Skeeter0007 Posted September 14, 2009 Posted September 14, 2009 Hi all Seems to be the right place to get answers. So if you don't mind a quick question that would be great. I have a 2000 nitro CDC 911 with a 36 volt system on board, (225 EFI). I seam to be killing batteries like there going out of style. I was wondering if I have this thing wired up right. 3 batteries. all in series. with the trolling motor feeding off all three. The engine/live wells ect feeding off of one. and the third with nothing feeding off of it. The batteries in question are 2 under a year old and one purchased this year to replace one that failed. Today I go out on the water get to my fav hole and wamo my Maxim 101 at a setting of 100 thrust acting like 20 thrust. Tell tale sign that I have a problem. Take it home. Pull the batteries and hook them up to my in house 3 bank charger and 1 reading no life. This battery was bought last year. Am I doing something wrong here? Or do I have just great luck with batteries? Batteries are Interstate Marine Deep Cycles Thanks in advance. Quote
clipper Posted September 14, 2009 Posted September 14, 2009 I've had no experience with 36 volt systems but the first question the guys who reply to your post will ask is "how are you charging the batteries?" Are you carrying them in the house each time you go fishing? Quote
Super User Way2slow Posted September 14, 2009 Super User Posted September 14, 2009 What you are faced with one of the biggest pitfalls of series batteries, in a series configuration, all batteries have to be the same. This means they have to be the same Make, Size, and AGE. The only time you can replace just one battery in a series system is when all batteries are fairly new and have not been cycled over approx 25 times. After they have be cycled more than that, their charge and discharge capacity starts to change and this has to be fairly even among them. In series, all batteries see the same current load, if the batteries are not identical, one battery can see a much larger/smaller the current load than the others, this can either damage the one battery, or the other two. So, what this all boils down to, when you need to replace one battery, you have to replace all three. Now, the one battery should have lasted much longer than that unless you are fishing over 200 days a year. I know you get bad stuff all the time, but I would check my onboard charger and make sure it's functioning properly. Charging the batteries to a full charge and either coming back on when they drop to the preset voltage or maintaining the proper float voltage if it has a float mode. I am assuming you leave it on 24.7. Quote
HPBB Posted September 14, 2009 Posted September 14, 2009 I run a 36volt MG Tour and way2slow is right when you change one change them all. My boat is out 75+ a year and i get 3-4 years on a set of batteries (cheep batteries too). One question you say that the TM is feeding off of one? if that is the case then you only run 12 volt, even if all batteries are in series. the neg wire from your TM should be off of battery one and the pos should be off of battery 3. this is a bad diagram but here goes. if you run the pos and neg from any of the 3 batteries they will be at 12volt. you can run your livewell/ elctronic of of any 12 volt hook you. this is how my set up is. also make sure you charger is working. when my first set went bad it was beacuse of the charger and it cooked the bateries. TM 36 volt neg POS l l l l l l l l neg pos______neg pos_______neg pos battery one battery two battery three l l l l l l l l 12 volt running all electronics and live wells. Quote
Skeeter0007 Posted September 14, 2009 Author Posted September 14, 2009 This is the current set up. So replace all three at the same time. Also the bats are all the same make model. Jones trolling motors got back to me and told me to run 3 bats for the trolling 1 for engine and the rest of the electronics. So total 4 bats and use an MK-3-DC onboard alternator charger. to charge the trolling bats while I'm running hole to hole. I like this Idea I run a 36volt MG Tour and way2slow is right when you change one change them all. My boat is out 75+ a year and i get 3-4 years on a set of batteries (cheep batteries too). One question you say that the TM is feeding off of one? if that is the case then you only run 12 volt, even if all batteries are in series. the neg wire from your TM should be off of battery one and the pos should be off of battery 3. this is a bad diagram but here goes. if you run the pos and neg from any of the 3 batteries they will be at 12volt. you can run your livewell/ elctronic of of any 12 volt hook you. this is how my set up is. also make sure you charger is working. when my first set went bad it was beacuse of the charger and it cooked the bateries. TM 36 volt neg POS l l l l l l l l neg pos______neg pos_______neg pos battery one battery two battery three l l l l l l l l 12 volt running all electronics and live wells. Quote
Ann-Marie Posted September 16, 2009 Posted September 16, 2009 Even with matched batteries, discharging too much is suicide to a 36 volt battery. For the technical details if your interested, picture this circuit. You have 18 cells wired in series with the motor when it is running. Each cell can be regarded as a 2 volt source and some internal resistance that is normally very low. The motor in the circuit is a zero volt source and also some internal resistance normally higher. As the battery discharges the resistance in the cells increases so some of the voltage gets lost in these and your output voltage drops. The resistance of the motor does not increase. If you discharge too much and the resistance of the weakest cell gets to be too high, for example equal to the motor resistance, then it will have a voltage across the resistance equal to the voltage across the motor, say 16 volts. So if the voltage across the lowest cell resistance got to 16 volts that would put 14 volts REVERSED across the cell which will rapidly destroy it. This can happen in 12 volt batteries too but the reverse cell voltage is limited to about 8 volts and the damage occurs slower. So don't be tempted to squeeze that last run out of the batteries, that is what kills them. Quote
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