BigBattery 48v HSKY Discouraging News
 

I just had a chat with the BB tech dept.
I was curious that my battery only charges to an absolute max of 54.6v, and that doesn't last long after beginning operation...
The resting voltage drops to 53.2v VERY quickly.
But, resting voltage will read that for many, many days after that.....
Seems like I always am greeted with a readout of 53.0 on the dash gauge, which is always .2v lower than the readout on the battery....
I was told that 53.2 represents a 99% of max charge.....
I was instructed to run the battery down to low voltage cutoff then recharge.
Do this several times to increase capacity...
However, once the LV cutoff point is reached, I would be dead in the water and have to tow to the shop. Not crazy about that........
Then he said to take it to 20% rather than LV cutoff........

I then inquired as to the state of the Blue tooth app for the BMC. First I got blah, blah, but then was told that, if my IOS device didn't recognize the BMS on BT, IT NEVER WOULD................... So...................
I guess I just have to stay in the dark and drive it.

Not to say that I am unhappy with the HSKY, just disappointed that I was not more informed when I purchased it.

Y'ALL BE ADVISED !!!

Re: BigBattery 48v HSKY Discouraging News
 

Ronno, I really think that 53.2 resting voltage is what you want to extend the life of your pack. I think you are fine.

53.12 volts is 3.32 volts per cell which is excellent. It may only be 90% SOC but your battery monitor and shunt will configure this as 100%. If you can't get 50 miles with your pack on level pavement, I'll give you a refund....well forget that part.

In the woods where you roam, 50 miles could never be achieved but you are in excellent operating condition anyway. When you get down to a minimum of 51.5 volts, which will be around 20% SOC, recharge it. If I were you, I would recharge when you hit 50% charge. Two 50% charges equals one life cycle.

As far as the bluetooth apps, I don't have that feature and don't even want it. The dash gauges are all I need to see where I am at. As long as my BMS does its thing, I'm happy.

Have I told you I really like my Eco Battery yet?

Re: BigBattery 48v HSKY Discouraging News
 

Does it have to be driven? I mean what if you turn on the lights or create load other ways?

Re: BigBattery 48v HSKY Discouraging News
 

I have not as yet installed my voltage reducer.......
But, that is a thought.
Lights are the only accessory on the cart.

Re: BigBattery 48v HSKY Discouraging News
 

Your batteries sound just fine to me.

Re: BigBattery 48v HSKY Discouraging News
 

Mine charges to 54.6 with a Lester Summit II charger. It seems okay to me, I drove my cart on a 20 mile run last week. I think it could have gone another 10 miles or more.

Re: BigBattery 48v HSKY Discouraging News
 

I think you’re good also. I’ve got allied 60aH and it comes to rest around 54.5-54.7v after a full charge. I’ve been told by allied a resting voltage of 51.2 is “dead”. I’ve never run them that low; I’ve gotten 30+ miles on a charge and it rest at 51.6ish IIRC. I usually recharge around 52v range.

I had to send about 15 emails back and forth with allied before I was able to get any specs from them re low and high voltage cutoff, temp operation, etc. I had to ask very specific questions to get specific answers (and even then, they satisfied what I was looking for but still what I would define as “specifically vague” answers…)

Re: BigBattery 48v HSKY Discouraging News
 

Hmmmm, the chart indicates that 53v is about 75%......
BB said that 53v is 99%
That is quite a discrepancy IMO

Re: BigBattery 48v HSKY Discouraging News
 

Predicting SOC via voltage is highly inaccurate with LiFePO4.

Re: BigBattery 48v HSKY Discouraging News
 

I've noticed this and have thrown out all my SOC charts. I made a 29.25 mile run today as a test with my 72 Ah battery:

Ending SOC on meter 39.4%

Ending Volts on meter 52.31

Ending Ah on meter 28.4

The voltage according to my charts was around 55%SOC. Could that possibly be correct and my SOC meter incorrect? I think as you said the voltage is not a good indication of SOC.

