AGMs - are they really worth the cost?

[WaltBennett]

I went with flooded cell batteries (four T-105s) when I found it would be almost twice the cost to go with AGMs two and a half years ago. Even dropped the Trojan automatic watering system as it would be close to $200 extra. Put a first of each month reminder in my Google Calendar so I wouldn't forget to check them. After an extended vacation to the dry Southwest desert, and a second even longer one to the middle of even dryer NV and CA, I still haven't had to more than top off any of them. Never has taken more than a half hour or even 1 1/2 pints of distilled water in a month. While I'm aware that not having to look at them at all may be a benefit, I don't think it would have been worth the ~$400, but then that's just IMHO. (Maybe I'll put something up about MPPT vs. PWM some day.)

[DQDick]

Charging faster and discharging slower works for me. Not having to check them is just a side benefit.

[mlh]

I see no need for AGM batteries for a camper. My new F150 came with an AGM battery. It has start stop, when you come to a stop with your foot on the brake the engine cuts its self off then when you take your foot off the brake it restarts. This will eat a standard battery. You don't have this constant short term draw on your batteries. Your draw is longer and more constant. If it was my camper I wouldn't spend the money for the AGM batteries. I think there is no advantage for your application.
Lynwood

[Starmaster]

Hi DQDick,

I'm curious about your " discharging slower " statement. How can the battery design (AGM vs Flooded) affect the discharge rate of a battery?

Discharge rate is a function of current drawn and for how long. The only way I can think that an AGM would last longer than a Flooded would be if the AGM had a larger amp/hr rating.

AGM may be able to take a higher charge rate but doesn't that require a special charger that is "AGM aware/optimized"?

Dave

[mlh]

AGMs tyke a slower charge rate, 10 amps max or you will burn them up.
Lynwood

[DQDick]

If you goggle why are AGM batteries better you'll find a lot of articles, but the basics come down to this: AGM: The Absorbed Glass Matt construction allows the electrolyte to be suspended in close proximity with the plates active material. In theory, this enhances both the discharge and recharge efficiency.

[WaltBennett]

Don't know about that DQDick - if so, why do equivalent size AGMs have lower amp hour ratings than flooded? Also, both my inverter/charger and solar charger have specific settings for flooded and AGM (and others) so that they charge at a lower rate for AGM.

[DQDick]

Only know how it works in my rig with my system.

[mlh]

Dick I guess you have these batteries. Do you think they are they better and are they worth the extra money for a camper. The only one I have ever had is in my F150.
Lynwood

[TLightning]

AGMs can be mounted in any position (upside down if you want to) and when mated to a proper charger, you can forget about them. Also, they do not give off any gases like flooded batteries. I had them in a previous motor home (four six volts batteries), but wouldn't get them in the Montana where I pull the battery out in the winter.

[DQDick]

quote:Originally posted by mlh

Dick I guess you have these batteries. Do you think they are they better and are they worth the extra money for a camper. The only one I have ever had is in my F150.
Lynwood

I full time and make extensive use of solar, including running the convection oven, making coffee, using the vacuum and other things your not supposed to do on solar. For me they're worth it, and when I was a LEO I had a battery on a car explode on me so the no gas thing would be worth the money anyway.

[NRA-Girl]

quote:Originally posted by mlh

AGMs tyke a slower charge rate, 10 amps max or you will burn them up.
Lynwood

Not sure where you got that info from but its totally wrong. AGMs can take much much much larger charge rates than Wet Cells.

AGMs have much lower internal resistance (less heat during recharge) this means less of the incoming energy is converted to heat and results in faster more efficient charges. AGM charge efficiency is in the 98% area where as wet cells are in the lower to mid 90's

To replenish 100 ah pulled from an AGM it takes less power and time than it does for a wet cell.

Another poster also mentioned that AGMs have lower AH ratings but that is not necessarily correct either. Side by side an equivalent sized AGM might have a lower 20hr AH rating but it you look at ALL the specifications, you will see that at high discharge rates an AGM will provide more AH.

Also an AGM can be discharged to a much lower state and recharged without as much degradation as a wet cell. The general thought is not to discharge a wet cell to more than 70% where an AGM can easily go to 50.

The AGM charge profile calls for lower voltages generally than a wet cell but that does not mean it charges slower. Due to its extremely low internal resistance an AGM will still charge faster at lower voltage than the Wet Cell will at higher voltage.

If you leave your RV parked for long periods, just disconnect the AGM and leave it. Come back a year later and it will be fine. Do that to a wet cell and it will be dead - or darn close to it.

No gassing, No checking electrolyte, mount in any orientation, low self discharge, higher charge efficiency, higher discharge capablility... AGM's have many benefits.

Is it worth the money? Well that depends. If you are cheap then they definitely are not worth the money. If you buy Chinese tires to save money then they won't be worth it.

But -I f you like the finer things then they might be. If you like convenience and are willing to pay for it then they might be. For solar applications like Mr DQ was talking about - where every AH saved (during more efficient charging) can go back into the batteries- they probably are.

[Bigboomer]

AGM'S are worth every dime over wet cells, especially for fulltimers and boondocking, period!

Are they for everyone, no as noted above but as NRA Girl pointed out you get what you pay for... I put Concord Sun extender (made by Lifeline) so they are made in USA and have had great use out of them.

[mlh]

I posted the AGM batteries couldn't be charged over 10 amps. NRA girl said this was not correct. I have a 2015 F150 with one of these batteries that went bad so I checked on the internet to see what type of charger I needed and got some wrong information. After more research I found she is wright. I learned more about these batteries. According to what I learned :
They store well
Don't sulfate as bad as standard batteries
80% of battery failure is related to sulfation
Some of the deep cycle AGM batteries require special charge rates
Last longer
Don't tolerate high temperature and high discharge rates.
Thanks NRA girl. I learned something.
Lynwood