No, so long as you make sure you disconnect all loads, including battery monitor. Lithium do not self discharge as much as lead acid, so will be fine for a year or so.

-- Edited by Mamil on Sunday 26th of May 2019 01:14:20 AM

General advice is to store LiFePo4 at about half normal SOC. The chemistry is different to that of Lead/Acid batteries and the ideas around that technology do not apply to Lithium. Lithium holds it state of charge well and Lithium does not have Sulphation issues we see in Lead/Acid batteries. Working out what semi-discharged SOC is will be your next problem because the Voltage over discharge curve is quite flat. That flat discharge graph is one of the outstanding advantages of having Lithium batteries.

Iza

Branchie wrote:

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Thanks Mamil  when you say I will be fine for a year or so, are you telling me then that I may have to change them out..?  at $3400, I hope not...

 

Branchie

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I meant they are fine to be stored for a year or so without charging. They won't self discharge and die like a lead acid would over that time period. In fact, it's bad for Lithium to be trickle charged over a long time in storage.

But be careful that ALL loads are disconnected, including parasitic loads like battery monitors, voltmeters etc. Best to have a battery disconnect switch, or remove the leads from the terminals, to be sure.

 

-- Edited by Mamil on Sunday 26th of May 2019 01:33:26 PM

Thanks Mamil Now I understand it...  And a good bit of advice you gave also, Get a Battery Dis-Connect Switch... I know the builder is fitting the Redarc Battery Management system, so maybe there is one already there.. but will ask him..

 

Branchie

Using a multi meter, if you can get to the individual cells, discharge until they are between 3.2v and 3.3v, then disconnect the battery and it will remain in a healthy state for yrs until you need it again. Simply reconnect the battery and it will recharge and if the BMS is any good, it should reset the 100% SOC after the first full charge and every thing will work just like it did before you disconnected it.
What battery capacity did you get for the $3400?

T1 Terry

Izabarack wrote:

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Mamil wrote:

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On the other hand, if you do connect it to a charging source such as solar or AC while the van is in storage, then no need to worry. The BMS will let the battery run down to 90% (takes about two weeks) and then will charge it back up to 100% and switch off the charger, let it run down to 90% again and repeat, and repeat. This is not the same as constantly trickle charging and so doesn't damage the Lithium battery.

 

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 Maybe not the same as being on trickle charge, but not different to putting the batteries into storage at full charge. 

Iza

---

 As Iza has said, it is not the same as leaving the battery in storage mode, and depending on the sensing the BMS has, it could very likely not stop the short charging cycle damaging the battery.

I'll try to explain why:

Sadly very few BMS systems actually monitor the cell voltages and base their warning systems from there, so it is very likely a repeated charging from 90% SOC to 100% SOC will be based on total battery voltage and not individual cell voltages. A lithium ferrous cell will be damaged if repeated pushed above 3.6v, (there are 4 cells in a 12v battery). If the cell voltage isn't monitored, the combination of 4 cell voltages can total what ever the BMS considers to be 100% charged voltage yet have one of the cells at higher than the safe max of 3.6v. Each short cycle will push this cell even further out of balance as this happens at the very end of the charging cycle. The run away cell is being pushed ever higher with a charging rate much higher than can be contained by the internal cell balancing system (generally limited to 0.5 amps max) cell damage is the end result.

 

T1 Terry

Tried to put commas in the right place to make it readable, probably still looks like a dogs breakfast but hopefully it's a bit better

-- Edited by T1 Terry on Monday 27th of May 2019 05:42:56 PM

More great info Mamil as for the Redvision system .. I am not sure.. yes it is a new van (or will be once we collect in July)  So will have to ask about that system..

 

Branchie

Branchie wrote:

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 .. I am not sure.. So will have to ask about that system..

---

 Does Redarc provide any written assurance that the semi-controlled cycling of a battery bank in storage will not induce the possibility of battery damage by keeping the battery at full, or near full, charge?   Any written assurance should contain something about the time frame that the Storage setting will cover.

A pretty safe variation to the advice above would be to discharge the battery to, say 12.8 (3.2 x 4), then disconnect the battery completely.   As also said above, re-connection after storage and letting the BMS do its thing, will restore the system to an expected condition.

