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Old 09-01-2020, 08:35   #1
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Just installed LiFePO4 and solar array not working/going crazy.

Hey CF,

I was up til 0400 today installing my new battery bank, and solar array. Nothing is working as expected, so I was hoping I could glean some help from you all. 3 issues:

- The battery cells are 100ah 3.2v arranged in 2p4s to make a 12.8v 200ah system. They arrived a couple of weeks ago and I immediately tested them with the multimeter. 3.29 volts per cell. And 13.16 when connected in 2p4s. So far so good, I thought. Hook them up last night and the total voltage reads 13.05 volts on both my $20 battery monitor screen and on the victron MPPT. But multimeter shows 3.29 volts per cell and 13.15 total. Multimeter is just garbage, then, I guess?

- I hooked up my circuit following the attached diagram, except I ran the negative lead on the battery to ground on the engine block. That's what I had done with my lead acids before and it worked fine. This time I get voltage readings from the monitor and the MPPT, but no power to the house. Might be a bad connection somewhere, I guess. Any thoughts as to troubleshooting this?

- Finally, I wake up this morning hoping that at least the victron charger is working well, and I see the voltage/amperage graph attached. Amps are 0 and voltage seems to be oscillating between about 15 and 35 volts! What on Earth have I done?

Anyway, I'm totally exhausted. Going to try to catch a few more hours of sleep and then get back to it. Hoping to get the kinks worked out today, and that I haven't done anything seriously damaging to all this.

Sincerely.
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Old 09-01-2020, 14:38   #2
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Re: Just installed LiFePO4 and solar array not working/going crazy.

Well, this was a bit of bleary panic post after an exhausting night of wiring. I woke up refreshed and managed to sort most of it out. Cheers.
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Old 09-01-2020, 15:03   #3
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Re: Just installed LiFePO4 and solar array not working/going crazy.

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Originally Posted by Santiano View Post
Well, this was a bit of bleary panic post after an exhausting night of wiring. I woke up refreshed and managed to sort most of it out. Cheers.
Do you mind sharing what the problem was for the benefit of others
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Old 09-01-2020, 15:09   #4
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Re: Just installed LiFePO4 and solar array not working/going crazy.

The Victron MPPT stabilized its voltage readings around 40 by the time the sun was high. That is a problem I'll have to address if it recurs, but for the moment I'm just glad it's looking good.

The general problem with the circuit was a bad fuse or fuse holder, haven't worked out which yet. But that's solved.

I'm still getting different readings from different instruments, but chalking that up the the variety of cheap Chinese monitors and multimeters and balancers I have currently. Gonna have to shell out for a nice(er) multimeter soon.
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Old 09-01-2020, 16:10   #5
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Re: Just installed LiFePO4 and solar array not working/going crazy.

I think the issue is that the Victron display is reporting the solar array voltage which is and will be very different from the battery voltage.

The swings you saw were just the solar controller testing to see if the panels could deliver any useful power.

You need to look at the MPPT output, not the input.
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Old 09-01-2020, 16:29   #6
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Re: Just installed LiFePO4 and solar array not working/going crazy.

Oh, I was definitely not under the impression that my battery voltage was swinging between 15 and 40 volts. But on the other hand, I do not know how solar controllers work - this is my first experience with one. I hope you are correct and it was just a test mode of the mppt.

Anyway, the mppt still shows the battery voltage at 13.55 at the same time as both my other monitors show it at 13.25. still a bit disconcerting.
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Old 10-01-2020, 09:55   #7
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Re: Just installed LiFePO4 and solar array not working/going crazy.

Quote:
Originally Posted by Santiano View Post
Oh, I was definitely not under the impression that my battery voltage was swinging between 15 and 40 volts. But on the other hand, I do not know how solar controllers work - this is my first experience with one. I hope you are correct and it was just a test mode of the mppt.

Anyway, the mppt still shows the battery voltage at 13.55 at the same time as both my other monitors show it at 13.25. still a bit disconcerting.
Are all devices measuring from exactly the same point?
.25 volt seems like a lot of difference even for cheap meters.
I suggest checking each connection with volt meter looking for a high resistance point.
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Old 10-01-2020, 15:12   #8
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Re: Just installed LiFePO4 and solar array not working/going crazy.

While it may seem like a lot of work, use another battery unconnected to anything, to check you instruments. I pulled out my car battery and making sure that all the instruments to be check are isolated, I found quite a bit of variation in voltage readings between instruments. The real trick is finding out which instrument was accurate.
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Old 11-01-2020, 06:04   #9
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Re: Just installed LiFePO4 and solar array not working/going crazy.

If a BMS system is disconnecting and reconnecting due to over voltage it would look like there were wild voltage swings on the battery.
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Old 12-01-2020, 00:44   #10
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Re: Just installed LiFePO4 and solar array not working/going crazy.

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The general problem with the circuit was a bad fuse or fuse holder, haven't worked out which yet.
I'm not sure which type of fuse holder you have, but beware of the twist-together type. (See photo.) They are not water tight, are constructed of POS (Plain Old Steel) that rusts and worst of all, the connection is held by an internal spring -- if enough tension is placed on the wires, the connection with the fuse will pull apart internally breaking the connection. The connection will re-make when the tension is released. That can make you crazy if the problem is intermittent, like in a wiring bundle that moves at sea.

The fuse holder below will corrode and fail in a very short time in a seawater/salt air environment. They also tend to melt before the fuse blows. They have no place on a boat. Their only redeeming quality is that they are dirt cheap.

For low current point-to-point wiring, I prefer the watertight ATO/ATC type fuse holders.
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Old 12-01-2020, 02:44   #11
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Re: Just installed LiFePO4 and solar array not working/going crazy.

Quote:
Originally Posted by Santiano View Post
Oh, I was definitely not under the impression that my battery voltage was swinging between 15 and 40 volts. But on the other hand, I do not know how solar controllers work - this is my first experience with one. I hope you are correct and it was just a test mode of the mppt.
Yes Tanglewood, is correct (everything he posts is worth reading carefully). Your graph is displaying solar voltage not battery voltage.

You can see here in the first photo that solar voltage is selected on my system. In the second photo battery voltage is selected (it is almost a straight line). If you want, you can display two parameters on the graph, or even alter the time scale. In the third photo both battery voltage and solar voltage are shown:
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