AGM battery aging out?

Tabnero

that just not look like a 245 amp hour battery to me. I think it is smaller capacity

Denny16

None of the TaB400 batteries were 245 AmpHr., the original ones were 235 Amp.Hrs., which are not readily available any more.  I suspect, they were never 235AmpHr, but closer to 200 AmpHr, as that is what is currently available.  A label does not necessarily make a battery a larger capacity.  The original 235 AmpHr and my replacement 200 AmpHr batteries were the same size.  New batteries are a bit smaller, with the same rating due to better materials being used currently.  The TaN 400swith two 6VDC batteries are 224 amp hrs.
 Cheers 

Aubrey

we are about to order the Renogy 200aH Deep Cycle AGM directly from Renogy.
Good enough price to take a risk, 2 yr warranty (I hope) 3rd party sellers look like a crap-shoot.
We are loving the portable solar from them.

XenanMe

@Aubrey I switched out the old AGM battery for  lithium.  It was pricey but worth it for us because all of our camping is boondocking.  That Renogy battery looks like a good deal and I have only had positive experiences with that company.  Good luck!

Aubrey

More real world experience. Thanks!
I wanted to sleep on it.  Since we have only ever camped on a 6-7 yr old battery i have no baseline to compare.
We are reformed  hippies, so we dont use the coolcat much. (A propane genny for emergencies would be nice, and prolong battery life)
The 200w portable seems like a winner, and it was charging the same old Discovery EV4D from 2018

Aubrey

We purchased a 200aH AGM from direct from Renogy and I installed it with battery voltage at 13V rested, but in just an hour or so of Fantastic Fan-fridge-radio-USB fan use it is down to 12.5V.  This seems to be a faster drop than my OEM Discovery battery. I am continuing the driveway test but worried I either have overestimated Boondock capabilities,
have an excessive draw somewhere
or have purchased a faulty battery.
I know I need to be able to monitor amp usage to know in more detail what is happening. 
After pulling fridge fuse and turning of fans, battery rested for an hour I am at 12.75v , about 90% charge
Gonna continue running fans awhile (no fridge) and see what voltage is later tonight. 

Grumpy_G

Don't overthink it. The battery capacity is determined by discharging it all the way down to 10.5V so 13V to 12.5V is a fraction of the nominal capacity. Plus, if you look at the ever popular voltage-SOC charts you'll notice the voltage drops faster at higher state of charge. Also lead-acid deep cycle batteries require 15-20 cycles from new to reach full capacity. 

Aubrey

Well raise my rent! Im still learning. Ha!

Sharon_is_SAM

If you are drawing a higher current (fan on high, frig cycling, etc) it will drop the voltage faster than how you normally use the TaB while boondocking.  We are still careful with what we use even though we have plenty of power.  Lucci light, turn off the Alde, USB and pump when not using,etc.  After you turn off the appliances and let it rest, you saw the voltage return, so it will be artificially low when under load.  Keep in mind that voltage is not the best way to measure the state of charge of your battery.  How are you measuring the voltage?

pthomas745

The rested battery phenomenon is real.  All you are seeing when you try to measure battery voltage while a lead acid battery is being charged or "in use" is...a lie.

Pulling the fridge fuse, etc, is not enough to turn off the battery.  The battery disconnect switch must be off. Even at 12.75, an AGM state of charge chart would show you at 90 percent of battery capacity.  Your AGM battery, at the very least, has 100 amps available. In an hour of use, even the Fan/TV/Fridge/USB and parasitic drain combo will not draw the 10 amps of power that "seem" to be taken from your battery.  The 12.75 reading appears to be another "false reading".

All of the amp needs of each device in the trailer are well known.  This is a spreadsheet from Jenn Grover's page that I used in my 2017 that should pretty much fit the items in your trailer.  Believe it or not: it is really hard to run enough things in the trailer to come up with 10 amps of usage in an hour. 

Aubrey

UPDATE..  The renogy battery has had a couple few cycle in the driveway but not much. Just did a single night of camping, no hook ups,
fantastic fan on low 1.25 amp
fridge on 3               3.6 amp
TV for couple hours  1.25
stereo for few hours  0.5
and very little water pump use

drove home 25 minutes and parked for another 24 hrs with fridge still on..
Battery showing 11.7V or so
I just cant get used to running down to %20 SOC for just one night of camping.
I could deploy the solar, but I expected more capacity unhooked.
it seems my old battery wasn't as far gone as I assumed, but thats water under the bridge. We must be energy hogs or something, not getting anywhere near the multi-night boondock experience I have read about here.
Still learning.

pthomas745

"Battery showing 11.7V or so."

What battery monitor do you have?  Somewhere in the thread you mentioned "the solar monitor", but we still need more info.  Sounds like we already discussed the "rested battery" idea, too.

So...lets dig into your battery monitor.  Which one is it?  Victron?  Has it been set up for your new battery install?

Something here...just isn't right.  If you have the Victron, show us your Status and History screens.

Aubrey

I check voltage with a multi-meter at the Zamp port. I definitely  need a more sophisticated device.

qhumberd

On my 2019 400 there are 2 6V Harris AGM batteries. The spec sheet states 224 amp hour rating. My 100 watt RENOGY portable panel controller is set for AGM and charges full at 13.4 V. I have a shunt connected so can accurately read voltage with trailer battery switch off after a full charge the shunt voltage readout tells me I have 13.1. Volts initially and no appreciable drain. The next day and even a week after the voltage drops to 12.83 volts with the shunt still showing a full 224 amp hours available. Per the voltage reading at rest it would seem I am at 80% charge. Is this what an aging battery is doing or is something else going on? Thanks 

Aubrey

I plan to get my our trailer a smart shunt this winter, but I can say after resting for weeks in the garage my trailer battery is still at 12.9V.
When I get the shunt I may realize the Fridge is just to costly to use when boondocking. 
Meanwhile I also plan to experiment unplugged in the driveway but with fridge unplugged and breaker turned off.