A curious entry on battery user manual. Parallel or Series are not supported?!?!?!?!! (1 Viewer)

[poindexter]

Hey forum, really interested to get your views on this.

I've got x2 of these batteries. They are 200AH each, 12v, Lithium:

I am in the process of installing the electrical setup. I had a quick read up of the manual to understand what the maximum charge amps would be in order to size up the breaker and noticed this:

err, what the heck? Putting the awful grammar aside they are basically saying don't put these batteries into series or parallel config??!?!?!?!?

What are your thoughts please?

 

[poindexter]

This has got to be BS? Surely?

 

[dunnah01]

I think they"re saying get a grown up to do the connections and don't use your 3 month old grandkid

 

[Lenny HB]

With Lithium batteries there is a BMS (battery management system) between the batteries and the terminals so you are connecting to an electronic circuit not direct to the batteries.
So it's possible the BMS does not support series or parallel connection.

Just looked up those batteries they are very cheap so it doesn't surprise me that you can't connect in series or parallel most manufacturers state how many batteries you can series or parallel.

 

[poindexter]

OK well thats rather frustrating. So I can't wire them in series or parrallel. Pffff.

Thats actually a major f*** up.

Now im stuck with two massive great batteries that cannot serve the same circuit at the same time.

Its either sell the batteries (both brand new basically) but who would trust that or design a split circuit in the van where half of the gear runs off one battery, the other half off the other. This is a bad option. Im gonna need an extra inverter to do this.

Oh Please!.

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[Lenny HB]

Can you return them?

If not you could try them in parallel and see how they behave.

Another option is to fit a couple of selector switches so you could switch the load between batteries but you would also need to switch the charging.

 

[poindexter]

With Lithium batteries there is a BMS (battery management system) between the batteries and the terminals so you are connecting to an electronic circuit not direct to the batteries.
So it's possible the BMS does not support series or parallel connection.

Just looked up those batteries they are very cheap so it doesn't surprise me that you can't connect in series or parallel most manufacturers state how many batteries you can series or parallel.

Wait a minute. These batteries do two things. They either serve power or they receive power. Simple, surely.

If I cable them up in parallel any current that is either drawn from or returned two will be simply divided in half.

How exactly is the battery ever going to know if it is in a parralel config or not? I could put 100 of them in parallel. The battery's BMS would never have any way of knowing this.

OK, cabled in series I get it. The voltage doubles, or triples or basicaly multiplies by x number of batteries that are in the series. Electrical appliances don't like running on higher voltage than they are supposed to. If the battery has advanced circuitry it is basically an appliance within its self. But in parallel. I dont think that there is any way that the battery could be impacted by that setup.

 

[poindexter]

Can you return them?

If not you could try them in parallel and see how they behave.

Another option is to fit a couple of selector switches so you could switch the load between batteries but you would also need to switch the charging.

Nope. Purchased them about a year ago. Didn't get around to finishing the van yet.

Unless anyone can put forth knowlege to counter my previous logic (I could always be wrong!!!) thats what im gonna do.

 

[Lenny HB]

I've done a bit of Googling a couple of sellers say you can parallel upto 4 of them. The worse that can happen is the BMS will shut down, I would just go for it nothing to lose.

 

[AdrianChen]

If there is any contact information I think I would check with them - hopefully it is just caution on their part, using poor language - Are you going to be using their chargers?

I agree with Lenny, and if they are not designed for parallel operation the issue will likely be in cell balancing, and at some point one battery may shutdown at times, either as loads are switched on, or during charging, without any advice from Kepworth the best you can do is ensure they are fully charged when you connect them, and try to get the interconnects/cables the same size. and periodically charge them individually.

If you don't need their combined current output, you could use them separately I guess with a battery selection, or "1 2 both" switch, using both only when necessary?

https://www.kepworth.com/lifepo4-energy-storage-battery/ - Still says the same thing in their blurb.......

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[headlight]

poindexter it doesnt say they cant be series or parallel, it says "series or parallel needs to be under the guidance of a professional battery engineer".
In other words you need to know what your doing if you join them in series or parallel.

 

[Raul]

Parallel no problem, when it meets a charger or a load behaves the same. Parallel them with equal cables the take all the charging and discharging all from the same point: positive from batt1 and neg from batt2.
That manual is old bad chinglish.

 

[MichaelT]

Parallel no problem, when it meets a charger or a load behaves the same. Parallel them with equal cables the take all the charging and discharging all from the same point: positive from batt1 and neg from batt2.
That manual is old bad chinglish.

Would it be better to join them with a busbar then take the feed from there?

 

[Raul]

Would it be better to join them with a busbar then take the feed from there?

Why? Flexible cable to join is better, as you need to go round to the next terminal is not a straight line, then you need some hefty heat-shrink to cover the bar. You can run two cables to a buss bar if needed a single common point.

 

[Carpmart]

Load of old tosh in the instructions… of course you can run them in parallel. The cell packs neither know or care that they are connect to another cell. It then just acts as one battery with two BMS’s which is fine.. been doing it for over four years with my KS lithiums.

