battery voltage while running trolling motor.

[shizzy]

I was wondering what voltage I should be seeing from my battery with a full charge while using my trolling motor. My battery is one year old and I cant remember what I was seeing last season. All seems well and I can troll all day but I hit 11.5-11.3 as soon as I start using the trolling motor.

I charge the battery after every trip and it holds a charge of 12.72-12.74 volts after sitting for 2 days after coming off the charger.

I have a 40# Minnkota and my Depth finder hooked up to the battery.

[broken_line]

it shouldnt drop to that i have a 30lb thrust, depth finder areator pump, radio hooked up to that one battery and it doesnt drop below for an hour with all this stuff on at the same time..

[jeffreyd]

That is a dead battery but if you are watching while you are trolling, that is indicating the load voltage. Check it after you troll for a few min to see if it recovers or not. I think you have a bad battery, age does not matter, heck here in AZ if I get a year i feel happy. Environmental issues are a big factor as is clean connections etc.

[shizzy]

it doesnt come back up once you have trolled for a while.

darned Wally World battery.

[jeffreyd]

i would dump it and put a good marine deep cycle battery in it. if you get a deep cycle, it can handle the deep discharge and then the sudden charge to full and back and forth. the problem with batteries is that we rarely take them down to such a deep discharge they build a memory. normally a battery only uses the top 20-25% of the charge, then we throw a charger on it and build it back. I think if i had the space, a true deep cycle battery is a delco 1150 with screw post. the problem is that they are expensive compared to others on the market. i would use an interstate if you have access to them as from other posts, they seem to be the most common in that part of the country. we only use delco in the fire trucks as they are the only one that is listed by NFPA as a deep cycle.

[shizzy]

I ran it today and it stayed at 12.3 - 12.4 all morning while running the trolling motor. it came back up to 12.5 when I checked it with the multimeter after the trip. It did dip down to 11.9 volts while running the trolling motor on the high setting (rareley used) so while its not 100% I think it will work for now.

Im going to be out of the country for most of July so Im going to limp this battery through this season if I can.

[BobT]

I'm not sure but I don't think I'd right off the battery just yet.

When a load is applied to a battery I would expect to see some voltage drop relative to the load applied due to the battery's internal resistance. That's what a load test does. It applies a relatively high load and monitors the battery's ability to maintain an acceptable voltage level. A common standard for component voltage ratings is +/- 10%. If your 12v rated electric motor follows this standard it should be functional from 10.8v - 13.2v. I don't know for sure if this "rule" applies to battery powered dc systems though.

I don't know the specifications for your battery so I can't tell you what to expect but basically, the higher the load the lower your battery's output voltage will be. The voltage drop may be more significant in colder conditions as the chemical reaction inside the battery will be slower.

Edit: I just looked it up in my NFPA79 code book. Bear in mind this is related to industrial equipment and may not apply in this case.

Quote:

4.3.3 Direct Current (dc) Supplies from Batteries

4.3.3.1 Voltage. The electrical equipment shall be designed to operate correctly where the dc supply voltage of batteries is from 85% to 115% of the nominal voltage. A supply voltage from 70% to 120% of the noinal voltage shall be permitted for dc supplies to battery-operated vehicles.

If we apply this rule then it would be considered normal for your motor to run at voltages from 10.2v to 13.8v. This would seem reasonable considering that many voltage regulators are set to a maximum of 13.8v.

[jeffreyd]

NFPA 1901 standard for Fire appartus and low voltage info