bigger battery?
 

I'm doing constant engine off coasting around town, and I wonder if a slightly bigger battery would be useful, both for charging capacity and durability over time.

Plus I mistakenly left the ignition on over night, which drained the battery to 1.6 volts this morning. Hopefully it will charge back up, but in any case the battery's getting to the end of it's life.

If a bigger battery is a good idea, what do you recommend for the '99 Civic?

You need a deep cycle marine preferably AGM, not a standard flooded starting battery.
And yes bigger is always better.

Thanks. The battery doesn't get heavy use, maybe 25 miles of engine off coasting in a week.

Even a little bigger battery would be good, a balance between cost, and being able to fit in the same position.

Anymore suggestions are much appreciated.

The battery is 12.5 volts this morning, after a short drive yesterday morning and charging the day before that, so it might survive awhile longer. I think the 92-00 Civic battery is a 51R. A post here suggested a group 34, but that is too big for the space in my car.

Group sizes & dimensions
51r ~ 9.38" L ~ 5.13" W ~ 8.88" H ~ 425 cca / 85 reserve capacity OEM
34 ~ 10.25" L ~ 6.81" W ~ 7.88" H ~ 800 cca / 110 reserve capacity
Size & dimensions with cca & RC

Costco's 51r is 500 cca so I'll get the same one again, unless a larger battery will fit in the space.

Don't worry about cca. You want more reserve capacity.
Which is measured by the number of minutes a battery can support a 25 amp load.

For example my Home made solar inverter generator hybrid uses a group 31 with 205 minutes of reserve capacity.
It had a group 34 with 100 minutes of reserve capacity, but I wanted more.

Thanks for those details.

However those batteries are way too big for my space.

I guess the only option is group 34, or else stay with the Costco 51R.

You are good then.
With group 34 there are a ton of AGM and deep cycle options. When using a group 34 AGM you can expect at least 800cca and up to 120 minutes of reserve capacity (with a deep cycle).
The group 34 optima AGM is what I started out using to power my inverter on hybrid generator. I took that optima out of my hybrid generator and put in my suburban and do lots of EOC.
It has no problem doing an EOC for between 1 to 2 miles with all the lights on then restarting the 7.4L engine.

The 34 would be great, if I can get it to fit in the space.