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paulz
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# Posted: 7 Nov 2020 06:35pm
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Quoting: somewhereinusa I use a Victron BM700 it keeps track of amps used.
Thanks. This is what Victron says about it:
The BM700 is a high precision battery monitor. The essential function of a battery monitor is to calculate ampere hours consumed and the state of charge of a battery. Ampere hours consumed are calculated by integrating the current flowing in or out of the battery.
I take that to mean it keeps track of amps added as well as used. So if you started with 100, used 50 but charged back 25, it will say 25 used, or 75 remaining.
Do I have that right?
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paulz
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# Posted: 8 Nov 2020 12:05pm
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Dug this out of the box of stuff that came with my Epever SCC. Looks like it can do the trick. No instructions, guess I'll put it over the negative battery cable (as ICC advised awhile ago) and start pressing buttons.
https://www.droking.com/Digital-Tester-DC-10-90-V-100A-Multifunction-Voltage-Current- Capacity-Power-Coulometry-Time-Display-Panel-Meter-Monitor-Meter?search=100a&descript ion=true&page=5
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paulz
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# Posted: 25 Dec 2020 02:08pm - Edited by: paulz
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I'm such a dope. I've been charging my Valence U27s with a special Lifepo4 20 amp charger I bought just for them (although I never saw it put any more than 6 amps). It takes about a day and half for two batteries in parallel, and has done the job well. Up until a week ago, when I left it outside charging overnight and it rained. Charger is kaput. And I want to go back to the cabin tomorrow or the next day. I have them on a standard 1 amp regular charger/maintainer right now, and they are 75%.
There is a guy selling an 18 amp charger that is supposed to be LFP friendly but I don't see where it has the special two stage charge rate for LFP. (Its a Dual Pro RS3, nice charger in any case). He's not trying to talk me into it, but he does say that with the internal BMS in the Valence, any regular battery charger will work without damaging the batteries.
I can order another LFP only charger online and get it in about a week, just wondering if indeed it's a benefit to have.
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Steve_S
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# Posted: 26 Dec 2020 02:16am
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LiFePO4 can be charged with either of these modes:
1-stage profile (constant current (CC) aka Bulk Stage) profile will charge the battery ~95%. The 1-stage profile is sufficient, since LiFePO4 batteries do not need to be fully charged, they will settle to 95% after charging.
2-stage profile (constant current, constant voltage (CC-CV) profile aka Bulk and Absorption Stages). The 2-stage profile will charge the battery 100%. This may also have the effect of triggering a BMS HVD (High Voltage Disconnect), therefore take appropriate precautions by using conservative charge settings to begin with.
• Optimal Charging will occur at 0.5C charge rate per battery. The number of batteries multiplies the amps required to meet 0.5C charge rate.
• The ability for any single battery within a bank of batteries should be capable of handling the full charge & discharge potential of the system.
NB: Some BMS' (Battery Management Systems) can interact with Inverters, Chargers & Solar Controllers which can improve overall performance, reliability and longevity of the battery systems. These capabilities are dependent on the equipment being used.
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paulz
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# Posted: 26 Dec 2020 08:07am - Edited by: paulz
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Quoting: Steve_S • Optimal Charging will occur at 0.5C charge rate per battery. The number of batteries multiplies the amps required to meet 0.5C charge rate.
Thanks Steve! I don't know what you mean here. is that a half amp? And by number of batteries, is that cells per battery? I don't know how many are in the Valence U27. A lot I'm sure, it's 140AH and weighs 40lbs. I think. Also believe it is rated for 20A charge capability, so with 2 in parallel I could put 40A at them?
So does that mean I could charge to 95% with a standard automotive battery charger? That's good enough I think, even after 3 days at the cabin they are still around 40% by my AH meter.
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Steve_S
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# Posted: 26 Dec 2020 11:02am
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Example:
A 100AH LFP battery can discharge up to 1C Max, which is 100Amps. Usually, that is kept below 0.5C or 50A.
The Valence batteries are well discussed in the DIY forum, some even have gotten the BMS software to be able to interact with some of the Valence BMS'. There are different models with different specs and interfaces.
