The middle LED typically means about half charge, but you'd need to know what the actual voltage is that the indicator changes at, vs the discharge curve of the specific battery being used is, to know what the true state-of-charge is, for any battery where voltage is a good indicator of SoC. It's a fair bet that for your system, it is about half, so you can probably safely assume this, for new batteries. As they age this may change.
(for batteries like LiFePO4 where voltage isn't a good SoC indicator, you'd need a wattmeter to count Ah / Wh in/out to know the state of the battery at any point).
Do you have a voltmeter (or multimeter)? If so, connect it to the battery in a way that lets you be able to read it while riding, and set it to 200VDC. Red lead to battery positive, black to negative. Note down the voltage before you start riding, and then as it reaches the yellow LED. Noting where it reaches the red LED may also be useful, to know about where the system expects "shutoff" to occur. (even if it doesn't have an automatic safety shutoff to prevent battery damage)
Regarding replacing the batteries, you need to know how much current (amps, A (vs amp-hours, Ah) your system draws under max and continuous loads from the batteries, so you can be sure the new batteries can handle that load without problems. (more further down in this post about that)
Then make sure the new battery is rated for *more* A (current) (not Ah, capacity) than the system will ever draw from it. As much more as you can get, to have as little voltage drop (sag) as possible so you can get the most power (watts) out of the system. If it sags a lot in voltage under load, then the system doesn't have as much power as it could, and at low states of charge can sag enough to shutdown the system (either because of controller LVC, or because of battery BMS LVC--SLA don't have BMS, but Li of various kinds do, or should, and will turn off the output when it goes too low to help prevent battery damage that can lead to a fire).
If the Li battery has no BMS, then there is also no way to keep it balanced (individual cells can become different from each other over time, even in an SLA, but without a balancing BMS there's no simple automatic way to prevent or fix this; there are manual ways to do it if there is no balancer in the BMS or no BMS, but it can get a bit complex and is tedious).
Since SLA are typically only able to deliver about half their capacity (Ah) when used as they are in an EV, the new Li battery only *has* to have about half the capacity to give around the same range, most likely. But getting one with *more* capacity is usually better, because you get more range, and it's easier on the battery even if you don't use it all.
Is this the new battery you are looking at?
https://www.amazon.com/LiFePO4-Security-Scooters-Emergency-Lighting/dp/B08ZH77QCG
![711h2ju5SES._AC_SL1500_[1].jpg](https://endless-sphere.com/sphere/data/attachments/185/185415-5e2c3dae7b8ddff34089ed22b04c8493.jpg "711h2ju5SES._AC_SL1500_[1].jpg")
It does say it has a BMS, so it should protect itself against problems. However, sometimes there are problems with putting BMS-protected batteries in series, as one BMS turning off to protect itself puts the entire system voltage across it, and if it's FETs aren't able to handle taht, they can fail. To prevent this kind of problem, diodes can be placed in parallel with the pack, per the diagram in this thread:
if necessary.
The specs indicate only 10A continuous discharge. Is your bike like this one?
https://electricbikereview.com/ezip/trailz/
MOTOR NOMINAL OUTPUT:
450 watts
BATTERY VOLTAGE:
24 volts
BATTERY AMP HOURS:
10 ah
BATTERY WATT HOURS:
240 wh
BATTERY CHEMISTRY:
Sealed Lead Acid
CHARGE TIME:
6 hours
ESTIMATED MIN RANGE:
10 miles (16 km)
ESTIMATED MAX RANGE:
15 miles (24 km)
DISPLAY TYPE:
LED Console
READOUTS:
Battery Voltage (Full, Half, Low)
If so, the 450W motor, if it only draws that much max, would at 24v be about 450 / 24 = 18.75A, or nearly twice the continous current the new battery you list can handle. It could handle that power for a few seconds at a time (peak), but if you are riding up a hill, pulling a load, etc., that power level will be sustained longer than the battery can handle, and it may either shut off output to protect itself, or if unable to do this it may be damaged by the overload.
Parallelling at least a pair of batteries, in series with another paralleled pair, (four total) would support that load well enough. More in parallel would support it easier. But using larger versions with higher capacities and capabilities would usually be "better" than paralleling several smaller ones, assuming the cells in bigger ones are also bigger and not just more small ones in parallel in a bigger case. (there are advantages to either way, depending on usage scenario and needs).
So using this 36Ah version:
https://www.amazon.com/LiFePO4-Security-Scooters-Emergency-Lighting/dp/B09ZD94W55?th=1
would be better, in that case, as it's 40A continuous limit would directly support twice your worst case loading (assuming the system never draws more than the 450w regardless of conditions) and there are even larger versions if you need more capacity. Still need to series two of them for the 24v system, but you don't have to parallel another pair like you would with the 10Ah version.
THe solar part...to guarantee proper operation without damage, you'll need a charge controller (MPPT, etc) that supports the panel voltage range you'll be using, and either directly or is user-adjustable to the charging voltage and current that the batteries you will connect to it require.
It's possible to directly connect panels to batteries if the loaded voltage of the panel is the same as the charge voltage of the batteries, but there is nothing to limit the current draw other than panel voltage drop, and if the current is high enough it can damage the batteries.
mrobinson.cell@gmail.com said:
First anyone know if the status indicator on the mode selector/twist throttle state of battery indicator goes yellow what is the actual state of charge. Is yellow 50% or close? Trying to max the sla battery life.
Second question. I know everyone loves lithium battery. Will 2 10ah weize lifepo4 (tpli-1210ah) work for creating a 3rd battery pack for the 24v system? I want to put several of these on a small trailer and charge with solar panel.
