Lithium Vs. More Solar

[obiwancanoli]

Having learned so much from members here since my initial posts in early 2018, I've been grateful that the learning curve has been relatively steady, and informative. I've truly appreciated the guidance...

Today, considering replacing my standard deep cells - each 115 min @75 amps, 220 Ah at 20 hr - with 100 Ah Lithium batteries is on my mind. I'm thinking 3 would do the trick, but have room for 4...

My rig is a 2017 Newmar Ventana LE 3436. I've got 480 W Zamp solar producing 26.1 peak Amps, a 30A Controller, plus a external, portable solar panel at 120 W.

The Li choice seems clear to me, as a distinct cost advantage over time, and fits well with my goal to enjoy more dry camping...

The question is, should I consider adding another 160-320 W solar? Of course, would need to obtain new controller, thinking MPPT would be best - note that I ask because of my tendency to plan for worst case scenarios, and feel a certain peace of mind knowing I'd have sufficient power to last a week without sunshine... shade is nice, but that doesn't help the solar much...

[obiwancanoli]

pianotuna wrote:
obiwancanoli,

340 watts of panels is probably quite a bit on the low side. I'd aim at 600 to 800 watts.

Several of the members here have 600 + and find they don't need to run a generator at all.

Thanks, That's my goal... no gen

I already have 480W on the roof, and am considering adding another 340, depending on, first, the results of installing the Victron 712. Readings should offer some insight as to how much solar, if any, to add, but I'm inclined to add it anyway, and have room to double that.

[3_tons]

Ha, Nuttin to fear except for fear itself - lol!!...

The thing that’ll keep your LiFePo4’s happy is that once they’re fully charged to not let them linger on the charger for an extended period of time, and when not in use (e.g. in storage) store the batts at about 50% SOC (an approx equilibrium of about half the ions on the anode and half on the cathode thingy),

To avoid parasitical losses (when in storage) I added a disconnect switch directly atop the positive battery post (or pos cable per Victron)...I first checked switch with an ohm meter and it measured zero resistance when in operation...

https://www.ebay.com/itm/Battery-Disconnect-Switch-Quick-Cut-off-Terminal-Link-for-Car-Truck-Auto-Vehicle/363023438228?hash=item5485e21194:g:IIAAAOSw3RtbQbsZ

3 tons

[pianotuna]

obiwancanoli,

340 watts of panels is probably quite a bit on the low side. I'd aim at 600 to 800 watts.

Several of the members here have 600 + and find they don't need to run a generator at all.

[obiwancanoli]

Feeling better about this... looks like I probably don't have to worry about a new converter, charger, inverter... Once the Victron 712 is installed, that should give me a bit more info on which to move forward, if at all... By the way, also of note, I also have a 2000W Modified Sine Inverter

Thanks, everyone... this has been a real education... I hope some of it sticks

[3_tons]

BFL13 wrote:
So you can get a PowerMax LK (or the Boondocker rebrand) for a lot less than a PD, and it can be set to any voltage you like (from 13 - 16.5) by you--not by the factory-- and you can use the Victron gismo to limit the time the same way.

Good point, and the adjustability should make it suitable for a wide array of LiFePo4 offerings...

3 tons

[BFL13]

So you can get a PowerMax LK (or the Boondocker rebrand) for a lot less than a PD, and it can be set to any voltage you like (from 13 - 16.5) by you--not by the factory-- and you can use the Victron gismo to limit the time the same way.

[obiwancanoli]

3 tons wrote:
I’m relatively new to Victron's BMV Li compatible SOC meter, but prompted by my previous, I then checked the Victron BMV Manual and found this item of high interest in Section 4.2.2 concerning relay programming - For those who have this device, this seems the ideal solution to end-of-charge shutting down of the Li’s charging source post BMS balancing regiment!!

“15. Relay-off delay
Sets the amount of time the ‘de-energise relay’ condition must be present before the relay opens.
Application example: keep a generator running for a while to better charge the battery (relay in CHRG mode).
Default Range Step size:
0 minutes 0 – 500 minutes 1 minute“

Many thanks, Victron!

3 tons

Really good to know this, sir, thank you. I have one coming and soon to be installed as the first step in the process - LI upgrade, then, perhaps, add 340W solar and an MPPT Controller...

[3_tons]

I’m relatively new to Victron's BMV Li compatible SOC meter, but prompted by my previous, I then checked the Victron BMV Manual and found this item of high interest in Section 4.2.2 concerning relay programming - For those who have this device, this seems the ideal solution to end-of-charge shutting down of the Li’s charging source post BMS balancing regiment!!

“15. Relay-off delay
Sets the amount of time the ‘de-energise relay’ condition must be present before the relay opens.
Application example: keep a generator running for a while to better charge the battery (relay in CHRG mode).
Default Range Step size:
0 minutes 0 – 500 minutes 1 minute“

Many thanks, Victron!

