diy solar

diy solar

New PowerMax Lithium Series Converter/Chargers

At present there is no solar. I would like to get 400 watts on the roof if it were me. Its only a 25 foot RV so space is limited with the AC unit and skylight and fans, etc.

I really need to get a good wiring diagram of the RV ( 2015 Thor 24SA ) to see what isolator is installed for alternator charging. The stock unit may provide so little charging that taking that into account may not be of concern. I read somewhere that ideally 30a may be provided but I cannot verify that right now.

As always an energy audit is the best solution and I am winging it at the moment. This all started out after being told that on an overnight here in Maryland, that running the propane heater pretty much killed the batteries. Taking into account 6-8amp draw on on the 160ah total/80ah usable batteries, adding in running lights for a bit and other parasitic draws, the batts were more than likely taken to or below 50% of the 160ah.

I have a spare Renogy battery monitor that I was going to add inline to get a better idea of capacity and draw.
 
That would be my guess on consumption. And if they're not new batteries they may not be putting out or holding full amps either. They're all great when they're new, eh??

Roof space is always a challenge. I spent a lot of time on my roof trying to figure out what would fit. I didn't really want panels near the front just for windage. And I was always trying to figure out how I would walk around them once they got mounted up there. I was going to take advantage of some cheapo grid-type ones from SanTan since we were over there over the holiday, but couldn't figure out how to situate them on the roof. The two 50x26 ones in 215A turned out to fit really nicely, and with my 160W 'suitcase' it gets me pretty darn close to 600W. I'm pretty sure I can make up my overnight use within 3 or 4 hours of good sun.

As far as I know the isolators simply combine the two banks - chassis/starter and house - when the ignition is turned on, or when the boost button on the dash is pushed. That's how mine is. But I have also heard they limit charging to the house until the chassis is fully charged, but not sure how that would or could happen. I really think they just combine the two banks. You should be able to test that with a volt meter, or a clamping current meter. I decided I didn't want to futz around with alternator charging, with expensive battery pack and an old GM alternator, I just didn't want to deal with it, so I took the isolator out and put a bus-bar there instead, combined the chassis loads, chassis battery lead, and generator lead.

What is interesting is how they split up loads on house verses chassis on my winnebago. The isolator/combiner had the chassis battery lead and load items on one side, and the house lead on the other to combine them. The house lead then went over to the remote battery cutoff switch, on the other side was the lead to the house loads, and the generator.

So the chassis battery powers the slide-out motors, electric entry step, power awning, and leveling jacks. The house side gets the lighting, fridge board, water heater board, and furnace blower and controller. It's like they assume you'll start the engine and then run all the stuff in to depart - slides and jacks, awning, etc. Same with deploying - I keep the engine running till everything is out and setup. The slide out motors especially run much faster with the engine running. Voltage sag and wiring runs combine to lethargy. LOL

What I found out exploring all the wiring and thinking about what options I had, I found the electrical compartment under the fridge is where the converter was - I also installed the inverter there. The converter is on it's own circuit, along with the 120V fridge outlet. But the 12V house lead that came over to this compartment to a post was 6awg wire, which was probably enough to feed the 600w inverter (5A max), but I didn't like the converter/charger on the same 12V lead, and it was all fed by a 55A 12v circuit breaker. So I left that wiring in place, and ran a direct 4awg wire to the inverter with it's own 80A fuse. Then moved the converter up front under the settee where the new lifepo pack will be. Now the converter is on the receptacles circuit which is also a 15A, so I decided to put a switch on it so I could turn it off if wife is gonna plug a hair dryer in or other hi-amp appliance. They have all the 120V outlets on one circuit which is kind of a bummer. We'll get by.
 
So you bring up some great points about what is run on chassis and what is run on house. With that being said I have had other thoughts about a parallel system. Leave everything that exists alone as much as possible. The AGM's can hang under the steps and get cold, I don't care.

If there were still some of the Bluetti AC200s that were refurbished for $650 I would say just buy one of those and use that but at $1700 for a new one, I don't think so. Anyway thought about the following. Just dedicating a few critical circuits; like the furnace blower, to a higher capacity system and leave the rest of the electrical alone, for the most part. Provides additional power for where it is really needed and still have the 160ah of AGM.

