C-Tek D250 SE and lithium charging - Expert required
Submitted: Thursday, Mar 10, 2022 at 16:45
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JJAdv
I have a friend with one of these. Its seems to have a strange profile, when compared to how my Redarc stuff works
This set up has a Victron meter as
well, so we can see whats happening.
When charing the battery up (Lithium 100AH) if will charge it to 100%. Once it gets to 100% it will stop charging, and the appliances will start to bring the battery back down. The C-tek does not continue to supply any power, the battery will drop by 10% + before the C-Tek decides to charge again. If you disconnect the C-Tek it will start to charge again.
C-Tek tell us this is the way it should work. The issue is, when trying to be fully charge right at the end of the day with your panels, you could be as much as 10 to 15% down, as the C-teck has decided not to charge.. if this is the way they work, its stupid..
My redarc just keeps the battery at 100% and supplies the power the appliances need as
well. Right up to the point solar is no longer supplying any power.
Can any experts on C-Tek comment on how these chargers should work, is C-tek correct in stating this is how they work?
PS: The Standard non Lithium version of this charger we have, charges "normally" as I would expect, always keeping the battery at 100%.. We just used the AGM profile and that seem to work for now.
Reply By: Frank P (NSW) - Thursday, Mar 10, 2022 at 17:22
Thursday, Mar 10, 2022 at 17:22
JJ,
I'm no expert but I've been reading what they say. I also talk to my lithium battery supplier, EV-Power in WA, who supplied my Karavan batteries.
He says what Ctek says. IE, lithium batteries in service should be charged to 100% then stop the charge, use them a bit and resume the charge. A properly configured lithium charger will do that. Even better, if capacity and useage allows it, limit charge to 80-90%. This is what battery electric vehicles do - they have an unused and unaccessable top and bottom buffer so that even when the gauge says 100%, the battery is not at 100% and when it says 0% the battery is not dead flat - both of which influence longevity.
For longevity they should not be kept at 100%, especially in hot weather, so leaving a trickle on them to keep them at 100% is not ideal.
I know there will be differing points of view - the Redarc vs Ctek philosophies is a good example.
There won't be catastrophic failure if kept at 100% but longevity will be reduced, according to my sources who I consider expert and reliable. Longevity is possibly more relevant when considering the high purchase cost of Li batteries - depends on the depth of your pockets, I suppose :-)
For long term storage they should be stored at 50-70% IIRC. That's what I do with my Karavan batteries.
PS:
Love your vids, BTW
AnswerID:
639793
Follow Up By: Gbc.. - Thursday, Mar 10, 2022 at 19:04
Thursday, Mar 10, 2022 at 19:04
Everything I have read agrees with you. Lithium at 100% isn’t great.
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Reply By: Member - LeighW - Saturday, Mar 12, 2022 at 09:47
Saturday, Mar 12, 2022 at 09:47
Generally accepted that a Lithium charger should charge to whatever level you have set it for then turn off and not start charging again until battery voltage has dropped to the predefined level.
In practice manufacturers have gone generally one of two ways, they either do the above or they go into a power supply mode otherwise generally know as float, the float voltage will be a little lower than the float voltage for a AGM for existence. They do this as the problem becomes what at what voltage do you trigger restarting the charging, it is difficult with Lithium's to detect when 2% for instance has been taken out of the battery, can be done by monitoring Ah in and out but that adds extra cost to the charger.
In reality the power supply mode for cycling daily is just as good as the batteries want remain at 100% for long periods of time, only becomes an issue if floating 24/7. Also ensures battery is at 100% when the sun goes down which may be critical in small battery setups. If you have a lot of over capacity and you want to ensure maximum life of the batteries then may be the no float method is best for you.
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Follow Up By: JJAdv - Saturday, Mar 12, 2022 at 11:46
Saturday, Mar 12, 2022 at 11:46
OK, but the question is "is this behavior the normal behavior for a CTEK" as no other charger we have tried works like this. All other chargers will all keep the battery at 100%. The BMS and the battery design will be such that the cells are never actually at 100%.. even if the meters state 100%..
Just like a Tesla does..
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Follow Up By: Member - LeighW - Saturday, Mar 12, 2022 at 20:58
Saturday, Mar 12, 2022 at 20:58
Early Enerdrive DCDC chargers charge till they reached the set parameters then turned off. Restarted charging when battery dropped to around 13.3V so that type of behaviour is not unique. Their current version goes to power supply mode.
According to the CTEK manual charger goes into float mode for 2 hours then switches to pulse mode whereby it gives a pulse a 1 hour pulse charge and an auto pulse 10 days. I assume that means when the battery drops to a certain level it will go into charge mode for an hour. If battery not used then it will give a one hour every 10 days.
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Reply By: Member - Captain (WA) - Sunday, Mar 13, 2022 at 19:02
Sunday, Mar 13, 2022 at 19:02
It seems the C-tek is doing what its designed to do, but as you rightly pointed out, you can lose up to 10% of battery capacity if the solar drops off while at the lower end of its deadband.
The Redarc BMS 30 has two modes, Touring and Storage. In Touring mode (lithium profile), it keeps the batteries at 100% capacity, ready for use. But in storage mode, it switches off at 100% and stay off until less than 90%.
The C-tek profile seems to be very similair to the Redarc Storage mode and maximises battery life. But when you are using your van and want maximum power available, the C-tek seems to prioritise battery life over maximum power capacity.
Not sure why C-tek only has the one mode, the Redarc with its Storage and Touring modes seems to have typical useage patterns covered much better.
Cheers
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