Re: [MV] Mixing batteries

From: Bruce Beattie (bruce@eecs.berkeley.edu)
Date: Tue Apr 29 2003 - 18:13:27 PDT


Hi Glen,
    Ok, I guess I didn't realize the the other systems used a 24 volt charging
system. I thought that they used the system that is in the CUCV ( except M1010)
where you have a seperate
12 volt generator charging each battery. At least that is what I thought was
happening.
So in the series case you have a good point.
Thanks for the lesson!
Bruce MVPA 23824

Glen Closson wrote:

> One issue is that in a series circuit (the two 12V batteries in series) you
> always have the same current flowing through each cell (Norton's current
> law) if you are charging or discharging. So if you have different
> chemistries, once battery will probably charge up faster than the other one,
> so the first one may get over charged.
>
> When you discharge the batteries (the most load they see is when cranking)
> one battery may act like a limiting device for the "better" battery.
>
> This also applies to mixing a new battery with an old one.
>
> My guess is that is okay for the short term (emergency), but you will see
> decreased total battery life and performance for the long term.
>
> Regards,
>
> Glen
>
> -----Original Message-----
> From: Military Vehicles Mailing List [mailto:mil-veh@mil-veh.org]On
> Behalf Of Bruce Beattie
> Sent: Tuesday, April 29, 2003 4:58 PM
> To: Military Vehicles Mailing List
> Subject: Re: [MV] Mixing batteries
>
> Ok, I'll bite, Why would it make a difference if you use two different
> chemistries?
> As far as I know batteries don't talk to each other, so how on earth can
> they
> tell if the other battery is different.
> The electrical load on each battery is going to depend on the application,
> and in 24 volt settups
> on CUCV's the loads and charging patterns are radicaly different from what I
> can see. Not that I am
> a guru about this sort of thing.
> Bruce MVPA 23824
>
> "Employee@MilVeh.com" wrote:
>
> > If you are replacing older 6TL batteries with new 6TMF
> > (or 6TLFP) batteries, it is desirable not to mix 6TL
> > with 6TMF/6TLFP in the vehicle/equipment. The older
> > 6TL cases are all green, including the top.
> >
> > The newer styles 6TLFP and 6TMF have black tops and a
> > green case or brown case. The reason is that the
> > chemistries are different. Bottom line: Its most
> > desirable to have "black tops with black tops" and
> > "green tops with green tops."
> >
> > If you need to know Army approved NSNs for other types
> > of batteries, like those needed for communications and
> > electronics, the Army CECOM-LRC website gives common
> > use batteries, both commercial and MILSPEC styles, in
> > their "Preferred Power Sources" listing.
> >
> > --- RKubu@aol.com wrote:
> > > List,
> > > I know there was a thread recently that covered
> > > mixing batteries. I cannot locate the messages and
> > > there is currently no list archive. Is it OK to mix
> > > 6TLs and 6TMFs? The latter look identical to the
> > > former and I was told they will work in a 5 ton.
> > >
> > > Thanks,
> > > Bruce
> > >



This archive was generated by hypermail 2.1.4 : Sat May 07 2005 - 20:18:40 PDT