Lithium Parallel In Harmony With Lead Acid

BatteryMegaUK said:
Hi Andy,

The max charging current is 50AH the max discharge current is 100AH.
Click to expand...
Did you mean 100 amps max discharge and 50 amps max charge because what you wrote there doesn't make sense I'm afraid.
Usually there is also a continuous discharge and max discharge rating. (One that it can maintain safely until flat and a higher discharge current that is time limited.
Do you know these figures?
 
HandyAndy said:
Did you mean 100 amps max discharge and 50 amps max charge because what you wrote there doesn't make sense I'm afraid.
Usually there is also a continuous discharge and max discharge rating. (One that it can maintain safely until flat and a higher discharge current that is time limited.
Do you know these figures?
Click to expand...
I think you will find that a LiFePO4 battery is far less troubled by discharge rates. Lead acid batteries waste more power the higher the rate of discharge. This is calculated using a formula known as Peukert’s Exponent, if I have understood the law correctly this means that in effect a 100Ah battery drops to perhaps 90Ah or 80Ah if you whack it particularly hard. The effect of heavy discharge on a Lithium battery is much less and can be mostly ignored. The recharge rate is also better on the Lithium, probably 99% whereas a Lead one is usually 95%. Not of much significance when on hook up or engine charging but may be relevant if you are struggling to keep up on solar power in a UK winter.
 
HandyAndy said:
what you wrote there doesn't make sense I'm afraid.
Click to expand...

Highly unimpressive to prospective buyers, they need to improve their performance.

Not only do you not measure current in AH, you measure charge in Ah.

I know "we" don't correct spelling in here but this is totally different.
 
Pausim said:
I think you will find that a LiFePO4 battery is far less troubled by discharge rates. Lead acid batteries waste more power the higher the rate of discharge. This is calculated using a formula known as Peukert’s Exponent, if I have understood the law correctly this means that in effect a 100Ah battery drops to perhaps 90Ah or 80Ah if you whack it particularly hard. The effect of heavy discharge on a Lithium battery is much less and can be mostly ignored. The recharge rate is also better on the Lithium, probably 99% whereas a Lead one is usually 95%. Not of much significance when on hook up or engine charging but may be relevant if you are struggling to keep up on solar power in a UK winter.
Click to expand...
The BMS will have a continious discharge and a max discharge current though ?
No point me dropping a grand on two batteries to find it cuts out trying to put the toaster on for eg ?

Subscribers  do not see these advertisements

 
Becks have a new Hymer for sale at the moment which has a "hybrid" system of two agms and a lithium battery.
 
Pausim said:
I think you will find that a LiFePO4 battery is far less troubled by discharge rates. Lead acid batteries waste more power the higher the rate of discharge. This is calculated using a formula known as Peukert’s Exponent, if I have understood the law correctly this means that in effect a 100Ah battery drops to perhaps 90Ah or 80Ah if you whack it particularly hard. The effect of heavy discharge on a Lithium battery is much less and can be mostly ignored. The recharge rate is also better on the Lithium, probably 99% whereas a Lead one is usually 95%. Not of much significance when on hook up or engine charging but may be relevant if you are struggling to keep up on solar power in a UK winter.
Click to expand...
Now I'm home I have a bit more time to explain rather than trying to post with one hand, ram some food down my neck with the other and have one eye on the clock :D
Lithium cells do have a discharge limit, essentially governed by thermal properties.
Some Lifep04 cells (individual 3.2v cells!!!!!!!!!) like the red headways can do 160amps max discharge 80 amps continuous at 3.2v. That's bonkers when you consider making a 12.8v battery it can produce 320 amps on its own SAFELY!

I bet your left bollock these don't do that though... :D
 
HandyAndy said:
Some Lifep04 cells (individual 3.2v cells!!!!!!!!!) like the red headways can do 160amps max discharge 80 amps continuous at 3.2v.

OK that makes sense.


That's bonkers when you consider making a 12.8v battery it can produce 320 amps on its own SAFELY!

I can't work that one out. 4 x 3.2 is indeed 12.8. But 4 cells can only produce 80A.
Click to expand...
 
  • Like
Reactions: DBK
HandyAndy said:
Some Lifep04 cells (individual 3.2v cells!!!!!!!!!) like the red headways can do 160amps max discharge 80 amps continuous at 3.2v. That's bonkers when you consider making a 12.8v battery it can produce 320 amps on its own SAFELY!
Click to expand...

Erm, NO! If a single cell can produce 80 amps continuous, then any number of cells in series will never produce more. Thus 4 3.2v cells in series will still produce 80amps, not the 320amps you claim.

Its not all that amazing, I have some standard 3Ah lithium batteries which will produce 150-160 amps continuous, though not for all that long.

