Battery Charging with Ham Radio Power Supply

[Jmel]

> menu setting for end voltage. It lowers amps once it get to this total voltage (2.4v default for 6 cell 12v) until battery full.

With lead, there is no "end voltage", that's for other chemistries.

Absorb should be held until 100% Full, usually defined as endAmps, usually .005C.

Only then dropping to float.

And chargers don't lower the amps, just hold volts.

It's the resistance of the batt, depending on the chemistry that determines CAR at a given SoC.

I probably didn't describe it accurately, but yes it holds the voltage until the battery eats less amps. On the rc charger there is no float though. 

We'll see how well the 20a one does once it arrives.

 

[highdesertranger]

on most newer vehicles the voltage regulator is in the main on board computer. you would need to reprogram the computer to change the settings on the alternator. highdesertranger

 

[Spaceman Spiff]

> This is to be a backup plan to keep from damaging the house batteries or keep food, medications from spoiling.
There is no such danger.
???  Running FLA batteries below 50% will not damage said batteries?  Or to save batteries by turning off refrigerator won't compromise food or medications that need refrigeration?

As such I would drive as much as needed to charge batteries
> If you mean to 100% Full, then that means 5-7 hours. Assuming the Alt even puts out that power without overheating, without a shunt on the House batt you could be wasting very expensive wear and tear.
This is a backup system that I have needed about once a year.  If I have to run my truck to get my batteries back to ~80% or from ruining meds by turning off refrigerator to save the batteries I will.  I understand the last 15-20% charge requires ~3 hours.  My plan is to keep my batteries above 60% and equalize on shore power as soon a I can, and hope this minimizes damage to batteries.

You bring up a good point:  How many amps will two golf cart batteries (208 AH) accept at 50% capacity?

> or to find shore power.
That's better, only time to use the PS.
That assumes one can move to find shore power.  Two years ago I was stuck in the Utah back country for four days due to impassible roads.  Batteries were down to 65% before the sun came out and I was able hold around 75% until I could drive out and find shore power.

Forget the EEs, IMO more likely to just get you confused, unless they specialize in low voltage systems or battery design.
These are EEs I worked with for 30+ years.  Yes they confuse me but they keep asking questions until they understand what I need.  Unfortunately, unless by accident, I only see them once a year.

> I have a Trimetric 2030RV that I am in the habit of looking at every time I stop.
Excellent unit. Shunt is on the House terminal?
Trimetric is wired so all current to the house batteries negative terminal go through a 500Ω shunt.

Watch it while you're actually charging off the Alt, look at Amps live, can't trust SoC unless it's well calibrated to declining actual bank AH, and recently manually reset to 100% or based on endAmps.
Trimetric is reset twice a year after equilization and bench charging to ~1.5A @ 14.3V.  Batteries have been reading a consistent 1.27+ specific gravity for four years.

To summarize:

• I have a need for a method of charging my house batteries when sunlight is not adequate to keep my batteries charged and shore power is not available.
• I camp in places where I could be stuck for a while.  Or take 3+ hours to get to shore power.
• I have a Jetstream JTPS31MB power supply that I can use as a dumb charger.
• I do not have a small generator nor the funds to buy one, do not have a place to carry one, do not want to carry gasoline inside the camper.
• My truck alternator produces 14.6V when charging; my house batteries lose water above 14.3V when charging and are in a difficult place to access.
• As I carry the power supply to equalize and to charge when shore power is available, I am looking at the advisability of using it and an inverter as my backup.
• My other alternative is using the truck alternator as the charging source directly.  I will have to find a way to reduce the voltage at the house batteries to 14.3V, add an automatic watering system, or add water to the batteries when used.
• Either of these solutions may require the alternator to supply power without the truck moving so I will need a way to keep the alternator cool.

Thank you all for your input.  I have a number of questions I will have to research.

 

[highdesertranger]

Spiff doesn't the alternator back off the 14.6v after a short while? most do and settle around 13.8v. 14.6 is real high for alternator output voltage, have you checked the specs is it supposed to be that high? is the main engine computer the voltage regulator? highdesertranger

 

[John61CT]

The only thing regulated by an alt VR is voltage.

As long as it is connected to a bank it thinks is not full, it (strives to) put out Absorb V, whether it can or not depends on the batt SoC.

Once it thinks the batt is full, it drops to Float V.

The only time it can be in between is Bulk, striving to get to Absorb.

 

[John61CT]

I meant no danger of damaging the batts charging by Alt directly:

> My other alternative is using the truck alternator as the charging source directly.  I will have to find a way to reduce the voltage at the house batteries to 14.3V, add an automatic watering system, or add water to the batteries when used.

This is what you should do.

If you can't, save up for

a mod job to the Alt/VR if your vehicle allows that, or

a Sterling DC-DC B2B

But IMO only when driving for other reasons. Running the propulsion engine for extended periods of time is very wasteful and expensive. I would recommend a little genny and/or more (portable) solar.

