Battery maths help please

Tookey

Tookey

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I have installed a Leoch 12v 108Ah battery. I am trying to work out what its 80% DoD is but every website I visit immediately starts talking about amps which is fine but I will be keeping an eye on the voltmeter so amps don't help.

Can you tell me what me 80% DoD will be in volts?

If you can be bothered could you please show your workings?

Thank you
 
Does this help?
 

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Tookey said:
I have installed a Leoch 12v 108Ah battery. I am trying to work out what its 80% DoD is but every website I visit immediately starts talking about amps which is fine but I will be keeping an eye on the voltmeter so amps don't help.

Can you tell me what me 80% DoD will be in volts?

If you can be bothered could you please show your workings?

Thank you
Click to expand...

Are we talking about a lead acid battery here. If so your minimum voltage at 50% max DOD would be 12v. If it’s lithium then the voltage should remain about the same at 80% dod. a lead acid at 80% dod would be reading about 10.9 volts, but you would be damaging your lead acid battery. If you are struggling for amperage a second battery of the same make and amperage would be your best option.
 
Fisherman said:
Are we talking about a lead acid battery here. If so your minimum voltage at 50% max DOD would be 12v. If it’s lithium then the voltage should remain about the same at 80% dod. a lead acid at 80% dod woukd be reading about 10.9 volts, but you would be damaging your lead acid battery.
Click to expand...
Lead carbon
 
Failure modes of flat plate VRLA lead acid batteries in case of intensive cycling
The most common failure modes are:
- Softening or shedding of the active material. During discharge the lead oxide (PbO2) of the positive plate is transformed into lead
sulfate (PbSO4), and back to lead oxide during charging. Frequent cycling will reduce cohesion of the positive plate material due to the
higher volume of lead sulfate compared to lead oxide.
- Corrosion of the grid of the positive plate. This corrosion reaction accelerates at the end of the charge process due to the, necessary,
presence of sulfuric acid.
- Sulfation of the active material of the negative plate. During discharge the lead (Pb) of the negative plate is also transformed into lead
sulfate (PbSO4). When left in a low state-of-charge, the lead sulfate crystals on the negative plate grow and harden and form and impenetrable layer that cannot be reconverted into active material. The result is decreasing capacity, until the battery becomes useless.
It takes time to recharge a lead acid battery
Ideally, a lead acid battery should be charged a rate not exceeding 0,2C, and the bulk charge phase should be followed by eight hours of absorption charge. Increasing charge current and charge voltage will shorten recharge time at the expense of reduced service life due to temperature increase and faster corrosion of the positive plate due to the higher charge voltage.
Lead carbon: better partial state-of-charge performance, more cycles, and higher efficiency
Replacing the active material of the negative plate by a lead carbon composite potentially reduces sulfation and improves charge acceptance of the negative plate.
The advantages of lead carbon therefore are:
- Less sulfation in case of partial state-of-charge operation.
- Lower charge voltage and therefore higher efficiency and less corrosion of the positive plate. - And the overall result is improved cycle life.
Tests have shown that our lead carbon batteries do withstand at least five hundred 100% DoD cycles.
The tests consist of a daily discharge to 10,8V with I = 0,2C20, followed by approximately two hours rest in discharged condition, and then a recharge with I = 0,2C20.
(Several manufacturers of lead carbon batteries claim a cycle life of up to two thousand 90% DoD cycles. We have not yet been able to confirm these claims)
Recommended charge voltage
Specifications
Cycle life
V
12 12
≥ 500 cycles @ 100% DoD (discharge to 10,8V with I = 0,2C20, followed by approximately two hours rest in discharged condition
 