Iza 

Mamil wrote:

---

T1 Terry wrote:

---

Izabarack wrote:

---

Mamil wrote:

---

On the other hand, if you do connect it to a charging source such as solar or AC while the van is in storage, then no need to worry. The BMS will let the battery run down to 90% (takes about two weeks) and then will charge it back up to 100% and switch off the charger, let it run down to 90% again and repeat, and repeat. This is not the same as constantly trickle charging and so doesn't damage the Lithium battery.

 

---

 Maybe not the same as being on trickle charge, but not different to putting the batteries into storage at full charge. 

Iza

---

 As Iza has said, it is not the same as leaving the battery in storage mode, and depending on the sensing the BMS has, it could very likely not stop the short charging cycle damaging the battery.

I'll try to explain why:

Sadly very few BMS systems actually monitor the cell voltages and base their warning systems from there, so it is very likely a repeated charging from 90% SOC to 100% SOC will be based on total battery voltage and not individual cell voltages. A lithium ferrous cell will be damaged if repeated pushed above 3.6v, (there are 4 cells in a 12v battery). If the cell voltage isn't monitored, the combination of 4 cell voltages can total what ever the BMS considers to be 100% charged voltage yet have one of the cells at higher than the safe max of 3.6v. Each short cycle will push this cell even further out of balance as this happens at the very end of the charging cycle. The run away cell is being pushed ever higher with a charging rate much higher than can be contained by the internal cell balancing system (generally limited to 0.5 amps max) cell damage is the end result.

 

T1 Terry

Tried to put commas in the right place to make it readable, probably still looks like a dogs breakfast but hopefully it's a bit better

-- Edited by T1 Terry on Monday 27th of May 2019 05:42:56 PM

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Interesting Terry, but there's a couple of things in your explanation I don't understand...

As the whole point of the internal cell balancing system is to balance out the cells at the top of the charge cycle, by burning off current from the fully charged cells and letting the less charged cells catch up, why would it be operating in the opposite way to push the cells with the highest charge even higher?

Secondly, as cell balancing only happens at the end of the charge cycle, what difference does it make whether the battery was "short cycled" or deep cycled?

---

The charge burn off type balancers don't generally start until the cell is well and truly over voltage, but then they only burn off 0.5 amp at the very best. I have a few of these balance boards that burn off 2 amps and the heat generated is substantial requiring them to be mounted to an actual heat sink to stop them from failing due to heat stress. When they fail they no longer turn off, they continue to load that cell causing their own set of problems. The heat pumped into the cell while it already heat stressed due to over voltage charging is yet another issue and inside a sealed battery case ....... how does it cool?

The more common and better quality balancers these days use a inductor coil on each cell and switch from single cell to parallel mode linking all the inductors together, then back to single cell mode. This effectively moves current from a high voltage cell to a lower voltage cell, therefore, actually transferring some of the capacity from one cell to the other. These type balancer circuits work all the time. 

If your lithium battery still uses the burn off type balancers, be prepared for a short cycle life. The heat from the burn off balance board will destroy the run away cell by gradually reducing its capacity, this is how the high cell ends up going even higher voltage. The BMS is not linked to the charger so it doesn't know to reduce the charge rate to less than the discharge capability of the balance board.

This loss of capacity guarantees it will be the first to reach the top of charge and go over voltage and also being the first cell to discharge to a point where the low voltage again creates internal heat in the damaged cell. The death spiral is rapid and in a sealed top battery there is no way of knowing it is happening and no way to stop it.

Something to think about, if the BMS was linked to the charge controller and able to drop the charge rate to less than 0.5 amps, how long would it take to finish charging a cell that say only 3 Ah behind the top cell? Now think of how long it takes to get the cells to the point the run away cell goes high voltage, how many hrs does the sun shine? Unless you are recharging from mains power there simply isn't the time frame available to do a proper top balance on a house battery pack due to the capacity of each cell. These systems were designed for the early electric vehicles that had 40Ah cells, not 100Ah or higher capacity cells. It is not unusual to be fitting 400Ah battery packs these days, a 2% difference between the highest capacity and the lowest capacity is an 8 Ah capacity difference, 16 hrs to fix that with a 0.5 amp burn off type discharge balancer, that is a long time to be subjecting a cell to that sort of heat punishment, you have to expect there will be some sort effect on that cell.