(2) Ampere Time 100ah batts stored inside and climate controlled - $800
SunGoldPower 2000w inverter/charger - $600
Victron 100/30 MPPT - $200
(2) 200 watt panels - $400

This may make things more complicated as need to make sure if on a 15amp shore power that both the RV charger and the new Inverter/Charger are not drawing too much at the same time. Again these are just thoughts and not my wallet. Like to throw some chum in the water and see who calls the ideas stupid. :)
 
As far as I know the isolators simply combine the two banks - chassis/starter and house - when the ignition is turned on, or when the boost button on the dash is pushed. That's how mine is. But I have also heard they limit charging to the house until the chassis is fully charged, but not sure how that would or could happen. I really think they just combine the two banks. You should be able to test that with a volt meter, or a clamping current meter. I decided I didn't want to futz around with alternator charging, with expensive battery pack and an old GM alternator, I just didn't want to deal with it, so I took the isolator out and put a bus-bar there instead, combined the chassis loads, chassis battery lead, and generator lead.
Found some info after you provided how your RV functions as it was very enlightening. Thanks for the hint to investigate further.

When the motor home engine is not running, the chassis and auxiliary batteries are
kept separated from each other within the electrical system through the use of a battery
isolating controller. The controller prevents the auxiliary batteries from discharging the
chassis battery when the motor home is parked.

  1. Delays connecting the auxiliary batteries to the charging system for approximately 15 seconds, to allow the alternator time to reach full charging ability.
  2. After this initial time delay, if the alternator has come up to full charging ability, (13.2 Volts) the isolator will electrically connect the auxiliary and chassis batteries together for charging.
  3. If the charging voltage drops below 13.2 Volts for a period of 4 seconds due to low idle speed and or excessive load, the isolator will disconnect the auxiliary batteries until the voltage returns to a level of 13.2 volts for about 10 seconds.
  4. In the event the automotive battery is discharged, it will be necessary to press and hold the Start Switch located in the dash.

The automotive chassis 12 volt system alternator supplies power to both the
automotive systems as well as any auxiliary battery if equipped, and directly to the
motor home living quarters while the vehicle’s motor is running.

The alternator compensates for electrical usage in the vehicle, the power drawn by the
appliances, lights, fans and other 12 volt powered items as well as the charging of the
automotive and auxiliary batteries.

If the alternator isn’t keeping pace with the draw on the unit’s electrical system, while
driving down the road, it means you’re working in a negative mode: more power is
being used than the unit is putting out.

This means that you are taking power out of the batteries. If you draw too much power
from the batteries there may not be enough power left in the battery to start the motor
home or run any of the appliances when you stop for a break or for the night.

The alternator will charge at a higher rate right after the vehicle’s been started,
replacing the power used to start the vehicle, but the charging should quickly go back
to “normal” and hold its own even when you turn on lights or appliances.

When stopped at a campsite that allows you use of the shoreline, the 120 volt electrical
system will recharge your auxiliary battery.
Under heavy usage in warm weather, check the fluid level of those batteries that
require attention to fluids quite often. Low battery fluid level is very harmful to the
battery’s longevity.

If the alternator shows a discharge while the motor is running, turn off appliances and
lights to see if a charge comes on or if the alternator indicates “neutral”. Then apply
a drain on the system to see if a discharge returns. If a discharge persists, contact
your dealer.
 
Yep, that's an isolator-combiner solenoid. A source of some grief for regular RV'rs if they fail. LOL

We got by with two 6V golf cart batteries in series for the past 15 years, about half dry camping. We would run the generator if we needed 120V power, for air conditioning or microwave, or any other 120V use, which was not much. We are not TV-watchers. This year I decided to install a pure sine wave inverter so wife could charge her laptop, our phones, etc. Which led to more solar panels, more battery, more wiring, and on and on. LOL I mention this because your friend with the two 80A batteries might get along pretty well with a pair of lead-acid Trojan or Crown 220-240A golf cart packs. They hold up pretty well for light use, and good ones can be had for about $350 for a set. I'm sure you already know this. But alas, still only about 110-120A usable. I'm hoping to get more like 190 out of my lifepo pack, so about twice what we've gotten by with for all these years.

