Using alternator to charge batteries

[DPL646]

I would like to avoid having solar to charge four Optima D31M deep cycle batteries. Has anyone hooked up their alternator to charge their battery array? I would also like to have an option to plug in via an extension cord to charge as well. Any advice or tips would be appreciated.

 

 

 

[Beta Don]

The 2014's and later come with a 150 amp alternator, so there's certainly power available for other uses

To recharge from 120 volt power, you'd need a battery charger capable of getting the job done.  A 30 or 40 amp 'smart charger' like they use on boats is pretty expensive  -  $350 to $450.  If you get one of those, you could install an inverter in your TC which would power the battery charger using alternator power  A 750 watt inverter would put out enough 120 volt AC to run that sort of charger

I mounted a 500 watt inverter in the aft compartment of my TC and I use it to recharge two Segways while we drive.  Works like a charm!

Don

[thx138]

It's very simple to do a basic setup to charge the batteries off the stock alternator. You can use an IBS relay and appropriate wire size for the run (there are calculators online for that) but I would run in line fuses at each end of the setup.  https://www.sierraexpeditions.com/index.php?l=product_detail&p=2193

[Beta Don]

If he were to attempt to recharge four deep cycle Optima batteries in parallel directly from the alternator, a 'proper sized wire' would be VERY large  -  Those batteries would probably like more than 50 amps each if they were deeply discharged and the wire size would be larger than the vehicle's battery cables

Since he wants 120 volt recharging capability which would require a battery charger, IMO it would be simpler and safer to plan on a set-up where an inverter  powers the battery charger and that would limit the current to a safer level  -  Whatever size battery charger he buys.  A 20 or 30 amp charger powered by an inverter could be done with much smaller wire sizes

Don

[Fifty150]

I encourage the build.  Do.  Post photos.  Inspire the masses to follow in step.

[chong]

I have both in my Van. My battery bank is 2x Optima Yellowtop (each battery is 75Ah). I have them connected to the Alternator via a Blue Sea Systems Add a Battery kit. I can also charge them via AC with a NOCO Genius 10a charger. 

I've documented my build here: Vincent VanGoing 1.0

[dinocarsfast]

I am building mine with the auxiliary batteries connected to the vehicle charging system too. One thing to consider is the alternator output is very low at idle and will barely charge the batteries, 

This link has has the output curve of the alternator;

Ford Fleet charging system documentation

So with my 2.5 engine at idle 600 rpm and 2.76 pulley ratio the alternator will spin around 1700 rpm, producing less than 100 amps.  

Estimating some of the main loads, headlights that dont yet switch off in my van, 55w each equaling 10 amps and with losses and other loads I dont expect much more than a couple of amps for the auxiliary batteries unless the vehicle is moving and the engine is spinning.  Though with an auxiliary battery charger it might be able to charge auxiliary by stepping up the voltage and drawing more current than what the alternator is producing but this will only be draining your main battery if alternator output current is not enough.

The overdrive pulley solution.  I plan to install one of these http://www.cpgenerator.com/overdrivepulleys.html it might put a little higher load on the bearings but I dont rev the engine very high anyway because I try to save fuel so Im not to worried.  Also if the bearing go bad and it starts to make noise, alternator replacement is easy and it will be a good excuse to install a higher output unit.  

I am really curious why you need 4 optima deep cycle batteries I have heard from people that use that much reserve power for 5th wheel rigs and with a lot of loads and live completely off the grid.  I would also suggest a battery monitor like this https://www.solar-electric.com/trtmbamosy1.html. You install a shunt resistor directly to the battery and it monitors how much current goes into or out of your battery and accurately monitors your charge state and power usage.  With a battery monitor you will be able to use a lot more of your batteries and they will probably have less wear because you will better be able to avoid overly discharging them.  

 

Keep everyone posted on your progress and what you decide to go with. Don't be like me, I need to make a build thread but I my build has been progressing slower than I had hoped.  

Edited August 27, 2017 by dinocarsfast
clarification

[G B L]

The way the alternator Charging is controlled is buy voltage.  If you get the right set up the even with the Headlight draw the house batteries will get most of the Charge with the right regulator the engine battery will only get Just what it needs .  All the batteries Step back the charging amperage  quite rapidly as the Battery voltage rises.  The only way to get the batteries fully charged with the engine running is time, lots of time

[dinocarsfast]

Sorry, to clarify the setup that I was describing I was assuming that you would be using a dc to dc charger like these; http://amsolar.com/rv-solar-panel-kit/charge-controllers/  These chargers are marketed for rv solar setups but a photovoltic cell is just a another power source and if you connect it to your vehicle battery the charger will charge your auxiliary batteries just the same as long as it is expecting a 12V source.  Without a charger like this an auxiliary battery setup will be not be fully utilized and your auxiliary batteries will never get charged and store only a fraction of the batteries advertised current.  

Many people connect auxiliary batteries directly to the vehicle positive, this in my opinion will cost a more because the batteries will never fully charge and you will need multiple batteries.  And being that they are usually kept at a low charge level they will need to be replaced more frequently.

One difficulty with a charger like this is that you only want it to charge when the engine is running, so you will need a switch.  Otherwise you could discharge your vehicle battery while trying to charge your auxiliary battery if the engine is not running.

If my explanation is not clear or missing anything please let me know I will be glad to clarify.  

[G B L]

If You you get the right smart regulator for the vehicle Alternator the house battery charging function is automatic.  The engine battery and the house battery will get the proper charge from one Alternator mounted on the engine.  If you added a solar function to the house batteries the solar charge controller would blend that charging into the mis

 

Categories : Electrical : Alternators : Voltage Regulators

 

 

 

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[chong]

On 8/27/2017 at 6:25 AM, dinocarsfast said:

I am really curious why you need 4 optima deep cycle batteries I have heard from people that use that much reserve power for 5th wheel rigs and with a lot of loads and live completely off the grid.  I would also suggest a battery monitor like this https://www.solar-electric.com/trtmbamosy1.html. You install a shunt resistor directly to the battery and it monitors how much current goes into or out of your battery and accurately monitors your charge state and power usage.  With a battery monitor you will be able to use a lot more of your batteries and they will probably have less wear because you will better be able to avoid overly discharging them.  

I have 2 batteries. The design requirement was to be able to run 2 heated blankets for 8 hours (the coldest overnight temp we've slept in the van was -18F). I put together a system to do that while running a powered cooler.

A battery monitor is definitely on my list of upgrades for the future.