Gell Cell vs Deep Cycle Marine Battery to power Scope
Jerry Lodriguss
I'm interested in purchasing a battery to power my scope setup
in the field. All of my equipment (Drive corrector, ST-4, and
anti-dewers) draw about 3 amps.
I was looking at maybe a 40 amp hour battery minimum, but I
have a couple of questions on gell cells vs lead-acid deep
cycle marine batteries.
Is there any difference in how low you can run these two types?
I hear the gell cells do NOT like to be discharged all the way
and that they can be damamged if you do this. How about the
deep-cycle marine, do I have to worry about this?
Any difference in performance in cold weather, near freezing
and sub-freezing temperatures? Would keeping the battery in an
insulated container help here?
Can you recharge either one of these batteries from a running
car engine? Would the alternator/regulator (I know next to
nothing about electricity!:-) ) in the car put out too much,
what? "juice" that would damamge either type battery? I'm
thinking about trying to recharge in the field off the car if I
pull an all-nighter in the winter on a multiple day trip.
Any comments suggestions welcome!
Thanks in advance.
Jerry
--
email: j...@astropix.com
Astrophotography Techniques and
Digital Enhancement in Photoshop Tips:
http://www.astropix.com
Larry Bourdillon
Jerry Lodriguss wrote:
>
> I'm interested in purchasing a battery to power my scope setup
> in the field. All of my equipment (Drive corrector, ST-4, and
> anti-dewers) draw about 3 amps.
>
> I was looking at maybe a 40 amp hour battery minimum, but I
> have a couple of questions on gell cells vs lead-acid deep
> cycle marine batteries.
>
> Is there any difference in how low you can run these two types?
> I hear the gell cells do NOT like to be discharged all the way
> and that they can be damamged if you do this. How about the
> deep-cycle marine, do I have to worry about this?
>
> Any difference in performance in cold weather, near freezing
> and sub-freezing temperatures? Would keeping the battery in an
> insulated container help here?
>
> Can you recharge either one of these batteries from a running
> car engine? Would the alternator/regulator (I know next to
> nothing about electricity!:-) ) in the car put out too much,
> what? "juice" that would damamge either type battery? I'm
> thinking about trying to recharge in the field off the car if I
> pull an all-nighter in the winter on a multiple day trip.
I am not too familiar with the characteristics of gell cells. But as far
a lead-acid batteries are concerned, I could add a couple of points.
First, the difference between the deep cycle versions and the standard
fare battery is only in the plate design; the chemistry is the same.
Deep discharging causing a non-removable coating (lead oxide, if I
remember) to build up on the plates, effectivly reducing the available
area. The plates in the deep discharge units are designed to compensate
somewhat for this. Bottom line - *any* lead acid cell will last longer
if it is not deep discharged. Second, temperature will definitely affect
the available discharge rate. For low current drains, however, this may
not be an appreciable factor.
Yes, it would be possible to recharge such a 12 volt battery from your
auto. However, I wouldn't have any sensitive electronics connected at
the time of recharging. Also, you might want to check that you auto's
alternator can handle having a nearly dead battery suddenly connected.
Good seeing...
...larry
James W. Burrows
On 9 Sep 1996, Jerry Lodriguss wrote:
> Can you recharge either one of these batteries from a running
> car engine? Would the alternator/regulator (I know next to
> nothing about electricity!:-) ) in the car put out too much,
> what? "juice" that would damamge either type battery? I'm
> thinking about trying to recharge in the field off the car if I
> pull an all-nighter in the winter on a multiple day trip.
There's been a lot of discussion about batteries on the MAPUG list, and
there's guys who will swear that either one's better. I myself got a 94
Ah deep cycle lead-acid (good exercise!). My main worry about your plan
is that my 110V battery charger only puts out 10 A; does an alternator do
much better - 4 hours running the car (idle probably won't be enough
either)?
Jim Burrows 206-244-2933
E-mail: bur...@halcyon.com
Seattle: WGS84 lat 0.828547, long -2.135692 (rad)
Ron Peterson
On Sep 09, 1996 07:51:41 in article <Gell Cell vs Deep Cycle Marine Battery
to power Scope>, 'Jerry Lodriguss <j...@cyberenet.net>' wrote:
>I'm interested in purchasing a battery to power my scope setup
>in the field. All of my equipment (Drive corrector, ST-4, and
>anti-dewers) draw about 3 amps.
