battery bank charging from alternator

anarky321 · Dec 3, 2015

the question is specific to a Chevrolet Express van but is really applicable to any vehicle
i want to set up a battery bank of about 10kw (probably less because of weight), which can be done in several ways but i want to do it as series-only, as an example lets use the Trojan IND17-6V - 925AH - a pair of these is sufficient, aside from the weight concerns

the problem is - i want to be able to at least partly charge from the alternator AND be able to charge from AC through an IC - 250A-300A alternators are available for this model van, but how well would this work?

if you have (2) 6V in series this is basically a dual battery setup because the circuit sees it as 1 12V battery in addition to the main battery but the alternator is obviously not built to 3-stage charge deep cycle batteries and has an internal regulator

is this a doable setup by using a battery isolator an an inverter/charger to also add AC charging?

SternWake · Dec 3, 2015

Yes. Look into the Blue seas ACR, or the surepower1314 for voltage sensing automatic solenoids.

One can use a Dumb Solenoid and trigger it a multitude of ways.

I'd recommend avoiding Diode based isolators, those with large finned heatsinks.

Take power right from the alternator(+) stud, instead of the engine batteryfor the solenoid. Fuse properly to protect the thick wire.

I'd use no less than 2awg.

A huge capacity of depleted battery bank is basically an overload on almost any charging source.

The Alternator will get extremely hot and wear out quicker.

Consider making a cold air intake to blow on the alternator to keep it cooler and last longer, and be able to produce more amperage whilst working hard.

Voltage regulation plays a HUGE part in how much the alternator will deliver. Voltage is electrical pressure, the higher the pressure difference, the more amps can flow from source( alternator) to load( depleted battery).

The vehicles voltage regualtor is designed around keeping a starting battery topped off, but more importantly not overcharging the slightly depleted starting battery. It is not designed for maximizing charging current into another set of deep cycle batteries.

Whether you can use an external voltage regulator in your vehicle, is unknown to me, as is the voltages your vehicle allows, and when, and for how long, and what may or may not affect its decision making as to what voltage it will decide to allow/Aim for.

My 89 dodge's voltage regulator is inside my engine computer, and appears to be completely devoid of logic or reason in the voltages it decides to allow. I have a plan on external regulation with an adjustment knob on my Dashboard, but do not have all the parts yet to wire it up.

Alternator recharging can be very effective bringing batteries upto 80% charged, but that last 20% takes about 4 hours, no matter how powerful the charging source might b, and that is if it allows voltages in the mid 14's to be held for those 4 hours.

It is important to get to 100% regularly for good battery longevity. Solar is good for achieving that last 20%, and when plugged into the grid a charging source which can hold absorption voltage of 14.8v, as trojans want, is important too.

Powermax has a line of adjustable voltage MANUAL converters with upto 120 amp ratings, that can hold the battery at 14.8v for as long as it takes to actually max out specific gravity, but it takes a human with a brain and some knowledge and hopefully a hydrometer to determine when to either unplug the charger, or lower voltage to 13.2 to 13.6v.

Next converter I would recommend for minimal recharging times is the progressive dynamics 9200 series with the charge wizard pendant, as one can push a button and the converter will seek and hold 14.4v for 4 hours.

Iota does 14.8v but only holds it for a short time before lowering voltage

I use a Meanwell rsp-500-15 which is capable of 40 amps and any voltage from 13.12 to 19.23v, but it needs some modifications for simple voltage changes and to be able to dissipate the heat it can generate when maxed out for an hour or more when the battery bank is heavily depleted.

Generally, one needs to utilize each and every charging source available, whenever available, to keep the batteries at the highest state of charge as possible, for best battery longevity. Anything less compromises battery longevity to some degree, so one must choose what is acceptable to them, effort and financially wise to achieve acceptable battery life.

anarky321 · Dec 4, 2015

how would this circuit look?

i've been reading the details on the Cole Hersee 200A smart isolator which seems like it would fit perfectly but 2 issues with it - it doesn't isolate the batteries immediately after engine shutoff - so a manual disconnect switch has to be wired in between isolator and battery bank?

another issue - running the inverter/charger for the battery bank while the alternator is charging it....will that be an issue at all? this would be a 2000W inverter/charger

another issue - while the engine is on unless manually isolated the 12v starting battery will in effect be providing part of the charge for the house battery draw since it's seen as part of the circuit by the inverter - but since there is charge moving FROM alternator TO bank then that shouldnt be an issue i guess because it won't be drawing any current out of the starting battery while alternator is running...do i understand this right?

also as far as alternator overheating - assuming an 800AH battery bank and a 300A alternator it should be drawing about 250A during the bulk charge phase is that pretty accurate? how much of a shortened life would i expect from an alternator for using it like this considering that it's rated to 300A?

i was also thinking about putting a manually switched bypass circuit in for the main battery that would disconnect it completely from the charging circuit while the house battery is being charged by the alternator but i think the wiring for that would make things too complicated and its probably unnecessary

SternWake · Dec 4, 2015

Sounds like you want a lot of manual control. perhaps a 1/2/both/off switch rated for 300 amps is what you need. With this you can take the engine battery completely out of the loop when powering the inverter with the engine running, Just Do NOT turn the switch to OFF with the engine running or POOF goes the alternator's diodes. The alternator field disconnect prevents this, if one has the ability to run the field control wires through the switch.

