Inverter issue - urgent help required

[TallPaul_S]

View attachment 258131
Not sure how that screen gets its info

Hmm, not sure how that system works and if it has a shunt and can read the exact charge level.

Regardless, the voltage of your battery is why you're getting the issues, it's dropping below 11v when you're running the inverter.

That couple of amps of solar should still be raising the voltage too.

Could be a few things:

Soc is wrong and you're actually at 10% or 20% charge
Batteries aren't balanced and one is low charge, it should be pulling from them both at the same time (IE one battery at 10.5v and one at 13v)

 

[Bav]

Hmm, not sure how that system works and if it has a shunt and can read the exact charge level.

Regardless, the voltage of your battery is why you're getting the issues, it's dropping below 11v when you're running the inverter.

That couple of amps of solar should still be raising the voltage too.

Could be a few things:

Soc is wrong and you're actually at 10% or 20% charge
Batteries aren't balanced and one is low charge, it should be pulling from them both at the same time (IE one battery at 10.5v and one at 13v)

Okay, well thanks for your assistance.

Looks like it's game (or at least trip) over. We're not on EHU and the weather (and the forecast) is shite, so this ain't going to get better any time soon.

 

[TallPaul_S]

Okay, well thanks for your assistance.

Looks like it's game (or at least trip) over. We're not on EHU and the weather (and the forecast) is shite, so this ain't going to get better any time soon.

I'd try running the engine whilst you have the inverter running, then leaving the engine running for 40 mins or so to put some charge back into the batteries, and see what the voltage gets to when you've switched off.

 

[Bargy62]

Okay, well thanks for your assistance.

Looks like it's game (or at least trip) over. We're not on EHU and the weather (and the forecast) is shite, so this ain't going to get better any time soon.

See if you can change pitches and get on EHU unless its a no EHU site

 

[Bav]

See if you can change pitches and get on EHU unless its a no EHU site

In my infinite wisdom, I decided not to bring the hookup cable.

That'll learn me.

 

[The Flying Scotsman]

In my infinite wisdom, I decided not to bring the hookup cable.

That'll learn me.

Most sites have leads you can borrow Bav.
Worth an ask

 

[Bav]

Ok, so just returned from a 90 min run in the van. SOC went from 64%, to 78%.

Disregarding solar input (it was misty & foggy throughout), I think that's about right for a 20A DC-DC charger: 90 mins at 20A/hr equates to 30Ah and 14% of 220Ah equates to 30.8Ah.

Voltage went from 11.65v to 13.12v, which means, according to LiFePO4 voltage charts, SOC has gone from <10% to ~60%.

An increase of 50% in SOC arising from an input of 30.8Ah, would suggest (to me) a total LB capacity of ~62Ah (as opposed to the 220Ah I think I have)... and that's where I get completely flummoxed.

Can anyone explain?

 

[Sackmycook]

Yeah, you didn't have enough juice to cook yer eggs this morning

 

[roadtripper]

I think I'd advise waiting until you have a known trusted multimeter and take direct readings from the batteries before doing too much detailed diagnosis.

Remember all voltages used for accurate SoC need to be for a battery under no load (nothing out nothing in) and rested for a good 20-30 mins
Lithium in particular has a behaviour where the voltage is higher at the end of charger for quite a bit and then settles back - it's why the float voltage can be quite a bit lower.

If it's not obnoxious to the neighbours run the engine to support the batteries when you are under heavy load on the inverter - this is what we do on the narrowboat.

 

[Bargy62]

Most sites have leads you can borrow Bav.
Worth an ask

or have a run out and find a camping shop and buy a EHU lead better than all the grief and worry

 

[Bav]

Yeah, you didn't have enough juice to cook yer eggs this morning

I'm not a morning person as it is (barely an afternoon one tbh), so woe betide anyone/anything that comes between me & my brekky.

 

[CJW]

Just looked up the system you use. Looks really neat.

Battery monitor PICO for boats, campervans, RVs - Simarine

The PICO battery monitor delivers all data about your batteries (voltage, SOC, time to charge & discharge ...), tank levels, fridge

simarine.net

Only thing my feeble brain can imagine is that the shunt (there’s a link to the manual) isn’t wired properly and it’s not registering the draw correctly, giving the impression of there being charge available when there isn’t.