>I was looking at maybe a 40 amp hour battery minimum
40 amp hour battery should be plenty for a nights observing if
your equipment only draws 3 amps.
>Is there any difference in how low you can run these two types?
>I hear the gell cells do NOT like to be discharged all the way
and they give more efficient service if they are used that way. A gell
cell battery is another story. Your information is correct. Gell cells
are made for use under conditions that call for a power supply that will
not spill liquid if tipped over, but they don't usually have the reserve
power a deep cycle has and won't last as long if fully drained each time
before being recharged.
>Any difference in performance in cold weather, near freezing
>and sub-freezing temperatures? Would keeping the battery in an
>insulated container help here?
of these two batteries. The gell cell will withstand lower temperatures
before freezing, but unless you live in an area that experiences temps
below -20 degrees, you shouldn't have to worry about it. I would use a
container of some sort for the deep cycle, but more to make sure it isn't
accidentally tipped over.
>Can you recharge either one of these batteries from a running
>car engine? Would the alternator/regulator (I know next to
>nothing about electricity!:-) ) in the car put out too much,
>pull an all-nighter in the winter on a multiple day trip.
is use a set of jumper cables and connect positive to positive and negative
to negative between your car battery and the one you are charging. I
wouldn't keep using the battery to power your equipment while you're
charging it though, and take into account that it will take about an hour
to replace any appreciable charge in either type battery regardless of how
you recharge it.
Personally, I would choose the deep cycle over the gell cell. Any
advantages of the gell cell over the deep cycle would ones of conviniance
(no spills, etc.) and not worth the two or three times the cost. Gell
cells are spendy!
Ron Peterson
>Any comments suggestions welcome!
>
>Thanks in advance.
>
>Jerry
>
>--
>email: j...@astropix.com
>Astrophotography Techniques and
>Digital Enhancement in Photoshop Tips:
>http://www.astropix.com
>
>
Darr...@usa.pipeline.com
Andy Domonkos
I prefer GelCEll over lead acid for the safety issues.
Whichever you choose, take measures to isolate the battery from your
optics during storage and transportation. Both these batteries vent
corrosive vapors that will damage the coatings on optics as well as
corrode the metal in scopes.
Andy
Jerry Lodriguss
Andy, thanks, I bought a 40 amp hour gel cell today.
Thanks for the tip on the vapors, I didn't think of this. I was
just planning on carrying the battery in a small ice chest to
insulate it, and carrying everything in the back of a Jeep
Cherokee.
Any suggestions on carrying the battery in the same car with
the scope?
Michael Edelman
Jerry Lodriguss (j...@cyberenet.net) wrote:
: I'm interested in purchasing a battery to power my scope setup
: in the field. All of my equipment (Drive corrector, ST-4, and
: anti-dewers) draw about 3 amps.
: I was looking at maybe a 40 amp hour battery minimum, but I
: have a couple of questions on gell cells vs lead-acid deep
: cycle marine batteries.
: Is there any difference in how low you can run these two types?
: I hear the gell cells do NOT like to be discharged all the way
: and that they can be damamged if you do this. How about the
: deep-cycle marine, do I have to worry about this?
Yes, Gel cells are designed for standby service, not for rapid
cycling. They will have a very short life under such conditions.
They also suffer at low temperatures.
Marine batteries are similar to auto batteries, but have thicker plates
to better withstand deep cycling and high discharge rates. A marine
battery will last *much* longer in service.
: Can you recharge either one of these batteries from a running
: car engine? Would the alternator/regulator (I know next to
: nothing about electricity!:-) ) in the car put out too much,
: what? "juice" that would damamge either type battery? I'm
: thinking about trying to recharge in the field off the car if I
: pull an all-nighter in the winter on a multiple day trip.
There's no way you'll run a marine battery down over night running a
telescope and a defogger. But in a pinch you could charge it via
a running car. Gel cells should also be self-regulating on charge
(being lead acid) but they're more prone to damage from alternator
duimping, being of lighter construction.
