Is my new battery charger defective?

[Lectron]

I am planning to build a 400W solar system. I purchased an AIMS Power charger for 12/24V ($289, Will was recommending it) and a few CHINS 12V 100AH batteries. When I charged each battery, the charger reached 13.67V and went into the float stage at this voltage. The LiFePO4 battery should be charged to 14.4V and float at this voltage, as I understand. The charger was configured for the LiFePO4.

Are my batteries undercharged? Is the charger defective or am I missing something? The seller, currentconnected.com, stated that this was normal.

Thank you.

 

[Samsonite801]

Seems about right to me:

(click on pic to zoom bigger)


Reference to doc: https://docs.google.com/spreadsheet...9Ho25ul2QzdEgoV9M35y5uj6tsk/edit#gid=52730408

Some people here even like to keep LFP float lower, like 13.40v to maintain longer life...

 

[sunshine]

When I charged each battery, the charger reached 13.67V and went into the float stage at this voltage. The LiFePO4 battery should be charged to 14.4V and float at this voltage, as I understand

There is a difference between the charger V setting and battery V reading, Just how large a difference would depend on the particular setup.
I often see that this is not clarified better in discussions to avoid confusion....charging '@' xVolts and charging 'to' x Volts!!

 

[Lectron]

Thank you, Samsonite 801 and sunshine, your comments were very helpful.

It does look like the 13.7V is a reasonable level for the float stage. But the charger's manual listed 14.4V for this level and it bothered me.

The Chins battery manual states:

Charging Limit Voltage: 14.6V​

Over Voltage Disconnect Voltage: 15V​

Over Voltage Reconnect Voltage: 14.2V​

Float Charging Voltage: 13.8V​

May I ask a stupid question? For the MPTT solar charge controller, what do these terms mean - Charging Limit Voltage , Over Voltage Disconnect Voltage, Over Voltage Reconnect Voltage? The term "over" needs clarification for me.

If the reconnect voltage is 14.2V, the battery will never (while the sun is out) see any voltage lover than this value. I am sure, I am missing something.

 

[Don B. Cilly]

the charger reached 13.67V and went into the float stage at this voltage.

[From manual] Float Charging Voltage: 13.8V

So you're worried about a 0.33V discrepancy, or...

Over Voltage Disconnect Voltage: 15V, if by any chance the battery goes 0.4V over the 14.6 limit, it disconnects. Like charging from another source...
When it gets back to <= 14.2, it reconnects. If the battery will never (while the sun is out) see any voltage lower than this value, what would be the point of charging it from another source?

Personally, I don't charge my LFP batteries to "100%". Supposedly, not doing so will increase their lifespan, and I believe it.
I pretty much never discharge them below 50% either, but that's just because I draw very little and... can afford it :·)

 

[Lectron]

Thank you, Don for your comment.

I was worried about 0.7V discrepancy: the charger was "floating" at 13.67V but it's manual specified 14.4V as the float stage!

I do not have the system assembled, just all components. I also have a bank of flooded lead acids which I keep at 13.5V. While I read a lot about this stuff and watch Will's videos I still do not have a clear 100% understanding of what is involved. Thus, thank you again.

 

[Don B. Cilly]

but it's manual specified 14.4V as the float stage!

Is it? Manual? Yeah, OK, sorry, but this apostrophe pandemic really gets me sometimes ;·)

Float Charging Voltage: 13.8V

Well, from what you wrote, it specifies 13.8... ?

 

[Lectron]

The BATTERY's manual - 13.8V, The charger's - 14.4V. But the charger held at 13.67V...

What should it be, in your opinion? In Spain and in the US?

 

[Cal]

Sounds like you have a problem. Are you sure the dip switches (1 & 2) are correctly set? Both should be in the "0" position. I would switch them back and forth a few times to see if that makes a better connection. If not the charger is defective. You can try working the dip switches with and without the battery connected. You could also try the AGM setting (14.6V bulk) to check for different results.

 

[Lectron]

Thanks, Cal.

I did try the dips and the AGM yesterday, w/o any difference. But is there a problem? The battery wants 13.8V float (per its manual) and the charger floats the battery at 13.7V. Which is 99% charged. Not bad (?).

There might be a misprint in the charger's manual where it lists 14.4V float level with dips at 0-0.

