Lead Batteries

If you discharge completly a lead battery and then reacharge it, is it better for it and make it last longer?

 

Completely discharging any battery is generally not a good idea. Some tolerate it better than others, but it's still not a good idea.

 

nicads like that, don't do that to lead acid batteries, not good for them.

 

The SLAs I found I can get away with reducing them to 4v but no more than that. Gel Cells don't like to run flat. I can run my Yamato till it crawls. By that time after checking the voltage the batteries are down to 4v. Anything less than that and the motors just can't turn the prop when in the water under that load. A slow charge is good when you run them down that far. When battling though I wouldn't go less than 5v.

 

I was under the impression that SLA and Gel cell batteries are Lead Acid in nature. I have read that they
are designed for emergency lighting mostly. In that use they require that they "NOT" be deep cycled.
The only lead acid batteries that can be deep cycled are "deep cycle Marine". So we shouldn't cycle them
past about 5.5 volts. Storage is a issue in the winter time when the cells go below 32 deg. F they do strange
things like reversed polarity. In the past I have discharged my SLA's and charged them to see what they
have in storage capacity, useful at the beginning of the year to weed out the "bad" batteries.

But now with the newer chemistries becoming cheaper, SLA and Gels are not a good investment. They tend
to not supply the current as advertised.

 

Everything you need to know about SLA's can be found here http://batteryuniversity.com/. In particular, the Lead Acid articles under Battery Types and Charging Batteries.

Steve Tyng

 

Day two of basic math and basic electricity, another year and a half to go. I blame you for letting Rickover steal my soul... And Kotori just took the ASVAB yesterday. Don't you see the chain of misery and suffering you've caused? Repent! Repent your sins and and as penance you shall let me sink you in the few free moments I have to spare!

 

SLA's are not a bad investment. I get them cheap compared to the new batteries and the new batteries are fairly new on the market so as far as their longevity that is still open. The SLA's however do last for a long time. I have 4 that I still use and they been in Bismarck and Yamato . My last set lasted me for 10 yrs and they were used heavily.

 

Lead acid batteries lose capacity quicker than the LiFEPO4 batteries are projected to. The LiFE batteries, sitting on the shelf, only lose 3-5% of their charge per month, if you leave a Gel Cell on the shelf for 6 months you are lucky if it has any charge left at all. Gel Cells are rated for 200 cycles, the LiFE batteries are rated for 2000 cycles. The usable capacity on all batteries drops with age, the LiFE batteries are still good for 80% of the initial rated capacity at 5 years old. Gel Cells suffer significantly more capacity loss with age. We had gel cells on float chargers continuously for 5-6 years where I worked, when the power went out we found they were all dead. I would say that although your Gel Cells test OK voltage wise, if they are 10 years old they have almost none of their rated capacity left. Enough to turn a motor, but I bet the voltage coming from the battery when it was under load dropped through the floor.
Here is the battery type comparison chart from batteryspace:

Chemistry​

Voltage​

Energy Density​

Working Temp.​

Cycle Life​

Safety​

Environmental​

Cost based on cycle life x wh of SLA
LiFePO4​

3.2V​

>120 wh/kg​

-0-60 °C​

>2000(0.2C
rate, IEC Standard)
Safe​

Good​

0.15-0.25
lower than SLA
Lead acid​

2.0V​

> 35wh/kg​

-20 - 40°C ​

>200​

Safe​

Not good​

1
NiCd​

1.2V​

> 40wh/kg​

-20 - 50 °C​

>1000​

Safe​

Bad​

0.7
NiMH​

1.2V​

>80 wh/kg​

-20 - 50 °C​

>500​

Safe​

Good​

1.2-1.4
LiMnxNiyCozO2​

3.7V​

>160 wh/kg​

-20 - 40 °C​

>500​

better than LiCo​

OK​

1.5-2.0
LiCoO2​

3.7V​

>200 wh/kg​

-20 - 60 °C​

> 500​

Unsafe w/o PCM​

OK​

1.5-2.0​

Start looking at watt-hours instead of amp-hours, it gives you a much better indication about how much truly usable power you get from a battery.
Ron Hunt