Mike Schnierle
In article <3234A2...@ix.netcom.com>, Larry Bourdillon <lab...@ix.netcom.com> says:
>
>Jerry Lodriguss wrote:
>>
>> I'm interested in purchasing a battery to power my scope setup
>> in the field. All of my equipment (Drive corrector, ST-4, and
>> anti-dewers) draw about 3 amps.
>>
>> I was looking at maybe a 40 amp hour battery minimum, but I
>> have a couple of questions on gell cells vs lead-acid deep
>> cycle marine batteries.
>>
>> Is there any difference in how low you can run these two types?
>> I hear the gell cells do NOT like to be discharged all the way
>> and that they can be damamged if you do this. How about the
>> deep-cycle marine, do I have to worry about this?
>>
>> and sub-freezing temperatures? Would keeping the battery in an
>> insulated container help here?
>>
>> car engine? Would the alternator/regulator (I know next to
>> nothing about electricity!:-) ) in the car put out too much,
>> what? "juice" that would damamge either type battery? I'm
>> thinking about trying to recharge in the field off the car if I
>> pull an all-nighter in the winter on a multiple day trip.
>
much power as yours. I have had no problem depleting the gel-cell
completely and recharging it with a small motorcycle battery charger
plugged into the wall socket. I have not tried to recharge it from the
car alternator. I suspect that the alternator might be too much for it,
but it is samll battery.
I used to own a camping trailer that used "marine" or "deep-discharge"
lead acid batteries for electrical power when 120 volt ac wasn't available.
Those batteries worked fine, even in cold weather. They can be discharged
completely and recharged any number of times, as long as you keep the
water levels up, using distilled water, preferably. Most trailer systems
are designed to charge the storage batteries from the car alternator when
the trailer is being towed, so that shouldn't be a problem. The only
disadvantages to the marine batteries are the weight and the fact that
marine batteries are definitely not "no maintenance." Because of the
design differences between marine batteries and car batteries, you must
keep the water in the battery at a proper level. Also, obviously, the
marine batteries, unlike the gel-cells, cannot be stored on their sides
or the fluid will run out.
Good luck.
Mike Schnierle
Andy Domonkos
Gel Cell discharge rate: Current divided by 20. To provide 2 amp/hr
service 40/20 gives you the 2A/hr service required. In short, the 40A
battery will provide 2A/hr for 20 hours.
Andy
Bicyclist1
I did a lot of studying in the design of a lighting system for my bicycle
using gel cells. The performance you get from a gel cell is very
dependant on the current draw rate, the temperature, the depth of
discharge, the charge current, and the charging voltage. I wrote a
lengthy article on it that made its way into the FAQ in rec.bikes several
years ago. (I can't find a local electronic copy).
I can summarize some good rules of thumb for sizing up the job:
-The size of the battery (e.g. 40Amp hours) means that the cell is capable
of supplying current at 1/10 that rate for 10 hours at an ambient room
temperature (typ. 70deg F). So for this case, this battery can supply 4
amps per hour for 10 hours at 70 deg. If you draw much more than 4 amps
per hour, you need to derate. The curves are not linear, and vary between
0 and 20% derating.
If the temperature of the cell is lower, you have to derate. Again, the
curves are not linear and vary between 0 and 20% over a large temp. range.
Potentially you have to derate by 40% if you are drawing a lot more than
4 amps when the cell is a lot colder than 70deg. My cut on temp is that
there is a lot of mass in these batteries and if you can insure they are
warm before you start, and can reasonably insulate them, temp should not
be a factor.
As for charging, the charging current is related to the charging voltage.
The more voltage, the greater the current, the faster you recharge. If
you want to charge faster, you will shorten the overall life of the cell
in terms of the number of cycles you can recharge. It is recommended that
you trickle charge and then float or remove the battery when full charge
is reached. The literature states that if you charge right you should see
typ. about 10000 recharge cycles from you cell. If you abusively charge,
(high voltage/current, long times) that number drops quickly and you may
only see a 1000 or so. Your intended use may say the ecomomics of abusive
charging is OK cuz that may be more times than you will likely use it. If
you charge at very high voltages, the cell will start to boil and will
outgas hydrogen. This will shorten the life of the cell and is
potentially very dangerous if your cell is not in vented location.
