12v emergency start battery as power supply

[KAM]

Not strictly boaty. I need a small 12v supply to run led lights and a water pump. A lead acid battery seems a bit big and clumsy. I was wondering about using one of the small lithium 12v emergency starter batteries now widely advertised. Would the recharge speed be too slow to be practicable. Has anyone used these in this type of application.

 

[Refueler]

It may surprise you - but many of those Lithium Starter packs are not so big on capacity as they try to kid you. But they are designed to throw out huge amps to kick an engine over ... but only in very short bursts.
As to run less demanding gear - yes they will of course - battery doesn't care ... but do not expect long output ...

If you are looking to run lights / a water pump - then I would look at SLA or other types of Lithium (SLA = Sealed Lead Acid .... basically same as house alarm battery ... you can get them up to good capacity). Or a smaller Lead Acid for a Lawn Tractor or similar ... they are quite compact.

 

[B27]

I run an irrigation pump from an old motorbike battery. It's a small system.
Battery pack for cordless drill?

Starting point is knowing how many Ah you want.

 

[Refueler]

I run an irrigation pump from an old motorbike battery. It's a small system.
Battery pack for cordless drill?

Starting point is knowing how many Ah you want.

Exactly ... know how much power you need - then more than double it to avoid destroying the battery by over discharge.

 

[KAM]

30Ah should do. Was looking for a cheap leisure battery around this size but doesent seem to be available.

 

[KAM]

Had wondered about a 12v drill battery pack but it would need a thermistor and some work on interfacing for charging.

 

[Kelpie]

I use a small lithium jump start device as a handy portable 12v supply. Runs my digital piano without fear of voltage spikes, and I get several hours out of it.
It's essentially a big version of those power banks you can use for charging your phone etc. From memory it's 12Ah at 3.7v, so very small compared to similar any lead acid battery.

 

[William_H]

Nigel will tell to look for a motor dismantler to get old car batteries. This would be the cheapest option. SLA batteries can come in almost any AH size you want. I have 40AH SLA in mobility scooter. (dinghy tractor) about 100 squid here. Search 12v SLA | Jaycar Electronics
I use a bundle of lithium 18650 cells for the boat battery. 3 cells in series makes 11.5 to 12v and they are about 4AH each cell so 3 banks in parallel gives my 12AH. I use a simple charge controller board to manage charge and discharge. it is very light weight and easy to take home for charge. ol'will

 

[Refueler]

Nigel will tell to look for a motor dismantler to get old car batteries. This would be the cheapest option. SLA batteries can come in almost any AH size you want. I have 40AH SLA in mobility scooter. (dinghy tractor) about 100 squid here. Search 12v SLA | Jaycar Electronics
I use a bundle of lithium 18650 cells for the boat battery. 3 cells in series makes 11.5 to 12v and they are about 4AH each cell so 3 banks in parallel gives my 12AH. I use a simple charge controller board to manage charge and discharge. it is very light weight and easy to take home for charge. ol'will

Guy wants small ... so the Scrap yard battery is not really an option ... but if size is no problem - then yes ... why not ? Just because a cars scrapped does not mean battery is scrap ...

I mentioned SLA as you say - they come in small to quite large capacity ... but they are not designed to deliver high amps ... but perfect for low power work.

18650 ? care needs to be taken here as the 18650 name actually is the physical size of the cell ... so high capacity means lower amp delivery - its a trade off - same as with NiMh ... low capacity = high amp ... large capacity = lower amp ... its the physical construction that dictates that.
Charging such 18650 - which are LiIon - is simple with a 3S balance based charger ... available at under a tenner. But of course - person needs to either get a holder for the cells or spot weld them as a pack ...
18650 also come in two voltages ... 3.3 or 3.6 nominal ..... so the 3.6v is the preferred for this as the full charge value is then 4.2v .... 3x 4.2v = the decent value for 12v applications. The 3.3v version is not enough ...

 

[PaulRainbow]

I mentioned SLA as you say - they come in small to quite large capacity ... but they are not designed to deliver high amps ... but perfect for low power work.

SLA can deliver high amps, well over 1000CCA for bigger batteries.

 

[KAM]

Might go for SLA presumably they don't need any sophisticated charge circuit. Was thinking of using a standard VSR in a dual battery set up.

 

[PaulRainbow]

Might go for SLA presumably they don't need any sophisticated charge circuit. Was thinking of using a standard VSR in a dual battery set up.

Absolutely fine. SLA stands for Sealed Lead Acid, nothing special.

 

[Refueler]

SLA can deliver high amps, well over 1000CCA for bigger batteries.

I was referring to the sealed batterys typically used as house alarm batterys .... not the No Maintenance Sealed Crankers ...

You KNEW that ...

 

[PaulRainbow]

I was referring to the sealed batterys typically used as house alarm batterys .... not the No Maintenance Sealed Crankers ...

You KNEW that ...

My crystal ball is at the menders, so no, i didn't know what you meant.

 

[Refueler]

My crystal ball is at the menders, so no, i didn't know what you meant.

That I definitely do not believe as you prowl my posts looking for any to have a stab at ... go back a few posts and I specifically mentioned house alarm SLA's ....
Post #2 if you've forgotten.

Yet another example.

 

[KAM]

I used small SLAs many years ago and seem to remember having to use a special charger not a car charger but maybe car chargers have moved on since then.

 

[PaulRainbow]

That I definitely do not believe as you prowl my posts looking for any to have a stab at ... go back a few posts and I specifically mentioned house alarm SLA's ....
Post #2 if you've forgotten.

Yet another example.

In a single sentence you talk about SLA, Lithium, something "basically the same as house alarm batteries" and lawn tractor batteries.

SLA cover any thing that contains lead/acid and is sealed. To say that SLA cannot deliver high amps is therefore not appropriate or correct as a blanket statement.

 

[PaulRainbow]

I used small SLAs many years ago and seem to remember having to use a special charger not a car charger but maybe car chargers have moved on since then.

You need to be clear what you mean by "SLA".

 

[KAM]

This sort of thing.

 

[Refueler]

This sort of thing.View attachment 163593

Yes Paul ...... this sort of battery.

SLA may be a generic term - but it is this form of battery that most people think of when SLA term is used ...