Battery Load tester

[Lazarus]

Do any of you with EV have battery load tester to check condition of batteries?

I'm wondering if it would be worth the money to know? I can tell the SLA batteries are fading on the e-bike. The range is still good it's just taking longer and longer to charge. I guess when it get to the point the range is affect I'll replace.

Do you think there would be any advantage to knowing that your batteries are x amount depleted?

Thoughts?

[MetroMPG]

Your bike is a load tester.

As long as they still meet your needs (get you to your destination), I wouldn't worry too much. It becomes a concern when you are actually getting close to fully depleting the pack by the time you get to your destination, because the individual batteries don't discharge at the same rate. Meaning it's possible you could damage one by overdischarging while the others are still permitting you to limp along.

A load tester will come in handy though if you decide to try the used batteries from the alarm company. Because you can go through a box of them and figure out which ones have the highest remaining capacities.

A simple capacity test is to wire a 12v battery to an AC inverter, and run a load on the inverter as well as an AC analog clock. The inverter will shut down when voltage drops below some threshold, and the clock will stop, giving you a useful data point to compare against other batteries using the same test.

[AndrewJ]

I tested my 12v batteries by hooking them up to a load (in my case my car, with headlights on) and started my stopwatch.
Once the clock was running, I recorded the voltage (with my DMM) every 30 seconds.
When comparing the voltages you could clearly see which batteries where good as they took longer to drop voltage, and they stabilized at a higher voltage.

I think Darin mentioned that one should use a test load that somewhat closely matches the intended load of your batteries.
Since I'm using mine to run my car's electrical system, I figured the (relatively) high draw of the high-beams would best mimic the overall draw of the cars electrical system.

[MetroMPG]

That's a good method too, Andrew. The advantage to the inverter method with the AC clock is that it doesn't require you to babysit the process.

The best load tester I've used is the pack monitor for watching individual batts while they're being used for their intended purpose. I'm talking about the LED meter added to the ForkenSwift recently.

[TomEV]

You could also use a resistive load such as a water hot pot, a heater (one without a fan) or a few incandescent light bulbs. I use a cheap heater that I converted for use as a defroster (installed a 48v fan) as it pulls about 15 amps at high heat setting.

I have used regular 100 watt light bulbs as well. Got to do something with them since the house now uses CF bulbs...

But I haven't had a need to load test the batteries in a while - I just check the miles traveled vs the amp hours used to charge the pack.