Battery to fit in tub that’s larger than a Group 29?

mickietucs

My 2016 320S has a Group 29 battery. I do not know what that means in AH. Right now dry camping. Have a Renogy 100w portable solar and running my fridge on propane and a 12v Iceco GO20 fridge. Amongst trees so not getting full sun to solar and trailer battery goes between 11.96 (when compressor kicks on) to 13. Wonder if I should get a bigger battery and if so which one would still fit in tub. Already kind of tight in there. Thanks. 

Denny16

The quickest (and one of the best) ways to increase battery capacity on an older 320 with the smaller battery area, is to go with a small 100 amp lithium battery, like the Renogy lithium battery which I believe is around the size of a group 29. 

The 11.96 volt reading you are seeing when the cooler compressor comes on, is showing the load of the compressor is drawing on the battery.  To get a true battery voltage reading, charge the battery, turn off the battery disconnect switch, wait at leas 5 to 10 minutes, read the battery voltage from the battery directly.  

Then run your trailer’s electrical system with the cooler for several hours, to a half day, with no additional charge going to the battery (solar panels)., then turn off the battery disconnect switch, wait 10-20 minutes, and take another battery reading.  The difference is the power used by the trailer during the test period.  If the rest was for 4-hrs, then divide the voltage difference by 4 to get how much power you are using per hour.  

Then add the solar charging to the system, and recharge the battery back up, and run the test again with the solar working, to see how much the solar is adding back in.  This will give you an idea of how much battery capacity you need.  

Most lead acid group 29 batteries are around 60 amps, of which you can only use about 40 amps max.  A 100 amp lithium will give you 85-90 amps of power, so will double your current capacity, and wil, reduce the tongue weight a small amount (difference in the two battery weights).
 Cheers 

dragonsdofly

@mickietucs I will just answer your question as to the largest lead acid battery profile you can fit it your tub. I have a group 31, 110 ah battery in my front tub so you can fit a larger profile in. We did have to remove any battery box and just cover the top with a plastic lid. The propane bottle is in exactly its original location with no relocation or adjustment of the propane rack. We cut a piece of ¾" plywood the same dimensions as the battery and screwed it into the crossmember of the tongue to support the larger battery and screwed a strap to that to secure it. The battery (and plywood) is angled in the tub so it fits without altering the standard propane tank position. We have been traveling that way since 2018 and all is well. We still have room for leveling pads and supplies, like gloves in that tub. Hope this info helps. 
-Denise

mickietucs

@dragonsdofly - that sounds like it would work. May I ask the brand name and where you got it? My present battery is already angled on a piece of wood (but in a plastic battery box which can be removed). 

@Denny16 - thanks and I’ll also look into a lithium although that one from Renogy is out of my price range. 

ScottG

I currently have an Interstate g31 in the "g29" box I installed several years ago. 

The box was a bit roomy for the previous g29 battery, but the g31 is only a bit bigger and fits perfectly. 

It's worth checking the size specs of different batteries and comparing them to your space--you may find one that slides right in!

BrianZ

Ref:  https://tab-rv.vanillacommunity.com/discussion/comment/101709/#Comment_101709

@mickietucs,
We are using a Trojan-1275 12V Golf Cart Battery with 150AH in a NOCO Group 27 box, as shown in the link above.  The only disadvantage is its weight, 85 lbs, but it's cheaper than Lithium (we paid around $200 4 yrs ago) and gives almost the same usable AH.  We bought ours at a local shop that sells & services golf carts.  If you get one, get the "plus" version with shorter cable lugs, which would be a better fit, height-wise.  Ours is a quarter inch too tall for the box lid to snap shut on both sides; though it's not a problem since the strap holds it snugly in place.  See photos at the link above.

dragonsdofly

@mickietucs not near the t@b right now, but will post the particulars on Sunday, 08/07/22, about 36 hrs from now. Will even be able to post a pic for you. -Denise

dragonsdofly

@mickietucs finally got to the t@b and got the included pic. This group 31, 110 ah battery was purchased in 07/19 at batteries plus bulbs. It cost about it's ah rating after the old battery (standard group 24, 70 ah) trade in. Husband removed our makeshift plastic lid and buckled the strap back in place so you can see how it fits and rides on the plywood support. Good luck. -Denise

webers3

AmpereTime 100ah LiFpo4 13 x 6.82 x 8.48 inches, with SmartShunt in my 2017 T@B 320S
Left is the front of the tub, right is the rear, top is the propane tank