I use a trolling motor on my dinghy because it's fun. I typically use a small 7 amp gel cell because its very portable. It's enough for 1-3 days. I'd like to charge it off of my car. Would a solar charge controller work for this purpose? I'm not looking for anything fancy since these batteries only cost $10-15
I want to charge a 12v battery with a 12v battery so I can have 12v
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So you want to charge the 7 amp gel cell from some source. What charger originally came with your the 7 amp gel cel? Is it an AC charger that you plug into some sort of charger for the gel cell? Could you just use a small portable inverter plugged into the DC circuit that gives you enough AC to run the regular charger? Trying to understand what it is you are trying to do?
I want to use my car to charge my gel cell so it's ready to go the next day. I originally bought the gel cell for a UPS but havent gotten around to installing it. There was no charger included. Running an inverter to go from 12v to 120v to 12~16v seems like a very round about way of getting 12v not to mention it would probably kill my battery if left on overnight.
Even if the gel cell was totally dead, I doubt charging it back up would drain more than 15% of my car's battery. Not enough to put me in a bind in the morning.
So, with that said, I'm really just looking for a way to keep the gel cells from overcharging. I've seen those things go up in smoke a few times
Nothing like using a 120A alternator to charge a 7A battery! This is just an easy way to keep that dinghy batt charged
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You are going to charge it from your car? I"m assuming by the need to charge from the car that your car is not parked at home when you do this? More info on the whole picture would be helpful rather than trying to guess. If its parked at home, Why not just buy a small "1 to 1 1/2" amp maintenance charger from the auto parts store or another appropriate small charger?
I know its not the most efficient way, but why not a small portable inverter hooked to your car battery with clips (I used to have one). Then plug the 1 - 1 1/2 amp maintenance charger into the inverter and voala. The inverter with that load shouldn't drain your car battery overnight? Just still not understanding the application. A solar controller is not cheap. Look on ebay a device to accomplish what you are trying to do?
I know its not the most efficient way, but why not a small portable inverter hooked to your car battery with clips (I used to have one). Then plug the 1 - 1 1/2 amp maintenance charger into the inverter and voala. The inverter with that load shouldn't drain your car battery overnight? Just still not understanding the application. A solar controller is not cheap. Look on ebay a device to accomplish what you are trying to do?
As the batteries are so cheap I'd just hook it up in parallel, no charge controller or anything. Either alligator clips to the terminals or through the lighter plug.
May not get full charge if the car isn't running so the batteries won't last as many cycles, at $10 each they may last long enough.
May not get full charge if the car isn't running so the batteries won't last as many cycles, at $10 each they may last long enough.
If the batteries are that inexpensive, why not just have 2 or 3 and charge them at home during the week and bring them all down to boat on the weekend? Car batteries are designed to discharge a lot of energy quickly, they're not as good at long slow drains such as leaving a light on or charging batteries.
Dave's right. It would be helpful, also, for us to know how it is supposed to be charged. You said you didn't get a charger with it, but that doesn't answer the question. Is it a mini-plug, a small socket plug, wires that are exposed when you open the case? Help us to help you.
At the moment I've been pretty nomadic. I've only spent 2-3 hours at home this week. The only thing stopping me from directly wiring it up to my car's electrical system is the fact that it would be overcharged. Most days I don't discharge them less than 40%. If they don't get to 100% it's not a big deal. The marina isn't big and I'm perfectly capable of rowing. It's basically a toy to keep me happy while at the marina. I figured a cheap Chinese solar controller would be sufficient to charge these little batteries. Any suggestion on rating? 20 and 30A seem fairly common
Google says peak charge voltage for gel is 14.1-14.4, about what your car will be when running. With the car off voltage will be 13.0 or less. No need to over complicate things.
How often do you run your car? If you're looking to leave it off for a week and use it to charge the little batts you'll be asking for trouble. If you drive it every day or two you'll be fine.