 

[Spaceman Spiff]

Spiff doesn't the alternator back off the 14.6v after a short while?  most do and settle around 13.8v.  14.6 is real high for alternator output voltage, have you checked the specs is it supposed to be that high?  is the main engine computer the voltage regulator?  highdesertranger

The alternator was generating 14.6V when starting battery was at 12.3V (voltage measurements at battery), started tapering to 13.6V when battery was ~12.5V.  Air temperature was ~75ºF, hood open, ~2000 RPM during test.
Alternator spec's call for 14.8V when charging, 13.8V when maintaining, and is internally regulated.  My free HF voltmeter could be off, my good VOM was measuring amps.

 

[tx2sturgis]

Like everyone else, I'm following and contributing to several threads, so if this was addressed, I might have missed it.

Lets drill a bit deeper into the original question:

Reason I am asking is ...... I am confused about how the my truck alternator (2012 Ram PU) will respond to a full starter battery and a depleted house bank.

Going back to this original post, you mention that your GC batteries will be depleted...why would that happen?

Do you expect to deplete them daily or weekly and possibly have no solar input at all? 

Or are you asking just in case this might happen, at some time, with several days of overcast skies or parked under trees for a week or three?

In other words, are we addressing an expected regular occurrence or a backup strategy?

Because if you plan (or expect) to 'deplete' those batteries regularly, your out-of-pocket expenses could go up a LOT more compared to having a properly-sized solar array to keep them from getting 'depleted'.

If you are operating a 12v fridge, the LV cut-out circuit in that unit SHOULD shut it down before the GC batteries are 'depleted'. If you kept operating other items, then you COULD deplete the batteries...but why would you do that? Most of us would begin conserving power use until the solar input can 'top-up' the batteries.

If you only expect normal, light use, and regular topping-up with solar, then the very robust and forgiving GC batteries will easily tolerate normal vehicle alternator voltages for the short periods of time during your stated drive times of 25-150 miles.

If the GC batteries DO get deeply depleted, then when they are paralleled with the starter battery, they will see a HUGE influx of current from your healthy starter battery, more or less rapidly equalizing the level of both sets of batteries, and the alternator output will be divided between 3 partially depleted batteries.

So my question is:

What will you be doing, or not doing, to keep those GC batteries in good health when you are off grid, off shore power, and using them during your boondocking expeditions?

 

[Spaceman Spiff]

 . . .Going back to this original post, you mention that your GC batteries will be depleted...why would that happen?
Do you expect to deplete them daily or weekly and possibly have no solar input at all? 
Or are you asking just in case this might happen, at some time, with several days of overcast skies or parked under trees for a week or three?
In other words, are we addressing an expected regular occurrence or a backup strategy?
From post #23:  [font=Verdana, Arial, sans-serif]This is a backup system that I have needed about once a year . . . [font=Verdana, Arial, sans-serif]Two years ago I was stuck in the Utah back country for four days due to impassible roads . . .
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I have 200W & 208 AH of supply, I use ~ 30AH/day which should give me 3 days margin with no solar input.

 . . . So my question is:
What will you be doing, or not doing, to keep those GC batteries in good health when you are off grid, off shore power, and using them during your boondocking expeditions?
My solar charging system works well.  My big draw is the refrigerator at < 35 AH/day; I am usually at 100% before 1 PM.  This is for those few times when I am stranded in the back country with no sun or a long ways from shore power.  Batteries are 4 years old and still have a 1.27+ specific gravity.

 

[John61CT]

if you plan (or expect) to 'deplete' those batteries regularly, your out-of-pocket expenses could go up a LOT more compared to having a properly-sized solar array to keep them from getting 'depleted'.

Down to 50% is depleted enough to cause possible overheating / low production issues with a stock alt setup.

It is exactly what deep cycle batteries are designed to do in daily usage, does not imply any abuse.

Depleted as opposed to say 10-20% DoD, which would present little challenge, even to modern "green" vehicles' alts controlled by the ECU / ECM / PCM

For more traditional alt setups, the internal VR can be replaced with a much more effective external unit, but even that minimal mod is pretty expensive, IMO only worthwhile if the alt is an important charging source.

I think a little gennie is more flexible and cost-effective.

But in this case, nothing at all is required other than a good ACR and maybe a watering system.

 

[John61CT]

> Trimetric is reset twice a year after equilization and bench charging to ~1.5A @ 14.3V.

For better accuracy, the "reset to Full" should be done manually every few cycles.

Unless you a really very confident Bogart's auto-reset's "Full judgement" is based on the same 1.5A endAmps reading, and your solar is actually going over that SoC point very regularly.

 

[John61CT]

> How many amps will two golf cart batteries (208 AH) accept at 50% capacity?

With the Trimetric, how are you not observing this yourself?

