Replacing OEM batteries with LiFePO4's

[smiller]

You mean slide it out so you can get to the pot, but don't disconnect it - run it and turn the pot while measuring the voltage?

Not quite that easy I'm afraid. Basic steps are:

1. Remove AC and DC power from the unit.
2. Remove the top front panel (that covers AC breakers) and and disconnect AC and DC power leads to the charger unit.
3. Remove the charger unit and place on bench.
4. Drill out the rivets that attach the top cover.
5. Remove cover, pot is at rear of circuit board.
6. Apply AC power to the unit and set to desired DC voltage.
7. Reattach top cover with sheet metal screws and reassemble everything.

Sounds complicated but it's really only a 30 minute job. There is a large range of adjustability but I can't say for sure whether you can get up to 14.6 volts.


Also, if size is a consideration you might also look at the Iota DLS chargers which have a smaller form factor. They are heavy duty units that will provide rated output without breaking a sweat.

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[Peter Tourin]

I'll probably give that a try - I wonder if I could ring Parallax and find out how high they'd go...

As for the Iotas, the size is great and they are apparently more efficient than the PD's, as the PD7060AL (60A ouy) is rated at 1000W input draw while the DLS-75 is also rated at 1000W. But they're 13.6v out, 14.2 when jumped. Close - I wonder if they also have a voltage adjustment pot inside. Probably worth a phone call to them.

 

[smiller]

The DLS models are voltage adjustable via a pot inside the unit. I know they will go to 14.6 because I have set mine to that (wanted higher absorption level setting .)

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[israndy]

If they need such high voltage from their charger what are you going to do when driving? Are you going to adjust the alternator output? How about solar, are there controllers yet that handle LiFePO4's? And freezing, has that been mentioned yet? I am following another board that has done the lithium conversion, their pack has little heaters that use some battery energy to keep the pack above freezing as that appears to be BAD for the chemistry. That seems like a drag, especially if you don't have solar. I can see a day when the RV is buried in snow and the pack uses up it's charge running the heaters and STILL freezes. Although snow is a great insulator, so perhaps you would save yourself the freezing temps. My Serenity has the batts outside in a hanging cage, so very exposed to the weather. I just put another set of flooded 6Vs in, I had hoped that some tech like you are experimenting with would be available by now so I could avoid the flooded. I do have solar and I am counting on keeping them charged and topped will allow them to last many years this time. Glad they are cheap, @$89

-Randy

 

[smiller]

If they need such high voltage from their charger what are you going to do when driving?

I would ask Smartbattery tech support if they feel 14.1 volts is adequate. If not then there are DC-DC converter systems that can provide a higher voltage while underway, but it would ne nice to avoid the extra hardware if possible.

 

[Peter Tourin]

Checking it out with SmartBattery - I'll let you know.

 

[electrikman]

On the question of cold weather driving and camping and batteries comfort you have to consider insulating that battery box and somehow keep it warm (venting furnace?) .The good news is there is no worry about venting for non wet batteries with smart batteries or even gel banks.
So a nice airtight padded cell for the juice boxes.
I had a real issue with road salt and sand completely covering all my six back gels batteries in serious winter driving conditions.Keep those terminals clean!

 

[Unity Traveler]

Peter, same advice I give to everyone when the subject of charger/converters and inverters is raised. Talk to Randy at bestconverter.com. Click here to see his page about Lithium Ion charger/converters...

I followed Don Horner's advice & called Randy about our Parralax 7300 Converter/Charger & he recommended I go with the Parralax 7300 Series Upgrade Kit which I did.

Did not replace the stock Interstate Batteries yet, but plan to in another week once we return home. The current Interstates do not hold a charge long enough now after two years to even run the fan all night before getting down to low 12's which is at about the 50% discharge rate.

Here is the upgrade kit info for the 7300 Series Parralax: http://www.bestconverter.com/MagnetekParallax-63007300-Upgrade-Kit_c_64.html

Or go to Best Converters & click on the first item on the left for the upgrade if interested.