I got sold on lifepo here, even enough encouragement to build my own battery pack from 3.2V cells. I've gathered all the bits and pieces to build it, just waiting for the cells to arrive.

Up in Zion at the Ponderosa, dry-camped for a week, just 160w of solar. Did great and had a ball.

043.jpg
 
Looks peaceful. Wish I were there myself right now. :)

Part of the problem is I know he will, at different intervals, take one or two of his 4 daughters on a trip. I can only guess how much power a teenage girl might require, much less cell coverage.

I've built packs but with the prices that some LFP batteries are now and not having to wait 2 months to get the cells, unless you are building large 48v packs or power walls, not sure the cost effectiveness / time factor for the future. I like the DIY aspect of it myself but if I am going to send someone down the road, I'd rather not have a failure due to a bad crimp on a BMS wire and I look like the a-hole that left them stranded with no juice.

I did look at the Crown cells as an alternative. Need to see if there is a supplier close to avoid some of the shipping costs of lead.
 
So you bring up some great points about what is run on chassis and what is run on house. With that being said I have had other thoughts about a parallel system. Leave everything that exists alone as much as possible. The AGM's can hang under the steps and get cold, I don't care.

If there were still some of the Bluetti AC200s that were refurbished for $650 I would say just buy one of those and use that but at $1700 for a new one, I don't think so. Anyway thought about the following. Just dedicating a few critical circuits; like the furnace blower, to a higher capacity system and leave the rest of the electrical alone, for the most part. Provides additional power for where it is really needed and still have the 160ah of AGM.

(2) Ampere Time 100ah batts stored inside and climate controlled - $800
SunGoldPower 2000w inverter/charger - $600
Victron 100/30 MPPT - $200
(2) 200 watt panels - $400

This may make things more complicated as need to make sure if on a 15amp shore power that both the RV charger and the new Inverter/Charger are not drawing too much at the same time. Again these are just thoughts and not my wallet. Like to throw some chum in the water and see who calls the ideas stupid. :)

So, just for the sake of argument on how you could do it...
The ampere time batteries are $700 Frankly I think you only need one for that coach unless they're going to run a lot of inverter power.
A Xantrex 2000w inverter $365
Tracer N Mppt $120
Nature Power 215W panels on sale at HD - $154X2 = $308

These are acceptable reputable brands you could utilize.
You can use the rest for profit/markup.
 
So I opened up the PM3-55LKL and got all excited cuz there was another adjust pot in there with the board label of "VR2" - the one you can get to from outside the cover is labeled "VR1". Oh boy, this is the overall voltage adjust pot....uh no. It does nothing. I suspect it's voltage threshold at load or something - adjusting it in any charge mode does nothing. So I left it where it was. Played with the other pot again - in fixed-mode it adjusts from 12.75 to 16.25 volts. Left it back at 14.4 volts.

Looks like I'll start with 2-stage charging at 14.6/13.6, see how it does with the lifepo pack.

IMG_4175.HEIC
 
I'm looking at this converter as well for my LiFePO4 conversion in my camper. I'm going with 4S2P 200A or 230AH cells. It'll fit into my GC2 battery box. 400-460AH would be nice
Below is the email I got back from Graham over at PowerMax
-----------------
Thanks for reaching out to us, below is a quick description of the charge profile on the LKL unit and pricing, We have both in stock and available on the website, pricing includes free shipping too. If you have any questions please let me know

2 Stage Mode (Lithium Profile) - Factory Setting
Bulk - 14.6V - (start point can be turned up/down from 13-16.5V, float will adjusted by the same value)
Float - 13.6V
re-bulk - 12.8V

Load sensing is done on connection, if draw less than 10 Amp the unit will drop to float, if not then Bulk mode will run for upto 8 hrs or until Amp draw is less than 10A.
The Unit has universal input, 110~220Vac

This charger then has the standard 3 stage and single fixed voltage mode outputs as on the regular PM3 series, these can be selected via a switch on the rear of the unit, each mode is highlighted via color specific LED
-----------------
So, his email is incorrect?
2-stage is NOT adjustable? Since it's 2-stage mode that drops down if amps are less than 10, wouldn;t it automatically drop down if being measures while disconnected?

