Problems with renogy 170ah batteries

[meerkatmag]

This has turned into a very useful resource for anyone with these batteries. I suspect this will happen to them all in the end as the bms is obviously useless.

Renogy informed me yesterday that they are honouring the warranty for mine so I'll be getting new ones. I'm going to open up the old ones and try to replace the bms with JK-B2A8S20P bms. I'll take photos and report back in case it helps anyone in future.

Thanks yzman for the photos that will help a lot. Any advice for doing this or if that bms isn't right please let me know.

By the way I have had one battery on absorption for two days now at 13.59 and it seems to have done very little. I still can't up the voltage even by .1v before it cuts off. So I don't think they would ever recover.

 

[Yzman321]

This has turned into a very useful resource for anyone with these batteries. I suspect this will happen to them all in the end as the bms is obviously useless.

Renogy informed me yesterday that they are honouring the warranty for mine so I'll be getting new ones. I'm going to open up the old ones and try to replace the bms with JK-B2A8S20P bms. I'll take photos and report back in case it helps anyone in future.

Thanks yzman for the photos that will help a lot. Any advice for doing this or if that bms isn't right please let me know.

By the way I have had one battery on absorption for two days now at 13.59 and it seems to have done very little. I still can't up the voltage even by .1v before it cuts off. So I don't think they would ever recover.

I’m surprised they will let you keep the old ones while providing replacements! Good to hear!

I think your BMS choice is great! The existing negative eye terminals should bolt up nicely on the BMS, all you need to do is double them up on both sides. This BMS choice is more practical for people than my one BMS 16s configuration, unless they want a 48v pack. With the JK BMS you can turn on and off the active balancing when you wish and you have 2 amp balancing, good for 170ah strings.

I’m interested in photos of your project and also the cell voltages to see if cell 4 was high on your batteries like mine. I’ve had my batteries for for 3 years now, and only converted them to a new BMS in September. They used to all work fine until they shocked me the 35 percent useable capacity for four of them in parallel.

 

[740GLE]

cheaper to send new batteries that ask him to return, it’s built into their fluff of warranty items.

Does sound like this will be a problem for many batteries and it’ll be the “push overs” that wont fight for warranty claims.

 

[meerkatmag]

I don't know whether to laugh or cry. Renogy sent me two brand new replacement batteries. One of which is totally fine, charged up to 14.2v stayed up around that, now sitting at 14v after sitting over night. Sounds good to me.

The other one I can't set a charge voltage any higher than 13.95v otherwise it goes into protection and cuts voltage down to 13.3v.

I think it's the same problem, they have made a battery with unbalanced cells from new, it's presumably sat in a factory for a year or so and the problem has got worse as the BMS is useless. There's no way I can string these two in parallel.

I've told renogy, not sure what they are going to do if anything. They can't keep sending me new batteries surely.

I'm seriously so fed up of this!

 

[Yzman321]

I don't know whether to laugh or cry. Renogy sent me two brand new replacement batteries. One of which is totally fine, charged up to 14.2v stayed up around that, now sitting at 14v after sitting over night. Sounds good to me.

The other one I can't set a charge voltage any higher than 13.95v otherwise it goes into protection and cuts voltage down to 13.3v.

I think it's the same problem, they have made a battery with unbalanced cells from new, it's presumably sat in a factory for a year or so and the problem has got worse as the BMS is useless. There's no way I can string these two in parallel.

I've told renogy, not sure what they are going to do if anything. They can't keep sending me new batteries surely.

I'm seriously so fed up of this!

Very interesting! One good and one bad, that I’m sure will become two bad overtime. The internal cells have been good in my experience, so that’s an additional 340ah once fitted with a new BMS.

Do you still plan on tearing town and retrofitting the JK BMS?

 

[meerkatmag]

Very interesting! One good and one bad, that I’m sure will become two bad overtime. The internal cells have been good in my experience, so that’s an additional 340ah once fitted with a new BMS.

Do you still plan on tearing town and retrofitting the JK BMS?

Yep I'm going to, have ordered one just waiting for it to arrive. I'm going to try one first, if it sorts it I will consider doing all of them. Quite a lot of cash for 4 new BMSs but I'm thinking it's worth it. I'll take photos and report back for others to follow.