 

[Peter Tourin]

Lithium batteries take different charging voltage than do standard or AGM batteries, so I can't use that upgrade. But even for standard and AGM's, the stock charger in the Parallax 7300 isn't wonderful, and that upgrade kit gives you a good multi-mode charger. So you may want to consider it when you get new batteries - but it won't help me with lithium batteries.

 

[israndy]

he recommended I go with the Parralax 7300 Series Upgrade Kit

I was sorry that I did this upgrade because I now have the solar charge system that does all that the Parallax does (3-stage and eq). I only ever need the converter when I am at a campsite. If I had instead done one of those DC-DC 3-stage converters I could have gotten the better charge from both my converter AND the alternator...

-Randy

 

[Peter Tourin]

I just talked with an engineer at Parallax. The converter in the 7300 puts out about 13.8v at no load, and goes down to around 13v at full output. I asked if I could get 14.6v no load by opening the converter and adjusting the internal pot, and he said yes, though he was pretty cautious about it. If I were to do that, my understanding is that I could charge my lithium batteries tolerably well as an interim measure, until I decide what charger I'm going to get for the system.

One of his cautions was that while charging that way, I'd be pushing my whole DC system up to 14.6 volts - the charger/converter is putting out that voltage to charge the batteries, and the batteries are connected to my whole DC system. He was worrying that some of the DC equipment might not like the high voltage. But in any flooded cell or AGM system, that same thing happens during charging, when you're going up to the 14.2 - 14.4v area. I have to assume that most of these devices will run on a range of voltages from around 11 to around 16 volts.

 

[OrioN]

You can charge the LiFePO4 very effectively in the 14.0V to 14.2V range.





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[smiller]

Yes, Peter did you get a response back from SmartBattery regarding compatibility with a lower (than their published spec) charging voltage?

 

[OrioN]

If you are contacting Smart Battery, the most important and only question to ask is this...

...what is the voltage (cell or bank level) that the BMS starts its 'top' cell balancing at?

Why? Cause LiFePO4 cells, and unlike lead acid, will drink/accept current as if you were pouring from a bucket, and at any voltage range really above it's nominal of 13.4V (yes... 13.4V is the NEW 12.8V). This cell balancing number is the important 'number' really as you want your charger(s) to exceed this to have the BMS do some requisite balancing. My current BMS will start it's balancing at ~3.45V (cell) or 13.8V (bank).

Interesting enough, and again unlike lead acid, and to demonstrate the LIFePO4 chemistry and technology is entirely different, when or while a 14.6V charge is applied the battery monitors will exhibit the cell voltage state or in actuality the SOC. Only when the bank reaches its full capacity, will the bank voltage (and the monitors) rise to meet the charge voltage. A lead acid battery will pretty much exhibit the charge voltage at any given moment. BUT, if a CC (constant current) charger (ie, alternator or Li charger that requires a BMS signal to start/stop) is applied, the bank voltage will continue to rise ABOVE the charge voltage...and this is why or one reason why a BMS is required, to stop the 'run away' that causes the cells to burn.

One need to forget everything one knows abooot lead acid.



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[Peter Tourin]

Thanks OrioN - understanding this is slow going! I just phoned Progressive Dynamics. Their tech support engineer says that their 9100L series chargers hold a steady 14.6v. The battery BMS (internal, in the case of the SmartBattery's) will open the battery relay at some point (when any of the 4 cell banks reaches 3.9 volts, in their example). Then the balancing circuitry does its thing, and as the cells balance and the voltage of the highest cell drops, the relay closes again and the charger is reconnected. According to PD's tech support engineer, the charger always holds the house DC system at 14.6 volts. I asked him if that's true after the batteries are fully charged and he said yes - the batteries drop out of the circuit and the house DC system is then being run off the charger.