Thanks for opening that sucker for us to get a look.
I'll be emailing him back
 
2 Stage Mode (Lithium Profile) - Factory Setting
Bulk - 14.6V - (start point can be turned up/down from 13-16.5V, float will adjusted by the same value)
Float - 13.6V
re-bulk - 12.8V
Interesting if adjusted down could be:
Bulk - 13.8
Float - 12.8
re-bulk - 12.0

Need to calculate if the battery could get from 12.0 to 13.8 in less than 8 hours.
 
Interesting if adjusted down could be:
Bulk - 13.8
Float - 12.8
re-bulk - 12.0

Need to calculate if the battery could get from 12.0 to 13.8 in less than 8 hours.
You're assuming that the voltage offsets remain the same. If things are adjusted by a single pot, it's more likely that the voltages adjust linearly.
13.8 is 93.2% of 14.6. I'm guessing (based on electronics experience) that if you adjust 14.6 down to 13.8, the float voltage would be 12.86. I know it's a small difference, but it's there.
This is all assuming that the 2-stage mode is adjustable.

That is to be confirmed. The above testing though, doesn't bode well for adjustable 2-stage.
 
I'm looking at this converter as well for my LiFePO4 conversion in my camper. I'm going with 4S2P 200A or 230AH cells. It'll fit into my GC2 battery box. 400-460AH would be nice
Below is the email I got back from Graham over at PowerMax
-----------------
Thanks for reaching out to us, below is a quick description of the charge profile on the LKL unit and pricing, We have both in stock and available on the website, pricing includes free shipping too. If you have any questions please let me know

2 Stage Mode (Lithium Profile) - Factory Setting
Bulk - 14.6V - (start point can be turned up/down from 13-16.5V, float will adjusted by the same value)
Float - 13.6V
re-bulk - 12.8V

Load sensing is done on connection, if draw less than 10 Amp the unit will drop to float, if not then Bulk mode will run for upto 8 hrs or until Amp draw is less than 10A.
The Unit has universal input, 110~220Vac

This charger then has the standard 3 stage and single fixed voltage mode outputs as on the regular PM3 series, these can be selected via a switch on the rear of the unit, each mode is highlighted via color specific LED
-----------------
So, his email is incorrect?
2-stage is NOT adjustable? Since it's 2-stage mode that drops down if amps are less than 10, wouldn;t it automatically drop down if being measures while disconnected?

Thanks for opening that sucker for us to get a look.
I'll be emailing him back

Graham was going to get back to me with a response from his engineers/designers on adjusting the voltage on the unit. I have not heard anything since my original inquiry on December 14th.

After our initial call, he went out to their warehouse, pulled a unit off the shelf, plugged it in, and confirmed that only the fixed-voltage setting could be adjusted. When you switch back to either 2 or 3-stage it goes back to the default 14.6/13.6. Works the same regardless of what mode the unit is when plugged in. He called me back and admitted there was an error in their instruction manual, that was not how the design was intended, and he was going to get back to me with an update. Either with a system redesign, an update, or at least some kind of an answer.

I can confirm in 2-stage it switches to bulk immediately if there's no load - takes about ten seconds. A DVM will show 14.6, then it will drop to 13.6. I have not connected it to a lifepo, just to my FLA's, but they were mostly fully charged so I couldn't get any kind of feel for boost/bulk switching duration.

I figure worst case scenario I can use the fixed charging mode at somewhere from 14.0 to 14.6 when I need to charge, and simply shut it off when amps taper off to nothing. (EDIT: Now I recall him saying current is fixed amps when it's at fixed voltage - it acts as a straight fixed power supply.)

Graham mentioned these units get used on all kinds of odd applications, and the fixed voltage was used primarily as a direct power supply.

I would like to know what the second internal adjust pot does, for sure. The one labeled VR2. I have to assume it's 'voltage regulator' is part of the pot designator on the board. I played with it in various settings but nothing changed, so I put it back where I thought it was. Hope it doesn't change anything. It could be a re-connect volts or something like that, when a load is connected.
 
Last edited:
Graham was going to get back to me with a response from his engineers/designers on adjusting the voltage on the unit. I have not heard anything since my original inquiry on December 14th.

