[Guide] DC-DC Charger (for leisure battery) -- How I Done It --

[brenmona]

Hi @TallPaul_S. Yes, Thankyou, I do know the converter company changed the black wire over when he changed to the lithium battery. It just seems that the Ctek will not allow over 13.2v to get through to the battery when charging off solar

Thanks again

 

[brenmona]

I just connected the black battery select wire to the SB input on the CTEK unit when I did mine.
Just checked my Renogy app and it’s showing 100% at 13.2v.
What are we saying the LiFePo voltage should be?

I thought and `I could be wrong that Lithium was around the 14.2 Volt resting?

 

[TallPaul_S]

I thought and `I could be wrong that Lithium was around the 14.2 Volt resting?

LiFePO4 at 100% SOC is 14.2v when charging and 13.5v when not charging. Depending on battery of course, but they're all close to that figure.

 

[Bigsidavies]

Hi @TallPaul_S. Yes, Thankyou, I do know the converter company changed the black wire over when he changed to the lithium battery. It just seems that the Ctek will not allow over 13.2v to get through to the battery when charging off solar

Thanks again

Although I have the CTEK250SE my solar is managed with a Victron MPPT controller. Even over summer I don't think I ever saw more than 13.4V in the battery.
You got me wondering now, so I'm going to connect it to EHU tomorrow and see what the victron ac-dc takes the voltage to.

Edit:- just found this on the Renogy website which shows that a fully charged battery at rest should be 13.6v

A Comprehensive Guide to LiFePO4 Voltage Chart

Unlease the secrets of LiFePO4 battery voltage and learn charge cycles, optimal usage and performance in our guide.

www.renogy.com

 

[Salty Spuds]

Although I have the CTEK250SE my solar is managed with a Victron MPPT controller. Even over summer I don't think I ever saw more than 13.4V in the battery.
You got me wondering now, so I'm going to connect it to EHU tomorrow and see what the victron ac-dc takes the voltage to.

I found that the standard Victron lithium profile didn’t get my SuperB Epsilon battery high enough to reset the SOC to 100% on the BMS. I contacted SuperB & they sent me some charging figures, Voltage/time etc. I setup a custom profile on my Victron app & used it across all 3 devices, solar/mains/B2B. Works a treat.

 

[TallPaul_S]

Although I have the CTEK250SE my solar is managed with a Victron MPPT controller. Even over summer I don't think I ever saw more than 13.4V in the battery.
You got me wondering now, so I'm going to connect it to EHU tomorrow and see what the victron ac-dc takes the voltage to.

Edit:- just found this on the Renogy website which shows that a fully charged battery at rest should be 13.6v

A Comprehensive Guide to LiFePO4 Voltage Chart

Unlease the secrets of LiFePO4 battery voltage and learn charge cycles, optimal usage and performance in our guide.

www.renogy.com

What you'll typically see, if you have any load at all on the battery, is it going to 14.2v when it's charging, but it'll only be there very briefly before dropping to 13.5/6v - then if you have any load it'll drop a little more to 13.3/13.4v.

Like so:


In the above chart, mine only sat at 13.5v for about an hour, that's with a 0.5a draw on it - and it started dropping away when any solar input would have also gone.

So you might never see the battery at 14.2 or 13.5/6v as it'll only ever be there briefly - but it must be getting to that voltage otherwise it's not getting fully charged.

Mine currently is at 99% SOC and only 13.35v.

 

[Bigsidavies]

I found that the standard Victron lithium profile didn’t get my SuperB Epsilon battery high enough to reset the SOC to 100% on the BMS. I contacted SuperB & they sent me some charging figures, Voltage/time etc. I setup a custom profile on my Victron app & used it across all 3 devices, solar/mains/B2B. Works a treat.

I’ve got my mppt on a custom profile as attached. But that’s only 14.2v.
The Renogy document above shows 14.6v to be max charge voltage so I’ll change it to that.
Won’t really do much for a few months, but I’ll check the Victron 240v charger settings tomorrow.

 

[Bigsidavies]

Just plugged in to EHU and the LiFePo profile on the Victron blue smart is also 14.2v.
I’ve changed it to 14.6 on both the solar and the 240 and I’ll see what happens.
Hopefully it will get the battery to the 13.6 max at rest.