 

[Cal]

Seems like the charger is defective. You could try the charger on a lead acid battery. Does voltage go higher? Probably not.

 

[Lectron]

Cal, but if the charger brought the battery to 14.4V on the float, don't you think that it would be too high? The battery spec calls for 13.8V.

I think that 13.7V that the charger gives is not bad.

 

[Samsonite801]

Technically LFP don't need to float like other chemistries. You can do only 1-stage or 2-stage if you want...

Have a read on this doc, it has some good info:

Ref: https://www.solar-electric.com/lib/wind-sun/Relion_Charging_Instructions.pdf

"Charge Profiles:
LiFePO4 batteries can be charged with either a 1-stage profile (constant current (CC) aka Bulk Stage) or a 2-stage profile (constant current, constant voltage (CC-CV) profile aka Bulk and Absorption Stages). The 1-stage profile will charge the battery ~97% and the 2-stage profile will charge the battery 100%. The 1-stage profile is sufficient, since LiFePO4 batteries do not need to be fully charged; this will not reduce life as it does with lead-acid."


Essentially, just think of float (CV) as the max you want to charge your LiFePO4 battery to. You can turn off the charger at that point he current has leveled off on LFP because it does not need continuous float to keep them from draining like SLA and other chemistries in that ballpark.

So if 13.7v is where you want to be on the SoC chart, then just leave it.

 

[Lectron]

Thank you, Samsonite801, for the info.

I do not know how my new charger is configured to deliver charge. It goes into the float mode at 13.67V which suits me now that I reviewed the voltage curve that you supplied earlier.

I was ready to return the charger to the seller because I expected that it will float at 14.4V as given in its manual. Now I think I will keep it. Do you agree?

I have a couple of Epever Tracer-BN Series MPPT charge controllers with MT-50s. Do these charge with a 1-stage or 2-stage profile? They are still in boxes, not used.

Thank you.

 

[chrisski]

I got an AIMS 120 VAC to 24/12 VDC converterm and it was bad out of the box. Turns out they manufacture them in China; I had thought it was made in the USA. My converter sparked excessively when conected. I returned mine and am waiting for the replacement.

I do not plan on using the lithium settings, I plan on using the gel. This is a little closer to the voltage I’d Ike to see:


I understand lithium does not float, but when I opted for a really low float charge, the SCC only pushed about 30% of what was being used by the loads in the system, so the batteries were slowly dying putting me in a position where I could be low on power at sunset. If these batteries are used primarily on a solar power, I see no other way except to float the batteries so they stay charged until the sun goes down. I float my batteries a little less than my 27.6 volt absorption, but see no reason why that would not work as float also.

 

[Lectron]

Thank you, chrisski. Yes, they are from China, like my batteries, the SCCs and everything else. But I think I should be satisfied with the charger, it does not spark, it brings the battery to a comfortable 13.7V and goes into the float stage. At this point I disconnect.

I am planning to build a couple of 12V solar systems.

 

[chrisski]

Thank you, chrisski. Yes, they are from China, like my batteries, the SCCs and everything else. But I think I should be satisfied with the charger, it does not spark, it brings the battery to a comfortable 13.7V and goes into the float stage. At this point I disconnect.

I am planning to build a couple of 12V solar systems.

I’d like to see what others say, but there’s times where my SCC does exactly like you’re saying, and its fine, so I would think its not unusual from the charger, so its fine.

I’m just waiting to get my charger back. If there’s a cloudy day, I do not have anything to charge the batteries if they get low. We get 50 days of clouds a year. The last one was three days ago whenI took the RV out, but the next day was sunny.

 

[Lectron]

The charger looks very respectable. Will Prowse uses it and I trust the guy. I bought CHINs batteries and the SCCs based on his reviews. These also look decently made.

 

[Cal]

Cal, but if the charger brought the battery to 14.4V on the float, don't you think that it would be too high? The battery spec calls for 13.8V.

I think that 13.7V that the charger gives is not bad.

Don’t know why you want to hang on to a defective charger.

Your battery won’t get a full charge at 13.8V.
14.4V bulk is perfect for your battery.

 

[Lectron]

The battery will be above 99% at 13.7V. Based on the comments above, this is quite adequate and 14.4V is too high.

The battery maker listed 13.8V, I am afraid to go higher.