I urge you to get the spec sheets for the specific batteries you have (model & version), if you overdrive charging, the BMS will be constantly cycling on/off depending on its setup internally.
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paulz
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# Posted: 26 Dec 2020 04:17pm
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Well I had never heard of a 'C' until I read your post this morning.  I need to read up and understand about that. Thanks.
Data sheet for my batteries. 72 amp charge?
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gcrank1
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# Posted: 26 Dec 2020 05:13pm - Edited by: gcrank1
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C rate is the 'charge' rate; bat AH's divided by the C rate is your charge amps.
For example, with the old lead acid 100ah you would be safe with a C-10 though some AGMs I had said up to a C-6. Mfg spec is the one to follow.
So, for a 100ah bat that is 10amps for a C-10, 16.6 for C-6.
C-1, outrageous! Wow! Magic in, magic out
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ICC
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# Posted: 26 Dec 2020 05:50pm
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Quoting: gcrank1 C-1, outrageous! Wow! Magic in, magic out
charge rates of 0.5C to 1C are relatively commonplace with lithium cells. High charge rates can degrade longevity but I have some 6 year old lithium ion cells that still perform extremely well even though they are regularly recharged at 1C rates.
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Steve_S
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# Posted: 27 Dec 2020 05:21am
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Some LFP Chemistries can handle up to 3C and even 5C discharge rates (these are far from cheap !).
NCM, NCA and other chemistries can handle even higher C-Rate Discharge & Charge. Remember, EV's are 300-600 Volts DC and higher for bigger vehicles like trucks / busses.
The A-Typical ESS / Storage battery used for residential is 1C Rate max.
Headway LiFePO4 can do continuous discharge up to 10C and continuous charge at 3C but $$$$$$
@Paulz, yes per that datasheet that battery can take 72A charge. So from 0%SOC to 100% SOC @ 72A would take 2 hours. +/- a bit with CCCV charging.
BTW: If you watch the videos on the YT about these Valence Batteries, you'll see they are using Cylindrical LFP which is indicated on your posted spec sheet.
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paulz
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# Posted: 27 Dec 2020 09:05am
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Thanks guys. So with my 140ah batteries, a 72 amp charge is a C2 rate?
I have to decide on a charger. My two options as I see them are a LFP specific 20 amp charger like the one I just fried, or a higher amperage non-LFP automotive charger. Both about $150. Here are the examples.
The automotive charger would be nice to have for other uses, and I don't think the second stage charge for the extra 5% is needed for me, if I'm only losing 5% of my usable power. But I want to do the right thing for the batteries.
I do have a benchtop 6-10 amp automotive charger I could try in the mean time, again if they won't hurt anything.
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Steve_S
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# Posted: 27 Dec 2020 02:54pm - Edited by: Steve_S
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With Lithium...
140AH Lithium Battery,
1.0 C-Rate = 140A
0.5 C-Rate = 70A
0.33 C-Rate = 47.6A
Forget the lead usages for this stuff.
There is also no Peukert Effect with Lithium.
The more Amps you can push (14.6V @ 70A max in your case) the faster the battery will charge. This will also cause the battery to warm up during charge.
That first charger - ummm... more like a LED Lighting Power Supply being used as a charger. Not uncommon but not what they are designed for.
Right at this moment as I write, I am using a TekPower 1540E Bench Power Supply to top charge 4 LFP 280AH cells. Because I am "topping" the cells are in parallel getting 3.55V @ 34A. As this is a proper CCCV Powersupply it will reduce amperage relative to increased impedance as the cells fill up.
LINK to the TekPower 1540E
https://www.amazon.com/gp/product/B015QHVJP6/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&p sc=1
OR https://tekpower.us/power-supply/switching-powersupply/tp1540e.html
There are other Good Brands at similar price points.
A PRO TIP if your feeling inclined.
If you have an old Desktop PC with a big ATX Powersupply, you can purchase what is called an ATX-Breakout that basically turns that into a controlled and adjustable powersupply. The kits are CHEAP ! Depending on ATX PS you can get a seriously great powersupply. The kits can be for any size ATX Powersupply but if you want to use anything over 600W make sure the kits supports it. My 1100W Gamer Machine supply fried one instantly....