This one is rated for 350 amps continuous when 0000 copper cable is used:
https://www.bluesea.com/products/9002e/e-Series_Selector_Battery_Switch_with_AFD

I assume you are not wanting to try and charge the batteries with both alternator AND inverer/charger at the same time?

I've no idea how much current those insanely huge trojans can actually accept when 50% charged before 14.8v is reached. Instant absorption voltage might be attained at 200 amps, or perhaps 400 would be necessary. to bring them to 14.7.

Or they might take an hour at 300 amps before they climb to 14.8v. I've no idea.

At Idle speed do not expect a 300 amp alternator to be able to produce much more than 100 amps, and the hotter it gets the less it can make.

If Idling and Maxing out the alternator, definitely increase cooling to the alternator.

220F seems to be the tipping point one does not want to exceed if possible.

Such a huge amperage need is really in the realm of two alternators. Or perhaps an external rectifier can be used to keep the heat out of the alternator casing.

http://www.ebay.com/itm/Alternator-...al-Rectifier-Alternator-Upgrade-/161173273360

If the Load of the inverter is bigger than the alternator can provide at that rpm, then the batteries will make up the difference, and yes if the engine starting battery is in parallel with the house batteries, it too will be discharged.

There are a lot of variables in how much any given alternator can make at a given temperature and certain rpm. I can't give definitive answers, and am not willing to speculate since I have no experience with such giant batteries or with alternators rated at 300 amps.

The marine guys take their alternator charging more seriously.

http://www.balmar.net/aa-at-layout.html

speedhighway46 · Dec 4, 2015

The regular diode battery isolators are a problem because of the voltage drop. Several years ago a European company came out with a series of battery isolators based upon field effect transistors instead of diodes; there is no voltage drop.

I have a three port FET battery isolator in my motorhome. It's has worked flawlessly. It is fed from a direct line from the alternator. One port goes to the starting battery bank; one port goes to my deep cycle house battery band; and the third is not used but is reserved for another deep cycle battery bank when I install my solar system.

Look under the thread "two questions" in the electrical section for a diagram of the electrical system. This FET BI is sold by Jamestown Distributors and is shown on their web site.

Another option for you . . .

anarky321 · Dec 5, 2015

the alternator would be more of a "backup" option when AC recharging was not available

the 350A switch looks like a great solution

the particular 300A alternator is rated at 225A idle

alternator and AC charging will never be at the same time of course

can you recommend a good ~3000w inverter/charger that can accept both 120v and 240v input? ie being able to charge from the standard 50A 14-50R RV outlet, 30A TT-30, 5-15R 15A house outlet (switch between the 3 with adapters) AND be able to plug into 240v stove/dryer plug with a separately wired cord ie dual-input inverter...is this possible?

^ the main need for this is flexibility in finding plug-in power sources

anarky321 · Dec 5, 2015

for some reason im missing the edit putton on my post all of a sudden

im sitting here thinking about this - how am i supposed to charge a 1000AH battery bank with a 3000w inverter/charger from a household outlet which is typically 15A without blowing the breaker? is the inverter able to be programmed to only draw a certain amperage on the 120v line while charging?

SternWake · Dec 5, 2015

I've not investigated inverter/chargers offerings, having myself never needed more than 800 watts of inverter, and my preference to keep the inverter a separate device than the charger in my smaller system, and cannot make recommendations.

I am not sure if the adjustable voltage 120 amp Powermax converters can be run in parallel for 240 amps, I strongly suspect so, at least until absorption voltage is reached, but these are power factor corrected and a single 120 amp charger can be run off of a standard 15 amp receptacle. Email Errin at powermax and see what he says about paralleling them.

The PD series and Iota chargers, their 80 amp + offerings requires a 20 amp circuit.

