2 Pack 12V 15Ah LiFePO4 Deep Cycle Battery, 2000+ Cycles Rechargeable Battery for Scooter, Lighting, Power Wheels, Fish Finder and More with Built-in 16A BMS

I extended my 12v car battery with this.Despite the comments not to do it, a battery balancer costs anywhere upward of $200.So I made my own for under $10.I may be wrong in some assumptions, and am still testing my setup, and will update in the future on more actual results.In the meantime, I theorize:My lead acid car battery charges at 14.4V (11A), and discharges at 12.65V (800CCA). This battery charges at 14.4V (4A), and discharges at 13.35V (8A, 20A burst).I connected this lithium battery in series to a 100W 3ohms resistor.Then I connected the lithium battery + resistor unit to the lead acid battery in parallel.After about 60 minutes of driving, the resistor was slightly warmed up, but still less than hand temperature, and the Li battery was cold to the touch, and both batteries balanced out.The resistor was added to lower the balancing currents between both batteries, and to protect the Li battery from over charge currents.From online:A lead acid battery has an internal resistance average of 20 mOhms.A lithium battery has an internal resistance average of 100 mOhms.Assuming this information is correct, and if my charging circuit provides 10A charging current (which is on the high side), the lithium battery without resistor should charge at approx 1.6A, while the lead acid should charge at 8.666A. So a resistor may not even be necessary for active (being charged) operation.More than likely the actual charge current is lower, as the charging circuit may only provide 5 to 6A of charge current,thus lowering the lithium charge current below the nominal.With added 3 ohms resistor, the 14.4 charge voltage drops to 13.75V, as a further protection against shorts, overcharges and over discharges.The main 2 reasons I have the resistor installed is:1- High current draw protection (eg: when the battery wants to start the engine, and a voltage sag happens).2- Battery balancing when charger circuit disconnects.Number 2 is the main reason, as the 14.4V charge voltage over the lead acid battery (13.75V on the Li battery side after resistor) disconnects, and the Lead acid battery drops to its nominal 12.50V, and the lithium to its 13.5V.That's a 1V differential between both, and with only 20mOhms on resistance, the current draw of the Lithium trying to charge the Lead acid would be about 50 amps (ignoring wiring resistances, probably closer to 25A in real life), well above the max the Li can handle.With the 3 Ohms resistor, the current draw from the Li to the Lead Acid should be closer to 0.333mA. A better suited 1Ohms resistor should allow for balancing currents of 1A.The resistor isn't the most efficient way to limit current, but considering that it was a very cheap solution, IMHO it was the best solution for an average Joe.The cons of this resistor setup, is that after shutting off the car, both batteries will self balance for a time, until the 13.50V voltage of the Li battery, matches the 12.50V of the Lead acid.Consider that the car also has parasitic losses, drawing energy from the lithium battery first; and all that balancing and parasitic losses all go through the resistor which basically converts roughly 1 to 3W in heat loss....The second con, is that when the starter motor is engaged, drawing up to 200A (400A peak); and the Lead acid voltage drops to 10V, the Li battery will be taxed heavily. It can provide a max of 20A for a duration of 3 seconds.If we presume that the LeadAcid has an internal resistance of 10mOhms, and the Li+3Ohms resistor is 3100mOhms, then about 200A/3110*3100= 199.35A goes to the Lead Acid, and about 0.64A goes to the Lithium (provided both batteries leveled out to 12.50V).If the engine is started immediately after it was shut down (start-stop system at a red light), the Li still has 13.5V, making the amp rating ~0.83AThe rest of the power gets drawn from the lead acid.For that reason, I believe a 1 or 0.5 ohm resistor may be more suited for regular cars allowing higher balancing, and higher starter discharge currents.In my case however, I own a hybrid car, and the starter only gets power from the 12V battery, if the high voltage battery is depleted.So it basically never draws power from the 12v.So the Li battery is merely there to extend the life of the 12V battery, and take care of the parasitic losses of the car (sensors, remote unlock, etc...).So far it also seems to work just fine.I'll update when something goes wrong or fails.

Works fine in older Razor 24v 12" dirt bike, maybe a bit more power than original AGM. Wasn't sure if BMS would be powerful enough, but it hauled my 180lb body up a steep driveway, the motor struggled as it usually does, but the batteries didn't cut out. Also wasn't sure the original 24v charger would work, but it does. I do assume that one battery will reach 100% before the other and will cut out, leaving the other battery not fully charged, so I will periodically charge each separately. The weight difference is incredible. And hopefully won't be replacing these every other year like the original AGMs.I will likely be purchasing more for UPS's, to eliminate replacing AGM batteries! Testing the BMS while charging, I think they will work fine with a UPS, as they completely cut offline when fully charged. Not sure how much current they can actually output for a UPS though.

Lead acid battery tripped the panel as it dropped a cell or two, bought this to replace it with idea maybe it'll last a while.I did have to clip the terminals to make them fit, but had to on previous so no biggie.Battery weighs maybe 1/3-2/3 the old battery.Being it's a lithium, slight worry but risk in anything...

Long lasting power for more fun.

I put 3 of them in a 36 volt child size motorcycle. They are lighter than the original gel cell lead acid batteries. They seem to perform better, time will tell about recharge cycles. Using the original 36 volt charger.

I purchased these to compare to other LiFePO4 batteries that I have purchased on Amazon. When I received them, they were charged approximately 75% so I fully charged them and then ran a capacity test. These batteries should be 192 Wh after several recharge cycles so I was pleasantly surprised to see that the first test was 191 Wh. I tested the second battery with similar results. I fully expect these batteries to meet or exceed their specifications after a few charge/discharge cycles. I highly recommend these batteries. I will update my review if anything changes.As I stated, I have several other brands of LiFePO4 batteries, and all of them have been 5% to 10% below their rated capacity on the first test. Eventually, they are close to their rated capacities. These batteries are impressive and quite a value for their price. Definitely give them a try!

It did the same as the last two batteries. After two days of use, the batteries died, and they couldn't be charged with the charger that came with the mobility scooter.

I replaced a dead lead-acid UPS battery with this 12V 8Ah LiFePO4 battery and it fit perfectly. The UPS has been working flawlessly since the swap. While I haven't yet assessed its long-term durability, the cost is reasonable and the significantly lower weight is a definite plus.