Battery cycling?

[weldted]

What constitutes a cycle in a battery, makers quote good for X cycles? If you are not using the van buthave solar panels which top up the battery then overnight there is a small discharge from the alarm/immobiliser all be it from the engine battery which my system also tops up. In the summer use tv etc during the evening which my panels (300 watt) have topped up by around 10:30 am depending on the weather. In the winter chances are if not driving or on ehu the panels may lose the battle to fully recharge each day. But will fully charge if say van driven on third day using the system I have previously posted about. Just wondered how it is calculated.

[StuartO]

Shallow cycling is said to be less wearing (on a battery's service life) than deep cycling and I believe that reputable estimates therefore assume discharge to a worthwhile (but not a very deep) extent.  Individual variation in the burden which we motorhomers place on to our leisure batteries is going to be a big factor in service life, so I doubt that predictions of service life are going to be much use.  Now that we know that the number of cycles a given battery will deliver are not reliably tested, so that the NCC and manufacturers' figures are not necessarily to be trusted, it's all a bit of a guessing game.

But batterries are consumable items and compared with the overall costs of motorhoming, they are not expensive.  Accepted wisdom at the moment seems to be that Varta LFDs are pretty good (and they are guaranteed for five years) but there might be better on the way (eg from Yaesu) but we should certainly think twice before buying any really cheap ones, which are likely to be Far East rubbish.

[aandncaravan]

Stuart is spot on.

 

A battery rated at 200 cycles when discharged down to 50% Depth Of Discharge (DOD) will probably achieve over 1,000 cycles at a shallower 20% DOD or 2,000+ cycles at an idle vehicles 'overnight' discharge and Solar charge of extremely shallow 0.5% DOD.

 

Leisure Batteries in the UK are tested by the big battery companies to BS EN 50342 and we have see those test results for the big companies.

The standard requires the battery to be discharged to 50% Depth Of Discharge and only the usable cycles that deliver greater than 80% capacity are counted.

The standard regards a battery that can no longer deliver at least 80% of the rated capacity on the label, as exhausted (e.g. 80Ah out of it's 100Ah would be an exhausted battery).

 

A battery loses a little bit of it's capacity each time it is used, so often reaches the 'exhausted' state long before it develops a fault like shorted cells, etc.

Obviously the battery may go on working 'well' after this point, therefore a battery rated using this standard may last significantly longer than the cyclic figure suggests. Hence batteries, like the YUASA L36-EFB potentially performing better than the paper spec suggests in real use.

This battery BS EN tested at 230+ cycles, but Yuasa quote 200 cycles, again showing how a big name battery will perform better in real world use.

 

The lesser battery companies have a reputation of 'overstating' the number of cycles, like quoting 100 when the reality is only 85.

 

Not all companies use the same standard, we have paperwork from an Asian company that tested a batteries cyclic ability by counting the cycles right down to the batteries 50% Capacity, not the BS EN standard's 80%.

If the general guide is that you don't discharge a battery below 50% DOD, effectively always leaving 50% behind, then leaving 50% behind on a battery that only has 52% capacity left (i.e. 52Ah of a 100Ah battery) gives a cycle of 2%/2Ah Capacity!!!

 

Unbelievably, we have a document that was used by the NCC to 'verify' an Asian manufactured battery that counted all cycles right down to 50% usable capacity. In real use this means you probably won't achieve half the 'verified' cyclic ability.

The Asian battery in question was claimed by the manufacturer to deliver 220 cycles and that was accepted by the NCC and used to 'verify' the battery. However, using the BS EN standard it shouldn't have been rated at 160 cycles.

 

When the same battery was actually tested at BS EN 50342, it achieved a miserable 71 cycles real cycles, suggesting that the manufacturer either employs Han Anderson to write out the battery test figures or their test only discharged to 25% DOD.

 

So you are right Weldted, not all cycles are the same. We have seen BS EN battery test data for the big manufacturers, but not from the Far East to back up the figures.

 

 

Speaking over the weekend we were again told by someone of 'high regard' that the NCC's own 'standard' of just testing a battery for 6 cycles and then 'estimating' that it will reach the manufacturers cycle rating 'encourages' the less scrupulous manufacturers to quote inflated figures.

 

 

Like Stuart suggests stick with a name like Banner, Varta, Yuasa or Exide until the NCC start publishing real test data to prove ALL the batteries really do what is claimed.

 

We have now seen inside a Yuasa L36-EFB Leisure/Starter battery and it is everything the manufacturer says and more. It takes over from the Varta LFD90 as our best 'Best Value Buy'.

 

[weldted]

Many thanks, 2 Yuasa L36-EFB's it is then.