I usually drive multiple times a day. Voltage was at 12.2 or 12.4 just after I shut the car off earlier today. I'm guessing with the engine on it'll be around 13.5v. Once the battery is charged the power draw should be minimal with a charge controller.
Does anyone have any recommendations for the rating of the charge controller?
Does anyone have any recommendations for the rating of the charge controller?
I'm recommending no charge controller.
You're car's 12v system has a built in charge controller in the alternator. You want to charge a small 12v battery. Hook it up in parallel (+ to +, - to -) and be done with it.
You're car's 12v system has a built in charge controller in the alternator. You want to charge a small 12v battery. Hook it up in parallel (+ to +, - to -) and be done with it.
My car has a much larger battery so running two batteries of different sizes, health, etc in parallel might not yield the best results
Last try here.
Different sized batteries don't do well in series. They can be fine in parallel if they have the same or compatible chemistry. We're not talking about leaving them connected all the time, just enough to charge the little battery. I'd use the lighter plug. Use a cheap digital voltmeter to check the process. Wire it in line with the charge wire for easy monitoring.
But if you want to buy a charge controller or inverter+110 charger suit yourself.
Different sized batteries don't do well in series. They can be fine in parallel if they have the same or compatible chemistry. We're not talking about leaving them connected all the time, just enough to charge the little battery. I'd use the lighter plug. Use a cheap digital voltmeter to check the process. Wire it in line with the charge wire for easy monitoring.
But if you want to buy a charge controller or inverter+110 charger suit yourself.
There are battery charges specifically designed for this application, for the radio control (R/C) market. They are actually quite sophisticated and versatile, and quite inexpensive, considering the features.
The idea is that people used motorcycle batteries in their "boxes' to run electric starters for gas or glow R/C engines, and needed to recharge them in the field. Simply connecting them to one's car battery, especially when the car isn't running, won't cut it. These chargers are DC boost converters and chargers.
Here's an example:
Turnigy Accucel-6 80W 10A Balancer/Charger LiHV Capable - about $34.
"The Turnigy Accucel 6 Balance Charger utilises quality FET's and resistors to accurately balance and charge LiPoly, LiFe, LiHV, NiMH, Nicd and Lead Acid batteries."
"And because this is a 12v DC charger you can power it up at the field using a 12v car battery or at home with a 12v power supply."
I have a couple of these in different sizes. They really work well.
The idea is that people used motorcycle batteries in their "boxes' to run electric starters for gas or glow R/C engines, and needed to recharge them in the field. Simply connecting them to one's car battery, especially when the car isn't running, won't cut it. These chargers are DC boost converters and chargers.
Here's an example:
Turnigy Accucel-6 80W 10A Balancer/Charger LiHV Capable - about $34.
"The Turnigy Accucel 6 Balance Charger utilises quality FET's and resistors to accurately balance and charge LiPoly, LiFe, LiHV, NiMH, Nicd and Lead Acid batteries."
"And because this is a 12v DC charger you can power it up at the field using a 12v car battery or at home with a 12v power supply."
I have a couple of these in different sizes. They really work well.
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Wow! That's an awesome little charger! Technology has changed so much since I was into RC cars. I ordered a solar charge controller last night so if that doesn't work I'll definitely give the RC charger a try
In order to charge one battery from another you need a charging voltage present in order to do so. If you don't have a charging voltage the batteries will attain parity voltage and minimal to no current will flow between batteries. Also GEL charges at a lower voltage than flooded or AGM lead acid batteries so you'd need a way to step down to a 14.1V - 14.2V GEL charge voltage.
A DC to DC charger would work, such as the Sterling Power ProBatt Ultra's but they cost more than the GEL battery you're using...
The charger I suggested in the post before yours is just such a charger: DC-DC, handles a large variety of battery types, charges automatically, cycles batteries, logs charging and discharging data, etc., etc., for about $34 for a 10A charger. They really are quite remarkable.
Update: the less expensive ones don't have data logging.
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