Simplified lifepo4 charging and care
Collapse
This is a sticky topic.
X
X
-
I might add that it might be a good idea to put those two batteries in parallel for a day or two. It would be best to put 14.4 volts on them so they get current and have a better chance of balance at the top of the charge curve. That would eliminate any big balance issues that might have complicated the original scenerio. They won't balance in series because as soon as one of them hits the high voltage cutoff the BMS should drop it off and the other one will also lose power so it would never catch up. They could also appear to be in balance at resting voltage but that is not a good measure like it would be at the upper knee at 14.4 volts. -
Hi Ampster
The Batteries are VoltaX 200 Ah LiFePO4. They do say up to 4 batteries in series. I agree it's a warranty problem and like all warranty situations I want as much information and understanding of the problem. Sadly many manufacturers try to negate claims, so opening the battery is not a viable option.
The same battery functioned well as single 12volt system. So the problem only came about with the addional battery.
I would verify all your charger settings to better inform your conversation with the manufacturer. Normally those drop in batteries should open the circuit if either battery goes above the charging voltage. The reason for using a power supply versus your charge controller is to get a more consistent current measurement for the documentation, It may also eliminate your charge controller as a variable.Last edited by Ampster; 11-30-2020, 12:57 AM.Leave a comment:
-
Hi Ampster
The Batteries are VoltaX 200 Ah LiFePO4. They do say up to 4 batteries in series. I agree it's a warranty problem and like all warranty situations I want as much information and understanding of the problem. Sadly many manufacturers try to negate claims, so opening the battery is not a viable option.
The same battery functioned well as single 12volt system. So the problem only came about with the addional battery.Leave a comment:
-
......... Recently I purchased another identical (Make and Watts) battery.
Fitting them in series I set charging volts to 29.2 (14.6 recommended charge per battery) . The new battery does not want to charge up to the same voltage as the original one. In circuit I am getting a maximum 13.32 volts on the new battery and 15.69 on the original. The combined voltage comes up as 29.01 Volts, seemingly ideal, but 15.69 is too high for one and 13.32 is too low for the other. Should the BMS have allowed this?
I assume one of the batteries is faulty but which? As I’m new to lithium I’m betting on the new one, but...? The original battery is only one month old. Now I wonder if the 15.69 has damaged the battery.I would appreciate any help with this problem.
....
This sounds like a warranty issue that you should discuss with the manufacturer.Leave a comment:
-
I have an off grid system consisting of 900w solar array through an “Outback 80Amp controller”. I was using only 1 LiFePO4 200w battery set for 12 Volts. Recently I purchased another identical (Make and Watts) battery.
Fitting them in series I set charging volts to 29.2 (14.6 recommended charge per battery) . The new battery does not want to charge up to the same voltage as the original one. In circuit I am getting a maximum 13.32 volts on the new battery and 15.69 on the original. The combined voltage comes up as 29.01 Volts, seemingly ideal, but 15.69 is too high for one and 13.32 is too low for the other. Should the BMS have allowed this?
I assume one of the batteries is faulty but which? As I’m new to lithium I’m betting on the new one, but...? The original battery is only one month old. Now I wonder if the 15.69 has damaged the battery.I would appreciate any help with this problem.
MaurieLeave a comment:
-
If we lived there full time I would probably skip the BMS. But $700 is worth it for the piece of mind when the place is vacant.
Thanks for all the advice.
Leave a comment:
-
I would however follow EVE's recommendation for clamping the cells to extend their life. It does not need to be much but it reduces strain on the terminals if there is some swelling. I have 32 of these cells in a cabinet with 3/16" aluminum plate and 1/4" allthread. The clamping force I used is enough to compress a split washer. Not much is necessary.
Leave a comment:
-
Yes, that Granger heater pad is the sort of thing. Look for one with some sort of CE or UL certification, you want reliable & safe, not cheap. Seed bed heaters would also work I suppose,
Think of unattended conditions, the cost of the batteries, and the consequences of a failure. Will your charge controller block charging if the temps fall below 34F ?
Be sure to inhibit charging by disconnecting the solar panels from the controller, - don't allow the BMS to disconnect the battery from your controller, or you may fry the controller.Leave a comment:
-
Hey PNJunction. .....
With all your LifeP04 experience over these last six years do you still think running without a BMS is practical for a setup like mine? I may eventually add the Orion Jr.2 BMS but want to get familiar with LifePO4 before getting too complicated.
.....
I tried variations of charge current and Constant Voltage settings and the simplest solution was just to lower the voltage setting on the built in charger because I wanted to increase my odds of fully charging my pack from solar. That is why I kept the current high but it was still way below 1C.
