Battery charging

molly 2 said:
Tried to charge my Leisure battery sargent charger only putting 1 amp in , then it dawned on me it is too bloody Cold ,
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Too Cold? It's a balmy 3C and I'm in me Speedos 🤡
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Battery is charging ok as well ;)
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Maybe 1a is all it needs.

I looked at mine today while draining down (I meant to di it the other day but I was using the water.


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Leisure batt with shunt.

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Leasure batt with long time observations

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I just downloaded the data from My ancell battery monitor, very easy to understand and almost minute by minute, it all seems to be accurate enough for my needs.


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merl said:
Nothing to do with the cold.
What battery type do you have?
Do you have solar?
If you don't have solar, How long has it sat since you last used EHU or driven?
Where are you getting the 1A charge figure from?
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Cold is an issue for lithium batteries. Most BMS's (battery management systems) inhibit charging when close to freezing to protect the battery. This is a good reason to make sure the batteries are installed within the heated part of the vehicle. If you have Bluetooth access to the BMS settings you can usually adjust the temperature at which this happens. I leave mine set to +5degC. Discharging is unaffected. Significant load is normally only when the 'van is in use so the temperature is then usually high enough for charging.
 
The safe charging lithium at low temperatures is far more complex than the common notion of "Don't charge below zero"
There is no cliff edge at zero deg but rather a gradual slope of increasing 'risk'.
This risk doesn't only vary with temperature but also charge current and state of charge.
As a result you will cause more damage to a lithium battery if you charge it at 0.5C rate at 95% state of charge at +10deg C than you would if you charged the same battery at minus 15 Deg C at 0.01C rate at 50% state of charge.
I think the only time you'd need a heater pad would be if you used your van in the winter and your batteries were sited outside the habitation area in external temperatures.
Here's a tip for anyone who's lays their van up over the winter and is concerned about their solar damaging their lithium battery.
Adjust the solar absorbtion voltage to 13.1v with a recharge (if adjustable) to 13.0v. This will ensure the battery sits partially charged.
The amount of charge current you'll get from your solar over the winter won't be sufficient to cause any damage at this reduced SOC even if we get seriously low temperatures.
As mentioned, there is an increased risk from high charge currents so be wary of starting the engine with a powerful B2B when the temp is low AND your battery is very close to full charge.
 
In my experience with lifepo4 over the last 6 years if you are in the UK you won't get anywhere near enough solar harvesting to worry about charging a cold battery. As Merl says zero doesn't mean you can't charge lifepo4 although I would advise you check the specs for you own battery so you know for sure. I can charge to minus 10 degrees with mine albeit at a low charge rate.

I have been up on Cairngorm when its -6 during the day, lovely blue sky and sun and harvesting on 300W panels was negligible. I did wait until I had brought the battery temp up to around +5 before I started my engine and the B2B kicked in but solar not a concern for most.
 
merl said:
The safe charging lithium at low temperatures is far more complex than the common notion of "Don't charge below zero"
There is no cliff edge at zero deg but rather a gradual slope of increasing 'risk'.
This risk doesn't only vary with temperature but also charge current and state of charge.
As a result you will cause more damage to a lithium battery if you charge it at 0.5C rate at 95% state of charge at +10deg C than you would if you charged the same battery at minus 15 Deg C at 0.01C rate at 50% state of charge.
I think the only time you'd need a heater pad would be if you used your van in the winter and your batteries were sited outside the habitation area in external temperatures.
Here's a tip for anyone who's lays their van up over the winter and is concerned about their solar damaging their lithium battery.
Adjust the solar absorbtion voltage to 13.1v with a recharge (if adjustable) to 13.0v. This will ensure the battery sits partially charged.
The amount of charge current you'll get from your solar over the winter won't be sufficient to cause any damage at this reduced SOC even if we get seriously low temperatures.
As mentioned, there is an increased risk from high charge currents so be wary of starting the engine with a powerful B2B when the temp is low AND your battery is very close to full charge.
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I totally agree with all the points raised. However as most BMS's can't cater for all these variables a choice has to be made for a temperature for the BMS to turn off charging. Although my battery compartment has some insulation on the bottom and sides and is open the the heated part of the vehicle at the top, I did put heater mats under the cells and use a temperature controller. This helps to avoid the need for the BMS protection and the two systems ensure redundancy to avoid battery damage.
 
Nabsim said:
In my experience with lifepo4 over the last 6 years if you are in the UK you won't get anywhere near enough solar harvesting to worry about charging a cold battery. As Merl says zero doesn't mean you can't charge lifepo4 although I would advise you check the specs for you own battery so you know for sure. I can charge to minus 10 degrees with mine albeit at a low charge rate.

I have been up on Cairngorm when its -6 during the day, lovely blue sky and sun and harvesting on 300W panels was negligible. I did wait until I had brought the battery temp up to around +5 before I started my engine and the B2B kicked in but solar not a concern for most.
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As you say solar is unlikely to damage a lithium battery. The biggest risk is on cold starts from the alternator.
 
I get so confused with all this work of the divil stuff, I have four battery monitors now, (who said I'm paranoid????) not really they all tell me different things, one keeps a 72 day long-term memory of the LB, I was thinking of getting one for the VB, but I probably willn't. The others are simple 5 day monitors, and one is a shunty jobby, (tech term) which informs me of current use etc

No I don't want a little blue box.
 
Chasn said:
As you say solar is unlikely to damage a lithium battery. The biggest risk is on cold starts from the alternator.
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I have a Renogy 40A B2B which has the option to toggle with a remote switch to 20A. It is activated from the alternator D+ so I've wired in a 3 position switch so I can have 40A, 20A or Zero charge. It's generally left off because in the summer the solar usually does the job, certainly off during the winter for the reasons already mentioned.
 
Pudsey Bear said:
I get so confused with all this work of the divil stuff, I have four battery monitors now, (who said I'm paranoid????) not really they all tell me different things, one keeps a 72 day long-term memory of the LB, I was thinking of getting one for the VB, but I probably willn't. The others are simple 5 day monitors, and one is a shunty jobby, (tech term) which informs me of current use etc

No I don't want a little blue box.
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You dont need a blue box Kev, things are looking great on your van so far, just keep whatsapping me images from your monitoring devices and I'll keep my eye on what's happening and prevent the flat battery/knackered ECU issues occurring again.
There's no perfect solution Kev, we've all seen people getting completely flumoxed because their dead simple PDU display with 3 lights says the battery is great and then they go flat in no time. The other extreme is to monitor the capacity in far more complicated and sophisticated ways BUT then people are faced with the not so simple process of interpreting the results. As we've seen having a myriad of voltage readings from monitors and particularly BMSs can lead to constant monitoring and high anxiety levels because things don't appear to absolutely 100% perfect. Be thankful you've not got a Bluetooth BMS on a lithium battery, you'd probably be well stressed about cell imbalances by now mate!
 
I'm a lot happier with it now the cold has arrived, and I can see the true values 24/7 if I feel the need, rather than supposition.

I just wish the BT would reach a bit further on these colder days.
 
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