Lithium upgrade

[stevensmith91]

Ok looking for some advice , I’m collecting my new Pilote Motorhome in two weeks time and have asked the dealer to fit a lithium battery
also fitting an inverter so I can run my 600 watt microwave occasionally for a maximum 3-4 minutes
I have a 2000 watt Renogy pure sine wave inverter what would be the minimum amperage Lithium battery I would need

 

[Admin]

You will need a battery that can output 200 Amps of continuous current to run a 2000 Watt inverter at full power.
A 600 Watt microwave may draw around 1200 watts of power from the inverter.

As far as the capacity, I would recommend 200Ah+

Phil

 

[Exwindsurfer]

You will need a battery that can output 200 Amps of continuous current to run a 2000 Watt inverter at full power.
A 600 Watt microwave may draw around 1200 watts of power from the inverter.

As far as the capacity, I would recommend 200Ah+

Phil

Iwas going to say the same Phil but i thought let someone who knows say lolol.

 

[Geek]

What would be the minimum amperage Lithium battery I would need

I'm not sure which of the two possible questions you are asking here.

Basically, a battery has a storage capacity measured in ampere hours. This is how much energy is stored in it. A 100Ah lithium battery can deliver 10 amps for ten hours, giving 1320 watt hours of power.

You are talking about taking maybe 2000 watts for five minutes, so that's only 166 watt-hours. No problem for a 100 Ah battery.

There is another capacity measure: how much current you can draw from the battery. In general, it's best not to ever exceed the two hour rate, even briefly. That basically means you shouldn't be taking more than 50 amps from a 100Ah lithium battery.

If you plan to draw 150 amps from lithium, you want at least 300Ah of battery. Preferably significantly more.

 

[Admin]

Basically, a battery has a storage capacity measured in ampere hours. This is how much energy is stored in it. A 100Ah lithium battery can deliver 10 amps for ten hours, giving 1320 watt hours of power.

LFP (LiFePO4) batteries are calculated at 12.8v. A 100Ah 12.8v LFP battery is 1280 watt-hours.

There is another capacity measure: how much current you can draw from the battery. In general, it's best not to ever exceed the two hour rate, even briefly. That basically means you shouldn't be taking more than 50 amps from a 100Ah lithium battery.

Many LFP cells can output at 1C, so an EVE 280Ah prismatic cell can be discharged at 280A.

Provided that the battery is rated at 200A continuous discharge, then it will be fine. The max discharge is more to do with how much power the battery management system is rated at.

 

[Geek]

My lithium batteries, and all the other ones I have known all run at 13.2v. Yes, when near flat they'll drop to 12.8v but for the vast majority of the discharge it's 13.2v.

You may find some batteries that can be discharged at 1C but the ones I know about can't be without damage. 0.5C is pushing your luck, let alone 1C. However, at 1C you probably would see a volt drop towards 12.8v.

And yes. I expect the limitation is in the BMS rather than the cells or the connections. Something has to be the limiting factor.

 

[wildebus]

My lithium batteries, and all the other ones I have known all run at 13.2v. Yes, when near flat they'll drop to 12.8v but for the vast majority of the discharge it's 13.2v.

You may find some batteries that can be discharged at 1C but the ones I know about can't be without damage. 0.5C is pushing your luck, let alone 1C. However, at 1C you probably would see a volt drop towards 12.8v.

And yes. I expect the limitation is in the BMS rather than the cells or the connections. Something has to be the limiting factor.

Even Lithiums suffer from fairly significant voltage sag under load. Here is an example of my own batteries ....
Voltage dropped down to 12.72V when hit with a 0.25C load.

 

[mark61]

My lithium batteries, and all the other ones I have known all run at 13.2v. Yes, when near flat they'll drop to 12.8v but for the vast majority of the discharge it's 13.2v.

You may find some batteries that can be discharged at 1C but the ones I know about can't be without damage. 0.5C is pushing your luck, let alone 1C. However, at 1C you probably would see a volt drop towards 12.8v.

And yes. I expect the limitation is in the BMS rather than the cells or the connections. Something has to be the limiting factor.

Interesting about discharge temps.
The two I'm looking at, the sales people will tell you they can be discharged down to -20. This is backed up by info in data sheets, although data sheet will add "The temperature protection starts restricting discharge at 3˚ C low and 40˚ C high"

Bit meaningless unless it tells you what it restricts to.

 

[wildebus]

Interesting about discharge temps.
The two I'm looking at, the sales people will tell you they can be discharged down to -20. This is backed up by info in data sheets, although data sheet will add "The temperature protection starts restricting discharge at 3˚ C low and 40˚ C high"

Bit meaningless unless it tells you what it restricts to.

Mark, the "C" he is referring to is not Celsius, it is shorthand for a charge or discharge rate relative to the battery capacity.
So if you have a 100Ah battery and you have a load of 50A on it, you have a load of 0.5C (50A/100Ah).
when in my reply I said I got a voltage sag down to 12.72 at 0.25C, it was a load of around 50A on a 200Ah bank (50/200).

