Is anyone using the MPP Solar 12V LV PIP and not getting full charging.

I started this discussion in another thread, but decided it should have it's own discussion.

I have a new 12V LiFePo4 batter pack I built from cells and a BMS ordered from BLS batteries on aliexpress. I am charging with the 12V MPP solar LV PIP unit that has a 20A utility charger. I dont have solar set up yet.

The charger seems to shut off when the battery reaches 13.55V. I tried bypassing the BMS to see if this was the problem. I tried changing the float charge value in case this was a problem. Nothing really changed. The battery manufacturer is wondering if it is the charger.

Cells are pretty well matched. 3-4mV difference when disconnected, but show a 25mV difference when the charger is connected. Even when it doesn't appear to be charging.....

The one weird thing is that when it is plugged in it will still say "charging" right below the icon, the charge indicator light is solid which should mean the battery is fully charged.

Shouldn't a lifepo4 battery charge to over 14v? Is this fully charged indicator the charger just telling me the battery is not accepting any more current?

Sorry about the long winded question. Just not seeing things how I was expecting and still pretty new.

A lifepo4 cell can be charged up to 3.65v, but preferably lower in normal use. 13.55 volts is 3.39v per cell. That's more like the fully charged resting voltage than an end of charge voltage.

Are you measuring volts at the battery terminal or the changer terminals? Under sized wire will cause excessive drop across the wire under high current so your battery could be reading 13.55v but the voltage at the charger terminals could be 13.9 (that's a lot of drop by the way!).

I'm measuring with batgo battery monitor and balancer. When I disconnect the battery from the PIP unit or turn it off it drops to 13.4v or so. i have confirmed with an electric tester. MPP PIP unit shows a matching voltage. charge voltage in the MPP PIP is set at 14.6v per battery manufacturer specs BMS has a cut off of 14.6v for battery. I was hoping to do some capacity testing, and then would drop my charge profile down a bit.

thanks for you input

Can you measure the current passing through the battery before the charge is terminated? That'd tell you if there is a capacity problem in the battery itself.

The PIP display agrees with the voltage you see on the battery terminals? That rules out a calibration error in the PIP. The only thing I can think of is the PIP is sensing the current is going below the point where it senses charge is complete.

I can try to discharge it some and check it tomorrow. I will be getting a hall effect monitor in the next day or two that is the best meathod?

I received the response to my questions about the limited charge cycle from the Maximum solar Ebay seller that I bought it from. It still doesnt make 100% sense to me.

"Yes, there's a reason for that. Typically inverters should not subject battery to excessive bulk charge so in a charging cycle, it's designed in a way that if the battery was not below 12.5v (based on 12v) then it won't get “bulk" charged. It'll only go up to float level and stay there. To bring a battery to bulk charge please discharge battery to below 12.5v and it should happen. "

I responded that I had changed the float to a higher Voltage. havent heard back.

Is this a MPP Solar unit?
If it is I was wondering if you had to pay about 120.00 in shipping to get it here?

gnubie said:

Can you measure the current passing through the battery before the charge is terminated? That'd tell you if there is a capacity problem in the battery itself.

The PIP display agrees with the voltage you see on the battery terminals? That rules out a calibration error in the PIP. The only thing I can think of is the PIP is sensing the current is going below the point where it senses charge is complete.

Click to expand...

Well, I hooked up a hall capacity monitor and ran the batter down to 10.4V . I got 2400 kWh which is a 200 Ah battery, so even if it doesn't charge to over 14V I guess it's no biggy.

The only weird thing is that the reported load on PIP was lower than my monitor on the small A/C I was using to draw down the battery.

Reported WH used by AC was about 10% less than the draw on the battery which makes sense given normal inverter inefficiency, but any time I checked all three sources for current draw the PIP showed a lower draw than the other sources that I couldnt explain.

I’m experiencing the same symptoms. 13.5v max at the PIP display and volt meter at PIP / battery connection. My Battery Go BG-8s says 13.2v. Battery is Lifepo4 12v Sinopoly. Now 13.5v is 99% charged so?

If you read above the distributor told me this is a safety feature in the MPP. Since I am still getting full capacity and it is better to not fully charge anyway I am just going to leave it.

I agree it’s good for battery life to leave a lifepo4 under a full charge, but you lose any top balance. When charging lifepo4 using a PIP you never get to 3.6v per cell. If the PIP won’t let the cells go that high using a PIP charger makes a BMS useless as it only kicks in to top balance at 3.6v. I use a Battery Protect to stop an over discharge, so I may as well disconnect my BMS.

Yep. I realized the same thing

How do you NOT charge to full? Is there some setting that I have to change to tell my MPP to stop charging at 90%? Is that what BMS ACTUALLY does is charge and discharge between the high and low thresholds that you set in the controller?