Subscribers  do not see these advertisements

 
My bad.. you are of course correct. I was thinking of the battery I was going to make which had more than one set of 4 cells in it, then ended up multiplying the amps for this example when indeed in series the amps remain the same.. so 80 amps continuous it is...
but four ROWS of 80 amps cells in parallel...... Now we are cooking..... cables probably :D
The Red headways apparently do more than the 160amps recommended max in testing on a dead short...
This guy had 300 odd amps out of ONE cell hahaha.

 
thebriars said:
Erm, NO! If a single cell can produce 80 amps continuous, then any number of cells in series will never produce more. Thus 4 3.2v cells in series will still produce 80amps, not the 320amps you claim.

Its not all that amazing, I have some standard 3Ah lithium batteries which will produce 150-160 amps continuous, though not for all that long.
Click to expand...
all right keep your allens on :D I cocked up :D I was thinking of the entire battery pack which has 4 rows of 4 series cells in parallel.
 
HandyAndy said:
Did you mean 100 amps max discharge and 50 amps max charge because what you wrote there doesn't make sense I'm afraid.
Usually there is also a continuous discharge and max discharge rating. (One that it can maintain safely until flat and a higher discharge current that is time limited.
Do you know these figures?
Click to expand...

Please see specification sheet attached
 

Attachments

That's more like it. Thank you ??.
So at 12v (don't know yet what the voltage sag is going to be like at 100amp draw) we can see it can do 100 amps continuous with a max of 200amps for 3 secs.
Not bad!
 
HandyAndy said:
That's more like it. Thank you ??.
So at 12v (don't know yet what the voltage sag is going to be like at 100amp draw) we can see it can do 100 amps continuous with a max of 200amps for 3 secs.
Not bad!
Click to expand...
If my maths is right, with an internal resistance quoted as up to 45 milli ohms, (which is quite high) at 100 amps the voltage drop will be up to 4.5 volts.

Subscribers  do not see these advertisements

 
I was reading about the transporter lithium battery which if I read it right you can just swap them for lead with no alterations. They are advertising these a lot, but don’t answer email questions or reply when I have left a message. Why bother advertising when you can’t reply.
 
A little off course here I know.

The blurb for Lithium drop in batteries all say they can be charged using existing charging methods for lead acid/ agm,
What they don’t say is whether the charging system can handle the current that they want to suck from the system.
As I understand it to be safe you need some kind of current limiting gadget, why?

Now can someone tell me when I start my van from the 110Ah start battery it has to supply a very large amount of current to turn over the engine, depleting the battery.
Once the engine is running the alternator then surely is working its socks off to recharge the battery.
I think the standard alternator on my van is rated at 95 amps , does this mean it can produce 95 amps straight up or over an hour?
I’ve read somewhere that the resistance, temperature and state of charge of the battery limits the current.

Now my point is this, if the alternator can produce this kind of power why would I need to upgrade the cables etc. to charge a lithium battery that wants to take everything I could throw at it,
Or is it to maybe protect the lithium battery itself from too much charging current hence the need to limit the current?

One for the auto electricians.
 
Off da Grid said:
I think the standard alternator on my van is rated at 95 amps , does this mean it can produce 95 amps straight up or over an hour?
Click to expand...
I think you might be confusing 95A with 95Ah. The first is a measure of the output at any particular moment, the second is the cumulative effect over the period of one hour. A 95A alternator can supply a flow of current of 95A.

A vehicle will have large cables that allow the alternator to rapidly recharge the engine battery after starting. A well built motorhome will probably have cables capable of carrying about 5OA from the engine battery to the leisure battery when the engine is running. Unfortunately it seems that there are still a lot of motorhomes with much weaker cabling. I think it would be unwise to generalise or guess what you have in any particular motorhome without checking. You should get a clue from the size of the fuse used on the cable that links the engine and leisure batteries.

I am reasonably happy to use the existing motorhome mains charger to top up my lithium (LiFePO4) battery, though it may not fully charge it. However, I use a B2B charger between the engine battery and the lithium leisure battery because this fully charges the lithium and protects both it and the engine charging system by separating them. Unlike lead acid batteries, lithium batteries are not damaged by under charging so when I am on an electric hook up this is not a problem.

Lithium battery manufacturers and sellers are understandably keen to point out that it is relatively easy to swap over from lead acid ones. My experience is that it is not quite as easy as some suggest but that with a bit of care, knowledge and investigation it can be done without too much difficulty. Having said this I have had my new motorhome for over a month now and have not yet switched over to my lithium battery because I am waiting for advice from CBE about disconnecting the battery linking relay built into their system.
 
I never had a problem with thin charging wire to my caravan battery ?
 
Off da Grid said:
A little off course here I know.

The blurb for Lithium drop in batteries all say they can be charged using existing charging methods for lead acid/ agm,
What they don’t say is whether the charging system can handle the current that they want to suck from the system.
As I understand it to be safe you need some kind of current limiting gadget, why?

