Charge cycles

[Colvic Watson]

I've just bought a lead acid battery that says it's good for a minimum of 150 charge cycles. I thought it was the discharge cycle that affected performance? So am I right in thinking that a large number of small charge cycles does very little harm to a battery - say discharging no more than 15% and then recharging?

 

[VicS]

I've just bought a lead acid battery that says it's good for a minimum of 150 charge cycles. I thought it was the discharge cycle that affected performance? So am I right in thinking that a large number of small charge cycles does very little harm to a battery - say discharging no more than 15% and then recharging?

I think by "charge cycles" they mean discharge and recharge but I would have expected the depth of discharge to have been specified.
Normally I think 50% including leisure batteries but 70% for deep cycle batteries.

What sort of battery?

 

[Plevier]

100 10% cycles will do less damage than 10 100% cycles if that answers your question - but not no damage.

 

[Mistroma]

I've just bought a lead acid battery that says it's good for a minimum of 150 charge cycles. I thought it was the discharge cycle that affected performance? So am I right in thinking that a large number of small charge cycles does very little harm to a battery - say discharging no more than 15% and then recharging?

Correct, you will get many more discharge/charge cycles from a battery when only discharging 15% vs. 50%. However, that doesn't make it the best option financially. You'd need to do some calculations but accurate information often seems to be hard to come by for a specific battery. Perhaps battery mfrs. don't want people to compare easily on like for like basis.

Taking some approx. figures (with lots of guesswork):

100Ah battery discharged 50% gives at least 150 cycles.
So usable Ah is around 7,500Ah (50x150)

Same battery discharged 15% might give 500 cycles.
So usable Ah is still around 7,500Ah (15x500)

But of course you need to buy a batteries to supply 333Ah to get same Ah out each day if only using 15%.

Sounds reasonable so far but:
1) Figures are guesswork and I suspect they are optimistic (i.e. More likely to get only 300-400 cycles instead of 500). So only getting 60%-80% of 7,500Ah quoted.

2) Flooded batteries are slow to charge from 80% to 100% so you are unlikely to keep batteries at 100% even if only using a small amount of power each day.

It all gets complicated once you start looking at charging regimes, usage profiles, different battery types. I guess that's why there are so many threads on the subject.


PS I'm considering new batteries as well. 6V Trojan units would be fine BUT they are 2mm too big for the compartment. Typical.

 

[Conachair]

Trojan L16RE-2V

 

[Colvic Watson]

Thanks, that's very helpful. We are marina based so keeping them near 100% is easy but clearly recharging them little and often when cruising is better than fewer big chargers.

 

[Plevier]

Trojan L16RE-2V

That graph really surprises me.
Assume a 100Ah battery for simplicity. The graph says that at 20% discharge i.e. 20Ah you will get 4000 cycles which is a total delivery of 80,000Ah over the battery's life.
At 40% i.e. 40Ah you will get 2000 cycles - 80,000Ah over the battery's life.
At 80%, 1000 cycles - 80,000Ah.
At 100%, 800 cycles - 80,000Ah.
According to this the depth of discharge makes no difference to the total delivered Ah over the life of the battery.
It contradicts my previous post and much as I respect Trojan's reputation, it goes against my considerable experience in the battery industry and it would take a lot of evidence to convince me it's right.
I do find 800 cycles at 100% depth pretty ambitious for a flat plate battery as well.
I shall do some digging.

Doesn't alter the fact that you should always keep as near fully charged as possible!