That is why I would recommend that you use very conservative charging voltages until you do get a BMS, I had the advantage of several weeks of small increments while I could monitor my pack daily before I felt comfortable leaving it on its own. I did settle on 3.40 volts per cell which is a CV voltage of 54.4 volts for the pack. That is a conservative number but these cells seem to have a pretty steep charge curve after 3.4 volts. You are not leaving much capacity on the table and your pack life will be extended with that conservative voltage.
I have always used a BMS but I have not always used the the individual cell voltage cutoff to protect my pack. I have relied on using conservative charge parameters. Over time the small balancing currents of the BMS tend keep the cells balanced at the top but keep in mind, with these 250 Ahr cells it is going to take months to bleed off even a 10 Ahr balance difference between these large cells.Last edited by Ampster; 11-24-2020, 10:43 PM.Leave a comment:
-
An alternative would be a seedling heat mat. Inexpensive ones that maintain about 70F are $20 and ones like this with adjustable thermostats are more: https://www.amazon.com/dp/B016MKY7C8..._1DBVFbZJTPAT9
Not sure that you would need an aluminum plate with the surface area of these pads. EVE says in their spec sheet that these batteries will perform from 0C to 60C which is 32F to 140F although I would never take them to those extremes. The charge and discharge tests are done at 25 C which is 77 F.
I would however follow EVE's recommendation for clamping the cells to extend their life. It does not need to be much but it reduces strain on the terminals if there is some swelling. I have 32 of these cells in a cabinet with 3/16" aluminum plate and 1/4" allthread. The clamping force I used is enough to compress a split washer. Not much is necessary.Last edited by Ampster; 11-24-2020, 11:40 PM.Leave a comment:
-
I think 70F is too warm. 45 F is good enough, or even 50F if you want them more "lively"
I think an incandescent bulb is too unreliable (even 2 of them) I'd suggest a 50w heater pad or something like that, on an aluminum heat spreader plate at the bottom of the battery box (don't put the weight of the batteries on the heat pad)
google "silicone battery heater" for a bunch of ideas, Put a plate (thick enough to conduct heat) inder the batteries and extending enough on the side to stick the heater to. Much better than a light which will heat one battery and the otheres will be cool
https://www.grainger.com/product/3CD...P7A1P:20501231Last edited by hammick; 11-24-2020, 09:40 PM.Leave a comment:
-
..... Batteries will be in an insulated box with a remote operated incandescent bulb so I can keep them close to 70 degrees Fahrenheit during the winter. There will be a second bulb for backup purposes. Both bulbs will be controlled using a simple but reliable Wifi plug through the Smartlife IOS app........
I think an incandescent bulb is too unreliable (even 2 of them) I'd suggest a 50w heater pad or something like that, on an aluminum heat spreader plate at the bottom of the battery box (don't put the weight of the batteries on the heat pad)
google "silicone battery heater" for a bunch of ideas, Put a plate (thick enough to conduct heat) inder the batteries and extending enough on the side to stick the heater to. Much better than a light which will heat one battery and the otheres will be cool
Leave a comment:
-
Hey PNJunction. I read this entire thread. I will be installing an EVE 16s 280ah 48v bank to replace my 325ah Trojan L16s. I will be top balancing them in parallel with my CC/CV adjustable power supply. My Schneider Conext XW5548 inverter has settable LVD and HVD. The most I will be taking from these batteries during the darkest of winter is 150ah and a fraction of that when the place is vacant. I have the ability to remote monitor my Schneider equipment and have the Conext shunt based battery monitor for AH counting. I can also remote start my genset for charging if the panels get covered with snow.
When the place is vacant I leave the inverter on to run the fridge, security cameras and a few other low power devices. Batteries will be in an insulated box with a remote operated incandescent bulb so I can keep them close to 70 degrees Fahrenheit during the winter. There will be a second bulb for backup purposes. Both bulbs will be controlled using a simple but reliable Wifi plug through the Smartlife IOS app.
With all your LifeP04 experience over these last six years do you still think running without a BMS is practical for a setup like mine? I may eventually add the Orion Jr.2 BMS but want to get familiar with LifePO4 before getting too complicated.
Thanks for any advice.Last edited by hammick; 11-24-2020, 07:08 PM.Leave a comment:
-
Yes the voltages will be equal when all are in parallel but at 3.65 at no more than .0015C. It would be better done at 3.4V but now the rough equalization has been done there is no reason to go back to this step. Since his balancers can charge and discharge cells, equalization can be done at the absorb voltage while in normal use.Leave a comment:
-
I think the OP is talking about the whole pack in parallel to get the cells closely balanced near the top. In that configuration they will self balance the voltage themselves. Earlier I think he said high voltage cutoff would be about 3.4 per cell in normal use when using the balancing devices.
Last edited by robeyw; 02-06-2020, 09:41 AM.Leave a comment:
Leave a comment: