Parallel powermaxes outputs

pnichols wrote:

Mobilesport wrote:
You read it right , when I got my PowerMax it didn't perform like a manual charger even though it had the potentiometer.
After removing resister 1 it now stays at any voltage I set it too like its supposed to.
Really no need for a switch because if you want it at 13.6 volts just dial it to 13.6 volts with the pot.

Way to go ... that appears like you accomplished very quickly and cleanly what many in these forums are trying to arrive at by messing around with adding separate potentiometers onto/into various standalone power supplies. Way to go!

What there trying to do is totally different , there power supplies came with no pot so they added one , mine came with a pot but resister R1
was giving me issues.
What they are doing is buying a power supply and making a adjustable charger by adding the pot , in the end they're getting a nice adjustable power supply for a way cheaper price.
The PowerMax costs twice as much but is already set up.

time2roll wrote:
How long do you want your battery at 14.8 volts?
How long will you be away doing something interesting?

Sure if you plan to be in camp all day or the activities are short it is not a concern. Or you can use the wind up timer like MEX.

Leaving camp with the gen running doing a battery charge on a timer would only work with a motorhome type of installed generator, not with portable gear like I have.

I consider myself stuck there during generator charging so I want to to recharge less frequently, and to get it done as soon as possible when it does need to be done. "It" being a 50-90.

So first, I want that 14.8 to stay at 14.8 for the entire 50-90 and using a timer is not going to tell me when I am at 90. I have to be there to see when I am at 90 so I can shut off the generator, put my charger(s) away and now be free to go somewhere till next time.

Solar is a way to extend the time between required 50-90s, so that is a good thing. When solar is not available, then it is all about the size of the battery bank and how many AH you use each day. To get the shortest run doing the 50-90, you need as many amps as you can put on the bank that it will accept. To run that many amps worth of charger(s) you need a big enough generator.

Your budget, your physical limits on how many batts you can take along, and how big a gen you can take along, are factors. Gas for the gen could be a factor. Another is the allowed generator time in the campground, where you need to get the 50-90 done in that allowed time.

That is why I am forever grateful that a few years back now, you taught me how to use more than one charger at a time to add their amps so it didn't take so long to do my 50-90s. :)

Since generator hours happened to coincide with the best time to go up to the lake for a swim, it meant battery charging was cutting into swimming time. You got me more swimming time! :)

How long do you want your battery at 14.8 volts?
How long will you be away doing something interesting?

Sure if you plan to be in camp all day or the activities are short it is not a concern. Or you can use the wind up timer like MEX. I guess I prefer to have things run automatic because I don't want to be tied down to return at some specific time. Automatic is especially good it you can set it to your needs.

time2roll wrote:
I might also be curious to change the resistor value. Try half or double and see if the time delay is adjusted. If you could get 2 or 3 hours of absorption you could actually go on a hike or go fishing etc without worry.

I don't understand that at all. The voltage drops by one volt after 15 minutes. You could maybe change that time, but what for? With no timer or voltage drop, you just set the voltage and it does Bulk and Absorption at that voltage. How long it keeps the battery in Bulk and how long Absorption takes is just a matter of the max amps (75 amps here) wrt the size of the battery bank in AH. (see ugly graph in the AGM thread)

Of course by the time you got back, somebody might have stolen your generator and maybe your charger if they are portables. :(

Mobilesport wrote:
You read it right , when I got my PowerMax it didn't perform like a manual charger even though it had the potentiometer.
After removing resister 1 it now stays at any voltage I set it too like its supposed to.
Really no need for a switch because if you want it at 13.6 volts just dial it to 13.6 volts with the pot.

Way to go ... that appears like you accomplished very quickly and cleanly what many in these forums are trying to arrive at by messing around with adding separate potentiometers onto/into various standalone power supplies. Way to go!

time2roll wrote:
I might also be curious to change the resistor value. Try half or double and see if the time delay is adjusted. If you could get 2 or 3 hours of absorption you could actually go on a hike or go fishing etc without worry.

47k ohms
Yellow violet orange gold

I tried to get the ohms value of the pot but I have a new Craftsman clamp on meter and it seems to only measure lower resistances , anything higher and it reads OL ------overload
I'll have to read the manual for the multimeter

I might also be curious to change the resistor value. Try half or double and see if the time delay is adjusted. If you could get 2 or 3 hours of absorption you could actually go on a hike or go fishing etc without worry.

Mobilesport wrote:
@ BFL13
What's the deal with having to set the voltage unloaded on these adjustable models?
I mean let's say I set the Powermaxes voltage unloaded to 14.8 volts , I then make a mark on the tape with a sharpee to show were the 14.8 volt mark is , I then plug the pos and neg battery cables to the PowerMax. why do I need that mark ?
Why can't I just read the voltmeter and set the voltage using the voltmeter?
Is the voltmeter reading incorrect so I must go by the mark ?

That voltmeter only shows the correct battery voltage when the battery is full on a Float.

When you are actually charging a low battery, the voltmeter shows a voltage somewhere between what you set it at and what the battery voltage is up to now. If you want to adjust that voltage, you can't go by the voltmeter.

So with no battery connected, turn on the charger, put your voltmeter in the output, twirl the knob and mark some voltages, then install your charger.

Now you can use the marks to set the Vabs you want. You can read the battery voltage on the Trimetric, or voltmeter on the battery, and the voltmeter on the charger will show how close the indicated voltage is getting to what you set it at.

If you don't snip R1, then instead of having two sets of markers, just have a set for after the 1 volt drop. Now at first to get 14.8 you set the knob at the 13.8 mark, and then after 15 minutes and it drops, dial it to the 14.8 mark.

--Valhalla needs to buy one and learn what the 75 amper really pulls from a Honda in VA (see actual numbers posted earlier)

Mobilesport wrote:

valhalla360 wrote:
The Honda 2000 is rated for 1600 continuous watts. 150amps at 12v is 1800watts before considering losses.

At best the little Honda will be running flat out and won't be quiet. Assuming it doesn't cut out from overload, it will put a lot of wear and tear on the generator.

Also, what size is your battery bank? Unless it's pretty big, it won't be able to absorb 150amps.

I have a PowerMax BPCM-75 PF corrected Adjustable model ,,,My Honda 2000i runs the PowerMax pumping 75 amps into two gc2 6 volters (12 volt bank) and the Honda barely comes out of Eco mode and runs pretty quiet and then when the amps start to drop gets really quiet .

I was thinking of adding two more gc2 batteries for a total of four and then run dual Powermaxes

Sure a single 75amp charger should only draw around 1000w (900w + some for losses). That' well within it's capabilities and once the amps drop off, it's even lower. Double that and you will be pushing the little generator hard during the bulk charging. When it drops back to float charging, it should be fine but you also don't really need a 150amps of charging at that point.

Reality is 4 batteries isn't a very large bank...maybe 420amp-hr(?). Assuming bulk charging is from 50-80% then it drops off, it's the difference between 1.7hr and 0.9hr to bulk charge.

@ BFL13
What's the deal with having to set the voltage unloaded on these adjustable models?
I mean let's say I set the Powermaxes voltage unloaded to 14.8 volts , I then make a mark on the tape with a sharpee to show were the 14.8 volt mark is , I then plug the pos and neg battery cables to the PowerMax. why do I need that mark ?
Why can't I just read the voltmeter and set the voltage using the voltmeter?
Is the voltmeter reading incorrect so I must go by the mark ?