Maker Pro
Maker Pro

SLA/Li-ion Questions

NachoohcaN

Mar 19, 2018
1
Joined
Mar 19, 2018
Messages
1
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...edium=display&utm_campaign=primecables_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!
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
13,700
Joined
Nov 17, 2011
Messages
13,700
an you charge an SLA battery with a lithium ion jump starter?
The description for the unit you linked to states it can charge a 12 V 3A load (in the manual it even states 3.5 A). However, this is not a charger. It will not provide the required current control (limited charge current, reduction of current at end of charge) for safely and repeatedly charging an SLA battery.

One also has to be careful when interpreting the "technical data" of this device. It states 12000 mAh (aka 12 Ah) but doesn't say at which voltage. It is a common "trick" to give the capacity of the internal battery which usually is at a much lower voltage than the output. Assuming a 3.6 V Lithium battery, 12 Ah translate into roughly 43 Wh which in turn at 12 V is only 3.6 Ah. Take away from that gross capacity the losses within the electronics (assuming an efficiency of 80 % which is an optimistic estimate, I think) you're left with approx. 2.9 Ah effective capacity. Less than 1/2 of the capacity of your SLA battery.

Could I add a 4aH SLA battery in parallel? How does the depletion/charge of the batteries work if they are different Ah?
I don't recommend using different batteries. Neither in series nor in parallel. It is best to use batteries of the same type. We have another thread on that issue.
 
Top