 

T1 Terry 

Izabarack wrote:

---

Branchie wrote:

---

 .. I am not sure.. So will have to ask about that system..

---

 Does Redarc provide any written assurance that the semi-controlled cycling of a battery bank in storage will not induce the possibility of battery damage by keeping the battery at full, or near full, charge?   Any written assurance should contain something about the time frame that the Storage setting will cover.

A pretty safe variation to the advice above would be to discharge the battery to, say 12.8 (3.2 x 4), then disconnect the battery completely.   As also said above, re-connection after storage and letting the BMS do its thing, will restore the system to an expected condition.

Iza 

---

Iza, I had the same concern, ie. that the storage profile might damage the battery by keeping it between 90-100% charged for a long period in storage. I queried it with Redarc technical support, and though not in writing, they told me that was the way their engineers had designed it and it wouldn't damage the battery. Not totally convinced by their answer I personally do exactly as you suggest, I discharge the battery to about 50% then disconnect for storage. However, what I said to Branchie is what Redarc advise, so at least he now has the choice of who's advice he wishes to follow!

T1 Terry wrote:

---

Mamil wrote:

---

T1 Terry wrote:

---

Izabarack wrote:

---

Mamil wrote:

---

On the other hand, if you do connect it to a charging source such as solar or AC while the van is in storage, then no need to worry. The BMS will let the battery run down to 90% (takes about two weeks) and then will charge it back up to 100% and switch off the charger, let it run down to 90% again and repeat, and repeat. This is not the same as constantly trickle charging and so doesn't damage the Lithium battery.

 

---

 Maybe not the same as being on trickle charge, but not different to putting the batteries into storage at full charge. 

Iza

---

 As Iza has said, it is not the same as leaving the battery in storage mode, and depending on the sensing the BMS has, it could very likely not stop the short charging cycle damaging the battery.

I'll try to explain why:

Sadly very few BMS systems actually monitor the cell voltages and base their warning systems from there, so it is very likely a repeated charging from 90% SOC to 100% SOC will be based on total battery voltage and not individual cell voltages. A lithium ferrous cell will be damaged if repeated pushed above 3.6v, (there are 4 cells in a 12v battery). If the cell voltage isn't monitored, the combination of 4 cell voltages can total what ever the BMS considers to be 100% charged voltage yet have one of the cells at higher than the safe max of 3.6v. Each short cycle will push this cell even further out of balance as this happens at the very end of the charging cycle. The run away cell is being pushed ever higher with a charging rate much higher than can be contained by the internal cell balancing system (generally limited to 0.5 amps max) cell damage is the end result.

 

T1 Terry

Tried to put commas in the right place to make it readable, probably still looks like a dogs breakfast but hopefully it's a bit better

-- Edited by T1 Terry on Monday 27th of May 2019 05:42:56 PM

---

Interesting Terry, but there's a couple of things in your explanation I don't understand...

As the whole point of the internal cell balancing system is to balance out the cells at the top of the charge cycle, by burning off current from the fully charged cells and letting the less charged cells catch up, why would it be operating in the opposite way to push the cells with the highest charge even higher?

Secondly, as cell balancing only happens at the end of the charge cycle, what difference does it make whether the battery was "short cycled" or deep cycled?

---

The charge burn off type balancers don't generally start until the cell is well and truly over voltage, but then they only burn off 0.5 amp at the very best. I have a few of these balance boards that burn off 2 amps and the heat generated is substantial requiring them to be mounted to an actual heat sink to stop them from failing due to heat stress. When they fail they no longer turn off, they continue to load that cell causing their own set of problems. The heat pumped into the cell while it already heat stressed due to over voltage charging is yet another issue and inside a sealed battery case ....... how does it cool?

The more common and better quality balancers these days use a inductor coil on each cell and switch from single cell to parallel mode linking all the inductors together, then back to single cell mode. This effectively moves current from a high voltage cell to a lower voltage cell, therefore, actually transferring some of the capacity from one cell to the other. These type balancer circuits work all the time. 

