Adjustable Voltage Boondocker Converter Question

So I got a hold of Randy today. Randy told me that due to the internal resistance of my 4 GC-2s I would never hit 100amps, and 75 amps would have been fine. He told me just to "roll with it and not worry about it."

I'm pretty sure if I can get 4 12v Walmart specials to take close to 85 amps, I should be able to push down 100amps into 4 Gc2s?

Besides, I'd love to "Roll with it" if I didn't spend extra money for a 100amp charger. I also have a real hard time believing that at 50% depleted GC2s internal resistance lines up exactly to 75amp.

I've tried to get a hold of someone at Powermax, but no luck yet. Admittedly, I've only called twice (no message) and left one email through there support form. I'll try again next week more seriously.

Now that I've spoke with him about this, I can't recommend Randy. I think he's a used car salesmen with some electronics talent. Randy has no intention of helping me get to the bottom of this. So, be warned and stay away.

Joel

I'm gun shy because the pm4b-60 got smoked on its 2nd run, and I have no way of knowing if it was indeed the T, or if it was an over temp issue, or??? It was a very hot day when it happened, and was plugged into a heavy industrial cord, that may have gotten unplugged momentarily? It had only been running for a few minutes when I heard it go poof! then let out the smoke. But either way, it cost me $35 in return shipping, and I ended up with a mislabeled 45a instead of the 60a I paid for. And the one I returned disappeared into thin air, just like the smoke it let out. So, no, I do not have any faith in pm's return policy.

And now I hear others have had similar experiences. So mine is not an isolated case. I'd be very interested to know how many folks have received the wrong unit? Or how many had to be returned because of T issues, or whatever. Powermax can boast all they want about a low return rate, but that convinces me of nothing. I can only go by my experience, which is likely more common than anyone wants to admit to.

That said, other than blowing up occasionally, or the company's inability to handle returns properly, they really are decent little units. ;)

Nobody would know about the thermistors if not for me, so it is all my fault! There are kabillions of happy PowerMax customers and my problems were over three years ago with the models back then. Which PowerMax addressed.

IMO just use your unit and enjoy. If you have a problem, use the warranty provided.

On a tech note per this forum, the thermistor is just one component in the 120v "front end", and it could be an "issue" and the "fix" could be changes to it or the rest of the "front end" or both.

I don't know if PowerMax changed the whole front end or just the thermistors to solve the problems back then, but they did something, so IMO you just have to use the unit as you would like a regular human and see how it goes. If it smokes, use the warranty, but don't be gun-shy because of me from some years ago.

BTW, I am told that PowerMax is working on a new design of the "front end" which does not use a thermistor at all.

MEXICOWANDERER wrote:
Could a soft start circuit be of any value with the thermistor issue?

I have no idea? It seems to be a combination of ac inrush and how much load is applied... at least that's what I've gathered from discussing this with BFL. But so far, connecting to the bank 15 minutes after powering up the pm4b-45 appears to have no ill effect... but I do need to inspect the T, to be sure. And that may be with an upgraded T?... so I need to do as BFL said, and find out exactly what T is in this thing.

And then there's the pm3-75 which I have not tried charging with, yet. So it may not respond well to my waiting 15 minutes, and then connecting to the bank? But I'd rather take the better-safe-than-sorry route, and look into upgrading its T before trying it.

The thing is, as long as the bank is depleted deep enough, Vbatt remains well below Vabs during boost, anyway, so the whole 15 minute +1v boost thing isn't an issue. However I do not normally cycle my batts that deep. And I'm still not exactly sure at what dod Vbatt will rise above my Vabs setting during boost.

The bank is down to 66% at the moment, so I will be doing an overnight charge tonight. I'm pretty sure that's low enough to make the 15 min boost issue moot, so I'll fore-go waiting the 15 minutes before connecting the bank. I do know it's an issue in the 75%+ range, though.

Anyhoo, that in no way answers your question :(

Agreed. Batteries can actually accept might higher amps than what most people think if the voltage delta is great enough.

The duration that they can accept them is a different matter, but if a '100 amp' charger outputs 75 amps for an hour before before the amps begins to taper, then the batteries could certainly accept more than 75 amps initially.

joel,

Two of my 6's (215Ah) easily accept 45a to over 80% soc, at less than 14.8v... x2 that's 90a to over 80% soc. Not knowing the capacity of your 6's, my guess is your 6's should have no problem accepting 100a, if below say 75% soc, provided the voltage is set high enough.

I called Randy to ask if one was available, and he said he could get one and it was $20 more than the 75 amp adjustable. I checked my invoice and also the sticker on the unit, both say 100amp. I tried testing at home, but figured I just hadn't hit the batteries hard enough to see max output before I left on a trip.

Out on my trip, I definately got them low enough, and no matter what voltage there was no pushing more than 75-76 amps according to my Victron meter.

I've got 16" of 4 gauge wire and 4 brand new GC2s from Sams. Considering I could get 80amps from 2 Vectors hitting 4 12v Walmart GRP 27s under less depletion, I am sure I should have seen more.

I just left Randy a voicemail to see what he knows. Randy's always seemed to be good guy when I or anyone I've sent his way has dealt with him so now I will wait and see what he says.

Joel

While I do not remember my whole conversation with Errin as it was 5 months ago, I did ask about the thermistor issue and was assured they had solved it with a burlier part.

When I spoke with Errin just after Randy, at least he didn't try and tell me that the depleted batteries could not accept more than 75 amps, or practically call me a nitwit liar by saying my group 27 Northstar AGM couldn't accept over a hundred amps from my alternator, when depleted when I have the tools and desire to test,observe and measure such things.

Errin said send it back and we will sort it out instead of trying to convince me Black was white. The sorting process was time consuming, but part of that was It was not on my Dime, but a friends', who had/has a lot of other things going on, and my friend does not know a lot on this topic..

Right now the Adjustable 100 amp model and a non adjustable model, still in the shipping box, are sitting side by side on a bench, and I am not sure what is going on regarding getting the non adjustable model back to Powermax or the shipping costs refunded for shipping the original 75 amp model back, which was sold and labelled as a 100 amp model.

When somebody tells you are wrong, when you know you are not, yet they claim to be an expert, and are just a salesman with apparently little understanding of the product they are promoting, well.... I simply do not trust salesmen.

I wish I could have more confidence in recommending the Powermax adjustable voltage models. I've another project where such a model on a timer could really make the final design shine in performance, but instead, am just going to mate a Lifeline 31 to a PD9245, and hope one likes the other.

Perhaps I am a voltage control freak, but my taxed and delivered 127$ and slightly modified Meanwell rsp-500-15 does exactly what i tell it to, and can push 40 amps into any lead acid battery I care to hook it upto, and hold it at the desired absorption voltage for as long as I decide. It has also been perfect as a converter too. Powering all loads while holding my AGM at 13.61v.

It would be great to recommend a product which does not require modification to others seeking the same level of control required when one is seeking ideal battery longevity, and not just a 'one size fits all' compromise.

Powermax should really seek to sort out the discrepancies in their amp flavored models, and have a much better website with more information on their products, and make it simple to order the desired product.

I personally do not like speaking with strangers on a phone. I want to see the product I desire on my screen, and click 'Add to cart' and have it at my doorstep in a week, not jump through a bunch of hoops and middle men and recieve something different to what I ordered, then jump through a bunch more hoops to actually get what I ordered and have my intelligence insulted along the way by a salesmen middleman who should not be insulting anybody's intelligence.

Could a soft start circuit be of any value with the thermistor issue?

lol, well I must admit, neither my eyesight nor my manual dexterity are what they use to be :(.