Brad
Brad Grande - WB0OYX
AT&T-Microelectronics
gra...@mtdcr.att.com
bicyc...@aol.com
908-957-7656
Andy Domonkos
Bicyclist1 (bicyc...@aol.com) wrote:
:
: -The size of the battery (e.g. 40Amp hours) means that the cell is capable
: of supplying current at 1/10 that rate for 10 hours at an ambient room
: temperature (typ. 70deg F). So for this case, this battery can supply 4
: amps per hour for 10 hours at 70 deg. If you draw much more than 4 amps
: per hour, you need to derate. The curves are not linear, and vary between
: 0 and 20% derating.
The Gates designers handbook recommends the Capacity/20 rule. All battery
back systems I've designed use that principle.
I can see how the C/10 can derate quickly especially with age , temp, etc.
Andy
Jeffrey R. Hapeman
>Yes, Gel cells are designed for standby service, not for rapid
>cycling. They will have a very short life under such conditions.
>They also suffer at low temperatures.
This is true for SOME gel cells, but one can buy quality gel cells that
are designed for deep discharge and last a very long time AND work well
in cold weather. I have several 33 amp-hour gel cells that are very
compact and wonderful maintanence-free batteries. They are designed for
electric wheel chairs, where a battery with liquid is an obvious hazard.
They are designed for deep discharge, but should be charged with the
proper type of automatic-cut-off charger that "finish trickles" the
charging. This is because they are sealed and one does not want to have
an explosion due to heating due to too rapid charging.
The advantages of gel cells far outweigh the extra cost for me. I use
mine primarily for research purposes, where I must transport them around
the country. Unless you're driving yourself, you can't ship most
lead-acid liquid batteries. Why? They're dangerous if they tip over or
start to leak--lots of corrosive acid.
By the way, my two gel cells cost about $70, and have been
charging/discharging (completely) for the last three years. They show no
sign of stopping. I find that feeling safe with the battery was worth
the extra cost.
Jeff
--
******************************************************************************
Jeffrey R. Hapeman
Department of Botany
jhap...@students.wisc.edu
University of Wisconsin-Madison jhap...@macc.wisc.edu
430 Lincoln Drive
Madison, WI 53706
Ph (608)-262-4422 FAX (608)-262-7509
http://www.wisc.edu/botany/Orchids/Orchids_of_Wisconsin.html
******************************************************************************
spooner
The July '89 S & T has a gel cell charger design. Looks like it could be
adapted for cigarette lighter use if 6 volt batteries were recharged one
at a time.
Mike
Steve Scampini
What brand batteries are you using?
TIA,
Steve
Anthony E Arnerich
Jerry Lodriguss <j...@cyberenet.net> wrote:
> I'm interested in purchasing a battery to power my scope setup
> in the field. All of my equipment (Drive corrector, ST-4, and
> anti-dewers) draw about 3 amps.
>
> I was looking at maybe a 40 amp hour battery minimum, but I
> have a couple of questions on gell cells vs lead-acid deep
> cycle marine batteries.
You might wish to consider using seperate batteries.
Pro:
Easier to carry (less laod per trip)
Some equipment combinations won't tolerate common grounds (ST7 or ST8
used to autoguide a G11 without going through SBIG's relay adapter).
This is a rare problem though.
Con:
More expensive per amp-hour
Recharging ritual is a bit more complicated.
> Is there any difference in how low you can run these two types?
All gel cell data sheets I've seen describe them as being deep discharge
type. This is why they are used for alarm systems and emergency lighting.
> I hear the gell cells do NOT like to be discharged all the way
> and that they can be damamged if you do this. How about the
> deep-cycle marine, do I have to worry about this?
Any battery that is discharged *all* the way down will be seriously damaged.
There are prudent limits if you expect to achieve many charge/discharge
cycles. In fact, across a wide range of discharge depths from 1% down to maybe
50% down there is a fixed amount of amp hours that the lead acid battery will
be able to deliver over it's useful life. In effect this means that if you
buy too small a battery you will have to recharge too often. Too large a
battery will last longer than you, and is too heavy during all that time.
A good rule is to never discharge the lead acid below 1.8 volts per cell
(there are 6 cells in a "12V" battery). This point is achieved when you've
used up about 2/3 of the nominal capacity. You might want a little more
margin, and limit yourself to a 50% discharge.