Fisherman said:
Failure modes of flat plate VRLA lead acid batteries in case of intensive cycling
The most common failure modes are:
- Softening or shedding of the active material. During discharge the lead oxide (PbO2) of the positive plate is transformed into lead
sulfate (PbSO4), and back to lead oxide during charging. Frequent cycling will reduce cohesion of the positive plate material due to the
higher volume of lead sulfate compared to lead oxide.
- Corrosion of the grid of the positive plate. This corrosion reaction accelerates at the end of the charge process due to the, necessary,
presence of sulfuric acid.
- Sulfation of the active material of the negative plate. During discharge the lead (Pb) of the negative plate is also transformed into lead
sulfate (PbSO4). When left in a low state-of-charge, the lead sulfate crystals on the negative plate grow and harden and form and impenetrable layer that cannot be reconverted into active material. The result is decreasing capacity, until the battery becomes useless.
It takes time to recharge a lead acid battery
Ideally, a lead acid battery should be charged a rate not exceeding 0,2C, and the bulk charge phase should be followed by eight hours of absorption charge. Increasing charge current and charge voltage will shorten recharge time at the expense of reduced service life due to temperature increase and faster corrosion of the positive plate due to the higher charge voltage.
Lead carbon: better partial state-of-charge performance, more cycles, and higher efficiency
Replacing the active material of the negative plate by a lead carbon composite potentially reduces sulfation and improves charge acceptance of the negative plate.
The advantages of lead carbon therefore are:
- Less sulfation in case of partial state-of-charge operation.
- Lower charge voltage and therefore higher efficiency and less corrosion of the positive plate. - And the overall result is improved cycle life.
Tests have shown that our lead carbon batteries do withstand at least five hundred 100% DoD cycles.
The tests consist of a daily discharge to 10,8V with I = 0,2C20, followed by approximately two hours rest in discharged condition, and then a recharge with I = 0,2C20.
(Several manufacturers of lead carbon batteries claim a cycle life of up to two thousand 90% DoD cycles. We have not yet been able to confirm these claims)
Recommended charge voltage
Specifications
Cycle life
V
12 12
≥ 500 cycles @ 100% DoD (discharge to 10,8V with I = 0,2C20, followed by approximately two hours rest in discharged condition
Click to expand...
Those advantages of Lead Carbon is why David (wildebus) recommended as it is very likely my battery is basically going to be abused rather than cared for
 
Fisherman said:
Failure modes of flat plate VRLA lead acid batteries in case of intensive cycling
The most common failure modes are:
- Softening or shedding of the active material. During discharge the lead oxide (PbO2) of the positive plate is transformed into lead
sulfate (PbSO4), and back to lead oxide during charging. Frequent cycling will reduce cohesion of the positive plate material due to the
higher volume of lead sulfate compared to lead oxide.
- Corrosion of the grid of the positive plate. This corrosion reaction accelerates at the end of the charge process due to the, necessary,
presence of sulfuric acid.
- Sulfation of the active material of the negative plate. During discharge the lead (Pb) of the negative plate is also transformed into lead
sulfate (PbSO4). When left in a low state-of-charge, the lead sulfate crystals on the negative plate grow and harden and form and impenetrable layer that cannot be reconverted into active material. The result is decreasing capacity, until the battery becomes useless.
It takes time to recharge a lead acid battery
Ideally, a lead acid battery should be charged a rate not exceeding 0,2C, and the bulk charge phase should be followed by eight hours of absorption charge. Increasing charge current and charge voltage will shorten recharge time at the expense of reduced service life due to temperature increase and faster corrosion of the positive plate due to the higher charge voltage.
Lead carbon: better partial state-of-charge performance, more cycles, and higher efficiency
Replacing the active material of the negative plate by a lead carbon composite potentially reduces sulfation and improves charge acceptance of the negative plate.
The advantages of lead carbon therefore are:
- Less sulfation in case of partial state-of-charge operation.
- Lower charge voltage and therefore higher efficiency and less corrosion of the positive plate. - And the overall result is improved cycle life.
Tests have shown that our lead carbon batteries do withstand at least five hundred 100% DoD cycles.
The tests consist of a daily discharge to 10,8V with I = 0,2C20, followed by approximately two hours rest in discharged condition, and then a recharge with I = 0,2C20.
(Several manufacturers of lead carbon batteries claim a cycle life of up to two thousand 90% DoD cycles. We have not yet been able to confirm these claims)
Recommended charge voltage
Specifications
Cycle life
V
12 12
≥ 500 cycles @ 100% DoD (discharge to 10,8V with I = 0,2C20, followed by approximately two hours rest in discharged condition
Click to expand...
So 10.8V is 100% but what I am trying to identify is 80% as this seems like a happy medium between abuse and care.

So is the useful table posted by mjvw not applicable?
 
Tookey said:
Those advantages of Lead Carbon is why David (wildebus) recommended as it is very likely my battery is basically going to be abused rather than cared for
Click to expand...
The information I posted suggests a min voltage of 10.8v.
You would have to ensure that this falls within the latitude allowed by your 12v equipment. I would reckon that would be fine. Also they are recommending at least a 2 hour break before recharging. I would reckon on 11-11.1v for 80%.
Also I would recommend an mppt controller (victron preferably).
Also if you do go for victron David recommends the battery temperature monitor also. But knowing David he will be your best man for advice here.
 
Fisherman said:
The information I posted suggests a min voltage of 10.8v.
You would have to ensure that this falls within the latitude allowed by your 12v equipment. I would reckon that would be fine. Also they are recommending at least a 2 hour break before recharging. I would reckon on 11-11.1v for 80%.
Also I would recommend an mppt controller (victron preferably).
Also if you do go for victron David recommends the battery temperature monitor also. But knowing David he will be your best man for advice here.
Click to expand...
Thank you very much.