I asked if they assume that the DC house system will be happy at 14.6v, and he said that maybe some old-fashioned bulbs will have reduced life, but in general the answer is yes. He pointed out that many non-lith chargers go to 14.2 - 14.4v, and a few tenths one way or the other shouldn't have much effect. I tried to get some tech white papers from them on the charger series, but he said none were available.

I hope I'm understanding this and stating it correctly - please chime in if I've got anything askew - now that I've bought the batteries, I'm trying as quickly as possible to make sure I understand what I've got. They should arrive this afternoon - I should have them in the RV this evening. And if they're really shipped at 50% SOC or thereabouts, I just realized that I don't have a good way to charge them - unless I use my regular standard/AGM car charger. I assume the present Parallax 7355 won't do much. It also sounds like the Sprinter alternator output will be enough to charge them on this weekend's first trip - it'll be VT to PA on Friday/Saturday, then back Sunday afternoon.

Do you happen to know anything about battery monitoring for these batteries? I haven't even started to think about that issue yet.

 

[OrioN]

Thanks OrioN - understanding this is slow going! I just phoned Progressive Dynamics. Their tech support engineer says that their 9100L series chargers hold a steady 14.6v. The battery BMS (internal, in the case of the SmartBattery's) will open the battery relay at some point (when any of the 4 cell banks reaches 3.9 volts, in their example). Then the balancing circuitry does its thing, and as the cells balance and the voltage of the highest cell drops, the relay closes again and the charger is reconnected. According to PD's tech support engineer, the charger always holds the house DC system at 14.6 volts. I asked him if that's true after the batteries are fully charged and he said yes - the batteries drop out of the circuit and the house DC system is then being run off the charger.

I asked if they assume that the DC house system will be happy at 14.6v, and he said that maybe some old-fashioned bulbs will have reduced life, but in general the answer is yes. He pointed out that many non-lith chargers go to 14.2 - 14.4v, and a few tenths one way or the other shouldn't have much effect. I tried to get some tech white papers from them on the charger series, but he said none were available.

I hope I'm understanding this and stating it correctly - please chime in if I've got anything askew - now that I've bought the batteries, I'm trying as quickly as possible to make sure I understand what I've got. They should arrive this afternoon - I should have them in the RV this evening. And if they're really shipped at 50% SOC or thereabouts, I just realized that I don't have a good way to charge them - unless I use my regular standard/AGM car charger. I assume the present Parallax 7355 won't do much. It also sounds like the Sprinter alternator output will be enough to charge them on this weekend's first trip - it'll be VT to PA on Friday/Saturday, then back Sunday afternoon.

Do you happen to know anything about battery monitoring for these batteries? I haven't even started to think about that issue yet.

BMS Cell Balancing should be occurring before 3.65/14.6V stage. This is to ensure that some balancing occurs while the charger is still active, as many shut down(LI specific) at this voltage; and while this is happening on a cell board level, there may not be enough time to complete the task if the pack voltage drops under load. Most BMS's for 'house' power have now dropped their cell balance point to 3.55V or less. Plus... this accommodates alternator or a host of other typical marine/rv chargers.


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[OrioN]

They should arrive this afternoon - I should have them in the RV this evening. And if they're really shipped at 50% SOC or thereabouts, I just realized that I don't have a good way to charge them - unless I use my regular standard/AGM car charger. I assume the present Parallax 7355 won't do much. It also sounds like the Sprinter alternator output will be enough to charge them on this weekend's first trip - it'll be VT to PA on Friday/Saturday, then back Sunday afternoon.

Do you happen to know anything about battery monitoring for these batteries? I haven't even started to think about that issue yet.

CHARGING:

My current and principle method of charging is via solar. My Morningstar MPPT60 is custom programmed to charge at 14.1V Absorption, and stay at 14.1 for 2 hrs to full-fill the cell balancing. It then switches to a 13.5V Float, so I can keep the bank at MY 100% SOC and run me loads rest of day.

