Simple no build single battery

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Trebor English

Well-known member
Jul 20, 2016
Reaction score
Melbourne, FL
My van has two plastic Sterilite 3 drawer units.  They are tied in place using coat hanger wire like a wire twist tie on a loaf of bread.  My fridge is tied down using a 1 inch wide cargo hold down ratchet strap.  The strap hooks into the floor things where the second row seats used to attach.  I have a plastic shelf for the 2 burner camp stove.  Everything is intentionally just put in with minimum "build" because the van is a 1999 with 200,000 miles.  I can switch my stuff to another van with minimum work.  Also, I'm lazy.

I wanted the same sort of installation for my electrical stuff.  I started with a plastic box on the floor containing a pair of 35 amp hour AGM mobility scooter batteries (400 watt hours each) and an inverter.  It never really charged well using the van alternator plugged in to a cigarette lighter socket.  The wire was too long and too skinny.  After a couple of months I gave it to someone who really needed it.  She was taking a class online and needed to use her laptop.  That box was like a double Suaoki 400 watt hour box except it could really do 400 watt hours with 2 batteries.

Then I just used the van battery to run my electric shaver, 3 minutes per day, 1.5 watts 120 vac, 1/4 amp 12 volts into the inverter and to charge the cell phone, 2 amps for 1 hour daily.  I have a laptop that only needs 12 volts rather than the typical 19 volts but I have figured out how to do everything using just the phone.

The original van battery was a Ford special extra small capacity at a premium price.  It had a reserve capacity rating of 100 minutes.  So 100 minutes divided by 60 times 23 amps is 38 amp hours.  The 50% recommendation is for deep cycle batteries.  My experience is that with a starter battery 5% with occasional 10% discharges shortens the battery life a little bit.  The 36 month battery made it only to 35.  That's not terrible.  10% of 38 is only 3.8 amp hours.  That means two days of shaving and phone charging is about the limit.  

I got a group size 24 deep cycle 12 volt trolling motor battery.  I thought that was the biggest battery that would fit in the original location.  

Of the group size 24 batteries I got the one with the least cold cranking amps and the most amp hours.  This is not advertized as marine starting or dual use.  It was $80, I just looked and today it is $60.  The original Ford group size 59 is $100 so I saved $20.

It is rated at 75 amp hours.  Since it is not a golf cart battery my opinion is that good life will allow 25% discharge rather than 50%.  I've been using it 2 years.  25% of 75 amp hours is 18 amp hours.  That's a 10 x improvement over the original battery.  It really is a deep cycle battery.  A maintenance free starter battery has calcium in the lead alloy to save water.  This battery uses 20 to 30 ml of distilled water per cell per month.  This battery has lead antimony alloy plates consistent with the water use.  It gets 10 minutes per month of watering.  Otherwise it will be shot in 4 to 6 months.

Since this battery is in the original location the alternator is connected to it normally and the charging is normal.  There is no solenoid or VSR, voltage sensitive relay.  There is no custom cable with wire bigger than your thumb.  If it is deeply discharged idling to charge it will result in a hot alternator.  I don't deeply discharge it and make it a point to drive right away after starting the engine.  I have had no problems.

That still requires regular driving to recharge.  I got a cheap $15 charge controller and a $108 100 watt solar panel and attached it to the luggage rack.  The wires are run through the side door on the driver's side.  The rubber door seal works to keep out rain and hold the wires.  No drilling and sealing for the wire.  

To connect the solar to the battery I have an AWG #6 wire, like pencil size, from behind the driver's seat up to the battery.  

Suitcase folding panels typically have big clips that connect right to the battery.  That would mean no extra wire to connect the solar.  You just open the hood to connect directly to the battery.  

Now I can stay in one place without driving until I run out of food or water.  

I switched my ice chest for a fridge.  Since my electricity supply is small I put together a DIY unit set up for minimum electricity use.  I started a thread to describe it.  

Basically it has a little freezer compartment and I fill that with 8 pounds of water/ice.  It only runs during the day when it is sunny to minimize battery use.  The ice keeps it cold 3 days without any electricity and it uses 6 to 13 amp hours per day, 7 day averages, depending on ambient temperature. 

I saw a you tube video about an Alpicool.  They have a C15 and C20 that are 15 and 20 liter, very small, and have a very low energy consumption. 

From posts I have seen here it looks like smaller Whynter, Truckfridge, and Dometic run 20 to 30 amp hours per day.  With a 200 watt solar and a 75 amp hour battery, 18 useable, this won't leave margin for rainy days.  If those fridges will really perform at the 10 to 15 amp hour range it should be fine.
I got a group size 24 and that fit easily.  I made a corrugated cardboard battery sized model and closed the hood on it to see if it would fit.  Places like AutoZone sell battery hold down things that go over the top of the battery.  That requires drilling 2 quarter inch holes.  

The bigger the battery the more effort it will take to fit it.  If your battery choice is moderate, it may just fit with no more than a new hold down.  This will take serious thinking.  

