[cigarbox]

Hey guys, I am a new member here. My name is Ted and I am from Marietta, GA, about 20 mins northwest of Atlanta.

I have been looking at the RWA products and have been seriously impressed.

I am considering purchasing a Sig 30.2, but I have one concern. How is it that the batteries both stay at an equal charge when charging? It seems to me that the batteries would become unbalanced if it is a 2x12v series system charged by 24v. I thought a 2x12v system had to be charged in parallel by a 12v charger to keep it balanced??

Hopefully someone can clear this up for me.
Thank you!

[Vinnie R.]

Hi Ted,

Welcome to audiocircle and the RWA forum!

How is it that the batteries both stay at an equal charge when charging? It seems to me that the batteries would become unbalanced if it is a 2x12v series system charged by 24v.

We use a battery analyzer to closely 'match' the two batteries (especially in terms of their internal impedance) so when they are charged in series, the voltage across them is approx. the same.  Since they are in series, the current that flows through each battery is the same.  So you want the internal impedances to be matched as closely as possible in order to get approx. the same voltage across each battery during the charging cycle.

I thought a 2x12v system had to be charged in parallel by a 12v charger to keep it balanced??

24V SLA chargers are designed to charge two 12V SLA batteries in series.  They even make chargers designed for 36V and 48V (for 3 and 4 batteries in series).  Again, the trick is to match up the batteries with an analyzer as mentioned above.  IMO, with two batteries in series, it is very doable.  If going with more batteires, I would charge them in parallel.  But when charging in parallel, the batteries see equal voltage but will draw different amounts of current (again, matching the batteries tends to minimize this). 

Hope this helps,

Vinnie

[cigarbox]

hahaha, that is very clever! It's so simple that I didn't even consider that as a possibility. Cool!

Just because I am interested in this sort of thing, how close does the internal impedence of the batteries have to be for the system to work? 5%? 1%?


thanks for the quick reply.

[Vinnie R.]

Hi Ted,

I also forgot to add that we also match the "state-of-charge" of each battery.  It is not a good idea to install a battery that is 60% discharged, and one that is only 15% discharged - and then charge them in series. 

So by closely matching battery impedance and state-of-charge, everything works out well.

Just because I am interested in this sort of thing, how close does the internal impedence of the batteries have to be for the system to work? 5%? 1%?

+/- 5% (or better) is good for internal impedance and state-of-charge matching. 

Best regards,

Vinnie

[cigarbox]

thanks so much, Vinnie. I like the philosophy of your company, and I do plan on buying a 30.2 soon.