Two Examples:
https://www.amazon.com/Breakout-Adjustable-Supports-1-8V-10-8V-Protection/dp/B08NC3S7 Q2/ref=sr_1_15?dchild=1&keywords=ATX+Breakout&qid=1609098653&sr=8-15
https://www.amazon.com/Breakout-Adjustable-Supports-1-5V-9-0V-Protection/dp/B07KPF8QW 4/ref=sr_1_6?dchild=1&keywords=ATX+Breakout&qid=1609098653&sr=8-6
BTW: Several Videos on YT about doing just such conversions plus enhancing them too for more functionalty/capability.
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paulz
Member
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# Posted: 27 Dec 2020 06:05pm - Edited by: paulz
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OK so I should be looking at power supplies instead of battery chargers.. Might as well go for 40 amps, an old desktop PC power supply won't do that will it? The breakouts you showed are only a couple of amps. Darn, and I just took an old PC to the electronics recycle. They have a ton of stuff, maybe I'll go see if they have anything.
On another note: I have two Valence U27s in parallel in my truck, that plug into and power the cabin most of the time. I have a third U27 in the cabin hooked to my newly installed solar. If I go somewhere in the truck, I plug this battery in while I'm gone.
The two batteries in the truck have the same SOC obviously, the third has something else depending on how the solar is doing. Would it be a bad idea to have all three connected and powering the cabin at the same time? Don't really need to, just wondering.
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paulz
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# Posted: 30 Dec 2020 10:56am
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Hey where'd everybody go?
Those TekPower power supplies are nice, might be the ticket. But then I have to figure out how to do the 2 stage charging, right?
Last night, after the sun went down and my solar charging experiment went from 2amps to zero, I went to grid charging. I tested both my 10 amp car battery chargers on an FLA battery, both showed a charge of 15v and change, afraid to use them. Then I dug out a little gel battery charger, it only tested at 13.8. I opened it up, found the the little potentiometer dingus and cranked it up to 14.6. It's been on all night. Only putting in 2 amps but I'm at 75% SOC so should be able to make the cabin trip tomorrow. Plus my third Valence is on the solar at the cabin at somewhere around 1-2 amps.
Still need to figure out a charger or power supply. I was looking on Craigslist, as I'm know to do, and see they make LFP chargers/power supplies for RVs.
https://www.progressivedyn.com/rv/power-converters/pd9100-series-rv-power-converters/ pd9145a-45-amp-electronic-power-converter/
Same price as the TekPower, but maybe does the LFP charging on it's own? Maybe even some other stuff. But maybe it takes another piece (interface) to work?
All very involved. I just want to get back to cutting logs and stuff. Probably should have just paid for grid power years ago but too far along now..
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ICC
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# Posted: 30 Dec 2020 01:17pm
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Quoting: paulz Those TekPower power supplies are nice, might be the ticket. But then I have to figure out how to do the 2 stage charging, right?
Power supply units like those serve many purposes. When assembling lithium cells into battery packs they are invaluable for bring all the cells, wired in parallel, to the same exact voltage as Steve was doing. There are very definite reasons for doing that. A whole topic unto itself.
In the hands of the wrong person, with the power supply set incorrectly, whatever, one could seriously damage lithium cells.
There are many other uses for a CC/CV power supply for those who like to work with various electronics. I do not recommend power supplies such as these for general purpose battery charging. They are a professional or serious hobbyist tool. I have two. I would be lost without them. However, I do all my regular battery charging with assorted battery chargers that have all the needed automatic taper down and charge profile switching and/or automatic shut-off capabilities.
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ICC
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# Posted: 30 Dec 2020 01:39pm - Edited by: ICC
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The PD units are good for their intended use; RV's. They are like having two units in one. When connected to grid or generator power they can directly supply enough DC current to run all the DC devices there may be. Up to the rated output power, 45 amps in this case. The PD can do that even if not connected to any batteries.
