How To: Load Test Your Prius Battery

[@sixthsense2939]

I set up the test just like yours. Found one battery which failed miserably. A dead-one in the 28 battery line-up, and it's all over for a Prius. There's no mystery with Prius batteries for me anymore, just a lot of nuts & bolts and repetition. Thanks for your video, it saved me a bundle.

[@beenegarage7116]

That's awesome, glad it was helpful! Let me know how it works once you put it all back together!

[@sixthsense2939]

@@beenegarage7116 all good. had to learn how to repack the cells vertically, then within an hour, it was back in the car and working. With good advice for folks such as yourself, Prius battery pack repair is very easy indeed.

[@rotaryperfection]

I just repaired my 2nd gen battery pack and didn't use this hi load method. I simply equalized all the batterys and then isolated them after group charging to see which ones whould drop the fastest over 24hrs. Replaced the ones that discharged and repeated the charge and self drain test. All 28 dropped similar after swapping different ones in so that's what I reinstalled in the car. So far so good after a week of driving. Now that I've seen this load testing method, I wish I would have found this video sooner. I did try previously with a digital load tester to see if that would work as an experiment to load test but it didn't so I just relied on the self drain test Now I'll have to re buy my manuel heat element tester to check the spare battery cells I have. Got lucky and bought an entire 2nd gen battery pack off auction for $75 and so far all the cells are usable. 😁 Thx for posting because this is exactly what I needed to see.

[@dunesalvador9351]

The best tutorial how to test hybrid cell.

[@shirwansalih8726]

Thank you very much I finished my battery today I found 2 cells were back and 6 more within 30 seconds were below 6.5 I change them too. Now my battery pack is amazing and gives me amazing milage.

[@jayviz]

you are so awesome for making this video I can't thank you enough. I take it you would perform this procedure prior to any charging/discharging cycles to eliminate the weak ones right off the bat? also I noticed it's been a few years since you made this video. Looking back on it, would you have done anything differently?

[@honuputters1891]

I tried to duplicate the test, but when I tried it, music did not play. What am I doing wrong?

[@monoshock57]

🤪lol

[@Madvizion]

You freak 😂😂😂

[@justinjacobsen84]

I have a question. What is the voltage threshold for determining whether a battery is still good or not when under load? Thank you for making this video!

[@RogerPack]

He basically says to compare them to their neighbors and look for outliers at 4:00 :)

[@MervsServiceSecrets]

I've seen people voicing concerns about using a method like this because of the large load, so I wonder if there is a way to introduce a rheostat into the equation as a way of "turning down" the amp draw.

[@stevepope5484]

I didn't realize they would swell while discharging? I bought this exact load tester. Instructions do not advise 30 sec. Also it's like one min.cool off between pulls. I did 20 sec. A couple of times Then 10 more secs on one module. Hope Harbor Frieght gives me a refund tomorrow. It stopped working. Doesn't read volts or anything now.

[@richarda.490]

I did this load test with a halogen headlight. The voltage drop was imperceptible- at most .o5 to .07 volts per module.

[@CuddleTrouble]

You're drawing way less amperage than he is in this test.

[@MervsServiceSecrets]

Excellent video. FYI that a-zon link is no longer active. How many amps did you draw?

[@jesusvelazquez9569]

the best test found

[@liam3444]

Where do you buy the new cells? All I am finding are refurbished.

[@stevepope5484]

I'm using an automobile headlamp bulb./volt meter. Took 20 minutes to go from 8.whatever to 7.2

[@paschinthaka1397]

Good luck sir

[@mbliu91]

Thank you that was really helpful!

[@WiSeNhEiMeR-1369]

Thanks, ... COOP ...

[@billt7207]

Is it okay to run for more than 10 seconds? I got the same tester and it says 10 seconds only but 30 seconds is okay?

[@zonykel]

The warning I saw from another video was that the heating element inside the load tester can get very hot. I think that's part of the reason for the 10-second recommendation.

[@RogerPack]

@@zonykel Where's the other vid? :)

[@malkhazkobakhidze8403]

What was the actual Amps reading on load tester while testing?

[@RogerPack]

It's basically a manual load so doesn't read amps (he's using the digital thing for monitoring voltage only).

[@richardking6066]

Googling " DIY Grid Charger" may be of interest. A low-cost way to charge and balance the entire pack, without disassembly.

[@stevepope5484]

After reconditioning. And no TRIANGLE but engine immediately starts?and goes dead after 30 seconds. Today TRIANGLE? But says ready and doesnt start.backed up under electrical power 15 feet /the engine starts?30 sec.goes off? I took a reading today on the pack Because the dash says 3 bars. The pack shows 230volts?

[@stevepope5484]

I red the ecu normally wont allow the battery to be charged past 201Volts Soooooo maybe I've done a bad thing?

[@RogerPack]

@@stevepope5484 ever figure it out?

[@lesliebrew4789]

Thank you so much. You da man!!

[@alexvargas2384]

Does it work to remove memory effect to cells?

[@cody9214]

How do you have the imax connected to the load tester and battery? What outputs are you using.

[@beenegarage7116]

I just connected the main positive and negative of the imax to the main positive and negative of the battery. Same place the load tester was hooked to. Really just using it as a fancy voltmeter. I blew up my DC wattage meter shortly before this test or I would have used that. Would’ve been more appropriate.

[@theaussienurseflipper.8113]

How many amps U charging at cheers

[@iankennedy8457]

What amperage did you charge at? How long did the charge cycle take?

