Lifeline vs. Trojan Charging speed

[zboss]

Hi folks,

How much more quickly do Lifeline AGM's charge vs. Trojan Flooded given a XXX watt solar panel outputting full (meaning lab optimized conditions) wattage?

[colemj]

Assuming that XXX is less than 1C, Mainesail posted data on another thread showing that AGM's reach absorption voltage at the same time as FLA's. It then becomes a question of how much time is needed at that voltage to reach full charge for each.

I contend that that time difference between the two is inconsequential in practice. Others have strong opposite beliefs.

The real answer to your question, however, is that neither will reach full charge unless that is a whopping big solar panel, or they both start out close to full charge.

Mark

[djmarchand]

Well, "conventional wisdom" says you shouldn't charge FLAs at more than .25C but it is ok to charge AGMs at .5C, maybe more. So assuming that you have enough solar panel wattage (a big assumption) then AGMs will charge faster at least for some of the charging cycle.

If two battery systems, one FLA and the other AGM, both start charging at .5C and the two are charged by sources that can supply .25C and .5C respectively then the AGM will definitely start out faster. But as the state of charge builds up the difference will narrow. At .75C I suspect it will be the same charge rate for both batteries, maybe .1 or .2C.

So AGMs charge faster but not as much as you would think.

David

[zboss]

This is pretty much what I thought. We have 520 amp hours of trojan t-145's with 527 watts of solar and a wind generator. We use between 75 and 110 amps during the night (define as when the amps going in moved from positive to negative and the back again) and it usually takes us till about 3 or 4 PM (on bright sunny days) to get back to zero consumed.

I hear folks say they are full at noon (consuming same amp hours) with solar half my watts and no wind generator so I have to wonder... is it truly an AGM vs. flooded difference?

[smac999]

you not going to notice a difference with a solar panel. (well maybe at 2000+ watts)

hook up a 200a charger and you'll notice the difference.

you don't use amps. you use amp hours.

[zboss]

Originally Posted by smac999

you not going to notice a difference with a solar panel. (well maybe at 2000+ watts)

hook up a 200a charger and you'll notice the difference.

you don't use amps. you use amp hours.

We also have a 175 amp alternator and wind generator but this wasn't so much a question of my particular setup, rather a question of the virtues of AGMs. If AGMs don't really charge faster on-the-hook in low amp situations (solar/wind) then there its pretty much a wash between AGM and Flooded in that configuration.

If we had a generator pushing a 200 amp alternator then maybe AGMs would be better. If we are in a slip and plugged in, then it makes no difference unless you are not spending the night.

[sailorboy1]

it seems the real question you should find out is how many amps your panels are really producing, if they are at their max what difference would AGM higher acceptance make?

[Maine Sail]

The only way to really test charge efficiency or Coulombic efficiency is to discharge known Ah's at the 20 hour rate then use a device that can "over count" (not reset to 100% when full) Ah's returned. When you get back to your "net accepted current at absorption voltage" which you deem the bank "full" at the bank is now "full". How many Ah's out to back in did that take?

Charge at 14.4V to 0.5% acceptance (Lifeline) and stop charging

Now draw out 50% at the 20 hour rate and 75-80F

Now recharge and count how may Ah's it took to get back to 0.5% acceptance at 14.4V.

When new the Coulombic efficiency will be different than when aged.

Keep in mind that with large banks and small arrays you will not even hit absorption voltage until well into the mid to high 90% range dependent upon available current.

[sailinglegend]

Coulombic efficiency, or charge efficiency is the answer to the OP's question, but it is a subject not often explained or understood. Maine Sail is the only person I know who would TRY and measure it!!!!

Battery Charge efficiency is different to Charge Acceptance Rate.

Charge Acceptance Rate is the amount of current that a battery will accept at a given voltage and given state of charge. AGMs will accept much more than Trojans or any other FLA. So if a Trojan is accepting 50 amps from a 100 amp charge source and AGM may accept the full 100 amps in the initial boost stage of charging, so that part of the charge cycle will be faster.

Battery Charge efficiency is how much of that current is actually converted to stored Ah. This is the value you have to input into a good battery monitor to help it more accurately calculate the Ah stored in the battery. A typical default value is 85%. Wet Led Acids can be anywhere from 70-85% and AGMs can be as high as 98%. Battery efficiency is very non-linear, so at 50% State of Charge it may be 95%, but above 85% SoC it may be less than 50% which means witrh every 10Ah charged only 5Ah get stored. This gets worse the closer to 100% SoC you get.

So if you want to store 100Ah in an FLA bank with an 80% efficiency then 125Ah has to be input. (80% of 125 is 100). With an AGM bank at 98% efficiency then only 102Ah has to be input to raise the bank by 10 Ah. That's 23% less Ah needed to raise the bank by 100Ah, so it is charging 23% faster. Lifeline claim 20% faster charge. This happens at all stages of the charge cycle, so even a modest Solar Array will put more Ah into an AGM than an FLA bank.

With AGMs you don't need a high current source to charge faster, but it helps. AGMs high Charge Acceptance Rate means that you can happily put 100 amps into a 100 Ah Lifeline battery, whereas Trojan only recommend 10 amps, so Lifelines can charger very much faster than Trojans.

[colemj]

Originally Posted by sailinglegend

even a modest Solar Array will put more Ah into an AGM than an FLA bank.

This is not possible.

Mark

[colemj]

Originally Posted by sailinglegend

AGMs high Charge Acceptance Rate means that you can happily put 100 amps into a 100 Ah Lifeline battery, whereas Trojan only recommend 10 amps, so Lifelines can charger very much faster than Trojans.

On another thread, Mainesail and Btrayfors posted actual experimental data showing the opposite of this.

Mark

[sailinglegend]

Originally Posted by colemj

On another thread, Mainesail and Btrayfors posted actual experimental data showing the opposite of this....

Then why not be helpful and include the link, I'm always happy to be proved wrong - you never are!

[colemj]

http://www.cruisersforum.com/forums/...-127411-4.html

Mark

[sailinglegend]

Originally Posted by colemj

On another thread, Mainesail and Btrayfors posted actual experimental data showing the opposite of this.

Mark

I quote Btrayfors:

At 50% SOC, the maximum acceptance rate is just over 1xCA or just over 100 amps for a 100AH AGM battery

This is exactly what I said.

Trojan recommend a 10 amp charge rate - see their literature - there can be no argument with that.

Sometimes I just don't understand what planet you are on!

[mitiempo]

Originally Posted by sailinglegend

With AGMs you don't need a high current source to charge faster, but it helps. AGMs high Charge Acceptance Rate means that you can happily put 100 amps into a 100 Ah Lifeline battery, whereas Trojan only recommend 10 amps, so Lifelines can charger very much faster than Trojans.

I have never seen a battery manufacturer recommend a charger at 10% of C. 25% is more like it.