After our initial call, he went out to their warehouse, pulled a unit off the shelf, plugged it in, and confirmed that only the fixed-voltage setting could be adjusted. When you switch back to either 2 or 3-stage it goes back to the default 14.6/13.6. Works the same regardless of what mode the unit is when plugged in. He called me back and admitted there was an error in their instruction manual, that was not how the design was intended, and he was going to get back to me with an update. Either with a system redesign, an update, or at least some kind of an answer.

I can confirm in 2-stage it switches to bulk immediately if there's no load - takes about ten seconds. A DVM will show 14.6, then it will drop to 13.6. I have not connected it to a lifepo, just to my FLA's, but they were mostly fully charged so I couldn't get any kind of feel for boost/bulk switching duration.

I figure worst case scenario I can use the fixed charging mode at somewhere from 14.0 to 14.6 when I need to charge, and simply shut it off when amps taper off to nothing. (EDIT: Now I recall him saying current is fixed amps when it's at fixed voltage - it acts as a straight fixed power supply.)

Graham mentioned these units get used on all kinds of odd applications, and the fixed voltage was used primarily as a direct power supply.

I would like to know what the second internal adjust pot does, for sure. The one labeled VR2. I have to assume it's 'voltage regulator' is part of the pot designator on the board. I played with it in various settings but nothing changed, so I put it back where I thought it was. Hope it doesn't change anything. It could be a re-connect volts or something like that, when a load is connected.
Thanks for the feedback, Browneye. I figured I'd do the same. Keep it in Fixed voltage mode at around 3.45 V/cell and live with it. LiFePO4s can be floated at 3.45 with no issues and that's "around" 90% SOC anyway. I've got an email into Graham at PowerMax regarding the discrepancy. We'll see what happens.
I'm pretty curious about that VR2 pot as well. You've proved that it isn't the "2/3 stage mode" absorption voltage adjustment. It could the the current threshold where it drops from Absorption to float. It could be the Float voltage. Who knows. Let's hope that since you've contacted him earlier and my email, he might be able to get back to me/us with information.
 
Frankly, I don’t think he knows. I think he’s a marketing guy. We’ll see. :giggle:

I tried to google it, found nothing. :rolleyes:
 
I just called the powermax people and left a message. I'm looking for a response on the design as built and what was intended on the voltage adjust parameters and settings. In doing some research online there are some old RV threads that hashed this out years ago - and the converter units really don't seem much different from what they were a decade ago.

Evidently the founders were originally with WFCO and started another company in competition. And one of their primary retailers was BestConverter guy Randy in Alabama. Boy does he have some negative feedback. Anyway, I just ordered a class-T fuse and block from them, and they sell powermax converters under their own brand: Boondocker.

The other thing I want to know is how the fixed-voltage setting works. If there's a voltage drop to the load then I assume it will push max current up to it's rated capacity - the 55 amps or 100, whichever unit you have. But it seems like any other power supply in that once the load voltage rises up closer to the charger voltage the current would taper off as it reaches a matching voltage. Perhaps someone more knowledgable here could shed some light on this.

If this is the case, then setting the fixed voltage at 14.0 to 14.4 and letting it charge a lifepo pack until the current tapers off, then just shut it off.

Their older models only had a 15 minute boost charge at 14.6 and then the unit would drop to 13.6 for an absorption phase, and once the battery reached full charge it would drop to 13.2 as a float phase. This new charger doesn't seem much different, just that they've eliminated the FLA float setting. They also had their PM4 which had the fourth phase for equalization/de-sulfating. Graham claimed this new charger had a 4 hour boost duration if the pack had low voltage/low SOC.

For anyone with more interest on charging lifepo packs here's a pretty good blog from Marine How To - @Dzl has a link in his sig for these guys:
 
The other thing I want to know is how the fixed-voltage setting works. If there's a voltage drop to the load then I assume it will push max current up to it's rated capacity - the 55 amps or 100, whichever unit you have. But it seems like any other power supply in that once the load voltage rises up closer to the charger voltage the current would taper off as it reaches a matching voltage. Perhaps someone more knowledgable here could shed some light on this.

