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PowerMax PM3-55LK 12 Volt, 55 Amp Converter/Charger - Gobi Review

sshibly

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PowerMax PM3-55LK 12 Volt, 55 Amp Converter/Charger

I bought this from DonRowe, promptly shipped and they had the best price.

Reason I bought it - After some adult beverages, the 55 amp charge current and ability to adjust charging voltage looked very attractive.

Additional justification - found Battleborn batteries gave it ok to use for Li batteries.

Peeking at the manual I found that you can switch it and use it as a benchtop PS.

Fast Forward few months, well outside return period and my EVE cells are here.

Decided to charge my fully depleted 280AH with PowerMax after adjusting the voltage to 14.2 volts.

Charging -
Worked as designed, started to charge at 50 amp, the EVE cells started to heat up a little.
Fan turned on and everything was looking good till RIGHT at 30 mins the voltage dropped to 13.5v.

Some peeking I found that the charge does BOOST charge at 14.2 v for ONLY 30 mins then drops to the lower volts.

Conclusion -
USELESS for my LIFEPO4 charging needs, I can't recommend it, unless you want to keep rebooting charger to reset it.


Future -
I called PowerMax and they said they have a new line of improved PM3s coming out in March. Unfortunately, these might have a times charging function too.


Alternate -
You could set it to constant voltage output mode and use it to charge and pray that BMS cuts off or ask your ex-girlfriend to watch it. :rolleyes:
 

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I attached 2 pics, one shows the charger chugging away at nearly 50 amps. 2nd shows the charging amps drop to nearly zero as the batt volts exceeded the absorption volts.

I stepped away to buff my nails and the silence, aka no fan noise caught my ear and I walked back to my MIT certified lab [plastic folding table from costco] and the leading zeros on the clamp on Amp meter gave me quite the shock.
PowerMax owes me a couple of depends and a Star Wars jammy pants :oops:.
 
Decided to charge my fully depleted 280AH with PowerMax after adjusting the voltage to 14.2 volts.

Charging -
Worked as designed, started to charge at 50 amp, the EVE cells started to heat up a little.
Fan turned on and everything was looking good till RIGHT at 30 mins the voltage dropped to 13.5v.

Some peeking I found that the charge does BOOST charge at 14.2 v for ONLY 30 mins then drops to the lower volts.

Conclusion -
USELESS for my LIFEPO4 charging needs, I can't recommend it, unless you want to keep rebooting charger to reset it.

Alternate -
You could set it to constant voltage output mode and use it to charge and pray that BMS cuts off or ask your ex-girlfriend to watch it. :rolleyes:
The 3 stage charging and fixed voltage modes are documented in the manual.
How would you expect this product to work?
What functionality would make it useful?

I have the 24 volt 25 amp version and its worked quite well for me.
During top balance I used the fixed voltage mode to quickly get my cells nearly full and then a buck converter to top each on off.
Then I used the converter again in fixed voltage mode to recharge the cells after the initial capacity test.
The I switched to 3 stage mode for normal operation 28.8VDC for 30 minutes, 27.0VDC for 12 hours and 25.6 VDC float. I will use one of these https://www.canadiantire.ca/en/pdp/noma-outdoor-heavy-duty-24-setting-timer-1-outlet-0528845p.html to power cycle the converter every 24 hours.
 
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According to sshibly, "I found that the charge does BOOST charge at 14.2 v for ONLY 30 mins then drops to the lower volts."
Personally I basically ignore phase 1 as it is so short.
As long as my battery doesn't get to cv during phase 1 it not relevant to my use case.

The converter does have tunable fixed voltage mode though which has its uses.
 
Decided to charge my fully depleted 280AH with PowerMax after adjusting the voltage to 14.2 volts.

Charging -
Worked as designed, started to charge at 50 amp, the EVE cells started to heat up a little.
Fan turned on and everything was looking good till RIGHT at 30 mins the voltage dropped to 13.5v.
13.5 volts will get your batteries pretty darn close to full.
13.9 will get them full.
I suggest you configure the converter to do 3 stage charging with the 30 minute boost phase set to 14.6 which means phase 2 will be 13.9 volts for 12 hours.
 