My 'bank' arrived at ~40% SOC. I used the solar charger too for the initial charge. With 600W PV and running ~8A loads while charging, it took 2.25 day to top up the needed ~250aH. I monitored the the SOC and cell states for the duration. When the bank was nearing full SOC during day 3 of charge, the 4 super cells were indeed out of balance and with a cell volt differential of 0.25V between high and low. It took 2 more days to finish the balancing, and I had my charger set to a 6hr 14.1V absorption. I've kept this algorithm for future needs....



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[Custommm]

Just to add a bit of noise on this very interesting thread...

I asked the Following to Randy at BestConverter.com
Hi
I currently own a 2014 Class B+ motorhome
1-Having 2 interstate flooded Golf Cart battery (6V)
2-a GoPower 95 W Solar panel and the GP-PWM-30 Solar controller
3-Magnum MM612 inverter (600W)
4-Converter-WF8955-PEC
5-Diesel Generator 3200Watts

I would like to know what would be required to add Lithium batteries to my RV.. (i heard that Li with Mg is even safer/better than the LiFePO4)

Looking to be able to use more Fully the AH (150-200) and have a Pure SineWave inverter (approx 1800-2000w PureSine ,like a house outlet)


I know that Lithium can be harmed and NOT last as long as expected if the Temperature is not well managed and if the charging controller is dumb (make sure the proper charged is applied to each cell individually)

1-So What do you see as requirement for my project and what would be the approximate cost to add this new/mostly R&D, feature to my RV…
2-Is major re-wiring have to be replace (Versus Bulk FAST recharge of those Li battery)


Randy's answer:

Hi Dany,
If you get lithium, the only thing I know that you will need to change is the converter. Here is a link to our lithium converter/chargers.
http://www.bestconverter.com/Lithium-Ion-Battery-Chargers_c_221.html

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Is it a bit too easy ??
What do you guys think?

 

[Peter Tourin]

I got my batteries from SmartBattery - they're 100AH drop-ins with internal BMS. Those PD 9100L series chargers are what SmartBattery recommended to me. They've tested them with their batteries, so they don't have any concerns about compatibility. Note that those chargers come with a power cord, and you void the warranty if you modify the charger - also the form factor is pretty different than the OEM converter (in my power center at any rate). So there will be some mechanical/electrical issues with removing the OEM converter and mounting and wiring the PD.

If you have a 55 amp charger like I do, note that the PD 60- and 70-amp chargers are the same size, while the 80-amp charger is bigger and requires a 20A breaker instead of 15A (which is what's in my power center for the OEM converter). I'm trying to decide if it's worth all the rewiring and mechanical issues to install the 80A charger - I installed 2 100AH batteries, and they'll be perfectly happy with the 80A charger. But I'm not sure it's worth all the work just to gain a slightly quicker recharge time. This is a crude and not quite correct comparison, but if the difference between their 60A and 80A chargers were 3.3 vs 2.5 hours to fully recharge, do you want to go to the extra effort in order to charge in 2.5 hours?

BTW - the SB100 batteries are a drop-in for the MB's battery compartment, but only barely - it's a VERY tight fit. and I had to slightly rearrange the wires where they enter the compartment. Photos later.

Also - the PD website has a page in their lithium charger area with an interesting description of how the charger and the battery's BMS interact - http://www.progressivedyn.com/pdfs/lithium_battey_chargers_lit.pdf

 

[smiller]

Assuming quality design and construction a fixed-voltage DC supply is a fixed-voltage DC supply. All of the intelligence is in the BMS and from all I can tell the only thing 'Lithium' about the Progressive Dynamics unit is setting it to a fixed 14.6 volts and applying a purple label.

Long way of saying, if another power supply manufacturer of equal or higher quality has a unit that meets your needs better (in terms of size, power output, etc.) then I wouldn't hesitate to use it.