Adjustable Voltage Boondocker Converter Question

Well, I threw together a short 4ga pigtail, and installed a 50a switchable circuit breaker between the pm4b's positive output and the 2ga positive cable to the bank. I set Boost at 15.7v and Vabs at 14.7v. Resting ocv was at 12.72v.

I fired up the gennie, ran it for a few minutes on full throttle, then plugged in the pm, with the circuit breaker open. Then I turned on the eco, to save gas and reduce the noise. After the pm did it's 15 minute thing, I turned off the eco, and closed the circuit breaker.

Voltage dropped to about 14.3v, then quickly rose to about 14.6v, then started rising slowly from there. I then turned the eco back on. At last glance things were at about 8a @ 14.67v.

So everything seems normal.

I suggest both of you get hold of Errin again and see where things stand. (He has read this thread)

There may be a "fix" to kill the 15min thing by doing something on the circuit board (snip something) but I want to get further confirmation before posting it here. That would also kill the three-stages apparently. More on that if I get solid info. That would solve jrnymn7s problem I think.

Thanks for sharing LY,

So I'm not the only one to get a mis-labeled unit (45a labeled as 75a)... definitely a Quality Control issue, there.

Did you order one of the older adjustable units or one of the newer ones?

My Powermax story goes like this.

Ordered a 100 amp adjustable voltage unit. The UNit which came had a 100 amp sticker right on it with 3 40 amp external ATC fuses.

Once it arrived, a pair of New and fully charged group 31 AGM batteries was taken down to 50% Via a 10 amp load for 10 hours.

The powermax, when attached, and cranked all the way up, was not capable of more than 75 amps.

Randy tried to tell me that 2 AGMs at 50% could not accept more than 75 amps. Effing BS!

Then measured the unit and Randy said yes that is the 100 amp version, bla bla bla, talk to Errin at powermax.

Errin said send it back, if it tests at 75 amps we will ship you a new one and refund the return shipping.

Over a month later a PM3 100 NON adjustable voltage model arrives. It has 4 40 amp external fuses and is an inch longer. It is never unboxed as there is no adjustable voltage.
Another month goes by and the adjustable voltage model arrives, also 4 40 amp external fuses, and an inch longer than the first '100 amp' model

It tests at 94 amps and line voltage is the suspected culprit for the 6 missing amps.

So my take is that Either Randy is unaware he is selling 75 amp models as 100 amp versions or is ignorant of it. Telling me that two depleted group 31s AGM's could not accept more than 75 amps infuriated me and made me lose all respect for him. Simple dishonesty or complete ignorance, one or the other, nothing else.

I would recommend skipping bestconverter.com entirely and placing any orders directly through Errin@powermax by phone. Screw the lying or ignorant middle man. All these adjustable voltage models are special order type things, not done by Randy, but by PowerMax.

My friend whose money was spent acquiring this Powermax tried to get an electronic timer installed for all the trouble along the acquisition of the correct product path, and they said they could not make it work properly.

I have a spring loaded 12 hour timer for the 94/100 amp adjustable voltage model.

The return Shipping was never reimbursed, and the automatic model still sits on my friend's bench next to the adjustable voltage model, so the drama is not quite sorted out yet. I am not sure if his card was charged twice, or if Powermax wrote off the non adjustable model.

So I would not order any Model without a means to test its maximum output on arrival. There is some dishonesty or ignorance going on with regards to what stickers are placed on what models.

If we had no Clamp on Ammeter we would have believed the 75 amp model was the 100 amp model like the sticker says.

I wonder how many out there believe they got what they ordered and have the lower amp version instead.

Such a shame, as this is one of the few products available which can fully charge any given battery in the shortest amount of time. But will you get what you order or have some smoke blown up your keester and be told it is a barb e que?

The adjustable voltage models have NO stages. Nothing Automatic. No boost/bulk.absorption/float, just a single desired end voltage, and it will take the battery up there and hold it forever. The user must determine the ideal absorption voltage and how long to hold it there.

lol, yeah it's like dog training... it's rarely the dog that needs to be 'edumicated'

I'm having difficulty seeing any difference between say having the converter all hooked up, and then turning on its power switch (or plugging it in)... and having it all hooked up, and then closing the circuit to the batteries. In fact, I would think the latter would be less stressful on the thermistor? It may come down to the overall power needed to meet the load, as you say.