Dave1 said:

I can try to discharge it some and check it tomorrow. I will be getting a hall effect monitor in the next day or two that is the best meathod?

I received the response to my questions about the limited charge cycle from the Maximum solar Ebay seller that I bought it from. It still doesnt make 100% sense to me.

"Yes, there's a reason for that. Typically inverters should not subject battery to excessive bulk charge so in a charging cycle, it's designed in a way that if the battery was not below 12.5v (based on 12v) then it won't get “bulk" charged. It'll only go up to float level and stay there. To bring a battery to bulk charge please discharge battery to below 12.5v and it should happen. "

I responded that I had changed the float to a higher Voltage. havent heard back.

Click to expand...

I’m seeing my pip-812 is doing the very same as yours and that’s with PV power only ac In is not connected.
Stops at 13.55V at the battery. I know it’s good. For longevity and charge cycle increases but shouldn’t you be able to have the option to charge to full if you choose? I looked thru the manual and found nothing pertaining to setting for doing that. Am I missing something? Also the fan continues to run and drawing power maybe from the PV or the battery. And I’m showing 7amps still being supplied thru the battery cable with a clamp meter but the battery BMS must be blocking any further charging for some reason. My EPever 4215bn always charged to 14.4 before the battery or CC tapered the charge to 0 charge. Strange stuff.

at battery.

I just spoke with Ian of USAShipmpp
Concerning the 13.55v charge and he said at setting #27 you could raise the float voltage up to where you want but after charging it would float charge also at that higher voltage. So raising it up over 14v it might not be wise. I think that wouldn’t be healthy for an expensive LiFePo battery. I’m leaving at 13.6 which is 100% resting voltage. I don’t know if raising float to charge to 14.4v then resetting float to 13.6 on occasion would be beneficial or not?
Any input on that from anyone?

I think I’m going to buy a second Aili battery monitor to use with the all in one.
Good to see what is actually going on at all times.

@MrNatural22 I was reading the manual JUST today about that parameter after seeing my charge stop at 13.5. That is apparently the default, so to the OP, to say it is not charging all the way is actually incorrect. It is charging up to where you told it to by leaving that parameter at default.

I select “user” defined for battery and then am still trying to set the right voltages for bulk and float by trial and error until I get a normal, conservative fully charged voltage of 25.6v (what Renology recommends) on my 24v AGM battery bank. I’m still playing with it, but charging to 26v with the PIP connected and <100watt load seems to get close to 25.6v in a rested battery disconnected from the PIP. You know your actually changing the charge settings in “user” mode when the changes to bulk and float in the Watchman software no longer say “false”. I had to play with bulk, float, and battery cut off voltages to get it to say, “change successful”. Even with my solar switched off, utility only charging, little to no load, it won’t fully charge my bank properly in “AGM” mode.

MrNatural22 said:

I just spoke with Ian of USAShipmpp
Concerning the 13.55v charge and he said at setting #27 you could raise the float voltage up to where you want but after charging it would float charge also at that higher voltage. So raising it up over 14v it might not be wise. I think that wouldn’t be healthy for an expensive LiFePo battery. I’m leaving at 13.6 which is 100% resting voltage. I don’t know if raising float to charge to 14.4v then resetting float to 13.6 on occasion would be beneficial or not?
Any input on that from anyone?

Click to expand...

I tried that too as a test. I agree it would not be wise as a long term setting. It didn't seem to change anything. I don tthink it is a big deal. I got the full capacity from my battery.

I have been working on this same issue with my Pip Lv2424. I never witnessed my SCC bulk charging automatically. However, I found that if I switched the PV breaker to off, waited a minute, then flipped the breaker back on, the SCC would begin a bulk charge cycle.

I've been reading extensively on where to set a float voltage for Lifepo4. I see recommendations ranging from 26.4 all the way to 27.2. I see Battleborn mentioning that anything under 27.2 is fine. Then on another site, I found where almost no charging happens below 27.2 and that is why Battleborn recommends a float below that level. Does charging happen below 27.2 volts? If not, then should I force a bulk charge cycle occasionally? I see a problem because if my battery has not gone through a bulk cycle, and no charging occurs below 27.2 volts, then I could have a full day of sun and not have a well charged battery by nightfall. Then through the night my inverter could shut down due to low voltage and be forced to run the generator after a sunny day. As a side note: I'm still wating on my BMS that I ordered in January. When that arrives, I should have Coloumbe meter and be able to know my actual SOC more accurately.

I got 400w of solar installed on the roof and am a little perplexed by the numbers going into the battery. They are connected 2S2P using 10ga wire

The voltage and amps make sense, but the reported watts in doesn't add up. Thoughts.

36Vx9A should equal 324W (which does seem high given where the sun is, but that is what is measured and what my multimeter confirms.

So why am I only getting 140W?