Leaving battery in storage

[Gozza2]

Hi again all

I know that what I'm about to ask is a "how long is a piece of string" question, but I'm just looking for some rule of thumb guidance.

On our storage site there's no mains, and I don't currently have any solar or other top-up facility...so...

Assuming I get back to the storage site with a fully topped up battery, and assuming the battery is middle-range quality and reasonably new, how long should I expect it to be safe to leave the battery in the 'van rather than bringing it home and putting it on float charge? By "safe" I mean, it won't self-discharge to the point that the battery loses capacity / is ruined.

For the purposes of some "back of cigarette packet" calculations, assume an 85 Ah battery and no load while in storage.

 

[Damian]

Battery self discharge rate varies based on the chemistry type used and the temperature the battery is at: higher temperatures increase the self-discharge rate. This explains why batteries left inside cars on hot days must be recharged more frequently!

Battery self-discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery. Battery self-discharges does decrease the overall shelf-life of batteries and causes them to initially have less than a full charge when actually put to use.

Here are average self discharge rates for the following chemistries:

	NiCd	NiMH	Lead Acid	Li-ion	Li-ion polymer	Reusable Alkaline
Self-discharge / Month (room temperature)	20%	30%	5%	10%	~10%	0.3%

The rate at which batteries self discharge depends on the type of battery, state of charge, charging current, ambient temperature and other factors. Lithium based batteries suffer the least amount of self-discharge (around 2–3% discharge per month), while nickel-based batteries are more seriously affected by the self-discharge rate.

To reduce the rate of battery self discharge during storage then store the battery at lower temperatures to reduce the rate of self-discharge and preserves the initial energy stored in the battery.

 

[Gozza2]

This is brilliant Damian, just the kind of detail I was looking for, thanks.

 

[RogerL]

Ordinary lead-acid batteries are best not discharged below 50% as doing that repeatedly shortens their lives but that still gives up to 10 months without attention - car accessory shops usually have signage to recharge batteries every 3 months while unused.

 

[JezzerB]

I didn't leave our cars longer than a couple of weeks over winter uncharged-and with the van it can be cold which makes matters worse so we bought a little 10w solar panel and croc clips-put it in the roof light held in place by the blinds-just pull them across enough so it sits on them-and leave it on trickle charge-no controller needed with a teeny panel. Alternatively optimate will sell you a kit.

 

[Raywood]

We have our battery connected to a low wattage solar panel which has been enough to keep it charged. As I have a 110 watt battery I am not keen on removing it.

 

[otherclive]

We have our battery connected to a low wattage solar panel which has been enough to keep it charged. As I have a 110 watt battery I am not keen on removing it.

Do you connect the solar panel clips to the battery cables in the van rather than route them through another penetration in the battery box.

 

[Gozza2]

I've been thinking about solar, which is partly what guided my original question. I have a history of forgetting to look after the battery when the 'van isn't in use, leading to the battery becoming useless and a replacement being needed. JezzerB's solution looks like what I had in mind, but I'll want to find somewhere within the van that I can connect straight to the unswitched battery cables (via a fuse, obv. !), rather than penetrate the battery compartment.

I'm not keen on spending masses on a solar panel, as it'll only be for in-storage battery maintenance, but of course at the same time I don't want to spend money on a cheap 'n nasty panel from a dodgy online retailer, that won't do the job.

 

[Beehpee]

I seem to remember seeing solar panels for sale at Aldi, I’ve no idea of output or type but you can be pretty sure it’s gonna be cheaper than anywhere else, I have an idea my niece bought one and it’s kept her battery charged ok, on a similar topic my GT70 has a solar panel on the roof that came with the van when new, previous owner said he’s not needed to charge the battery since he bought it, it’s got a controller but solar is all a bit of a mystery to me, anyone any idea what size the panel was likely fitted by bailey and what it’s likely to power.
Apologies if I’m changing OP’s topic.

BP

 

[JezzerB]

I've been thinking about solar, which is partly what guided my original question. I have a history of forgetting to look after the battery when the 'van isn't in use, leading to the battery becoming useless and a replacement being needed. JezzerB's solution looEks like what I had in mind, but I'll want to find somewhere within the van that I can connect straight to the unswitched battery cables (via a fuse, obv. !), rather than penetrate the battery compartment.

I'm not keen on spending masses on a solar panel, as it'll only be for in-storage battery maintenance, but of course at the same time I don't want to spend money on a cheap 'n nasty panel from a dodgy online retailer, that won't do the job.

Ours was a cheap and nasty eBay tenner p urchase. Worked beautifully for the 4 years we didn't have a van with solar and as you say direct to battery. First can we left it outside too propped up on a frame.