Battery for my trolling motor...twin or single?

[jwardmagic]

I have a 55lb thrust troling motor that I am looking to buy a 12v deep cycle battery for. I found that I could buy two 85ah batteries for ?60 each, or a 135ah battery for ?150. To me, buying two 85ah batteries and connecting them in parallel seems better as I'd be basicaly then using 170ah for a lot cheaper than buying a single battery.

The two cheaper 85ah batteries are shown on the following links:
http://www.tayna.co.uk/Numax-CXV24MF-P3126.html

And the single more expensive 135ah battery:
http://www.tayna.co.uk/M135-Premium-Numax-Deep-Cycle-Marine-Battery-P3774.html

The 85ah batteries say they are sealed (suitable for marine) and deep cycle.

My question is, would my assumption that two 85ah batteries be better than the single one correct? They would also weigh less.
What are the pro's and cons?

If anyone can help I'll be very grateful!

Thanks

 

[mudslinging79]

Re: Battery for my trolling motor...twin or single?

con would be the weight. pro is hook them up right you double the amps, yet keep 12 volts

 

[5150abf]

Re: Battery for my trolling motor...twin or single?

Second mudslinging, 2 will weigh more than one, if your boat will take the weight without upsetting your balance I would do it.

I have 3 batteries on mine, starter and 2 boat, I always fish down river and hate running out of power, had to troll back a couple weeks ago and barley made it, got the second battery before the next trip, no worries now.

 

[jwardmagic]

Re: Battery for my trolling motor...twin or single?

Thankyou for the replies. The I found out that each 85ah battery weighs 18kg and the single 135 weighs 40kg...so using two singles wouldnt weigh more but less!

 

[fishrdan]

Re: Battery for my trolling motor...twin or single?

each 85ah battery weighs 18kg and the single 135 weighs 40kg...so using two singles wouldnt weigh more but less!

I find it hard to believe that 2 lighter batteries would provide more power than a single heavier battery, since the majority of the batteries weight comes from the lead plates, bigger plates, more power. If they do it's great, but it goes against everything I've ever heard about batteries of similar construction.

If you run dual batteries, run them separate instead of running them in parallel, use a battery switch or connect to them manually 1 at a time. Connecting them in parallel will double your AH, but as the batteries get old 1 of them will get weaker. When this happens the weak battery will drain the good battery down to it's voltage and slightly discharge the better battery. I used to connect my 12V batteries in parallel and when I separated them and ran them independent, the total run time was longer,,, than having the batteries connected in parallel. With new batteries I'm not sure you would see much of a difference, but as they get older I think you will see a difference, probably in a year or 2, depends on usage and how well the batteries are maintained.

How long do you want the battery(s) to last with the trolling motor? I'm running 2 brand new group 29 batteries (210 reserve capacity, about 65# each) with a 45# trolling motor and each one will last about 5-6 hours of constant usage before it's discharged, this is trolling at speed 2 with short bursts of speed 4-5. The old batteries (from 2006 and 2007) would only go 2-4 hours before they needed to be recharged, they needed to be replaced...

Personally I would get the biggest battery available and see if it suits your needs, since you might have to add a second for more run time

I looked at the batteries you linked and the shipping price is driving up the price of the bigger battery, can you get these batteries locally? The 2- group 29 batteries I just bought locally cost $170 in the US, but if I had to have them shipped, I'm sure it would have tacked on another $100. Warranty coverage for a battery is an important thing to consider and if you have to ship it off it for replacement it could be expensive.

Oh yeah, if this is a lead/acid battery (not AGM or gel-cell) I would try to find one with removable caps instead of sealed. As the battery gets old the fluid level can drop, if the plates get exposed it will be a short end to the battery. I usually check my deep cycle batteries twice a year and they always need a bit of water added, though I do use them hard.

 

[steelespike]

Re: Battery for my trolling motor...twin or single?

I agree^ Battery capacity can be traced directly to weight,And as stated
in parralell can become un balanced.You should also consider the AGM batteries.
In my electric car occasionly when running low on a steep hill the system would drop out.But batteries have what I call "bounce back" where they will regain enough to run the car further.I find the AGMs bounce back quicker and with more reserve.An electric car draws a temendous amount af amperage especially on a hill.Your trolling motor would never challenge them.I feel that my 105 amphour AGMs performed close to the original 135 amp hour flooded batteries that came with the car,and were comepletly maintenace free under very strenous conditions.

 

[jwardmagic]

Re: Battery for my trolling motor...twin or single?

I find it hard to believe that 2 lighter batteries would provide more power than a single heavier battery, since the majority of the batteries weight comes from the lead plates, bigger plates, more power. If they do it's great, but it goes against everything I've ever heard about batteries of similar construction.

If you run dual batteries, run them separate instead of running them in parallel, use a battery switch or connect to them manually 1 at a time. Connecting them in parallel will double your AH, but as the batteries get old 1 of them will get weaker. When this happens the weak battery will drain the good battery down to it's voltage and slightly discharge the better battery. I used to connect my 12V batteries in parallel and when I separated them and ran them independent, the total run time was longer,,, than having the batteries connected in parallel. With new batteries I'm not sure you would see much of a difference, but as they get older I think you will see a difference, probably in a year or 2, depends on usage and how well the batteries are maintained.

