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Posts: 323
Location: Waukee, IA | I am installing a 24 volt system in my boat this winter and am wondering if I need to have the same type of batteries or if they can be different?
I currently have a trojan as my trolling motor battery but I need to buy another one for my new trolling motor. Trouble is....I am not sure that I can fit both batteries in my storage area in the front which is my only option. The trojan fits but there is no way I can get two of them in the same space.
Are there other lower profile batteries that I could use? I need something less tall to fit.
Also, how far between batteries can your jumper wires be???
Thanks for any help! |
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Posts: 433
Location: Cedarburg, Wisconsin | The smaller the wire you run the closer they must be. If you run 4 gage or 6 gage I'd think you'd be good for any run up to 20 feet. Probably you could get by with 8 gage or 10 gage if it is shorter and you don't need 50+ amps. With the 24V the amp draw should be less than with 12V.
If you use different batteries you must be careful charging as they will charge at different rates and times. I'd get rid of the battery you have and put in a matched set that fits to make it easier to charge, but that's just me. You could try mixing them but I have no idea what that may cause. I'm afraid it won't be good though. |
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| you really don't want to mix batteries for a variety of reasons. consider using the trojan for your other stuff and get two new ones, they really will last alot longer. |
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Posts: 2753
Location: Mauston, Wisconsin | Guest - 12/22/2008 3:51 PM
you really don't want to mix batteries for a variety of reasons. consider using the trojan for your other stuff and get two new ones, they really will last alot longer.
It's amazing that these lead-acid battery "urban legends" still exist. Just go buy another Trojan of the same size. Adding a new battery in series with an older battery to supply 24V to your new TM isn't going to affect the useful life of either battery. In fact they don't have to be the same size nor do they have to be the same manufacturer or even the same lead-acid type (wet-AGM-gell). No matter what, make sure you charge them separately, i.e., with stand-alone 12V charger or an onboard dual battery/split bank charger. Don't buy a 24V only charger.
For cable sizing follow your trolling motor manual installation recommendations. Beware of using to small of a cable (don't go small to save money). If your TM data plate instructions call for 50A wire - you need #8 AWG minimum. If you're running the cables 15-20' you might want to consider #6 AWG. F.ex With a 50A load the #8 AWG 20' circuit voltage drop will be ~ 1.6V - Thats ~81watts of power being lost in the cables. If you use #6AWG the voltage drop will be ~ 1.02V and power loss in the cables would be ~51W. If you want to squeeze maximum performance from your battery and the TM consider larger cables. In no circumstance should you use anything smaller than what the manufacturer recommends, including a inline fuse or circuit breaker to protect the cables and the TM.
#6 AWG = 65A max
#8 AWG = 50A max
#10 AWG = 35A max
#12 AWG = 25A max
The above are with a 75C (167F)cable temperature in a 30C (86F) ambient, this is the effect of watt loss/heat in the cables.
Good luck.
Al
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Location: Grand Rapids, MI | What if you have a 12V Trolling Motor? Can you still hook up 3 batteries together? |
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Posts: 5874
| Sure, in parallel. That would really up your run time, providing you have good batterys to start with. |
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Posts: 717
Location: Grand Rapids, MI | Thanks, Shep. I was hoping you'd say that. I'm sick of switching battery terminals halfway through the day! |
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Posts: 433
Location: Cedarburg, Wisconsin | The only problem with multiple batteries in parallel is that it takes longer to recharge them. Your charger has a finite charging current so the more power you use from the multiple batteries, the longer the time to replace it. This usually isn't a problem at home but at a remote vacation resort, using a 100 feet of extension cord or more, you may find yourself with less and less reserve each day even with the multiple batteries. I always ran two in parallel for my 12V system and had on the fly charging capabilities too. Still found a few days where the batteries were getting weak towards the end of the day. |
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Posts: 323
Location: Waukee, IA | Maniac,
So you are saying I would be just fine if I didn't have another Trojan battery? I can't have two of them because they both won't fit in my storage area...too tall for it. BUT.....I tried an interstate battery from my Travel trailer and hooked everything up today and the trolling motor ran...so that is good FOR ME 
So it sounds like I can just get another TM battery that will fit and as long as I charge them separately...which I was plannning on doing anyway...I should be fine? |
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Posts: 2753
Location: Mauston, Wisconsin | wkeegobbler - 12/23/2008 8:56 PM
Maniac,
So you are saying I would be just fine if I didn't have another Trojan battery? I can't have two of them because they both won't fit in my storage area...too tall for it. BUT.....I tried an interstate battery from my Travel trailer and hooked everything up today and the trolling motor ran...so that is good FOR ME
So it sounds like I can just get another TM battery that will fit and as long as I charge them separately...which I was plannning on doing anyway...I should be fine?
