SLA/Li-ion Batteries?

[wood nacho]

Any battery experts out there?

I have a battery powered speaker system which is powered by a 12V lead-acid battery (7.5Ah). I am looking to increase the amount hours of use I can get out of the unit and I see there are a couple different options. I'm a little confused about each...

The speaker system has a 12vdc 2a charge port on the back. Meant to be used, say, with cigarette lighter port inside your car, or one of those battery boosters with a 12v out port. I'm wondering if I could use a Lithium-ion jump starter to charge the battery. I've been looking at this one...

https://www.primecables.ca/p-360792-...ecables_criteo

I understand that this unit is meant to jump start SLA batteries but what about charging them with the 12v out port? Can you charge an SLA battery with a lithium ion jump starter? A little confused here.

Another option....
If I were to increase the Ah by adding another SLA battery inside the unit (wired in parallel ofcourse) do I have to use the another battery with the same Ah? I am looking to keep the unit light-weight and adding another 7.5Ah battery is a lot of weight. Could I add a 4aH SLA battery in parallel? How does the depletion/charge of the batteries work if they are different Ah?

What would be the best way to add more Ah to this unit. Any help is appreciated! Thank you!

[fazool]

I'm not a battery "expert" but recently did a big engineering project on LiIon batteries (in coincidence with the Sony battery recall issue). I consulted with the world's most patented woman (world leading battery expert living in our town and taught at my grad school)



There is no quick answer - this is a detailed topic.

Short info is this:

You can never swap battery types. The charging circuits are specific to the battery types and have safe guards (over/under voltage and current and temp protections).

You can drain multiple lead-acid batteries safely in parallel because the load current draw hasn't changed. When you charge them in parallel you will draw more current from your charger so you will possibly overload the charging circuit.

[dannyg1]

“I'm wondering if I could use a Lithium-ion jump starter to charge the battery. I've been looking at this one...”

Possibly. It depends how the jump starter ‘sees’ the load of the SLA. One of the small, common, lithium jump packs probably won’t have the ah capacity to charge it much though.


“Another option....
If I were to increase the Ah by adding another SLA battery inside the unit (wired in parallel ofcourse) do I have to use the another battery with the same Ah? “

Yes, it must be the same so that pulling the larger one down to flat doesn’t reverse volt the existing battery (You’ll also have to balance charge the two cells). Depending on how the amp is wired, you may be able to plug a battery in through the AC charging port and the amp will see that as separate from the DC circuit and will run that battery down, independent of the internal battery, in which case you could plug any AH sized battery to that AC brick port and be fine running it. The AC line would be required to take 12v DC of course.

[Big Band Guitar]

Originally Posted by fazool

I'm not a battery "expert" but recently did a big engineering project on LiIon batteries (in coincidence with the Sony battery recall issue). I consulted with the world's most patented woman (world leading battery expert living in our town and taught at my grad school)



There is no quick answer - this is a detailed topic.

Short info is this:

You can never swap battery types. The charging circuits are specific to the battery types and have safe guards (over/under voltage and current and temp protections).

You can drain multiple lead-acid batteries safely in parallel because the load current draw hasn't changed. When you charge them in parallel you will draw more current from your charger so you will possibly overload the charging circuit.

This answer is correct. Having been involved somewhat in electric bus development.

Parallel lead acid of different ah are just fine. In series NO.

[Big Band Guitar]

I have done something like that on a battery powered amp that I built.

I have two batteries but switched so that only 1 is powering the amp while the other is charging. That doubled the run time without worrying about battery matching. It also isolates the amp from the charger and AC line.

My charger is a stand alone.

[dannyg1]

Parallel SLA’s of different ah are not fine:

http://batteryuniversity.com/learn/a...configurations

[Big Band Guitar]

Originally Posted by dannyg1

Parallel SLA’s of different ah are not fine:

http://batteryuniversity.com/learn/a...configurations

Lots of misinformation there about lead acid batteries.

[dannyg1]

As far as my experience sends me, battery university is the premier source for intensive information about every aspect of battery technology that there is on the internet. I’m interested to s e some of these instances of misinformation you’re referring to. How about you post a few please.

[dannyg1]

OP,

Listen to the info posted here carefully and read the posted links. Do your best research and play your music.

Be aware though that running a mismatched configuration that is lacking a fuse could run your smaller cell into a shorted condition and using it in this way is a *serious* fire hazard. Besides that, you should be fine.

[wood nacho]

Thanks for the help everyone. I'm thinking I will remove the current 12v and install a similar one with higher Ah. I think this is the only way I'll feel safe! This would be harmless no?

[dannyg1]

Originally Posted by wood nacho

Thanks for the help everyone. I'm thinking I will remove the current 12v and install a similar one with higher Ah. I think this is the only way I'll feel safe! This would be harmless no?

Yep, that’ll work.