But my thoughts return to the fact that the thermistor does not blow, even when the pm4b-45 're-starts', following the 15 min boost thing, on a depleted bank. When it does so, voltage starts to drop to whatever surface charge exists, and current drops to zero. But then it comes back on at 14+ volts and 45 amps. This has no ill effect. I fail to see the difference between this scenario, and applying a load after the unit has been basically sitting idle for 15 minutes.

From what the PM guy told me, the in-rush stress on the thermistor is higher when I start the unit with the knob turned right up at 15.2v or whatever in cold weather, and it kicks off at its 100amps. It would be less stress to start out at a lower voltage for the required 120v input VA/watts.

I notice my VEC1093DBD set to 40a kicks off at lower amps and quickly steps up to its 40.4a instead of hitting 40.4 at first. Maybe that's why.

I don't know if it matters if the unit is already going at 13.6v at some amps and you jack up the voltage to 15v and now get more amps. I have done that and it doesn't seem to bother the charger.

The Honda conking out was what caused all this in the first place with me. I did not warm it up first and it got hit with the 100amper at 14.8 VA demand and the engine conked out immediately--the breaker didn't pop as such, but it lost power with no engine of course.. I had to restart the Honda engine to get 120v again and that gave the charger a hot restart (ie thermistor already hot) It takes longer than they say before it is safe to do a restart too. It is supposed to be ok again after a minute or two but I had trouble after 15 minutes waiting when I was doing some tests on that with the lid off so I could see the thermistor. Had a thread on that a couple years ago.

It came out in the long thermistor thread that I should connect first and start the unit afterwards too, so there is less stress. That applies to me when I have the charger connecting with clamps and not like a converter that is already wired to the batteries.

I have been getting by ok since then with no more thermistor trouble now I have learned how to behave :)

BFL,

I could see maybe the Honda's eco-throttle having an adverse effect on the 120Vac power to the pm, with that momentary drop, then jump, in rpm. But maybe if the eco was left off 'til after the 15 minutes, the 120Vac power would not fluctuate too much? I guess I'll know soon enough.

I know it's recommended to first connect a charger to the batteries, and then plug in to the 120Vac power, but I think that has more to do with not causing sparks, and/or not wiggling the connections around while the charger is running. But simply closing the switch between charger and batteries should not cause any problems.

Mex,

As far as I know, the thermistor issue is solely an ac input one. It is the inrush of 120Vac into an already hot thermistor, and has nothing to do with the units dc output. Otherwise, every time a significant 12v load was suddenly applied to an older powermax converter, or the charger portion of the converter-charger kicked on, the thermistor would blow. But this is not the case.

Pre-charging, to raise battery voltage would not help, in this case. However, this was my solution to the Turnigy 1080w shutting down, due to a current spike, over and above its current limit, at start up. If you re-call, the battery bank presented such a large load that the current would momentarily spike above the power supply's 60a limit, and it would shut down. So, it has current limiting protection, but not the type suitable for using the supply as a battery charger. I forget the names of the two basic types of current limiting, but this is what separates suitable power supplies from non-suitable power supplies, when it comes to using them as chargers, and not simply as a power supply. The cheapowatt seems to lack any sort of current limiting, whatsoever.

jrnymn7 wrote:
So what you're saying is, by running the pm for 15 minutes, with no load attached, could cause the thermistor to warm up enough that when the load is applied, the thermistor could blow? That would not be good :(

However, when the 15 minute thing ends, the unit actually stops outputting for a couple seconds, and then resumes. I always know when this has happened because the Honda's eco-throttle reacts accordingly. This does not blow the thermistor... so perhaps it is only a disruption in the 120Vac power that causes the thermistor to blow???

I would think it would be no different than the converter sitting idle, while plugged in to 120Vac pedestal power, and then suddenly having to output whatever current necessary to meet whatever 12v load is applied; be it the battery bank, or a 12v appliance.

I really don't know. Interrupting the 120v is bad which is a hot restart. Starting the charger and then connecting it makes for a sudden stress that kind of acts like a hot restart maybe--not sure about that.. and that was with my 100 amper set to 14.8 so the stress is higher then for watts. the newer models with lower amps and a better thermistor may be fine. I don't know.

Here comes the Cheapowatt again :)

For 22 bucks you can set this power supply at say 13.4 volts and 1st stage it for a minute or so before exposing those thermistors. Staging charge voltage values is how I am operating the BORG. In my case it's the breaker that suffers from inrush.