I have a puzzle for YOU

[WorldwideDave]

Summary: One battery. No solar panels connected. No inverter. One fuse panel. Two DC loads. One load works the other does not. Both loads are charging cables for solar generators. Need some suggestions on why this might be.

Thanks for reading.

Long version:
No solar connected right now.
I have a 200 AH LiFePO4 battery.
It is fused and connected to a Blue Sea fuse panel, recommended by Will P himself.
I have 2 loads coming off the fuse panel.
One goes to a cigarette lighter socket (female)
The other goes to an SAE connector.

In the SAE connector I plug in another SAE connector that has a wire which goes to a 7mm barrel-type connector. I then connect this to a different solar generator (225Ah) to charge it. All day long the SAE connector charges the solar generator just fine. I know this because of the discharge meter on my shunt, and the DC Watts In on the solar generator both match at about 50 watts. The amp rating on the solar generator will not permit more amps than this to flow in from a 12v source. All good. I get it. When I use solar panels plugged into the solar generator directly, they run at a higher voltage, and I get more wattage to charge with. Brilliant. No problem.

In the cigarette lighter socket (female), I plug in a cigarette lighter plug (male) that has a cable attached. At the male end there is a red light to indicate good fuse. At the end of the cable is a 5mm barrel-type connector. I then connect this to a solar generator (small 150Ah) to charge it. Earlier today it was charging the solar generator. I know this because the discharge rate on my shunt, and the screen of the solar generator also indicates around 30 watts were coming into the solar generator. However, now I am seeing something unique. It seems that while the solar generator is flashing that it is charging, I see zero watts coming into it on its screen, and zero watts being discharged.

If I connect both generators at the same time, I can see that one generator (the one connected to SAE) keeps on charging but the other solar generator does not charge.

If I then I connect the solar generator (smaller one) that is not charging to the SAE cable with an adapter to go from 7mm to 5mm, the solar generator also does not charge.

I do not have an adapter to go from the small 5mm up to the 7mm so I cannot test charging the bigger Solar Generator with the cigarette lighter cord. However, there is a fuse in the cigarette lighter male part, and if you remove the fuse or if it has a bad fuse the red light on the case will not light up.

I don't know if I have a bad solar generator, or if there is just not enough watts coming out of the fuse panel, or if the 200AH battery BMS is in some funky only send 50 watts mode or what. Battery is currently low at 11.75 volts according to the shunt, and the solar charge controller reports 11.75 volts as well. However this is with load (shunt reporting 60 watts going through it right now to charge the other solar generator).

I know I can disconnect my load, wait 2 hours, then see voltage and compare it to my battery manufacturers chart. Right now it would report zero percentage on state of charge, but not accurate with the load.

I guess I can get a reading of SoC tomorrow morning. I can also try hooking up solar panel directly to smaller 150Ah solar generator to see if it wakes up with more voltage, amps, and watts in the sun tomorrow.

It may be that the voltage requirements are higher for the smaller solar generator. Although it lights up like it is charging and flashes, it shows zero watts, so its internal charge controller might be at play here. DC Input on the side of the small solar generators it reads 15v at 2.4 amps (that is 36 watts max). Maybe at 11.75 volts it just says no thank you.

 

[wpns]

It may be that the voltage requirements are higher for the smaller solar generator. Although it lights up like it is charging and flashes, it shows zero watts, so its internal charge controller might be at play here. DC Input on the side of the small solar generators it reads 15v at 2.4 amps (that is 36 watts max). Maybe at 11.75 volts it just says no thank you.

That feels like the answer. Try fully charging your LFP battery and see if the smaller battery pack will charge.

 

[WorldwideDave]

Or I could keep draining the battery while the larger solar generator is still connected to it and see if the BMS shuts off the ability to discharge the battery?
Charging it all back up via the sun only would take me 4 days my guess at 300 watt panels max.

 

[time2roll]

Get the battery above 14.2 volts and see what goes.

