SLA Charging Question

[Capn_Phil68]

Hi,

Thanks for calling in.

I'm a bit confused about recharge limits.

My bike, a chinese MBT, states that the battery pack is good for around 300 charges.

Does this mean 300 full charges or 300 part charges or on a ratio basis e.g. 600 half charges.



TIA

Phil

 

[flecc]

With battery types in general, it's taken to mean full charges.

However, these numbers of charges are very imprecise, not very much better than guesses, the life of any battery determined by a large range of factors.

One example I often quote is that of Li-ion, said to be 500 charges. Perfectly standard examples of these are used in satellites, where they last for up to ten years and receiving over 3600 charges.

Likewise, Jeremy has quoted the example of the Toyota Prius NiMh batteries, nominally good for 400 charges, but guaranteed to take 8000 charges on the Prius.

So you can see how hugely variable this can be. The numbers can reduce as well of course, and some of us have been complaining of this with some particular battery types.
.

 

[Jeremy]

Likewise, Jeremy has quoted the example of the Toyota Prius NiMh batteries, nominally good for 400 charges, but guaranteed to take 8000 charges on the Prius.

I have a feeling that the Prius cells are good for much more than that, mine is now three years old and has probably partially cycled the cells around 30,000 to 40,000 times as far as I can tell. Watching the power flow display in the car, it's clear that the batteries get partially discharged and charged every mile or so in normal driving, depending on the terrain. It's quite common to see the power flow reversing every few yards in stop/start traffic and equally common to get continuous heavy discharge going up hills and heavy charge coming back down them. They have an 8 year or 100,000 mile warranty, which implies that they are good for at least 100,000 cycles, perhaps a lot more, although these will be quite shallow cycles.

Jeremy

 

[flecc]

Apologies for misquoting you Jeremy, 8000 charges in lieu of 8 years!
.

 

[Jeremy]

Understandable, Flecc, given that the number of cycles seems so extraordinarily high.

I must spend some time researching the relationship between charge/discharge depth and number of useful cycles for various battery types. It looks to me that the relationship is very non-linear for NiMH, with shallow charge/discharge cycles greatly extending battery life.

Jeremy

 

[flecc]

Yes, it does seem that way. In contrast, the satellite example with Li-ion is of approximately 3500 charges of one seventh of the capacity used each 24 hours, so amounting to 500 full charges, very linear.

I've no idea with lead acid.
.

 

[pete22]

From: Can the lead-acid battery compete in modern times? BatteryUniversity.com

" Lead-acid does not like deep cycling. A full discharge causes extra strain and each cycle robs the battery of some service life. This wear-down characteristic also applies to other battery chemistries in varying degrees. To prevent the battery from being stressed through repetitive deep discharge, a larger battery is recommended. Lead-acid is inexpensive but the operational costs can be higher than a nickel-based system if repetitive full cycles are required.

Depending on the depth of discharge and operating temperature, the sealed lead-acid provides 200 to 300 discharge/charge cycles. The primary reason for its relatively short cycle life is grid corrosion of the positive electrode, depletion of the active material and expansion of the positive plates. These changes are most prevalent at higher operating temperatures. Cycling does not prevent or reverse the trend."