Battery Charging with Ham Radio Power Supply

[Spaceman Spiff]

I have two questions:

1. Is it advisable and what are the risks of using a variable voltage power supply set at absorption voltage to charge my house batteries, checking once an hour or so?
        
2. The good and the bad of placing an inverter close to the battery/alternator under the hood and running a 110V line back to the battery compartment to run the power supply  vs.  running big cables from starting battery to house batteries?

Reason I am asking is that I have the power supply and I am confused about how the my truck alternator (2012 Ram PU) will respond to a full starter battery and a depleted house bank.  The power supply is a 25 amp, 4 - 16 volt adjustable ham radio switching power supply.

 

[tx2sturgis]

I have done some similar things...more than once.

So...I have a couple of thoughts.

Power supplies work great as a 24/7 float supply, but don't have the 'smarts' to limit current by reducing voltage when you aren't there watching everything. If the batteries get depleted, the power supply will be overworked and might even overheat or shutdown, since the battery may try to draw more than the supply can put out, depending on the size and the charge level of the battery. You are probably referring to a 30A supply, most of those are rated at 25 amp continuous, 30 amp surge.

The way I get around this on mine is to insert a self-resetting 10A circuit breaker inline, this will slowly 'pulse' the incoming current to the battery when it goes above 10 amps.....it works, but is an off-label, non-standard use.

As far as the inverter under the hood:

Most inverters have LOTS of vent openings and if it rains hard, and you splash thru some ponding water on the road, you can bet that not only water, but road grit will end up in the inverter, and probably ruin it, or worse, start a fire.

Years ago I installed a remote mount ham transceiver chassis under the hood and after a hard rain, the radio display freaked out and the radio became a paper weight.

Live and learn.

 

[John61CT]

> Is it advisable and what are the risks of using a variable voltage power supply set at absorption voltage to charge my house batteries, checking once an hour or so?

Yes, no problem at all, as long as

you set volts to what the target batt mfg specs are, and don't forget to check, end up boiling all the water away.

And, the power supply is self-limiting wrt current protection. Good ones are, cheap ones aren't. You are just risking the PS though, not your batts. See below

As the bank SoC is rising, current is reduced. When amps drops to around .005C (.5A per 100AH) the bank is 100% Full, all charge sources should hold Absorb until that point.

Then just shut it off, no need to float unless in storage, say once a week top up.


> Power supplies work great as a 24/7 float supply, but don't have the 'smarts' to limit current by reducing voltage when you aren't there watching everything.

Yes, but OP is talking about monitoring manually, just as Sternwake does with his House bank.


> The way I get around this on mine is to insert a self-resetting 10A circuit breaker inline, this will slowly 'pulse' the incoming current to the battery when it goes above 10 amps.....it works, but is an off-label, non-standard use.

Excellent idea, but only needed if the PS doesn't have good built-in circuit protection.

The CB should not be instant type, have a bit of delay, and can be sized within 10% of the PS continuous rating.

 

[John61CT]

> The good and the bad of placing an inverter close to the battery/alternator under the hood and running a 110V line back to the battery compartment to run the power supply  vs.  running big cables from starting battery to house batteries?

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

I am so confused by this idea.

There is no reason to run a PS (AC to DC) off an inverter (DC to AC). The PS should only be run from shore power, mains or genny.

Just parallel the House bank with the Starter once the alternator is charging.

If it gets too hot because your House is well depleted, its thermal protection will cut output until it cools down. House being lead, as SoC rises, it won't demand a lot of amps anyway after a while.

How many hours a day do you drive?

How many days are you away from shore power?

 

[tx2sturgis]

Most normal power supplies, once tripped, do not automatically reset. Either a fuse or breaker blows, and/or the crowbar protection shuts it down. This is why I use the self-resetting breakers at about half the power supply rating.

Purpose built smart chargers will not stop working, they just limit current until the battery state of charge is high enough that incoming current is reduced.

 

[Spaceman Spiff]

I am so confused by this idea.
I am looking at options.  Deadwood's post Electrical thoughts after a 12 day road trip prompted my thinking that I need to improve my plan B, which is currently a single stage 6 amp charger run off the trucks small inverter.  I have only had a few times when my batteries were not at 100% at the end of day because of the lack of sun, so it is not a pressing need (yet).  I have only once run my batteries down to 60%

There is no reason to run a PS (AC to DC) off an inverter (DC to AC). The PS should only be run from shore power, mains or genny.
I have the power supply.  I do not have a generator, do not have the funds to purchase one, do not want to carry extra gasoline nor a gas appliance in the camper.

Just parallel the House bank with the Starter once the alternator is charging.
Why the starter and not the starter battery? Or the alternator directly?

My batteries (2 X GC2) lose water fast if the absorption voltage > 14.3.  The voltage set point for the alternator in my truck is ~14.6V (drops to 13.6 when starter battery is full), hence my concern over using the alternator for charging. I can set the power supply to give me a stable current source at 14.3V and remove it when the battery get to ~90% and let the solar finish (or not).
 . . .
How many hours a day do you drive?
I might sit for a week, move every couple of days; depends on when I want a change of scenery or need groceries.  When I drive it is 25 - 150 miles.