My PM4 works in constant voltage mode all the time, and it behaves as you describe. It will allow the battery to pull up to its rated current until the PM "sees" the set voltage, then it tapers current to hold set voltage.

If this is the case, then setting the fixed voltage at 14.0 to 14.4 and letting it charge a lifepo pack until the current tapers off, then just shut it off.

Yep, that would work.

Their older models only had a 15 minute boost charge at 14.6 and then the unit would drop to 13.6 for an absorption phase, and once the battery reached full charge it would drop to 13.2 as a float phase. This new charger doesn't seem much different, just that they've eliminated the FLA float setting. They also had their PM4 which had the fourth phase for equalization/de-sulfating. Graham claimed this new charger had a 4 hour boost duration if the pack had low voltage/low SOC.

When charging at 0.5C, LFP rarely needs more than about 30 minutes of absorption. When charging at lower currents, it needs even less time. That's part of the reason why I've been cautioning others not to waste money replacing perfectly good hardware when what they have will work 95% as well from a charging perspective and may also avoid potential damage from misguided implementations of LFP charging.
 
My PM4 works in constant voltage mode all the time, and it behaves as you describe. It will allow the battery to pull up to its rated current until the PM "sees" the set voltage, then it tapers current to hold set voltage.

My understanding with current is if there's nothing to draw it there isn't any. So when connecting to a discharged lifepo pack the difference between the pack voltage and the charger voltage would cause current to flow - up to the capacity of the charging unit.

Once that voltage differential gets very low the current stops flowing - the pack reaches full voltage charge state.

Am I correct in this logic on how it works?

In practical use, you set the fixed voltage on the charger to your desired SOC - say 14.2 or 14.4 volts. Turn on or connect charger when the pack needs to be charged, monitor charge current and shut off the charger when the current drops indicating the pack is near full SOC.

I have a clamping meter I bought for some reason, perhaps it was on an items list for building a pack. Seems like it would make sense to mount it more or less permanently on the converter charge lead to monitor charge current. Does that make sense?

410Iy8wAkSS._AC_SX355_.jpg


I also got one of the new shut meters from a forum vendor that I will mount in an easy to view location. It should keep track of SOC based on amps out and amps in:

kg-f%E7%B3%BB%E5%88%97%E4%B8%BB%E5%9B%BE-jpg.65153



And I have a Tracer Xtra SCC with a lifepo setting that also has a good display of PV and battery current. I'm thinking it will have better metering and abiliity to custom tailor a charging profile. I haven't even gotten to this stage yet.
 
When charging at 0.5C, LFP rarely needs more than about 30 minutes of absorption. When charging at lower currents, it needs even less time. That's part of the reason why I've been cautioning others not to waste money replacing perfectly good hardware when what they have will work 95% as well from a charging perspective and may also avoid potential damage from misguided implementations of LFP charging.

That 5% exception would perhaps be those converters that use a four stage charge profile, with the fourth stage being an equalization charge which would be bad for LiFePO4. That caveat to that is that the BMS should simply cut off charging at those voltage levels. The caveat to the caveat is that the BMS shouldn't be used like that and should only be the last line of defense.
 
That 5% exception would perhaps be those converters that use a four stage charge profile, with the fourth stage being an equalization charge which would be bad for LiFePO4. That caveat to that is that the BMS should simply cut off charging at those voltage levels. The caveat to the caveat is that the BMS shouldn't be used like that and should only be the last line of defense.

True if those converters actually use an equalization voltage. Many refer to equalization as a simple return to the bulk voltage (14.4, 14.6, etc.). Unnecessary and suboptimal, but not harmful.
 
My understanding with current is if there's nothing to draw it there isn't any. So when connecting to a discharged lifepo pack the difference between the pack voltage and the charger voltage would cause current to flow - up to the capacity of the charging unit.

Once that voltage differential gets very low the current stops flowing - the pack reaches full voltage charge state.

Am I correct in this logic on how it works?

No. current flows until the voltage differential is ZERO. It will never be zero. it will pass micro-Amps of current to hold the battery at 14.4V or whatever, and that is bad for the cells. They should be allowed to settle after fully charging.

In your scenario, the charge would need to be manually terminated.
 
Back
Top