Battery Longevity

Then it’s the voltage sag

How you mean?

Depending on battery, brand, c rating, temp and other stuff … voltage sag will trip your voltage cut off… but when I come off throttle the voltage comes back up…

I’d try a higher c rated battery in your case

Right, I see. Thanks :thumbsup:

That would explain why going down the slight hill on my way back to the car at the end of the ride it almost seemed like it gained some guts again?

Running 9s (recommended with your setup) voltage cut-offs should be:

3.6 x 9 = 32.4v cutoff - may be able to do a little less than 3.6 but I’m not as familiar with Lipos as Li-ion.

If your batteries are puffy they are likely dying/dead. Probably from over-discharge if you were draining 9s batteries to 22v!

If you have a balance charger then just full charge one 3s pack at a time, and fully discharge it on the charger to measure your amp hours. These things are like $25-30 on ebay.

Secondly, if you have a VESC and a BLE module you can run ackamaniac’s app and see how many watt hours you are actually consuming and compare that to the batteries specs.

Lastly, voltage will drop when under load, and slowly rise again once left alone for a bit. But around 3.6v (32.4v for 9s) for lipo is basically dead.

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That’s the regen giving you a bump

Ah of course!

its all about the Watts and thats calculated Volts * Amps = Watt. if you just put them in paralel, the watts would stay the same 36v * 5A = 180Watts 12v * 15A = 180 Watts

btw, im running a 9S 5000mah set as well and i reach something about 18-20km (~10 miles)

OK I see. So how would I go about getting more miles?

technicaly only by increasing the watts. which means adding more cells. since you are using lipos anyway, you could just go for 12S which will give you 1/3 more range or add 3 more 3s 5000mah battery in paralel which will double your range

it also depends heavily on how you are driving. if you are accelerating often and hard, your battery wont last long. accelerating takes lots of juice. jsut cruising along is what gives you range.

edit: new lipos need to be “burned” in by the way. that basicly means charging and discharging them 2 or 3 times before using them. if you jsut charge them and them start hammering them, yourt chance of killign them is rather high.

Thanks for that.

To be honest, today, although I was stop starting quite a bit because I was filming, I mostly cruised and only tried out top end once for a few seconds…

I was mostly at half throttle for at least 4 of my 5 miles

well you should get at least 8-9 miles with a 9S setup. i get like 10miles with only 80% charged batterys (missing a charger with the right amount so 80% is all i get :smiley: ) what motor and gear ratio are you using???

since your battery are puffy already, i realy recommend getting rid of them and buying new ones. the borderline minimum charge for lipos shouldnt be lower then 3.2Volts per cell. on a 9S setup thats a minimum voltage of 28.8V. so if you realy downed them to 22V allready, your probably killed your pack anyway

It’s possible I killed them with my last ESC as it didn’t have cut off protection etc.

I’ll look in to getting some new batteries, I’m thinking of going for Li-ion this time though with a BMS. What configuration would you recommend to get me around 10 miles of range?

My pinion is 10T and the sprocket is 30T (it’s a chain drive).

dont underestimate li-ions ^^ if you want to do it right, then you need something like a 10s4p build (4 packs of 10 batteries) which cost allready ~200€ not counting in a BMS. that would be at least 50€ extra. and li-ions dont come prebuild which means you have to build everything on your own. and you want that to be at least 3 packs because li-ions are nowhere near the discharge rate of a li-po pack. 1 single 1s 25c 5000mah lipo pack can deliver 125Amps while a single li-ion battery delivers 10c tops. thats 25-30 amps.

Yeah I’m thinking of using Samsung 30q 3000mah.

I was thinking of making an 8s4p pack. Would that be OK?

thats up to you. id probably go for a 10s at least.

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Yeah but why’s that? What would the difference be? Range or speed, or both?

Yo!! Listen to @jaykup!!! If you have been draining them to 22.2V this is VERY bad for them and explains the puffiness as well as loss of capacity! Please dispose of them safely, do some research on safety with lithium batteries, and buy a Lithium ion battery

Err, I have been listening to everyone… I’m not 100% sure if I have in fact been draining them too low but two of the three packs are a bit ‘puffy’.

I’m thinking about replacing them with Li-ion. As you can see. From my posts above.

I’m trying to ascertain which would be the best configuration for me for cost and range . . . which you’d know . . . if you read my posts . . .

So I just ‘disposed’ of two Zippy 8000 mAh Lipos. Youtube has a lot of examples of disposing. I created a discharge circuit with a 12v lightbulb. If you are getting rid of them, hook up the light bulb and place it somewhere safe until the light is no linger lit. Use a voltmeter and make sure the battery shows under 1v. At this point, it is safe to dispose.

If you haven’t worked with Lipos before, you should know that they can become unstable when abused (ie over/under/load charge). A damaged pack can become a roman candle quick! And it can take a while before the chemical reaction turns into flames. They should be removed and stored in a fireproof container when not in use.

Now, with that said, I am moving to Li-ion batteries. They are more expensive and @Achmed20 is counting the costs in building a pack. My 8s1P (2 x 8000 mAh 4s1p Zippy’s) would get me about 12 miles. I have a 6374 motor (I think. I’m at work). An 8s4p pack of 3000 mAh will give you 12,000 mAh, or about 18 miles if you are using a similar motor and gear ratio as I am. If I have found the correct reference for the battery you wish to use, it is a continuous 15 amps. Across 4 packs that’s 60 amps. Your Lipos were more like 125 amps. Your torque will drop (acceleration) but it will be doable.