Flat lithium battery.

[Rustin]

Camped a couple of nights last weekend. No hookup but have a 300ah fogstar lithium battery. Discharged to about 140/300.

Didn't think much of it.

Away this weekend, Friday evening battery was at about 170/300. Understandable, no sun at all at home in west yorks, and slipped my mind to hook up at home.

At campsite, using heating, charging phones and telly on, low watt electric kettle but switched to kettle on hob.

Last time I looked at the Fogstar app Saturday afternoon, battery had discharged to around 78/300.

Maybe an hour later everything went off, fully discharged.

Went to campsite bloke, paid for electric and hooked up.

Battery has only charged up to 140/300 and then stopped charging.

Any ideas why the battery discharged so quickly when it was roughly at a 1/4 full, and why it has stopped charging from hookup when at 140/300?

Newish battery, only 6 cycles.

Thanks

 

[MichaelT]

You can't rely on the app to tell true soc you need a shunt. There will be lots of small current drains the app does not see that would of taken battery lower than the app shows.

 

[WESTY66]

Have you got charging switched on at the app

 

[eurajohn]

Check the cell voltage.

 

[Pausim]

Sounds like the battery monitor is out of sync with the actual state of charge. I have read on other threads that the Fogstar system needs to be fully charged and discharged a few times before the cells are properly balanced and the app reads properly. I think Fogstar sell an additional active balancing device, some lithium batteries incorporate active balancing as standard.

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[Cush]

what type of onboard charger? Could the electric you paid for run out or trip at the post? What are your draws? It seems you use about 70amps / day.

 

[Rustin]

Have you got charging switched on at the app
View attachment 982252

Have you got charging switched on at the app
View attachment 982252

I think all is as it should be.

 

[Rustin]

what type of onboard charger? Could the electric you paid for run out or trip at the post? What are your draws? It seems you use about 70amps / day.

Had a bloke fit it for us but decent Renogy equipment for b2b, onboard and solar charger and 2000w inverter.

 

[Rustin]

Check the cell voltage.

Is this problematic?

 

[Cush]

Is this problematic?



View attachment 982262

Look good to me. Nothing to activate any shut offs. Good delta . Are you still on ehu? Fuse gone?

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[eurajohn]

Is this problematic?



View attachment 982262

I'm certainly no expert but to me that suggests the battery is not fully charged, so looks as though the charger has stopped way before a full charge, but I guess you have already realised that.
Have you tried an alternative source of charge?

 

[Rustin]

Look good to me. Nothing to activate any shut offs. Good delta . Are you still on ehu? Fuse gone?

I'll check when I get home, see if I get any additional charge for the 30 mile drive.

 

[Pausim]

Cell voltages look well matched and probably about 70% charged. I would try turning the mains charger off and back on again to provoke a new charging cycle.

 

[Rustin]

I'm certainly no expert but to me that suggests the battery is not fully charged, so looks as though the charger has stopped way before a full charge, but I guess you have already realised that.
Have you tried an alternative source of charge?

Will drive home soon and see if it resumes charging.

 

[Rustin]

Cell voltages look well matched and probably about 70% charged. I would try turning the mains charger off and back on again to provoke a new charging cycle.

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[Rustin]

Nice one, quick underpants run to the EHU, unplugged, 20 seconds, plugged back in, charging batteries again. Useful to know for future reference.

Still not sure why it discharged from 1/4 to nothing so quickly unless as posters pointed out, the app is not entirely accurate.

 

[MichaelT]

Nice one, quick underpants run to the EHU, unplugged, 20 seconds, plugged back in, charging batteries again. Useful to know for future reference.

Still not sure why it discharged from 1/4 to nothing so quickly unless as posters pointed out, the app is not entirely accurate.



View attachment 982298

Yes get it to 100% over a few days then fit a shunt.

 

[stevewagner]

I had a Renogy B2b and if failed after two weeks. Had major issues with their customer service. Eventually got another which failed in 3 weeks. Bought a Sterling 70amp B2b which has worked perfectly for over a year.

 

[headlight]

Nice one, quick underpants run to the EHU, unplugged, 20 seconds, plugged back in, charging batteries again. Useful to know for future reference.

Still not sure why it discharged from 1/4 to nothing so quickly unless as posters pointed out, the app is not entirely accurate.



View attachment 982298

Irrespective of the number of cycles the BMS cannot and will never detect any draw under 1.5AH on the 300AH Fogstar.
So the SOC shown on the app can be quite a bit out.
A shunt detects all amps in and out of 0.1AH so is far more accurate.
I don't use the app to monitor the SOC on my Fogstar, I use a Victron Shunt.