I'm also not familiar with the standard plugs at RV parks and can offer no assistance there other than to expect low input AC voltage and an underperforming charger because of it

anarky321 · Dec 5, 2015

RV PARKS - 50A@120v x2 = 12kw , 30A@120v = 3.6kw , and 15A@120v=1.8kw utility outlets

the 50A is a 14-50R outlet 4-wire 4-prong (electric stove outlet but wired differently), the 30A is a TT-30R 3-prong

blars · Dec 5, 2015

If you really want that, I'd look at marine chargers. But a practical sized Lead-Acid bank won't be able to handle enough current to make a 240v charger needed, and setting the input current limit is something only on some high-end chargers. LiFePO4 batteries can handle the current, but are you going to be able to quick-charge them often enough to make the extra expence worthwhile?

anarky321 · Dec 6, 2015

its more about flexibility than pure current, for a 12v 800AH bank you'd want a 160A 2500W charger but the typical household outlet trips at 1800w so therein lies the need for 240v compatibility so you can plug into an empty dryer outlet if needed

after thinking about this i too agree that the charger and the inverter can and probably should be separate units, either that or id only use the larger inverter for charging and have a smaller wired in for everyday use

LoupGarou · Dec 7, 2015

If your starter battery and the battery bank are different battery types, you might consider a Battery-To-Battery charger made by Sterling Power.

http://www.sterling-power-usa.com/ProCharge-B-waterproof-dcinput-battery-charger-12volt-12volt.aspx

Cousin_Eddie · Nov 5, 2020

Hi everyone,
Hope your day is going well.

So… I removed my generator and went from a single 12v house battery to a four 6v battery bank with solar panels and an inverter. I installed a new 32A converter replacement unit and fuse panel. I also have Shure Power. Everything is installed correctly and the system has preform flawlessly for over three years.

However after the conversion the DC to/on my RM2310 Frig stopped working. It works fine on propane and AC. Also I notice when the engine is running my DC control panel doesn’t show that anything is charging like it did before. The alternator may not be able to charge the larger battery bank but the DC should still work on the Frig.

I did wire the inverter into the automatic transfer switch left over from the old generator which gives me use of all the wiring so I can use outlets and such. Meaning I can run the Frig on AC from my battery bank just like a generator but that would drain the batteries in a few hours.

I like trouble shooting over all, but this one I can’t seem to get it resolved.

bullfrog · Nov 5, 2020

I believe that since you have AC available the refrigerator control board is programmed to use AC. The only time it will switch to DC is when it senses AC is not present. I would try turning off the inverter and seeing if the refrigerator can be set to use DC.

Cousin_Eddie · Nov 6, 2020

Thanks for the Reply bullfrog.

The Frig is older and set manually. I keep the Frig AC circuit off unless I plug-in. I also tried disconnecting the circuit breakers from the solar charge controller and the inverter.. Still no DC charge or DC Frig.

One odd thing,

If shut-off the batteries, lights, fans and everything is of course not working but the DC charge panel shows the batteries are charging... I’ve never tried running the Frig with the shut-off in the off position lol. Frig was fine with the single house battery it was grounded to the body and I went back the same way with the battery bank.

barleyguy · Nov 6, 2020

RV fridge problems like that are somewhat likely to be something on the circuit board. It's generally all one board that controls all of the switching logic.

You can buy a new board for most old fridges from here:

https://www.dinosaurelectronics.com/

They are in the $100-150 range and pretty easy to install, probably just a few screws and some ribbon cables.

bullfrog · Nov 6, 2020

What is the state of charge of your battery bank? Are all the batteries close to being equal (balanced)? Could you have disconnected the batteries while the solar panels were connected to the controller and caused damage to it? How much solar do you have in panels and how much is getting to the controller? I would start verifying power at the source (panels) with just the battery bank connected and all loads disconnected. Once the battery bank is determined to be good and getting properly charged I would then add loads one at a time while watching the battery state of charge. You may find some hidden 120 volt loads the generator or shore power handled just find that your battery/inverter system with solar can’t, but I’m just guessing. Start at the source and make the checks and check the loads. If you could draw a diagram of how you installed the inverter and converter as will as what was done with the isolating switch for shore power. Where in the system did you add the inverter and converter? Is the converter running off the inverter now?

bullfrog · Nov 6, 2020

Sorry for all the incorrect spell check, find=fine and will=well. Using existing wiring could possibly cause the converter to run off the inverter as 120 volt shore power is generally wired directly to the shore power once the power selector switch is turned on I believe. This would create a large wasteful load on the batteries.

Cousin_Eddie · Nov 7, 2020

Thanks for the imput.
I'll do some more trouble shooting.

Drmiller100 · Nov 9, 2020

So you have a 12 volt dc to 120 inverter which plugs into a 120 to 12 volt converter.
Is the converter outputting 12 volts dc or 12 volts ac?

Why not skip skip the inverter/converter and use a piece of wire and a fuse?

battery bank charging from alternator

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