I just used the search function upper right of this page and searched on "adding house battery' and got over 10 pages of hits. You might want to start there.

 

I did that first, along with several search queries related to battery size.. read through a couple of the threads returned. I did find one thread stating that a second battery would fit under the starter battery, but it was for a different application. I am seeking info on the largest capacity battery that will fit in that space.

 

Hmmm. Strange. I just did it and clicked on a couple of the links that came up and was able to learn that the battery size is H6. Clicked on another link and saw mention of Optima having an 800CCA battery in an H6 configuration, rated as "one of the highest amps available".

 

But, that's not what he's asking. He wants to put a second battery in there, not upgrade his current battery.

OP, the problem is that the single flooded cell takes up more than half of the space. I can't recall if anyone has squeezed a second battery in with the OEM single, but, it would not be much of a house battery.

Some guys here have changed their OEM single into 2 AGM batteries (which are smaller than the single flooded), similar to the Ford option. Still not sure if one of the two has been devoted to house duties.

The search function on this forum sux. Better to go to Google and enter something like site:www.fordtransitusaforum.com add second battery
(although that search will probably bring up the guys putting in the 2 AGMs)


EDIT -- Apparently, my understanding of the battery dimensions is wrong. pjtezza says on page 2 of this thread, that the single flooded battery is the same size as each of the dual AGM batteries.

 

There was one guy on the forum who put a heater under the drivers seat and put his house battery under the passenger seat.
I remember reading a thread with pictures how he did it.

 

That'd be me.


Lifeline GPL-30HT 150AH AGM battery on its side under passenger seat:

https://www.fordtransitusaforum.com...-transit-general-discussion/22553-house-battery-where-what-type.html#post962284


Saga of Espar install under driver seat

https://www.fordtransitusaforum.com...aforum.com/diys-modifications/71876-espar-webasto-planar-under-driver-seat.html

 

I put 2 group 27's under the drivers seat along with the starter battery. Had to stretch the seat frame a bit.

 

That looks factory. Nice job! That is probably beyond my abilities. I never learned to weld

What are you using to charge the two group 27s? A b2b charger?

 

I didn’t pull the battery box out to confirm, but since I had my driver seat off I did measure the dimensions of the base for the battery box, and it looks like it’s about 13.5 inches wide by 14 inches long. So whatever combination of batteries would fit within that square would work in that space. I have the single AGM Ford battery myself, and I could fit two of them by getting rid of the battery box.

 

Two 100ah AGM under the passenger seat (dry fitted, haven't relocated here permanently, yet):

https://www.fordtransitusaforum.com/camper-vans-conversions/41778-house-batteries-under-passenger-seat-2.html?t=41778&page=2&amp=1

 

I'm using a CTEK D250SA with Smartpass. The batteries are Crown group 27 6 Volts and less than 8" tall. I got a 10% discount and free shipping from this site:
https://www.techbatterysolutions.com/6CRV215-Crown-6CRV215-AGM-Battery-6V-215AH-p/6crv215x.htm

 

That is a nice set-up.

 

Two of the OEM size batteries fit under the seat without modification other than removing the foam barrier. Here's a pic of a single H8 battery (I forgot to measure to see if two would fit, it looks close)

 

Thanks for posting that picture. I cannot tell, is that the driver's seat?

 

I researched this extensively a few years ago when I was building my first Transit conversion. If you want to keep the stock battery box intact, the only option is to add another battery of the same size. The Ford lead/acid battery is the same physical size as the AGM battery used in the dual battery configuration. The battery box is unusually short and this limits the battery sizes available. The plastic battery box for both options (single battery vs. dual batteries) is the same basic size, but it has a few different bumps in the bottom. I was able to mod my single battery box to accept two batteries. I bought the right size name brand AGM battery on Amazon for a very low price including shipping. There is rumor that there is an upgrade kit available from Ford that has the dual battery box, but I haven't actually heard of anybody using it. This extra battery gives you 85Ah. I left my original lead/acid battery and added an AGM battery. This mixing of battery chemistry was considered sacrilege on this forum, but it worked for me for 3 years and, AFAIK, is still working for the new owner.

 

I left my original lead/acid battery and added an AGM battery. This mixing of battery chemistry was considered sacrilege on this forum, but it worked for me for 3 years and, AFAIK, is still working for the new owner.

I am surprised that someone who builds custom camper vans to sell nationwide has not even done basic research, Mixing different battery chemistry types has always been wrong, And not just on this forum!

https://www.optimabatteries.com/en-us/experience/2014/04/can-i-connect-dissimilar-batteries-parallel

 

My goal is to run a 12v fridge, a fan at night and some led lights. I am reluctant to put a hole in the roof for an exhaust fan but I realize a season of using this van may change my mind.

Here are my questions.

1. What is the highest capacity house battery that will fit next to the starter battery under the driver's seat? I assume I want AGM but i don't really know.
2. Given the answer to 1, what b2b charger output do I need to service this battery?
3. If there is an appropriate battery that fits, will I need a second charging source in addition to the alternator? Typical event has the van stationary for a long weekend max. The only appliance I'd keep running is the fridge.

Just my opinion but why in the world do you want to increase the hassle of trying cram all the extra complexity in the space under your driver seat? There is a lot of room in a van. Eking out whatever you save by stuffing so much into the small space you'd be allotting just doesn't seem worth it.

I have a 200ah lithium battery that uses no other charging source than the alternator. I too did not want to cut a hole in my roof and didn't. I have slider windows in the rear that provide all the fresh air we need. If you are determined to squeeze a second battery under the driver's seat I would think that whatever AGM battery you find that works, you could find a Lithium with more power that is likely even smaller.

I think my battery setup is about as compact as I could have achieved and would have gone crazy if I'd had to squeeze it all in next to my single starter battery. (Ignore the inverter in the upper half of the picture.)

 

If there is a b2b charger between the lead acid starter and AGM house battery, does this no-mix rule still apply?

 

No mix: Battery types, Not battery chargers.

 

I love this... i am getting ready to put in an aux battery and it never dawned on my to use the second battery under the seat as the house battery. I will search for threads on separating the two and to see if these is feasible. It would save space for sure.

Killer job on the extension of the battery area too. So many of you are craftsman, I love seeing your work.

 

Six of these 35 amp/hr AGM fit under the pass seat. I'll be installing soon and post some picks. Total of 210 amp/hrs.

 

Interesting approach.

They are a deep discharge type, rated for ~ 6 amps max continuous, so (6 batteries) x (6 amps) x (12 volts) = ~ 400 watts.

Refrigerator and lights =yes
Inverter = challenging

 

Well, for anyone following along, I just finished installing a 100ah AGM battery under the driver's seat, next to the starter battery. I used a CTEK b2b charger, which I mounted on the back of the seat base. This did not use any floor space. Everything is tested and working as planned. I also tied in a Blue Sea fuse box and battery monitor. Now, I just need to find a place to mount them that fits the stealth mode for this install.

 

Pics... Please!

 

I installed 100AH Calb LifeP04 battery under drivers seat next to stock AGM starter battery -

Its a Tight fit but doable and has been there for 2 years -

 

Is the stock starter battery an AGM? TBH, I assumed it was lead acid and did not inspect it closely.

Also, were you able to reuse the metal lid that bolts on the back side? I was but it was a really tight fit, and required several iterations of cable routing.

 

Pics... please!