[Rover] Primary Batteries

Wed Apr 8 20:55:33 EDT 2020

1 more important piece of info I forgot:  planned discharge rates.

SLA/AGM & other Lead-Acid:  I was told a long time ago, plan for C/10
maximum discharge rate & don't go above C/8.

LiFePO4:  I have seen discharge rates of C or higher commonly used, we use
a 20AH LiFePO4 battery for the 10GHz liaison station that is ~2A RX / ~20A
TX for around 8hours with 5-10% TX duty cycle without issues.

What this means is the ~400AH marine flooded-cell lead-acid battery bank I
use in my rover is really only capable of 400/10=40A maximum planned
discharge rate -- this combined with the weight of the lead-acid battery
bank may eliminate it from your planned 75A discharge rate since 10x 75AH
batteries is a lot of weight (normal Group24 marine batteries are around
75AH).  My battery bank is 6x Group24s, but they are refurbished so I
tested their capacity (refurb == drained, cleaned, replaced acid, retested,
etc by someone who has done the refurbishment for off-grid solar systems
before).

Hope this info helps.

regards,
Dean -- VA3CDD

On Wed, Apr 8, 2020 at 8:26 PM Ev Tupis via Rover <rover at mailman.qth.net>
wrote:

> Hi Dean,
> That last paragraph is gold.  It gives me real insight into how you are
> configured and why.
>
> I need to think about how to transpose that into how I hope to operate.
>
> Thanks, Dean!
> Ev
>
>
>
>
>
>
> On Wednesday, April 8, 2020, 7:56:01 PM EDT, Dean Denter <va3cdd at rac.ca>
> wrote:
>
>
>
>
>
> LiFEPO4 is lightweight but lots of money, but you can use most of their
> rated capacity (use a BMS to make sure you don't damage the battery -- a
> lot of the commercial batteries have BMS circuits already built in, make
> sure the BMS supports the configuration if you plan to use them in series
> and/or parallel configurations) -- I use a 30AH battery for my 10GHz
> hilltopping setup, it needs to be lightweight since it is part of a gear
> pack that gets carried on my back occasionally.
>
> SLA & AGM are both heavy weight but less expensive, be careful to not
> discharge these below 11.5V or you will damage the cells and you will
> likely only get 50-60% of the rated AH capacity without damaging the
> batteries -- I usually use an automatic cutoff set to 11.8V to turn off the
> power before the batteries get damaged.
>
> For my rover I used standard wet-cell lead-acid marine batteries in my
> rover -- make sure they have ventilation & are properly restrained to not
> tip.  If you go with 12V wet-cell marine batteries, be careful to look for
> DC-type and not DP or Starting batteries (DC = Deep Cycle).  As mentioned
> above, I have an old commercial cut off circuit that shuts down the power
> if the voltage drops too low.  I was running about 400AH of series/parallel
> Group24 DC-type marine batteries to power the rover with a 20A charging
> circuit that is relay switched from an ignition-only circuit so it only
> charges when the engine is running.  The rover has an FT847 (~2A RX / 20A
> TX), an IC746 (~2A RX / ~25A TX), a dual band FM mobile (1A RX / 10A TX), &
> 3 transverters (.5A RX / 10A TX) with a couple of HTs and other gear -- I
> still paper log, but would like to add in a laptop at some point.  I
> usually have enough power to make it thru a VHF contest weekend -- but
> recent contests have only been local 6-8 hour sprints due to work
> commitments.
>
> regards,
> Dean -- VA3CDD
>
>
> On Wed, Apr 8, 2020 at 7:29 PM Ev Tupis via Rover <rover at mailman.qth.net>
> wrote:
> > Adding to this thread...I see that there are three options to consider:
> Absorbent Glass Mat (AGM) Sealed Lead Acid (SLA) batteries, and lithium
> iron phosphate (LiFePO4).
> >
> > Any comments on these in a high current environment?
> >
> > Ev
> >
> >
> >
> >
> >
> >
> >
> > On Wednesday, April 8, 2020, 7:12:44 PM EDT, Ev Tupis via Rover <
> rover at mailman.qth.net> wrote:
> >
> >
> >
> >
> >
> > Thanks, Sean.  I'm hearing either golf cart batteries or marine
> batteries from others, too.
> >
> > -Ev
> >
> >
> >
> >
> >
> >
> > On Wednesday, April 8, 2020, 5:23:48 PM EDT, Sean Waite <
> waisean at gmail.com> wrote:
> >
> >
> >
> >
> >
> > The 100Ah AGMs I use top out at 30A or so continuous pull. We run a pair
> of them with a worst case of about 45-50A worst case draw and usually much
> less. With 75A expected draw you're looking at 3 of those in parallel or
> more likely going for heavier batteries.
> >
> > A lot of people like the 6V golf cart batteries in series+parallel to
> get 12V at the expected capacity and current rating. I'm using 12V
> batteries, it's what I found.
> >
> > I'm topping them off from the car while in motion. Definitely get some
> heavy power poles, or rather the Anderson SB series connectors. You don't
> want to overdraw your car battery while stopped. We disconnect when parked
> and then reconnect in motion. I need to pick up a big marine battery switch
> or something so I don't have the mechanical cycles on my connectors and
> also to make it easier to switch (our first rove required a wrench to
> disconnect 200Ah of battery from the car at each stop while on a rush. Not
> my idea of fun)
> >
> > I found really heavy gauge jumper cables, 4AWG or so, and have been
> using that wire for connecting things. The jackets are probably overly
> thick but it was the best price I found for that wire.
> >
> > I fuse with 80A fuses. I probably could reduce that rating but I wanted
> to leave headroom for the battery string to charge.
> >
> > I've thought about all sorts of other enhancements but there are other
> priorities and this works. Bring a fire extinguisher.
> >
> > 73/Yours in Scouting
> > Sean Waite, WA1TE
> >
> > On Wed, Apr 8, 2020, 16:27 Ev Tupis via Rover <rover at mailman.qth.net>
> wrote:
> >> Hi List,
> >>
> >> Could you offer me some insights?
> >>
> >> I have a need to supply ~75 amps @ 12v during TX.  My plan was to put a
> battery (or two?) in my trunk along with the amplifier to keep leads short.
> >>
> >> I'd keep that battery "topped off" by running some 6AWG from my
> under-the-hood battery.
> >>
> >> Any recommendations for a battery for the trunk (or other insights)?
> >>
> >> Ev, W2EV
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