100AH LiPo battery separate from any other Tab item for 2 way fridge at night

Jake_Elwood_and_us

  I have 2-50AH LiPo batteries I picked up for another project. After our last boon docking camping trip with shade and storm clouds I realized we might be coming up short on battery supply. Our 2021 400BD has solar.

  I'm considering putting the two LiPo batteries in the under bed storage area and running wires to a switch near the 2 way fridge. The switch would be a 2 pole 2 throw with center off to select which power is going to the fridge. I would reroute the external solar leads to the new batteries and look into a portable 100 watt solar array with controller. I would also provide a charger and add a 120V receptacle to allow charging from shore power.

  This would allow me to save the main battery so we can go longer without running our generator or moving to a full hookup place.

  One of many ideas I have conjured up while hanging out with the Tab.

  One of which is a large water filter like we used to use while river rafting to fill our 7 gallon water storage jugs from a river and siphoning into the Tab when running low.

  Just haven't figured out how to do a portable wastewater treatment plant yet.

  Any thoughts before I start buying stuff and boring holes? Thanks!

webers3

I have a very similar setup using Jackery battery, if the house battery gets low I plug the fridge to the jackery battery, and if there is sun I plug in the portable solar panel into the jackery, works great, similar concept as yours, it  should work as well

Jake_Elwood_and_us

webers3 said:

I have a very similar setup using Jackery battery, if the house battery gets low I plug the fridge to the jackery battery, and if there is sun I plug in the portable solar panel into the jackery, works great, similar concept as yours, it  should work as well

Thanks, I think I'll do it!

pthomas745

Your 400 already has about 117 amp hours available, and solar. There is no need to start boring holes.  You can just carry an extra battery, completely separate from the trailer.

Many easy ways to do this.

https://tab-rv.vanillacommunity.com/discussion/7008/anyone-carry-a-spare-battery/p1

Denny16

I ran the fridge on our 2018 TaB 400 for three days and three nights of no electrical hookup (boondocking) and had no issues of running the 200AH AGM battery down.  The 193-watt solar panel on the roof parked partially under a small shade tree, still managed to recharge the overnight drain by mid day, and keep up with daytime load.  We also ran the Alde two nights, it was in late October in NorCal, so less sun than during summer, and was cold in the evening.  The 200AH battery only used 15-20% of its charge overnight.

I would not worry about the newer 2-way fridge running down the battery lower than an average day sun would be able to recover the charge.  You could even go a cloudy rainy day, with two nights and a day, without drawing down the battery bast 60-50% of its charge.  

If you want some backup, add a MC or a Anderson connectors to a no 6 cable attached to your battery distribution box, and route it into the rear storage locker.  The lithium battery should fit in there too, and just plug the lithium battery in when the AGMs start getting to 60/50% and the Lithium will boost the system back up.

Jake_Elwood_and_us

Denny16, so it is ok to mix the AGM and LiPo batteries? That was why I came up with this idea to keep them separate because I thought it was not a good idea, especially when it comes to charging.

In full disclosure I'm still waiting for my battery monitor to show up so I can keep a better eye on what is happening. On our last trip I simply used a multimeter and it showed going as low as 11.9 one morning. Hence the idea to have a second system but I think I will wait until I have the battery monitor and can see what is really happening. Getting ready to leave on a 10-12 day trip next week and the battery monitor will not be installed. The first 6 days will be without shore power but should have good solid summer sunshine all day.

Denny16

Jake, first, you should not need the spare lithium batteries, as your 224AH of AGM batteries will keep you going, and the solar will recharge any night time drain on the batteries, unless you run into a week of lousy dark sky weather.  I would not mix lithium and AGM long term or in a permanent setup, nor try to charge them whilst connected, but for a short period to get some additional power, it should work.  The lithium batteries will charge the AGM a bit, until both battery banks are the same voltage and provide some adding WH of power. 

Once you get AC shore power or solar charging going again, I would disconnect the lithiums, and charge them back up separately.  As for the battery monitor, get a small volt/ohm meter and use that to occasionally check the battery bank.
 Cheers 

Jake_Elwood_and_us

Denny16, thanks for the feed back.

Sharon_is_SAM

This is from lithiumhub.com:

Can you put a lithium battery in parallel with an AGM battery?

Yes, you can. However, the Lithium battery will drain into the AGM as the resting voltage for AGM is lower than the lithium. That would take several weeks but if charged and used weekly the two types of batteries can be put in parallel.

Jake_Elwood_and_us

I'm learning so much, thanks to everybody and this forum.

screwlose

Really the difference between Battery Voltages is maybe 1/2 a Volt
Is that really a big difference? Not an easy answer...

Battery Tender's website has a pretty good writeup, it takes a bit to read through it all but is well worth it, it reads pretty easy, not a lot of Tech Terms, so is good for General Public

https://www.batterytender.com/the-basics-of-electricity-new

Denny16

Nice find @screwlose. I agree a .5-1.0 VDC difference is not an issue, batteries will eventually equalize after a load is placed on them.  You could connect the additional battery in parallel when you arrive at the Boondock camps site, and with both batteries charged, you would have additional AmpHrs of power in cloudy sky situation where solar might not keep the AGM bank charged.  

This would buy you some time wait for the sun to come back out.  When it does, I would disconnect the additional lithium battery, and let the rooftop solar charge the AGMs, and use a portable panel setup,to,charge the lithium battery bank.  This way both will get an optimal charge.
 Cheers 

Jake_Elwood_and_us

Denny16, I'm thinking short term on this next camping trip connecting my 2-45AH 12 volt LiPos in parallel and connecting them via the solar port on the outside of my 400. It looks as the wire gauge from the solar port to the existing batteries is maybe 10? Since these 2 extra batteries would be adding some extra power do you have an opinion on this setup?

Denny16

Jake, thst should work fine, if your AGM bank needs a boost, connect the lithium.  A AWG 10 wire is good for 20 amps on a short run like this, so it should be fine.  Is the SAE fused?  If not consider adding a fuse (20amps) between the battery and port.
 Cheers 

Jake_Elwood_and_us

Yes, the SAE has a 30amp fuse at the battery fuse which is accessible from the storage compartment. There are two actually, one from the rooftop solar and this one. The 7 pin positive lead runs to the WFCO load center. I just tried it out, paying close attention to the positive/negative on the SAE receptacle. Since both batteries are full I didn't notice anything so I may run a test tomorrow.

Denny16

Easy enough to replace the 30-amp fuse with a 20 amp. fuse. 

Cheers