CTEK D250SE and Renogy 100Ahr Lithium Battery

[Jimsky]

For years my CTEK D250SE system has worked well - supplying the auxiliary battery from Alternator when moving, and solar panels when stationary. However, I have just replaced my AGM aux battery with a nice new Renogy 100Ahr lithium battery and now it refuses to charge it from either source at more than 0.5A (it should be doing 20A at least). To let it know the battery has changed from AGM to Lithoium I moved the small black lead to the + terminal as the instructions said and confirmed that it has adjusted the voltage accordingly but ...... it seems to think the Renogy battery is full, even though it's only 70% full.

Has anyone got this combination working? or are the 2 just incompatible?

Thanks, J

 

[Pausim]

How do you know it is only 70% full? What voltage is the battery sitting at?

 

[Jimsky]

How do you know it is only 70% full? What voltage is the battery sitting at?

Hi and thanks for responding. You can connect via Bluetooth to the Renogy battery with an APP that tells you everything about its state of charge, voltage and current in or out of it. I suspect that in term sof voltage, the CTEK and Battery might disagree on the definition of full. I have also put a big 50A load on the battery to try to induce the CTEK to kick in, but no joy there either. I'd really like to know if anyone has this combination working so I will know if if might be faulty equipment, rather than an incompatibility.

 

[Pausim]

You might be right about the CTEK disagreeing about what is a full charge. The battery manual says to charge at 14.4V, which is a normal LiFePO4 charging voltage. The CTEK manual says it charges at 14.2V maximum on the Li profile which is lower than I would expect. However I would still expect it to achieve more than a 70% charge. What voltage is the battery showing when at rest?

 

[Jimsky]

At rest it shows 13.3V - and I should add that it varies very littl between 70 and 100%. The alternator gives a good 14.2V, the solar gives 22.5V. I have learned from Renogy that their battery does not need the 5-stage profiled Litium charge routing that the CTEK provides - it only needs a constant 14.2 volts. Could it be that the CTEK just thinks that at 13.3 V the Li battery just needs and occasional float pulse?

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[Pausim]

At rest it shows 13.3V - and I should add that it varies very littl between 70 and 100%. The alternator gives a good 14.2V, the solar gives 22.5V. I have learned from Renogy that their battery does not need the 5-stage profiled Litium charge routing that the CTEK provides - it only needs a constant 14.2 volts. Could it be that the CTEK just thinks that at 13.3 V the Li battery just needs and occasional float pulse?

It is possible, the CTEK does seem to have an unusual Li charging profile.

 

[Jimsky]

OK, so I think I have the conclusive evidence I needed to show they are just not compatible. I reinstalled my AGM battery (Changed the RED wire to (-)) and hey presto everything works as it should. On loading the AGM the solar panels kick in and cover the demand. With them off and the engine running it takes all the current it needs from the alternator. Rather a lot of time went in to finding that out. Until my RENOGY DCDC charger arrives (just bought one) I'll reconnect the Li battery and see if I find any state of where the CTEC is happy to cut in. SOLVED!!!!!

 

[Jimsky]

Update - Renogy and CTEK have the same wiring configuration. Uprated the fuses, swapped over the wires and hey presto, everything works as it should and of course with the BT dongle the Renogy tells me everything it is up to. On solar and Alternator it will give 25 amps from each. If you switch off the solar, it will give 50amps from the alternator along - that’s quick charging for a battery that will accept 100a. Job done.

 

[tomdub]

hello. Jimsky I have had a miserable experience with the ctek d250se after changing to lithium. I have spent hours wiring, rewiring, etc believing I was the culprit causing the issues. I rarely get beyond 80% charge, it seems to want to keep me at 13.3v. Like you I tried heavy loads but still no joy. I hate the thing. Taking your lead I put my mates AGM in and like you describe the ctek does what it says it does, wish i'd thought of doing this it would have saved me hours.
So thanks for your post, I'm done with the d250se now, I'm just about to order the renogy dc/dc. Can you give me and update on your experience with it, any issues you may have had. The blurb about the BT app seems top suggest through it you can limit the current from either source to your liking. Can you confirm this is a function available in the app. I ask as I'd like to instal it into my current wiring where I'd need to keep the alternator to 25amp in all circumstances and not have the 50amp alternator charge kick in.

Thanks for ending my misery.

 

[Pausim]

I have had a miserable experience with the ctek d250se after changing to lithium.

I see from the technical data that the CTEK D250SE LiFePO4 profile is only 14.2V, which would fall short of a full charge for my battery. My Votronic B2B manual shows this voltage for a couple of makes of LiFePO4 but most are 14.4V or 14.6V.

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[tomdub]

Yeah mine is 14.6. I never realised 0.whatever volt could be so important and effect things.

 

[CAB96]

hello. Jimsky I have had a miserable experience with the ctek d250se after changing to lithium. I have spent hours wiring, rewiring, etc believing I was the culprit causing the issues. I rarely get beyond 80% charge, it seems to want to keep me at 13.3v. Like you I tried heavy loads but still no joy. I hate the thing. Taking your lead I put my mates AGM in and like you describe the ctek does what it says it does, wish i'd thought of doing this it would have saved me hours.
So thanks for your post, I'm done with the d250se now, I'm just about to order the renogy dc/dc. Can you give me and update on your experience with it, any issues you may have had. The blurb about the BT app seems top suggest through it you can limit the current from either source to your liking. Can you confirm this is a function available in the app. I ask as I'd like to instal it into my current wiring where I'd need to keep the alternator to 25amp in all circumstances and not have the 50amp alternator charge kick in.

Thanks for ending my misery.

Jimsky was last on the forum in 2022 and is not a paid up subscriber, so unlikely to reply!

Seems as if you found the solution to your problem though