AGM vs Golf Cart Acceptance Rate?

[Delancey]

I believe I have it correctly that Golf Cart Batteries have higher acceptance rates by design when compared to other flooded batteries. How do they compare to AGMs?

[smac999]

golf cart is a physical case size and is available in both flooded and AGM type...

I doubt a flooded golf cart has a higher acceptance then the same AH size in other group sizes.

[Sternwake]

If 6v GC batteries came with CCA figures, and if one compared them to an equal capacity of 12v Marine/dual purpose battery's CCA figures, the 6v GC-2 batteries would be the clear loser due to thicker denser plates designed for deep cycling.

Denser thicker in flooded batteries equates to higher resistance and lesser rates of charge acceptance.

CCA rates have little value in deep cycling applications, but they do correlate to charge acceptance when high amps are available and a charging source's voltage regulator is seeking to obtain at least 14.4v

How many amps does is require for a 50% depleted set of GC-2 batteries at 230Ah capacity require to reach an instant 14.8v?

I do not know personally, I will guess about 90 to 100 Amps. Actual data here would be great, and data as to how fast those amps taper at absorption voltage too.

I do know my Single group 27 Northstar AGM at 90 AH capacity when new and discharged to the 50% range, required over 106 amps to nearly instantly be brought to 14.8v, now at ~ 400 deep cycles that number is somewhere around 80 to 90 amps.

My flooded group psuedo deep cycle 31 was significantly lower than this.

Amps required to yield instant absorption voltage at battery terminals is telling, if one has a charging source large enough and also seeking mid to high 14's, and the instruments to measure, and the desire to experiment.

[sailinglegend]

Originally Posted by Sternwake

.....Amps required to yield instant absorption voltage at battery terminals is telling, if one has a charging source large enough and also seeking mid to high 14's, and the instruments to measure, and the desire to experiment.

My DC Generator put 250 amps at 14.4v into our Lifeline bank @ 50% SOC when they were new. 12 years later they were down to 55% of their original capacity at the start of the year and only accepted about 110 amps @ 50% SOC. They have lasted this season well - but we did have 1050 Ah 12 years ago!

In answer to the OP's question AGMs will accept much more current than Flooded Lead Acid batteries. Lifeline claim an "inrush current" of 500 amps for a 100Ah AGM. This will quickly fall to maybe 150 amps. So if an FLA is accepting 50 amps from a good 100 amp charge source an AGM may accept the full 100 amps in the initial boost stage of charging, so that part of the charge cycle will be faster.
 This may not be true for all AGMs - people buy the wrong sort for boats. Standby Solar or Starting AGMs that are not designed to cycle regularly to 50% SOC will fail quickly.

AGMs ARE NOT ALL MADE THE SAME!

See this thread: http://www.cruisersforum.com/forums/...ge-137059.html

[Akapeterc]

I just recently replaced my Trojan T145 plus batteries for full river AGM batteries. The Trojans were 265amp and the full river are 250amp both 6 V. The AGM batteries definitely charge a lot faster, on an average through the afternoon and night & using the inverter for breakfast, I lose about 75 Amp hours. The batteries are fully charged well before lunchtime

[a64pilot]

At nearly 50% SOC my 660 AH Lifeline bank will accept 185 amps for 30 min, then they go into absorption and will hold above 150 amps or so for another 30 min.

[ranger58sb]

Originally Posted by a64pilot

At nearly 50% SOC my 660 AH Lifeline bank will accept 185 amps for 30 min, then they go into absorption and will hold above 150 amps or so for another 30 min.

What size is your charger?

-Chris

[StuM]

Originally Posted by ranger42c

What size is your charger?

-Chris

I'd guess he's using a genset of around 3kW.

[a64pilot]

Originally Posted by ranger42c

What size is your charger?