 

[roadtripper]

If there is a pair of LBs is there a shunt per LB or are they wired in a bank with a single shunt to the bank?

If it's a single shunt to a bank then any current flowing between the 2 batteries would never be seen. So if one of the batteries was slightly more aged than the other it could be trying to charge itself from the healthier one and the system would never see it but you'd be loosing charge through heating loses.

This is one of the big risks with lead accident battery banks where a failing battery can parasitically drain and damage the remaining healthy ones. The lithium situation is much more murky due to the BMS, a good system where the BMS communicate and the bank acts as a single battery should do much better, but the simpler systems are likely prone to the same risk.

I really don't recommend banks unless absolutely necessary because of this. We have to have a 4 battery bank in the narrowboat and the downside of the capacity is the battery lifetime is never as good as they would be standalone as the first to age ages all the rest.

 

[Bav]

If there is a pair of LBs is there a shunt per LB or are they wired in a bank with a single shunt to the bank?

If it's a single shunt to a bank then any current flowing between the 2 batteries would never be seen. So if one of the batteries was slightly more aged than the other it could be trying to charge itself from the healthier one and the system would never see it but you'd be loosing charge through heating loses.

This is one of the big risks with lead accident battery banks where a failing battery can parasitically drain and damage the remaining healthy ones. The lithium situation is much more murky due to the BMS, a good system where the BMS communicate and the bank acts as a single battery should do much better, but the simpler systems are likely prone to the same risk.

I really don't recommend banks unless absolutely necessary because of this. We have to have a 4 battery bank in the narrowboat and the downside of the capacity is the battery lifetime is never as good as they would be standalone as the first to age ages all the rest.

Unfortunately, I don't know anything about the battery install - I just know there's 2 of them, they're 110Ah each and they're LiFePO4.

I’ve previously requested a wiring schematic of the power system and, whilst they didn't say no, they didn't say yes either. I suspect they don't have one and don't want to spend additional effort for a conversion that's already out the door.

 

[Pauly]

Where abouts are you and how long you staying for ?
I live on the devon/cornwall border and happy to come help out if you need some testing done (im a sparky) or can bring you a hookup lead if you need one ?

 

[czmate1999]

Unfortunately, I don't know anything about the battery install - I just know there's 2 of them, they're 110Ah each and they're LiFePO4.

I’ve previously requested a wiring schematic of the power system and, whilst they didn't say no, they didn't say yes either. I suspect they don't have one and don't want to spend additional effort for a conversion that's already out the door.

had similar with mine at busfest. mine dropped below 40% and the microwave would only run for a minute then stop. think its safety mechanism built into the inverter. plugged in to hookup and it was fine and the when above 50% - on battery it was fine... think its to do with the load being pulled...

 

[Dellmassive]

been busfesting, so off grid with beergoogle.

looks like you have low voltage issue, 11.65v or whatever it is.

maybe due to low battery charge, as you say its ok when engine running.

cables too thin and getting volt drop?


post some pics of the inverter, batts, connections etc etc

 

[Bav]

Where abouts are you and how long you staying for ?
I live on the devon/cornwall border and happy to come help out if you need some testing done (im a sparky) or can bring you a hookup lead if you need one ?

A very generous offer @Pauly and much appreciated, but I really can't put you to the trouble.

We're due to go home on Wednesday and I'm sure we can muddle through 'til then - just need a little sun or, failing that, to cook on gas instead of lekky.

Cheers.

 

[Dellmassive]

had similar with mine at busfest. mine dropped below 40% and the microwave would only run for a minute then stop. think its safety mechanism built into the inverter. plugged in to hookup and it was fine and the when above 50% - on battery it was fine... think its to do with the load being pulled...

the battery APPs / BMS can drift out of whack - some times the app is wrong.


normally full discharge, then re cgharge will get them back again.

 

[Bav]

the battery APPs / BMS can drift out of whack - some times the app is wrong.


normally full discharge, then re cgharge will get them back again.

When you say 'full discharge', you mean to 0%? I thought you weren't meant to discharge LiFePO4 below 20%?