Batteries in a small van

[Trebor English]

How do you make sure you always have enough charge to start the van?

I pay attention to the amount of use and the weather.  If it is sunny then more use is ok.  If it has been raining all day and at 4pm only 5 amp hours have been collected then there's no computer or cell charging.  Even on low power days the MaxxFan runs on low while cooking.  On a good day I have 14.6 volts by 9 or 10 and use all I want.  I don't have a jump pack, lithium or agm.

I recently watched a video about solar electric in a house in Arizona.  The guy claimed that if your solar is the right size and working correctly you just use it without ever giving it a second thought.  If you have to think about it you should get it fixed.  That approach works for him.  I have only one 75 amp hour battery for starting and everything else and one 100 watt panel.  I have never had a failure to start or had to wait for the solar to charge before I could go.  I pay attention.  Monthly I check water and specific gravity.  Daily I watch amp hours in and curtail use accordingly.

 

[frater secessus]

How do you make sure you always have enough charge to start the van?

Run loads off the controller's LOAD output, and set the Low Voltage Disconnect to whatever voltage you want.

 

[hausmutti]

Run loads off the controller's LOAD output, and set the Low Voltage Disconnect to whatever voltage you want.

I’m not sure what that means, but I think it answers a question I had.  Is there a thing that you could set that won’t let the battery get too low?

 

[John61CT]

It may be better to start your own thread, give the details of your setup.

Some solar controllers include a LVD feature, give a load output with limited current capacity that cuts out when volts gets too low.

You can also buy standalone LVD and wire the to protect the whole bank say at 11V, and a small on on say a fridge to cut that out at 12V.

Some fridges have that built in.

 

[Trebor English]

Is there a thing that you could set that won’t let the battery get too low?

My solar charge controller has a setting that causes it to turn off the load output if the battery gets that low.  It has another setting that the battery has to get up to for it to turn back on.  

They make things that do that without a charge controller.  Search for "low voltage disconnect" on Amazon.  You could use a cheap solar charge controller to do that even with no solar panels.

 

[frater secessus]

I’m not sure what that means, but I think it answers a question I had.  Is there a thing that you could set that won’t let the battery get too low?

That's what a low voltage disconnect does.

 

[Jmel]

I think I'm going to outline my setup in another post, but on topic -

I purchased a low voltage disconnect device, capable of running 30 amps at 12v. It has 4 settings for both disconnect and reconnect voltage. I cannot attest to how well it works yet:

https://www.ebay.com/itm/Low-Voltag...V-30Amp-Based-on-MCU-and-MOSFET-/372100359203

It uses mosfets, and relieves the issue of "chattering relays" from what I've read. There is a delay between the actual low voltage condition and the power cut.

I also purchased separately a 12v low voltage alarm. This way, I can get a warning before a low voltage disconnect will take place.

 

[highdesertranger]

the problem I have with all these disconnects and alarms is they all take a little power to run. in a situation were we are trying to conserve as much as we can they are just eating power. I say just pay attention to what's going on. highdesertranger

 

[frater secessus]

Consumption is generally measured in milliamps.

 

[95Astro]

What about this AGM battery? You can get them at Amazon...free shipping if you are a prime member.
https://www.amazon.com/Universal-Po...8&qid=1509000193&sr=8-2&keywords=ub121000#Ask

 

[John61CT]

I doubt they last more than a few hundred cycles at 50% DoD.

Nowhere near the value of 2x 6V FLA Duracell/Deka GCs from Sam's Club or Batteries+

Never buy from a manufacturer you can't pick up the phone to talk to their tech support, get detailed performance charts, charging specs, the equalization protocol etc.

Among AGM I only recommend Odyssey, Lifeline and Northstar.

For FLA: ​Rolls/Surette, Trojan, Deka/East Penn, U.S. Battery, Crown, and Superior.

And most of these make starter type and "dual purpose" as well as those truly intended for deep cycling, so specific line/model matters.

 

[Gideon33w]

Those Duracell deep cell units from Batteries+ are surprisingly good for the money.
If we do an off-grid ranch again I'm going to use them for our power bank.
That said, gotten away with Walmart cheepies so long as you aren't constantly taxing them.