running two chargers

BFL13 wrote:

No idea where you are getting that idea from.

A bit off on a tangent......
A friend of mine has a charger similar to those pictured.
We checked the charging voltage and saw it go up as high as 17.5 volts. That seems a bit high to me.

On topic: My guess is that having identical chargers might increase your chances of success......might.

The idea comes from the fact that "smart" chargers adjust their output based on the "back voltage" or internal resistance it sees from the battery. If part of what it sees is NOT the battery but another device, the odds of things not working right are high.

I feel like it would be much less of a hassle to just upgrade your converter/charger to a 75amp/100amp model. No Mickey mousing clamping or disconnecting batts. Just my 2c.

Dirtpig wrote:
I feel like it would be much less of a hassle to just upgrade your converter/charger to a 75amp/100amp model. No Mickey mousing clamping or disconnecting batts. Just my 2c.

well, since I have a 2000VA generator, it will NOT run a 75 or 100A charger. so, I have a 55A charger in place of the WFCO and a 65A in the pass through. when only on one generator, on goes the pass through 65A. when I have shore power or two generators then I crank them both on and get 110A or so for quite a while.

So, there are reasons to have two chargers rather than one.

and there is no mickey mouse stuff, I just turn one or the other on or both on. both are connected to the same battery bank in parallel.

ktmrfs wrote:

and there is no mickey mouse stuff, I just turn one or the other on or both on. both are connected to the same battery bank in parallel.

In this WHOLE discussion, did you miss the main point......which IS that connecting two chargers at once might not give you significantly more total charging current than just ONE.....because both may "adjust" for the presence of the other.

What actually happens depends on which two chargers you have.

3 answers. one is a caution.

In the manual for my Prosine 2.0 Xantrex suggests a maximum charge rate of 30% the C/20 amp hour rate. so if you have say one pair of 110 amp hour GC-2 batteries in series (still 110 amp hours since in series you add voltage) that would be 33 amps max charge. Or less for most battery types. Or more for LIFELINE AGM only.

Second answer: If you have enough battery it will not HURT and no damage will happen but I stress for 50 amps you need around 175 Amp Hours of battery capacity at the c/20 rate. or a whole bunch more at the Wal*mart rate (long story told elsewhere about how wal*mart cheats on their capacity ratings)

Third answer.. MOST LIKELY OUTCOME. is only one device will charge the other will go into standby so you won't double charge rate.. That applies to "Smart chargers"

How parallel power sources work.

I see folks arguing that even in a parallel setup. such as I run, all batteries must be "identi9cal" which mine are NOT..

They give all sorts of myths as to why this is.
"The smaller battery will reach full charge and signal the converter to stop charging": True for batteries in SERIES, not in parallel.
"the smaller battery wi9ll "Draw down" the larger one.. No, not unless it shorts out.

NOTE even if they are all identical. Short out will draw down non shorted batteries.

Now with batteries in SERIES each battery in a single chain (usually 2 GC-2's) must be identical to its partner.. But adjecent pairs need not be.

Why is this that you7 can parallel different size batteries.
When discharging the battery with the higher voltage will provide all or nearly all, the power till the voltages match then each battery will prov9ide a share equal to the size rati9os. so if you had two batteries one 100 amp and one 50 one would provide 2/4 (the 100 amp) and the other 1/3 (the 50)

And charging. the battery with teh LOWER voltage will suck nearly all the power till it reaches the same voltage as the other then. See above.

Once equality (State of charge) is reached, they will remain in lock step. and when one readches full (or empty) the other is there as well.

Now with multiple CHARGERS. the onhe with the higher voltage (they are almost never exactly the same) will provide the lion's share of the charge, up to all of it, while the other one goofs off and does nothign.

wa8yxm wrote:
3 answers. one is a caution.

In the manual for my Prosine 2.0 Xantrex suggests a maximum charge rate of 30% the C/20 amp hour rate. so if you have say one pair of 110 amp hour GC-2 batteries in series (still 110 amp hours since in series you add voltage) that would be 33 amps max charge. Or less for most battery types. Or more for LIFELINE AGM only.