Then what is correct in these three readings?

Re: BigBattery 48v HSKY Discouraging News
 

BB is correct. That is about 3.31 volts per cell which would be 90+ % depending on the decimal amount.

I think all of the charts for lifepo4 are incorrect. Especially the ones I made!!!:oops:

Maybe? The charts I made said 100% but this is actually 80% or 53.2 volts. My meter is calibrated to show the resting voltage as 100%. Maybe that is the discrepancy.

Re: BigBattery 48v HSKY Discouraging News
 

Given the voltage variation with temperature and cycle history, trying to measure SOC by voltage is not very useful with lifepo4 batteries. You need to count electrons.

Re: BigBattery 48v HSKY Discouraging News
 

Tough to do for sure. Would you say it is more accurate to measure SOC by remaining Ah instead of voltage? It appears to be fairly consistent in my mileage log. Voltage has been all over the place but SOC and Ah are more predictable.

I rode 29.25 miles today and had ending Ah of 28.4. So I used 43.6 Ah which approximates to 1.49 Ah per mile. This has been pretty consistent in 10 logged rides of over 8 miles. 1.42 to 1.60.

Variations may be due to average speed. Faster average speeds seem to have used more Ah per mile. Temperature has been between 65 and 90 however which may throw everything off.

Re: BigBattery 48v HSKY Discouraging News
 

Measuring Amp Hours (counting electrons) is the only way I know to get a reasonable measure of SOC with these cells. A good BMS will do that for you but it isn't easy with the wildly fluctuating current in a golf cart while driving. It's easy when charging to measure how much you put in but you really need to know how much is left while driving.

Re: BigBattery 48v HSKY Discouraging News
 

Hi Tom,

Forget the voltage. 39.4% of 72Ah is equal to 28.4Ah, so both these numbers (39.4% or 28.4Ah) are what I would be going with.

As Volt_Ampare implied, your SOC meter counts electrons, go with that.

Cheers
Pat.

Re: BigBattery 48v HSKY Discouraging News
 

Thanks Pat and V_A!

As usual, you start helping someone else with their problem and end up helping me!

I think it is starting to sink in now.:thumbup:

Tom

And this is my new charging chart:

Re: BigBattery 48v HSKY Discouraging News
 

No voltages Tom……I like it. :lol::thumbup:

Re: BigBattery 48v HSKY Discouraging News
 

Thanks, Pat! Gosh, this makes it so much easier.:thumbup:

Re: BigBattery 48v HSKY Discouraging News
 

My cart only needed a 48Ah recharge after the 20 mile run it did last weekend. I only recharged it today too. I think it could probably go 40 miles on a full charge.

Re: BigBattery 48v HSKY Discouraging News
 

That is 2.4 Ah per mile. With 82.4 usable Ah down to 20% SOC (105Ah minus 20% = 82.4), you should see 34 miles. If you take it down to 5% SOC you would see 41.6 miles, although I don't like running it that low. Close to home, no problem.

I am getting a mile every 1.48Ah. You apparently have more Ah consumption due to the larger tires and higher speed.

I recommend keeping a log of any ride over 5 miles. This will give you a good indication of what to expect in future rides. I charge after any ride of 5 miles or longer. That's about a 10% DOD. Ten of these charges would equal one life cycle.

I'm glad your cart is working great for you. I know you're as glad as I am about going to lithium.:thumbup:

Re: BigBattery 48v HSKY Discouraging News
 

That's quite a difference in energy draw between our two carts. I want to run an AC motor eventually to give my cart a bit more range.

I use a tracking device to keep trip logs. I would highly recommend one to anyone interested. They'll tell you how far you go and they have good security features. Mine is made by Optimus, but there are many that do the same things mine does.

Re: BigBattery 48v HSKY Discouraging News
 

Never thought about trip tracking devices. I'll need to look into those. Thanks!