3 tons

[3_tons]

I would add however that 14.6v is the BMS cutoff voltage for some LiFePo4’s...From what I’ve been able to gather it seems that there’s really no such thing as a “one size fits all” Li charger - Custom tailored voltage adjustment makes perfect sense, while ‘user adjustability‘ (per solar controllers) would be even better, and adding say an end of charge tail current & voltage timer ‘ala Victron’s BMV would be BEST!!...In fact, the Victron’s built-in relay could likely be adapted to this end!!

Either way, most LiFePo4’s suggest a charge voltage range of 14.4‘ish -14.6, so it’s fairly easy to find a conventional charger that fits that bill...Some end of charge monitoring MAY be required...

3 tons

[BFL13]

bestconverter's blurb says:

"Output voltage can be FACTORY ADJUSTED to meet OEM requirements for various lithium ion battery chemistries and Voltages. Standard “L” Series voltages are set for 14.6- Volts to meet requirements for lithium iron phosphate batteries. Other chemistries may require different voltages"

So if your Li doesn't like 14.6v, I suppose you have to special order your 9100L.

I have not checked to see if there is a place on the usual on-line ordering "carts" where you fill in what voltage you want yours to be.

[3_tons]

“ Please explain what the 2 individual bms's that are on each separate battery pack protecting the individual cells of that battery pack reacting with each other during possible spikes while discharging or charging. Most likely different brands, programming.“

To borrow a phrase from former Sec of Defense Rumsfeld, it seems to me that it’s more a matter of the “known knowns, the known unknowns, and the unknown unknowns” - lol

3 tons

[3_tons]

“Progressive Dynamics, in partnership with one LI battery maker has come out with a LI=programmed converter. Now. that is the full extent of my knowledge on this unit. I forget which company they partnered with (might be Battle Born). If you are going to go LI. you need this converter”.

During a recent camper conversion, I gained hands on experience with PD’s latest Li converter-charger, and ultimately spoke with PD’s tech about their Li charge methodology...The charger’s output is merely fixed at a constant 14.4v throughout the entire charge cycle and beyond...Once the Li is fully charged, it strictly relies on the BMS for charge management thereafter - their tech said that he would not recommend leaving the charger on for long term storage...

Because of this, I personally prefer my ‘ol faithful PD 9245 with it’s benign end of charge switch to float, I just skip the equalizations...

3 tons

[Itinerant1]

BFL13 wrote:

Itinerant1 wrote:

BFL13 wrote:
"If you're thinking of adding 100ah batteries to larger ah capacity batteries your going to run into problems. Yes, they are the same voltages but the lower capacity batteries will shutdown before the larger capacity batteries. The bms's could be setup differently protecting the cells of the different packs. Stay with the same ah capacity battery"

Please explain. I asked about this earlier in this thread, but no answer.

No problem with FLAs so why with Li is the question. (FLAs do not "shut down" eg.) Is it because of BMS? Is the BMS in the same brand 200 different from the BMS in their 100, so they shut down at different times?

If so, why pick the 100 to shut down first? What does capacity have to do with it, when it has no effect with FLAs?

Just like to know and maybe others do too. Thanks.

If using say a 100ah and a 125ah lfp probably no problem.
But...
Using a 250ah and a 100ah the bms's aren't that smart to know to use the 150ah first from the larger bank. So the individual cell voltages with in the dropin battery will diverge from each other as the capacity get sucked from them. As the 100ah drops in capacity so does the cell voltage, which in turn should shut one battery down early. Or charging which obviously the smaller will fill first, once again triggering a shutdown and if for some reason it didn't shutdown good chance there will be some puffy cells at the very least. 😉

You appear not to understand that they rise and fall together per their SOCs. If there is a 100 and 200, and a 60 amp draw, it will be 20 from the 100 and 40 from the 200. (the 200 has half the R compared with the 100 and V=IR, so I is twice with the 200 to keep V the same)

They will each reach 50% SOC at the same time, and when recharged, they will reach full at the same time. They are at the same voltage in parallel, and each has the same voltage/SOC.

Please explain what the 2 individual bms's that are on each separate battery pack protecting the individual cells of that battery pack reacting with each other during possible spikes while discharging or charging. Most likely different brands, programming.

[wa8yxm]

The Converter/Chargers in RV's come in 3 types for this discussion.
Some (Generally large Inverter/Chargers) are programmable by the user and may be I STRESS MAY BE, adjustable for LI battery types.

Most CONVERTERS are not programmable at least not as designed, and are designed for flooded wet cells.

Progressive Dynamics, in partnership with one LI battery maker has come out with a LI=programmed converter. Now. that is the full extent of my knowledge on this unit. I forget which company they partnered with (might be Battle Born). If you are going to go LI. you need this converter.

I suspect other companies may follow.

[3_tons]

Seems that prudence may well be advised when attempting to apply FLA logic to Li...

3 tons