12v 7ah batteries barely giving me a mile per charge

[cody196]

Do you know much about rc lipo batteries ? You may want to save you money for a longer lasting safer battery solution. More plug and play and not a battery charging hobby with a BBQ or fireplace to charge.

yeah i have some saved but i just dont have a job to make the kind of money right now to get it. Im only like 17 turning 18 next may. But as for the de-sulfation i believe i seen some special kind of chargwers on ebay before that mentioned de-sulfators, would that work?

 

[Voltron]

Most of the desulphation strategies or adding things is for flooded lead acid with removable caps. With SLA there isn't much to be done to revive them.

 

[amberwolf]

But as for the de-sulfation i believe i seen some special kind of chargwers on ebay before that mentioned de-sulfators, would that work?

If you look around old stuff from a few years back, you'll find various threads discussing de-sulfation and other fixes of SLA, that might help you start your experiments.

 

[cody196]

so here is the latest video of my ebike on 72v, doesnt last very long does it. https://www.facebook.com/cody.wherry99/videos/608817455974807/

 

[wesnewell]

would refilling batteries with like epsom salts help restore its life since they arent too old.

If you left them uncharged over night a couple of times, or even once, you seriously damaged them. If you've got a 12V charger with a desulphate mode, you might get something back. I've resurected a few using the 24hour recondition mode of my charger, but it's hardly worth the effort. I leave my charger hooked up to my lawn tractor battery all the time 24/7 to keep it from going dead. Been doing that for a couple of years and the battery still won't hold a charge long. But it's enough to start it when I need to mow. Lead sucks.

 

[cody196]

would refilling batteries with like epsom salts help restore its life since they arent too old.

If you left them uncharged over night a couple of times, or even once, you seriously damaged them. If you've got a 12V charger with a desulphate mode, you might get something back. I've resurected a few using the 24hour recondition mode of my charger, but it's hardly worth the effort. I leave my charger hooked up to my lawn tractor battery all the time 24/7 to keep it from going dead. Been doing that for a couple of years and the battery still won't hold a charge long. But it's enough to start it when I need to mow. Lead sucks.

would those AGM deep cycle ones work longer than some cheap firststar or powerstar SLA's? if i take care of them properly

 

[Ykick]

 

[999zip999]

Cody where do you live ?
Ykick there lead batteries are dead again and can't start the Enterprise. The Enterprise now uses titanium lithium batteries. 30,000 cycles 80% capacity

 

[dogman dan]

Lead is only going to last for you if you ride less than 15 mph,, and for about 5 miles per charge.

Better cells will help,, but have you priced really good EV rated lead bricks? They cost more than lithium per usable ah. Your 7 ah cells only have about 4 ah usable. take em deeper, and you kill em,, as you did.

If you get more lead,, please get a cheap watt meter, so you can know when to stop, when you have discharged 3-4 ah.

 

[rguy56]

I do 16S cell count voltage and I like it. I’ve been using the Turnigy 20C 4S 5Ah hardcase. MultiStars don’t have quite the C rate and I prefer the form factor and added protection of the hardcase. Another advantage is that the hardcase come with 4mm bullet connectors which makes it much easier to series connect into one pack. I have yet to figure out how to series XT60 connectors without fabricating extra dongles?

Here's a nice little 16S pack made from 4S hardcase:

JST extension cables can be quite handy for breaking out the cell channels.

I know that hobbyking sells series connectors in xt90s, and xt90 to xt60 adapters, for what it's worth...

 

[Recumbent Bicycle Source]

I'm too tired to read all the discussion. But here is something to think about for those still without a budget to get Lithum.

When I first started I purchased 3 Powersonic 14AH Lead Acid Batteries... about 30lbs worth. I rode maybe 30 times with them about 20 miles max with pedaling... nearly all flat ground. I spent about $130 for them.

I was able to get about 6AH usable power and did not work them hard.

Lithium is King obviously.

I still have them... use them as back up to power little things in my RV.

 

[DrkAngel]

It's difficult to get your mind wrapped around the inadequacy of SLA in modern applications.

This single post really helps - LiPo vs SLA

.

 

[999zip999]

DrAngle that graph feels like my experience with SLA. My first ebike SLA build made me cry.

 

[cody196]

so lipo packs like multistar will have deeper discharge rates or meaning it will last longer per charge and more cycles before its life is over? Can anyone compare the differences between LiPo's, Lithium Laptop Cells, and SLA's?

 

[Voltron]

Not sure if you get the C rate thing yet.. its a measure of how fast you're moving the electricity in and out of the battery pack. So for a 10ah pack, if you pull 10 amps out of it continuously, that is 1c, and the same for charging at that rate. 20ah at 20amps draw, same 1c rate. That is about what a regular lead battery can withstand. So to sustain say a 30amp draw, you would need a 30ah pack, or you're going to be working it too hard for long life. With many lipos, they have a 30 or 40 c rating. so for a 30 amp draw, you would only need a 1 amp hour pack, if you go by the rating, but maybe you don't even want that c rate for long life. It would be silly to have a pack that small of course, so your normal size lipo pack can handle hundreds of amps at peak without damage.

So its not that a lipo will run longer or discharge deeper, an amp hour is an amp hour, but you can put a massive amp draw on a smaller pack. But if you're hitting a lead battery with a 2 or 3c amp draw, it will maybe only deliver half of the rated amp hours, and it will die an early death.

 

[DrkAngel]

.
...No ... not even close!

10Ah SLA battery at .5C (5A discharge) will only supply 5Ah usable output
10Ah SLA battery at 1C (10A discharge) will only supply 3Ah usable output
10Ah SLA battery at 2C (20A discharge) will only supply 2.2Ah usable output
10Ah SLA battery at 3C (30A discharge) will only supply 1.8Ah usable output
10Ah SLA battery at 5C (50A discharge) will only supply 1.4Ah usable output

 

[DrkAngel]

40mph requires 2250w motor output.
80% efficiency means 2800w from battery.
2800w / 72V = 39A draw from 7Ah batteries!
5.57C discharge rate from 7 Ah SLA means <1Ah - usable
and rapid destruction!

Sorry, bad math - Corrected now
2Ah LiPo at 20C would perform better and last longer!
But splurge, go 5Ah +

Be aware, above statistics are for full throttle at ~40mph.

 

[cody196]

alright thanks for the info, how much miloes could i get with a 10c 5.2ah lio pack per charge at full throttle most of the time.

 

[DrkAngel]

72V x 5.2Ah = 374wh
374wh / 2800w = .13hours @40mph (if optimally geared for 40mph)
40mph x .13hours = 5.2miles @ 40mph
≤4 miles = more realistic

Might I point out alternatively:
10mph = 36 miles range
15mph = 23 miles range
20mph = 15.5 miles range
25mph = 10 miles range
30mph = 6.25 miles range
(lower, more realistic, efficiency scale used))