Yes - You will be fine. Another "EM" trick for a tight space is to use a valve-regulated lead-acid battery (VRLA), more commonly known as absorbent glass mat (AGM) or gell cell or no-maintenance, and to install them on their side. They can actually be operated in any posistion except upside down, i.e., there is no free electrolyte to spill. But I would also put a 1/2 " rubber shock/vibration pad under the battery to lessen the shock/vibration.
With respect to multiple battery's and paralleling them. If you have multiple batteries for your 12V trolling motor, the best method of use is to parallel them. This will give you maximum runtime. I said this before in another battery question thread.
f.ex. If you have two (2) batteries that are marine rated @180 minutes. That rating means those batteries can discharge 25A for ~180 minutes before they are considered as discharged and require recharging.
Now if you use them individually by swapping them you will get a total of ~ 360 minutes. However, if you parallel them you will get ~ 1080 minutes. I know it sounds crazy, but it's absolutely true. It's a phenomena of the electro-chemistry of a lead-acid battery. Many folks think of a battery as synonymous to a gas tank i.e., where you have fixed quanity of fuel. Well that's really not true.
With a lead-acid battery the amount of energy/power available for use is dependent upon the rate of use. The lower the rate, the more energy that is available. The available fuel qty changes with rate of use even though the battery doesn't change it's physical size.
The rule of thumb for any lead-acid battery: If you double the load-the runtime will be 1/3 of the original. Conversely if you cut the load in half the runtime will triple.
If we are discharging the battery at 25A we get 180 minutes. However, when in parallel with another battery of the same AH rating. The load on each is cut to 1/2 or 12.5A. Shazam! So with two batteries in parallel you get 3 x the original runtime 3 x 180 x 2 = 1080 minutes.
Recharging - the right size charger is important in recharging your battery. It takes longer to recharge a battery that has been discharged at a low rate versus one that has been discharged at a high rate. If we roughly calulate the watt seconds of energy removed for each of the examples above, we can see that we have removed more energy from the battery with the lower discharge rate.
25A x 12V = 300W 300W x 180 minutes x 60 sec = 3, 240,000 watt/sec
12.5A x 12V = 150W 150W x 540 minutes x 60 sec = 4,860,000 watt/sec
This means recharge time required is also variable based on how you discharged the battery. How big of a charger do you need - generally the charger should have an ampere rating (A) that is from 5% to 20% of the battery ampere/hour rating. F.ex. a 100AH battery would require a 5A to 20A charger for proper recharge. Don't go smaller or don't go larger. Either would likely damage the battery. 100AH and 80AH are very common battery raings for trolling motor's. I have two (2) 100AH batteries and I use two (2) 15A stand-alone battery chargers to recharge. them.
As Shep said, paralleling 3 batteries will really boost the runtime. But also it was pointed out that you need to increase the charging power. You can use a single charger or you can use three separate chargers or a three bank charger to recharge them, i.e., each battery needs to get recharged within a reasonable period of time, typically 8-24 hrs. My batteries are usually fully recharged after ~12 hrs.
Merry Chrismas!
Al
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Posts: 135
| Hey Al,
Merry Christmas and thanks large for the battery class, it's slowly sinking in to my brain which resists charging normally.
So I am going to parallel my new Optima and my older big ol' Trojan battery and charge them separately, so I assume that I'd better unhook the batteries from one another before I hook up separate chargers, right?
W |
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| 80 lb. Terrova. Quality baby! |
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Posts: 2753
Location: Mauston, Wisconsin | whit65 - 12/24/2008 10:02 AM
Hey Al,
Merry Christmas and thanks large for the battery class, it's slowly sinking in to my brain which resists charging normally.
