Using Lithium Batteries

[Crazy Brit]

I have always said that this idea of only charging your Lithium Batteries to 80% and then only Discharging to 20% is a load of Balony. It is often stated as the way to best look after your Lithium (LiFePO4) Batteries, but really is a nonsense.

Just came across this Video posted yesterday by Will Prowse, who a lot of people regard as THE god of Lithium and Solar and it is good to see he is dispelling this myth. Maybe more people will believe him and use the blooming batteries they bought properly and fully!

I am starting the Video at the point he discusses about charging and discharging levels .... Also watch all to the end!

Remember - Use that Battery!
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This is why I built my own battery. So I could use it as I wanted and if I screwed up I only had myself to blame. I watched a fair bit of Will and the off grid garage particularly for the bms settings. It's not immediately obvious what some do. Having access to all the settings is a real bonus.

I visited a renewable exhibition at the NEC and spoke to one of the techs and he was a bit surprised I was only using 306Ah from my EVE MB30 cells and not the >330 Ah they are capable of. I didn't tell him I got 339Ah out of each cell when I tested them before assembly into the battery! Lol

 

[wildebus]

I dip and and out of Will. He has some great info for sure but don't really care about seeing 20 battery tear down videos a month.
I find Andy Off-grid Garage too hard going. Even when I see a video released that covers a specific topic of interest, his presentation style twists my melons too much to be able to watch for long.

 

[mry716]

May I also suggest a video worth watching - I was surprised as to how much I was able to learn.

 

[wildebus]

May I also suggest a video worth watching - I was surprised as to how much I was able to learn.

Clarkes a nice guy. Had a fairly long conversation with him a few years ago when he was in the Dominican Republic - we did a bit of a collaboration on Hybrid Battery setups.

 

[Pudsey Bear]

The scooters new battery lasted from 7th of November until the 18th no charge left in the car overnight it did drop a bar on each other last three days of use last week and go quite slow but was okay, so I put the fully charged one that came with it in on Monday and it's lost three bars already, so I'll swap in the fully charged new one tomorrow.

Is there anything I can do to recondition the older one to get more out of it, it's not an issue at home as I have the mains to charge it but when it goes back in the van I only have a 12v charger, I don't think using my small LB and the 300w inverter is really an option, but I'm pretty dumb on stuff like this.

Pardon our interruption...

 

[Chasn]

Vegas in winter can go lower overnight than many places in the UK

I don't think the cold charging discussion was in scope for the video topic. If you watch other videos of his, he is fairly obsessive on the topic in fact.

The best option really is not sitting a battery on a heat mat but to have a battery with internal heater as part of the design AND a BMS that works in conjunction with it and directs power accordingly. That way you don't have to mess around with chargers with temperature sensor control and cutoffs... Just let the battery take care of it (but low temp charging is a whole different topic to the one discussed on the video)

I do get the batteries to look after themselves as they power their own heater mats. As my battery pack is made up from 8 individual cells (4S2P) it is necessary to add the heating rather than have it already incorporated. The advantages of self made batteries is cost (£700 for a 600Ah pack) and space (the 8 cells take up the same space as two 95Ah lead acid batteries). I also use these cells to make up off-grid backup power packs (£2000 for 30kwh). Much cheaper than the commercial domestic solar system battery back ups.

 

[CriftinsCampers]

Last week it went down to -6c here one night and the low temp disconnect in my BMS kicked in.
However there’s seemingly a bug in my unknown brand Renogy 200Ah battery BMS which I noticed from the first winter, where it also drops it output to around 12.2v in sub zero conditions unless there’s a significant load such as from my diesel heater, stuff like my >£300 intellitec wall clock using its power manglement feature and turns it’s display off but usb sockets and battery monitors etc continue to work.

Unfortunately what really suffers is the Ablemail AMT12-2 because the input voltage is too low and my chassis battery isn’t then trickle charging.