If your lithium battery still uses the burn off type balancers, be prepared for a short cycle life. The heat from the burn off balance board will destroy the run away cell by gradually reducing its capacity, this is how the high cell ends up going even higher voltage. The BMS is not linked to the charger so it doesn't know to reduce the charge rate to less than the discharge capability of the balance board.

This loss of capacity guarantees it will be the first to reach the top of charge and go over voltage and also being the first cell to discharge to a point where the low voltage again creates internal heat in the damaged cell. The death spiral is rapid and in a sealed top battery there is no way of knowing it is happening and no way to stop it.

Something to think about, if the BMS was linked to the charge controller and able to drop the charge rate to less than 0.5 amps, how long would it take to finish charging a cell that say only 3 Ah behind the top cell? Now think of how long it takes to get the cells to the point the run away cell goes high voltage, how many hrs does the sun shine? Unless you are recharging from mains power there simply isn't the time frame available to do a proper top balance on a house battery pack due to the capacity of each cell. These systems were designed for the early electric vehicles that had 40Ah cells, not 100Ah or higher capacity cells. It is not unusual to be fitting 400Ah battery packs these days, a 2% difference between the highest capacity and the lowest capacity is an 8 Ah capacity difference, 16 hrs to fix that with a 0.5 amp burn off type discharge balancer, that is a long time to be subjecting a cell to that sort of heat punishment, you have to expect there will be some sort effect on that cell.

 

T1 Terry 

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Terry, I don't doubt your knowledge in this area, but sometimes I wonder if knowing so much about what could potentially go wrong leads you to take an overly pessimistic view of what will go wrong. From what you say above someone could worry that any off-the-shelf Lithium setup is doomed to failure, yet most seem to do what it says on the tin.

I think all Branchie really needs or wants to know about his new system is that if the Redarc charger and battery's internal cell balancing system perform as designed he'll be alright 

-- Edited by Mamil on Tuesday 28th of May 2019 07:19:55 PM

Mamil wrote:

---

 

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Terry, I don't doubt your knowledge in this area, but sometimes I wonder if knowing so much about what could potentially go wrong leads you to take an overly pessimistic view of what will go wrong. From what you say above someone could worry that any off-the-shelf Lithium setup is doomed to failure, yet most seem to do what it says on the tin.

I think all Branchie really needs or wants to know about his new system is that if the Redarc charger and battery's internal cell balancing system perform as designed he'll be alright 

-- Edited by Mamil on Tuesday 28th of May 2019 07:19:55 PM

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 That is the whole problem, there is no way of knowing if it will be alright and from hands on experience I can assure you that many of the drop in systems will run into problems after around 2 yrs. We have had customers in the workshop that only got 7 mths before one of the drop in batteries failed. After much fighting they replaced the failed battery but would not replace the second battery and told them in no uncertain terms that they would not receive anything more. The seller updated their website to say their batteries could not be used in parallel. The replacement battery started to do exactly the same thing as the failed battery had done early on after the install. I managed to get the two batteries to sort of work together and 6 mths later we received a thank you email our Christmas saying the system was finally doing what they had hoped.

I'm wondering if anyone who has fitted drop in lithium batteries will own up to problems when they start to occur, pride can be a terrible thing.

As I have said before, we can try to sort out the system to get it to sort of work the way you'd hoped, but there is no substitute for building the battery properly and installing a proper BMS system.

 

T1 Terry

Ron-D wrote:

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The only sensible thing to do would be buy one from Terry he hnow everything 

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  You missed my signature line Ron :lol: But I am the one with the most active systems on the road that I get constant feed back from over the last 8 yrs, no one else in the world can claim that title. I really do have the most experience using lithium ferrous batteries as house power batteries in RV's and off grid systems.

Many may claim yrs of experience with lithium batteries, but they are talking about lipo batteries in model planes etc for the majority of the yrs of lithium experience they are claiming. The only relative claimable experience is using the same lithium chemistry and in the field you plan to use the battery, the rest in meaning less. 

Should I be excited I've reached the Tall Poppy status in you view Ron? No doubt you did a Google search to try and prove me wrong and didn't find what you had hoped for ...... The fact I give the information out on this forum and others for free doesn't attract any brownie points in your book does it Ron

 

T1 Terry