AGM Charge Rates and Times

[jrnymn7]

I am interested in knowing how fast AGM deep cycle batteries charge, especially in the upper SOC range.

Things to consider:

- Ah Capacity of battery/bank

- starting SOC or DOD, or Ah's consumed/replaced

- Charge Rate, expressed as C/? (Battery Capacity divided by charging amps... i.e; 400Ah/100a = C/4 rate)

- At what point do amps begin to taper?

- Charge time

- ???

Thanks for any input you can offer.

[mena661]

landyacht318 wrote:


Those with lower voltage charging sources will be able to charge AGMs faster, but when voltage is pushed higher the gap narrows but to what degree, I cannot say.

Or maybe it charges faster at higher SOC's?

[landyacht318]

I am probably among the few who has both a flooded and an AGM I can cycle independently, and also has the tools to measure amp flow as well as an adjustable voltage charging source. So I did a little experiment, and the results were generally as suspected.

Those with lower voltage charging sources will be able to charge AGMs faster, but when voltage is pushed higher the gap narrows but to what degree, I cannot say.

[pianotuna]

Hi Landy,

That is compatible with AGM having much lower internal resistance than flooded.

landyacht318 wrote:
So at least in my two batteries, the AGM does indeed accept higher amps at lower volts. I don't know how much faster it would charge overall to 80% to 90% or to 99%

But again, the flooded battery has 330+ cycles on it, the AGM ~ 30. So it is hardly a scientifically accurate observation.

[landyacht318]

Last night I took 55 AH from my screwy flooded 31

At 9 AM the solar had voltage upto 12.6v

I set MW to 13.9v and plugged it in.

18 amps began to taper immediately

When I cranked it upto 14.9v, 40.95 amps

Comparing this with the AGM which had 30 amps removed, the AGM took 22 amps at 13.9v.

So at least in my two batteries, the AGM does indeed accept higher amps at lower volts. I don't know how much faster it would charge overall to 80% to 90% or to 99%



But again, the flooded battery has 330+ cycles on it, the AGM ~ 30. So it is hardly a scientifically accurate observation.

[NinerBikes]

mena661 wrote:

jrnymn7 wrote:

I've noticed a few come with a 15a charger. How weird is that???

I find it weird too. And I haven't seen any large amp LI chargers either. You would think high amps chargers would be more common with LI.

Hey Landyacht! For me, the big deal with LI is 80% DOD, lighter weight per amp-hour (even lighter because you don't need as large a batt bank), flat discharge curves and zero maintenance (actual zero maintenance not the don't choose to do any maintenance, zero maintenance). The rest falls in the techie neato category (which I have no problems talking about all day long :B).

I am in this camp. Lighter battery means less tongue weight on the TT for me, a good thing. Also with LiFePo having a cut off BCM and steady voltage from 90% to 10% SOC... I am thinking that even with running the heater... unlikely with 100 AH Li FE Po, even with 80 amps useable, I'll ever really get too deep into the battery with running the heater at night, although the damn blower sure is noisy. Compares favorably to the 90 pounds of T-1275 that yields 75 amp hours for 50% SOC.

I think I have more than a few years left in my T-1275's before I'll have to fork out the $Bignum for LiFePo, so hopefully the price of
'em continues to fall.

Trojan batteries better get off the FLA and AGM battery bandwagon and start working with the new Li battery chemistries, before they go the way of the buggy whip.

[christopherglen]

mena661 wrote:
You mean 5% SOC, right? If you're only using 5% of your banks capacity at a time, wow! Also, I wouldn't consider 5% to be a cycle. IMO, 80% and below would be a cycle. Hey MEX! I WAS going to go LI 5 years ago. If it was only about $1000 cheaper then, I would be running that now instead of the L16's. Price is always an issue.

5% DOD, 95% SOC, they are designed for 10 days without sun to 50% DOD/SOC. It is a single battery, ~225AH if memory serves, running a load 24/7 365.

[mena661]

Most of the companies that sell to the public use the same manufacturers of LFP cells (Winston, CALB, Hi Power, GBS are a few). Price differences between the cells themselves are small and the quality is the same between them (at least I'm not aware of any that stand out). There's not that many available to the general public. The one's you read about you simply cannot buy, not to mention they are custom built and designed for specific environments. The company most used on the racing sailboats is Genasun, I think, and they seem to be accepted as the best BMS manufacturer also. Mastervolt is another. Both are really expensive and only sell pre-packaged batteries (cells plus BMS). I don't know what cells they actually use.

Winston
CALB
GBS

[MEXICOWANDERER]

Time to play Devil's Advocate again...

How many companies are manufacturing lipo batteries that can be used in R.V.'s?

When you advocates are pricing batteries are they made by the same oufit that makes lipo batteries for cruising sailboats? The applications that according to many exhibit all of the profound attributes unique to lipo batteries?

Or, are they the comparitive "low Priced Spread"

You are undoubtedly aware of the Jeckyl/Hyde difference between a Full River or Lifeline and the peanut gallery wanna be's? Lifeline was not kidding when their .110" positive plates and money-is-no-object thick plate paste makes a laughingstock out of AGM competitors with .045" plates?

I can only wonder if lipo is going to have or already has laughingstock grade "discount" grade of batteries? Sorta you know like comparing a Johnson Controls battery to a Rolls & Surrette?

[mena661]

You mean 5% SOC, right? If you're only using 5% of your banks capacity at a time, wow! Also, I wouldn't consider 5% to be a cycle. IMO, 80% and below would be a cycle. Hey MEX! I WAS going to go LI 5 years ago. If it was only about $1000 cheaper then, I would be running that now instead of the L16's. Price is always an issue.

[christopherglen]

The big selling point of the agm's for me was 0 maintenance - ever, and the fact that we have a solar cathodic protection system that is 10 years old, that puts it at over 3500 (shallow) cycles. And it is still going strong. The extent of maintenance on it is cleaning the panels in the fall, once a year, that's it. It is designed with a 5% DOD during summer, in snow season the controller *should* hit the low voltage cutoff when the panels are buried. So there is the occasional deep cycle, and during overcast weather in winter it may not get into float all the time. I know of no FLA's that can go for years being ignored, and enjoy it.

[MEXICOWANDERER]

Politics, cars, wimmen, music, tires, beer, tools, haircut, once a guy makes up his mind there is no way in hell somone else is going to argue him into changing his decision. The harder you try the deeper he digs his hooves, I mean feet, into the ground.

I'd LOVE to see lead disappear. Then I peek at my emaciated bank balance. I would be estatic to have a Mercedes 600, Christian Dior, Armani, Rolex lifestyle but instead of Mum's I have to settle for, (as Redd Foxx put it) "Champipple".

A person's gotta do the best he can with what he's got.

[mena661]

jrnymn7 wrote:
Yep, at u.s prices, though. Right now we're getting killed on the exchange. Today I spent $10.44u.s. on EBay... came out to $12.99can!

I totally forgot you're from Canada.

[jrnymn7]

Yep, at u.s prices, though. Right now we're getting killed on the exchange. Today I spent $10.44u.s. on EBay... came out to $12.99can!

[mena661]

jrnymn7 wrote:
200Ah LiFePo4... $2400 (complete with BMS)

Just under $2000 for THIS ONE.