How many C's can forklift battery take

[Weldman]

Got a 12 85 31 forklift battery originally was 18 85 31 which is about 2010 AH and was wondering how many amps it needs to keep it happy when charging to prevent sulfation also what the max is. I know lead acid is around .5C but since this has bigger plates I assume it can take/needs more than that.

 

[sunshine_eggo]

Lead acid is NOT 0.5C. It is more typically 0.10-0.15C. Fast charge batteries are typically 0.3C below 2.3V/cell.

Sulfation can be avoided with as little as 0.05C, but you'll likely need equalization a few times a year depending on depth of discharge.

I would charge anywhere in the 100-200A range and monitor specific gravity accordingly.

Best if you can locate the specific datasheet for your battery.

 

[Weldman]

Lead acid is NOT 0.5C. It is more typically 0.10-0.15C. Fast charge batteries are typically 0.3C below 2.3V/cell.

Sulfation can be avoided with as little as 0.05C, but you'll likely need equalization a few times a year depending on depth of discharge.

I would charge anywhere in the 100-200A range and monitor specific gravity accordingly.

Best if you can locate the specific datasheet for your battery.

Thanks, I was off on the numbers I don't know where I got .5 from guess from 50 amps I push into a 440 AH I have now based on that formula. Yes little hot but I just add little more water than usual. Says full charge is 1.29 gravity but nothing on specs since it's not a top brand name. Going to run a second Midnite Classic 150SL to it pack on another 2400 watts +/-. I usually equalize once a month on current set up. Didn't know if a forklift battery could take more than 0.1C

 

[sunshine_eggo]

They typically can take more than 0.1C, but it's usually an additional charging stage. We had a charger that did about 0.3C up to 27.6V and then held at 27.6V and tapered current. Once 0.1C was hit, it marched up to 29.6V - basically a dual-absorption type of charge. It was branded as being a "fast charger."

I'd start with:

29.6V absorption (lower it if your water consumption is too high)
Tail current 40A (charge is done when the battery can't take more than 40A @ 14.8V based on 0.02C typical spec)
27.2V float (27.6V if you have trouble getting to 1.29 SG @ 29.6V)
31.2 - 32.4V equalization

Only add water to max level AFTER fully charged.
Check SG the day after adding water AFTER full charge and float for 2 hours.

If SG drops to 1.255 or cells vary by more than 0.03, run an equalization.

Equalize at 31.2-32.4V (typical range, start at 15.9 and adjust up or down as needed) until SG stops increasing OR battery hits 110°F.
If temp limit is hit, stop equalize and allow battery to cool. Equalize again tomorrow.

Increase or decrease equalization frequency as needed. Fewer and shorter equalizations are better, but I prefer shorter between those two.

Some inverters get really unhappy at >32V, so exercise caution when equalizing.

 

[Weldman]

They typically can take more than 0.1C, but it's usually an additional charging stage. We had a charger that did about 0.3C up to 27.6V and then held at 27.6V and tapered current. Once 0.1C was hit, it marched up to 29.6V - basically a dual-absorption type of charge. It was branded as being a "fast charger."

I'd start with:

29.6V absorption (lower it if your water consumption is too high)
Tail current 40A (charge is done when the battery can't take more than 40A @ 14.8V based on 0.02C typical spec)
27.2V float (27.6V if you have trouble getting to 1.29 SG @ 29.6V)
31.2 - 32.4V equalization

Only add water to max level AFTER fully charged.
Check SG the day after adding water AFTER full charge and float for 2 hours.

If SG drops to 1.255 or cells vary by more than 0.03, run an equalization.

Equalize at 31.2-32.4V (typical range, start at 15.9 and adjust up or down as needed) until SG stops increasing OR battery hits 110°F.
If temp limit is hit, stop equalize and allow battery to cool. Equalize again tomorrow.

Increase or decrease equalization frequency as needed. Fewer and shorter equalizations are better, but I prefer shorter between those two.

Some inverters get really unhappy at >32V, so exercise caution when equalizing.

Yep mine would start the audible alarm at 32V, max amps is 85 for it but will work in conjunction with CC. My CC is on max smoke settings for current battery and will do same when I get this one online. Read the part fill after full charge on the watering system which in itself won't let you overfill it. Bought a 36V to have spare cells just in case.

 

[eXodus]

Lead acid is NOT 0.5C. It is more typically 0.10-0.15C. Fast charge batteries are typically 0.3C below 2.3V/cell.

Sulfation can be avoided with as little as 0.05C, but you'll likely need equalization a few times a year depending on depth of discharge.

lead is also self limiting through resistance.

Thanks, I was off on the numbers I don't know where I got .5

The highest I've lead ever seen take in was 0.5C it's like you offer 100AH battery a 200A charger - it will not charge with 200A - it will charge with 50A. That's like the upper charging limit under perfect conditions. Usually lead is lazy and doesn't want to charge that fast.

 

[sunshine_eggo]

lead is also self limiting through resistance.

All batteries are.

The highest I've lead ever seen take in was 0.5C it's like you offer 100AH battery a 200A charger - it will not charge with 200A - it will charge with 50A. That's like the upper charging limit under perfect conditions. Usually lead is lazy and doesn't want to charge that fast.

