[DeTomaso] Couple Of Qs

Sean Korb spkorb at gmail.com
Tue Jun 13 13:08:51 EDT 2017


There is a lot of concern about alternator charging.  Don't line up a
couple of DeWalt packs into your car and hope for the best.  The
larger format batteries have internal circuitry for the BMS (battery
management system) to keep all the cells balanced and turn cells down
during operation if they have an increase in resistance.  It's a lot
easier to get thermal runaway in those systems vs a lead acid battery
which also has multiple cells.  Lead can also explode from a shorted
or high resistance cell in the pack but the chemistry doesn't act as
quickly and the fire goes out after the explosion.  The Lithium acts
so fast you only have a few seconds to break the circuit or there will
be a fire.  It probably wouldn't be too risky on a Pantera since most
of the load is on start, and the constant load of 40A or so is well
below nominal, unlike a laptop which runs flat out (at least on mine).

There's a lot of argument (not really, it's like it is here where
people talk about 351W vs 351C) about "bottom balancing" vs "top
balancing" your pack.  Top is when you make all the batteries equal at
the top of the charge and bottom is all cells are equal at the bottom
of the charge.  With top, you *must* have a BMS.  With bottom, you
should have a BMS anyway but you can get away with it if you check
your sells a lot by hand.

Production stuff they don't argue a lot.  Everything gets a BMS.  It
adds to the expense but it is coming down in price like everything
else electronic.


On Tue, Jun 13, 2017 at 12:46 PM, Joseph F. Byrd, Jr.
<byrdjf at embarqmail.com> wrote:
> Is there any concern with older alternator/regulator charging?   I though LI
> products needed a "smart" charger.
>
> -----Original Message-----
> From: DeTomaso [mailto:detomaso-bounces at server.detomasolist.com] On Behalf
> Of Sean Korb
> Sent: Tuesday, June 13, 2017 12:21 PM
> To: DeTomaso Mail List
> Subject: Re: [DeTomaso] Couple Of Qs
>
> Half the weight and 5 times the cost:
> https://www.summitracing.com/parts/brl-i25x/overview/
>
> Also twice the reserve AH reserve capacity too and with my 2500CFM fans
> pulling 20A in bumper to bumper idling traffic... that could be handy as the
> Raleigh/Durham area becomes Atlanta.
>
> I've been wondering how these fare long term.  They are supposed to last
> twice as long or more than an AGM battery too.  Could be easily relocated to
> the rear of the car but it's not hard to build a bucket in the trunk for it.
> I'm not sure of the chemistry though.  If it is not LiFeP04 the failure mode
> is... very intense.  I was thinking of Hammond's crash and while Pb
> batteries also explode, the energy cooped up in a higher rated Lithium
> battery is stunning when released.
>
> sean
>



-- 
Sean Korb spkorb at spkorb.org http://www.spkorb.org
'65 Suprang,'68 Cougar,'78 R100/7,'60 Metro,'59 A35,'71 Pantera #1382
"The more you drive, the less intelligent you get" --Miller
"Computers are useless.  They can only give you answers." -P. Picasso


More information about the DeTomaso mailing list