So I am going to parallel my new Optima and my older big ol' Trojan battery and charge them separately, so I assume that I'd better unhook the batteries from one another before I hook up separate chargers, right?
W
When paralleling battery's, if the battery is the same type but different size it's Ok to use a single charger- but you need to consider the combined AH rating when selecting the charger size. F. ex. If paralleling a 100AH with an 80AH the combined AH rating is 180AH. Ideally you would want a 18A-36A charger. I would never go lower than 10% of the AH rating. Some onboard dual or triple bank chargers permit paralleling of the output to achieve higher output ratings, i.e. a triple bank 10A charger may allow the three (3) 10A outputs to be paralleled for 30A total. Check with the manufacturer before purchase.
If the batteries are different type - AGM & wet cell you don't need to charge them separately all the time. But the wet-cell may need a periodic equalize charge. Get a marine dual battery paralleling switch - A-B-Both-Off. Set it to "Off" and turn on your charger(s). That way you don't have to disconnect any cabling. You can also do the same thing with a couple of marine grade 50A 12VDC single pole switches.
Here's some charging configurations for those interested.
Happy New Year!
Al
(12-24V Trolling Motor Battery Charging.gif)
(24V Trolling Motor Battery Charging.gif)
(36V Trolling Motor Battery Charging.gif)
(12V Trolling Motor Battery Charging.gif)
(12V Trolling Motor Battery Charging w-AB SW.gif)
Attachments
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 12-24V Trolling Motor Battery Charging.gif (6KB - 1223 downloads)
24V Trolling Motor Battery Charging.gif (5KB - 1612 downloads)
36V Trolling Motor Battery Charging.gif (7KB - 716 downloads)
12V Trolling Motor Battery Charging.gif (4KB - 221 downloads)
12V Trolling Motor Battery Charging w-AB SW.gif (6KB - 680 downloads)
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Posts: 135
| Thanks, Al great information,
Man, I love this board!
W |
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Posts: 2753
Location: Mauston, Wisconsin | Almost-B-Good - 12/23/2008 10:08 AM
The only problem with multiple batteries in parallel is that it takes longer to recharge them. Your charger has a finite charging current so the more power you use from the multiple batteries, the longer the time to replace it. This usually isn't a problem at home but at a remote vacation resort, using a 100 feet of extension cord or more, you may find yourself with less and less reserve each day even with the multiple batteries. I always ran two in parallel for my 12V system and had on the fly charging capabilities too. Still found a few days where the batteries were getting weak towards the end of the day.
Excellent!
Happy New Year!
Al |
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Posts: 97
Location: Chaska MN. | Thanks Al for the diagrams, correct me if Im wrong but with a 24V system I can charge with two 10 amp chargers one on each and should not be a problem, any advice on charging 24V system without a on board system would be great as my funds right now wont allow for that. |
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Posts: 2753
Location: Mauston, Wisconsin | suicknut- Yes you can, see the 24V charging diagram above. You can also charge them individually with a single 12V charger by switching the battery charger from one battery to the other - it just takes ~ twice as long to recharge them.
I personnaly use two (2) stand-alone Vector chargers. (2A-10A-15A selectable) -> the top one.
http://www.battery-rechargeable-charger.com/auto-vector-car-battery...
I didn't pay this price, I got them on sale at Farm & Fleet ~ 3 years ago and paid less than $100 for both....
I know there are guy's here who swear by onboard chargers - thats their perrogative. If you have lots of cash, they are OK, but I think external charger(s) are a better and more cost effective solution.
1. I can recharge any lead-acid battery - my car's - truck-boat's-motorcycle-garden tractor - portable depth finder - Xavier's electric gocart, etc.
2. I always have a spare charger! Very important if you're on a remote fishing trip and Wally World is 100 miles away.
3. Having two allows me to recharge my trolling motor batteries twice as fast (12/24V TM).
4. Yes - somone's going to say it's a pain in the butt having to get chargers from where they are stowed - I use a waterroof plastic tote, that I just leave on the dock or inside my truck cab, then you have to open the hatch. remove the battery covers - hook them up - plug them in- after charging unplug them - unhook them - replace battery covers - close hatch, stow chargers, etc
With a onboard charger you just plug it in and unplug it! But you also don't get to see/your battery(s). I get to inspect my batteries and terminals everytime I recharge them. What about loose/corroded connections, or little furry critters using your battery box as a home & chewing on cables out of boredom? The whole process takes me 5 minutes, and when I close that hatch, I know Esox Maniac is ready!