 

[WorldwideDave]

Well, get this... in past 2 hours, the voltage dropped so low I guess the BMS shut off the battery. The meters on the shunt are not reading anything. The charge controller has also shut off. So I will charge it via my 200 watt panel tomorrow and see. My 100 watt panel is in use. I could also connect a trickle charger. I am in the market for an appropriate AC to DC charger as well...trickle charger is like .8 amps or about 11 watts, so 200 watt panels = better I think. But at least I was able to see how low it would go before it died. I will disconnect the loads and see if it wakes up tomorrow morning on its own.

 

[WorldwideDave]

In the morning I put my solar panels on my roof and plugged them into the solar charge controller. The battery woke right up. It has been charging most of the day. It has increased by 773 watt hours on the charge side of the shunt with a 200 watt panel connected doing about 80-110 watts throughout the day.

In fact, if I know that I connected the panels at 9 AM and it is now 6 PM, that's 9 hours of charging for 773 watt hours. Thats about 85 watt hours per hour from a 200 watt panel. Is that any good? I honestly don't know, but it doesn't seem good.

Also, if my battery is 2560 Watt Hours, and I'm getting 85 watt hours per hour, the best I can do is 30 hours to charge a 2560 Watt hour battery. Is my math right? Given that it will likely be in the sun charging for 10 hours a day max, safe to assume it will take 3 days to recharge with my single 200 watt panel? Maths can be hard.

In other news, because I took photos of the shunt meters every morning at the same time, I have some stats to share:

On April 2, I disconnected the panels and brought it inside with a full battery. I used it for 6 days before the BMS shut off the battery. Used 2579 watts before it died. Rated at 2560, so probably accurate/healthy battery. It does not have a BMS that i can access with bluetooth, and I don't trust the solar charge controller or the shunt to provide state of charge 'facts'.

I do not plan on connecting any load except the USB camera I have connected for 3 days just to see if it charges up on its own happily and i get the 'ful' on the solar charge controller again. Is this all good testing?

 

[Supervstech]

In the morning I put my solar panels on my roof and plugged them into the solar charge controller. The battery woke right up. It has been charging most of the day. It has increased by 773 watt hours on the charge side of the shunt with a 200 watt panel connected doing about 80-110 watts throughout the day.

In fact, if I know that I connected the panels at 9 AM and it is now 6 PM, that's 9 hours of charging for 773 watt hours. Thats about 85 watt hours per hour from a 200 watt panel. Is that any good? I honestly don't know, but it doesn't seem good.

Also, if my battery is 2560 Watt Hours, and I'm getting 85 watt hours per hour, the best I can do is 30 hours to charge a 2560 Watt hour battery. Is my math right? Given that it will likely be in the sun charging for 10 hours a day max, safe to assume it will take 3 days to recharge with my single 200 watt panel? Maths can be hard.

In other news, because I took photos of the shunt meters every morning at the same time, I have some stats to share:

On April 2, I disconnected the panels and brought it inside with a full battery. I used it for 6 days before the BMS shut off the battery. Used 2579 watts before it died. Rated at 2560, so probably accurate/healthy battery. It does not have a BMS, and I don't trust the solar charge controller or the shunt to provide state of charge 'facts'.

I do not plan on connecting any load except the USB camera I have connected for 3 days just to see if it charges up on its own happily and i get the 'ful' on the solar charge controller again. Is this all good testing?

Um… why does it not have a BMS?

 

[WorldwideDave]

Um… why does it not have a BMS?

Oops - corrected. I don't have BMS that I can connect to with Bluetooth to see what it reports. That's what I meant. Thanks. MCSE computer certification? We are getting old my friend.

 

[Supervstech]

Oops - corrected. I don't have BMS that I can connect to with Bluetooth to see what it reports. That's what I meant. Thanks. MCSE computer certification? We are getting old my friend.

How about my NCE… netware 3 certified baby!

 

[WorldwideDave]

Insert token ring joke here

 

[Supervstech]

Insert token ring joke here

Omg, so much token ring!… my flashbacks are flashing…

 

[wpns]

In fact, if I know that I connected the panels at 9 AM and it is now 6 PM, that's 9 hours of charging for 773 watt hours. Thats about 85 watt hours per hour from a 200 watt panel. Is that any good? I honestly don't know, but it doesn't seem good.