-Chris

The Magnum puts out 125 amps and I also have a 60 amp Sterling Pro charge, combined of course they are 185 amps and they do load the Nexgen 3.5 KW pretty well.
From conversations I have had with David Goodbar at Lifeline its better for their batteries to charge them with as high an amperage as possible, plus if I'm burning the Diesel anyway, why not?
The Sterling came first and at that time I had no plans on a large inverter / charger, but the Magnum has been one of the best things I have added, so far its been flawless.

[Maine Sail]

Originally Posted by a64pilot

At nearly 50% SOC my 660 AH Lifeline bank will accept 185 amps for 30 min, then they go into absorption and will hold above 150 amps or so for another 30 min.

That is a .28C charge rate and not all that high for 660Ah. IMHO a .3C +/- charge rate is pretty optimal charge rate for Lifeline AGM's. This results in maximizing your charge current source while getting to a reasonable bulk/early absorption SOC level in a relatively short period of time.

The last 6-8% of capacity, which is still critical for state of health and needs to be attained regularly, takes the longest. The difference between a .4C charge rate to 100% and a .2C charge rate to 100% SOC only changes the time-to-full duration by about 12-15 minutes.

Here are some testing summaries using Lifeline batteries from 50% SOC and at:

.2C 50% to 100% SOC = 5:42 - Exited Bulk Charge at 1:16

.4C 50% to 100% SOC = 5:30 - Exited Bulk Charge at 19 Minutes

.2C 50% SOC Charged at .2C for 1 Hour = 71% SOC - Never Exited Bulk

.4C 50% SOC Charged at .4C for 1 Hour = 85% SOC - Exited Bulk at 20 Minutes

.2C 50% SOC Charged at .2C for 2 Hours = 87% SOC - Exited Bulk at 1:16

.4C 50% SOC Charged at .4C for 2 Hours = 96% SOC - Exited Bulk at 20 Minutes


How Fast Can AGM's Charge? (LINK)



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[a64pilot]

Reason I wanted such a large charging rate was to get as much charge into the bank as soon as possible, and then when the acceptance rate is down to where Solar can handle it, shut down the generator. I hope to be able to get to 100% SOC twice a week doing this and make water, wash clothes and whatever else I need or want to do that requires power, but goal is to only run the generator a couple times a week early in the morning.

[btrayfors]

Maximum charge acceptance for flooded golf-cart batteries is between 20 and 25% AH rating at 14.4-14.8VDC.

AGMs can accept a LOT more. At 50% SOC, an AGM battery can accept charge amperage initially of more than 100% its AH rating, and at lower SOC AGMs initially can accept as much as 500% of AH rating.

Four years ago durinig a prolonged series of battery tests, we worked together with the Concorde-Lifeline battery company and ran some controlled, measured tests on a new AGM Lifeline battery. The graphs below show actual charge acceptance rates for the first two hours at room temperature, using four different levels of charger capacity.

[ranger58sb]

Originally Posted by StuM

I'd guess he's using a genset of around 3kW.

Originally Posted by a64pilot

The Magnum puts out 125 amps and I also have a 60 amp Sterling Pro charge, combined of course they are 185 amps and they do load the Nexgen 3.5 KW pretty well.

That's what I was after; I didn't remember seeing any typical chargers advertised with amperage that high (not that I shopped extensively)... but the idea of combining chargers hadn't occurred to me.

-Chris

[smac999]

Originally Posted by ranger42c

That's what I was after; I didn't remember seeing any typical chargers advertised with amperage that high (not that I shopped extensively)... but the idea of combining chargers hadn't occurred to me.

-Chris

we often install ~200a of charging on a 40' sail boats up here. 1 hour of gen a day and 23h of inverter. ~800ah house banks.

using an inverter charger + big charger.

[ranger58sb]

Originally Posted by smac999

we often install ~200a of charging on a 40' sail boats up here. 1 hour of gen a day and 23h of inverter. ~800ah house banks.

using an inverter charger + big charger.

Thanks for idea reinforcement; really hadn't even crossed my mind it could be done that way. Partly, I guess, because I don't really have space for a single battery bank large enough to benefit all that much from a combined approach...

Useful insight.

-Chris