David has assisted and came up with a good idea incase I have a component failure outside of Europe, my two PV panels are independent and have a Victron 75/10 on each, two independent set ups so in the event of a panel/controller failure I am not left 'high n dry'
 
Fisherman said:
The information I posted suggests a min voltage of 10.8v.
You would have to ensure that this falls within the latitude allowed by your 12v equipment. I would reckon that would be fine. Also they are recommending at least a 2 hour break before recharging. I would reckon on 11-11.1v for 80%.
Also I would recommend an mppt controller (victron preferably).
Also if you do go for victron David recommends the battery temperature monitor also. But knowing David he will be your best man for advice here.
Click to expand...
Doesn't battery temperature monitoring apply more to Lithium?
 
I would also consider this, you only require one even if you have more than one battery. You Victron controller is not aware of battery temperature, and will adjust how it charges your battery according to temperature. The sensor communicates this information to the controller Via blutooth. This one has a 3m blutooth range. But they do one with a 10m range if required.
Yes you can damage lithium batteries below 5c, hence why some have internal heaters and blutooth connectivity to help prevent this.

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Tookey said:
I have installed a Leoch 12v 108Ah battery. I am trying to work out what its 80% DoD is but every website I visit immediately starts talking about amps which is fine but I will be keeping an eye on the voltmeter so amps don't help.

Can you tell me what me 80% DoD will be in volts?

If you can be bothered could you please show your workings?

Thank you
Click to expand...

This is not an easy question to answer as most charts reference an open circuit battery that has been rested and is at 21c.
If the battery is in-circuit or under load/charge the charts are useless.
A battery monitor is the best way to determine the state of charge as it counts the energy removed from the battery.
 
Obviously a proper system is best
But we just go on a simple volt meter.
We regard 12.5 as warning. But rarely below 12.6 even at night with gas heating in use (blower)
If you keep the vehicle warm then the blower is hardly used and so no big drain on the battery !
We manage fine !
 
In no particular order ....
The general advice about not going below 50% SoC for a Lead Acid battery does not apply to Lead Carbon battery. Sure you will reduce the charge cycle count and so likely service life, same as any battery (including Lithium), but you do not damage the battery.
A true Battery State of Charge monitor is the best way to know what your batteries state of charge actually is. As Phil says, when under load or under charge, the voltage shown has no direct relevance to the tables. You can get a 'feeling' for the battery level after a while, but it is a lot easier with a SOC monitor :)

Now in terms of a table, this is a table vs Ah discharge table I made from my own physical installation of 300Ah of Ritar Lead Carbon AGM Batteries - so the Leoch Lead Carbon AGM should be very similar. The current on this table was a fairly constant 1.x Amps so pretty minimal.
To find the voltage at a given DoD%, divide the Ah figure on the X axis by 300. The lowest DoD I have here is 71% (217 out of a 300Ah bank) but the line is pretty constant in its decline, so 80% DoD would mean a voltage of around 11.75V I would say
1620565122124.png
 
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"The general advice about not going below 50% SoC for a Lead Acid battery does not apply to Lead Carbon battery. Sure you will reduce the charge cycle count and so likely service life, same as any battery (including Lithium), but you do not damage the battery"

This is pure semantics surely. Why would you make a distinction between non-existent actual physical damage to the battery (and I doubt that assertion that there is none anyway) and damage to one's bank balance because the battery is going to fail sooner than it otherwise would have if that non-existent damage hadn't occurred.
 
I don't agree.
The deeper you take a battery, the less charge cycles you have - that is a generally accepted situation with any battery.
But if you are operating it within its service parameters you are not chasing damage to it and it will recharge correctly.

If you take it below its service parameters you are risking and likely damaging the actual working operation of the battery far more than just reducing its service life.

Whether you agree or not is your choice.
 
Tony Lee said:
"The general advice about not going below 50% SoC for a Lead Acid battery does not apply to Lead Carbon battery. Sure you will reduce the charge cycle count and so likely service life, same as any battery (including Lithium), but you do not damage the battery"

This is pure semantics surely. Why would you make a distinction between non-existent actual physical damage to the battery (and I doubt that assertion that there is none anyway) and damage to one's bank balance because the battery is going to fail sooner than it otherwise would have if that non-existent damage hadn't occurred.
Click to expand...

With regards to making a distinction between no physical damage and lifespan this actual battery's requirement is not to last many years and thousands of cycles but rather potentially high levels of discharge over a 12 month period where preventing inefficiency (no physical damage) during this and only this period is the priority rather than total lifespan.

I don't know enough about batteries to know whether the above is relevant to your point but that is it's intended use which Wildebus is aware of.
 
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