Now can someone tell me when I start my van from the 110Ah start battery it has to supply a very large amount of current to turn over the engine, depleting the battery.
Once the engine is running the alternator then surely is working its socks off to recharge the battery.
I think the standard alternator on my van is rated at 95 amps , does this mean it can produce 95 amps straight up or over an hour?
I’ve read somewhere that the resistance, temperature and state of charge of the battery limits the current.

Now my point is this, if the alternator can produce this kind of power why would I need to upgrade the cables etc. to charge a lithium battery that wants to take everything I could throw at it,
Or is it to maybe protect the lithium battery itself from too much charging current hence the need to limit the current?

One for the auto electricians.
Click to expand...

It is vitally important that customers understand you cannot charge a lithium battery from an alternator unless it is specialised and regulated properly. This includes via a split charge relay from the start battery. The lack of resistance to charge in the lithium means the alternator can fly free if connected directly to a bank containing a lithium, producing too much current and getting too hot, especially at idling revs which reduces the cooling effect of the alternator fan. This will burn out the alternator
or worse.
Our Lithium can only be charged safely using either a mains charger or battery to battery charger with suitable voltage and amps settings within the range described on our specification sheet. I cannot be connected directly or indirectly to alternator output charging. I imagine it is the same for all lithiums.

Subscribers  do not see these advertisements

 
  • Thanks
Reactions: DBK
weejocky said:
So what is the point of this thread :doh:
Click to expand...
They are offering advice and a wealth of knowledge to help Funsters.
They are absolutely not, trying to divert people to the Battery Megastore for their cheap deals on batteries or chargers!

It would be like me doing a review (Test) on a Bailey motorhome and at the end mentioning I have a cheap one for sale!
 
BatteryMegaUK said:
Our Lithium can only be charged safely using either a mains charger or battery to battery charger with suitable voltage and amps settings within the range described on our specification sheet. I cannot be connected directly or indirectly to alternator output charging. I imagine it is the same for all lithiums.
Click to expand...

So, in light of this last post, what on earth is the point of the first post.
 
Thank you some sensible advice, time to get the torch, multimeter and callipers out.
When I was considering the lithium root I was going to disconnect the charging setup from the nordelectronica anyway as their considered to be delicate electrically and charge straight from the start battery via the appropriate gizmos.
Our battery power consumption is pretty low so the solar should be adequate enough to charge a lithium battery, I bought the Votronic controller for the future proof lithium setting. We could probably go 5 days on 100Ah lithium if needed. I don’t use the mains battery charger since going solar.

 
I recently purchased one of those small "Battery Banks" which allegedly will start a Big Diesel (not tried it, Yet). But it did boost off my Fiat Punto. I was pleasantly surprised. I assume it too has Li-Ion/Li-Po cells. I am not opening it up just to find out!. It charges via a USB connection from any usb source. I wanted it to back up my Laptop in "on site" or "off grid" situations where no "mains" are available.

The Punto went "flat" after being unused for some time, it was connected using the supplied cables and it turned over after only a few seconds. So will it also boost the Merc; V6 Diesel?. Hopefully I won`t have to find out!.

Subscribers  do not see these advertisements

 
It won't start my Land Rover Td5.. tried it after I bought one. Waste of money..I think I've used it to charge the phone one weekend when I was off grid in a tent.. it's been sat in it's zip bag since then. probably flat and knackered by now :D
 
PeteH said:
I recently purchased one of those small "Battery Banks" which allegedly will start a Big Diesel (not tried it, Yet).
Click to expand...

I have one as listed below, it will start my 2.8 ltr Mitsubishi turbo diesel three times before it needs recharging. I've had it since 2017 and used it quite a few times, the only thing that's failed was the mains charger, but just bought another charger from ebay easy enough.

Amazon product ASIN B01BEZV0IA
 
What do you take from that?. At first glance, It would appear that fitting a Li-?? battery as "starter" would require extra protection?. Perhaps if using Li-?? batteries for Habitation, the "trick" would be to have them separate electrically and use (say) a B2B unit to charge them when on the move?.

Does that work?.
 
PeteH said:
What do you take from that?. At first glance, It would appear that fitting a Li-?? battery as "starter" would require extra protection?. Perhaps if using Li-?? batteries for Habitation, the "trick" would be to have them separate electrically and use (say) a B2B unit to charge them when on the move?.

Does that work?.
Click to expand...
It is one of the reasons I installed a B2B.

Subscribers  do not see these advertisements

 

Join us or log in to post a reply.

To join in you must be a member of MotorhomeFun

Join MotorhomeFun

Join us, it quick and easy!

Join us

Log in

Already a member? Log in here.

Latest journal entries

Back
Top