13.5 volts will get your batteries pretty darn close to full.
13.9 will get them full.
I suggest you configure the converter to do 3 stage charging with the 30 minute boost phase set to 14.6 which means phase 2 will be 13.9 volts for 12 hours.
Good Point - I don't myself charging any batt for 12 hours, lol. Hence the fixed volts mode is more attractive.

It is not a hook up and forget it about it [big fan of Ron Paul], hence my thumbs down.
 
You can play with the voltage so that it takes longer to charge your battery.
13.4 volts will get your battery ~90% full and it will take longer.
Its also considered relatively safe to leave your battery exposed to 13.4 volts or 3.35 volts per cell indefinitely.
 
s..Joey, Yes, that will work.

Say my 280AH cells are at 30% SOC,

I yank of the volts to max, that will raise the boost voltage and raise the absorption voltage.
I will test it out tonight,
 
s..Joey, Yes, that will work.

Say my 280AH cells are at 30% SOC,

I yank of the volts to max, that will raise the boost voltage and raise the absorption voltage.
I will test it out tonight,
I wouldn't exceed the per cell limits in the boost phase.
 
PowerMax PM3-55LK 12 Volt, 55 Amp Converter/Charger

I bought this from DonRowe, promptly shipped and they had the best price.

Reason I bought it - After some adult beverages, the 55 amp charge current and ability to adjust charging voltage looked very attractive.

Additional justification - found Battleborn batteries gave it ok to use for Li batteries.

Peeking at the manual I found that you can switch it and use it as a benchtop PS.

Fast Forward few months, well outside return period and my EVE cells are here.

Decided to charge my fully depleted 280AH with PowerMax after adjusting the voltage to 14.2 volts.

Charging -
Worked as designed, started to charge at 50 amp, the EVE cells started to heat up a little.
Fan turned on and everything was looking good till RIGHT at 30 mins the voltage dropped to 13.5v.

Some peeking I found that the charge does BOOST charge at 14.2 v for ONLY 30 mins then drops to the lower volts.

Conclusion -
USELESS for my LIFEPO4 charging needs, I can't recommend it, unless you want to keep rebooting charger to reset it.


Future -
I called PowerMax and they said they have a new line of improved PM3s coming out in March. Unfortunately, these might have a times charging function too.


Alternate -
You could set it to constant voltage output mode and use it to charge and pray that BMS cuts off or ask your ex-girlfriend to watch it. :rolleyes:
There is a switch on the side to allow fixed voltage.
You will need to roll your own charge termination logic though.
Which I have done and described in this thread https://diysolarforum.com/threads/adding-charge-termination-logic-to-an-rv-converter.24061/

50 amps into an eve cell is just slightly under 0.2c which is pretty much optimal in my opinion.
 
Both are designed properly. It is your battery bank that is way out of balance to begin with.

Most high quality chargers are designed to hit at least 14.2v. The reason for this is that a bms with it's weedy little fets/balance resistors typically fire off at 3.5 to 3.55v (or should). For a fine balance, not gross.

But if your bank is way out of balance, and lets say it's a 400ah capacity, and only 500ma little bms bleeders/fets, well that's going to take waaaay too long to accomplish anything useful, hence the timeout to prevent one from spending a week doing so. The degradation clock is ticking the more time you spend in the upper knee.

So the manufacturers know what they are doing, and are protecting you and your investment from yourself. :)

If a bms only has a "dead man" protective bleeder at say 3.8v, then it is up to YOU to make absolutely sure your bank is at least relatively balanced to begin with by other diy means.

OR, if using a drop-in with no access, you should complain to your dealer / manufacturer that your bank was slapped together with badly unbalanced cells to start.
 
I wish I had seen this sooner. Did the PM3 actually reach the set absorption voltage? Or did the BMS cut off early due to poor cell balance?
 
You know I'm sorry to sound like a kill-joy. But if you look at it differently, you might consider it a diagnostic tool when this happens.
 
I learned a lot here,

I have to correct the TYPO above for everyone

I am NOT a fan of 100 SOC,
I charge my batts to 90% max and drain them to 30% ish, yes lot capacity but I size my batts for it.
 
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