Reddit mentions of 12V Dual Battery 140A Smart Isolator (VSR Voltage Sensitive Relay) for Auto/Boat/RV

I can't answer all of your questions but I can say that yes the batteries should have been left on a trickle charger over the winter.
The symptoms all seem to just point to dead batteries, hopefully after charging for a couple days they'll regain their ability to hold a full charge.

As far as jump starting, I see no reason why you would not be able to, as long as your truck's battery can provide similar cranking amps.

For my merc 5.7, I use a dual purpose for starting the engine and deep cycle for boat electronics. I've got them wired with this guy: https://www.amazon.com/gp/product/B00400IYTK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 that way both can charge when the engine is running and I don't have to worry about the boat electronics draining my starting battery.

Thanks for the reply. I was able to get a look at the batteries today to check the connections and noticed one seems to have been leaking. I removed it and so far the system works fine on the remaining battery.

So I'm thinking it developed a crack OR the leak is due to overcharging. How can I figure this out?

Maybe you can help me answer this question: If my batteries were topped off and then I drove for 10 hours, would my battery isolator be overcharging the batteries? And one of them finally quit?

This is the smart isolator I'm using-

https://www.amazon.com/gp/product/B00400IYTK/ref=ask_ql_qh_dp_hza

> but at that rate I'm better off charging my batteries with my diesel's alternator

Yep. I frequently ask people on this sub why they think solar is so important when they're driving around in something that generates electricity already. Solar is expensive. It doesn't work in Seattle except for three weeks in August. Unless you're in the desert southwest, you need to have sufficient battery capacity for multiple days without sun which means you need an even bigger solar panel array to recharge that battery pack on the 2 sunny days during a two week period of overcast and showers.

Unless the van is parked somewhere for days and days without moving, just charge the house battery from the alternator. Even if it's parked on a sunny day, there's a huge incentive to park it in the shade to prevent the interior temps from killing anyone inside.

Using the alternator is easy. The absolute brute force, quick-n-dirty, cheap way is to run a #2 or #4 gauge wire from the positive terminal of your your van's battery to the positive terminal of your house battery through a simple switch and a high capacity (100A) fuse.

Under $10 crude switch from any auto parts store: https://www.amazon.com/Post-Battery-Master-Disconnect-Switch/dp/B001N729FS/ You use this to 'disconnect' the wire between the batteries when you park. This prevents that 60W fan you're running 24/7 from running down your starter battery. Get a better switch as your budget allows.

Better is an 'isolation relay' - there are two basic kinds. The inexpensive kind https://www.amazon.com/gp/product/B005JCX8OY/ requires that you also find a 12v power source that goes active when your ignition is turned on. This powers the relay to connect your house battery to the alternator/starting battery. It's not a big deal, but possibly a small hassle. Any Napa, Reibes, Pep-Boys, Autozone, etc auto parts place will have one.

Or, an automatic type that senses when the voltage on your starter battery rises due to the alternator and then automatically connects your house battery so it gets charged, too. https://www.amazon.com/gp/product/B00400IYTK/ You take the 12v cable from your van battery to one terminal. The 12V from your house battery to the 2nd terminal. And, the last terminal goes to ground.

BTW, I wasn't trying to 'burn you' but rather put some realism into your needs. At least you didn't mention electric heater or electric air conditioning like some folks do. For heating or cooking, gas/propane is the practical way to go. (There are some great, BUT EXPENSIVE, diesel heaters that can tap into your van's fuel system).

For air conditioning, there isn't any van-sized alternative other than a gas powered generator or an electrical outlet near the van.

Good choice on the fridge. And, you're right - it's not a 'now' sort of requirement.