How long do you want the battery(s) to last with the trolling motor? I'm running 2 brand new group 29 batteries (210 reserve capacity, about 65# each) with a 45# trolling motor and each one will last about 5-6 hours of constant usage before it's discharged, this is trolling at speed 2 with short bursts of speed 4-5. The old batteries (from 2006 and 2007) would only go 2-4 hours before they needed to be recharged, they needed to be replaced...

Personally I would get the biggest battery available and see if it suits your needs, since you might have to add a second for more run time

I looked at the batteries you linked and the shipping price is driving up the price of the bigger battery, can you get these batteries locally? The 2- group 29 batteries I just bought locally cost $170 in the US, but if I had to have them shipped, I'm sure it would have tacked on another $100. Warranty coverage for a battery is an important thing to consider and if you have to ship it off it for replacement it could be expensive.

Oh yeah, if this is a lead/acid battery (not AGM or gel-cell) I would try to find one with removable caps instead of sealed. As the battery gets old the fluid level can drop, if the plates get exposed it will be a short end to the battery. I usually check my deep cycle batteries twice a year and they always need a bit of water added, though I do use them hard.

The quotes I got about the weights of the batteries were directly from Tanya the company. Ideally I'd like to the battery/ies to run for 2 hours, if I had the motor on full throttle. Its a 55lb thrust motor. I live in the south of the UK and the company is in Wales so I can't really get them locally. What Ah/type of battery would you recommend? I dont really want to be forking out too much for a battery.

 

[fishrdan]

Re: Battery for my trolling motor...twin or single?

Ideally I'd like to the battery/ies to run for 2 hours, if I had the motor on full throttle. Its a 55lb thrust motor.

Either of those battery(s) you listed (2 small or 1 big) would run the trolling motor at full power for 2 hours, and maybe a bit more, but I would expect much more. Generally, trolling motors draw the same amount of current as their thrust rating, 55# = 55amps, it's not really accurate, but a good rule of thumb. Theoretically, one small 85AH battery should run the TM at full power for about 1.5 hours and the 135AH battery about 2.25 hours, but that's just a guess. I did a KG/LB conversion on the 135AH battery and 40KG is 88lb, that's a big battery. My group 29 batteries only weigh about 65# each.

Are you in a small town? Around here the local auto parts stores carry (or can get) marine batteries, though you do pay a premium for them. Even the "big box" stores around here carry marine batteries, Kmart, WalMart, though I'm not sure if you have any places like that around you.

Something to remember about batteries, they are like milk, you don't want to buy one that has been sitting on the shelf for a long time. I try to find one that's 1-2 months old, 6 months is a gray area, I wouldn't by one that is a year old. The month/year is usually stamped or stickered on the case of the battery, well at least over here it's like that.

 

[jwardmagic]

Re: Battery for my trolling motor...twin or single?

Thankyou for your reply. There is one big battery store about 50 miles from me I may try, but they dont sell the M135 battery, which is strange. Im sure they will all be over ?150.
You say both batteries will run the motor for 2 hrs on max...however, I don't want to fully discharge the batteries as that will ruin them. Would either type run the motor on full for 2 hours without fully discharging? I'd like to leave about 1/4 - 1/3 of the power in it so not to ruin it.

 

[Silvertip]

Re: Battery for my trolling motor...twin or single?

Batteries are buckets of electricity. The bigger the battery capacity the longer it will run the motor. So the bigger the number the longer the run-time. The next consideration is then weight, size, and cost. The rule of thumb for trolling motor batteries is the largest battery you have room for and can afford.

 

[fishrdan]

Re: Battery for my trolling motor...twin or single?

I'm with ST, the biggest you can afford, price and weight. I don't think you will harm either of those battery combo's, 2 small or 1 big by running the TM at full for 2 hours as deep cycle batteries are designed to be discharged and then recover. The battery should be able to deliver it's full rating without harm, which isn't beyond what you want to do.

You will cause damage to the battery if it's not charged up quickly after discharging it, like with in a day or 2, maybe a week. Leave the battery in a discharged state for a long time (month, year) and it will eventually kill the battery. The kiss of death for deep cycle batteries is leaving them discharged. I know people who pretty much have to buy new batteries every year or 2, they use/charge them for a couple months, then neglect them for 8-9 months during the winter. If you want the battery(s) to last a long time, get a nice electronic battery charger (10 amp or more) and charge the battery after each use. You can "top it off" again right before your next outing, but don't plan on "charging it up" right before the trip. I'm guilty of neglecting my batteries at times and paid the price, $170 to be exact...

 

[jwardmagic]

Re: Battery for my trolling motor...twin or single?

Is it not true however that the weight difference could be merely due to the fact that the battery "life levels" are different, not the ah? The 86ah maybe is made with less cycles than the 135ah?