How many days are you away from shore power?
I have (pay for camping or visit friends) shore power about once every 30 - 50 days when out to do equalization with the power supply.

Thanks for your critique.

 

[Spaceman Spiff]

I have done some similar things...more than once.
So...I have a couple of thoughts.

Power supplies work great as a 24/7 float supply, but don't have the 'smarts' to limit current by reducing voltage when you aren't there watching everything. If the batteries get depleted, the power supply will be overworked and might even overheat or shutdown, since the battery may try to draw more than the supply can put out, depending on the size and the charge level of the battery. You are probably referring to a 30A supply, most of those are rated at 25 amp continuous, 30 amp surge.
I do watch my batteries (probably more than I need to) and get nervous when they approach 70%, so if I go this way I will be stoping every hour or so to check the batteries/power supply.  When batteries get to ~ 80-90% I would shut the power supply down and let solar finish.

Yes the supply is advertised as a 30 amp (rated at 30 amp surge, 25 amp continuous in the small print).

The way I get around this on mine is to insert a self-resetting 10A circuit breaker inline, this will slowly 'pulse' the incoming current to the battery when it goes above 10 amps.....it works, but is an off-label, non-standard use.
Should not the power supply self limit to its rated current, in this case 25A (or 30A)?  And it should be able to deliver that current continuously and safely.  The designed in heat dissipation should take care of the heat generated if there is adequate airflow around the supply.  I don't know how this power supply handles 'surge'.  More questions!

As far as the inverter under the hood:
Most inverters have LOTS of vent openings and if it rains hard, and you splash thru some ponding water on the road, you can bet that not only water, but road grit will end up in the inverter, and probably ruin it, or worse, start a fire.
Good point.  I would have to find a place under the hood that is protected or build protection for an inverter.  I'm getting too old to drive with a snorkel.  Are marine inverters more water resistant/proof?
Dirt is an issue as I drive dusty roads a lot.

Thank you also for taking the time to think this through with me.  Even if I go with alternator or some other backup charging method I will need to figure out the best way to run the power supply every 6 weeks or so to equalize.  I have plenty of time as I will be making modifications to the truck and camper in March/April.

 

[John61CT]

> I have the power supply.  I do not have a generator

My point is that the PS is only useful plugged into mains power.

Just like an inverter does not create any power. Think about it, where is the inverter getting its input?

And note the specsheet for the power supply should tell you if it has overcurrent protection, and if so, what type.

Most don't, cheap ones just release the magic smoke when a load demands too much.

> Why the starter and not the starter battery? Or the alternator directly?

Starter battery, as opposed to House. The circuit between the Alt and Starter (batt) is joined from any point to House for charging purposes. An ACR/VSR is often used to ensure the Starter is not depleted by House loads.

Assuming the House bank is a chemistry type that is happy with the Alt output voltage.

> My batteries (2 X GC2) lose water fast if the absorption voltage > 14.3.  The voltage set point for the alternator in my truck is ~14.6V (drops to 13.6 when starter battery is full), hence my concern over using the alternator for charging.

Lower the alt setpoint if you can. Or top up water more frequently, bubbling does the bank no harm, just don't let the plates get exposed.


>  When I drive it is 25 - 150 miles.

Then alt is unlikely to be a significant charge source, at least not worth investing big money modifying to be able to do so.

But a cheap voltmeter and shunt showing amps going into your House bank would be a very worthwhile investment, maybe rig to display at your dash.

 

[Jmel]

Sort of related... Ive just purchased a Chinese 20a smart charger for under 20 dollars. I had great success with one I bought that output 6 amps, so I'm hoping this doesn't end my success streak. I will have it in about 2 weeks. My current method was to use a smart lipo/lead/NIMH charger that I use for my RC planes, but due to the 14ga wire, I've limited it to 14a out. Works perfectly, and you can even adjust the peak voltage up or down from 2.4v per cell.

 

[John61CT]

Link please? Very suspiciously cheap!

And why do you quote voltage per cell, do you actually use those big industrial 2V batts in series?

 

[John61CT]

Just as a side note, I'm always on the lookout for Blue Sea's CL-Series BatteryLink ACR (PN 7600), now discontinued.

It actively limits the current to 60A, (actually depends on temp)

Very useful when an LFP bank would otherwise overheat your alt, or overload a PS or charger with poor current limiting.

Also lets you get away with 6-8 AWG wire rather than 4/0 at $8 per foot.

Too big for this case though.

 

[tx2sturgis]

Should not the power supply self limit to its rated current, in this case 25A (or 30A)?  And it should be able to deliver that current continuously and safely.  The designed in heat dissipation should take care of the heat generated if there is adequate airflow around the supply.  I don't know how this power supply handles 'surge'.  More questions!

Power supplies like the one you have dont work like a 'smart' battery charger. As load current approaches maximum, voltage falls off rapidly, VERY rapidly, and the built in-protection (fuse, circuit breaker, or electronic overload protection) will trigger the supply to shut down.

