My new fish finder is rated for 10-20 volts. My old one was 10-17 volts. I was using a 10 aa battery holder for a theoretical 15 volts. I'm thinking of switching to a 12 aa holder for a theoretical 18 volts.Since the batteries can have a starting voltage of 1.6 or so, am I pushing my luck?

If it was me, I would go for it. Even at 1.6 v per battery, thats only 19.2 volts. Still you might contact the manufacture and confirm 20v upper end, and then maybe test your battery voltage as well, at least the first time. You could get a really long run time with that set up, that sure will be sweet. Btw, do you mind me asking what finder you purchased?

Moonman.

The manufacture speck is usually for good operations so that unit should work well at 10 volts. I have not measured the current at different voltage on your unit but I have on other units. I found that higher voltage results in higher current and I believe without better performance. If this is the case more voltage means higher current and shorter battery life. Best battery performance is obtained when most of the energy is removed from the batteries when the voltage drops below the detectors good operating range.
I just went and measured a unused 1 year old Energizer Ultra Lithium battery which was at about 50°. It measured 1.807 Volts no load (the voltage would be higher if the temperature was higher). (1.807*12=21.6 volts) Batteries do not hold that voltage for long with a load but it is what the detector would see at turn on.
I have found that most hours of detector operations per ounce and per dollar of AA batteries is 9 Energizer Ultra Lithium batteries in series. A close second is 10 Duracell Quantum batteries in series.
For more information see
this link.

quote Moonman: "If it was me, I would go for it. Even at 1.6 v per battery, thats only 19.2 volts. Still you might contact the manufacture and confirm 20v upper end, and then maybe test your battery voltage as well, at least the first time. You could get a really long run time with that set up, that sure will be sweet. Btw, do you mind me asking what finder you purchased?


Moonman."

It is the Hummingbird PiranhaMax 153.

quote MagicPaddler: "The manufacture speck is usually for good operations so that unit should work well at 10 volts. I have not measured the current at different voltage on your unit but I have on other units. I found that higher voltage results in higher current and I believe without better performance. If this is the case more voltage means higher current and shorter battery life. Best battery performance is obtained when most of the energy is removed from the batteries when the voltage drops below the detectors good operating range.
I just went and measured a unused 1 year old Energizer Ultra Lithium battery which was at about 50°. It measured 1.807 Volts no load (the voltage would be higher if the temperature was higher). (1.807*12=21.6 volts) Batteries do not hold that voltage for long with a load but it is what the detector would see at turn on.
I have found that most hours of detector operations per ounce and per dollar of AA batteries is 9 Energizer Ultra Lithium batteries in series. A close second is 10 Duracell Quantum batteries in series.
For more information see
this link. "

That is interesting,so basically with higher voltage available the unit will basically "use the extra", at least up to a point? I am surprised that the lithiums make up for their cost in performance. That is good news,though,since they weigh about 1/2.How would I need to modify my 10 aa holder for only 9 cells?Last but not least,Hummingbird claims a current draw of 100ma for this basic unit, which sounds believable, but they claim the same current draw for all of the non color units in that series including the ones with gps and power ranging from 100 watt rms to 200 watt rms. Is that even possible? How do you double power and add gps and still maintain a 100ma draw? Thanks so much for your help.

Realize that when they say it draws 100 ma that means under some condition it draws 100ma. During turn on and deep water operations most detectors draw more current. If your detector was drawing 100ma from Ultra Lithium batteries the batteries should last about 31 hours. So estimate how many hours you will fish on a trip and make sure you have enough batteries to last the trip. I buy at Sams Club and get a fair price. I discuss battery holders near the bottom of the link mentioned above.

MagicPaddler,
I finally had time to go over all the information and tables in your previous post on this subject. It was very interesting and informative. It looks like I will be going with the ultimate lithium set up. The only thing I'm not sure about is the cost estimate for duracell alkaline aa. I found aa coppertops all over for .38 to .60 cents depending on quantity, which would make them cheaper than ultimate lithiums per mah.The comparison chart has them at over 1.00. I am still going with the lithiums, as I think the advantages outweigh the cost,at least for me.Thanks again!

There is 2 Duracell AA batteries. The first one I plotted is Duracell coppertop then a Duracell Quantum. The Coppertop put out is about 1830 mAh while the Quantum puts out 2350 mAh. Most of my batteries were purchased at Costco or Sams. Some I got the price from on line sellers.

quote mgraber: "

quote Moonman: "If it was me, I would go for it. Even at 1.6 v per battery, thats only 19.2 volts. Still you might contact the manufacture and confirm 20v upper end, and then maybe test your battery voltage as well, at least the first time. You could get a really long run time with that set up, that sure will be sweet. Btw, do you mind me asking what finder you purchased?



Moonman."

It is the Hummingbird PiranhaMax 153."

Thanks.