| Electronics > Beginners |
| AGM VRLA Batteries and Constant-Voltage charging. |
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| CJay:
--- Quote from: BradC on August 15, 2018, 07:03:20 am ---As soon as it hits 13.8V you switch to constant voltage mode until the current drops to sfa. --- End quote --- SFA being what as a percentage of max charge current? --- Quote from: BradC on August 15, 2018, 07:03:20 am ---I use a cheap CC/CV bench supply to charge lead acids all the time. Set the current limit at whatever the maximum charge current is, and set the voltage limit to the absorption voltage. The battery will sit on the current limit until it hits the crossover point, where the voltage will the remain constant as the current drops away. You can do the same thing with Lithium chemistry, it's just less forgiving of errors. --- End quote --- That's my SLA charge methodology too but with a rather expensive bench PSU, I will occasionally 'spike' a battery with a higher voltage if it refuses to take a charge. |
| Lightages:
AGM batteries should be charged at a rate of a minimum of 5% of their rated current until they reach their asorbtion voltage, 14.4v nominally. Then the voltage should be held at that voltage until the current drops to less than 2% of the rated current. You should also limit the time spent in asorbtion to somewhere around 2 hours even if the current doesn't drop. Once that occurs the voltage should be dropped to the float voltage, somewhere around 13.6v. The actual voltages and times should be taken from the manufacturer's specifications. This is my experience after running and installing solar energy systems for over 8 years. |
| metrologist:
paulca, did you consider a lithium battery, given your use profile? I think I will try one of those to save some weight next time, but I ride just about every day. |
| Lightages:
I should have also said that the manufacturer will or should specify the maximum charge current. |
| paulca:
What I couldn't understand was how "Constant Potential" differed from CC/CV charging. It seems that constant potential IS CC/CV as opposed to constant current charging which is more like a NiCAD/NiMh charger which pumps a fixed current at whatever voltage the battery will take until you stop it. Consider chargers for cordless drills with NiCAD packs. The instructions are to plug it in and leave it for 10-16 hours. The charger pumps 250mA into the battery constantly, allowing the voltage to rise to a point the pack starts to put out 250mA of heat and charge no more. This is fine, even to leave it charging over a weekend. Not fine for lead acids, especially AGMs. Doesn't need said, but highly dangerous with Lithium. |
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