Spare leisure battery and portable solar panels

[Captain Yoghurtpot]

Here’s one for the sparky peeps.
Might seem daft but here goes.
Currently have one 100 amph leisure battery of lead acid type under passenger seat and no room to fit a second.
Do have room for a second lead acid battery in a portable battery box however,in the front passenger footwell for use when not travelling ie on site.
Distance from battery terminals on box to fitted battery is no more than 2 to 3 feet.
Would it be permissible to connect the 2nd leisure battery to the fitted one in situ and then use the extended 12v power to last me longer than just 1 battery.
Also , could this set up be used if EHU was available to charge both 12v batteries?
Finally, would a 100w portable solar panel be a good idea connected to either the battery box battery only, or directly to the in situ battery only, or to both, running from the solar panel connected to the 2nd battery which in turn is connected to the in situ battery, ie in tandem.
Can’t / don’t want to Put solar on the roof, switch to lithium and reconfigure the charging circuits as the age of the set up and subsequent resale would be uneconomical, and I’m not made of money!
Thanks for any advice.

 

[pappajohn]

No problem fitting a second battery. Minimum 10mmsq cables connected Pos of battery one to Pos of battery two and Neg to Neg in the same way with a fuse in the Pos cable, or even better one at each end of Pos cable.
Solar panel connected to whichever battery is easiest and will charge both at the same time.
Two batteries and solar will more than double your off grid time.

 

[Captain Yoghurtpot]

No problem fitting a second battery. Minimum 10mmsq cables connected Pos of battery one to Pos of battery two and Neg to Neg in the same way with a fuse in the Pos cable, or even better one at each end of Pos cable.
Solar panel connected to whichever battery is easiest and will charge both at the same time.
Two batteries and solar will more than double your off grid time.

Pappajohn, yer bloods worth bottling!
Thanks so much.
May seem like a simple set of questions to some, but I don’t like mucking about too much with stuff I don’t fully understand.
Had applied some logic to my thought process on electrics, but from what I have read , especially lithium set ups, best to ask a man who knows.
Cheers
oh, and I am not going lithium.
It’s lead acid to lead acid.
Going to keep it simple.

 

[Phill D]

Apologies for piggy backing on your thread Captain Yoghurtpot, I have been considering similar, I have a new 120ah gel leisure battery fitted but I also have a good 85ah gel.
I know it is preferable that the batteries were same size and age and as close together as possible.
I also have 140w solar panel fitted.
But the nearest I could fit the 85ah spare gel is approx a 2.5m cable run.
So with the batteries not being the same and the cable length I am not sure if it's either sensible or viable.

 

[pappajohn]

Battery size (ah) is irrelevant. Your eyes see two batteries but the system only 'sees' it as one large battery.
Age is a deciding factor though, older batteries have reduced ability to store useful power so the combined power may only be in the high hundreds of amps rather than the 205 you would expect.

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[Revolvor]

On a recent trip to the tip, someone had thrown out two nearly new plastic tool boxes which I retrieved. One, with cantilever trays is ideal for my new disc grinder + discs, spanners etc, but the other I have used as a battery box for a Varta LFD90 leisure battery.

Originally it was just for my electric outboard motor, but recently I have improved it to use as temporary extra battery capacity in the MH.

It now also has a volt meter, 50 amp Anderson plug with circuit breaker, a 25 amp Anderson connector for accessories and a small solar panel, an SAE connector for my battery chargers, and USB and 12v sockets.

I utilised home-made positive and negative bus bars, and also attachments on the battery terminals for croc clips.

I have a matching 50 amp Anderson connector wired across my two existing leisure batteries.
Edit - next job is to make a cover for the +ve terminal/busbar

 

[Phill D]

On a recent trip to the tip, someone had thrown out two nearly new plastic tool boxes which I retrieved. One, with cantilever trays is ideal for my new disc grinder + discs, spanners etc, but the other I have used as a battery box for a Varta LFD90 leisure battery.

Originally it was just for my electric outboard motor, but recently I have improved it to use as temporary extra battery capacity in the MH.

It now also has a volt meter, 50 amp Anderson plug with circuit breaker, a 25 amp Anderson connector for accessories and a small solar panel, an SAE connector for my battery chargers, and USB and 12v sockets.

I utilised home-made positive and negative bus bars, and also attachments on the battery terminals for croc clips.

I have a matching 50 amp Anderson connector wired across my two existing leisure batteries.
Edit - next job is to make a cover for the +ve terminal/busbar

View attachment 488817View attachment 488819View attachment 488820

Sounds interesting, have considered a "plug in" option but been concerned how the hab battery will react when it is plugged in to the system when needed.

 

[Phill D]

Battery size (ah) is irrelevant. Your eyes see two batteries but the system only 'sees' it as one large battery.
Age is a deciding factor though, older batteries have reduced ability to store useful power so the combined power may only be in the high hundreds of amps rather than the 205 you would expect.

Thanks for that, Would that reduce the life expectancy of the new 120ah battery do you think

 

[Captain Yoghurtpot]

Am currently perusing the web and advertised suppliers for a portable solar panel or folding panels.
Any recommendations or advice anyone.
Thanks

 

[Revolvor]

Sounds interesting, have considered a "plug in" option but been concerned how the hab battery will react when it is plugged in to the system when needed.

I will trip the breaker before I connect it, and I think that as long as the battery charge levels are reasonably similar, there should not be excessive current flow when a connection is made.

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[Captain Yoghurtpot]

No problem fitting a second battery. Minimum 10mmsq cables connected Pos of battery one to Pos of battery two and Neg to Neg in the same way with a fuse in the Pos cable, or even better one at each end of Pos cable.
Solar panel connected to whichever battery is easiest and will charge both at the same time.
Two batteries and solar will more than double your off grid time.

Dear Pappajohn
Am currently going to undertake this project over the festivities but would appreciate advice on size of fuse to fit and type.
Cable size will be 16mm.
Many Thanks