Costco Interstate 27DC

jimpink

Greetings All, 

I have been searching the forum and can't quite find a specific answer to this ... 2017 T@B CS320. Need to replace the battery. I looked at and decided not to go with lithium batteries. Can I buy and install from Costco: Interstate 27DC Marine/RV Battery? (Part Number: 8-27MBP).

I think this gives me more power for longer than the 24D, although I see that I will also need to replace the battery tray and plastic case to fit the 12.74" length of the 27DC and am looking into this now. 

Thanks in advance for any advice.

Sharon_is_SAM

I assume the original tub.  For about the same measurements you can fit a 100 Amp hr AGM battery.  The Costco sited only gives you 66 Amp hrs of which 33 is usable before you start taxing your battery longevity.  

jimpink

Thank you. Never heard of an AGM battery - I'll look into it. More AH without having to mod the battery holder would be really nice

dragonsdofly

@jimpink we have a group 31, 110 amp hr deep cycle battery fit in our plastic tub. Also have the 20 lb propane tank, leveling blocks, wheel chocks and the usual stuff. That gives you 55 amp hrs of power to use. We tried different models, sizes etc, but this is the largest, most powerful single battery possible in that space without removing or downsizing the propane tank. We have less than ½" clearance and cannot fit a full battery cover in, but instead a top cover protecting the posts and electrical connections. Just wanted to let you know many options exist to get more power for your t@b.

jimpink

Thanks all for the ideas and recommendations

Grumpy_G

Note that the "50% usable capacity" is a RV forum obsession. You can draw 80% of rated capacity from a lead acid battery but it will not last as long. It's a choice between enjoying camping and buying a new battery every two years or trying to eek the maximum lifespan out of a battery. The Alde system and the older 3 way fridges work down to ~11.5V which is what a 80% discharged SLA battery puts out. I do not know how the newer compressor fridges react though. 

AnOldUR

Grumpy_G said:

... I do not know how the newer compressor fridges react though. 

Not sure about the factory 2-ways, but we use a couple of 12V chest fridge/freezers. Voltage drop can be a problem even though the battery has not reached the fridges low voltage cutoff.

pthomas745

I had this battery on my Amazon wish list for a long time.  Group 27 deep cycle.  A true deep cycle battery, without any compromises.

There are many others just like it on this Amazon page.  Measure out your battery area and see how the box fits.  It can fit in any configuration, just not upside down.

This battery will be a true upgrade of amp hours and performance.

https://www.amazon.com/Universal-Power-Group-100Ah-Battery/dp/B00S1RT58C/ref=sr_1_1?keywords=Universal+Power+Group&qid=1691711693&sr=8-1&ufe=app_do:amzn1.fos.f5122f16-c3e8-4386-bf32-63e904010ad0

Marceline

AnOldUR said:

Grumpy_G said:

... I do not know how the newer compressor fridges react though. 

Not sure about the factory 2-ways, but we use a couple of 12V chest fridge/freezers. Voltage drop can be a problem even though the battery has not reached the fridges low voltage cutoff.

The manual for my old (2013) Norcold 2way says that the cut off is 10.9 volts, but I think that in reality the cut off is actually a little bit higher.

Mickerly

Voltage to state of charge varies based on battery constructions. If you are measuring your battery that way, make sure you are using a table for your type battery; AGM, RV/Marine. auto, Gel are all different. Also, that is a resting voltage. The voltage reading while being used will go up and down as the load changes and is a meaningless reading in itself. 

Grumpy_G

The tables are typically for a C/10 load, meaning the current is capacity divided by 10 (just ignore that the units don't match ) In this case 11.5V indicates 20% state of charge. I had posted a table for different loads here: https://tab-rv.vanillacommunity.com/discussion/14588/battery-soc-vs-internet-myth

Mickerly

Agreed. Let me be more clear. The 50% number is folklore that probably needs to fade away. Different types of lead/acid batteries have have different discharge curves. Different loads will give different volt readings, as your chart indicates. If you are off grid and need to see you battery usage, getting a battery monitor is a prudent move.

If you camp mostly with hookups, Costco's battery will work perfectly. For off grid camping, you may want a more capable battery and a method of monitoring. For a mix camping styles, an100Ah AGM battery is a good recommendation.

Homebodyatheart

I have a 2017 320S Tab. I had a group 27 battery installed before I took delivery in early 2017. I am still using the same battery, just check the water levels regularly, and I do mostly camp with full power hookups.  I am also very careful about the order of plugging and unplugging to shore power. The dealer installed the group 27 base frame on top of the stock group 24 base frame. I’m not sure how they attached it, but it hasn’t budged in seven seasons. Good luck with your decision!