Batteries again :(

SquirrellCook

SquirrellCook

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I know this a common subject, but I'm trying to make sense of so many contradictory sources of information.
The one that seems to be most misleading is the battery's cyclic ability. It seems that there is some European body that covers this and states that the cyclic numbers counted should only to be when it reaches 80% of it's original capacity.
I expect anyone who has any interest in this subject knows with every charge discharge cycle the battery capacity is reduced. The deeper the discharge the greater the loss.
As the battery degrades with time any ways, it's not necessarily true that very small discharge will give the best value for money. I've not found the results of a study like this.
The NCC grading looks interesting, but when you look harder the numbers are too neat and are generally the same as the manufactures (sales team) have quoted. So you can't trust that.
Even acceptable maximum discharge voltages change when you look deeper. Some even claiming it's fine with a lead acid to go below 12 volts.
Discharge voltages are misleading too, the higher load the lower the voltage. Then you have to wait for the battery to recover off load to see how deep you discharged it.
Next week I'll attempt to contact some manufactures to find out if their cyclic numbers comply with this European rule.
One of them will be trojan as they claim their wet batteries cycle into a thousand plus! Mind you they are from the US and that says a lot!

I know everyone has an opinion based on personal experience, but sorry unless you've done a lot of back to back testing under controlled conditions your opinion doesn't count. If you have, your life must lack joy.
 
Don’t forget the term lead acid cover just about all battery types except Lithium and the like. You can totally discharge some lead acid battery’s many times but I doubt very much that any of that type are in any of our motorhomes.

There is no magic answer, you need to work out what power you will actually use, if then using lead acid you need two to three times that amount minimum spread across multiple battery’s and the means to charge them. lead Acid will also rarely get much over 80% charge unless you use hookup/generator or constant long runs as the charger setting will throttle back at 80%.

Low power users are okay but if you use a lot it’s a minefield.
 
Soon manufacturers won't have to worry about euro standards and will be able to quote anything they like!
But as now we'll just have to dig a little deeper and ask awkward questions.
 
Markd said:
Soon manufacturers won't have to worry about euro standards and will be able to quote anything they like!
But as now we'll just have to dig a little deeper and ask awkward questions.
Click to expand...
Very unlikely.
 
Meant to be a joke about the "lion being unleashed" 😀
I'd like to think everyone will be responsible but we may get stuff from anywhere that will only need to match whatever "standard" they choose to use.
 
Batteries are a bit of a minefield for sure.
I have little confidence in the NCC scheme as it is just a system that requires Battery makers to report their numbers for a certain spec and I don't believe there is any independant testing carried out by "NCC". It is the same as most schemes in that respect, so nothing surprising there.

Allowing a battery to go below 12V? well, there are two aspects to that. One is going below 12V under load and the other is going under 12V without a load (which would be an indication of the level of discharge). The Former is not unusual at all, but the later is usually not recommended as it will hurt the service life of a battery (and that is true of all batteries, including those that permit 100% discharge AND including Lithium Batteries).
And this effect of the Battery Voltage not being an indication of Battery Level is why a proper Battery Monitor is so useful on an installation that uses battery power relatively intensely or if there are any mission critical (CPAP?) requirements.

Decent Batteries tend to come with clear information on what happens to the batteries when they are discharged in different ways. That to me says the makers of those batteries know what they are doing if they are able to provide that information. And those are the ones to purchase.
Some Batteries sold don't even come with information on what voltages they should be charged to and floated at. Those are to be avoided IMO.

Example of a high performance battery is the Victron Super Cycle AGM, which is one of those batteries that CAN be 100% discharged without damage. But it does not mean doing that is not hurting the battery, and Victron don't hide that in their battery information. For Example from Victron
​
Cycle life​

  • ≥ 300 cycles @ 100% DoD (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)
  • ≥ 700 cycles @ 60% DoD (discharge during three hours with I = 0,2C₂₀, immediately followed by recharge at I = 0,2C₂₀)
  • ≥ 1000 cycles @ 40% DoD (discharge during two hours with I = 0,2C₂₀, immediately followed by recharge at I = 0,2C₂
So yes, you can take the battery down to 100% DoD, but do that on a regular basis and you will get 1/3rd of the life from the battery. Where these kind of batteries are very handy is when you normally don't need to draw that much energy but are sometimes "caught short". In those circumstances, an occasional 100% DoD will not reduce the service life notably (as long as battery is recharged as noted above)

But ALL batteries - INCLUDING Lithium - suffer like this to a more or lesser degree ... the more that is taken out the battery, the less overall cycles it will deliver in its service life. An example graph is below. But because Lithium starts off so much higher, many manufactuers will quote a life cycle based on a higher DoD as the number still looks so much better then Lead Acid which allows them to declare a high DoD as well.
battery-life-cycle-based-on-dod.jpg


Of course, the above represents my opinion. Others are quite free to have their own :)
 
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The ncc tests were found to be a load of clap trap,a independent test was done on batterys and bosch/varta silver power frame came out way better than al the so called les lead acid batteries.
Many of the so called les batteries were no more than car/truck units rebadged.
 
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