I would think at first in the .15-.25C range, then quickly dropping after passing 85% SoC toward the beginning of a 3-5 hour Absorb stage.

 

[John61CT]

Your House bank will charge just fine at 14.3V, just a little slower.

 

[tx2sturgis]

Down to 50% is depleted enough to cause possible overheating / low production issues with a stock alt setup.

It is exactly what deep cycle batteries are designed to do in daily usage,  does not imply any abuse.

50% depletion EVERY day?

Really? For how MANY days? This is where the trade-off is...how long would it operate this way?

Quite often I pull mine down to about 80%, and they always recover nicely. But even then I don't do this every day.

My point is that the starter battery COULD share some of the load of recharging the GC batteries, for a brief period of time anyway, and as the alternator pumps out the amps, the batteries will recover, at least partially. This is exactly how many factory fresh RV's are wired (thru a solenoid) and have been for decades.

And I was not implying 'abuse'...but over-use of the existing bank sounds possible.

 

[tx2sturgis]

My solar charging system works well.  My big draw is the refrigerator at < 35 AH/day; I am usually at 100% before 1 PM.  This is for those few times when I am stranded in the back country with no sun or a long ways from shore power.  Batteries are 4 years old and still have a 1.27+ specific gravity.

Ok.... 35 ah from this bank is not 50%, and not every day, but only occasionally when solar conditions make it happen.

Yes for occasional recharge back to full capacity, I still think, without you using a generator, and in your case, a manual battery switch to parallel the GC batteries with your main battery when driving is the answer.

Simple, effective, and reliable.

 

[Spaceman Spiff]

For better accuracy, the "reset to Full" should be done manually every few cycles.
Unless you a really very confident Bogart's auto-reset's "Full judgement" is based on the same 1.5A endAmps reading, and your solar is actually going over that SoC point very regularly.

Before I equalize I check specific gravity; all cells have always been 1.27+, with the Trimetric reporting 100%.  I am using S.G. as my figure of merit for 'full'.

With the Trimetric, how are you not observing this yourself?

I have never had my house batteries below 65% and that only once.  Unfortunately, I only had a 6 amp charger available at the time.

 

[John61CT]

> 50% depletion EVERY day?
That is exactly what proper deep cycling batteries are designed for, and why it's worth spending a bit more on quality.

It does no harm at all, even if every single cycle (some scenarios, not solar, a cycle may be 2-3 days)

Yes, if you cycle more shallow most cycles, only go down to 50% sometimes when conditions aren't great, the bank will last longer, maybe over a decade.

But if you're **never** getting down to 50%, you may be carrying too much expensively heavy lead around, 800AH weighs a lot more than 500.

> My point is that the starter battery COULD share some of the load of recharging the GC batteries, for a brief period of time anyway, and as the alternator pumps out the amps, the batteries will recover, at least partially. This is exactly how many factory fresh RV's are wired (thru a solenoid) and have been for decades.

The US RV industry is generally a very poor role model for good low-voltage electrics design. Marine electrics much more so.

The Starter **battery** has no role, should have no role, as a charge source. It's job is to crank the engine, full stop.

It is easy to design a system without any dedicated Starter batt, but that's another thread.

> And I was not implying 'abuse'...but over-use of the existing bank sounds possible.

90% of people away from shore power for long periods do truly abuse their banks, murder them in fact, never getting even half the lifespan they're designed for.

True on boats, but even more so on land, a long list of DO NOTs are in fact done every day, and many SHOULD DOs neglected. Most people are not even aware of the factors involved, but regular members here are learning them every day.

Going down to 50% every cycle is not such an issue.

 

[Spaceman Spiff]

Yes for occasional recharge back to full capacity, I still think, without you using a generator, and in your case, a manual battery switch to parallel the GC batteries with your main battery when driving is the answer . . .

I think I am coming to the same conclusion.  Dump the 25A charger and use the Morningstar CC for equalizing.

 

[John61CT]

> for occasional recharge back to full capacity, I still think, without you using a generator, and in your case, a manual battery switch to parallel the GC batteries with your main battery when driving is the answer.

I agree in general, but two nits to pick.

The dino juice needs to be applied in the morning before solar kicks in, otherwise never get to Full.

And an ACR is required rather than a mnual switch for those of us with less than perfect checklist memories.

Too easy to forget, leave it in the combined position when engine's off and loads deplete Starter, if you're out in the boonies no fun.

Yes, a backup powerpak can jump, but that's another piece you have to buy, maintain, replace.

An ignition-switched solenoid is good, but then Starter doesn't get topped up by solar or mains when stationary for long periods.

An ACR is best, and as long as you don't need it for cranking currents, not even expensive.

 

[John61CT]

> Morningstar CC for equalizing

Shore is best, no real harm going to six weeks instead of monthly.

But yes, as long as you can follow the protocol to completion, reliable insolation, batt doesn't care where the juice comes from.

Just don't allow automatic, always equalize manually.