Lead is not lazy. Lead has higher resistance than LFP, so it has a larger voltage increase for a given current in accordance with Ohm's Law, thus it hits its absorption voltage sooner and draws progressively lower current as it fills at the absorption voltage.

 

[eXodus]

All batteries are.

true, but still one of the reasons you don't need a BMS or any kind of super smart charger for a Lead battery.

I'm still a big fan of Lead batteries in stationary and applications where you need a heavy battery. (Forklift)

 

[Weldman]

Difference between a LiFePO4 and FLA out where I live at in conditions I am in is between taking care of a child or a teenager cause of weather extremes here.

 

[eXodus]

Difference between a LiFePO4 and FLA out where I live at in conditions

yeah, a LFP needs a lot of attention, doesn't like hot and cold. BMS, with tons of small wires and like to catch fire once in a while. There is a lot of parts needed to keep a LFP happy in extreme weather conditions.

While FLA couldn't care less about the climate, sure they loose capacity while cold - but since they are sooo heavy, it takes forever for the temperature to change. The high internal resistance makes them automatically warm up during charging at low temperature, so it doesn't affect FLA. High temperatures actually make them have more capacity.

Didn't know if a forklift battery could take more than 0.1C

Forklift batteries where designed to charge overnight - when workers are not around, warehouses usually run 2 shifts - so you got 8 hr.'s to recharge for a 16hr day. 8x 0.1C should get you there.

 

[Weldman]

While FLA couldn't care less about the climate, sure they loose capacity while cold - but since they are sooo heavy, it takes forever for the temperature to change. The high internal resistance makes them automatically warm up during charging at low temperature, so it doesn't affect FLA. High temperatures actually make them have more capacity.

Got down to 40 below zero Fahrenheit last winter with 60 below zero wind chill, my GC2's made it just fine outside without freezing. Granted the capacity fell through the floor but survived.

 

[Weldman]

Alright I got a question and wonder where I can find the answer for this for future references or can someone give me formula to finding the answer to this mathematical question.
Got a 18 85 31 forklift battery rated at 36V 1275 AH for 20HR so if I have taken off 6 of the 18 cells and it went down to 24V what would the amp hours be then? I came up with 2010 AH for my guesstimate.

 

[sunshine_eggo]

Enjoy this circular exercise...

36V * 1275Ah = 45,900Wh

You've removed 1/3 of the battery.

45900/3 * 2 = 30,600wh

30,600Wh / 24V = 1275Ah



Each cell has 1275Ah, so any series string of single cells will always have 1275Ah. It's the rise in voltage that increases the Wh of the battery and its total capacity.

 

[Weldman]

Enjoy this circular exercise...

36V * 1275Ah = 45,900Wh

You've removed 1/3 of the battery.

45900/3 * 2 = 30,600wh

30,600Wh / 24V = 1275Ah



Each cell has 1275Ah, so any series string of single cells will always have 1275Ah. It's the rise in voltage that increases the Wh of the battery and its total capacity.

Seems pretty basic once one writes it out, I understand it now.

 

[sunshine_eggo]

To be honest, I started the math exercise before I thought about it. I knew the math exercise would give the correct answer, but I didn't take the most direct approach first.

 

[Weldman]

To be honest, I started the math exercise before I thought about it. I knew the math exercise would give the correct answer, but I didn't take the most direct approach first.

Eh it's fine I was just missing the Wh portion of the equation. Got this thing online finally and looks like it's going to be a bit to charge it. Wanted to be sure since I was setting the battery monitor. Wait I was wrong, it's 1275 AH at 6 hr rate hehe and 2010 at 20 hr rate

 

[sunshine_eggo]

Even better.

 

[AE4KR]

Got a 18 85 31 forklift battery rated at 36V 1275 AH for 20HR so if I have taken off 6 of the 18 cells and it went down to 24V what would the amp hours be then? I came up with 2010 AH for my guesstimate.

Nope. The voltage drops, which also drops the watt-hours, but current stays the same. You'll have 24 nominal volts at 1275 amp-hours, for a capacity of about 30.6 kilowatt-hours.

Forklift batteries where designed to charge overnight - when workers are not around, warehouses usually run 2 shifts - so you got 8 hr.'s to recharge for a 16hr day. 8x 0.1C should get you there.

This is how they're marketed, but they're still subject to life reduction if charged quickly.

We tend to get spoiled by the specs for automotive starter batteries, which have a high number of very thin plates. They can be charged at 0.5C without issue. True deep cycle FLA has fewer, thicker plates.

 

[eXodus]

This is how they're marketed, but they're still subject to life reduction if charged quickl

A family member of mine works for a forklift company. They have all sorts of contracts for their livespan of batteries. With rather huge fines if a forklift isn't operating. One forklift can move a few millions worth of goods during a shift. So whatever service level they promised they have to keep.

I wouldn't say 0.1C is fast charging. And 8 hours charging is industry standard.

 

[Weldman]

Even better.

Yes and no, afraid I would need two forklift battery chargers to get true 100 plus amps in it without going to 3 phase forklift battery chargers. Have a AIM's inverter/charger claims 80 amps of charging and I only see between 20 and 30 amps, only time it gets near acclaimed numbers is when first plugged in. Also noticed all of forklift battery chargers rated for 24V on single phase claim maximum 800AH size battery in 8 hr period, that's a lot of propane for generator to burn.