another newbie perfect storm

  • AGM batteries?  check
  • massive inverter?  check
  • wants to run A/C off grid? check
  • wants to charge batteries from idling vehicle?  check

I’m going to get some of the Renogy AGM deep cycle batteries. Yes, I know wet cells will give me more bang for the buck, but my situation does not allow for them. At all.

I’ve already got a 2000/4000w inverter.

The inverter will power a CPAP, charge a power wheelchair, and even run the AC so the lines need to be pretty robust. I was thinking I might skip the breaker box and run a direct fused line from the batteries to the inverter instead of going through the breaker box.

I also need to leave whatever opening I need to add solar at a later date, though I have little idea of what making accommodations future solar looks like.

Before you ask, I know that the AC will eat the battery power pretty quickly. My current plan is to have an auto-starter on the van that will track the battery charge and, when the charge hits 50%, will turn on the van and start charging the batteries and running things off the alternator.


Let’s take these in order.

AGM batteries cost about 2x as much, generally have less capacity and lower voltages during Absorption.  I would like to strangle the first youtuber that started telling people to buy AGM for vans and campers.

Inverters are problematic for both philosophical and practical reasons.  They encourage people to think that inverters pull power from thin air, forgetting that it comes from the battery bank (at ~10x the amperage).  “All I need is a giant inverter and I can run everything I want!”  No, you probably can’t.   And inverters waste some power as heat;  most rules of thumb mention 10% losses at their full efficiency, and much more when underloaded.

Off-grid A/C is possible but not practical. Most people don’t have the cash, skills, or stubbornness it takes to get it working.

Charging from an idling alternator is bad idea because:

  • it’s hard on the alternator (no air movement to cool it).   Doubly so with AGM since charging current can be higher than with FLA
  • it’s hard on the engine, particularly direct injection engines
  • it’s unlikely to get lead-acid batteries fully charged, because Absorption takes a long time at voltages most stock alternators will not produce.


The good news is many folks chimed in to try to save the poster from himself.  One problem with the greater awareness of vandwelling is there are more clueless folks in the mix now.





Honeywell swamp cooler and a $100 mistake

41jcgmfxl6l-_sy90_Just before going FT I ordered a Honeywell CS071AE 176cfm evaporative cooler from amazon to help make summer in the desert bearable.  They humidity in the ELP high desert is quite low, a great candidate for evap cooling.  The vast majority of homes here have evap cooling units on the roof instead of A/C units.  In a residential setting it takes about 10x the electricity to run an A/C than evap. Continue reading “Honeywell swamp cooler and a $100 mistake”

freaking A/C questions

IMO the main mental errors made by newbs are the assumptions that:

  1. it is normal to have A/C in a vandwelling context
  2. having a big inverter means you have an endless source of power


Here’s the most recent example from a user’s first post:

Vehicle: 2003 ford e350 5.4 gas high top extended full windows
-mainly what i want from this electrical system is to be able to run a 5000btu window air conditioner through a 2000watt modified sine wave inverter through the night

Nope.  I’m not going to respond to those anymore.  I’ve been skipping a bunch of replies lately;  feels like Sisyphus pushing the same unrealistic expectations up the hill day after day.




garage sale finds: ceramic heater, vacuum

I’ve been looking for a couple items on the thrift store / garage sale scene.

ceramic heater

s-l1000My understanding is that ceramic heaters put out the same amount of heat but the elements themselves run at a lower temperature.  Supposed to be safer.

I wanted one that had at least one setting below 1000w, since that is how much of 15A shore power I allot for non-charging loads.  (The converter consumes the rest)

Mission accomplished:  Patton PCH4199 ceramic heater for $2.  I ran it on the kill-a-watt and it has a low setting of 750w.


il_570xn-722995734_lyp2I have heard many ‘dwellers say it is easier to vacuum than to sweep in a van.  I was thinking about one of those “bucket head” wet-dry vacs but ran into this little Dirt Devil for $2 at the same garage sale.  Works fine.

I got a dinky 300w inverter to run cordless drill chargers and I’ll run this off that if needed.  The inverter claims to be PSW but I suspect it’s a smoother MSW.