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Expedient charging-LiFePO4

Bluedog225

Texas
Joined
Nov 18, 2019
Messages
2,825
Good morning,

I‘ve got a 12 volt battle born. Unknown state of charge. It was on my victron charge controller sitting up at the cabin. I imagine it’s full.

I brought it home for the summer to avoid the 107 F.

I want to use it to power a little 12 volt water pump so I can water my pecan trees up at the place from the pond. About 300’ of hose.

The question is, can I bulk charge the battle born using a dumb 12 volt battery charger? I don’t mind baby sitting it. And I don’t need “full” charge.

I just need to put some energy into the battery so I can go pump 50-100 gallons of water every other weekend.

Or do I need to but [edit-buy[ a new LiFePO4 charger to keep these battle borns healthy.

Carrying water in buckets is getting old!

Many thanks!
 
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Yes you can bulk charge it. Do you have a way to monitor the current that is going into the battery? The current should max on on a small 12v charger. When the current starts dropping below the max, it is getting closer to being charged. For example, a 5 amp charger should peg out at 5 amps, then later drop off more and more. When it gets to 2 amps (for example) it will be largely charged. ALSO, if you can monitor the amps over time, say 5 amps for 3 hours, that is about 15 amp hours you have added to the battery. If you can also monitor the amps pulled by the pump, you can keep track of what you take out and what you put in. A clamp on DC amp meter is great for such work.
 
A dumb FLA charger will likely max at 13.8v or so. Not enough to get the LFP to full charge but good for what you need. I don't charge my LFP batteries to the full 14.2V with my solar setup on TH RV
 
Yeah. One day. This is just to get me through the summer.

I’ve got a tiny (1 amp) 12 volt charger that is putting out 14.2. Seem safe per the battle born charging recs.
 
Many dumb car battery chargers will charge way above 14.6 volts. However the BMS will protect the battery.
I suggest keeping a watch on the charge process and disconnecting if the volts rise over 14 volts.

Mike
 
Got it. Showing 0.8 amps inbound and a charging voltage of 13.31.

I’ll set the time and keep track of it every couple of hours for the day and see where it goes.
 
Got it. Showing 0.8 amps inbound and a charging voltage of 13.31.

I’ll set the time and keep track of it every couple of hours for the day and see where it goes.
14.0v would be 3.5v per cell and at that charge rate would be almost fully charged.
 
Dang. That was quick. Jumped to 17 volts around 0 amps in 1.5 hours.

Pulled the charger pdq. Resting at 13.6 (full).

Don‘t understand NOCO. Maybe the charger?
 
Dang. That was quick. Jumped to 17 volts around 0 amps in 1.5 hours.

Pulled the charger pdq. Resting at 13.6 (full).

Don‘t understand NOCO. Maybe the charger?
Hope that was 0.0 amps @ 17volts. Wonder if the BMS went open and the charger was open circuit voltage.
 
The charger (a little 1 amp 12 volt deal) was around 14.2 volts. Not sure how I got 17 volts. That was measured at the terminals with the charger on and hooked up. Took it off quickly.
 
Told you that would happen. The low cost battery chargers have no voltage regulation to speak of.
The BMS will have switched off the charge path so no harm done.

Mike
 
I charge LiFePO4 with a lead acid charger all of the time. Zero issues. The batt won't reach 100%. But it will replace the charge to run your pump
 
I am curious, when it when up to 17 volts, 0 ish amps. Was that an indication of full (ish) or not?

Or does the voltage run away before being full? I thought it only increase as amps absorbed decreased.

Thanks!
 
A 12V lifepo4 battery will shut down before reaching 17V.
If some or all cells are in over-volt the bms will terminate charging.
 
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