They also have a battery charger built-in with all the stages you need. BUT it is news to me that their chargers have the required profiles for charging lithium cell batteries. PD never used to have lithium settings in their equipment. BUT I have not kept track of what they may offer today. I would want to verify their lithium ability by seeing it listed in manufacturers information, not on a forum, blog or sales ad from anyone else.
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paulz
Member
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# Posted: 30 Dec 2020 02:15pm
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Thanks ICC. Yeah the ad on Craiglist says the PD is for lithium but the specs say 13.8 volts and no mention. I have noticed several chargers ads that say lithium but digging deeper appear not.
https://sfbay.craigslist.org/eby/for/d/hayward-camper-van-conversion-parts/7253610180 .html
I'd better stay away from the power supply idea, for the reason you stated...
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Steve_S
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# Posted: 30 Dec 2020 03:09pm
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The TekPower and similar units do CC/CV. I dial it down to do Single Battery Cells but it can do a 12V battery assembly as well, and the obvious other uses. It comes in more handy than I thought it would originally.
For example, I am doing a Topping & Capacity Test runs on individual 3.2V/280AH LFP cells this week. Using the TekPower 15/40. Charging the cells to 3.60V, starting with 40A-cc, which slowly decreases as the cell fills, by 29A it flips to CV mode and continues charging till 1.5A which is 100%.
Once this test run is completed the cells will be individually topped to 3.60V then assembled in parallel and again with charge applied to fully top balance. After that, reconfigure to 12V/4S battery pack and drop into casing, ready to go into service.
The end result will be a 12V/280A/3584Wh battery pack.
Cells: EVE-280AH Prismatic LFP(Dec.30 price)
Total US $646.00 delivered duty/taxes paid to US
https://www.alibaba.com/product-detail/3-2V-280Ah-Lithium-Ion-Battery_62585177205.htm l?
BMS: JBD SPo4S020 4S 12v 120A smart with UART RS485 & BlueTooth
Total US $80.00+/- direct
https://www.alibaba.com/product-detail/JBD-bluetooth-smart-bms-4S-12v_1600079534177.h tml?
OR
https://overkillsolar.com/product/bms-120a-4s-lifepo4/
On a Charger, there are options and using an Inverter/Charger can really simplify a lot. If using an external charger, you can use a dedicated Battery Charger but it is limited to that function. Using a Bench Power Supply allows for t to be used for different things. Fortunately LFP is SIMPLE and does not need super fancy profiles and special trickery.
Just some more muck to ponder & consider.
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Steve_S
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# Posted: 30 Dec 2020 03:37pm
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Ohh, it occurred to me to add this tidbit of "trivial" info for anyone using a Genset for running a charger or inverter/charger.
I use a Samlex EVO 4024 Inverter/Charger. It can push 100A Charge, default is 40A, I have mine set for 75A.
At 75A Charge rate it is pulling 120V/23A +/-2A from the Genset. Do note, that Samlex is 94% efficient so pending on charge device, the amps drawn may be higher due to inneficiencies.
25Ax120V=3000W continuous will exceed most small generator handling capacity for "continuous use". Just another factor in the equation.
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paulz
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# Posted: 30 Dec 2020 09:11pm
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Quoting: ICC BUT it is news to me that their chargers have the required profiles for charging lithium cell batteries. PD never used to have lithium settings in their equipment. BUT I have not kept track of what they may offer today. I would want to verify their lithium ability by seeing it listed in manufacturers information, not on a forum, blog or sales ad from anyone else.
Still poking around on the PD units. Oddly the PD website does not mention the lithium units, with the L suffix, but they are for sale all over the place advertised as lithium only. Tempting, but from what I gather they go into float mode after charging, and also they have no indicator light to let you know when it's charged.
http://www.bestconverter.com/PD9145AL-45-Amp-12-volt-Lithium-ConverterCharger_p_604.h tml#.X-0zMHdKja8
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paulz
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# Posted: 30 Dec 2020 10:09pm
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Hey, look at this, would they work?
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Steve_S
Member
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# Posted: 31 Dec 2020 05:36am
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Quite a few folks use the MeanWell power supplies and there are kits for these as well, which allow for fine adujtments but I have no familiarity with them.
