Re: Fish Finder batteries

GregS wrote:
In article <121chnb6e178o88@xxxxxxxxxxxxxxxxxx>, TJ <tjatari@xxxxxxxxxxxxxx> wrote:

I have two older Humminbird fish finders that are set up as portables using a home-brewed case. They are used intensely during a weeklong family fishing trip in August, but sit idle much of the rest of the time. They can run on anything from 10-16 volts.

The first season I had one I used alkaline D cells, and had to use two sets during the week. I really would rather use rechargeables, mostly as a matter of personal preference. I have been using 10 nicd D cells to run each of them, recharging every other day, but I'm not satisfied with between-season battery life. Maybe it's the charger I've been using or maybe it's the cheap brands I've been buying, or the fact I'm not as diligent as I should be about charging on the off-season, but it seems like I lose several batteries every year and have to buy replacements.

I want to try something different. I thought of nimh batteries, but I don't know if I want to go to the expense of buying 20 nimh batteries if they aren't going to last any longer than the nicds. The idea of buying 40 or so alkalines every year doesn't thrill me, either.

Recently I had an idea and I want to know if it's feasable. My computer's ups uses two 12V sealed lead-acid 7Ah batteries. I won't be using that computer while I'm fishing - I'll gratefully leave it home. The batteries will fit into the fish finder cases - if they can lay on their sides safely. I *could* pack the ups along to use as a charger, but it's pretty big, heavy, and bulky to use for that. I'm wondering about a 10-amp auto charger that has a 2-amp "trickle" mode. (their word, not mine) Assuming I was careful, is there any reason I couldn't use it to top off the charge the end of every day?

I'm thinking that this is an almost ideal solution. That, of course, means there must be something very basic wrong with it. The batteries will be maintained by the ups when I'm not fishing, and I don't have to remember to charge them. Another, probably better, solution would be to buy a second set of sealed batteries to fit the ups (last set was fairly cheap on eBay) and keep them charged with a maintainence charger. If I get 4-5 years out of them, they'd be cheaper than using the alkaline D cells. (can you maintain more than one battery at a time with one of those maintainers? Hmmm. If not, maybe a second ups from eBay is a thought...)

Is any of this workable, or am I nuts?



I have two thoughts. The old nicads had about 4 AHR rating I think.
AA nimh now have about 2 AHR. Only half the rating and they are widely
available along with chargers. You could use the LA batteries but they
are good for high current apps. If I used that, i would use a separates case
with jack to power anything. Internal fusing of course. You can then use that
autobattery charger, allthough ones specifically for those sealed cells
will work best. The battery in the separate case can be heftier. These
batteries can often be found at the surplus electronics companies or
Ebay.

greg

the batteries from your UPS can be used in any position. I would not swap the ones out of your ups when they are only #15-$20 each.

You can get a 13.5v regulated charger that will charge the lead acid batteries for a few bucks. 10 for $15 on ebay right now item # 7593567626 then you could sell the rest that you don't need.

personally i would use 18650 2.4 Ah lithium cells or 10 Ah NiMH D cells but you would need to do some soldering and buy or build a special charger.

10 of the 10 Ah MH10000-TB cells from batteryspace.com would cost about $70 and you could use one of the 10 for $15 chargers since they are limited to 1 amp and regulated they would not overcharge your batteries if you left it on overnight or you could buy a $28 charger from bs.com that would work perfectly with the 10 cell pack. they also sell 10 cell packs of lower rate cells that would work ok for the fishfinder if you don't want to assemble the pack yourself.

if the sealed lead acid (SLA) batteries fit in your housing you could use the charger you have but it will overcharge the SLA batteries and damage them if you leave it on trickle too long, then your UPS might not work when you need it.

-bob
.

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