 

[meerkatmag]

If anyone is interested in the Renogy BMS - I have done some research and have been experimenting on my batteries. This is what I think is going on.

I think the batteries have a resistive style passive top balancing system. What happens is when a cell reaches over voltage state a switch activates a circuit on that cell that applies a resistor in a loop. This resistor pulls a current from the cell and burns the energy off via heat. This discharges that cell and has an effect on the overall voltage of the battery pack by dropping the total volts by a significant amount, essentially half bypassing that cell. In this state the high voltage cell is discharging while the others are staying as they are. In theory it will balance if left like this and it stays in this state until the high cell voltage drops to below the threshold for the switch.

However, this passive balancing only happens when the battery pack is charged up fully and the high cell goes beyond some voltage limit. So if the charger is set to a profile of 14.2v for example (like victron does by default) it may not enter the balancing mode as you are just under the volt limit for the highest cell, however the cells could be already quite out of balance at this point.

I have tried keeping the battery in absorption mode for 2 hours (as renogy suggests) hoping that while the high cell is bypassed the other cells will charge up at the same time. This would hugely increase balancing time, however the BMS seems to stop all charge going in to the battery while any of its cells are fully charged, so no current passes through and the overall balance doesn't seem to be improved any more than just leaving it at idle fully charged.

On my best battery - the one that charges up to 14.2v happily and stays there, I am trying the above method to top balance and it seems to be improving it. Currently 14.3v is the max charge I can do before it enters cell protection. If I leave the battery in this protection mode - it takes many hours for the voltage to slowly drop by a few .1s of volts. Then I can charge it up again and it seems to be slightly more in balance each time, the 14.3v limit will hopefully creep up over a few days until I can get it to charge to 14.4v. I will continue doing this and will report back, but so far it seems to be working very very slowly.

However the issue with my older batteries is the cell imbalance must be so bad that the amount this top balancing is doing is not enough to make any noticeable difference. One of my batteries is sat at 12.84v. I believe this is in cell protection mode on one of the cells. It has sat there for 3 days now and the voltage has dropped by perhaps 0.01v ish. I would estimate it will take months if not years to balance itself like this.

Something else I have noticed. As soon as you add a load to the battery the voltage on the high cell drops enough to pull the resistive switch off and the pack goes back to normal. In this mode it doesn't balance anymore. So in normal use where there is some parasitic load always on the battery it will never balance. It might hit the protection/balance mode briefly but then the volts drop on the pack, any load on there pulls even more amps and it drops it out of balance mode again.

I think this is the BMS Module used: https://www.facebook.com/lithiumval...dvantages-flexible-number-o/1140968249661089/. I had trouble finding specs but maybe someone on here knows more about it?

I think replacing the BMS is clearly the best option with these batteries. Otherwise I would suggest regularly disconnecting the batteries from any load and charging right up to full and then waiting for the top balance to do its thing. That means watching the voltage, it should be low in protection mode, over hours or days it will gradually go down. Eventually it will pop back up to normal voltage. You can then charge it up again and repeat. Perhaps if you did this regularly from new it would just about be able to keep itself in order.

I'd love to know if anyone can check my findings and confirm. If there's any mistakes here please let me know and I'll take this down, don't want to leave incorrect info for future renogy 170ah victims.

 

[740GLE]

I noticed a huge difference in changing my JBD BMS balance when not charging and have my SCC hold absorption for 2hr each day, basically it would balance a little bit each day when a cell went above 3.4v delta went from 80mv to 1mv at 3.4v. after a couple weeks.

IMO These premade batteries value are 90% the cells, be glad you have more cells now and have the ability to retrofit a proper BMS.

 

[meerkatmag]

I’m surprised they will let you keep the old ones while providing replacements! Good to hear!

I think your BMS choice is great! The existing negative eye terminals should bolt up nicely on the BMS, all you need to do is double them up on both sides. This BMS choice is more practical for people than my one BMS 16s configuration, unless they want a 48v pack. With the JK BMS you can turn on and off the active balancing when you wish and you have 2 amp balancing, good for 170ah strings.

I’m interested in photos of your project and also the cell voltages to see if cell 4 was high on your batteries like mine. I’ve had my batteries for for 3 years now, and only converted them to a new BMS in September. They used to all work fine until they shocked me the 35 percent useable capacity for four of them in parallel.