[@beenegarage7116]

Is have to go back and look but I believe I was charging at 1c, so for these they would be 6 amps which would take a bit over an hour. Apparently if one charges nimh too slowly the algorithm can’t determine when the Cell is full and end up over charging.

[@iankennedy8457]

Ok. I’m a noob here. What does 1c mean?

[@beenegarage7116]

1c would be charging or discharging a battery fully in 1 hour. So a 6 amp hour battery would discharge in one hour if done at 6 amps. Therefore 1c.

[@GaryMarkowski]

I have two SkyRC iMax B6AC v2 chargers and they work pretty good. However they do not stop charging at a max voltage, so I do not trust the iMax v2 to charge/discharge in cycles. The cycle feature is useless. They work safely for charging if you watch them, and discharging works fine because you can discharge down to a set voltage. I set the manual charge to 6.0 amps (which is the max for NiMH), and it charges at a rate of about 5.2 to 5.4 amps. I set the time limit to 5 minutes and watch it very closely. Charging at a fast amp rate helps to reduce the battery memory effect. I think the Delta Voltage Drop kicks in around 8.6 or 8.7 volts, and it may be safe to charge up to 8.5 volts. I usually charge up to 8.25 to 8.30 volts. I do not know what is optimal. The iMax charger charges for 29 seconds and then pauses charging for 1 second at which time it captures the voltage, and then charges for 29 seconds, pauses for 1 second, and so on. There is no max voltage limit to set (I wish it had this feature). Since the iMax charger does not monitor the voltage every split second, it will not detect the momentary delta voltage drop of the battery, which indicates the battery is fully charged, and it should not be charged anymore. Because the SkyRC charger does not have a safe way to determine the battery is fully charged, I feel it is unsafe to charge up and discharge (in cycles). The SkyRC charger has a setting where you can discharge up to 2.0 amps, however realistically it only discharges at a rate of about 0.7 amps. If you wish to exercise the module, discharge the voltage slowly down to 6.0 volts For example, 1) Discharge battery @ 0.7 amps down to 7.0 volts. 2) Discharge battery @ 0.5 amps down to 6.7 volts. 3) Discharge battery @ 0.4 amps down to 6.5 volts. 4) Discharge battery @ 0.3 amps down to 6.0 volts. I do not recommend going lower than 6.0 volts. After discharging, allow the battery to rest for 2-4 hours or even overnight. Note: due to the battery chemistry, the voltage will drift up/down to 7.2 volts. When discharged to 6 volts, it usually will drift back up to 6.8 volts or more. To recharge, apply a 2 amp charge until the battery reaches 6.5 volts, and then apply a 6 amp charge up to 8.3 volts. Balancing the battery pack is a technique to weed out bad batteries and pair two of them together for each block. One way to test the batteries is to connect the SkyRC iMax charger to the battery. Charge it @ 6 amps up to 8.30 volts. Stop the charge and verify the voltage is close to 8.25 volts. Set the discharge rate to 2.0 amps and set the target voltage to 7.7 volts. Start discharging, and immediately connect another load to the battery terminals such as a halogen headlight (ideal). Once you hit the 7.70 volt target, the charger will stop discharging. Disconnect the headlamp. Write down, the time to discharge, and also the amps (note: the amps are based on the charger's discharge rate, and does not take into account the headlamp). You can use this information to sort the values you collect in a spreadsheet to determine which batteries are good and which ones should be replaced. As an additional step, you could charge the battery back up to 8.3 volts and write down how many amps were required to charge it back up. This would give you an idea of how many amps were actually discharged in the previous step (charger + headlamp).

[@iankennedy8457]

@@GaryMarkowski thanks! I may be doing another battery soon.

[@jayviz]

very helpful. thank you! how many amps were you using?

[@beenegarage7116]

I didn't get a direct reading but the device is supposed to pull 100 amps at 12 volts so I figure it was north of 50 amps with the lower voltage I was messing with.

[@panicosvasiliou4914]

I think that 50amps for 30 seconds for a 6500 mah battery is too much. Can we use a smaller load?

[@beenegarage7116]

I was trying to simulate what the Prius would pull. 50a is probably on the low end. These cells are rated at a high discharge rate to be able to handle depleting the battery in a single acceleration onto the highway.

[@panicosvasiliou4914]

@@beenegarage7116 I have the Dr prius app and I think it might go up to 20 Amps. But now I'm not sure. I will have to check it out tomorrow.

[@panicosvasiliou4914]

You are right. I found one screenshot where it drawed 75 Amps!!! So a weak battery, can we make them stronger if we discharge down to 6v and then recharge to 9v five times?

[@alext8828]

I have a concern about using my load tester on these battery modules. My load tester says it draws 135 amps. That sounds very high to me. Do you know what the amp draw is on your load tester? If you said it, I missed it. What would you say is a safe amp load?

[@beenegarage7116]

I think it’s a 100a draw with the tester I used.

[@alext8828]

​@@beenegarage7116 I see videos of people using light bulbs. I don't know if they're 6 or 12v. That doesn't sound like much of a load to me. I think you're in the right neighborhood. I couldn't see the name or model of your load tester but it looks familiar. Thanks for the info.

[@theaussienurseflipper.8113]

Load tester, U using 6v or 12v cheers

[@zonykel]

It's one and the same. You can just read the voltage with the needle on the meter.

[@alext8828]

Why does it play music when you put the load on it? (just kidding)

[@hiphopwong]

Seems like a 100 amp load is way too much? Most people are using a light bulb pulling around 2 amps to simulate the load on each module as it would work in the entire pack.