteS]

The new Rev2 version of the IP22 with Smart Networking appears to take control of the MPPT charger and it seems to always be in the same mode as the IP22. This has been discussed on the community forum and I'm of the opinion if its connected to mains you dont need solar.
The Mains charger picks up any load and the battery just sits there. I dont have any loads greater than 15A so there is never a demand on the battery while on EHU.

 

[wildebus]

The new Rev2 version of the IP22 with Smart Networking appears to take control of the MPPT charger and it seems to always be in the same mode as the IP22. This has been discussed on the community forum and I'm of the opinion if its connected to mains you dont need solar.
The Mains charger picks up any load and the battery just sits there. I dont have any loads greater than 15A so there is never a demand on the battery while on EHU.

Oh, I don't like that. I would say that is NOT a feature you want.
It certainly would not be a setup you would want where you have a solar installation to be "green" and only want to use grid power when the Solar is not able to deliver the necessary energy

I just threw up a pair of panels back on the roof after Arwen blew them down and plugged them into the second Victron MPPT in the Motorhome ... The Multiplus is in Float, but both MPPTs are now in Bulk (due to the lowish voltage of the Battery and probably stay in Bulk for a long time due to the rubbish solar harvesting). That pattern is just what I WOULD expect from an Networked set of charging devices, managed centrally.

 

[Nabsim]

I think storage mode is intended to stop you over-charging a basically full battery, as I understand it. So if you have some gear on, even if only 300-500mA, then I guess Storage ought to be not needed, as you suggest. But there again, the Victron designers seem to think you do.

I guess it's not a 100% precise science - unless you're in F1 where I imagine the batteries are monitored and controlled with unbelievable precision!

Does it? I haven’t noticed that yet but usually I run my mains chargers when I have no or almost no solar input. I only have the two chargers and one mppt that are Victron so it won’t affect my B2B but I will see if I can check this when me get more sun.
Or, is this only when you have networking enabled?

 

[PeteS]

Oh, I don't like that. I would say that is NOT a feature you want.
It certainly would not be a setup you would want where you have a solar installation to be "green" and only want to use grid power when the Solar is not able to deliver the necessary energy

I just threw up a pair of panels back on the roof after Arwen blew them down and plugged them into the second Victron MPPT in the Motorhome ... The Multiplus is in Float, but both MPPTs are now in Bulk (due to the lowish voltage of the Battery and probably stay in Bulk for a long time due to the rubbish solar harvesting). That pattern is just what I WOULD expect from an Networked set of charging devices, managed centrally.

I dont know I guess it saves a few cycles if your parked up for a period on EHU. If I'm honest I cannot see a reason to top up with solar unless I want to be green then I'd turn the charger off.
The most useful thing is gets temperature from the network so will not charge below a settable point. It also takes voltage and current, to what end I'm not sure of.
I hope I read it wrong, there is no mention in the manual of the master slave function, in fact it doesnt mention networking at all!

 

[PeteS]

This is one of the questions https://community.victronenergy.com...mppt-syncronized-charging-how-the-storag.html

 

[wildebus]

I dont know I guess it saves a few cycles if your parked up for a period on EHU. If I'm honest I cannot see a reason to top up with solar unless I want to be green then I'd turn the charger off.
The most useful thing is gets temperature from the network so will not charge below a settable point. It also takes voltage and current, to what end I'm not sure of.
I hope I read it wrong, there is no mention in the manual of the master slave function, in fact it doesnt mention networking at all!

Ref the data side, if you have Bluetooth SmartNetworking, you have shared Voltage and Temp to all participating devices.
If you have a Venus OS system and have DVCC enabled, then you have a central Temperature, Voltage and Current data source provided to connected devices, plus more available in the system (note: a device cannot participate in SmartNetworking AND DVCC. It is one or the other).

I read that community post. Still don't agree with the principle and I still don't agree with the idea that Mains should take priority over Solar. FWIW, I always set my MPPT profile differently to mains, with a higher Charge Voltage so it will take priority when available and if not, the mains charger does the job. Use the cheapest source when possible. All automatic.
Seen nothing to tell me that is not a good way to go, but everyone does things their own way which is fine.

 

[Nabsim]

I let anything that can add charge do so, that may be mains and solar or b2b and solar. My battery’s can take full combined output of all sources and I just want to get recharged as soon as possible

 

[PeteS]

I let anything that can add charge do so, that may be mains and solar or b2b and solar. My battery’s can take full combined output of all sources and I just want to get recharged as soon as possible

Thats very valid when you want to recharge as quickly as possible. However if your on EHU for a long period using a constant voltage say 13.5v as Victron do, then this will quite happily charge a LiFePo4 battery to 100% SOC but it will take a long time, that clearly depends on how much charge current you have available.
The point I'm making and why Victron use the master slave principle is that if you maintain a battery at 13.5V it will achieve 100% SOC eventually and remain there as long as you do not exceed the max current of the mains charger. So having Solar top it up is unnecessary. (Andy in Off Grid Garage show charging at diffent voltages quite well)

Now what I cant answer is why solar will then attempt to put more in on a sunny morning, the battery is still at 100%, I do know that it goes to float very quickly providing you have an auto absorption set or no absorbtion time set. If you have a networked system then the mains charger effectively throttles back the Solar to prevent unneseccary charging but only while they are networked, switch off the mains and the solar reverts back to its own settings.

 

[wildebus]

So the battery is fully charged by EHU/Mains Charger and then charger goes to float mode ... say 13.6V. All normal.

When the solar wakes up in the morning, it sees a battery at 13.6V, it doesn't see a battery at 100%. So it will go into its Bulk charge cycle to get the voltage up to what its charge profile is set to (say 14.4V?), then Absorption, then Float. All normal again.
The same is true if you started the engine and had a B2B.
The chargers don't know the battery is at 100%, they just know the voltage it is reading. They don't even know the current it is taking, just a net current in and chargers can go into the wrong mode quite often. My Multiplus will be in float mode sometimes when it should be putting a decent charge into the battery. A BMV can jump to 100% incorrectly when certain mathemetical parameters happen to coincide.
I think sometimes there is an idea of some kind of communication going on between a battery and a charger to say "I'm charged, turn off", but there isn't really, it is all based on voltage and current mathematics.