This is a discontinued model.
Manual Here:
https://www.mouser.com/datasheet/2/260/scn-600-spec-1180098.pdf
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paulz
Member
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# Posted: 31 Dec 2020 06:44am - Edited by: paulz
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Thanks Steve. I am going to get a couple from this guy this morning. I'm not finding the kits you mention, where can I search? They do have a voltage adjustment screw already.
For $20 each I can keep one at the cabin for genset use and one in the city.
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Steve_S
Member
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# Posted: 31 Dec 2020 07:12am
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From what I saw a few companies like RDI ?
This is one example below. People take the Meanwell type supplies & use this type of "front end" to get more tweakable / adjustable power supply. There are different brands & versions with various capabilities. I've seen them on eBay & amazon as well. Unfortunately, I have not paid much attention to these as it's not something I use.
I have a variety of chargers & power supplies so, these have not come into play for me...
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paulz
Member
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# Posted: 31 Dec 2020 09:05am
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Quoting: Steve_S This is one example below.
Thanks, did you mean to include an example? I'm still foggy on this. I take it this is to do the two stage charging? I can't just adjust the Mean Well (what a name..) to 14.6 and have at it, at least for the first charging stage? Does the kit have to be specifically for the Mean Well? What are the specs I need to look for in the kit? Think the Dodgers will the World Series again next year?
Thanks Steve. Leaving in two hours to get these, 60 mile trip.
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Steve_S
Member
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# Posted: 31 Dec 2020 10:26am
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IF you can set the voltage 14.0 to 14.6 V and "Verify" it with a DMM/DVOM to be 100% certain it right, it should feed Constant Voltage & Current till impedence forces amps taken down. This has NO SAFETIES so you will have to watch & pay attention to prevent overcharge conditions OR if the battery BMS starts kicking off because one or more cells are reaching full.
I have two S600-12 which are 12V/50A bridged together for 24V/50A. These were provided by one of my LFP Battery suppliers. They work OK for that setup.
The Example: https://www.aliexpress.com/item/1005001488070904.html
Thi sis use with a MeanWell type PS. The version here is only up to 18W
There are similar products from other companies that can handle even more juice. The above company has a wide variety as well...
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paulz
Member
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# Posted: 31 Dec 2020 02:26pm - Edited by: paulz
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Buy in bulk, that's my motto! I bought all 5 Mean Wells for 75 clams, plus 3 24v 2a for another 5. As my batteries can take 70a, and I have two in parallel, maybe I can double up on them for faster charging? I can use a couple at the cabin via generator and two in the city. And a spare.
I'm off to the cabin for New Years. You're on break Steve. My batteries are at an indicated 95% via my hack charger, should be back around 50% when I get back to try out the new gear.
Thanks again and Happy New Year!
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paulz
Member
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# Posted: 1 Jan 2021 11:53am
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Still attempting to understand charging profiles and such. Got to the cabin yesterday, my one LFP battery hooked to solar was reading 13.4 on the CC. No load connected. That, I think, is 100% SOC.
And now I read Li batteries should not be stored at 100%. So it's bad to have your solar fully charging your Li batteries, whether under load or not? How long is 'stored', a week, over winter? Or if under constant use, are they at 100% if the solar is doing it's job?
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FishHog
Member
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# Posted: 1 Jan 2021 01:56pm
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In my books storage is over winter. Using them every weekend I wouldn’t give it a second thought
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paulz
Member
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# Posted: 2 Jan 2021 08:16am - Edited by: paulz
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Thanks Fish. Well this is a pisser..with the tighter voltage range for SOC on Li batteries, I figured I'd better double check what my meters are saying. First photo is back at the city. My usual go to Craftsman DVM compared to the fancy usage gauge attached to the batteries. 13.2 vs. 13.32. Crap.
Second photo is at the cabin, the controller, the fancy gauge attached to that battery and a couple of cheapo DVMs. From top to bottom 13.20, 13.3, 13.2, 13.43.
Double crap. Hard enough trying to get this stuff right without this. I need a known accurate voltage to measure against.
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