Cell voltages in one of my batteries. This is one of the worst ones. Confirms your findings that cell 4 is always the high one. I wonder why this happens?
Cell 1: 3.262
Cell 2: 3.256
Cell 3: 3.261
Cell 4: 3.528

 

[sunshine_eggo]

I don't know whether to laugh or cry.

Neither.

Renogy sent me two brand new replacement batteries. One of which is totally fine, charged up to 14.2v stayed up around that, now sitting at 14v after sitting over night. Sounds good to me.

The vastly larger shock would be getting two balanced batteries.

The other one I can't set a charge voltage any higher than 13.95v otherwise it goes into protection and cuts voltage down to 13.3v.

I think it's the same problem, they have made a battery with unbalanced cells from new, it's presumably sat in a factory for a year or so and the problem has got worse as the BMS is useless. There's no way I can string these two in parallel.

As do almost all manufacturers. The time between assembly/installation and the requirement to not ship batteries above 30% SoC essentially guarantees a high probability that any top balance will be lost. The last time those were touched at the factory is typically 30-90 days - more than enough time for even a balanced battery to lose a top balance.

I'm seriously so fed up of this!

Your first battery is an extreme - horrifically unacceptable. You're entitled to outrage on that one. For the two new ones, that's just par for the course... you should feel elated that ONE is balanced. I'm serious. Buy a lottery ticket... you're on a winning streak.

A SoC imbalance of as little as 0.1% can trigger over voltage protection and prevent charging to peak voltage.

A 1% imbalance (1Ah) will take 24-48 hours of passive BMS balancing to burn off 1Ah. This means you must hold the battery at a voltage that guarantees continuous passive balance operation for 24-48 hours.

 

[Whinny]

I'm having the same issue with a 50ah Renogy battery. It appears in my case the BMS was not balancing at all, it was tested by interrupting a BMS lead and connecting an ammeter. I put a load (light bulb cuz I had it) on the remaining cells to force a voltage drop, no current flowed through the balance lead. I connected a JBD 60 amp smart and all seems fine, balance current is shown-I thought it would be less.
I did cut the case apart, it seemed easier than beating on it with a screwdriver.

 

[Yzman321]

Cell voltages in one of my batteries. This is one of the worst ones. Confirms your findings that cell 4 is always the high one. I wonder why this happens?
Cell 1: 3.262
Cell 2: 3.256
Cell 3: 3.261
Cell 4: 3.528

Amazing! My batteries weren’t an outlier this means.

I also would like to know what is causing this? I believe there is something wonky with the original BMS with this consistency of cell's 1-3 being very tight while cell 4 being high. If you tested all four of your batteries, this would be 8/8 of the same characteristics. I wish Renogy would comment, as they 100% know why, this must be a nightmare product for them.

Originally, I wanted to changeout all BMS's with JK BMS's however the cost of doing so is huge, so I went with one JK BMS and a 16 string. If you have any use of 51.2V packs, it's the most economical. I can also send pictures of how I put them in series without any additional material. These batteries are great in that regard, but nothing else!

 

[Jeffah]

Glad to have found this thread, I have 2 x 170ah Renogy batteries that have been replace TWICE under warranty in less than 2 years ie 6 batteries in total and after the last set were sent to me and numerous amounts of charging & testing videos emailed Renogy offered me a partial refund which I declined and eventually got a full refund ( Renogy said to just bin the defective batteries ).
I have had exactly the same experience as the other people have posted here and had concluded it was the Renogy BMS system employed in the 170 ah battery’s that was at fault , in Australia it’s have to get anyone to take / dispose of lithium batteries and I still have 4 of the 6 batteries sitting in my garage, such a waste to have to dump them just because of the dodgy BMS system.

 

[meerkatmag]

Glad to have found this thread, I have 2 x 170ah Renogy batteries that have been replace TWICE under warranty in less than 2 years ie 6 batteries in total and after the last set were sent to me and numerous amounts of charging & testing videos emailed Renogy offered me a partial refund which I declined and eventually got a full refund ( Renogy said to just bin the defective batteries ).
I have had exactly the same experience as the other people have posted here and had concluded it was the Renogy BMS system employed in the 170 ah battery’s that was at fault , in Australia it’s have to get anyone to take / dispose of lithium batteries and I still have 4 of the 6 batteries sitting in my garage, such a waste to have to dump them just because of the dodgy BMS system.

