The demise of our lead-acid AGM battery and it's replacement with a 120Ah Lithium. Mean I needed to re-think the camper trailer battery charging system.
The original system consisted of a Projecta IntelliCharge IDC25 DC to DC 25 Amp battery charger which also had an integral solar MPPT controller. The Projecta manual states it can only be used with GEL, AGM, Calcium and Wet lead-acid batteries. Not Lithium.
The 240V battery charger is a CTek MSX15 rated at 12V 15Amp. It is not designed for Lithium batteries and has modes 'Normal, Supply & Recondition'.
Online sources vary but a common consensus appears to be that a 12V Lithium-ion battery charging voltage during the Bulk stage should be 14-2 - 14.6V. Lithium has a relatively brief Absorption stage with a Voltage of 13.6V.
Lithium doesn't require a Float stage.
Under no circumstances should a Lithium battery be placed on a Reconditioning stage where the voltage rises to 15.2 - 16V. This could severely damage the battery.
Projecta
The Projecta website states "our IDC25 can only be used to recharge lead acid batteries". However when I looked at the charger manual I noticed the AGM charging option has a Bulk Voltage of 14.4V and an Absorption Voltage of 13.7V. The AGM mode does not have a Reconditioning stage. It appears the Projecta can be used to recharge a Lithium battery using the AGM mode.
After more research I found this website which included the following statement in their Technical Update
The nominal charge voltage for an AGM battery is 14.1-14.4V, which means that using a lead acid battery charger set to use the AGM setting will work correctly in most cases. A good example of this is the Projecta IntelliCharge series. These chargers have a maximum charge voltage of 14.4V for AGM and will charge a 12V lithium battery without issue.
So despite Projecta stating their Lithium specific charge must be used, it appears their lead-acid charger will work in the AGM mode.
Ctek
Looking at the CTek charging program suggested it might also be able to be used to charge Lithium using the "Normal" mode
The CTek has 8 stages in 'Normal Mode'
Desulphation 14.4V
Soft Start 15A until 12.6V
Bulk 14.4V
Absorption 14.4V
Analyse checks to see if Voltage below 12V
Recondition not used
Float 13.6V
Pulse 12.9 - 14.4V
At no stage does the Voltage exceed 14.4V. The reconditioning stage isn't used and the 'Float stage is 13.6V which is the same as the Lithium Absorption stage.
It appears the Ctek can be used to recharge a 12V Lithium battery if the 'Normal' mode is used.
Another interesting fact about Lithium batteries that I have identified from the use of my e-bike is that Lithium batteries should not be left fully charged if not going to be used. Lithium batteries are transported at a maximum of 30% charged. When I returned from my last outback trip the vehicle DC-DC charger had fully charged the battery by the time I arrived home after driving 11 hours. I ran the 12V oven for two hours and reduced the battery state of charge to 70%. I need to reduce it even further.
This raised another consideration. If the battery is at 40Ah (30%) and I load the fridge-freezer the night before a trip then the 40Ah might be used overnight prior to departure (5A load x 8 hours = 40). Moreover a 25A DC-DC charger will take a minimum of five hours to recharge the battery without a load. However if I plugged the CTek mains charger into the trailer the day prior then it could theoretically supply 140Ah (15A x 8 hrs = 120Ah).
Do I risk using non Lithium chargers on our new Lithium battery?
3 comments :
Hi Tom
On Oleanna the Victron inverter/charger is programmed so that the absorbsion phase kicks in at 28.4v and lasts the minimum time Victron allow which is one hour. The float voltage is set at 26.5v (24v system). All this is when we are hooked up. When we are out and about the alternator just charges the the batteries with no fancy "alternator to battery" stuff. The lead acid bow thruster batteries are wired in paralell with the Lifep04 bank via a relay which is activated when the ignition key is turned. So if the BMS turns off the lithium batteries when they are full the alternator is happy 'cos the lead acids are still there. It all seems to work ok. The batteries are now five years old and still going strong.
Mick
Mick the system on Waiouru also didn't have a DC-DC Charger. The output from the large alternator was more than capable of supplying the batteries. I assume Oleanna is the same? Trying to recharge the batteries with a standard car alternator might be a different story.
Hi Tom
Yes, Oleanna has a big chunky 24v 100 amp alternator that has no problem charging the lithium leisure bank. When Oleanna was new the Victron inverter/charger didn't have a specific lithium setting but we used the AGM setting and adjusted the voltage settings as in my previous comment. Victron have since then updated the firmware to include lithium batteries but I've left the voltages as before. I can do you a screen shot of default lihtium settings if you want?
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