Some last words on battery safety. Be careful, especially with batteries that are recharging or have just been recharged. Every lead-acid battery evolves hydrogen & oxygen during the recharge process. A 5% hydrogen level in air is considered as explosive.This means no sparks or open flames around batteries, don't lean over a battery with a cigarette in your mouth or hands. Don't check the electrolyte level by using a cigarette lighter as a light source. Use insulated tools/wrench's (electrical tape is your friend)
A short story: Back in my military days while stationed in Germany (I was in electronics) the Divison Command Sargent Major (CSM)came over to the electronics section and asked me to help fix a problem with one of the tanks, i.e., the driver's intercom was not working, w/o intercom the tank commander can't communicate to the driver, etc. I go over to the maintenance section. The tank is sitting in the maintenance bay - main gun is facing rear. Driver's hatch is closed so I go in through the turret hatch, crawl into drivers compartment and start working on the com problem. ~ 5 minutes later one of the mechanic's climbs into the turret and says he has to do the scheduled battery maintenance. The batteries in this tank are under the turret floor - two big 24V batteries. To access them there is hinged access panel in the turret floor. The same access panel allows access to the bottom escape hatch if the gun is in the rear position. So mechanic says hey Sarge I gotta move the turret so I can service the batteries, I say go ahead. I had already opened the driver's hatch for ventilation- tanks can be pretty smelly places! I'm working, ~ 60 seconds later there is a huge explosion inside the turret. Fortunately when he traversed the turret it automatically placed a solid steel shield between me and the turret (when the turret is traversed from the travel posistion the only way out for the driver is the drivers hatch). Have you ever heard hand grenade go off? Welll imagine one ~ 5ft away inside a solid steel sphere. I am up & out of the drivers hatch in less than 5 sec. I climb up onto the turret & look down in - see the mechanic through the smoke- he's got his hands on his ears screaming - I grab both wrists and physically lift him up through the hatch - By this time guys are coming from all over with fire extinguishers etc. I drag him down onto the engine compartment and a couple of guys take over. I look down off the tank & the CSM is standing there looking at me and his mouth is moving but I cant hear him, because my ears are ringing. I tell him I can't hear him, but I'm OK. There is a 2 lb chunk of battery lead & plastic laying at the CSM's feet. The CSM was coming over to see how I was doing with the intercom problem, i.e., without driver intercom- the tank is a +50 ton piece of worthless steel. His job is to make sure the equipment and his men are all at 100% capability. It took a few minutes for my hearing to come back. The chunk of battery had been ejected through the turret hatch- hit the maintenance bay roof and landed at his feet.
The mechanic had ruptured ear drums & minor scrapes and some minor acid burns on his hands. His hands and glasses helped protect his face. What happened - he was removing the positive battery cable to clean it with an un-insulated wrench, and he shorted the battery terminal to the turret floor. The resulting spark ignited the hydrogen in the battery - unknown to me he had the tank running for ~30 minutes before I got there, to make sure the batteries were fully charged so he could check the electrolyte specific gravity (required check in the maintenance log.).
Batteries also have an lot of stored energy and can release all that energy in a very short time- what we engineers call available short circuit current (SCC)- A typical 100AH marine deep cycle no-maintenance battery can deliver ~3000A of SCC. It's fairly easy to weld steel with a battery. IT's also easy to vaporize wrenchs/pliers etc. That vapor/metal in plasma form can also do a lot of damage to your hands, eyes, face etc. Insulate any tools - for example if you have a box end /open end combination wrench, decide which end you want to use & tape up the entire rest of the wrench.
Have you ever seen someone hook up a set of jumper cables to a car/truck battery and take the loose ends and tap the clamps together to check the connection by getting a good spark? Guess what? You have just witnessed an prime example of clueless human behavior. He should not be allowed to procreate, i.e., the human gene pool doesn't need more stupidity. Think about it, what are those sparks? Are they electrons? Noooooooooo! They are piece's of molten metal - do you value your vision? Don't do this with jumper cables or any cables connected to a power source such as a battery.
Have fun!
Al |
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