The cells are absolutely fine so please don't dump them. If you can change the bms yourself you can make them work. I can send some instructions and images. Otherwise I'm sure you can donate them to someone local who will use the cells? Perhaps now it's posted here someone will offer?

Great you got a refund, can't believe renogy are still selling these!

 

[meerkatmag]

Neither.



The vastly larger shock would be getting two balanced batteries.



As do almost all manufacturers. The time between assembly/installation and the requirement to not ship batteries above 30% SoC essentially guarantees a high probability that any top balance will be lost. The last time those were touched at the factory is typically 30-90 days - more than enough time for even a balanced battery to lose a top balance.



Your first battery is an extreme - horrifically unacceptable. You're entitled to outrage on that one. For the two new ones, that's just par for the course... you should feel elated that ONE is balanced. I'm serious. Buy a lottery ticket... you're on a winning streak.

A SoC imbalance of as little as 0.1% can trigger over voltage protection and prevent charging to peak voltage.

A 1% imbalance (1Ah) will take 24-48 hours of passive BMS balancing to burn off 1Ah. This means you must hold the battery at a voltage that guarantees continuous passive balance operation for 24-48 hours.

Thanks for this info, its really interesting. It's all a learning curve to me, I assumed that a company selling sealed batteries would include an active balancing system as it seems to best way to avoid warranty replacements! Seems like commercial madness to sell batteries that are out of balance and don't have a BMS capable of balancing properly. But like you say it seems par for the course.

I have replaced the BMS in the worst of my batteries, it is working well now and has been balancing for 17hours so far and is still nowhere near finished. It will take multiple days, perhaps a week working at 2a.

Slight issue is the case doesn't really have enough space for the JK BMS, i have to squash it to close the lid, so that's not ideal. Trying to decide whether to buy new enclosures and build them again from scratch. It's going to cost so much money to buy new enclosures and BMSs for all the batteries I have.

I think my takeaway from all this is it's best to buy decent batteries from the beginning from a company that includes a decent BMS with active balancing and some customer care knowhow!

 

[740GLE]

I wonder if the new test “gold standard” of these off the shelf batteries will not be low temp charging cut off

But how does the BMS handle unbalanced cells.

Once the battery is opened it wouldn’t take much to drain a few Whr out of a cell and track how the BMS brings the cell back up.

Sure in an ideal world everything would be balanced, butttt then we have renolgy.

 

[meerkatmag]

I wonder if the new test “gold standard” of these off the shelf batteries will not be low temp charging cut off

But how does the BMS handle unbalanced cells.

Once the battery is opened it wouldn’t take much to drain a few Whr out of a cell and track how the BMS brings the cell back up.

Sure in an ideal world everything would be balanced, butttt then we have renolgy.

I wish it was easier to open the case, I practically destroyed mine trying to get at the cells. Agree once you can get in it could be easily rectified.

I am doing some long term tests on my newest ones to see if they will self balance if left for long enough. If left fully charged up they do self balance but its extremely slow.

 

[740GLE]

I wonder if they have balance when charging enabled, if so charging at some crazy value like 100mA for days on end may help out.

 

[meerkatmag]

I wonder if they have balance when charging enabled, if so charging at some crazy value like 100mA for days on end may help out.

I'm no expert, but from my experimentation, it only balances when a cell gets to overvoltage state, it then discharges that cell while leaving the others unchanged. So it gradually lowers the voltage of the high one until they all align. I don't see any evidence of it doing this during normal charge. It must discharge at a tiny rate though so it takes literally days for the cell to drop any noticeable amount, the moment you start using the battery it stops balancing.

 

[sunshine_eggo]

I'm no expert, but from my experimentation, it only balances when a cell gets to overvoltage state, it then discharges that cell while leaving the others unchanged. So it gradually lowers the voltage of the high one until they all align. I don't see any evidence of it doing this during normal charge. It must discharge at a tiny rate though so it takes literally days for the cell to drop any noticeable amount, the moment you start using the battery it stops balancing.

most passive balancers are in the 30-70mA range, so 1-2 days of continuous balancing to make a 1Ah difference.