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Prognosis and best way forward for new, unused and neglected AGM battery
Please help me make the best recovery from a blunder with my AGM battery. Details of it and its history are shown on the graphic. 

If I understand correctly now (I've been slow to learn), both the idle time (without charging/maintaining) and the drop in voltage from use  are important--there are two variables, not just the voltage drop, to consider in maintaining a battery. 

As described in the graphic (which I hope to link effectively) my battery got a brief charge from my 5 amp Deltran Tender upon its delivery. The curve shows the brief initial charge and the subsequent continuous voltage decay for the 3 1/2 months it's been in my possession. 

1. What should I do before testing the unit the first time for one night of sleep? (I have that *&!*$$$ Resmed adapter.)

2. What fuse rating and wire gauge should be added to protect the setup and where should it be inserted?

3. What is best practice in keeping the battery maintained after doing those first things (no. 1 above) and after that first night or more of use?

4. With repeated sleep sessions on the battery power, at what point should I hook up the Deltran and for how long or to what effect (what recharged voltage?).

----While the battery is idle on the shelf
----After a night/nights of use

I plan to assemble durable protection to prevent a direct short across battery terminals.

The battery, Resmed adapter, Multimeter, Battery Tender, and cabling fit well in a rugged, open tool bag and will be setup for quick connection if my power out buzzer comes on or if my utility company notifies me as a medical equipment user (which it claims it will do in normal outage circumstances). If I travel by car or go on a short camping trip the bag will have the essentials.
Any and all suggestions would be appreciated.


[Image: 4UCePpcl.jpg?2]
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2Sleep, an AGM battery does best using a low amperage absorption charge, rather than a higher 5-amp. The absorption charge should take the battery to 14.2 to 14.5 volts DC from which it will come to a resting voltage of about 13.2 after 8-hours. The ideal charge voltage is higher and amperage lower than a flooded lead acid battery. The ideal initial charge should be done at low amperage for three to five hours at the current equivalent of 1/10 of its rated capacity, until fully charged. For a 10 amp battery, a 1-amp absorption charge is ideal. So the use of a 5-amp charger is only appropriate for a very large 50 amp battery.

The YUASA Technical Manual is a great resource for AGM batteries http://ktm950.info/library/assets/pdfs/Y...teries.pdf This manual discusses natural discharge rates, activation and maintenance practices. I consider this best-practice for batteries, and other manufacturers also provide technical specifications and recommendations.
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Hi 2SB,
Your battery is pretty resilient. A charged battery can easily sit for a few months without being recharged. It only dropped from 12.96 to 12.86. It is still good.
Don't leave it sitting for months discharged.
1. Hook it up to the minder. Although it is rated at 5A, that is max. Your battery is almost fully charged. It will probably accept a charge less than 1A.
2. If you have an adapter from Resmed it shouldn't require an extra fuse to give it a test. Make sure you connect it properly.
It you want to add a fuse in, place it inline on the positive terminal wire. Use a 5 or 10A fuse and the same guage of wire as the adapter from Resmed. Probably about 16AWG.
3. The main thing is to not let it sit for long times in a discharged state. Use it then recharge it. Depending on the size of the battery and how much you discharge it you should be able to get a couple of nights on a charge. Do you use a heated hose, humidifier? They take more power.
4. The Deltran is smart. It will charge the battery at the correct rate. You can leave it on as long as you want. If you are uneasy about that, disconnect it. Keep the battery above 12.8V
If you don't use it for a couple of months, hook it up again. The battery likes to be in a charged state.
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Many thanks Sleeprider and Mogy for your advice regarding the new-to-me AGM battery and its requirements.

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