 

[Rustin]

Irrespective of the number of cycles the BMS cannot and will never detect any draw under 1.5AH on the 300AH Fogstar.
So the SOC shown on the app can be quite a bit out.
A shunt detects all amps in and out of 0.1AH so is far more accurate.
I don't use the app to monitor the SOC on my Fogstar, I use a Victron Shunt.

Been pricing them up, will get one fitted. Too important, if we weren't on a site with hookup facilities last night would have been tricky, as we'd both had a bit of wine so no quick drive home.

Need an accurate reading.

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[MichaelT]

Been pricing them up, will get one fitted. Too important, if we weren't on a site with hookup facilities last night would have been tricky, as we'd both had a bit of wine so no quick drive home.

Need an accurate reading.

See off grid get funster discount

 

[Lenny HB]

Had a bloke fit it for us but decent Renogy equipment for b2b, onboard and solar charger and 2000w inverter.

Decent is not a word I would use for Renogy, but it's very cheap but you do get failures.
I wouldn't expect the BMS to be that far out unless you have charged it quite a few times and not reached 100%.
More lightly to be a charger problem.

 

[headlight]

Been pricing them up, will get one fitted. Too important, if we weren't on a site with hookup facilities last night would have been tricky, as we'd both had a bit of wine so no quick drive home.

Need an accurate reading.

I fitted a Renogy shunt in a friend's van 2 weeks ago.
IIRC it cost £50 something with a remote display screen, no Bluetooth app.

 

[Pausim]

Irrespective of the number of cycles the BMS cannot and will never detect any draw under 1.5AH on the 300AH Fogstar.
So the SOC shown on the app can be quite a bit out.
A shunt detects all amps in and out of 0.1AH so is far more accurate.
I don't use the app to monitor the SOC on my Fogstar, I use a Victron Shunt.

An external shunt could be more sensitive (I doubt the cheaper ones are) but it will not detect the internal losses such as running the BMS, keeping the Bluetooth awake and natural cell losses. I think it is safer to assume that after all periods of lay up the battery monitoring devices will all have drifted a little off target and will need to re-synchronise after a full charge.

 

[StillGoing]

If you fit lithium install a shunt. The BMS app is inaccurate especially with low currents and if you don’t regularly charge the battery to 100%.

Having said that, the shunt will be inaccurate if the internal battery heaters are on.

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[MichaelT]

If you fit lithium install a shunt. The BMS app is inaccurate especially with low currents and if you don’t regularly charge the battery to 100%.

Having said that, the shunt will be inaccurate if the internal battery heaters are on.

He already has lithium

 

[Guigsy]

The Fogstar BMS isn't sensitive to small currents. So over time it can drift from actual charge. A Victron shunt is much more sensitive, so suffers far less. This generally matters over long periods, like in storage where small parasitic loads get ignored by the BMS.

Last winter, I didn't use the van for a couple of months. My BMS said I was at 90% charge, but the shunt said I was at 30%. I plugged it in to charge and did indeed put in about 70% of the rated Ah capacity of the battery.

But when you're actively touring, it doesn't really make a difference. Most of the time, loads are well above the threshold, so the BMS remains pretty accurate. As long as you fully charge every couple of weeks, it's never going to be that far out.

In this situation, I'd suspect the AC charger either isn't working. Or it's not set to lithium.

 

[Pausim]

If you fit lithium install a shunt. The BMS app is inaccurate especially with low currents and if you don’t regularly charge the battery to 100%.

Having said that, the shunt will be inaccurate if the internal battery heaters are on.

Internal heaters should only use incoming charge currents which would be detected by an external shunt but probably mistaken for charging. Unfortunately some cheaper batteries cheat and use internal battery power to run the heaters instead of incoming power, they detect an incoming charge and turn the heaters on but this can flatten the battery because the incoming charge could be less than the consumption of the heaters.

 

[Guigsy]

Internal heaters should only use incoming charge currents which would be detected but probably mistaken for charging. Unfortunately some cheaper batteries cheat and use internal battery power to run the heaters instead of incoming power, they detect an incoming charge and turn the heaters on but this can flatten the battery because the incoming charge is less than the consumption of the heaters.

Regardless as to whether the heaters only run on external power or not, an external shunt would loose track of charge levels when the heaters come on.

In reality, it's not much of an issue. When you're using the van, the battery isn't going to be anywhere near freezing. In the UK, it's a rare scenario where the van is below freezing, but there's good current to charge the battery.

 

[Pausim]

Regardless as to whether the heaters only run on external power or not, an external shunt would loose track of charge levels when the heaters come on.

In reality, it's not much of an issue. When you're using the van, the battery isn't going to be anywhere near freezing. In the UK, it's a rare scenario where the van is below freezing, but there's good current to charge the battery.

I agree. My previous Lipo worked well for 6 or 7 years without the need for internal heaters so I was happy to choose one for my current van without them.

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