If you have a linear supply with a large transformer, the iron laminations will heat slowly, but the pass transistors will heat rapidly and could end up damaged, either open, or shorted. Neither is a good outcome. Switching supplies tolerate overloads up to a point, then usually just quit working due to circuit traces that burn up. They are often made to a price point and leave something to be desired in overload protection.

If your battery state means the supply is putting out 20 amps, then you're fine. But if the battery is trying to pull 30 amps, the supply will heat up, and either trigger a thermal shutdown or a full power off state, or end up needing repairs.

Power supplies like this are not 'smart'...they are 'dumb'...they just try to power a load, up to the limit, then shut down, blow a fuse, or melt something.

The common exception is a lab power supply with adjustable current limiting,  but that is not what you have.

Power supplies can very easily be used as a float supply, I have done this for years in several installations and here at home. But I install a self-resetting circuit breaker inline, that acts as a simple make-break current limiter.

Actually, I think if you install a simple continuous duty solenoid, or a battery isolator (with adjustments to the alternator if possible) then your system will be much simpler, and more reliable. Or a super simple battery combiner/isolator switch, and manage this task manually.

 

[John61CT]

Note that dropping voltage is just one form of overcurrent protection.

And that won't harm the battery.

I believe some Samlex and Mean-Well PSs have more elegant ways

http://www.meanwellusa.com/qa.aspx see Q13

Note that both ProMariner and Sterling chargers let the user scale doen the de-rating as needed.

 

[Spaceman Spiff]

Just like an inverter does not create any power. Think about it, where is the inverter getting its input?
This is to be a backup plan to keep from damaging the house batteries or keep food, medications from spoiling.  As such I would drive as much as needed to charge batteries or to find shore power.  I have needed to supplement solar charging only twice in four years.  I would still use the power supply to equalize, hence my exploration of using it as a backup charger.

Starter battery, as opposed to House. The circuit between the Alt and Starter (batt) is joined from any point to House for charging purposes. An ACR/VSR is often used to ensure the Starter is not depleted by House loads.
OK, my misunderstanding.  I had understood you to mean connecting to the starter.

Lower the alt setpoint if you can. Or top up water more frequently, bubbling does the bank no harm,  just don't let the plates get exposed.
This is probably beyond my capability; I know enough about electronics to be dangerous.  EE friends will have to advise, whenever I see them again.
At 14.6V I am adding ~ 200ml per cell weekly and the batteries are difficult to access.  At 14.3V I am adding ~75ml per cell every 6 weeks.

Then alt is unlikely to be a significant charge source, at least not worth investing big money modifying to be able to do so.
As mentioned above, this is a rarely needed backup plan so I would drive as needed.

But a cheap voltmeter and shunt showing amps going into your House bank would be a very worthwhile investment,  maybe rig to display at your dash.  I have a Trimetric 2030RV that I am in the habit of looking at every time I stop.

Thanks again 

 

[Jmel]

Link please? Very suspiciously cheap!

And why do you quote voltage per cell,  do you actually use those big industrial 2V batts in series?

I hesitated to post it because, although I don't mind tossing a few bucks on an experiment, I'd feel bad if someone else tried it and had a big problem...

https://m.banggood.com/Intelligent-...tery-Lead-Acid-Battery-Charger-p-1213520.html

As far as the 2v cells... That's how most of these RC chargers reference batteries, so it's not unusual in those applications. It's literally a 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. The RC charger I use is a reaktor 300w.

 

[tx2sturgis]

Note that dropping voltage is just one form of overcurrent protection.

And that won't harm the battery.

I believe some Samlex and Mean-Well PSs have more elegant ways

http://www.meanwellusa.com/qa.aspx see Q13

Note that both ProMariner and Sterling chargers let the user scale doen the de-rating as needed.

Dropping voltage is the normal way of limiting current, and no, it wont hurt the battery, but it wont charge the battery either.

And yes I'm familiar with other supplies and the more advanced way they can work, but Spiff has a common desktop communications power supply, which are, by design, less expensive, lighter duty and less sophisticated. They also usually are RF quiet and RF immune, which the others may or may not be.

It's probably an MFJ, Astron, Jetstream, Tenna, Alinco, or something similar.

 

[John61CT]

> 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.

 

[John61CT]

Fact that they spec 120AH max and lead only says to me not proper current limiting.

If you test it properly please post a review, worth its own thread.

Parallel 5 of these, 100A only $90!

 

[John61CT]

> 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.


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.


> or to find shore power.

That's better, only time to use the PS.


>> Lower the alt setpoint if you can.

> This is probably beyond my capability; I know enough about electronics to be dangerous.  EE friends will have to advise, whenever I see them again.

Go to any decent auto electric / alt shop, ask how much to try the adjustment. If they say more than $50 laugh and try the next.

Converting to a spectacular external VR like Balmar MC-614 is likely not worth it unless driving 20+ hours a week.

Forget the EEs, IMO more likely to just get you confused, unless they specialize in low voltage systems or battery design.


> 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?

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.

 

[frater secessus]

I have two questions:

1. Is it advisable and what are the risks of using a variable voltage power supply set at absorption voltage to charge my house batteries, checking once an hour or so?

That's how sternwake does it, if I remember correctly.  He had an adjustable mean well.