That’s 3.9 peak solar hours for that day. Not sure where you are or your roof geometry or how reasonable that is, but it’s not a crazy number.

And yeah, another 3-4 days (all other things being equal, not that they ever are) should fully charge your battery. And your load test shows it’s about the capacity it should be.

Btw: it’s probably not the best idea to use the BMS for charge/discharge control…

 

[WorldwideDave]

thank you @wpns - I'm not saying that the BMS shut it off, but I guess the real question is was the solar charge controller supposed to?
The solar charge controller's battery status lights stopped flashing or reading any values, then I noticed that while the solar charge controller stopped displaying anything, and the loads stopped charging things (loads connected to fuse panel direct from battery plus and negative shunt), the shunt meters (one for charge, one for discharge) shut off which was the indicator to me there was no power coming from the battery.

So how would I know, without the ability to connect to the BMS in the battery via bluetooth (mine does NOT have this capability that I can find), if it was the BMS or the solar charge controller that turned off the power? I guess the SCC has no way of telling the battery to stop, as it has no 'load' terminals on the SCC (which Will doesn't recommend using anyway).

 

[wpns]

thank you @wpns - I'm not saying that the BMS shut it off, but I guess the real question is was the solar charge controller supposed to?
The solar charge controller's battery status lights stopped flashing or reading any values, then I noticed that while the solar charge controller stopped displaying anything, and the loads stopped charging things (loads connected to fuse panel direct from battery plus and negative shunt), the shunt meters (one for charge, one for discharge) shut off which was the indicator to me there was no power coming from the battery.

So how would I know, without the ability to connect to the BMS in the battery via bluetooth (mine does NOT have this capability that I can find), if it was the BMS or the solar charge controller that turned off the power? I guess the SCC has no way of telling the battery to stop, as it has no 'load' terminals on the SCC (which Will doesn't recommend using anyway).

Without communications or a shunt, you can't really tell what the SOC is (and even then it's not terribly accurate unless you do something to reset its 'fuel guage' occasionally). You can infer it by voltage, but that's usually very inaccurate and may fight with your BMS.

When the BMS detects (however poorly) that the battery is overcharged or undercharged, then it'll shut off to prevent (further) damage. This will cause the SCC to think there's no battery connected, and the voltage on it's output terminals may be pretty arbitrary.

Communications with the BMS appears to be the best answer, followed by your own shunt, followed by voltage. You really need a good understanding of how these work, what your BMS is, and how these things interact, which this site is a (sometimes overwhelming) great resource for. All I can recommend is studying the issues and asking focussed questions to improve your understanding of your particular setup.

 

[WorldwideDave]

Thank you @wpns - I have a low cost (free to me) solar charge controller (was new in box) and retails for $25 on amazon, so nothing great there. The battery has a BMS - it is a chins 200AH 12v 2560wh battery - but I have no idea which BMS is in it because it has no serial number on the outside of the battery. The shunt I bought on amazon - Will recommended that one.
I am in no way angry that the battery shut down. I am learning with very little pressure and lots of time. With no way to notify me of state of charge remotely, I have the webcam pointing at the shunt's charge and discharge meters, which both show the same voltage. I don't rely on the voltage reading or the LED lights (low, medium, high, full) on the solar charge controller. And it sounds like when a battery is being charged or discharged the BMS will report different voltages to indicate its state of charge (I think I'm saying this right). I have a printout that someone posted about the battery (maybe not my exact battery, but same chins 200 AH 12v battery - they made 2-3 diff versions I think?) which shows the state of charge based on certain voltages. Something like 12.8 = full, 11.4 = 20% etc. I think that a better battery monitor - next on my to buy list - would report SOC more accurately because it could be programmed to know these numbers and thus report out more accurately. Victron smart shunt is not cheap. Considering others, but I still don't have enough panels, a better solar charge controller, another battery, or even an inverter yet. Fun but expensive hobby.

 

[shazam]

How about my NCE… netware 3 certified baby!

Old computer geeks of the world unite! . Double MCSE/NCE here also! Before that....Unix on the IBMs with reel-to-reel for data...TRS80 @ the house.... Good times!

We now return you to your regularly-schedule program....

Jim