Thus, a full week at the Texas Star Party x 10 hours per night x 3 amps
x 2 equals 420 amp hours. Allowing the use of a charger during the days
gets you to 60 amp hours. Turn on your heaters and ST-4 only when they
are used (the ST-4 of course needs cool down time and needn't be switched
off for the few minutes it takes to align the next target) can save you
some more. Discharging a little deeper than 50% will allow the use of a
slightly smaller bettery yet. Run your heaters at low power in all
conditions other than monsoons, and you'll save yet more power. Your
40 amp hour battery starts to look a *little* bit big now.
> Any difference in performance in cold weather, near freezing
> and sub-freezing temperatures? Would keeping the battery in an
> insulated container help here?
Cold weather cuts far into the capacity of lead acid batteries. Sub freezing
temperatures can cut the capacity by half. An insulator would help if you
had a heater you could put in there with the battery, but an electrically
powered heater won't buy you much. :-) There are chemical heat packs
available.
> Can you recharge either one of these batteries from a running
> car engine? Would the alternator/regulator (I know next to
> nothing about electricity!:-) ) in the car put out too much,
> what? "juice" that would damamge either type battery? I'm
> thinking about trying to recharge in the field off the car if I
> pull an all-nighter in the winter on a multiple day trip.
Gel cell batteries are not designed for the rapid recharging that
vehicular batteries are made for. You could wire one of those dual
battery adapters into your car like what they put into motorhomes, and
recharge the marine battery that way. For my gel cells I use automatic
chargers that are designed for the battery size in question. I run
these on the "morning after" drive home from a plug-in 120V inverter
in the car. What I lose in efficiency I gain in proper electronic control.
FYI, safe recharging rates are:
Fast: Current limited to Amps = 1/10 the num. value of the Amp-Hr rating
of the battery. This will end up being around 14.5 to 15.0V measured
at the battery terminal (not at the power supply if the connection
leads are anything but monstrously huge).
Example - 4.0 amps for your 40 Amp-Hr battery
Slow: Voltage limited to 13.8V. This will take several days if you've
discharged very deep! It is however a safe voltage for indefinite
periods of time, so this is used to keep alarm batteries topped
off.
An automatic charger switches between these modes as appropriate, close to the
"fully recharged" level.
Clear Skies,
Tony Arnerich
lrob...@ix.netcom.com
Jerry Lodriguss <j...@cyberenet.net> wrote:
>I'm interested in purchasing a battery to power my scope setup
>in the field. All of my equipment (Drive corrector, ST-4, and
>anti-dewers) draw about 3 amps.
>I was looking at maybe a 40 amp hour battery minimum, but I
>have a couple of questions on gell cells vs lead-acid deep
>cycle marine batteries.
Go with a 60 amphour then you don't have to worry about the
recharginging as much. This gives you 20 hours of run time.
>Is there any difference in how low you can run these two types?
>I hear the gell cells do NOT like to be discharged all the way
>and that they can be damamged if you do this. How about the
>deep-cycle marine, do I have to worry about this?
Actually there is a third better type of battery than either of these.
It is a Valve Regulated Lead Acid battery and is typically used by
the phone company in their remote cabinets. It is a sealed battery
similar to the gel cell but without all the problems of the gel cell.
They can be picked up at the scrap heap at your local phone company
yard if you ask nicely. Be sure to get a 12 volt one. I like the
Powersafe SBS60. It is orange and relatively small, maybe 4" wide by
10" long by 6" tall.
>Any difference in performance in cold weather, near freezing
>and sub-freezing temperatures? Would keeping the battery in an
>insulated container help here?
Definitely. You want your battery to be near 70 degrees F for maximum
performance and longer life although it will run at other temps, just
not as long.
>Can you recharge either one of these batteries from a running
>car engine? Would the alternator/regulator (I know next to
>nothing about electricity!:-) ) in the car put out too much,
>what? "juice" that would damamge either type battery? I'm
>thinking about trying to recharge in the field off the car if I
>pull an all-nighter in the winter on a multiple day trip.
Not sure about this one, Jerry, might work, but I prefer to trickle
charge mine and I've never run it down even after several days of
observing.
>Any comments suggestions welcome!
Hope this helps.
Larry Robinson
>Thanks in advance.
>Jerry