So I rely on my cheap simple greenhouse heat mat to keep the crappy battery alive.
Conscious the entire battery needs to warm thoroughly I turn the mat on at night normally just before bed and then if the sun appears it will charge and obviously that also solves the output issue as well.

Mines at around 98% charged all day I’ve never really bothered about preventing that but I do lower the bulk voltage slightly when not using the van mainly because the Renogy Rover lithium profiles is rather flawed.

 

[nabsim]

I have never worried about any charge coming in from the solar in sub zero temperatures. Its is such a small current it hasn't affected my battery

 

[wildebus]

Last week it went down to -6c here one night and the low temp disconnect in my BMS kicked in.
However there’s seemingly a bug in my unknown brand Renogy 200Ah battery BMS which I noticed from the first winter, where it also drops it output to around 12.2v in sub zero conditions unless there’s a significant load such as from my diesel heater, stuff like my >£300 intellitec wall clock using its power manglement feature and turns it’s display off but usb sockets and battery monitors etc continue to work.

Unfortunately what really suffers is the Ablemail AMT12-2 because the input voltage is too low and my chassis battery isn’t then trickle charging.

So I rely on my cheap simple greenhouse heat mat to keep the crappy battery alive.
Conscious the entire battery needs to warm thoroughly I turn the mat on at night normally just before bed and then if the sun appears it will charge and obviously that also solves the output issue as well.

Mines at around 98% charged all day I’ve never really bothered about preventing that but I do lower the bulk voltage slightly when not using the van mainly because the Renogy Rover lithium profiles is rather flawed.

Ref the Ablemail AMT12-2, if you connect a 12V line to SW2 (the faston spade tab next to the 0V tab), the AMT will run on "programme9", which is an override routine that turns it on for 9 seconds, off for 1 second, on for 9 seconds, etc and ignores the voltages on both IN and OUT. You loose the battery discharge safeguard but with the lithium the BMS should manage that anyway.

 

[wildebus]

I have never worried about any charge coming in from the solar in sub zero temperatures. Its is such a small current it hasn't affected my battery

Yup, quite right. Only thing to watch out for is if you plug into EHU, but I think you still have those Relion batteries? They will have a decent BMS and you'll be protected anyway I am sure.

 

[nabsim]

Yup, quite right. Only thing to watch out for is if you plug into EHU, but I think you still have those Relion batteries? They will have a decent BMS and you'll be protected anyway I am sure.

No, I couldn't afford the Relions, mine are TN Power. I am careful when mains chargers run although they don't get used very often

 

[wildebus]

No, I couldn't afford the Relions, mine are TN Power. I am careful when mains chargers run although they don't get used very often

I guess what you could do is switch the mains charger to "night mode" (they are the Victron IP22s you have still? think I have that bit right ) and that will halve the current output and will be within the safer limits for cold temp charging.

And the act of charging (or discharging) does warm the battery up anyway to a degree. my batteries like yours are inside the van and even when the interior is at 0 degrees the batteries are warmer. I have never seen the batteries drop below around 3 degrees at the very lowest.

 

[Okta]

Roamer helpfully give recommended charge currents for different temperatures. I suspect they would apply to other Lipo batteries too.

 

[merl]

Roamer helpfully give recommended charge currents for different temperatures. I suspect they would apply to other Lipo batteries too.
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And that data shows that the zero degrees cut off is a complete fallacy. NOTHING happens at zero, there's no cliff edge or line in the sand at zero or anywhere else for that matter it just gets more harmful as the temperature gets lower. The chart shows how permissible charge current gets less with temperature but there's a third factor that's not widely known or talked about yet and that's the battery's state of charge, it's permissable to charge at low temps and relatively high currents providing the battery is in a relatively low SOC.
Jumping in your van and driving it at 5deg C with a high current B2B could be OK if you're batteries are well below fully charged, however if they're already sitting nearly fully charged then you'll probably be damaging them permanently.