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[MichaelT]

Why? Flexible cable to join is better, as you need to go round to the next terminal is not a straight line, then you need some hefty heat-shrink to cover the bar. You can run two cables to a buss bar if needed a single common point.

I meant have 1 positive and 1 negative busbar then connect each battery to them and the take feeds from there, still use flexible cable to get to the bars and you can buy busbar with covers?

 

[Carpmart]

Load of old tosh in the instructions… of course you can run them in parallel. The cell packs neither know or care that they are connect to another cell. It then just acts as one battery with two BMS’s which is fine.. been doing it for over four years with my KS lithiums.

Just to add, same mm2 cables, same length and you’ll be fine!

Also, in addition to the two KS Cylindrical cell lithiums, I’ve added a third in parallel of half the capacity of the other two and EVE cells. Again, no issue.

 

[Raul]

I meant have 1 positive and 1 negative busbar then connect each battery to them and the take feeds from there, still use flexible cable to get to the bars and you can buy busbar with covers?

Yes of course, parallel them to a bus bar, with equal cables.

 

[AdrianChen]

Sales@yingdabattery.com confirm there is no problem, so caution/poor English.

 

[Pausim]

Some of the Amazon reviews say they are being used in parallel and series.

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[oldiesontour]

Jusst bought a 200a BMS instructions seemed to say similar,I contacted supplier in China parallel OK series 4 only.

 

[Madcaravanner]

Simplest thing is to contact the supplier and Ask

When it comes to how a BMS is set up there is never a silly question - you need your battery bank to function 100% of the time
You don't want to destroy a battery with the price that 200amp Lithiums are

 

[oldiesontour]

Personally I would have a look on eBay, Amazon,Ali express find the same one and ask the sellers posing as a potential new buyer...if you can't find out from your supplier.
If all else fails go for it the worst you can do is kill the BMS and have to replace them with better quality 200a Bluetooth heater control £50

 

[autorouter]

It is important that the voltages of the battery are exactly equal during both charging and discharging. In theory when you connect them in parallel, the voltages will be equal. But in practice, the link wires have a small but non-zero resistance, so there will be a voltage drop across them. If the link wires and connections are not arranged carefully, there will be slightly different voltage drops across the links, so the batteries will be charged and discharged at slightly different voltages. Because the voltage curve of the lithium battery is so flat, a small voltage difference makes a large difference in the charging and discharging amps. So it's a good idea to ensure that the link wires are arranged so that the voltage drops are exactly equal. There are basically two ways to do this. One method works only for two batteries, the other method works for any number of batteries.

The first method is to connect the load/charging positives to the positive of one battery, and the load/charging negatives to the negative of the other battery. Then use two identical link wires, one to link the two battery positives, and the other to link the two battery negatives. This method only works for two batteries. It's better than nothing for three or more batteries, but it's only exactly right for two.

The second method is to connect the load/charging positives to a common point, like a busbar, fuse or isolation switch. Then connect exactly equal links from that common positive to each of the battery positives. Then do the same for the negatives. The common point can be a negative busbar, or the battery side of a shunt if you are using a shunt. This method works for any number of batteries.

Either of these methods would work, I think. But then I'm not a 'battery engineeri' so what would I know?

 

[oldiesontour]

It is important that the voltages of the battery are exactly equal during both charging and discharging. In theory when you connect them in parallel, the voltages will be equal. But in practice, the link wires have a small but non-zero resistance, so there will be a voltage drop across them. If the link wires and connections are not arranged carefully, there will be slightly different voltage drops across the links, so the batteries will be charged and discharged at slightly different voltages. Because the voltage curve of the lithium battery is so flat, a small voltage difference makes a large difference in the charging and discharging amps. So it's a good idea to ensure that the link wires are arranged so that the voltage drops are exactly equal. There are basically two ways to do this. One method works only for two batteries, the other method works for any number of batteries.

The first method is to connect the load/charging positives to the positive of one battery, and the load/charging negatives to the negative of the other battery. Then use two identical link wires, one to link the two battery positives, and the other to link the two battery negatives. This method only works for two batteries. It's better than nothing for three or more batteries, but it's only exactly right for two.

The second method is to connect the load/charging positives to a common point, like a busbar, fuse or isolation switch. Then connect exactly equal links from that common positive to each of the battery positives. Then do the same for the negatives. The common point can be a negative busbar, or the battery side of a shunt if you are using a shunt. This method works for any number of batteries.

Either of these methods would work, I think. But then I'm not a 'battery engineeri' so what would I know?

Would the cell balance on ech cell not take care of any minor differences assuming BMS in batteries are identical. ? Any info appreciated

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[Awboxster]

Nope. Purchased them about a year ago. Didn't get around to finishing the van yet.

Unless anyone can put forth knowlege to counter my previous logic (I could always be wrong!!!) thats what im gonna do.

I have two Kepworth 100amp LifePo4 batteries and they are connected in parallel....they have been in this configuration since last March (2023) and they have been OK.