Second answer: If you have enough battery it will not HURT and no damage will happen but I stress for 50 amps you need around 175 Amp Hours of battery capacity at the c/20 rate. or a whole bunch more at the Wal*mart rate (long story told elsewhere about how wal*mart cheats on their capacity ratings)

It's true that lower charge rates help in battery cycle life. Ideally many batteries want even less than C/3 for optimum charge rate for maximum cycle life, sometimes as low as C/10.

However, most GC-2 have a C/20 rate of 200+AH, not 110. the Trojan T105 is 225AH at C/20. so C/3 would be 75ish A charge rate.

Now a single smaller 12V, 75ish AH rating, yes be careful.

However, within reason charging at higher rates doesn't have a real dramatic effect on cycle life. And in the case of GC batteries, with 500-1000 cycles for cycle life, even charging them at C/2 doesn't seem to affect them much. Now in my case I hit the batteries at times with 120AH, which is C/2 except that I have 4 of them so it's really C/4. But I wouldn't want to try to hit a battery with a charge rate close to C unless they were designed for that high a charge rate. And if you have a single 12V battery and a 55A charger, well, be careful, but it probably wouldn't hold 55A for long.

I could have run 20 Km marathons daily, become Vegan right out of the womb, and purchased a hundred dollars worth of vitamins and supplements monthly, all for the objective of gaining lifespan.

For me. My lifestyle?

Hahahahahahahahahahahahahahahahaha...

Shirley you jest. I would have been a sure target for some malfunctioning transit bus.

A manufacturer CAN NOT RECOMMEND constant voltage saturated charging because CHARGERS CANNOT DO It.

As fuel prices rise, my wallet tightens in response. The best way to preserve a battery is to pour a ton of money into it's maintenance and get tinnitus from hundreds, nay thousands of hours of excessive generator run time.

There is a CURVE exhibiting lifespan versus charge amperage limits. It is most pronounced between 10% of amp hour capacity and saturated charging. Under lab conditions it is something like + - 10%

This is for a ten % min and perhaps 45 ampere max charge span.

Factor in generator annoyance -- generator wearout, fuel, and logistics costs then try and defend so-called "ideal max charge rates"

"Uh raised muh oan tomatoes. Can you taste the difrunace? Doan wanna talk about the cost -- pretty touchy abut that"

I tend to think more about amp hour consumption versus recharging costs to replenish. You know -- a hundred dollar battery versus five hundred dollars to recharge. In deep double-canopy shade.

My car engine would last longest if driven at exactly that speed where the transmission switched to overdrive -- 42 mph. But then if I can listen to a generator hammer 3 extra hours every recharge -- I can leave the car parked and use a unicycle (less footprint).

ktmrfs wrote:

Dirtpig wrote:
I feel like it would be much less of a hassle to just upgrade your converter/charger to a 75amp/100amp model. No Mickey mousing clamping or disconnecting batts. Just my 2c.

well, since I have a 2000VA generator, it will NOT run a 75 or 100A charger. so, I have a 55A charger in place of the WFCO and a 65A in the pass through. when only on one generator, on goes the pass through 65A. when I have shore power or two generators then I crank them both on and get 110A or so for quite a while.

So, there are reasons to have two chargers rather than one.

and there is no mickey mouse stuff, I just turn one or the other on or both on. both are connected to the same battery bank in parallel.

75A on 15A line, 1260W.

Any good?

HTH;
John

ScottG wrote:

2oldman wrote:
OK, yes, parallel batteries might do better separated. Series, no.

Remember, the discussion is about using two chargers. Trying to use two smart chargers for either parallel or series batteries never works well if the two chargers are in parallel.

That's just not true. We use parallel Boondockers all the time. Also PD and others. It does work and many OEM send out units like that as well as fleet vehicles.

Like others, we routinely parallel two chargers (solar or shorepower). They are set to the same absorb set point.

During bulk phase their amps add together and get the batteries up to about 80-90% SOC quickly.

But during the absorb Constant Voltage phase one eventually cuts out, perhaps because of a slight difference in temperature adjusted V? And/or as long as just one can provide all the amps the batteries will accept at that point?