Charging 12V LIFePO4 batteries from 48V Main system

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Michelle Konzack asked Aug 25, '23

Charging 12V LIFePO4 batteries from 48V Main system

Hello *,

I just got lucky and got a used Citroen Berlingo 2015 (Transporter N1, Garage Car without any rust) with a broken engine. I want to use is a working car and have not to drive faster then 50km/h, hence my 7,5kW/48V motor (IEC 132) is very well suitble for it.

The Berlingo will get 32 cells LiFePO4 3,2V/310Ah hence 51,2V/620Ah in total. The charger will be a MultiPlus-II 48/5000 for charging and also my Tools on the Farm and in the Forest.

However, the only problem I face is how to charge the car battery which will be 4 LiFePO4 cells, hence 12,8V/310Ah. This capacity should be enough to power the electricity of the car for more then 8 hours, even if I would drive at night.

Since the Orion-Tr 48/12-20 is not suitable for charging and Victron does not have SmartCharger 48/12, does anyone have an idea, how to solve this?

The only option I see currently is a separated 230V/12V SmartCharger with 20-30A, since the car battery is so big, that it is virtually impossible to get empty before the drive battery.

Thanks for your help

dc-dc charger

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Answer 1 · 2023-08-25T13:14:21Z

JohnC answered · Aug 25, 2023 at 01:14 PM

Hi @Michelle Konzack

I've used an Orion-Tr 48/12-20 for years to charge a 450Ah (was 900Ah) bank. They can be set to a flat V, which is a little trickier with Li, but should still be doable. The Remote port might be useful for switching it in.

Back in the days before the Smart Orions they were touted as chargers too. They still can..

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Answer 2 · 2023-08-26T06:10:34Z

Michelle Konzack answered · Aug 26, 2023 at 06:10 AM

I have a Orion-Tr 24/24-12 and use itvas charger fir my electric tractor and load dumper, but both use PzS and AGM batteries and it works very well.

However, LiFePO4 batteries charging this uncontrolled can cause serious problrms

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Answer 3 · 2023-08-26T08:02:33Z

seb71 answered · Aug 26, 2023 at 08:02 AM

Can you use DC-DC converters in series?

So my idea would be to use an Orion 48-24 16A (380W) as a power supply for an Smart Orion 24-12 20A (240W) as a LiFePO4 charger.

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Michelle Konzack commented · Aug 27, 2023 at 07:02 AM

Generally yes, because 24V DC are always good for me, if I have not to charge the car.

I will see, what the fun cist in total.

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