My Ford Windstar has a pair of computers, front and rear.  Every time a door opens or closes a bunch of current runs, about an amp, for a half hour.  The bigger battery and the solar charging handles that.  The small original battery didn't do well with that.  I installed a battery disconnect to prevent that from discharging the original starter battery.  You may have loads that will mess with the starter battery.  A Suaoki or Yeti won't keep your starter battery charged.  

I got LED lights to replace all the light bulbs in my van.  Some people don't like LEDs because of the color or slightly lower brightness.  My thought is that they are nicer than no light.  

I did do a "build" thing.  I cut a 14 inch square hole and installed a MaxxAir exhaust fan.  I love it.  With the built in cover you can use it in the rain.  I put the stove below it so cooking steam and smells go right out.  I tried to avoid the "build" but I couldn't figure out any other way to get an exhaust fan.  A sunroof would work but I haven't seen that in vans.  The only electric thing that I use much when the sun isn't shining is the fan.  

So, if you want a substantial amount of electrical energy you need a pair of golf cart batteries and 200 to 300 watts of solar and solenoids and cables.  If you are willing to seriously limit your use of electricity you can get by with a low cost battery upgrade.  For extended no driving stays a modest solar panel and charge controller will work.  

If you have a special battery for non starter only use you can run it down to 10 volts and your van will start.  Your battery will die young if you do that.  If you pay attention and only have one battery you get long battery life and reliable starting.  You can get a low voltage disconnect device for $10 if you can't remember to turn off the lights.
Fantastic detail, sir.  Thank you.

Of particular interest is your idea of making your engine battery, your house battery as well.  The Discoverer I'll be remodeling, in planning stage noiw, doesn't have any room to spare for inside battery and gizmos.  I  would keep an eagle eye on battery level, and I also have a battery pack. My van is under thread Conversions, titled Methuseleh. I spelled it wrong when I started the thread :(

I hope a really good battery would fit in original space, a battery with no maintenance. (No water addition, etc.
Thanks, Max
Several years ago Sternwake had two batteries.  His starter battery died and he didn't replace it.  He just used his 90 amp hour Northstar AGM for starting and everything else too.  In order to fully charge it he replaced the voltage regulator.  With a volt meter and a knob on the dashboard he could coax the alternator to actually charge the way he wanted.  

Without the enhanced voltage regulator a deeply discharged battery will not get to 100%.  With my one battery system I have fewer driving days than solar only days.  I have my solar charge controller set high enough to get the battery charged and usually don't depend on the alternator.  

With a lightly used battery a half hour drive will put back what was used to start the engine plus a couple more amp hours.  A deeply discharged battery won't be refilled with a half hour drive.
DannyB1954 said:
You also can buy an automatic battery disconnect
Thank you Danny, I added it to my Amazon list.  If I ever DO go "on the road" I'll miss my frequent Amazon deliveries to my door. ::) Max
"Just passin' through"
I have a low cost flooded lead acid battery.  I add water and test with a hydrometer.  That takes 10 minutes per month.  If you get a sealed battery, AGM, gel, or maintence free (flooded, calcium alloy), you must either pay $150 or so for competent battery monitoring equipment or you fly blind.  Just measuring the voltage doesn't tell you how full the battery is.  
A hydrometer for $10 measures the density of the electrolyte.  That tells you how much is sulfuric acid and how much is water.  I know my battery is getting fully charged because A) the hydrometer shows 1.275 or more, B) when it is charging late in the day the battery is making bubbles, and C) water use indicates electrolysis is happening when the battery is getting charged more when it is full.  All three, A, B, and C.  Note, I didn't mention open circuit voltage, resting voltage, or voltage under load.  
When you discharge a battery the H2SO4 sulfuric acid leaves sulfate ions on the plates.  Actually, once the surface is covered the sulfate goes into the lead plates.  If you recharge the battery to 95% the sulfate that is most deeply buried in the lead remains.  When you discharge and recharge a few times that 95 % level becomes the new maximum.  5% of the capacity becomes lost forever.  Lather, rinse, repeat and you lose another 5%.  When your 100 amp hour battery is only a 75 amp hour battery that 50 amp hour discharge is way more than 50%.  Then you get a downward spiral.  You keep recharging and the voltage comes up but your capacity continues to drop.  

AGM batteries can't be watered.  You must treat them like a princess.  You can't under charge or you lose capacity.  You can't over charge or you lose water that you can't put back.  

Some AGM batteries are close to the price of lithium.  Lithium don't have the lead acid disadvantages of very slow finishing charge and the need for frequent 100% charging.  

If you must have sealed batteries I highly recommend maintenance free for starting and something else for your house battery.  I do not recommend a single battery that is sealed without whatever electronics are necessary to monitor and charge according to all of the details of the manufacturer's specification.  That includes having a way to measure the charging current and using the tapering of the current to control the charging.  

It is my opinion that a simple single battery scheme depends on the battery being flooded.  A $15 PWM charge controller like the one I have is incompatible with AGM.
Trebor English said:
I have a low cost flooded lead acid battery.
Bit by bit, I'm getting educated on batteries et al. Howmuch my ancient brain retains, is another thing.  :idea:   I try to look for photos and links to save under categories.

How about a Lithium Ion Battery?  I'm willing to pay more just to get away from maintenance.  The post suggesting to have just 1 battery may not apply to me.