Ref his comment about damaging the battery at a discharge rate of 1C and pushing your luck even at 0.5C.... Any given battery will have the charge and discharge rates published in the data sheet. And a decent manufacturer will match the BMS used to the battery packs fitted. So if they quote a 100A discharge or charge rate for a 100Ah battery (which is a 1C rate), then it will do 1C and if it fails, it is under warranty for replacement.
Some batteries only have a 20A or 40A BMS on their 100Ah batteries. On the other extreme, Powerroad fit a 150A BMS on their 100Ah Infinity range (a 1.5C rate) and publise it specifically, which they wouldn't do if the battery would be damaged if used to that level.

 

[mark61]

Mark, the "C" he is referring to is not Celsius, it is shorthand for a charge or discharge rate relative to the battery capacity.
So if you have a 100Ah battery and you have a load of 50A on it, you have a load of 0.5C (50A/100Ah).
when in my replay I said I got a voltage sag down to 12.72 at 0.25C, it was a load of around 50A on a 200Ah bank (50/200).

Thanks very much.
All makes more sense now.

 

[wildebus]

Before replying, I did a quick search to see what "C" stood for? Dunno! could be "Charge", but it applies to discharge as well. Maybe "Columbs", but that doesn't fit either.
If anyone does know what "C" actually stands for.......?

 

[cheyenne]

You will need a battery that can output 200 Amps of continuous current to run a 2000 Watt inverter at full power.
A 600 Watt microwave may draw around 1200 watts of power from the inverter.

As far as the capacity, I would recommend 200Ah+

Phil

hi guys . i have just installed a 2000w renogy inverter powered from 2 / 110 lead carbon gel's . my quick test was 1500w hair /800w microwave /1500w electric frying pan & was happy with the performance BUT must say i will buy another 110 battery . but my system is a stand alone in the m/h garage just for outside cooking when parked up for the summer/winter ( in Europe ) for 2 months at a time as the electric bill would be between £180/£300 & the price of electric is NOT going down on these sites . plus being able to run the microwave in the m/h en route in a layby is a bonus . Cheyanne

 

[Admin]

Before replying, I did a quick search to see what "C" stood for? Dunno! could be "Charge", but it applies to discharge as well. Maybe "Columbs", but that doesn't fit either.
If anyone does know what "C" actually stands for.......?

C = Capacity in Ah.

 

[Geek]

Even Lithiums suffer from fairly significant voltage sag under load. Here is an example of my own batteries ....
Voltage dropped down to 12.72V when hit with a 0.25C load.

Interesting. The heaviest load my battery bank has ever seen is about 10 amps, so it never drops voltage significantly under load. The bank is over 400Ah but not all of that is lithium.

I find that drawing 10 amps from a 100Ah lithium will give you 13.2v not 12.8v.
If i wanted to draw high currents, I'd probably not choose lithium.

Yes, I know Tesla and their kin take a lot of power from their (cooled) lithium batteries, but that's at high voltage to reduce the current requirement.

 

[Admin]

Interesting. The heaviest load my battery bank has ever seen is about 10 amps, so it never drops voltage significantly under load. The bank is over 400Ah but not all of that is lithium.

I find that drawing 10 amps from a 100Ah lithium will give you 13.2v not 12.8v.
If i wanted to draw high currents, I'd probably not choose lithium.

Yes, I know Tesla and their kin take a lot of power from their (cooled) lithium batteries, but that's at high voltage to reduce the current requirement.

Lead acid batteries are 12v but fully charged are 12.8v. This is because we calculate watts across the discharge range not the peak voltage.

Just to get my point across here is a photo of a Relion 12v LiFePO4 100Ah battery. Please not that that the Wh rating is 1280 Wh.

 

[Geek]

You are quite right. The picture assumes 12.8v. Reality is different. At 10a load, you will get 13.2v.

 

[Admin]

You are quite right. The picture assumes 12.8v. Reality is different. At 10a load, you will get 13.2v.

No, you will not get 13.2v across the whole discharge band, this means your Wh capacity would be wrong. The Relion battery has four 3.2v banks/cells as do all 12v LFP batteries. 3.2v x 4 = 12.8v. This is how we calculate the energy capacity of batteries. Cell voltage x number of cells x Ah capacity = Wh capacity.

 

[nabsim]

Surely the fully charged voltage of a Lifepo4 battery will depend on the cells used?

Actually ignore that, I think I am getting confused with charging

 

[Geek]

I don't have a relion battery. I get 13.2v until it is pretty near empty. It bulk charges at around 13.2v as well (well. 13.3v more or less) Perhaps mine have different cell types?

 

[Admin]

I don't have a relion battery. I get 13.2v until it is pretty near empty. It bulk charges at around 13.2v as well (well. 13.3v more or less) Perhaps mine have different cell types?

You are correct that all LFP (LiFePO4) batteries do sit at around 13.6v - 13.2v when charged but that is the not how we calculate Wh.