Those battery powered LED things last forever. If you haven't bought any yet, try to get ones with diffusers - intentionally stay away from the brightest ones you can find. The issue is that in the small confines of a van, they just sear burn marks in your retinas. 'dimmer is better' I have these - multi brightness, magnetic stick on to my van's metal interior: https://www.amazon.com/gp/product/B01H731UNS/

I got the non-rechargeable ones but use Amazon Basics Eneloop- equivalent rechargeable AAA batteries: https://www.amazon.com/AmazonBasics-AAA-Rechargeable-Batteries-12-Pack/dp/B007B9NXAC/ and a USB recharger for them sort of like this: https://www.amazon.com/gp/product/B00PZ6V99U/

I have one of these. You do not want this 2 ft from your eyes in a van: https://www.amazon.com/BUYGO-11-LED-Outdoor-Lantern-Camping/

Alternators give out anywhere from 60-130 Amps, depending on what model came with your van. A single 100W solar panel, laid out flat, is going to produce in the neighborhood of 80W for about 5 hours on a good sunny day, or roughly 400W per day. Even the smallest available alternator will produce twice that much energy in an hour of driving per day.

If you are going to charge your "house" battery off of your alternator, be sure you get a battery isolator circuit that will prevent your house electronics from draining your starter battery. Something like this: http://www.amazon.com/Smart-Dual-Battery-140A-Isolator/dp/B00400IYTK

This fits the "breaker or switch" suggestion perfectly and is exactly what its for, albeit a bit more expensive than a manual switch ;P

https://smile.amazon.com/dp/B00400IYTK/

Cool, I plan on using one of [these] to isolate the two. (https://www.amazon.com/gp/product/B00400IYTK/ref=crt_ewc_img_dp_1?ie=UTF8&psc=1&smid=A1Z9PJN6YB119)

> I need to take a look and see if I have the space for it under the hood (probably) but would be best if I could use a battery box in the bed of the truck.

Either way works, but it's a lot more fairly expensive wire to get back to the bed.

This is what I'm using (or something really similar): http://www.amazon.com/Smart-Dual-Battery-140A-Isolator/dp/B00400IYTK/ref=sr_1_8?ie=UTF8&qid=1416450132&sr=8-8&keywords=battery+isolator

Yeah, cheap chinese stuff. But it's been fine for a couple of years so I don't feel like it owes me anything. Expect that much more in properly sized cable and cable ends.

I had this and all the accessories on a previous plow truck: http://www.hellroaring.com/bic75150.php

It's really nice, but more than I wanted to spend for the foul weather/off road toy the new setup is on.

One thing to keep in mind is that normal lead-acid batteries require charging over long periods of time. If you drain your lead-acid house batteries to 50% charge (which is the maximum for deep discharge lead-acid/AGM) it will take hours of charging to bring them back up to 100%, and many people just don't drive that many hours. That's why there is usually solar which will charge all day long.

Nowadays, you can also buy Lithium Iron batteries, which don't suffer from being part discharged, and which charge much faster. But that's a bigger up-front investment.

As for how you hook up your battery pack to the alternator - you need a smart battery isolator that first fills up your car battery, and only then switches to send charge to your house battery. To keep your voltage drop to a minimum, you need thick wires to go 18 feet (which is 36 feet total, as the number that matters is the full round trip, not just one way.)

https://www.amazon.com/Smart-Battery-Isolator-Voltage-Sensitive/dp/B00400IYTK for example.

Maybe something like this? https://www.amazon.com/Smart-Battery-Isolator-Voltage-Sensitive/dp/B00400IYTK

Dual battery you will at least need this:
https://www.amazon.com/Smart-Dual-Battery-140A-Isolator/dp/B00400IYTK

https://www.amazon.com/Scoshe-EWFH-Single-Fuse-Holder/dp/B000KIR8M0/ref=pd_bxgy_263_img_2?ie=UTF8&psc=1&refRID=Y4S68RZF6CFYXAZBN52B

https://www.amazon.com/Absolute-ANL200-2-Pack-Fuses-Plated/dp/B005EUTLYW/ref=pd_bxgy_263_img_3?ie=UTF8&psc=1&refRID=Y4S68RZF6CFYXAZBN52B

Then its on to pwm vs mppt charge controller
and a panel and wiring.